12A half bridge
12-07-15, 05:18 PM
#1
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12A half bridge
Anyone running a 12A half bridge? What carb system are you using? Is there a way to install fuel injection in one of these engines?
Thanks
Thanks
12-07-15, 05:49 PM
#2
No way. I was just thinking about building another half BP 12A.
My setup will consist of:
RX-2 separate runner intake manifold
Racing Nikki (because it's huge!)
already hogged Y plates with 74 spec ports weakly attempted by the previous owner (will get corrected and get a set of eyebrows cut in the secondaries)
rotor housings with a little edge wear
Atkins apex seals to deal with the edge wear
static balanced 83-85 rotating assembly with stock flywheel (to smooth out the rough edges)
multi-hole stat gear bearings already installed and broken in
The eyebrows will get cut according to my previous findings. I'll need to go research what I did before.
The exhaust ports will be hogged out to similar timings as before, but this time a little bigger. Maybe out to 12AT spec or something.
Semi-locked if that's what it wants. Otherwise it'll get a stock or nearly stock dizzy. I've got four different stock timing curves to play with ranging from N201, N249, N304 and the rare N305 or N306 (hard to read through the grime).
The exhaust system I'll test it on will just be an RB long primary, which according to peejay, is not restrictive enough to worry about on his BP 13B, so I won't need to worry about it on a 12A.
Air filter will probably be an RB spun aluminum or a stock blue canister. j9fd3s says the stockers aren't all that restrictive. But at this point who knows what it will want. I haven't had a chance to build it and test it yet. I'm just in the planning stages at the moment.
Does any of this answer any questions?
My setup will consist of:
RX-2 separate runner intake manifold
Racing Nikki (because it's huge!)
already hogged Y plates with 74 spec ports weakly attempted by the previous owner (will get corrected and get a set of eyebrows cut in the secondaries)
rotor housings with a little edge wear
Atkins apex seals to deal with the edge wear
static balanced 83-85 rotating assembly with stock flywheel (to smooth out the rough edges)
multi-hole stat gear bearings already installed and broken in
The eyebrows will get cut according to my previous findings. I'll need to go research what I did before.
The exhaust ports will be hogged out to similar timings as before, but this time a little bigger. Maybe out to 12AT spec or something.
Semi-locked if that's what it wants. Otherwise it'll get a stock or nearly stock dizzy. I've got four different stock timing curves to play with ranging from N201, N249, N304 and the rare N305 or N306 (hard to read through the grime).
The exhaust system I'll test it on will just be an RB long primary, which according to peejay, is not restrictive enough to worry about on his BP 13B, so I won't need to worry about it on a 12A.
Air filter will probably be an RB spun aluminum or a stock blue canister. j9fd3s says the stockers aren't all that restrictive. But at this point who knows what it will want. I haven't had a chance to build it and test it yet. I'm just in the planning stages at the moment.
Does any of this answer any questions?
12-07-15, 07:15 PM
#4
Old [Sch|F]ool
FI would be super easy if you can source a GSL-SE intermediate housing and fuel rail.
My engine is basically a 12A with 13B rotating assembly and rotor housings... that's all a 4 port 13B is after all
And the GSL-SE intermediate housing. Using a carb as a throttle body. Works just fiiiiine.
I wouldn't screw around with a half bridge though. Full bridge has the same drivability but more power everywhere, at least if you have EFI.
My engine is basically a 12A with 13B rotating assembly and rotor housings... that's all a 4 port 13B is after all
And the GSL-SE intermediate housing. Using a carb as a throttle body. Works just fiiiiine.I wouldn't screw around with a half bridge though. Full bridge has the same drivability but more power everywhere, at least if you have EFI.
12-07-15, 09:17 PM
#5
Yeah with a carb, you have to do things differently.
Hey peejay, j9fd3s reminded me that if you can crack the secondaries open a little, it helps smooth things out. Fortunately the early Nikkis, like the 79s if not all of them, have a set screw under some white RTV you can adjust. However because my test vehicle has a leaky brake booster, I'll just let that be my air leak. And because the previous owner of the RX-2 mani knife-edged it up under where the secondaries are, creating kind of a smooth channel connecting both secondaries together, I'm curious how much will get to the front rotor through the channel. We know the rear will get plenty of air.
I wasn't going to create a build thread until more work has been done. Otherwise everyone gets annoyed at how long these things take. However, here you go. https://www.rx7club.com/1st-generati.../#post12000478
I'll update it when I've made progress.
Hey peejay, j9fd3s reminded me that if you can crack the secondaries open a little, it helps smooth things out. Fortunately the early Nikkis, like the 79s if not all of them, have a set screw under some white RTV you can adjust. However because my test vehicle has a leaky brake booster, I'll just let that be my air leak.
And because the previous owner of the RX-2 mani knife-edged it up under where the secondaries are, creating kind of a smooth channel connecting both secondaries together, I'm curious how much will get to the front rotor through the channel. We know the rear will get plenty of air.I wasn't going to create a build thread until more work has been done. Otherwise everyone gets annoyed at how long these things take. However, here you go. https://www.rx7club.com/1st-generati.../#post12000478
I'll update it when I've made progress.
12-08-15, 03:17 AM
#6
Old [Sch|F]ool
I'd want to see the opposite, no channels whatsoever. I'm trying to think of the most succinct way of putting this... Part of making good drivability with high overlap engines is minimizing the intake volume between the throttle plate and the intake port so vacuum in the manifold goes away as fast as possible during the overlap period. That way less exhaust gets pulled up into the intake manifold.
Worst case is if you have a plenum, but a channel between the two rotors will do the same thing, during the overlap period when the exhaust can get pulled up into the intake manifold, the port will be exposed to the vacuum draw from the OTHER rotor at nearly its highest rate of chamber expansion during the intake stroke.
That is why, when using the EFI "ping pong" manifolds, I would make sure they idled on the secondaries. And I didn't go full bridge until I had an ITB setup.
Worst case is if you have a plenum, but a channel between the two rotors will do the same thing, during the overlap period when the exhaust can get pulled up into the intake manifold, the port will be exposed to the vacuum draw from the OTHER rotor at nearly its highest rate of chamber expansion during the intake stroke.
That is why, when using the EFI "ping pong" manifolds, I would make sure they idled on the secondaries. And I didn't go full bridge until I had an ITB setup.
12-08-15, 09:44 AM
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Why couldn't one use a racing beat type intake with one of these:
MSD Atomic EFI Throttle Body Systems 2900 - Free Shipping on Orders Over $99 at Summit Racing
or any of the available TBI complete systems designed to bolt up to a Holley-type base?
Thanks
MSD Atomic EFI Throttle Body Systems 2900 - Free Shipping on Orders Over $99 at Summit Racing
or any of the available TBI complete systems designed to bolt up to a Holley-type base?
Thanks
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12-08-15, 10:19 AM
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Why couldn't one use a racing beat type intake with one of these:
MSD Atomic EFI Throttle Body Systems 2900 - Free Shipping on Orders Over $99 at Summit Racing
or any of the available TBI complete systems designed to bolt up to a Holley-type base?
Thanks
MSD Atomic EFI Throttle Body Systems 2900 - Free Shipping on Orders Over $99 at Summit Racing
or any of the available TBI complete systems designed to bolt up to a Holley-type base?
Thanks
that holley kit is huge money, and its about twice as big as you need, and thus i'd worry about its tunability, as you aren't putting it on a v8
12-08-15, 10:44 AM
#9
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I am running a Holley setup on my 12a half bridge. It runs good, but i don't like that i have a open spacer on it, I'm going to be installing a turbo and boost prepped Nikki
12-08-15, 11:12 AM
#10
You may be right, peejay. The insides of the secondary runners of this RX-2 manifold are black with carbon while the primaries are very clean aluminum.
It sounds like what you're saying is this RX-2 manifold, I had my heart set on, just won't work all that well on a half BP. That sucks.
But wait! I have two other manifolds as possible candidates! An RX-3 manifold that doesn't have any channels at all! And a 79 that has mammoth channels. I'd think the heavily channeled 79 would do better on a big streetport or a full bridge. But according to you, I want to minimize the plenum area on a bridgie, whether half BP or full, so any channels a mani may have are out. Thus I'm left with just the non channeled (sep runner) RX-3 manifold. I can save the 79 for a streetport.
But I'm still confused about something. I thought there would be a little bit of "ping pong" effect on the RX-2 manifold, you know? Due to its knife edged channel. That's why I wanted to use it. I thought this would be a good thing to take advantage of.
Actually, I have four manifolds to choose from, each with different features:
1) RX-2 manifold that was not channeled originally but the PO hogged out all the runners* but especially the secondary runners into kind of a knife edge that acts like a channel.
2) RX-3 manifold that was not channeled originally but the PO hogged out all the runners* but at least they're still separate.
3) 79 manifold that was channeled originally but has major hogging up under the phenolic spacer to produce two very large plenums and the runners were all hogged out.*
4) stock 81-85 manifold which we know flow like crap.
*This will kill low end torque as he port matched the primaries to the intermediate plate! All three manis are like this! GURRRRR!
Any ideas?
It sounds like what you're saying is this RX-2 manifold, I had my heart set on, just won't work all that well on a half BP. That sucks.
But wait! I have two other manifolds as possible candidates! An RX-3 manifold that doesn't have any channels at all! And a 79 that has mammoth channels. I'd think the heavily channeled 79 would do better on a big streetport or a full bridge. But according to you, I want to minimize the plenum area on a bridgie, whether half BP or full, so any channels a mani may have are out. Thus I'm left with just the non channeled (sep runner) RX-3 manifold. I can save the 79 for a streetport.
But I'm still confused about something. I thought there would be a little bit of "ping pong" effect on the RX-2 manifold, you know? Due to its knife edged channel. That's why I wanted to use it. I thought this would be a good thing to take advantage of.
Actually, I have four manifolds to choose from, each with different features:
1) RX-2 manifold that was not channeled originally but the PO hogged out all the runners* but especially the secondary runners into kind of a knife edge that acts like a channel.
2) RX-3 manifold that was not channeled originally but the PO hogged out all the runners* but at least they're still separate.
3) 79 manifold that was channeled originally but has major hogging up under the phenolic spacer to produce two very large plenums and the runners were all hogged out.*
4) stock 81-85 manifold which we know flow like crap.
*This will kill low end torque as he port matched the primaries to the intermediate plate! All three manis are like this! GURRRRR!
Any ideas?
12-08-15, 12:29 PM
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with a big overlap engine it is best to have individual runners, the rotors don't like sharing.
12-08-15, 02:12 PM
#12
I was not aware of this. I thought the channeled secondaries would be beneficial. Guess I was wrong.
I had success before because the manifold was totally stock. It seems I had beginner's luck.
I can still have some success with a half BP if I use the RX-3 manifold which happens to be an early one right before they started cutting channels. However the PO hogged the runners way out to match the tall intermediate plate, which as we all know, especially peejay, this removes the anti-reversion lip and leads to less power at low RPM. So I figured since it's a half BP and won't have that much at low RPM anyway, that it's fine. But then peejay and j9fd3s are saying these high overlap engines have more low end torque than the streetports have at high RPM. So once again I'm left scratching my head wondering what I should do.
Low end torque isn't really at low RPM. It's more accurately described as more power under the curve than a streetport has over the curve. Do I have that right? So it might have to idle at 1500 or 2000, but it will kick you in the pants a lot lower in RPM than a typical streetport would at higher RPM. Right?
I had success before because the manifold was totally stock. It seems I had beginner's luck.
I can still have some success with a half BP if I use the RX-3 manifold which happens to be an early one right before they started cutting channels. However the PO hogged the runners way out to match the tall intermediate plate, which as we all know, especially peejay, this removes the anti-reversion lip and leads to less power at low RPM. So I figured since it's a half BP and won't have that much at low RPM anyway, that it's fine. But then peejay and j9fd3s are saying these high overlap engines have more low end torque than the streetports have at high RPM. So once again I'm left scratching my head wondering what I should do.
Low end torque isn't really at low RPM. It's more accurately described as more power under the curve than a streetport has over the curve. Do I have that right? So it might have to idle at 1500 or 2000, but it will kick you in the pants a lot lower in RPM than a typical streetport would at higher RPM. Right?
Last edited by Jeff20B; 12-08-15 at 02:16 PM.
12-08-15, 04:37 PM
#13
Old [Sch|F]ool
Here's my current MSQ. I seem to recall from the mazspeed days that you've played a little with Megasquirt.
Mind you that it's a bit on the lean side below 4000rpm on purpose, it's happy at WOT and 13.5-14:1. At high RPM it's running quite a bit richer for cooling.
Also note the wildly asymmetrical RPM bins. Mostly I was adding them at random because the engine was perfectly happy with an 8x8. Probably could work equally well with a 3x3.
Every street port I've ever had would have a lightswitch effect at 5500rpm. The tunes would reflect that. When I did my first halfbridge, it made the same peak power as when it was a streetport but did it 1000+ RPM lower. This engine makes more low end and midrange power and it will carry past 10k depending on testicular fortitude or otherwise how stupid I'm feeling that day...
The thing is, unlike a street port, there IS no "kick in the pants". It just goes and there isn't really a powerband. It's soft below 2000rpm, that's it.
Mind you that it's a bit on the lean side below 4000rpm on purpose, it's happy at WOT and 13.5-14:1. At high RPM it's running quite a bit richer for cooling.
Also note the wildly asymmetrical RPM bins. Mostly I was adding them at random because the engine was perfectly happy with an 8x8. Probably could work equally well with a 3x3.
Every street port I've ever had would have a lightswitch effect at 5500rpm. The tunes would reflect that. When I did my first halfbridge, it made the same peak power as when it was a streetport but did it 1000+ RPM lower. This engine makes more low end and midrange power and it will carry past 10k depending on testicular fortitude or otherwise how stupid I'm feeling that day...
The thing is, unlike a street port, there IS no "kick in the pants". It just goes and there isn't really a powerband. It's soft below 2000rpm, that's it.
Last edited by peejay; 12-08-15 at 04:42 PM.
12-08-15, 07:05 PM
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Here's my current MSQ. I seem to recall from the mazspeed days that you've played a little with Megasquirt.
Mind you that it's a bit on the lean side below 4000rpm on purpose, it's happy at WOT and 13.5-14:1. At high RPM it's running quite a bit richer for cooling.
Also note the wildly asymmetrical RPM bins. Mostly I was adding them at random because the engine was perfectly happy with an 8x8. Probably could work equally well with a 3x3.
Every street port I've ever had would have a lightswitch effect at 5500rpm. The tunes would reflect that. When I did my first halfbridge, it made the same peak power as when it was a streetport but did it 1000+ RPM lower. This engine makes more low end and midrange power and it will carry past 10k depending on testicular fortitude or otherwise how stupid I'm feeling that day...
The thing is, unlike a street port, there IS no "kick in the pants". It just goes and there isn't really a powerband. It's soft below 2000rpm, that's it.
Mind you that it's a bit on the lean side below 4000rpm on purpose, it's happy at WOT and 13.5-14:1. At high RPM it's running quite a bit richer for cooling.
Also note the wildly asymmetrical RPM bins. Mostly I was adding them at random because the engine was perfectly happy with an 8x8. Probably could work equally well with a 3x3.
Every street port I've ever had would have a lightswitch effect at 5500rpm. The tunes would reflect that. When I did my first halfbridge, it made the same peak power as when it was a streetport but did it 1000+ RPM lower. This engine makes more low end and midrange power and it will carry past 10k depending on testicular fortitude or otherwise how stupid I'm feeling that day...
The thing is, unlike a street port, there IS no "kick in the pants". It just goes and there isn't really a powerband. It's soft below 2000rpm, that's it.
Can you post some pics of your set up? Thanks
12-08-15, 07:59 PM
#15
Yes, I've messed with MegaSquirt a little.
If I recall correctly, 100 = saturation mode or full time opening of the injectors, right? Then why are yours up to 139? Is it because the map never gets up there? Is it not scaled correctly? Or did you have to do some creative tuning to make it run the way you wanted?
I certainly had to do some creative out of the box thinking on my MegaSquirt to get it to run 3 rotors with direct fire of 180 degrees per rotor face while still maintaining the proper 120 degree separation amounting to a spark event every 60 degrees like a V12, because that's how I roll, but my tuning of MegaSquirt amounts to a borrowed laptop which I wasn't all that familiar with, using MegaTune which I didn't know how to use all that well, no wideband, and playing around with idle RPM bins ranging from 45 to 25 to get it to stop brapping at idle with a walbro 255 which it turns out has a base pressure of like 60 psi. No wonder it wanted to flood every time I'd go to start it. No wonder it ran so rich. No one ever mentioned anything on the forum back then about these fuel pumps so I had no clue. I just went with it because it's what everyone said to use. Or the Bosch 044 if I was looking to make bigger power.
I didn't have anyone around to help me and I had just spent nearly a decade of off and on messing with the engine's mechanicals and wiring harness building along with soldering the MegaSquirt and everything else you can think of, and I was sidelined by a severe deficiency in how I was supposed to tune the dang thing. And even then, I had creeping doubts or rather little faith it would do what I wanted powerwise in the end as an NA. In other words, the outcome was extremely disappointing compared to what I was essentially promised a streetported 20B was supposed to have I.E. 250 HP for a stock port NA and 300 HP for a streetport NA. Um, no. Not even close. I think I'd know if I was making anywhere close to 200HP like I am now with the turbo 13B. The 20B was probably only ever about 120 to 150HP maybe. But then again, seeing as my NA Nikki was probably doing around 130 to 140HP and wanting to break it loose in 1st gear, which is something the 20B never even came close to, well, it's pretty obvious the 20B was even less powerful than that. Sad.
A simple carb in the other car; a basic stock 13B Hitachi on the Icy engine, was like a night and day difference. Like a kick in the gut. Sure it wasn't super powerful but it had drivability that I just couldn't manage with the MegaSquirt. Probably about the same power as the 20B, actually. So sad.
And there wasn't anything wrong with the 20B. It just was the final result of all that went into it not living up to my expectations. Putting my best efforts into the MS yielded one of the worst driving experiences I had since I first test ran the Racing Nikki in early '12 and neither its primary circuit nor its secondary were working using Pineapple Racing's or rather Dave *******'s recommended tune. The carb only had an idle circuit and an accel pump that functioned at that point. lol I got it around the block, just like I did with the MegaSquirt, but it sucked! After that I swapped in a set of friggin stock SA air bleeds and the carb actually worked. Sheesh! Some people!
Getting back to my EFI experience, it was like an orchestra of disappointment and energy-in not equaling energy-out, on top of having to pull myself up by my bootstraps to get anything done, that it simply drove out any lingering enjoyment I might have had of the experience. I seriously didn't enjoy anything about the process. Coming from a background with zero EFI experience, it was a steep learning curve to begin with. The engine in question being my very first EFI engine ever, you can imagine at least a few reasons why I struggled so much and eventually decided to give up. You can go read my build thread to get a sense of the stress I was piling onto myself during a time I was still under the delusion that I could make it work.
I eventually had to come to terms with the reality that it just wasn't worth it in the end. So I sold all my EFI stuff and focused entirely on Nikkis. This has been a far more pleasant, if trying at times, learning experience. And I now have a setup that is more powerful than PercentSevenC's streetported FD engine we installed in his white car with a MegaSquirt that he spent weeks street tuning. I've only ever street tuned my stuff. And my hogged out Nikki with the same S5 turbo at less boost and no intercooler (his car had a big decent one in front of his radiator and slightly higher boost) has more instant power and better tip-in. Just about the only thing his FD setup had going for it that mine lacked, was the unmistakable FD upper manifold when you lift the hood. Then again it covers up the engine. Lame.
Spinning the tires in 1st, 2nd or 3rd is just a flex of the ankle away on my setup. I was going to try 4th but then my clutch slipped so I'll do a clutch job eventually.
Obviously his car had a lot of power and could spin them easily as well, but I don't think it was as dramatic and "kick in the pants" as mine. Plus his car still had the small stock 13" plus style rims with little 60 series tires and a lighter chassis; his being an 83 GSL while mine has the stock taller 14" GSL-SE rims with stock size tires and higher chassis weight; bigger diameter brakes etc making mine more difficult to break traction under any condition.
So comparing apples to apples as much as possible, mine wins. So much so that he now wants me to tear out the crappy FD setup with prejudice and install something similar to mine. I can't wait for Spring time!
Doing these projects over the last few years really has driven home the reality of how awesome or how bad/time consuming rotaries can be. I think if you focus on their strengths, they will never disappoint you and can even surprise you at times.* That's been my experience dealing with Nikkis for the past year and eight months. I think I've gotten pretty good at them. And knowing that I'm not all that special, that just about anyone over the past 30 plus years since the first modern '81 FB Nikkis came out, could have figured out how to get these carbs to perform this well. And yet it took us this long to get here. It took me, actually, trying to get them to work on my unique setup, to get this far. I know I wouldn't be where I am if it wasn't for Sterling semi-directly, Robert, bad83 and Yaw non-directly, and the Racing Nikki directly testing it on the R5 13B and taking inspiration from it to mod my first FB carb early last year in Feb '14 by first hogging it out for NA flow, but always with an eye on boost prepping. The rest is history.
*I seriously doubt a piston engine could return this kind of enjoyment for this little cost and using so many factory parts.
I don't see any reason to do any other kind of intake these days. Now when I read about problems people are having with their setups, whether it be non Nikki carb related or anything to do with EFI, I can only relay my story where appropriate and hope they get their thing working right. I mean heck I had to go through the process; wasted too much money and time on other setups which I'll never get back. I guess the only difference between me and someone else is I stuck with rotaries when someone else might go to an Evo or something stupid like that. Interesting that I'd compare a rotary to one of those. I didn't compare it to some crappy little grocery getter. Then again, those things make like 200HP these days. Of course they're heavy as heck so they need that kind of power. They're all gray now too. New cars suck.
If I recall correctly, 100 = saturation mode or full time opening of the injectors, right? Then why are yours up to 139? Is it because the map never gets up there? Is it not scaled correctly? Or did you have to do some creative tuning to make it run the way you wanted?
I certainly had to do some creative out of the box thinking on my MegaSquirt to get it to run 3 rotors with direct fire of 180 degrees per rotor face while still maintaining the proper 120 degree separation amounting to a spark event every 60 degrees like a V12, because that's how I roll, but my tuning of MegaSquirt amounts to a borrowed laptop which I wasn't all that familiar with, using MegaTune which I didn't know how to use all that well, no wideband, and playing around with idle RPM bins ranging from 45 to 25 to get it to stop brapping at idle with a walbro 255 which it turns out has a base pressure of like 60 psi. No wonder it wanted to flood every time I'd go to start it. No wonder it ran so rich. No one ever mentioned anything on the forum back then about these fuel pumps so I had no clue. I just went with it because it's what everyone said to use. Or the Bosch 044 if I was looking to make bigger power.
I didn't have anyone around to help me and I had just spent nearly a decade of off and on messing with the engine's mechanicals and wiring harness building along with soldering the MegaSquirt and everything else you can think of, and I was sidelined by a severe deficiency in how I was supposed to tune the dang thing. And even then, I had creeping doubts or rather little faith it would do what I wanted powerwise in the end as an NA. In other words, the outcome was extremely disappointing compared to what I was essentially promised a streetported 20B was supposed to have I.E. 250 HP for a stock port NA and 300 HP for a streetport NA. Um, no. Not even close. I think I'd know if I was making anywhere close to 200HP like I am now with the turbo 13B. The 20B was probably only ever about 120 to 150HP maybe. But then again, seeing as my NA Nikki was probably doing around 130 to 140HP and wanting to break it loose in 1st gear, which is something the 20B never even came close to, well, it's pretty obvious the 20B was even less powerful than that. Sad.
A simple carb in the other car; a basic stock 13B Hitachi on the Icy engine, was like a night and day difference. Like a kick in the gut. Sure it wasn't super powerful but it had drivability that I just couldn't manage with the MegaSquirt. Probably about the same power as the 20B, actually. So sad.
And there wasn't anything wrong with the 20B. It just was the final result of all that went into it not living up to my expectations. Putting my best efforts into the MS yielded one of the worst driving experiences I had since I first test ran the Racing Nikki in early '12 and neither its primary circuit nor its secondary were working using Pineapple Racing's or rather Dave *******'s recommended tune. The carb only had an idle circuit and an accel pump that functioned at that point. lol I got it around the block, just like I did with the MegaSquirt, but it sucked! After that I swapped in a set of friggin stock SA air bleeds and the carb actually worked. Sheesh! Some people!
Getting back to my EFI experience, it was like an orchestra of disappointment and energy-in not equaling energy-out, on top of having to pull myself up by my bootstraps to get anything done, that it simply drove out any lingering enjoyment I might have had of the experience. I seriously didn't enjoy anything about the process. Coming from a background with zero EFI experience, it was a steep learning curve to begin with. The engine in question being my very first EFI engine ever, you can imagine at least a few reasons why I struggled so much and eventually decided to give up. You can go read my build thread to get a sense of the stress I was piling onto myself during a time I was still under the delusion that I could make it work.
I eventually had to come to terms with the reality that it just wasn't worth it in the end. So I sold all my EFI stuff and focused entirely on Nikkis. This has been a far more pleasant, if trying at times, learning experience. And I now have a setup that is more powerful than PercentSevenC's streetported FD engine we installed in his white car with a MegaSquirt that he spent weeks street tuning. I've only ever street tuned my stuff.
And my hogged out Nikki with the same S5 turbo at less boost and no intercooler (his car had a big decent one in front of his radiator and slightly higher boost) has more instant power and better tip-in. Just about the only thing his FD setup had going for it that mine lacked, was the unmistakable FD upper manifold when you lift the hood. Then again it covers up the engine. Lame.Spinning the tires in 1st, 2nd or 3rd is just a flex of the ankle away on my setup. I was going to try 4th but then my clutch slipped so I'll do a clutch job eventually.
Obviously his car had a lot of power and could spin them easily as well, but I don't think it was as dramatic and "kick in the pants" as mine. Plus his car still had the small stock 13" plus style rims with little 60 series tires and a lighter chassis; his being an 83 GSL while mine has the stock taller 14" GSL-SE rims with stock size tires and higher chassis weight; bigger diameter brakes etc making mine more difficult to break traction under any condition.
So comparing apples to apples as much as possible, mine wins. So much so that he now wants me to tear out the crappy FD setup with prejudice and install something similar to mine. I can't wait for Spring time!
Doing these projects over the last few years really has driven home the reality of how awesome or how bad/time consuming rotaries can be. I think if you focus on their strengths, they will never disappoint you and can even surprise you at times.* That's been my experience dealing with Nikkis for the past year and eight months. I think I've gotten pretty good at them. And knowing that I'm not all that special, that just about anyone over the past 30 plus years since the first modern '81 FB Nikkis came out, could have figured out how to get these carbs to perform this well. And yet it took us this long to get here. It took me, actually, trying to get them to work on my unique setup, to get this far. I know I wouldn't be where I am if it wasn't for Sterling semi-directly, Robert, bad83 and Yaw non-directly, and the Racing Nikki directly testing it on the R5 13B and taking inspiration from it to mod my first FB carb early last year in Feb '14 by first hogging it out for NA flow, but always with an eye on boost prepping. The rest is history.
*I seriously doubt a piston engine could return this kind of enjoyment for this little cost and using so many factory parts.
I don't see any reason to do any other kind of intake these days. Now when I read about problems people are having with their setups, whether it be non Nikki carb related or anything to do with EFI, I can only relay my story where appropriate and hope they get their thing working right. I mean heck I had to go through the process; wasted too much money and time on other setups which I'll never get back. I guess the only difference between me and someone else is I stuck with rotaries when someone else might go to an Evo or something stupid like that. Interesting that I'd compare a rotary to one of those. I didn't compare it to some crappy little grocery getter. Then again, those things make like 200HP these days. Of course they're heavy as heck so they need that kind of power. They're all gray now too. New cars suck.
12-09-15, 01:34 PM
#16
I mention this next part because it is relevant and ties everything together. I performed this test on these three engines and Percent performed it on his FD engine: You're driving along in 1st gear and mash the pedal to the floor. What happens? For practical purposes, let's say the RPM is around 3000 or so.
The 20B slams you back in the seat, then coughs and falls on its face due to air stalling, you panic and let off, the throttle blade goes back to its sweetspot and slams you back in the seat one more time as your foot is leaving the pedal. I thought I got rearended it was so forceful. I checked my mirrors to see if there was a car behind me. Nope, just a little oil smoke from old oil seals. Actually, this was in the GLC back when the 20B was a stockport. I determined it was too much engine for the car so I pulled it and swapped it into the brown car. Back up, I rebuilt and streetported it before it went in the brown car. I then did the same instant acceleration test. This time it was a little softer; less "I got rearended" feeling, obviously due to the large ports hurting low end torque, and took it up to only 5000 RPM as it was a fresh rebuild and not really tuned yet. It wasn't bad, but both tires certainly held their grip just fine. Never even came close to wanting to break them loose in gear. Sounded kinda cool, being a 3 rotor, but you're right about them sounding kinda strange too. I first tested the brown car on a short header collected to 3" which had less power than when I did a long primary collecting all three primaries to 2.5" in front of an RB FC presilencer meant for an NA with the backpressure sensing tube removed. The muffler was swapped to an RB powerpulse from a full RB system I had, chopped after where the two tubes collect to 2.375". Going from 2.5" to 2.375" isn't bad and it flowed a lot of exhaust which you could see as a little bit of oil smoke and blackish smoke from being too rich.
Up next, or rather before the 20B, the half BP 12A had a stock old school Nikki meant for channels but worked great on a separate runner manifold as that tends to make the idle rich and allowed it to idle better than the original old school Nikki meant for separate runner manifolds. There is a difference in the way the idle and transition circuits are calibrated. Anyway the pretty much stock Nikki didn't have all that much low end torque due to its tiny 20mm venturis, but the mechanical secondaries were amazing! The exhaust was just a measly cast iron manifold on the exact same 3" center section and muffler I later tested on the 20B and then later on the turbo R5 13B. As interesting as the half BP was, it was hard to start (obviously a Nikki with huge stock short slow air bleeds and no choke flap will be hard to start every time regardless of the engine it's on, but I didn't know this back then, and BPs are harder to start than regular side ports anyway, at least as far as I know).
Now we come to the present. It is the 74 ported R5 13B currently in the brown car. While I was testing my first hogged out Nikki cut to 24.9mm and had no idea what I was doing with air bleeds etc, and just trying stuff in general without a wideband, I noticed it had more power than the half BP 12A did at any RPM so I decided I wouldn't do another half BP or even full BP 12A if a basic 74 ported 13B could walk all over it, but just yesterday I realized that the first BP I did wasn't fully utilized. I assumed the knife edged RX-2 manifold would be beneficial for one thing, which has just been proven false, but I do have another manifold from an RX-3 that will suffice, and now that I have pretty good Nikki knowledge, I could take advantage of it and use the full RB exhaust I mentioned earlier. That's why I was calling it half BP 12A Mark II or whatever. It would be a way to maybe get close to the power of the brown car's current 13B turbo setup without having to deal with turbos.
But as for power, I know the brown car's 13B has plenty even while NA because it wanted to break them loose in 1st gear when it was only me in it, no passenger, no spare tire, and basically an empty tank; like driving to the gas station. The car was as light as it was ever going to be without stupid weight reduction measures. It could only do this when the mechanical secondaries would open on the Racing Nikki or a properly set up hogged out boost prepped Nikki done as correctly as I could do them last year. The carbs weren't all that great back then because they weren't modded or tuned as well as they are now. Makes me want to try this instant acceleration test again with one of my modern hogged out boost prepped carbs in NA mode just to compare apples to apples on the same engine.
Percent's FD setup was weird. The idle was crummy and isn't really a good candidate. I say "was" because it doesn't run anymore. But when it did, it had some great tip-in and power. It really was no slouch, but all the work that went into it, and the fact it still had problems that he just couldn't solve, all I can say is it was about the same as the brown car's 13B with a Nikki, just far more prone to problems and far more complicated taking all the fun factor out of it. We won't be doing another one of these.
The 20B slams you back in the seat, then coughs and falls on its face due to air stalling, you panic and let off, the throttle blade goes back to its sweetspot and slams you back in the seat one more time as your foot is leaving the pedal. I thought I got rearended it was so forceful. I checked my mirrors to see if there was a car behind me. Nope, just a little oil smoke from old oil seals. Actually, this was in the GLC back when the 20B was a stockport. I determined it was too much engine for the car so I pulled it and swapped it into the brown car. Back up, I rebuilt and streetported it before it went in the brown car. I then did the same instant acceleration test. This time it was a little softer; less "I got rearended" feeling, obviously due to the large ports hurting low end torque, and took it up to only 5000 RPM as it was a fresh rebuild and not really tuned yet. It wasn't bad, but both tires certainly held their grip just fine. Never even came close to wanting to break them loose in gear. Sounded kinda cool, being a 3 rotor, but you're right about them sounding kinda strange too. I first tested the brown car on a short header collected to 3" which had less power than when I did a long primary collecting all three primaries to 2.5" in front of an RB FC presilencer meant for an NA with the backpressure sensing tube removed. The muffler was swapped to an RB powerpulse from a full RB system I had, chopped after where the two tubes collect to 2.375". Going from 2.5" to 2.375" isn't bad and it flowed a lot of exhaust which you could see as a little bit of oil smoke and blackish smoke from being too rich.
Up next, or rather before the 20B, the half BP 12A had a stock old school Nikki meant for channels but worked great on a separate runner manifold as that tends to make the idle rich and allowed it to idle better than the original old school Nikki meant for separate runner manifolds. There is a difference in the way the idle and transition circuits are calibrated. Anyway the pretty much stock Nikki didn't have all that much low end torque due to its tiny 20mm venturis, but the mechanical secondaries were amazing! The exhaust was just a measly cast iron manifold on the exact same 3" center section and muffler I later tested on the 20B and then later on the turbo R5 13B. As interesting as the half BP was, it was hard to start (obviously a Nikki with huge stock short slow air bleeds and no choke flap will be hard to start every time regardless of the engine it's on, but I didn't know this back then, and BPs are harder to start than regular side ports anyway, at least as far as I know).
Now we come to the present. It is the 74 ported R5 13B currently in the brown car. While I was testing my first hogged out Nikki cut to 24.9mm and had no idea what I was doing with air bleeds etc, and just trying stuff in general without a wideband, I noticed it had more power than the half BP 12A did at any RPM so I decided I wouldn't do another half BP or even full BP 12A if a basic 74 ported 13B could walk all over it, but just yesterday I realized that the first BP I did wasn't fully utilized. I assumed the knife edged RX-2 manifold would be beneficial for one thing, which has just been proven false, but I do have another manifold from an RX-3 that will suffice, and now that I have pretty good Nikki knowledge, I could take advantage of it and use the full RB exhaust I mentioned earlier. That's why I was calling it half BP 12A Mark II or whatever. It would be a way to maybe get close to the power of the brown car's current 13B turbo setup without having to deal with turbos.
But as for power, I know the brown car's 13B has plenty even while NA because it wanted to break them loose in 1st gear when it was only me in it, no passenger, no spare tire, and basically an empty tank; like driving to the gas station. The car was as light as it was ever going to be without stupid weight reduction measures. It could only do this when the mechanical secondaries would open on the Racing Nikki or a properly set up hogged out boost prepped Nikki done as correctly as I could do them last year. The carbs weren't all that great back then because they weren't modded or tuned as well as they are now. Makes me want to try this instant acceleration test again with one of my modern hogged out boost prepped carbs in NA mode just to compare apples to apples on the same engine.
Percent's FD setup was weird. The idle was crummy and isn't really a good candidate. I say "was" because it doesn't run anymore. But when it did, it had some great tip-in and power. It really was no slouch, but all the work that went into it, and the fact it still had problems that he just couldn't solve, all I can say is it was about the same as the brown car's 13B with a Nikki, just far more prone to problems and far more complicated taking all the fun factor out of it. We won't be doing another one of these.
12-09-15, 02:12 PM
#17
Waffles - hmmm good
iTrader: (1)
Nice to read about all the experiments you have done over the years Jeff.
I have to say my fat nikki will break the tires loose in 1st and 2nd no problem at low or high
rpm as long as the secondaries kick in. When my secondaries kick in its the same feel I have
experienced when riding in someones turboed rotary. Its like, bam, it kicks in and things
happen fast. I can probably tone this down with some more tuning on the primary and AP but
I kind of like it as is. Also theres a lot of pedal pressure needed to push it into the
secondaries, not sure if this is a tuning issue or how I have my secondaries hardwired. This
extra pressure makes it easy to cruise at the best MPG rate as well.
This is all on an 80 stockport 12A as well. I can't imagine what it will be like ported. I do have
some 12As laying bout in pieces waiting to be built up.
I have to say my fat nikki will break the tires loose in 1st and 2nd no problem at low or high
rpm as long as the secondaries kick in. When my secondaries kick in its the same feel I have
experienced when riding in someones turboed rotary. Its like, bam, it kicks in and things
happen fast. I can probably tone this down with some more tuning on the primary and AP but
I kind of like it as is. Also theres a lot of pedal pressure needed to push it into the
secondaries, not sure if this is a tuning issue or how I have my secondaries hardwired. This
extra pressure makes it easy to cruise at the best MPG rate as well.
This is all on an 80 stockport 12A as well. I can't imagine what it will be like ported. I do have
some 12As laying bout in pieces waiting to be built up.
12-09-15, 02:58 PM
#18
I made my old SA 79 12a half bridge turbo fuel injection , with a RB holley intake, accel TBI, Microtech ECU, turbonetics t72 turbo, dyno 337 WHP @ 9 psi. That was 7 years ago i sold the car 3 years ago
The Accel tbi is made to fit in the RB holley intake .
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The Accel tbi is made to fit in the RB holley intake .
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12-09-15, 03:06 PM
#19
Thanks.
It's pretty well known that a lot of things were changed about the Nikki for the 81 model year. One thing they changed is the timing for when the secondaries would open. From just looking at the differences, I'd say the 81 and later Nikkis open their secondaries at 60% throttle. The SA carbs and all old schools opened at 70%. I recall wankel=awesome asking why it was so hard to open the wired secondaries on his old school '76 nikki, wondering if he did it correctly.
I don't know whether it's the 70% timing or the way the linkage was wired but I suspect the latter. Why? Because I have two 79 carbs which I tack welded the two steel tabs where they meet. I made sure to keep everything centered with no side loading before I tacked them. The end result are secondaries that open just fine with no issues or binding at all. You can feel the hard spot plain as day just like on the FB carbs but it's certainly not complaint worthy. Maybe your linkage is binding slightly? I know I used to wire tie my secondaries but that was way back in the day before I had a chance to develop a feel for properly welded secondaries.
As for your fat nikki, I think it would be wise to get back into it and measure how far you cut your primary venturis. I use this measurement to size carbs properly for engines. There is plenty of overlap to play around with, but so far I've gotten feedback that 24.45mm to 24.5mm is a pretty good size (if a bit on the large side) on a stockported 12A, with no problems reported other than the tiny flat spot around 1700 which the accel pump covers nicely. In other words it's never noticed when you're driving it but can be found if just idling it up during warmup or whatever.*
The point I'm trying to make is if you were to enlarge your primaries a little more, the primary power would increase as well as total power when all four barrels are open, however the amazing transcendent rush of extra power you feel when the secondaries open would feel a bit less dramatic if the primaries were more powerful. Does that makes sense? I mentioned this to you before as a way of proving you could hog your primaries out a bit bigger and it wouldn't hurt drivability. In other words, your engine could handle somewhat bigger primaries if you wanted to go that route.
Would it still break them loose as easily when the secondaries open you ask? Well, with more power on the primaries, it just might break them loose on primaries only like mine does these days. But who knows. It's your first hogged out Nikki. I've done like ten of them at least. Probably more like 15 and I'm still learning. But so far I've gotten it down to an almost rote memory sort of thing. It's nearly down to a science where if I do a) I'll get b) as the result every time. But these carbs still surprise me with what I can do with them. Hence the half BP I'd like to try again, this time with enough Nikki knowledge that I think I could get it to run and drive with a lot more power and easier starts than the one back in 2011 had. And I'd like to try it in the brown car where I've done all my Nikki testing so far.
Getting back to the half BP, the updated list will include the sep runner RX-3 manifold and the 25.2mm hogged out boost prepped Nikki for NA use which, being an FB carb, gives me an eventual turbo option unlike the Racing Nikki which, being a 79, isn't really capable of handling boost. At least I'm not interested in risking the engine on a lean spot at 70% throttle like I experienced before from this carb. Of course that was back when it had stock 90 SA air bleeds. I still have to test it with FB's 70s but then I still have the 70% secondary linkage timing so I'll just save the Racing Nikki for a big streetported 12A for which it was originally intended. Or maybe a full bridge? Nah, gotta do a half BP first.
*One note about using a carb with venturis this big: you have to have a free flowing exhaust and intake. What this means to me is an RB long primary and at least a 79 intake manifold with a spun aluminum air filter or equivalent. It also helps to have direct fire ignition, not because it's mandatory, but because it works so much better than the stock cap 'n rotor. And if you still have points, I'm sorry.
It's pretty well known that a lot of things were changed about the Nikki for the 81 model year. One thing they changed is the timing for when the secondaries would open. From just looking at the differences, I'd say the 81 and later Nikkis open their secondaries at 60% throttle. The SA carbs and all old schools opened at 70%. I recall wankel=awesome asking why it was so hard to open the wired secondaries on his old school '76 nikki, wondering if he did it correctly.
I don't know whether it's the 70% timing or the way the linkage was wired but I suspect the latter. Why? Because I have two 79 carbs which I tack welded the two steel tabs where they meet. I made sure to keep everything centered with no side loading before I tacked them. The end result are secondaries that open just fine with no issues or binding at all. You can feel the hard spot plain as day just like on the FB carbs but it's certainly not complaint worthy.
Maybe your linkage is binding slightly? I know I used to wire tie my secondaries but that was way back in the day before I had a chance to develop a feel for properly welded secondaries.As for your fat nikki, I think it would be wise to get back into it and measure how far you cut your primary venturis. I use this measurement to size carbs properly for engines. There is plenty of overlap to play around with, but so far I've gotten feedback that 24.45mm to 24.5mm is a pretty good size (if a bit on the large side) on a stockported 12A, with no problems reported other than the tiny flat spot around 1700 which the accel pump covers nicely. In other words it's never noticed when you're driving it but can be found if just idling it up during warmup or whatever.*
The point I'm trying to make is if you were to enlarge your primaries a little more, the primary power would increase as well as total power when all four barrels are open, however the amazing transcendent rush of extra power you feel when the secondaries open would feel a bit less dramatic if the primaries were more powerful. Does that makes sense? I mentioned this to you before as a way of proving you could hog your primaries out a bit bigger and it wouldn't hurt drivability. In other words, your engine could handle somewhat bigger primaries if you wanted to go that route.
Would it still break them loose as easily when the secondaries open you ask? Well, with more power on the primaries, it just might break them loose on primaries only like mine does these days.
But who knows. It's your first hogged out Nikki. I've done like ten of them at least. Probably more like 15 and I'm still learning. But so far I've gotten it down to an almost rote memory sort of thing. It's nearly down to a science where if I do a) I'll get b) as the result every time. But these carbs still surprise me with what I can do with them. Hence the half BP I'd like to try again, this time with enough Nikki knowledge that I think I could get it to run and drive with a lot more power and easier starts than the one back in 2011 had. And I'd like to try it in the brown car where I've done all my Nikki testing so far.Getting back to the half BP, the updated list will include the sep runner RX-3 manifold and the 25.2mm hogged out boost prepped Nikki for NA use which, being an FB carb, gives me an eventual turbo option unlike the Racing Nikki which, being a 79, isn't really capable of handling boost. At least I'm not interested in risking the engine on a lean spot at 70% throttle like I experienced before from this carb. Of course that was back when it had stock 90 SA air bleeds. I still have to test it with FB's 70s but then I still have the 70% secondary linkage timing so I'll just save the Racing Nikki for a big streetported 12A for which it was originally intended. Or maybe a full bridge? Nah, gotta do a half BP first.
*One note about using a carb with venturis this big: you have to have a free flowing exhaust and intake. What this means to me is an RB long primary and at least a 79 intake manifold with a spun aluminum air filter or equivalent. It also helps to have direct fire ignition, not because it's mandatory, but because it works so much better than the stock cap 'n rotor. And if you still have points, I'm sorry.
Last edited by Jeff20B; 12-09-15 at 03:20 PM.
12-09-15, 06:02 PM
#20
Old [Sch|F]ool
The numbers actually can go as high as 255, IIRC
12-10-15, 07:18 AM
#24
Waffles - hmmm good
iTrader: (1)
Definitely need to measure how much I have the venturis hogged out. I'm sure theres some
meat left in there. I did it pretty conservatively.
I want to add a dual AFR since I have the bungs already in the rear of the center section for
each pipe. Then I can play with it in confidence.
meat left in there. I did it pretty conservatively.
I want to add a dual AFR since I have the bungs already in the rear of the center section for
each pipe. Then I can play with it in confidence.