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I can’t wait to get rid of the BP engine installed by the previous owner
the whole brapping thing is overhyped by the attention harlot crowd, even if you can get it to idle at a lower speed it’s still annoying to a hydrocarbon-stenching fault, and more importantly not necessary at all with a turbo either. If you’re going there then semi PP makes more sense on every level.
funny to be reading your responses now like you have it all figured out before having even gone there, but then glossed right over the example I gave you for a large street port. That engine at 25 psi would be in the low 600 whp range. In other words, right where you were looking to be in the 22 psi range.
what you still didn’t grasp fully yet is that the terms street port, bridge port, etc are only words. What ultimately matters is the opening and closing timing points. There’s a lot of undefined variation out there …
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Originally Posted by j9fd3s
mostly this is tuning, my Peripheral port idles ~900rpm, like the manual say it should. this is with a carb and locked distributor too, so with EFI, you should be able to idle around there with ease.
the engine is capable of idling lower, but the carburetor is my limitation
sort of, you smell like potato chips, which is better. if you say go dyno, breathing the fumes will still turn your head to mush though, just like regular gas.
E85 is nice though, we ran it in a miata, and just by dumping it in the tank we got 3-4hp, which is really good for that. it also would tolerate hot days better.
they shouldn't, again that is a tuning problem. a bridge or PP won't be happy at mid rpm (2-4k) and low throttle openings (if you are behind a prius), but other than that it should start and run and drive like stock. a street port should run like stock.
if you have a bigger turbo and more boost, it should just shove you in the back harder
we have fancy ECU's now, we can make the engine happy all the time
Thanks for the input.
E85 still smells but I think it is completely different fro pump gas and much more tolerable.
My builder is think an idle around 1300. If it can go lower awesome.
Exhaust porting is where you can really ruin driveability of a turbo car in my experience.
I would leave stock FD exhaust ports stock up to ~550rwhp level.
if you over port the exhaust (anything "up or wider") it makes it harder to get going from a stop- gotta abuse the clutch.
If you are idling at 2,000rpm like most poorly tuned bridges and semi p-ports it probably has no/little negative affects though.
I really noticed the downsides from 800rpm idle to 3,000rpm on an overly large street port.
Here are the ports I had.
Keep it more like the Left if anything- just down a bit for earlier opening/better spool and shaped for flow. The Right where it was larger and ported up was doggy off idle.
Thanks for sharing.
I was/am assuming my builder will do more of a "clean up" on exhaust as we really did not discus this.
It is intreating hear your experience with exhaust port as I would assume opening them up (trying to avoid timing interruption) would assist with turbo as I would think "free flowing" .
E85 still smells but I think it is completely different fro pump gas and much more tolerable.
it smells like potato chips, which is nice. a persons ability to tolerate, what is still a bunch of weird chemicals is about the same as regular gasoline.
Some tuners crank timing up to like 40 degrees at idle so the throttle plates can stay closed. This kills the idle. I like to idle around 5ATDC and open the throttle plates more. On a half bridge with the stock FC throttle body/intake I will remove the secondary throttle stop bolt and use a longer one, so most of the idle air comes through the secondaries. This helps idle a ton by killing the vacuum that the bridged ports see. It also helps low throttle drivability like cruising at 50-60mph.
Some tuners crank timing up to like 40 degrees at idle so the throttle plates can stay closed. This kills the idle. I like to idle around 5ATDC and open the throttle plates more. On a half bridge with the stock FC throttle body/intake I will remove the secondary throttle stop bolt and use a longer one, so most of the idle air comes through the secondaries. This helps idle a ton by killing the vacuum that the bridged ports see. It also helps low throttle drivability like cruising at 50-60mph.
All basically ar 1k-1100. That not bad at all. Thank you for sharing
1st link is interesting for hp with a bridge port. Id think more power would be available.
The 2nd link is crazy to run pump gas (91)and hit power at that psi with out worry.
Bridgeport is a catch-all term, there are many many different variations. Mine is a 6mm half bridge, I chose 3pc seals over the option of having a bridge on the primary. Some bridgeports work well, some don't, a lot of it is down to the back cut, exhaust port, and the turbocharger itself. The turbo and CR are mostly what determine how much power is available, the port should be chosen to match the turbocharger and intended usage. My setup makes full boost at 3600RPM, holds tq almost 1000RPM later than the same turbo on a stock port, and traps 130MPH on pump gas. IMO that is a good match between port, turbo, and usage. Your usage and power goals may be different so your exact bridgeport and turbo selection will need to reflect that.
"Some advantages for HBP is less stress on the engine, lower boost pressure requirements for 450 + rewhp, small turbo requirements.
Then I read mpg not drastically effected with HBP If tuned semi correctly."
"And my limited understanding is that bridge ports assist with moving air to allow for higher HP with out the need for so much boost pressure. A bridge port can/is streetable with proper tune."
These are... sort of correct? There is only less stress if you make less power, the difference isn't that drastic. Going bridgeport to avoid running an appropriate amount of boost is counterproductive IMO. Small turbo requirements is incorrect if you are thinking that you can use the airflow increase to downsize your turbo. It's a change in port timing and area, not a displacement increase. Fuel economy suffers everywhere but steady state cruise. Noise is increased and the ability to muffle that noise without killing power is reduced. Drivability is absolutely negatively impacted. The idle and "braps" are a non-issue IMO but minute throttle openings at certain points around 2400RPM cause significant bucking - you will get used to clutching in at turnoffs and in parking lots.
at 17 psi hits just over 500 rewhip on a mixture or pumps and ethanol? Impressive."
Keep in mind that whp numbers on a dogbox are usually not apples to apples with most results you see. He doesn't specify there but a straight cut box will typically give higher numbers on a chassis dyno than a factory box. Scalloped 8.5:1 rotors, 4" exhaust, dogbox, E30, modded UIM... this is not a typical streetport. Those exhaust ports look very similar to Adam Saruwatari's drag car bits. Obviously I can't say without driving it but I suspect that car is less "streetable" than a mild bridgeport by most metrics.
"Over the years I have seen many people advise not to boost at those levels with pump gas. In many cases AI was recommenced at the least.
Talking with builder tomorrow and see what his thoughts are. Again I am looking for mid 500s but not stressing the engine so much. Maybe hit 22 psi."
I've been up to 1.4 bar on 91 octane and 9:1 rotors, Max has been higher on 8.5:1. If you are paying someone else to do your work then you do what they say, but there are ways to run pretty big boost numbers on pump. In Japan I saw a handful of cars that would run ~1.9 bar on 98-100RON.
"the whole brapping thing is overhyped by the attention harlot crowd, even if you can get it to idle at a lower speed it’s still annoying to a hydrocarbon-stenching fault, and more importantly not necessary at all with a turbo either. If you’re going there then semi PP makes more sense on every level."
The only time a semi-PP makes sense is if you are racing in a series that prohibits full periport, and there are plenty of times when a BP makes more sense than PP. I guess I'm an attention harlot, but the thought of owning a rotary that drives exactly like a standard piston ICE really doesn't interest me all that much.
Just be aware that idle is idle... anything with overlap does NOT like low load. That brap brap brap is the engine accelerating and decelerating constantly. If you have a 30lb flywheel it is acceptable-ish, if you have a 9lb flywheel you find ALL the lash in your transmission and rearend and bushings and motor mounts until you give it enough load to run smoothly. Which is in my experience around 65kpa at 3000rpm manifold pressure, give or take depending on other tuning factors like ignition timing and exhaust free-flow, and it is a slope. It can be perverse to where you can't cruise faster because the engine is turning faster and is no longer loaded enough at the new RPM. I can drive at 60-65 but not 80 with my setup.
I literally wore out my left knee constantly shifting in and out of gear driving in the city because you can't coast or cruise at low speeds, you have to have enough load on it, so it is constantly accelerating, shift to neutral and coast, shift into gear and accelerate a little, shift into gear and coast...
That engine that purrs at 1000rpm is more like this at just a little more speed...
That knocking you hear is the exhaust hangers from the drivetrain bouncing around...
You have to ask yourself, realistically, what you plan on doing with the car and what your expectations are, and what compromises you are willing to make.
Bridgeport is a catch-all term, there are many many different variations. Mine is a 6mm half bridge, I chose 3pc seals over the option of having a bridge on the primary. Some bridgeports work well, some don't, a lot of it is down to the back cut, exhaust port, and the turbocharger itself. The turbo and CR are mostly what determine how much power is available, the port should be chosen to match the turbocharger and intended usage. My setup makes full boost at 3600RPM, holds tq almost 1000RPM later than the same turbo on a stock port, and traps 130MPH on pump gas. IMO that is a good match between port, turbo, and usage. Your usage and power goals may be different so your exact bridgeport and turbo selection will need to reflect that.
"Some advantages for HBP is less stress on the engine, lower boost pressure requirements for 450 + rewhp, small turbo requirements.
Then I read mpg not drastically effected with HBP If tuned semi correctly."
"And my limited understanding is that bridge ports assist with moving air to allow for higher HP with out the need for so much boost pressure. A bridge port can/is streetable with proper tune."
These are... sort of correct? There is only less stress if you make less power, the difference isn't that drastic. Going bridgeport to avoid running an appropriate amount of boost is counterproductive IMO. Small turbo requirements is incorrect if you are thinking that you can use the airflow increase to downsize your turbo. It's a change in port timing and area, not a displacement increase. Fuel economy suffers everywhere but steady state cruise. Noise is increased and the ability to muffle that noise without killing power is reduced. Drivability is absolutely negatively impacted. The idle and "braps" are a non-issue IMO but minute throttle openings at certain points around 2400RPM cause significant bucking - you will get used to clutching in at turnoffs and in parking lots.
at 17 psi hits just over 500 rewhip on a mixture or pumps and ethanol? Impressive."
Keep in mind that whp numbers on a dogbox are usually not apples to apples with most results you see. He doesn't specify there but a straight cut box will typically give higher numbers on a chassis dyno than a factory box. Scalloped 8.5:1 rotors, 4" exhaust, dogbox, E30, modded UIM... this is not a typical streetport. Those exhaust ports look very similar to Adam Saruwatari's drag car bits. Obviously I can't say without driving it but I suspect that car is less "streetable" than a mild bridgeport by most metrics.
"Over the years I have seen many people advise not to boost at those levels with pump gas. In many cases AI was recommenced at the least.
Talking with builder tomorrow and see what his thoughts are. Again I am looking for mid 500s but not stressing the engine so much. Maybe hit 22 psi."
I've been up to 1.4 bar on 91 octane and 9:1 rotors, Max has been higher on 8.5:1. If you are paying someone else to do your work then you do what they say, but there are ways to run pretty big boost numbers on pump. In Japan I saw a handful of cars that would run ~1.9 bar on 98-100RON.
"the whole brapping thing is overhyped by the attention harlot crowd, even if you can get it to idle at a lower speed it’s still annoying to a hydrocarbon-stenching fault, and more importantly not necessary at all with a turbo either. If you’re going there then semi PP makes more sense on every level."
The only time a semi-PP makes sense is if you are racing in a series that prohibits full periport, and there are plenty of times when a BP makes more sense than PP. I guess I'm an attention harlot, but the thought of owning a rotary that drives exactly like a standard piston ICE really doesn't interest me all that much.
Thank you for the input. I trust my builder and will go with his recommendations. He understands with HBP that I will be licking for the best drivability possible.
As I looked a semi pp due to some mentioning by other members, I quickly seen that this option as a "race" option.
Just be aware that idle is idle... anything with overlap does NOT like low load. That brap brap brap is the engine accelerating and decelerating constantly. If you have a 30lb flywheel it is acceptable-ish, if you have a 9lb flywheel you find ALL the lash in your transmission and rearend and bushings and motor mounts until you give it enough load to run smoothly. Which is in my experience around 65kpa at 3000rpm manifold pressure, give or take depending on other tuning factors like ignition timing and exhaust free-flow, and it is a slope. It can be perverse to where you can't cruise faster because the engine is turning faster and is no longer loaded enough at the new RPM. I can drive at 60-65 but not 80 with my setup.
I literally wore out my left knee constantly shifting in and out of gear driving in the city because you can't coast or cruise at low speeds, you have to have enough load on it, so it is constantly accelerating, shift to neutral and coast, shift into gear and accelerate a little, shift into gear and coast...
That engine that purrs at 1000rpm is more like this at just a little more speed...
That knocking you hear is the exhaust hangers from the drivetrain bouncing around...
You have to ask yourself, realistically, what you plan on doing with the car and what your expectations are, and what compromises you are willing to make.
Thank you for sharing and input.
I do not recall how heavy of a flywheel I will get, but I do recall it not being super light for the fact that you mention per my builder.
"That brap brap brap is the engine accelerating and decelerating constantly" make sense and I figured this was causing the brap brap.
"I can drive at 60-65 but not 80 with my setup". Are your referring to cruise at 60-65 and not causing at 80? If so that kind sucks from my perspective. Im hoping I can cruise between 60 and 85 as that how I typically drive. Its been over 15 years from driving a rotary for me. So I know I will have to adapt and adjust.
That is exactly it... not enough load for me. If I had a taller 5th gear it would be better at 80, but then the engine might not be under enough load at 60 to cruise well at lower engine speeds.
Speed limits here are around 60 and I chose my gearing to suit the kind of motorsports I do as the first priority, it is more of a happy accident that my cruise window happens to be where I prefer to drive
Even in my S60R (the 340hp Swedish tank) I find myself cruising at 65ish even though I drive it a lot where the speed limits are higher
The funny thing is I also have a mostly stock '81 RX-7, I find myself driving it at 75+ a lot because the old 12A cars had a weird kind of "coming on plane" effect where because of the way the ignition timing and carburetor sizing and aerodynamic loads and gearing come together, it takes less throttle to cruise at 75 than at 65, engine is quieter, etc. So we will call that an outlier.
It is also far more pleasant to drive than the bridge ported monster. You can drive it like a normal car because it IS one. I put about 8000 miles on it this year vs. only about 1000-1500 on the other RX-7. And about 40k on the Volvo.
That is exactly it... not enough load for me. If I had a taller 5th gear it would be better at 80, but then the engine might not be under enough load at 60 to cruise well at lower engine speeds.
Speed limits here are around 60 and I chose my gearing to suit the kind of motorsports I do as the first priority, it is more of a happy accident that my cruise window happens to be where I prefer to drive
Even in my S60R (the 340hp Swedish tank) I find myself cruising at 65ish even though I drive it a lot where the speed limits are higher
The funny thing is I also have a mostly stock '81 RX-7, I find myself driving it at 75+ a lot because the old 12A cars had a weird kind of "coming on plane" effect where because of the way the ignition timing and carburetor sizing and aerodynamic loads and gearing come together, it takes less throttle to cruise at 75 than at 65, engine is quieter, etc. So we will call that an outlier.
It is also far more pleasant to drive than the bridge ported monster. You can drive it like a normal car because it IS one. I put about 8000 miles on it this year vs. only about 1000-1500 on the other RX-7. And about 40k on the Volvo.
Great point about the gearing and 5th gear. I constantly have that in the back of my mind, only a 5 speed where a 6 speed would be nice. Something Ill look at down the road.
12-08-22, 07:58 PM
