Azriel_Strife

iTrader: (5)

I have an 1985 RX-7 GS, she goes good, but i want more on the ground..

Anyone know what i can install to get me over the 200HP mark? i need a good intake, but im carbed..

any input would be much appreciated..

thanks..

Glazedham42

iTrader: (4)

I hate to be the one to break this to you, but you're not going to hit 200 ponies with a different intake. For that matter, you aren't going to hit 200 with ANY amount of bolt ons. The higest you can get a 12A without porting or turbo or anything extravagant is about 150 hp. To hit that mark I would recommend a number of things:

1) Ditch the stock clutch fan and get yourself and electric fan to replace it. This has been rumored to free up anywhere between 10-15 hp. I'm not sure if anyone has actually dyno'd to prove the results ever, but the increase is significant.

2) If possible, take off all your emmissions junk, such as: air pump, hot and cold start assists, butterfly inside your intake manny. I would also recommend removing the rats nest for simplicity's sake. It will clear up a lot of potential problems. There is a tutorial for the rats nest removal on here if you look for it. Do a search.

3) Remove all your air conditioning components. You aren't going to gain any horsepower but you will be saving LOTS of weight. You'll understand why if you take it out. All the air conditioning equipment adds up. Most of it weighs quite a bit. Dropping weight is a great way to increase the effectiveness of your existing power.

4) Racing beat exhaust. The mother of all rotary exhaust systems. You can't beat this exhaust no matter what. I don't care what else you bring to the table, the RB system has it beat. It will yield a NICE horsepower gain. You'd be looking at about 20-30 hp just from this mod alone. I can't remember the actual increase the RB claims, but it is substantial.

Those are just a few things you might want to look into. If you are really going to try and hit 200 hp you need to do some serious searching of the forum here. Bolt ons aren't gonna cut it bro. Especially not just an intake. Your car only has about 100 hp from the factory. Your going to have to do a nice port job on the engine or start looking to turbo the engine or supercharge it to hit that level.

rotarymike

iTrader: (1)

It is essentially impossible to double the power of your car through bolt-ons, like an intake

If you REALLY want 200ish, find a J-spec engine importer and have a series 5 turbo engine installed. It's not cheap though, whether you do it or pay to have it done.

As light as a 1st gen is, the 160 HP or so from a stock 1989-1991 6-port NA 13B engine makes for an extremely quick car, while still being eminently streetable. You would be surprised how many 300+ HP cars (Z28s, etc) you can run down since you have 1000 less punds of weight.

Simple mods to increase power are listed in the post above. Essentially, put a good exhaust on there will get you <italics> maybe </italics> 125 HP, the rest of the mods minimize the HP wasted on other stuff, like spinning a fan or moving unnecessary weight.

If speed is all that's important, save your $ and buy a 89+ turbo II. Not being a smarta$$, just the truth. If it's more important than that, buy a 3rd gen or RX-8.

nevarmore

Its all about power to weight. Just to reiterate what RotaryMike and GlazedHam said here are some rough numbers:

100hp@2200lbs::22lbs/hp, stockish FB
100hp@2000lbs::20lbs/hp, stockish FB but dump some weight.
110hp@2200lbs::20lbs/hp, no emissions, OK exhaust

120hp@2200lbs::18.lbs/hp, stock body + interior FB w/ good exhaust and no emissions
120hp@2000lbs::16.6lbs/hp, dump the A/C and maybe a lighter hood or lighter wheels
170hp@2200lbs::12.9lbs/hp, Streetport
170hp@2000lbs::11.7lbs/hp, Streetport and a diet

I work better with numbers. This helped me figure out how to make my cars faster more than thinking about it in words. Yes, I know these numbers are a bit offm.

The first section is the best, you can cut weight from the car (nearly free) or spend cash on a mid-grade exhaust and end up at the same place. Cutting weight from the car includes the driver. I weigh 150lbs soaking wet after eating, there is a noticable difference in times between my car and when the guy I learned to drive from who weighs in at about 185.

Anyhow, I know that was redundant, but I had to offer up my two cents.

Azriel_Strife

iTrader: (5)

i thought i was making 146 stock... 12A rotary on has 100 horses?

thats kinda weak, even if i am really light..

anyway.. i wanna do my exhaust, and put on a slammin intake, but i wanna keep carbs, and original parts...

hit me back..

PE@CE

Glazedham42

iTrader: (4)

Well... my best advice to you would be to go here: www.racingbeat.com and start spending. All of their products are top notch. They are the #1 in rotary aftermarket performance. However, that doesn't mean they have the best prices on everything. You can find lots of their products used if you are patient. But for the most part I would just start by getting the basic RB bolt on pieces. Exhaust, intake, etc.

rotarymike

iTrader: (1)

13B in the 1st gen has ~135 HP. 13B in the 1986-1988 RX-7 has 146.

12A in latest form (1985 1st gen) had 101 HP.

Weak? from a 1.1 liter? ha!

exhaust is a must. even if you just rod out your 1st two cat converters, so *something*.

There is no such thing as a slammin intake on a carburetted car. There is only 1 carburettor, an expecially small Nikki 4-barrel (essentially a scaled down holley with vacuum secondaries). You can spend several hundred on a K&N filtercharger with the filter in the lid as well, but it still won't make more power. If you stick a straw into a small soda, you can suck x amount of soda per minute. If you put the same straw in a large soda, there is more soda to suck, but you can still only suck x amount of soda per minute. Replace soda with air, and the straw with the carb, and you'll have the picture.

For power, you can go to EFI on the 12A motor. But still, I'd think 135 would be about it without porting and exhaust.

MikeH

Azriel_Strife

iTrader: (5)

yeah, i get your picture..

By rodding out my Cats.. does that mean shoving a piece of rebar through it?

i kindof want to keep my emissions equipment on it.. cuz im in an area where we still have emissions control.. (Lower Mainland, BC Canada)

Also, what about getting a bigger "straw" so to speak, ive heard i can get bigger carbs to mount on that engine.. If this is possible, lemme know what will fit..

so if i get 1 oversized Cat from say, a small V8, and put 2 inch pip from there back.. thatll score me the flow i need, i think..

I've heard that rotary engines need backpressure, or they blow.. but they have no valves to float, no pistons to break, hardly any recipricating mass at all..

so is backpressure an issue?

feedback much appreciated..

rotarymike

iTrader: (1)

There are 3 cats in the exhaust stream. Only the rear-most one has anything to do with tailpipe emissions (as far as a yearly emissions test is concerned). So if the first two are hollow, you'll have more flow. You may find they are hollow already... one of the '85s I owned the innards of the 2 first cats were jammed into the inlet of the third

Bigger carb = lower torque. Unless you drag race ONLY, and don't mind a 2000 RPM idle stay away from the holley kits.

Try to suck soda through straw, you get X amount of soda. Try to suck soda through a 3" pipe, get nothing

Rotary engines need a small amount of backpressure for atomization of the fuel and such. But in general the less backpressure, the more power. It's really hard to blow a 12A motor unless it has a ton of miles on it, then it may blow at any time at all. You never know. One of mine chucked an apex seal at idle. Another had 170K on it and still ran strong, but leaked water internally... YMMV.

Why the reluctance to go to EFI?

MikeH

Azriel_Strife

iTrader: (5)

isn't it a huge job to install an EFi kit?

installinf a carb and manifild is easy.. but i tink itll take alot of work to intergrate EFi into a carburated car..

wont it involve new wire harnesses and such?

if not.. if you could give me a quick run down on what is required.. that would be awesome..

thanx

PEACE

Glazedham42

iTrader: (4)

Why is it a requirement that you switch over to fuel injection? You can easily make 200 hp being carbed. There is no real reason to switch over to FI. You'll probably end up spending most of your money trying to do the swap and in the end you'll just have a messy FI system that needs lots of work. I would stay with the simplicity of the carb and spend your money on proven power like a port job, or a turbo setup....

rotarymike

iTrader: (1)

Different strokes for different folks. I grew up with EFI, so I'm more comfortable installing and tuning it. I'm also a professional avionics tech, so that mayhave somethingto do with it. Carbs to me are a pain to tune correctly and still don't work as well.

With EFI, at least on a rotary, you can lengthen the inlet tract to increase torque (which rotaries don't have much of) without affecting fuel requirements or design much. And, all tha parts are right there... the GSL-SE has all the hard to find parts like fuel pump and intake maifolds etc. that can be adapted to a 12A without a huge mess.

Also, blow-through turbos are just a huge mistake. No way to completely control the fuel flow. For driveability, I've never seen a blow-through setup that worked worth a damn. For absolute power, sure, but then again you're building a drag only car.

Port job, hell yes. But with rebuild costs, vs. EFI costs, vs. a used 13B EFI motor, harness, and ECU, you'll get more power that you can use through the swap.

I have yet to see a 200HP 12A that wasn't in a formula Mazda type car, that would hold an idle or drive sedately. He said he needs to pass emissions too... that is something that won't happen with ports big enough to support 200.

rotarymike

iTrader: (1)

BTW, for cheap efi...

http://www.bgsoflex.com/megasquirt.html

it does work, and work well.

Mike

rxtasy3

iTrader: (2)

what are you talking about. bridge port engines idle at 2k. my streetport 13b idles around 1k and on a stock port, a holley will idle less than that. if fuel economy is an issue, go with a holley, in my experience the get better gas mileage than any of those big 2bbl carbs and still have the same power at wot.

i take it your using this system? i've really considered trying this.

efi12a

I can vouch for that. I'm using it on a street port 12A with a good exhaust, 2x50mm DCOEpattern TBs; the best power yet was 167@7500 (and still climbing, I chickened out of revving higher). Just as sedate as a stocker carbed unit too.

-Mike II

rotarymike

iTrader: (1)

Yeah, I'm using it. (the MegaSquirt)

Give me a day or so to put the pics into the content management on my site, and I'll post it here.

But in short, I used a GM TBI unit from a 4.3liter V6 and a homemade adapter to mount it onto the bottom slice of carb (so I could valve the secondaries) and then the stock 1985 manifold. Idled nicely at 600. With the carb, even after a pro rebuild, I had to keep my boot in it to get to 85 mph. With injection, I got a ticket for 90 in a 70

Motor threw an apex seal at 184k miles... so I reengineered the system to make it a little easier to find parts for, and less dependant on non-mazda hardware (ie stuff I can't buy ffrom MazdaComp). So the motor is now a mildly streetported 6-port 12A (GSL-SE housings, 12A rotor housings and spinny bits) and I'm building a custom lower intake manifold to bolt on the upper half of a 1991 intake, throttle body, etc.

The 'squirt rocks BTW - after install, took me about 2 hours to get a nice smooth idle and OK throttle response.

As for the high idle on a rotary with holley, my only experience has been drag cars with the RB manifold and a modest holley carb, and they wouldn't idle below 2k worth a darn.

rxtasy3

iTrader: (2)

all the drag rotarys i've read about are running bridgeport engines and yes they don't idle below 2k reguardless if it's using a 4bbl holley or any of the big 2bbl carbs. but there's nothing like sitting beside someone at a stop light, brap,brap,brap,brap. but back to the efi, i had thought about using one of the 4bbl throttle bodies that came on the mid 80's GM trucks.

FB II

i have posted this before but, 12a's have put down over 150 rwhp on stock ports using a carb. you MUST TUNE and whatever carb you are using needs to handle atleast 425cfm or so and be FULLY ADJUSTABLE. not just jet changing. read in on paul yaws site. you people don't give enough credit to the stockport 12a or carb capabilities. and blow-thru carb setups not being worthwile and only making big power for drag only? well then obviously you dont read the 1st gen section of this very forum. there are about 4 or 5 that have just gotten on the road with theres and waaay too many that have been around and theres more everday! hmmm great drivability. great power, idle just fine... people have been doing this FOR YEEAAAAARS!!! you just have to know what the hell you are doing. i honestly have thought about F.I.... especially the MS setup. but i dont see it being worth it anymore. someone made 167rwhp on the MS setup with a STREETPORT. paul yaw makes 154rwhp on STOCK PORT CARBED. i'm sorry for this rambling, but it just bothers me when people bash what they do not understand.

rotarymike

iTrader: (1)

Wow, anger. :-o Did we hit a sensitive spot?

FB II, you need to read the initial posts and reply in context. Azriel_Strife wanted to hit 200 hp with HIS carb with an EMISSIONS LEGAL car. And didn't really know much about the FB yet... not a dis to him, but everyone starts somewhere.

I spent about $120 on my megasquirt, $25 on the injection parts, and traded an hour or so of labor for the GSL-SE parts. (actually, a whole car's running gear). I think, that for the money, EFI is better than a YawPower carb. I've driven a car with his carb (IT7 1st gen) and I will admit that the WAY modified carb makes good power on a stock port, WITH AN OPEN EXHAUST. Hell, I was trying to get one of his spiffy headers before he switched to RX-8 stuff.

Blow through turbo without problems? I've never seen one. I've always heard the horror stories of people trying to tune them (true, not with RX-7s, but another finicky foreign sports car) and how they constantly need adjustment. Plus, to go to a decent carb, you're spending $ on a manifold, FPR, redoing fuel plumbing and wiring, etc etc I don't see it as any harder or easier than a simple fuel-only EFI.

You're right, I don't read the 1st gen section too much, because I have other **** to do... I pick a few forums I'm interested in and read those. Just like pretty much anyone who has a life :-P

167 on a streetport... what exhaust? Streetable? Who did the porting? What have his ported motors dyno'd at with carbs before this? Was the car tuned on a dyno (i.e., properly) or just drive-tuned? What injection setup was he using? I *know* Paul uses a dyno and fine-tunes to the nth degree.

When I say the RX-7 sucks ***, is unreliable, and not nearly fast enough to be considered a 'real' import like a Honda Civic with a Weapon-R intake kit and some stickers, THAT's bashing. <sarcasm off> You will note I did not do that. I said the cars I had experience with that had aftermarket carbs were drag cars and wouldn't idle. I also said that MY car performed such-and-such before and after the EFI mod, which in absence of timeslips or other dickwagging proof is pretty objectve.

I stand by my guns. EFI is better than carbs, ceteris paribus (all else being equal). Tuning and support equipment make a LOT of difference; a good carb setup will work better than a crappy EFI setup, sure. But a properly tuned EFI setup will result in more power across the power curve, with greater part-throttle driveability, easier starting, more adaptability to differing driving conditions, and better control over emissions (should one want that). There is a reason OEMs all went to EFI, and it WASN"T price.

Ok, rant done.

rxtasy3, to use a 4bbl TBI you will need to carefully match fuel flow of the injectors you choose, or you won't have very good idle mixture control. It would make the physical mounting much easier though I wanted to use the lower slice of a Nikki to valve the secondaries... primary plates removed, walls between ports milled out primary to secondary. Started using a stock vac solenoid to pull the secondaries open, ended using a hot-start motor to open them on command from the 'Squirt. (pretty easy to add in an RPM based switch in the code).

One of the guys at Charleston AFB has an extreme street port or bridge port 1st gen, painted newly red, nice condition... was REALLY nice to hear it lope by But by the same token, nothing sounds quite like a Porsche air cooled 12 either... so on and so forth. While *I* may not be an ideal person to ask this question of, the average Joe wouldn't drive a 962 or 917 on the street or expect it to pass emissions (big LOL).

FB II

hey, i apologize for coming off so angry. i wasn't... just bothered a bit. that 167rwhp was with a streetported 12a using the megasquirt setup. i was using that as comparison to pauls stockport carbed making almost the same power. and it was a street car, not race. so it did have a full exhaust and muffler. as i did say i looked in to going fuel injected, but the only setup i could see being pretty good was using TWM dcoe throttle body with dual injectors, then the ms unit, sensors (including xbar map sensor for boost), wouldnt be able to use tps because of bog. actually now that i think about it i would need 4 injectors in a dual stage setup. the price of the ms unit alone with some basic stuff is cheap no doubt. you can also probably find a laptop pretty cheap, but that still adds in to the equasion since they do not yet have the msviewer thing. hahaha, whatever you call it. eventually i may still have to try this yet as with weber carbs you max out around 500 hp and i'm on a rampage for power. the only serious benefit i see to this is gas mileage, but i knew getting in to the rotary scene that wasn't a perk. if you could list me a setup using gsl-se or whatever parts that would work on a turbo 12a setup efficiently i am all ears (or eyes rather) haha. i am very very open. i just don't like it when people bash the blow-thru carb setups.



EDIT!!! hey, i just noticed you are also in NC. i'm about 2 hours away (actually less if going fast enough)... maybe you could hit up a meet here or if there is one there. i would like to get together and swap ideas or hell, even learn more about your efi stuff. WOOT!

rotarymike

iTrader: (1)

I think I'll be at the MSCCNC meeting on Friday in Durham. Otherwise, it will be a few weekends before I am free... otherwise, hell yeah. Do you know where Victory Lane karting is? Some friends and I go down to run every once in a while

Let me know more about your setup with the 12AT... I am going to be running the dual-table code as well (basically using a 1991 intake manifold on my 12A). I have DT code modified to also output 6-port and VDI at adjustable RPMs.

680RWHP12A

the bottom line is dollar for dollar, a good carburated setup will win hands down over efi, anyday!!
carbs are more user friendly(almost anybody can tune one easily), with good results
the only advantage with an aftermarket efi system is it is more fine- tuneable, if you know how!!! fine tuning efi is very difficut as there is way more adjustments....

i know a few efi tuners that have customers that fly them around the u.s. to the various tracks they race at to fine tune the efi setups!! they pay big $$$!!!

the guys that race with holley, or weber setups can make simple jet changes themselvs, saving thousands of dollars(but missing maybe 20 to 40 hp over the efi guys)...

its all about the money, unfortinatly, and im all about saving it!!! so my vote is for carburated for all around use....(performance & dollar value)

also on another note, a typical dellorto or weber setup makes 40 xtra hp over stock se fuel injection!!! thats just one example!!
alot of stock efi systems are replaced by aftermarket carburators in favor of increased horsepower!!!


also there is a all motor honda running dual weber carbs and he is in the top 3 fastest all motor cars!!! thats not bad for ca carb setup, is it? he saved thousands of dollars and is very competitive!!!
thats it im sick of typing

FB II

you talking about the victory lane kart place that is right off 77 going on to 85?? if so, then that place rox! HAHAHA fug yea, lemme know if it is. 680rwhp is the guy i pretty much get all my stuff from. he's friggin amazing and especially with carbs. he's messed with both that and efi, and infact ran a nice efi setup on his drag car making i think 720 or 730rwhp. one of those two. so, don't get too mad at him for loving carbs tho. we really should get up sometime. i've been wanting to go to one of the msccnc meets, but i never get the right day off. arg.

rotarymike

iTrader: (1)

It's how you approach tuning. Using a vacuum or air speed thingy to tune multiple carbs is an art, not a science. Too many people are afraid of EFI I think.

I'll disagree with you on that one... I spent at least $400 making my stock 12A stock but functioning to have someone rebuild the carb, eventually buy another carb, and all the tuning issues. I spent *maybe* $300 on the EFI setup.

Well, the 1989-1991 EFI 13B makes 25hp more than the -SE (160 v. 135) and it's still a stock system, designed for emissions compliance and fuel economy. The dellorto/weber conversions make decent power. I'd like to know what the few people who have installed MS EFI computers into their 2nd gens are getting power wise, if it's been tuned properly.

MikeH

rotarymike

iTrader: (1)

Yeah, right after 77 and 85 meet. When I go down there next to get my kart on I'll drop you a line.

MSCCNC meets are a ways off for me too... most of them are in Durham, about an hour for me. I go when I can because I feel I should (hell, I started the group in '99) but that doesn't always happen... I know what you mean about days off etc. Heck, with school and converting back to being a civilian I haven't had time to play with my toys... I worked on my Jeep a few days ago and it was the first time I'd turned a wrench in earnest since coming back. Especially frustrating since I have a nice, new milling machine set up in my shop space, and the AL plate for the intake manifold, but haven't had the time to carve it out.

Too many projects. Turbovert, 90 T2, 85 GSL-S. I think I can whip out the turbovert if I can come up with $1500 or so for the parts car and rebuild kit. The T2 I need to purify myself for a week or two, sterilize the stall and make a Class III clean room to build the motor in, while chanting and sacrificing pistons. The FB just needs an intake manifold...

MikeH