What options do GSL-SE owners have to reduce the compression ratio in their 13b's? Do older 4-port RX3's or Cosmo's have lower compression rotors, and if so could they be used in the stock SE's rotor housings? Can the "tubs" be machined on the rotors for a deeper or wider depression to reduce the compression ratio, and if so what's the limit? I plan on turbocharging my 13b and using 12a side housings for an agressive street port, but I'd like to have a lower compression ratio for a better chance of eliminating detonation and longer engine life. I guess I could live with the stock 9.5:1 CR and run an MSD Boost controller and 6AL to retard the timing under boost, and possibly run a water/methanol injection system to help cool down temps and keep combustion pressures down but I'd rather run a CR closer to 8:1 so I can turn up the boost without fear of the amazing grenading rotary. Do I have any options or will I have to live with fear? Thanks to all who reply for your time, help, and info...

-Adam Collins

 

S5 (89-91) turbo and 3rd gen twin turbo engines came with 9.0 CR. You can always get the rotors and counterweights for an S5 to acheive a lower static CR. Another advantage to the S5 rotors, they're about 1.5-2LBS lighter/each.
The GSL-SE and older 13B rotors are in the 11.5LB range, while the S5 rotors are in the 9.5LB range.
Don't take my word for it, check it out here: http://mazdatrix.com/faq/rotorwgt.htm

 

Old-school 13Bs all had 9.2:1 compression ratios, if I remember correctly.

 

If you're going forced induction, find a pair of TII rotors. If staying NA, go with the S5 NA rotors, along with a lightweight flywheel and matching counter weights.

 

sell your SE rotors and get some T2 rotors.

 

I thought that S4 and newer rotors wouldn't work with 1st gen side housings. Something about a seal that was moved from the 1st gen rotors into the sides on the later engines, and that you're not supposed to interchange later model rotors into 1st gen housings because of different geometry isn't it? I may be assuming this, but I was told that the side housings from a later model engine wouldn't work on the SE's 13b. I also think it was RB's Technical manual/product catalog that said the combustion chamber geometry was different between 1st gens and 2nd and 3rd gens. Would I have to use S4 or newer side housings, rotors, and rotor housings? Or could I just get away with the rotors?

I was planning on running 12a sides, how would (or could) this work with the S5 rotors? Thanks to all for your time and help...

Oh yea-thanks for enlightening me, percent. I believe I was thinking of the 12a's when I mentioned the 9.5:1 compression ratio...

 

that is what is said, but people use newer rotating assemblies in older engines all the time and i have yet to see case of a fucked up motor based on different peritrochoids. not to say it's never happened, but ...

you are correct. you cannot use pre-'86 housings with '86+ housings - at least, not without modifications that are not worth it for street use, in my opinion.

stock compressions that i am aware of are: 8.5:1, 9.0:1, 9.2:1, 9.4:1, 9.7:1 and 10.0:1 in the varying engines over the years. outside of that i think i've read of some weird different compression rotors that were purpose-built - not for general consumption.

i still say if you're not going to just get a T2 motor and build it to use in your car, then the simplest thing is just build your 6-port with T2 rotors make it a little more boost friendly.

 

Well, the TII or REW may come later but I've got this 13b right now and would like to use most of the parts (engine components) I already have if at all possible. The TII rotor swap sounds doable for my project, with the lighter rotors and (slightly) lower compression ratios. I'll have to check the forums and see what I can expect to pay for a good used set. I'm almost ready to have a reputable shop build me my first 13b, just a few more items to gather for my suspension and a set of 12a side housings to port.

The TII rotors will work with 12a sides, won't they-as long as they're in an SE's 13b rotor housings? I don't plan on hooking up the factory 6-port intake manifold to a back-pressure sensing tube in the exhaust stream, and RB's manual recommended against porting the 6-port sides (said no significant power gains were found and no templates made). I'm shooting for right around 300HP with a properly sized turbo with the '84 13b. I'm not going racing with this car, so as long as my powerband stays in a good (mostly) streetable range I think I'd be happy with even less. I'll worry about more power down the road when I'm building my next 13b.

If anybody has any more info on the subject, especially if one of you guys are running TII rotors in your SE housings now or have in the past-please let me know how it worked out for you and if there's anything to consider or any precautions I should take before I start looking for a used TII rotating assembly. Thanks again for everybody's time and help!

-Adam Collins

 

why not boost NA rotors? as long as youre not wanting the absolute highest numbers you can and watch your tuning, youd be fine. the car would be more responsive as well.

 

Boost your current engine as is. The car will feel great.

Keep the 6 port actuators, and feed them thru BOOST instead of exhaust. (You will need a small valve to limit the actuators to receive only to 3-5 PSI )

You will have a stock looking, TORQUE Animal. Yes, TORQUE. It will be amazing to drive at the <300 or less HP levels.

More than that, and the 6 port system will become a bottleneck.

I have seen, driven, and experienced this setup. It is what made me fall in love with Turbo FB's 15 years ago. Nothing like going sideways at 70 mph by doing nothing more than stepping on it (not even downshifting)

 

Directfreak-not a bad idea. I've got most of the parts, but I plan on having the engine rebuild-or at least refreshed for now depending on how bad it looks once it's apart. How much boost psi would be required to push the stock 6-port intake set-up to right around or barely under 300hp? Would 9.0:1 compression S5 TII rotors be compatable with an otherwise basically stock SE 13b? What kind of ECU mods would be required to retain the stock ECU? I had planned on going a bit more flashy with the parts selection, but I'd like to read up on a similar set-up-this could save me a lot of money if I can see the power levels I'm shooting for. Who else has a turbo'ed stock intake SE? Thanks!

Oh-percentsevenc-Mazdatrix's website states the '84-'85 SE's comp ratio is 9.4:1, while the early 4-port 13b's was 9.2:1. I'll probably use TII rotors if they'll work correctly for me.

 

not for nothin', but ... this should have been stated in your original post. this contains all the pertinent information for me (or anyone else) to offer advice without just pissing in the dark.

have the motor streetported and put together. i'll be the third to agree on using the stock rotors. parts are important, but you won't NEED lower compression. after your engine is build, your focus should be on engine management. period.

you'll be best served if you look around the board and see for yourself the merits of porting and the fact that higher compression in itself does not kill motors.

 

You won't even come close to 300 hp on the stock ecu, Even if you converted the intake and ecu to a TII system you would only hit about 230 with other mods. 300 hp is standalone territory with FI and a turbo. If that's your goal, start with a TII setup now and save time and cash.

 

Keep the Stock Rotors, they are already 3MM rotors.
Upgrade to a 2nd Gen NA Intake (or keep yours)
Keep Stock ECU.
Add two secondary injectors.
Get Boost Dependent AIC (Additional Injector Controller for the new injectors)
Lock your Timing.
Tune Safely.
Enjoy.

See Web777's car here on the forum. I haven't seen him post in a while but he has a similar setup to what I described. Moves VERY nicely.

300whp on that setup with a nice little 60-1 Turbo should be 12-14 psi or less.

 

damn DF, youre making me want to rethink my bastardly swap...

 

Diabolical-sorry man, I didn't realize that I didn't include that information until later. I had started another thread and replied to another one or two around the same time with all that information and I must've gotten confused. I didn't want to repeat any information in the same thread. What would you do-keep the 6-port intake and rotary valves or go with 12a sides? Who would you recommend to streetport the 6-port plates if that's your recommendation? I didn't think that many people/companies had much luck porting the '84-'92 NA 13b plates (I know RB didn't-maybe I just assumed others didn't too). I've planned on an agressive street port from the get-go (I might've forgotten to include that info in this thread, too), but the original plan was to use the 12a irons because I thought I could squeeze more power out of them with an agressive street port then I could with the 6-port plates.

Trochoid-Do you disagree with DirectFreak? Should I run an aftermarket EFI, and which one would you run if so? What side housings would you choose for my HP goal? Could I get more power from the street ported 12a sides then the stock SE pieces?

I like DirectFreak's idea, if I can reach my goal that way. I planned on using an aftermarket fuel and ignition system from the start, and the more I research the more I'm leaning toward a completely assembled Megasquirt. I'd like a Haltech, but I'd have to save for another month or two for that. I'm going to weigh my options a bit more before I spend my $ on any type of EFI system, but which ones would any of you choose, and why? What are the biggest pros/cons in each that specifically relate to rotaries? And what type of ignition system benefits that would work with rotaries does each have? I don't plan on powering my plugs with the distributor anymore after upgrading the EFI, but I still don't quite grasp the rotary's stock ignition system yet either and all the technical lingo on the EFI system manufacturer's website confuses me when they brag about the ignition system capabilities. Thanks again for everyone's help!

-Adam Collins

 

When it comes to 'HowTo' make power, I won't argue with DF, lol. He's been there, done that. My preference would be a 13B 4-port engine with MS when shooting for over 250 hp.

 

i do my own porting so i wouldn't know who to recommend. i think Rotary Resurrection is fairly close, so you check his site or contact him on that matter. i don't know him, so this is totally based on his forum personality. he seems pretty knowlegable and decent in terms of ethics. i'll leave it there. check your local area on the board for locals. the closer you can keep your parts to you, the better.

i don't particularly like the 6-port configuration, so i usually convert to 4-port or do the siamese-thing - but that's my perosnal taste. that said, there have been quite a few streetport success stories for 6-port motors around the board. it's only when you introduce bridgeports that i see questionable results on the 6's. as for me, i can't see myself ever building a stockport motor for myself ever again. so i definitely say get a streetport. i'd be more than happy to share thoughts with you.

as for your particular situation, i know how i would go about it, but there are too many ways to skin this cat. so for you, my advice would be not to force the 4-port issue. you'll have to seek out an intake and a few other little things that probably won't matter much in terms of drivability and reliability - so it'll just cause delay and a few extra dollars. i believe Directfreak is a very credible source and you can follow his advice/blueprint and get the results you want, while keeping premium reliability and minimal delay and frustration.

finally, about your EMS, get whatever the person who will be tuning your car is familiar with. it's much better to have a great tune with a mediocre system than it is to have a shitty tune on a great system.

 

Diabolical1-what's the "siamese thing"? I'm not familiar with that term-I have an idea or two what it could be, but I'm not sure.

I really want to thank each and every one of you guys that have replied to my questions and PM's. This forum and it's members have helped keep me from making many mistakes, pointed out new parts and suppliers, and kept my interest in my '7 a top priority (after my son and job, of course). Everybody I've dealt with has been extremely helpful and friendly, and I'm more grateful for that than anybody could imagine. Because of that, I've got a pile of parts that I'm confident are the right parts for my application, well-95% sure. The other 5% was my own stupidity and impulse buying. I just want everyone to know that their advice IS appreciated. Now I just need the time to work on it...

I believe I'll stick mostly with DF's advice. I want to at least refresh the SE's engine if it checks out OK and have a large street port performed before any boost is added. I'll build this engine if I can get by without buying new rotor housings, but this will definately not be this car's last engine. I want to enjoy the suspension system I'm building on this car ASAP, and it'll cost me less money and time to build the engine I have. I'll get by on this set up while I save up for a bigger and better build. I don't really see it as wasting money, I see it more like gaining experience with rotary engines, engine management systems, and turbos. My performance background is littered with words such as "carbed", "naturally aspirated", and "valvetrain". This experience is worth more to me than the cost of a rebuilt rotary engine. Maybe I'll even be confident enough to build the next on myself. Once again guys, thanks for all your help...

-Adam Collins

 

Thank you for being patient and actually paying attention. That's what I love about the 1st gen section over the entire club. We are all family here, and we are all looking out for each other.

Please don't take my advise as Gospel, as Diabolical said, there are many ways to do what you want.

I have learned the hard way that you should build your system based on your horsepower goals. That way you don't buy parts you won't need, a turbo that's too big, an exhaust that's too restrictive, an ECU that's too crappy, etc.

My advice was based off a 300whp goal, (which is plenty) and will be a nice powerful, and reliable daily driver if need be, while saving you a large amount of money.

If later you decide you want 400HP or more, then you would have to re-do the entire system/engine combo.

If your end goal is 500+HP, then I would have pointed you in another direction entirely.

Those of you with E85 fuel avaliable to you could now probably do draw-Thru Turbo setups AND run higher boost/power combinations without the previous risk of detonation. Even without any kind of water or alcohol injection.

Lots of variables, Lots of combinations, many way to get the same goal. The amount spent can vary alot, just as the amount of boost needed can vary.

Good Luck.

Good Luck and keep reading/searching/learning before you attempt a swap, or to turbocharge your current ride.

 

it's when you basically turn a 6-port into 4 by combining the secondary and auxiliary ports on the front and rear side housings.

that's the smart move.

 

You'll do perfectly fine on the stock SE rotors and 6 port engine up to about 350-400hp with proper tuning. There is a guy that lives not too far from me named Aaron Cake, one of the smartest when it comes to turbocharging the 6-port NA engines. I don't know everything about his current setup, but AFAIK he is looking for around 450hp on a half bridge turbo 6 port S4 with NA rotors. Search for him on the forums. He's also got a website for the basics of turboing a 13B NA. It focuses mostly on the 2nd gen, but its good info. http://www.aaroncake.net/RX-7/mods.htm

 

Directfreak, you're making me want to boost my FB and it's not even running well!

 

i know he doesnt need backed up or anything but just check out this vid...its so sick!

 

o yeah thats also on my myspace....everytime i hear the engine in high rev i think its going to kill somthing!