I've got a buddy putting a Renesis in an 1984 RX-7 GSL-SE (brand new engine with 3mm Apex seals, 6 speed tranny, & custom made carbon fiber drive shaft)

It sounded like an interesting project ... was wondering if anyone else here had done or heard of something similar, and opinions of how something like this might turn out

Jeff

 

why?

 

Sounds great. With some porting and appropriate alternator etc, and a standalone ems, rev that sucker to 11 or 12k rpm

 

cause its more pwerful than the engine he had and less money than getting a whole new car. plus the job of doing it sounds like alot of fun. tell him to get it ported while its apart for the apex seals. whats he using for engine management? probably a motec right?

 

well the engine cant breathe much past 9500 anyway. in this situation if you wanted to increase the revs you'd need more air which would mean a whole new intake manifold. actually come to think of it- is he just getting a bare block or is it fully dressed? without everything to run the SDAIS (the elctronic and vacuum "switches") how would you "tune" the airflow to make the same power as it is in the rx8? interesting project....

 

lol exactly my thought.

 

hrm, good point

238hp (maybe 250 with the stand alone) in a car that weighs ~2600lbs, and doing it naturally aspirated with good drivability, which couldn't be done with the stock engine perhaps?

 

well he is going with the 3mm seals...that somewhat of an improvement isn't it. just changes the compression a little bit i beleive...i might be wrong though.

 

Interesting conversion......... old school ride meets new school technology........

 

the stock 8 has a carbon fiber drive shaft...you are refering to that right?

 

I've heard about someone swapping in a 13B-MSP into an older RX-7. It'll work, but there are some things that need to solved internally. Don't you have to clearance the engine a bit to allow 3mm apex seals? Also, what type of material are you looking into? Cast iron, or exotic ceramic? I think it would be a neat project that I would love to get involved with. I wonder how much better the engine would perform if you coated the rotors with Cermet.

As for the transmission, why not try to get away in a TII transmission? Maybe the gearing might be better suited for the RX-7, but I'm not sure.

As for Chuck's concern, eliminating the S-DAIS would pose a power delivery problem, since they're tuned to run at certain engine speeds. I was given the idea a few months ago about using a longer intake runner if you're going to work with forced induction, so perhaps a short one might be in order. I'm not sure. Keep this thread open for the next few months, because I'm going to pick up some serious stuff when I start taking fluid mechanics. :D

 

LOL - I seemed to have started something here! When I showed my buddy the responses here, it definitely got his attention!

Before he can get around to register or log in here himslef, he gave me something to post on his behalf (he's got his hands full right now with stuff)

(I hope posting for a friend won't break any forum rules, and I'm only going to do this for him once :D )
Jeff

 

aren't there a ton of mods available for that car that would be less expensie to mod and old engine over a new Renesis?

 

^ and keep it NA? no not really.

 

what, don't tell me you're actually against having a 4,000rpm idle?? Don't worry, once your eardrums rupture from revving up the engine a few times you won't even notice it anymore!

 

Haha, modded roatries for drag racing have to be some of the most wretched sounding cars ever.

 

it's been done already, I saw one somewhere, they even used the RX-8 gauge cluster

one question, why 3 mm apex seals? They don't seal as well, they are not very fond of high revs and don't provide any advantage on naturally aspirated cars. Some even argue if they provide any benefit on boosted rotaries as they'll break the same with a good knock. There are many high boost cars with 2-mm seals, it's all in the tuning.

 

Also consider one of the things that makes the NA 13B-MSP's hp rating around 238 +/- is all the arcane engine electronics. The Apex'i SuperAFC alone will not help you control the complex intake system, to say the least. Unless yo go with a standalone ECU that has a good handful of switched and pulse-width outputs to control all those extra solenoids, you're going to have to acquire the RX-8's actual ecu, wiring loom, sensors, etc.etc.etc. Even then it might be a labour of love just trying to get it all to work correctly.
Otherwise, if you're just using the MSP block with a custom cable / throttle body assembly or an intake manifold from the earlier rotaries, your end result probably won't be significantly better than that of using a standard 13B.

 

I think there will be big improvements anyway just based on the port timing differences