999miki

I really hope that many was lost in translation

Compression ratio, is just, ratio, it tells nothing about dynamic compression and that is important.

Shorter apex seals??

I really canīt imagine how lighter apex seal could be detrimental for boosted aplication

Side seals more outwards??

I really donīt see problem here

Only thing that could limit power output - internal flow of Renesis, are exhaust ports and structural strength of engine

ilikecars

sorry to bring up this old thread but i had a question that ill probably get flamed for. if the big issue here is detonation, then why not meth inject? this would raise the octane level and it burns colder than gasoline. kits are fairly cheap and tuning shouldnt be too hard. the injection would also cool the air charge (depending where the injector goes) which should help performance. is this valid at all or am i retarded? personally, i think this is an obvious solution for no one to have mentioned it so im guessing theres something wrong?

longpath

iTrader: (1)

I don't know if there is enough material in the housings to extend the intake ports this much (into the compression "stroke") but I would be interested in seeing this approach explored, if only to keep the expansion ratio at 10:1 and not having to enlarge the combustion chamber, reducing efficiency when you aren't at wide open throttle.

Does anyone with significant experience porting the Renesis know if there is enough metal in the housings to implement a Miller cycle late closing of the intake ports without running into the coolant jackets?

Roen

If anything, I stopped by Dave's last week at Speed 1 with the exact same questions. He gave me the exact same response. Combustion pressures are the key, even after I asked him if water / meth would be a good solution to combat this.

In his words, and I QUOTE: "A half point increase in compression ratio will lead to an almost doubling of combustion pressure."

His advice was use a Greddy and leave it as stock, or use a Turblown and keep it in the neighborhood of 300. He says at 350, the engines just don't last. His joke was that the best way to make power into these cars was to drop a 13B-REW or a 13B-RE and do a single turbo on top.

-Roen, mod on RX-7Club.

ilikecars

so the real issue isn't detonation, it's that the seals can't handle the load? as far as more power goes, mazdatrix is working on 3 and 4 rotor e-shafts and a turbo setup. don't know how the testing is going though.

ilikecars

I talked to Dave at Mazdatrix a couple days ago. I was asking about ethanol and detonation and got a very similar reply ^^you got from Dave. A properly tuned engine engine won't destroy apex seals. Ethanol and water/meth injection will allow for higher boost pressures, but this is what causes the problem. RX-8 engines have a weak combustion pocket, and the high pressures will actually dent the pocket. This was also problematic on past turbo engines (I think he mentioned the '91 but I'm not positive). The pressures will also push the side plates away from the rotor housing. These obviously cause lots of problems, but Mazdatrix does have a solution. They can bore the holes for the rotor housing bolts and use the larger ones (AMAZING...cause it's simple and a no brainer). Although this solves one problem, it will also put more pressure on the weak combustion pocket. Dave didn't mention anything to solve that, but I'm sure someone is making rotors that can handle higher pressures.

As far as a renesis/rx7 hybrid goes, Mazdatrix is using one in their time attack car. It makes 400hp on E85 @ 14psi IIRC. It uses stock renesis rotors and plates, and, I think, 89-91 rotor housings. This means it has 6 exhaust outlets!

I asked if using ethanol hurt anything, and Dave said he wasn't sure of the long term effects, but the 2-stroke oil they used had a bad reaction w/ the ethanol and would gum up the engine, so they switched to one made by Klotz.

Sorry for the long post on a pretty inactive thread, but thought I'd share in the spirit of going too fast and embarrassing corvette owners.

stinksause

iTrader: (5)

thanks a lot man ... that's awesome info!

Another issue however is the oil injection. Currently in the msp, the two oil injectors play a huge role cooling down the side and corner seals which are actually the major place of failure in our engines. Just premix does not solve this.

I am not going to go into and cover the changes in oil injectors over the years as I am sure you are familiar.

If they are running older PP exhaust housings, I am not sure how they solve this issue, as those would have single injectors from factory.

tofu_box

The issue with the renesis is not on the intake side of things, the intake port can move plenty of air.

The restriction is on the exhaust side. You need to get the air out.

The problem with exhaust porting is the water jackets around the port prohibiting any real porting work to be possible with the renesis.

If you look here you can see a factory port



Then this is a picture of testing on the factory port, you can see that there is not much room for porting before you puncture your water jacket



So therefore until you can get air out, by having bigger intake ports it is just a minimal gain.

Highway8

iTrader: (11)

My 2 cents and take it worth what its worth. I have never rebuilt a rotary motor and I only have a basic knowledge of the internal workings.

1- I have blown 2 Renesis in very short order whiel running FI on the track. Both times detenation or tunning does not appear to have been the issue. Both times my setup was maxing out my MAF sensor running 13PSI at redline. Both times my estimated RWHP was 320 but with a supercharger robbing power, my estimated crank HP was upwards of 425+.

2- A well know and respected Rotary Motor builder with a lot of experiance building Renesis Motors says the key to more power with a NA renesis is the intake ports. He believes the exhasut ports can flow plenty of air for NA. With FI, porting on the exhaust side would be beneficial.

3- The most common failure of the renesis aside from tunning is side seal failure as a result of side seal springs becoming week after extended exposure to high heat.

Thats all I got. I think the Hybrid motor is going to become the prefered choice for Renesis FI. But I also think we can make a lot of power with low boost/fast spoll turbos on ported motors. Street ports, 3/4 intake bridge, 1/2 intake bridge and full bridge ports are going to become more and more common.

ilikecars

I'm not really familiar w/ the evolution of the rotary to be honest (I had no clue about the injector #s). I didn't show interest it them until a year ago and haven't done much research on past engines. That being said, I wasn't smart enough to know to ask about the oil injectors, and I had called Mazdatrix for an entirely different reason.

shr3da

So from what I gather there is more than one issue restricting powere with the renesis, tuning, maf or physical.

On the issue of exhaust ports; is it possible to re direct part of the water jacket to allow for more porting?

ilikecars

what is the problem w/ tuning? there are limitations to the sII, but turblown is talking about a piggyback system that doesn't effect the stock ecu. still retains trac control and no warning lights. the maf can supposedly handle upwards of 400 hp (a couple posts above). any higher and you'd might as well go to a standalone anyway (assuming you could go higher). Also, I don't think you bypass a water jacket, but if i'm missing something let me know, because I'd rather be wrong and learn than be "right".