cretinx

Ok, just a few thoughts.

First - how do you lower compression on the rotary? Is it in the seals? I know that raising compression might give some gains but I think when the displacement is this small, and the turbos spool up about 3 times as fast as on a piston engine, we need to go with boost for power - so, lowering compression to maybe 8.8:1 or 9.0:1 would let us boost a few more pounds safely.

Rotors? I've seen these on racing beat's website. Are they tougher as well as lighter? Can we expect to see anything realisitically out of lighter rotors, or is it more for the open wheel racer using rotary power and needing that last 2-3 horsepower in his 1200 lb racecar?

Finally, porting - its been discussed, I checked out a thread in the Aftermarket area - why so expensive? Old rotaries used to be about $600 total to port and you'd make great gains - no rotary was complete without a streetport (bridgeports were worthless cuz your motor would die quite quickly). I bet with FI a porting will probably give 30-40 horsepower if done right. I'd do it if I could get it done affordably.

Ok - discuss.

Red Devil

I may be wrong, but to change compression is to change the available space within the combustion chamber. For a rotary, meaning the face of the rotor would have to be altered, and from there would either raise or lower compression. Don't know whether this is possible with Renesis rotors. But I have seen some discussion from time to time of people questioning running the REW 9:1 rotors in the Renesis instead.

Nemesis8

iTrader: (3)

Didn't we read that RE- Amemiya is going to experiment with placing 13B-REW lower compression rotors in their test mule 8, and then turning up the boost on the Greddy?

rkostolni

I'm also very interested in what we could do internally to allow increasing the boost. What kinds of things did people do to the Rx7 engines and how much did they usually have to spend for those things?

cretinx

With the old 13b-REW most people kept the compression the same when they rebuilt - they'd clean up the oil passages, port the engine of course, and replace the seals with thicker ones, preferably 3mm if you're going ***** out or 2mm if you still wanna keep some regular behavior (my ported, 3mm sealed engine took a few tries to get started, spewed a cloud of blue smoke on startup, and had an insano idle, but **** was it ever fast).

I'm totally intrigued by the concept of the lightened rotor because thats rotating assembly weight loss which can translate into big gains.

Obviously I'm still baffled why porting is so expensive - I'm going to call KD Rotary about it at some point, they told me a few months ago they were playing around with some Renesises they got their hands on.

SharkDiver

Wouldnt lighter rotors lessen the tourqe?I dont know. :o
shark

guitarjunkie28

bridgeporting worthless????? dood, i don't know where you got that info, but myself, and a few other guys i know all daily-drove our bridgeports...turbo bridgeports at that.

and there's even an aux-bridgeported renesis driving around so. cal on a daily basis

i don't know how much other guys are charging for the porting on a renesis, but it's not all that much... we got 9% running richer afr's than stock with just a really mild streetport, so there is potential, but i think most of it is gonna come from the exhaust porting.

i don't know about the older rotors in the renesis motor. the side exhaust port layout is gonna eat the side seals quick-fast-and in a hurry. hell, even the renesis side seals get hammered on enough, and they're even designed for it!!

Razz1

I think you should wait a couple of years for the factory super charger rather than try to lower the compression in the 8.

Jon-PTP

Compression was changed in previous rx7 engines with rotors from older engines and sometimes compression was raised using non turbo rotors... etc....

porting is expensive because it has become hard to find someone who can do it well without breaking other things. But alot of power can be gained from porting and unfortunately alot of power can be lossed with a bad port job.

slavearm

I am hoping that aux-bridgeported renesis makes its way towards my house soon :D

Moostafa29

In the famous words of Lil Jon...WHAT?

guitarjunkie28

cretinx

Ok, Bridgeporting isn't WORTHLESS - you make a shitload of power - but enjoy rebuilding your engine frequently. Most of the guys I know who did it had all sorts of problems, the least of being the total loss of street driveability.

guitarjunkie28

if they lost streetablility or reliability, they did it wrong! come on man, i daily drove mine and beat the **** out of it and it always held up...not because i spent a lot of money on it (i built it from spare parts i had laying around), but because i took the time to measure my clearances and design the bridge in such a way that was NOT going to degrade the reliablity.

btw, the aux-bridge renesis is now averaging a 3 mpg increase over stock. that should give you a hint that there is NO loss in streetability.

rotarygod

Myth! The longer and thinner the bridge, the weaker it is. The people that have failures typically have gone too far with theirs. A small bridge that isn't made too thin should be as reliable as anything else in the engine.

Loss of street drivability is a subject to opinion. Personally I wouldn't drive one on the street but many do. The biggest problems with these higher overlap engines on the street is that they can't be muffled very well without hurting the power, higher fuel consumption, and part throttle/low load levels are not very smooth. They do make good power across the rpm range when compared to traditional stock or street porting styles. New issues need to be addressed with bridge porting such as the intake manifold and exhaust. You really shouldn't use the stock setup at this point as you are not using your new ports to their full potential. Many people overlook this aspect and even a fairly well known and respected rotary tuner recommends a less than optimal setup for daily use. You'll very easily lose streetability from the wrong setup.

guitarjunkie28

i should clarify on the streetability thing too..

on an aux-bridgeport, the engine reacts almost identical to the way it would with either stock or a streetport until the aux ports open--THEN it makes the power.

on a half or full bridgeport N/A car, you'd lose all sorts of low end and gain it up top.

on a TURBO half-bridge, the loss in natural low end is replaced with faster spoolup from the turbo, pretty much cancelling it out, depending on everything.

i had a really big halfie on my fc and i noticed less power from 1000-2500 rpm, (partially from me swapping the hot side of the turbo from a 1.0 to 1.15) but how often is the engine below 2500rpm anyway?--especially a renesis!!? on my buddie's "street-bridge" i did for him, there was NO noticable loss anywhere. turbo cars are a different animal than the n/a cars, and should be treated as such.

cretinx

SO who do I go to do get my turbo renesis ported, and which port would you recommend?

Also - are the lightened rotors worth it?

guitarjunkie28

i could do it, and i've heard of a few other shops doing it.

i'd probably just do a streetport.

cretinx

location and price?

guitarjunkie28

pm or hit up the website for price.
i'm in hesperia, ca