Speculation On Tuning
 

Well here goes. I plan to build up my RX8 as many of us do. I also have done some math. Keep in mind this is a major guess at what the engine can handle, and we may all be pleasantly suprised or let down when it finally comes but based on some of the FD knowlege this is what I have in mind.

I will be waiting for lower compression rotors, hopefully down to about 8.2:1 or 8:1 so that way i can run 15 psi, and on this motor your looking at roughly a 150 hp gain, keep in mind though you will be losing fifty HP (approx) with low compression rotors, so thats 350 HP. Do some porting and based on what some FD's did I assume about a 35% power increasement (thats hard for me to swallow but that is what has been said) and that takes you to a wopping 470 hp (rounded DOWN). Add a good exhaust and you can benefit to about an additianal 10-20 hp, I say 15 for arguments sake. Thats 485, add an intercooler and get another 15 and you now have 500 crank hp. and 400 RWHP. Am I adding in the wrong order, are any of my numbers off, please discuss this in here.

I'm not sure if (street/mild) porting will do much for this engine since its ports are going to be very tall in stock trim from the factory. Unless, however, you were thinking of bridge porting :D Then maybe your numbers will actually be very close.

Yes it was bridge porting that was brought to my attention.

Keep in mind velo that there's all kinds of street and bridge ports. I'll list them for you:

1) Street port-
The side port is extended slightly. A mild increase of 20 to 30 HP can be expected.

2) Bridgeport-
An extra port is added to a street port right up against the edge where the peripheral housing meets the side housing. If performance carbs and exhaust systems are installed you could get a 70 to 90 HP increase.

3) J-Port-
A bridge port is extended past the edge of the peripheral housing, but not far enough to break into the water seal.

4) D-Port-
Very big port, the water seal is violated and so is the water jacket, so there must be restoration to maintain cooling. Don't expect the engine to last very long.

5) Peripheral port-
The rotor housing is ported. This port is often eliminated by racing rules. The motor will not run below 2000 rpm.

This is what you would expect on a normal and current rotary engine (10A 12A 13B 20B) and not a renesis rotary. But we won't know the pros and cons of the engine until it arrives in the u.s.

If your only looking at running 15psi then going to decompressed rotors is not needed.

Keeping the compression std aids off boost performance, and as long as it intercooled properly and the management system is tuned correctly you will have no worries.

9.5:1 is a wee high for turbos I think. It may work, but engine life will be extremely lower. I just have to wait and see.

Why will engine life be lower?

Engine life is related as much to tuning as anything else.

We built an RX-4 about 7 years ago for a mates girlfriend, which had a mildly ported std compression RX-4 engine, 2-speed powerglide transmission and the std 3.9:1 RX-4 diff. The car weighed 2680lbs, ran premium unleaded fuel (95 octane) and had a set of 26x8" M&H street tyres.

The car run 10.91@124.8mph in full street trim, as driven too and from the track. The engine in the car has been totally reliable with no so called compression related dramas.

The car is running a MoTeC M4 Pro and has been tuned correctly, and this I feel is where reliability is gained or lost.

std, 9.4:1

Okay, dumb question, what is porting? Must be a rotary thing.

Porting is simply changing the shape and size of the inlet and exhaust ports to increase the amount of air they will flow.

I'm betting Mazda has evolved the NA 1.3L Wankel about as far as you can go. More power probably means boost or N2O.

hate to tell you this but in the states we need lower compression rotors cause the Highest octane gas anymore is 92 or 91. 93 is like non exsitent and we will have to add octane booter every time we gas up. and I don't know bout you but I am very forgettful and If that motor gos cause I didn't put the oct booster I will be pissed off.

I don't see how you can think the rotary has evolved about as far as it can go. The piston engine has been around far longer and had many, many times more research dollars put into it and advances are still being made. If the rotary had anywhere close to the research put into it that the piston engine had, it would be much farther along than it is.

Of course, the rotary has benefited a tremendous amount for the work that's been done on piston engines. I still think the point is valid. If piston engines aren't maxed out, neither are rotaries.

He's talking about needing 95 octane in a hugely modified old rotary. An unmodified rotary in the RX-8 should be reliable. There is no reason to suspect it won't go 200k+ miles if properly maintained. Of course, it's possible that there will be problems, but that likelyhood exists in all engines.

In std trim an aspirated rotary does not need high octane fuel due to a lowish compression ratio compared to most late model high performance engines like the Honda V-Tecs and such.

Even with the 3rg Gen RX-7, most of the problems were not engine related. Problems with turbo's, manifolds etc have nothing to do with the reliability of the engine itself.

doctorr said:
How about replacing the runner entirely with a new one using the same or similiar ceramic/heat coating process? How expensive would this be (guesstimate)? I'm guessing then it would have to be port matched if this was possible at all. Am I way off, or is this a possibility with the right R and D?

I'm also interested in knowing how many other mods are needed in a street port to gain 20-30HP. To me that's a pretty good gain from only one mod. Also, does porting(street or bridge) effect low end torque like it does sometimes with modified cams in piston engines? Sorry for all the questions, I'm still new to rotaries and interested in learning.

i don't think your asking too many questions. the only thing i know about rotories is they go round and round instead of up and down! i'm just glad someone knows something to ask. i was lost at "porting" until some asked and answered that one:D

Thanks, Zoom44...
 

...now if only one of the resident RX-8 forum experts would be so kind as to respond with some answers or educated guesses :) .

Ya, I'm new to rotaries too
 

I'm not new to the concept, my dad had a second gen convertable, but that was before I could drive. I've had several friends with RX-7's but they were happy with them in stock form.

I don't know much about what mods will eventually be available for them. I'm too chicken and cheap for big time projects, but I was hoping that with upgraded intake, exhaust, and electronics we'll be able to get the RX-8 up around 300 HP.

Or am I wrong; will Mazda have the Regenisis close to it's maximum potential when released?

The Evolv had 280HP...
 

...until they tuned it back for whatever reasons (maybe reliability). I seriously doubt the Renesis is maxed out in factory trim. Mazdaspeed and other tuners will no doubt jump on this car from the get-go and make some good aftermarket parts with good power/handling gains. If I modded my RX-8, I would keep it NA. I would hope to gain 30HP with no loss in driveability, but until the car is actually here we can only speculate on its potential.

I'm also interested in keeping the engine in NA form so as to keep it more reliable and simpler. However, I intend to eventually procure just the Renesis motor, possibly with a Rx-8 trans, and install it in a Rx-3. The Rx-3 from 1972 was rated at 2060 pounds and would really haul ass with 280 to 300hp and some 4.5 gears in the diff. It'll take a while to get all the necessary pieces together but I deffinitely think the finished product would be well worth it.

i'm not going to allowed to do any big time mods by my wife. but hope there will at least be a chip swap available i could slip that by her. and maybe my exhasut will develop some hole by "accident" so that i can maybe replace it with something thay will loosen up a little hp. :D

I figure with standard bolt ons (intake, exhaust, ignition) a lightened flywheel, and maybe some deeper gears the rx-8 will got mid 13s. Thats enough for a daily driver.

smog legal
 

legend has it that california is one the most largely-targeted markets for the rx-8. thus, as california has some of the tightest anti-smog laws in the states, then im guessing the power difference between the rx evolve and the rx-8 is largely due to emissions control. thus, in order to get a significant power increase out of the rx-8, one may have to not give a hoot and pollute. (go woodsy owl!) IMHO, cars that are 73 and older are the ones people should buy, tinker with and trick out. i mean, if youre spending $30k on a car only to void the warrenty and risk ruining the engine (not to mention potentially having to smog check your car illegally), and ending up with a 2700lb car and 300HP, then why not just spend the same $30k+ on an old beater car and make it haul butt? even though i love to fix things that arent broken, i think the rx-8 (as with buying any new car) may be best left stock. or at least modify in moderation like Rumblee - chips and exhaust are one thing, but porting and adding turbos are another.

i think Mr. Wankel has the right idea with taking a smog-exempt car and putting some new technology in it. its not going to cost him as much, he can even strip off all the smog gear from the renisis if he wants and he'll still have a killer yet legal car.

I will be happy to tune the vehicle, hopefully to get around 300 hp without turbocharging. Any suggestions??