dezodwest

The exhaust is a baffle system. The exhaust is built with 2.76" piping from the midpipe back. Not sure what you are talking about with the exhaust flames. I never made any mention of flames in this thread. I can not post here to sell product for I'm not a sponsor. I plan on signing up soon, but right now I am simply providing info. I do have a store, and I do sell product (a lot of product) but can not link things directly on this thread per forum rules.

Here are some new pics showing the exact layout. The exhaust fits perfect, and has no evidence of melting or disfiguring the shrouds, which is a good thing! I've heard of other exhaust with large tips doing this, but no problems here.

swoope

iTrader: (5)

sorry i read fast some times. you mentioned exhaust fumes.. that is what i caught. so many here ask for flames..

still would love to see the 90 deg shot where the back pipe hits the y.. and you can always send me a pm.. i like to learn..

the bad thing about exhausts is you really really have to hear them live..

beers

dezodwest

I have some decent cameras. I could attempt to record the exhaust, and maybe a couple drive-bys if you guys want. Next time I have the car in the air I'll take a picture for you.

Easy_E1

iTrader: (2)

Good to see your making some headway with the system. Loking good.
See you on the 31st.

HockeyRX-8

iTrader: (1)

Please post a clip of how this exhaust sounds. I'm thinking about getting this exhaust, but i want to hear how it sounds first.

dezodwest

Video coming soon.

arghx7

I want to inject a little skepticism into this thread, not as a flame, but more as a challenge and a prompt for discussion.

That's fine I suppose, but it's still a rotary... how much "useful torque" do you expect under 3 or 4000 rpm without a restrictive turbo setup with a small hotside? It's all relative I suppose. Face it, these engines are relatively gutless down low anyway, so why not build it for where it's strong, 5000+ rpm? Having a good response down low has a lot to do with manifold design, with a divided tubular hotside ideal, and appropriately sized for your application. On an old setup with a stock turbo on my 88 Rx-7, I made 250rwtq @ 3500, but that's because the boost quickly dropped off due to the restrictive hotside on a stock turbo only made to hold 6psi to redline. You can also improve spool by messing around with your timing map.

True. Rx-8's are all about keeping weight down, which is the enemy of performance.

I agree with this as well...

Here's where I think you are getting off track. Talk to anyone who designs turbo manifolds. They will agree that if you make the runners (as in PRE-TURBO EXHAUST, not POST-TURBO) too big, it will slow velocity and hurt spool. So you are operating off a correct principle.

But constricting exhaust after the turbo is NOT good for performance! Why do you think when you put a bigger downpipe on an otherwise stock turbo car, the boost increases and can sometimes spike? It increases volumetric efficiency, and it increases spool. Why do you think people run big hotsides on large turbo setups? a 4" downpipe is going to make more power with better spool on a custom setup. Now you still have to optimize, and I'm not saying a 4" exhaust is going to be the best option for a 280-300rwhp car or that it will make a huge difference over 2.5" at such a relatively low power level. And that doesn't mean either you can't get away with something under 3 inch and still make good power.

But to claim that having a restrictive exhaust post-turbo is a performance benefit in and of itself is just not true, all weight and space considerations aside.

Again:

A larger exhaust INCREASING backpressure????? think about this man!

kersh4w

iTrader: (3)

uh yes, he is right. as the gas cools, they slow down. this creates turbulence and can create back pressure by forming eddies.

also, larger pipes = more weight, and as you said yourself, weight is the enemy of performance.

ask yourself, why dont turbo 911s have 12" exhaust pipes?

dezodwest

I guess I should have been more specific then with the posts I've made. We know a lot about manifold and exhaust design. Not as much as certain tuners out there, but we've been making custom and production based turbo kits for about 6-7 years now. We even setup and program AEM universal EMS for car specific applications, and with out own serial number, AEM warranties it.

We have a good know-how when it comes to thermal dynamics, exhaust design, turbo design, and more. Smaller runners do indeed keep velocities higher which helps for turbo spool. I did not say in my my post that making turbo manifold runners larger will be beneficial.

A 2.5" exhaust supports over 300hp. A 2.76 approaches 400 with no problems. The idea is to not go larger than you need to. My argument is the added benefit vs cons when switching to a 3" rear section. The design of the Greddy Evo TT is very efficient. There are very little bends in the system which allows it to flow well. I agree that 3" can be beneficial, and that a 3" mid-pipe would still help. My argument is that if you go too large, it can indeed create back pressure IF the exhaust gases aren't great enough (both in speed and temperature) to fully utilize the amount of space it has to move in.

An example for exhaust efficiency:

We make our own custom stainless turbo backs for the Scion tC. With our turbo kit and a stock exhaust, the tC was dyno'd. We then switched only to our custom turbo back exhaust and on the same dyno picked up 34whp. This is all on a 2.5" exhaust. By keeping the pipe from getting too large, we kept a nice fat torque curve, and to this day have the widest power bands on the tC turbo kits available. At 8psi we had a car dyno 314whp. Here in AZ, the kit that came off my car made 261whp, at only 5psi.

There are a few different variables with the turbo when it comes to design. Sure the AR makes a difference, but the exhaust and compressor wheels play a huge factor as well. You then take into account the inlet diameter, and compressor and exhaust housing sizes. We've fit wheels into T3 housings that you never thought possible. I had a turbo on my last car that made a few psi at 2000rpm, but had more top end available than the head could even carry. Luckily we have many different lines and custom setups at our disposal. We can test different turbos on different cars to see how they react.

I know the rotary is a different beast than a piston engine, and we look forward to the challenge. With proper R&D, I think a really affordable race-ready setup can be attained.

Hopefully I addressed your challenge well. I know you're basically looking for statements in response to yours. If you have more questions or feel that I've missed on something, let me know and I will be happy to answer it. Thanks!

Schimmle

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arghx7

It's a rotary, these cars have no shortage of high velocity, high temperature exhaust. Our typical exhaust EGT's (1200-1400 degrees) would be pretty dangerous on a piston engine but are just fine for our cars. Have you ever measured EGT's on a rotary? Do you think 1400 degrees is going to cool down to the point of causing turbulance? I took my car out to Virginia International Raceway a while back and my EGT gauge pegged at 1600 degrees from hard running (I was running 100 octane race gas, the car was not detonating). I then sold the EGT gauge and will eventually move to EGT probes that can log up to 1800 degrees and output a 0-5v signal for datalogging. EGT gauges designed for piston engines are useless under those hard conditions. There is no shortage of hot exhaust in a rotary, and I doubt the Renesis is any different than the older ones. Why do you think cat life is such an issue?

Now there are clearly diminishing returns in increasing exhaust diameter, and the design of the manifold and hotside are more important for reducing backpressure, but 2.75ish seems like an arbitrary cutoff point for diameter. People run those on turbo 4 cylinders all the time. Racing Beat makes 3" exhaust for both 2nd and 3rd generation Rx-7's that are quiet and flow very well. But yes, I have seen 400whp rotaries with 2.5" exhaust. That doesn't mean 3" wouldn't be an improvement though.

mdw1000

Good luck on the build! Since you asked for suggestions, I would strongly suggest a Mazmart water pump. And, depending on what you are using for engine management, perhaps a Mazsport cooling fan mod.

dezodwest

I'm not sure who your arguing with. In my last larger post, I even agreed to a 3" being benificial, and did not say it was too big for the Mazda. I'm aware that rotaries run hotter than piston engines. I've seen the racing manifolds on the RX8 race cars (which I know are 20b powered), I've read threads, and it's well known that the rotaries run hot.

I did not say the car couldn't use a 3" mid pipe, cat-back, or anything else. I just argued that this specific exhaust will well support almost anyone's power goals that can be safely acheived with Renesis. Sure a 3" is another option. From the products I carried, and as a matter of performance, preference, fit and finish, and style, this seems to be the best exhaust I would put on my own RX-8. I went to a meet recently and everyone LOVED the sound of the exhaust. It doesn't sound like many out there and I feel it works well even for a non turbo RX-8.

You make valid points and I've never disagreed with you. There is no specific cut-off with exhaust diameter. I just feel that the Greddy TT is a great system out there.

dezodwest

Thanks for the tips. I've been eying the Mazsport cooling fan mod for a while. We plan on coming with 2 different packages for an oil cooler upgrade. One being a full bolt on, with SS line replacements, the other just being upgraded coolers.

Thanks!

mdw1000

I would eye the Mazmart water pump as well. Designed by one of the world's leading rotary engine builders. I see water temps drop much more quickly with it.

As far as the fan mod goes, it depends on what engine management you go with. I believe a reflash unit like the cobb can control the fans. But if you go with an IntX, etc, you would need to do it with a mod like Mazsport's.

dezodwest

Yeah we're still unsure of what EMS we'll be using. We may work with a company or two to try and come out with a new EMS all together.

The water pump mod definitely seems like a great unit. I'll post up what we decide on. Right now we're getting ready for the time attack event we're hosting next week. Busy times!

HockeyRX-8

iTrader: (1)

......so where is the sound clip of the exhaust?

Renesis07

iTrader: (1)

^^^^ +1

dezodwest

I'll try to do it today, I don't have anyone to tape it so it'll be hard to record load, but I'll see what I can do.

AEM is sponsoring our time attack event so I bought an AEM CAI fore the car for next weekend. I need to install that in a little bit, then I'll tape the exhaust.