I just got this yesterday. 4" mandrel bent Also in the pic are the beginnings of my exhaust manifold. Yes those are cad designed, tuned, equal length, mandrel bent runners




Things should start to get interesting.

and for those who missed it in my previous mods:
I have twins!

 

What's it going to mate with?

 

There is a point of diminishing returns. Having a huge downpipe doesn't automatically/necessarily mean improved exhaust flow/performance.

 

No kidding. Carlos Gonzalez doesn't have any problem running low 8 second quarter miles with a 3 inch exhaust.
Header/exhaust manifold design is *much* more important.

 

Sweet, I want to see pixs of the manifold when its done along with those twins mounted..

 

Any one that is running twin TIALS must have something hardcore under the hood. To eachs own.

 

What the **** is that for? Twin T66's?

Have you checked to see if that'll fit under the car? I've seen FC's with 3" exhaust pipes under the car, and they don't have much for ground clearance.

 

Sweet! What turbo are you going to use?

 

As a matter of fact yes, this does fit under the hood/car... yes it fits. The whole thing is above the frame rails. It's all in the design with proper placement of bends.

As for the size. There is a point of diminishing returns yes. And yes, people do make power with 3" pipes. However... that is *not* optimal. Search for posts by garrett turbo engineers on the web. You will find that Garret actually says 3" tends to be on the small side for a 400 HP car. There are people on this list who, IMO, have proven that huge exhausts do benefit the rotary via significantly reduced back pressure.

Check out magnus and his Gt42. He spools that HUGE turbo nearly as fast as all the people with Gt35/40's which are quite a bit smaller. This is with a large DP and a properly designed manifold. Which is why I also included pics of the runner for my manifold and stated they are tuned equal length to all the specifications that have been shown to make power efficiently. They are CAD designed and I can guarantee that they are exactly the same length etc.

The problem is that people take something that work "well" and then don't bother to make it optimum. Take all the Gt35/40 kits out there for example. Not one that I have seen has an equal length manifold, much less tuned.

I have been researching for a year now and have selected components which I feel combine the attributes of an optimum turbo system. And that is what I have done.

We'll see how it turns out.

 

I see a Gt35/40. That looks nice. When you get the mani done, post pics. I'd like to see.

 

the 35/40 is not even close to an off the shelf turbo though... it's being tweaked.

 

Good to hear that you had done quite a bit of research.

Do you happen to have a link to the discussion regarding exhaust sizing by garrett turbo engineers? I'm getting all sorts of links, but they are mainly to vendors and not the actual discussion by engineers.

 

WE MIGHT HAVE A CONTENDER FOLKS!

 

Looks good, who did the bends?

 

A shop in Illinois (did I spell that correctly)? did the bends unfortuantely they don't handle smaller than 2", so I have to get the WG pipes done else where. I was a bit nervous to be sure that my computer model was accurate with that huge of a pipe.

They were the only place I could find that would do small quantities... like since I'm only making two setups right now for testing.

DOM,

I should have provided the link im my origional statement. Here is a post that I made several months ago. There is a link in that post that I was specifically refering too. I had several people PM and comment that it was well thought out... but that I may have imtimidated people into not responding. Oh well.

https://www.rx7club.com/forum/showth...hreadid=161657

FWIW, this pipe was really just for test fit and I know it fits... so if I decided to back off to 3.5" I know it'll work... might not necessarily work the other way around.

 

Sorry if my post was confrontational at all.

My cat just peed on my new Bride seats!!

 

hahahahahaha, that cat is such a bastard. You should put it in the toilet with the seat down and give it a flush. You hate it, and it hates you, and everything you love!!!! That sucks!

 

Hmm...I might have to send this link to some friends of mine. See what they have to say.

Regarding the Bride seats,...dude that sucks (although they would've gotten sweat/grease marks sooner or later).

 

True on the sweat. But cat pee? Blah.

I'll be curious to hear what they say as well. Post or PM me when you hear something... I can always stand to learn more. I didn't get any criticism then, so I've been marching forward accordingly:0

Please do let me know what you learn though.

-Chris

 

I'll post the response that I get from them. Let's just say....they are HIGHLY knowledgeable about all things turbo....hahahahha

 

Bride seats, twin Tials, someone win the lottery?

 

We're talking like 800-900 horsepower on that 3" pipe. The backpressure you *really* have to be worried about is the backpressure in the runners of the exhaust manifold.

Are you routing the wastegate dump tubes back into the exhaust? If that's the case, then I can see why you'd want such a large pipe.

I'm not saying that I don't overkill certain items on my car (a pump that can handle 800hp on a car that makes 450, for example). I just think a 4" pipe is about 1" larger than what is needed.

The exhaust manifold should be nice. I agree, it's a shame that so many of the manifolds I've been seeing recently don't use equal-length runners.
Best,
John


As for the size. There is a point of diminishing returns yes. And yes, people do make power with 3" pipes. However... that is *not* optimal. Search for posts by garrett turbo engineers on the web. You will find that Garret actually says 3" tends to be on the small side for a 400 HP car. There are people on this list who, IMO, have proven that huge exhausts do benefit the rotary via significantly reduced back pressure.

Check out magnus and his Gt42. He spools that HUGE turbo nearly as fast as all the people with Gt35/40's which are quite a bit smaller. This is with a large DP and a properly designed manifold. Which is why I also included pics of the runner for my manifold and stated they are tuned equal length to all the specifications that have been shown to make power efficiently. They are CAD designed and I can guarantee that they are exactly the same length etc.

 

What length and diameter did you select for the manifold piping? I've always been curious about the optimum size for a rotary.

 

I chose 15" length and 2" diameter. There are TONS of posts on this and unfortunately, I'm not sure there is a single, 100% right answer.... so after reading, and reading, and then reading somemore and listening to what people said, what people were doing and who said it... I selected this combination.

Oh, and I am planning on venting back into the DP... the cops out here are just looking for an excuse to give someone a ticket and with a full RE body kit my car will draw enough attention without it screams everytime a go WOT.

-C

 

wow, that's a sweet setup chris. I can't wait to see it running.