In the latest Circle Track there's an article by David Vizard that goes into the subject of exhaust systems in the context of increasingly restrictive noise standards in racing. The article explains somewhat the function of some exhaust components and desirable and undesirable effects in general terms. It is the most interesting article of it's type I've seen in a while.

I've had some contentious posts about headers in the last year, rooted in the fact that nobody can explain the what's and why's of some of the latest trends in design.

What prompts my interest is (was) my intention to run a straight 2.5 from off my header to a race muffler located in the stock location - eliminating the stock Catalytic Converter and Resonator. Then I read Vizard's article, and I start thinking that the full length pipe without a well designed resonator (to "end" the collector) might cost me top end power. I check with Scott Zellner and he says that ITR's like short pipes (RTR and King run a small straight thru (Borla XR-1 for King - which Vizard meantions in his article as being "transparent") and dump under the car). Well, Damn, what am I gonna do?

I want to run all the way to the back of the car for reasons to do with my rear diffuser. I could tuck a Borla up into the tunnel, and then come out the side with a Dr. Gas Boom Tube, but that's apt to be messy and cost me ground clearance (another of my motivations is to increase ground clearance), and further disrupt underbody airflow.

I've looked around alot, but found little. There's supposed to be an SAE Paper from the last couple of years on developments in racing exhaust - probably from NASCAR - that could be relevant and interesting, but I haven't been able to find it yet. Many of my racer friends (who either have their own dyno's or routinely talk with nationally known engine builders) say that headers are an overhyped subject, and that many of their best results have come with the "wrong" design. Ok, then, but I could still do something really wrong and kill some power - so why not try to avoid unnecessary losses.

So - THE QUESTION: Do any of you know much about this, or where to find helpful and instructive materials?

Scott, who doesn't want to fight with anybody.....if you know what I mean......

 

Scott, dunno if you read this yet: https://honda-tech.com/zerothread?id=130037

There was a BIG difference coming out of corners and motoring down straights. I don't dare look down at the end of a straight, but it's significantly faster. Not to mention wildly louder. As for keeping it quiet, talk to Dave. He actually suggested to me at first to run it all the way back.

You should actually give him a call. If you want his number, I can give it to you. He's a really good guy, and he's not gonna try to push his stuff on you if that's not what you want.

p.s. Spoke to an engineer at JIC today. He used to race in Japan, and raced at the 24 hours of Daytona a few years back. Interesting stuff. Here's the part you'll find funny. He said pretty much everyone there runs higher spring rates in back on Tegs. This is straight from a Japanese race team. I need a translator though. It was kinda hard to understand him sometimes. Gathered some very interesting info from him though.

Warren

 

You may or may not have seen these already, but I'll post them anyways
http://www.racingarticles.com/

Most of what is said in here is to be applied to Big V8s and the such, but there is some general principle that can be learned.

 

Try the Library of Congress - there has got to be something there

BPR - who will look in his local "library" for applicable reference materials

 

Warren - What's this Magnaflow Resonator you've got? I looked over their site and find round mufflers, but nothing specifically called a resonator.

Martini - "racingarticles" is a nice collection, but nothing that does the trick. Thanks anyway.

I'm going to have to see what will fit in the tunnel, and what is available. I did find ROUND Borla's on Jeg's site - so maybe one of those and a boom tube will do it. I'm not in a huge hurry to do this yet (I'm in a huge hurry to get other things done right now).

Scott, who doesn't want to get into motors and horsepower.....who doesn't want to get into motors and horsepower.....who.....

 

It's basically a straight through 22" resonator/muffler thingy. 4" round, 2.5" connections. It's not a stainless resonator, I think it's aluminumized. The piping that Dave uses is stainless.

If you dump out the side, I think it'll be tough to pass sound. Our local track has begun testing sound from both sides. Dump it at the end of the tunnel facing down (trailer queens only), or go all the way back with a good high flow resonator and muffler.

Before you go re-inventing the wheel you may want to give SMS a call and ask for a quote, or ask him about some of the engineering. I'm sure he'll share what he can. He can answer these questions better than I can.

Warren