DSMTalk Forums: Mitsubishi Eclipse, Plymouth Laser, and Eagle Talon Forum banner
1 - 19 of 19 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter · #1 ·
I'm looking for an exhaust for my 97 GSX. I'm thinking about either the Apex Dunk or the Thermal. Does anyone have any suggestions?
 

·
Registered
Joined
·
88 Posts
I would give the 2.5" pressbent exhaust from Buschur Racing a try. It is only $350 and probably has bigger bends than the Apex, unless you are going bigger turbo, then get the Thermal. If you don't upgrade your turbo you won't need 3" exhaust.
 

·
Founder/Former Owner
Joined
·
5,120 Posts
Whats the future plans? I think might as well go 3", once you start modifying most people can't stop, so you might as well go 3" now... you know you're just going to upgrade the turbo eventually :)
 

·
Registered
Joined
·
729 Posts
An exhaust that is too big could cause the exhaust gasses to lose velocity.

They say that 2.25 in intercooler piping is ideal. If you go larger than this the intake air actually loses velocity and can hinder performance.
I think the same goes for exhaust. when the gasses are exiting the turbo they are super-hot and traveling very quickly. If they flow into a larger container like a 3in exhaust the flow of the gas slows down. Not only that but as the gasses slow down they also become cooler and more dense, which in turn slows the flow even more. This will actualy create more back-pressure.

If you think about it, if you take the total volume of gasses in a 3in system compared to the total volume of gasses in a 2.5in system, the exhaust gasses coming out of the turbo have to push on a larger volume of slower moving gasses to make way for the newest gasses.

Another way to think about it would be that the total volume found in a 3in system would be equivelant to a 2.5in system of a much longer length if both systems had equal volume.

Did I chew this up enough?
 

·
Registered
Joined
·
729 Posts
Anyways kunkman, unless you plan on dumping $10,000 worth of go fast parts in your car and you are running 10's or 11's there is no point to a 3in system. I'd recomend the 2.5in buschur system. For its cost i doubt you can top its performance.
 

·
Founder/Former Owner
Joined
·
5,120 Posts
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Anyways kunkman, unless you plan on dumping $10,000 worth of go fast parts in your car and you are running 10's or 11's there is no point to a 3in system.<HR></BLOCKQUOTE>I disagree. I am not saying a three inch system is for him... he hasn't said what is mod level is currently, or what he has planned for the future.

But saying you have to have $10k in mods and/or run 10s or 11s is a *little* :) bit much. I run a full 3" and I am not in the 11s. My best ET is 12.4 and when I make the simple switch between a test pipe and high flow cat the difference is noticeable. My turbo is a small unclipped 16G. I wouldn't dream of downsizing my exhaust diameter. Most 16G guys I know in the twelves run 3" as well.

I don't want to beat a dead horse here because only kunk knows what he has now or has planned with mods. But I would say sure, there are reasons to get a 2.5" exhaust and there are reasons to get a 3" (without having $10k in mods or running 11s).
 

·
Registered
Joined
·
4 Posts
Discussion Starter · #7 ·
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by WhoaTed:
Whats the future plans?...<HR></BLOCKQUOTE>

Right now all I have is boost and A/F gauges. Filter and plug wires should be here monday.As for future plans, I know I want an exhaust, upper I/C and BOV, MBC, hi-flo cat and a downpipe. I'm not sure how far I want to go. When I first bought the car I wasn't planning on doing anything, but here I am.

Thanks for all the help.
 

·
Registered
Joined
·
88 Posts
I agree that if you have the feeling that you might go bigger turbo, get the 3". No since buying another exhaust next year :D But I am worried about noise. For me I would go small 16g and 2.5" exhaust. My $.02
 

·
Registered
Joined
·
729 Posts
Ted, I bet that 3in exhaust doesn't make your car any faster than a 2.5 would. Yeah it looks cooler :), it probably sounds cooler :) but on a car running 12s it probably doesn't add anything to performance.

Now i will admit that i havn't actually performed an experiment on a car to see the differance, but until someone can show me otherwise I have no reason whatsoever to be swayed by the market.
 

·
Registered
Joined
·
729 Posts
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by WhoaTed:
I run a full 3" and I am not in the 11s. My best ET is 12.4
<HR></BLOCKQUOTE>

Im not trying to sound mean here
but if i said that my car runs 14s and I have a 3in exhaust, would that mean anything?

I know that i am argueing against the common consensus here with what i am saying. But i Havn't seen any hard evidence to support the bigger is better mindset. Only that everyone just automatically follows the rule. Plenty of people have made plenty of money because that "rule". I urge you all to save your money(or at least spend it wisely).
 

·
Founder/Former Owner
Joined
·
5,120 Posts
You are right Tony I have heard nothing but good things about that book. I'll take your advise if I get the time :)

For now Alex I am going to (perhaps ignorantly :)) believe that I am better off with my full 3" system than anything of a smaller diameter. If I come across any printed support to my belief I'll post it here. I respect your opinion though, and I have heard others voice it.

Kunk, I subscibe to the "bigger is better" philosphy, especially with the cat-back. Good luck.

[This message has been edited by WhoaTed (edited August 19, 2000).]
 

·
Registered
Joined
·
729 Posts
I've just been calling all over to find corkys book and woulden't it figure that no one around me stocks it. Guess i'll have to order it.
 

·
Founder/Former Owner
Joined
·
5,120 Posts
Amazon.com has it for $34.95
Maximum Boost : Designing, Testing, and Installing Turbocharger Systems
by Corky Bell
 

·
Registered
Joined
·
43 Posts
you all need to go out and buy Corkey Bell's book on turbocharger theory. No matter how much you think you know, you WILL learn something. And as we all know knowledge is...
for example, did ya know 2 3" pipes flow the same as one 4". Optimum exhaust velocity is 250 ft/sec, intake is 450 ft/sec

Tony
95 GSX
96 TSI AWD
90 GST
 

·
Registered
Joined
·
729 Posts
So Im thinking that a 2.75 in exhaust would be ideal for at least 500 flywheel horses. Only problem is that no one makes one. I have a freind who claims he can get me small amounts of stainless in whatever diameter i want for $5 a foot. Does anyone just happen to know off hand what the length of their 3in exhaust is going through all the bends from the cat to the muffler? I'll try to buy at least this length and then see if extreme or thermal or someone can mandrel bend it at all the right places for me, and then if i cant find a good muffler at that diameter i will put a cone on for a 3in muffler.

Not only would this maintain exhaust velocity better, but it would also allow for slightly larger bends.

It might be a little while before i can make it all come together but i will let you all know if it works.

Maybe i've spoken too soon on everything i've said about exhaust here, but i'll find all the equations i need and do the math and post it as soon as i can.

[This message has been edited by gsxalex (edited August 19, 2000).]
 

·
Registered
Joined
·
729 Posts
Ok, looks like Mr. Bell is not going to disagree with any of us. As he explains it the 250fps figure is more of a figure not to be exceeded than an optimum figure. once this amount is exceeded the amount of drag produced by higher velocity cancels and then exceeds any benefit of faster moving exhaust. Slower exhaust velocities are not necessarily bad, however the tighter bends necessary in a larger diameter system definitely are.

I suppose a 3in catylitic converter would have less backpressure than a 2.5in one as would the 3in muffler; score one for the 3in system. But for those who don't like noisey systems the 2.5in will prevail.

According to Mr. Bell's calculations the 2.5in system should have sufficient if not superior flow for up to about 500bhp. While the three in system would be good to a bit over 700bhp. Does anyone know the differance or conversion between hp and bhp?
 

·
Registered
Joined
·
729 Posts
I found out about maximum boost from overboostededs post. I crave technical stuff so I had to get it. I ordered it from the source at Bell Engineering in texas(210-349-6515) for $32.50 plus shipping. There is lots of good info in there with tons of formulas for calculating anything you need to figure out. There are some areas that still left me with unanswered questions, but the basics of everything are covered quite well. I highly recomend it for anyone who likes to squeeze every bit out of what they have.
 

·
Registered
Joined
·
729 Posts
Oh Ted, just so you know I just got the book today, if that is what you were asking.
 
1 - 19 of 19 Posts
Top