Exhaust system performance

ellusion · Post by **ellusion** » Sun Jun 13, 2004 5:03 am

How much of a performance gain should i expect from a cat-back mandrel exhaust system??

Does a high flow cat (eg. 8L) give any gain?

ruchi · Post by **ruchi** » Sun Jun 13, 2004 11:05 am

Does this "exhaust system" include new headers too or just everything that is behind the headers?

Is this a custom job or off-the-shelf?

What gains has the supplier suggested it will give?

Who's doing it?

ellusion · Post by **ellusion** » Sun Jun 13, 2004 11:27 am

Just a cat-back exhaust is fine and wondering if changing to a high flow cat will be even better.

I would like to get a custom job from a reputable exhaust workshop but just wanted to know if there are any significant gains.

Its a GX so i can't use the UAS front piping....

Whate gains are you guys achieving? 5-10kw atw??

Boris · Post by **Boris** » Sun Jun 13, 2004 1:53 pm

Changin to a high flow cat ofcourse will make it better...

But you see I think you will only notice the difference if you already have a cat back exhaust and a good air intake...

It's hard to say by how much with all the mods, it's not like it's maths

But ofcourse there will be a difference, more importantly the slight torque improvement...

IMO first concentrate on the air intake side...

Just me 2 c...

ellusion · Post by **ellusion** » Mon Jun 14, 2004 2:47 am

i have got a k and n panel filter coz thats as far as my insurance will let me go. Now its the exhaust i would like to play with.

Does gaining power from an exhaust mean that the engine power has been increased?

Eg. in a gpx, the engine produces 147kw... and say 90kw atw. An exhaust simply gives more flow of air thus giving more useable power right? The engine would still be producing 147kw....

ruchi · Post by **ruchi** » Mon Jun 14, 2004 11:32 am

To over-simplify the process, the induction system is like your lungs, the fuel system is like your stomach, the engine is like your heart and the exhaust is like your bowels

.

By upgrading your exhaust system you are increasing your ability to get rid of the "waste" but unless you're taking in more through your induction (lungs) and fuel system (stomach) the improvement won't be as great and probably not worth the money.

To get really graphic, a restrictive exhaust system is like being constipated. Because of the extra back pressure you will be more sluggish and won't perform too well. Alternatively if you go for too large an exhaust you will have too little back pressure (diahorea) and will also experience problems.

The key is to understand that your car is a "system" and as such you must "tune" each of the components that make up the system. Changing just one will yield little result if it doesn't relate to the rest of the system. Even worse, upgrading one component can actually make the rest of the system perform worse if it is not matched correctly.

If you can breath easier, you're getting the food you need and you can expel the waste without any issues, then your heart will be able to pump harder and more easily (i.e. put out more power). So yes, if you upgrade your induction system and exhaust system the KW output of the engine can also increase.

I am very surprised your insurance company will let you modify the exhaust if you are not allowed to modify the induction system.

Hellsmurf · Post by **Hellsmurf** » Mon Jun 14, 2004 2:41 pm

love the analogy there ruchi

RallyMad · Post by **RallyMad** » Mon Jun 14, 2004 7:51 pm

I've got a great example of what Ruchi is talking about.
The laser TX3 (B6 1.6 non turbo) that I have at the moment was modified a little before I bought it, and has what the guys I bought it from liked to call a tuned lenght exhaust. A term I'd never heard before relating to the whole exhaust but only the extractors and I know that it means equalling the distance that air flows from the exhaust ports in an engine so that they all flow equally right, and therefore gain more power (from the bowels if you like_

But anyway my car has a full exhaust with extractors (which I don't trust) into a 2.25 inch pipe to a resonater and 2.5 inch back to a muffler with a 3 inch dump out, now I feel as does my mechanic that this exhaust system is way to big for the stock engine, I have lots of idle issues which I'm sure are caused by this as well. And I also feel that even though the car has great response high in the rev range and seem like it has good torque I feel that I'm losing power compared to if I had a system better suited to my stock engine and induction, which will also be suitably modified in the futuer

G_A_V · Post by **G_A_V** » Mon Jun 14, 2004 11:42 pm

if you get a high flow cat system ,you should be able to use the unique front pipe. the reason its not recommended for non mivecs, is because when installed on my car, we noticed the cat inlet was slightly smaller then that used on the mivecs (this may of been a doggy compliance place sticking on any cat, because the cat needs to be changed when compliance, and many doggy places weld together anything). So anyways when installed with the slightly smaller cat inlet it created a lot of turbulence and ended up loosing a kilowatt and a couple more when the ecu adjusted.
Basically the unique front pipe should work for non mivec (6 cyl) engines, because the front pipes on the mivecs, and non mivecs are exactly the same
So hopefully when the tax man pays me a visit i will invest in unique front pipes, high flow cat, and rear muffler. Then ill be able to show you dyno chart differences with these modifications done on a non mivec.

ellusion · Post by **ellusion** » Tue Jun 15, 2004 1:46 am

whats the size of the piping going to the cat?

If it's 2.5" then it should fit perfectly with a 2.5" high flow cat right?

RichardH · Post by **RichardH** » Tue Jun 15, 2004 10:37 am

ruchi wrote:a restrictive exhaust system is like being constipated.

Okay. Now I'm REALLY getting worried about you East Coast lads!!

- Rich

GPXXX · Post by **GPXXX** » Tue Jun 15, 2004 11:03 am

RichardH wrote:
ruchi wrote:a restrictive exhaust system is like being constipated.
Okay. Now I'm REALLY getting worried about you East Coast lads!!

- Rich

don't mind him richard, he's only speaking on his own behalf...

ruchi · Post by **ruchi** » Wed Jun 16, 2004 6:29 pm

So Mikey, should I come up with an analogy for you getting your engine "blown"? (turbo)

GPXXX · Post by **GPXXX** » Wed Jun 16, 2004 9:59 pm

no, we don't want to hear about your sexual fantasies...

hnm738 · Post by **hnm738** » Thu Jun 17, 2004 9:18 pm

i got a sports muffler
i went to do my exhaust today
and the guy told me if i was to change to a 2.5inch exhaust from cat to my muffler it makes no power or performances difference
is this true?

Jono · Post by **Jono** » Fri Jun 18, 2004 12:12 am

hmm so wats a laxative then?

Jono

GPXXX · Post by **GPXXX** » Fri Jun 18, 2004 11:23 am

a chemical to ease anal exploits...

YMY671 · Post by **YMY671** » Fri Jun 18, 2004 11:26 pm

guys where can you buy aftermarket exhuast?
i havent seen any for fto at all...besides custom ones.
i actually want the hks superdragger/5zigen/apexi N1
but what is the 5zigen like?

EURO · Post by **EURO** » Sun Jun 20, 2004 7:37 pm

depends where u are from mate?

in melbourne places like hypertech stock the N1 apexi exhaust for FTO, and im sure there are many others....

or go to www.perfectrun.com.au - they stock the n1 as well, at the best price ive seen. I think they are in syd.

GPXXX · Post by **GPXXX** » Mon Jun 21, 2004 11:35 am

YMY671 wrote:but what is the 5zigen like?

sounds like HEAVEN!!