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3.5 Inch To Big?

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ClutchBurndout-:( Grand Master

ClutchBurndout-:(

Posted
Posted

hey all, this is more a "just curious" topic, but i purchased a car (havnt picked it up yet) and the car has a 3.5 inch zorst with a stock turbo, now in the past ive had a 3 inch zorst on the same system and found it enough, but will 3.5 inch be worse for the performance of the car? to me it seems like there wouldnt be enough back pressure.

Anyway, i guess the MAIN question is, how much of a drop in perfomance will there be with this exhaust? should i invest in a 3inch?

stock PSI to BTW

cheers

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ClutchBurndout-:( Grand Master

ClutchBurndout-:(

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It will not hinder performance.

EPA issues however are most likely.

sound or pollution?

An exhaust CAN'T be 'to big' UNLESS you are going to give the exhaust 'to Big Al, your mate'.

Otherwise it is 'too big'.

But in this case, it isn't.

:P

i dont get it

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gwilkinson34 Collaborator

gwilkinson34

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Posted
sound or pollution?

i dont get it

Lol. 'to' and 'too' - two (hehe) different words.

The problem will be with volume, but I wouldn't worry about it (unless you get defected).

The size shouldn't make any difference to emissions as long as there is still a cat.

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ClutchBurndout-:( Grand Master

ClutchBurndout-:(

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Lol. 'to' and 'too' - two (hehe) different words.

The problem will be with volume, but I wouldn't worry about it (unless you get defected).

The size shouldn't make any difference to emissions as long as there is still a cat.

no i don want to take the cat out, srsly, i dont want the extra 500rwkw from taking the cat out, its just to fast for me, so ill leave it in.

i was under the impression that you need some sort of back pressure, but iono

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gwilkinson34 Collaborator

gwilkinson34

Posted
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no i don want to take the cat out, srsly, i dont want the extra 500rwkw from taking the cat out, its just to fast for me, so ill leave it in.

i was under the impression that you need some sort of back pressure, but iono

I believe the extra 500rwkw will make it too fast for you.

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ClutchBurndout-:( Grand Master

ClutchBurndout-:(

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turbo engines are rather different to natro engines when it comes to exhaust requirements. as has been said, you won't notice any difference between a 3" and 3.5" system. if it was on a NA car, then it would be a totally different story

ok, good thanks! :P

i dont realy care about the size, i just didnt want it to be any worse than a 3 inch, which i beleive is optimal for a stock turbo.

I believe the extra 500rwkw will make it too fast for you.

is that all you picked up? lol what about - don, srsly or iono, but its good to see u picked up a missing "o"

cheers mate :angry:

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gwilkinson34 Collaborator

gwilkinson34

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As far as I'm concerned any of those 'made up' internet slang words mean you are speaking another language.

But mix up your 'to, too, two' or 'you're, your' etc while attempting English and it's just plain slack. :P

But srsly, your exhaust is fine.

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ClutchBurndout-:( Grand Master

ClutchBurndout-:(

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As far as I'm concerned any of those 'made up' internet slang words mean you are speaking another language.

But mix up your 'to, too, two' or 'you're, your' etc while attempting English and it's just plain slack. :P

But srsly, your exhaust is fine.

hehe ok cheers mate

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slo_sprint Apprentice

slo_sprint

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Posted

It won't decrease performance, on engines with forced induction the less exhaust restriction the better.

My 33 had a 3.5" system with a stock turbo and very few mods and it was pretty damn loud (didn't have a cat or any mufflers bar the cannon though), did sound mint but.

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discopotato03 Grand Master

discopotato03

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Provided you have control of the fueling and timing it shouldn't be a problem , noise and cops aside .

The theory is that the best exhaust is no exhaust behind a turbocharger which obviously isn't going to cut it in a road car .

The turbo rally people like to start out big behind the turbo and step down in stages on the way to the back . What this is said to do is maintain gas speed in the exhaust system as the gas cools and contracts so to speak .

Its a way of having a large volume behind the systems chief restriction , all gasses are channelled and accelerated into the turbine housing , so the red hot gasses have room to expand into . The way to drive the turbine is to have hot gas at speed on one side and a large volume to spread out into on the other side .

As the gas cools it wants to slow down if the exhaust tract is the same all the way to the back , if it slows down too much you can have reversion issues if say the turbo/exhaust manifold/ports/valves/cams are sized to make high rev grunt .

So , the way to keep it moving is to step the tube size down in stages so that the gasses maintain some momentum and velocity .

My old dinosaur Subaru RX Turbo (1.8L 2 valve tiny port flat four GT2554R turbo) has a 3" tube from the turbo to the back of the gearbox and 2 1/2 from there . Its surprisingly quiet but both mufflers are in the 2 1/2 section behind the 3" cat .

It still has its AM radio tech computer and suffers no reversion crap/no pops spits OR drones anywhere .

I suggest that if you have to do something to reduce noise start at the back , its the cheapest easiest way that gives the least restriction in an exhaust system . Car manufacturers having been doing precisely this for some years now .

A .

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ClutchBurndout-:( Grand Master

ClutchBurndout-:(

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Provided you have control of the fueling and timing it shouldn't be a problem , noise and cops aside .

The theory is that the best exhaust is no exhaust behind a turbocharger which obviously isn't going to cut it in a road car .

The turbo rally people like to start out big behind the turbo and step down in stages on the way to the back . What this is said to do is maintain gas speed in the exhaust system as the gas cools and contracts so to speak .

Its a way of having a large volume behind the systems chief restriction , all gasses are channelled and accelerated into the turbine housing , so the red hot gasses have room to expand into . The way to drive the turbine is to have hot gas at speed on one side and a large volume to spread out into on the other side .

As the gas cools it wants to slow down if the exhaust tract is the same all the way to the back , if it slows down too much you can have reversion issues if say the turbo/exhaust manifold/ports/valves/cams are sized to make high rev grunt .

So , the way to keep it moving is to step the tube size down in stages so that the gasses maintain some momentum and velocity .

My old dinosaur Subaru RX Turbo (1.8L 2 valve tiny port flat four GT2554R turbo) has a 3" tube from the turbo to the back of the gearbox and 2 1/2 from there . Its surprisingly quiet but both mufflers are in the 2 1/2 section behind the 3" cat .

It still has its AM radio tech computer and suffers no reversion crap/no pops spits OR drones anywhere .

I suggest that if you have to do something to reduce noise start at the back , its the cheapest easiest way that gives the least restriction in an exhaust system . Car manufacturers having been doing precisely this for some years now .

A .

thanks for the info, very helpful, so with the 3.5 system in there with stock dump and front pipe, its not helping it i assume haha, but i will invest in a 3 inch bellmouth for the dump/front.

i dont have an issue with sound at all, its quite quiet actualy...

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mad082 Grand Master

mad082

Posted
Posted
so ive heard

What im wondering will a 3 inch dump/front pipe into 2 3/4 catback be aiight..is there any real point buying a whole system for 1/4 of an inch?

Or will i be captain sloooow.........

the only place you may lose some power is high up in the revs. general driving around and even just reving up to around 5000rpm probably won't make a scrap of difference. anything above that i think you would have to put it on a dyno to see the difference in power. don't think you'd notice the power when driving it. if you were aiming for 250kw+ then it might be worth going 3" though.

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75coupe Grand Master

75coupe

Posted
Posted

so if you were after more responsive midrange power the 3.5" exhaust is too large, is that what people are saying?

I was told by a tuner that a 2.5" custom made exhaust would be better than my 3.5" hks, this is what I was told when I told him I wanted to get a tune done for a HKS2835 with supporting mods...

I did say I was after good midrange response, and that I was not interested in ultimate peak power.

I didnt know wheather to trust him or not?

this is on a 33gtst

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