exhaust designs...do turbo's require any back pressure..??

[Gordy]

Mikejc wrote:
ENSMR2 wrote:
It's not different if it's been done though.

Boot/rear bumper exit would be different or even engine lid exit.......


Engine lid exit has been done

Mikejc


Yeah?

Anyone got any pics?

Like the man said, got any pics?

[Gordy]

Idea for you: Split the exit from the turbo: route the main feed down to a normally positioned exhaust, and feed the wastegate output (straight-through and unsilenced) through the side exit. You'll get 'normal' sound while pootling around and a roar when the wastegate opens. Woo hoo

[jdbecks]

the turbo causes enough turbulant air to worry about back pressure....ill find the link on www.mr2oc.com where they say that with dyno proofed that u dont require the back pressure on a turbo

[CosmosblueMR2]

Idea for you: Split the exit from the turbo: route the main feed down to a normally positioned exhaust, and feed the wastegate output (straight-through and unsilenced) through the side exit. You'll get 'normal' sound while pootling around and a roar when the wastegate opens. Woo hoo

AndyF has this

[Steve W2]

Or split into two pipes and have an side exit exhaust on both sides of the car I like the sound of that.

I also think some of you are missing the point by stating the one other person on the forum that has done each type of mod. He said he wanted something different, as in different from the norm.

That's entirely different to meaning unique and never done before.

[skinthespin]

why do the seals wear out with no back pressure?

[THE DUKE]

why do the seals wear out with no back pressure?

Thier flippers get tired.

[70by]

seals wearing out! back pressure needed for turbos! what have you lot been smoking get the gas out quick as possible,a free turbo is a happy turbo

[Al-sw20]

seals wearing out! back pressure needed for turbos! what have you lot been smoking get the gas out quick as possible,a free turbo is a happy turbo

I concur.

[jonb-]

Holdddd on.

Now i'm not the most learned chap when it comes to engines but i'm pretty sure, on NA's at least, you need some """backpressure""" not because backpressure is good, but if you go too large on your tube you lessen / lose the scavenging effect because the gasses are moving slower in the large tube (nothing to do with backpressure hence the """). Backpressure will exist in any system unless it's just a straight pipe.

Now, i'd assume this is most important off the cylinder on an NA car, so in the manifold. The only problem with our turbo cars is the f**koff turbo creating huge backpressure and runing the airflow, so there goes the main benifit of having a tuned exhaust size and length.

Post turbo it's just about getting the gasses out as quickly as possible, if the turbo is having to exhaust into a +ve pressure it's only going to slow it. Which is bad.

What and why this does to the seals i don't know, though i tend to believe what Jonno says. Perhaps you care to explain Neil?

[ENSMR2]

Holdddd on.

Now i'm not the most learned chap when it comes to engines but i'm pretty sure, on NA's at least, you need some """backpressure""" not because backpressure is good, but if you go too large on your tube you lessen / lose the scavenging effect because the gasses are moving slower in the large tube (nothing to do with backpressure hence the """). Backpressure will exist in any system unless it's just a straight pipe.

Now, i'd assume this is most important off the cylinder on an NA car, so in the manifold. The only problem with our turbo cars is the f**koff turbo creating huge backpressure and runing the airflow, so there goes the main benifit of having a tuned exhaust size and length.

Post turbo it's just about getting the gasses out as quickly as possible, if the turbo is having to exhaust into a +ve pressure it's only going to slow it. Which is bad.

What and why this does to the seals i don't know, though i tend to believe what Jonno says. Perhaps you care to explain Neil?

Like the old garden hose. Mahoosive hose and the water trickles out. Smaller and it shoots out.

Theres is certainly a lot more to it then just wacking on a large exhaust.

In general 2.0-2.3l cars shoudl go for 2.75 to 3.0 inch exhausts. Thats for 120-150bhp per litre. When you get to 200-250bhp per litre you can increase by 0.5 to 1 inch. Thats a rough guide though.

This is why I always recommend custom exhausts. It can be built to perform with what you require.

[Steve W2]

but if you go too large on your tube you lessen / lose the scavenging effect because the gasses are moving slower in the large tube

Thus creating a back pressure

I agree totally with everything in else in your post though. NA engines often use 'pulse tuning' to extract the most from an engine. The pulses on some race cars are timed with the opening/closing exhaust valves.

[70by]

i thought we were talking about turbo engines where off boost performance isn't really a factor,scavenging dosent really come into effect untill an engine is stretching its legs, past 4k as a genaral rule, and then its as much to do with valve overlap as exhaust design.

[skinthespin]

Must admit I had always thought on a turbo car the least backpressure the better, hence some of the early turbo racing cars had nothing after the turbo, noise limits were not an issue back then either.

I still cant get my head round why the seal life would suffer though?

On our NA engines our pipe lenghts are tuned very carefully to help scavenging/noise etc, but a turbo is something completely different.

[ENSMR2]

I still cant get my head round why the seal life would suffer though?

Yes, very nice of someone to mention it without explaining.

I know a impreza tuner who did various tests on different size exhausts. I remember him saying a while back it'd be great to run with no exhaust whatso ever

[jdbecks]

my mate has a rev2 and has took his exhaust off..after his gutted cat....he has no problems with it, not as loud as u think and dont suffer no hesitation or anything...the turbo spools up like lighting and u can here the turbo really well

dont flame me about him not having an exhaust its not me lol

[ryan]

If a turbo requires little backpressure, why do all rally cars have tiny 'pea shooter' exhausts?

[jdbecks]

noise restrictions? or more ground clearance?