Screamer pipe

[pgarner]

ok like o.g i search for screamer pipe on wikpedia and this came under wastegate

A "divorced" wastegate dumps the gases directly into the atmosphere, instead of returning them with the rest of an engine's exhaust. This is done to prevent turbulence to the exhaust flow and reduce total back pressure in the exhaust system. Divorced wastegate dumper pipes are commonly referred to as "screamer pipes" due to the unmuffled waste exhaust gasses and the associated loud noises they produce.

so would i be right by saying rather than the wastegate sending the exhaust gas down the exhaust . it sends it down a dedicated exhaust pipe

and whats wrong with having a little 1ltr car with a 4" pipe and 6" tail pipe it gives me 15bhp then i get another 10 from the induction kit

your right thou too many people go along with the more noisy the faster it goes





wrapping the exhaust is supposed to lower the under bonnet temperatures

[old-git]

Originally Posted by glaymore

a waste gate and bov serve completely different purposes, the waistgate stops the turbo from delivering to much boost, the bov or recirc valve let off presure on throttle shut situation, to stop the back pressure in the inlet damaging the tirbine in the turbo, as for screamer pipe I'v got no idea what the advantage of one of them would be

Yup, I know that

Probably serves the same purpose as aftermarket BOVs - Lots of noise. Another case of A.F.A.N.S.

[garagestmarien]

Originally Posted by old-git

Yup, I know that

Probably serves the same purpose as aftermarket BOVs - Lots of noise. Another case of A.F.A.N.S.

I agree that after market BOV'S make noise, but like on my engine CX25 GTi Turbo2, the factory recirculating type caused disrupted airflow to the intake. The standard airflow meter is Bosch with the flapper door and when testing the standard dump valve, you could actually see the door being pushed closed for a split second. With a twin piston dump to atmosphere this has been stopped.
However, the new build engine is having a complete new fuel management system, so this won't be a problem.
As for Wiki, it proves my point that more performance can be had by giving the waste gate it's own pipe and I still don't see why, with a good silencer this can't be done and still be quiet.

[pgarner]

Originally Posted by old-git

Yup, I know that

Probably serves the same purpose as aftermarket BOVs - Lots of noise. Another case of A.F.A.N.S.

AFANS???

if the exhaust gases are going down a separate pipe then they would fail emissions due to there being no cat. if you added the cat then there would be no point as the cat would increase the back pressure.

in newer VAG cars 1.8t and 2.0TFSI if a BOV is fitted the cars should overfuel as they are looking for the pressurised air being flowed back into the intake from the DV

[HDi fun]

I like the sound of the CX - one of my favourite cars of all time. I've never driven the turbo but do recall the completely over the top brake response on the more modest 2400cc ones.

Brean fun though, in a quirky kind of way.

[HDi fun]

Originally Posted by pgarner

ok like o.g i search for screamer pipe on wikpedia and this came under wastegate



so would i be right by saying rather than the wastegate sending the exhaust gas down the exhaust . it sends it down a dedicated exhaust pipe

and whats wrong with having a little 1ltr car with a 4" pipe and 6" tail pipe it gives me 15bhp then i get another 10 from the induction kit

your right thou too many people go along with the more noisy the faster it goes





wrapping the exhaust is supposed to lower the under bonnet temperatures

You can't just keep adding up the suggested bhp increases from sucessive modifications as you imply. Thanks, Paul, for clarifying this. The set of equations is nowhere near linear.

BR's take note, noise and performance are totally unrelated.

[waynne]

Originally Posted by HDi fun

BR's take note, noise and performance are totally unrelated.

This applies to mopeds as well as cars.

The Ferrari F40 (or maybe the F50) - I am led to believe has a screamer pipe- which is the third exhaust hole at the rear.

[garagestmarien]

Originally Posted by waynne

This applies to mopeds as well as cars.

The Ferrari F40 (or maybe the F50) - I am led to believe has a screamer pipe- which is the third exhaust hole at the rear.

Correct, that is the F40.

John

[HDi fun]

Come on - let's keep it in perspective. The F40 is producing something appraoching 500bhp, probably using four turbos to assist. There's a lot of opportunity for high back pressure in such an engine.

[old-git]

Originally Posted by pgarner

AFANS???

A.F.A.N.S = All Fart And No Sh*t

[pgarner]

Ahh

[waynne]

You wish you hadn't asked now!

[pgarner]

no i was thining

Another fin something something something

[SLEEPER]

A screamer pipe gives absolutely no benefit other than a noise to frighten old ladies etc

It is on the "exhaust" side of the turbos - The exhaust which is diverted through the wastegate to drive the tubo vanes (and thus produce the boost) has to go somewhere . There are only two choices -Either back into the exhaust or not . The latter is called a screamer pipe .
One side effect of not using a screamer pipe is that with a straight though exhaust in the car it can actually be noticably quieter as soon as the turbos come in . A properly tuned exhaust will also take this into account.
Lastly there is absolutely no point in putting a silencer on a screamer pipe cos the only reason for having it is the noise it makes.

A screamer pipe also has absolutely nothing to do with blow off valves which are on the "inlet" side of the turbos .
These are used because the turbos are driven by the exhaust gas pressure to push extra fuel into the engine.
When you change gear and the revs go down (even momentarily) the vanes simply cant slow down this quickly and would continue to spin at the same speed without the BOV , This would mean overfuelling on a big scale as the boost level ( and therefore the fuel level) would be far too high for the lower revs.
The BOV (or BOVS on a twin turbo) reduce(s) the pressure and therefore stops the overfuelling.
An altenative to a BOV is to have a recirculatory valve that sends the "surplus" gases back to the "inlet" side of the turbo. This works fine and is the set up on nearly all standard cars where the boost is running at fairly low presssue.

However if you raise the boost ( to get extra power) using the recirculating valve method is not always safe because the boost level becomes far more critical and the recirc valves cant always handle the higher pressures.
It is safer to vent the extra gas pressure into the atmosphere direct.
Bovs can be adjusted to make more or less noise. On my car they are only noticeable on full boost and are absolutely silent the rest of the time.
Depends if you want "go" or "show"

Hope this helps .

[waynne]

Very informative Sleeper - thank you.