Screamer pipe

[garagestmarien]

Don't want to cause an argument here but I'm afraid your wrong Sleeper.

BOV's or dump valves whether recirculating or to atmosphere are there to protect the turbo.

Without one, when you close the throttle there is nowhere for the gas to go, but the turbo is still spinning and trying to make boost. So what happens is that the turbo stalls. Apart from this causing turbo lag on gear changes (the turbo has to spool up again) the inlet vane is pushed hard against the bearing and will cause premature wear.
So the BOV allows the turbo to keep spinning without pressure, so that a quicker response is gained between gear changes.

Again with the screamer pipe (I think people are getting confused because of it's name - so lets call it a waste gate pipe), as I stated in an earlier post, I am referring to an external waste gate and with this set up the waste gate exhaust enters the main exhaust at right angles and therefore must disrupt the exhaust flow. Don't forget, we don't want any back pressure on the turbo exhaust.
Also as I stated before, the fuel system on my car doesn't have a lambda sensor, therefore using a "waste gate" pipe will not have any effect on the fueling.
Perhaps on an internal waste gate turbo and on systems using lambda sensors the previous points posted are a good argument.

So once again (depending on engine set up) I think a separate pipe for the waste gate would increase power and again with it's own silencer.
I'm not interested in noise but power.

John

[SLEEPER]

I dont think either of us is wrong wrong I think we are both right.
With the screamer pipe, you are referring to a system wihere the angle is 90 degrees and would cause back pressure on the turbo . My post only refers to a custom designed one off straight through exhaust ( which I have)
Yes of course bovd & recircs protect the turbo but they also must control the mixture as well .

[garagestmarien]

Okay,

The BOV doesn't have any effect on the mixture for injection, perhaps it does on carb's but I've never had anything to do with them.
On the injection, the fuel is calculated before the turbo and only on the amount of air entering.
On mine using a recirculating BOV (factory Bosch) and a race twin piston dump to air type, there is no different reading on the mixture.
Well not entirely true, my mixture with the race BOV is more stable because of the airflow meter not being disrupted.

Your exhaust system.
Is there any noticeable noise increase using the straight through system and is it stainless or mild steel.
I am contemplating building a straight through in stainless using middle and end silencers, system size from the turbo approx 75mm and mandrel bent tubes, so only joints are the silencers.
I was wondering about the turbo whistle though.
AND I AM GOING TO BUILD A SEPARATE WASTE GATE PIPE WITH SILENCER, BECAUSE I THINK IT CAN ONLY HELP MY SYSTEM.

John

[SLEEPER]

your set up is different to mine and i am sure this means different rules apply and you are far more likely to know whats right for your car than I am
On mine the exhaust sytem is stainless and has been designed from the mainfold back . It is 80mm and virtually straight back to the rear box because on my car ( a Nissan stagea with a RB26dett engine) thats the natural shape of the pipework. Because it is large and straight through ( to the rear box) and the turbos waste gases join at a better angle than 90 degrees I dont think I have back pressure issues.
Whilst I am not running silly boost it is above standard level and I was advised the recirc valve should be replaced with twin BOVs ,

Re noise Yes it is loud, Infact it is probably too loud up to 3500rpm when the turbos come in . It then gets quieter because the exhaust is directed through the turbos and then re enters the exhaust in a different way. I cannott explain why but it really does make a noticeable difference and is weird the first time you experience it.