No extra boost from mods theory..

[Birnie]

Hi guys,

I've read around and seen from adds on FRONT/DUMP pipes, and also, recently, from adding intercoolers that because of exhaust flow efficency, or cooler temps that your car will be running at higher boost.

Surely this ISN'T correct.

Although I do believe that you are no capable of running higher boost with better efficiency, or less danger, or whatever others reasons. And I agree that you might spool up quicker. They definatley make sense.....

BUT, you must be limited to what your boost controller is set to. I don't care if there's a massive vacuum sucking gases out of your turbo. As soon as it reaches it's set limit, it will hold it there and no further.

So basically, the theory is (in my mind) mod ecerything to make it smoother and cooler but no extra boost will be obtained until you mod or replace the boost controller.

Am I wrong???

Thanks...Birnie

[mupkant]

definition of noobs?

[Bass Junky]

You are wrong.

It is a very well known and accepted fact that when replacing factory dumps/fronts etc. that you will most likely raise the boost that the trubo can supply to the manifold.

Ask any speed shop or techie out there.

I haven't got time to go into specifics, but yes, you can definently make more boost with a less restrictive exhaust.

BASS OUT

[Birnie]

Thanks for the info BASS

Still trying to get my head around things. Thought I was was on a winner there. Doh!

I'll have to keep searching for the more technical answers but that's ok.

Even from reading your reply, "you will most likely raise the boost that the turbo can supply to the manifold". I can accept that, but why should it when it's set to a certain level. Still searching.

Catch ya..Birnie

[b2barker]

The reason you make more boost is because a stockie doesn't have a boost controller, just a wastegate. An exhaust with less backpressure means higher speed exhaust gases, and hence more boost.

[Birnie]

YEAH !

THanks b2barker.

Another pice of the puzzle is filled in.

Didn't have a boost controller to start with.

I need to do a course or something....geeze

[Bass Junky]

That's right.

Most turbos take their boost reading from right at the compressor, and hence the turbo might see 10 psi, but because of restrictions in the system, it might only be able to supply 7 psi to the manifold.

Remove the restrictions (in both intercooler and exhaust) and you get your 3 psi back.

Aftermarket boost controllers can take their reading from anywhere, therefor can regulate boost at the manifold if required, and also manipulate the boost to what they want.

BASS OUT

[qikr33]

if the turbos took their reading from the compressor the boost guage would not read vacuume cos the butterfly in the plenm would prevent this.i think what you guys are saying is that restrictive i/c and piping causes the turbo to run at higher boost that what the manifold is getting its like blowing through a thin straw,your mouth is building more pressure than what is felt at the end of the straw.Therefore if u have less restrictive piping and i/c the turbo is not working harder to reach boost and maintain it.when you boost your car to 12 psi thats the reading u get at the manifold.

[Steve]

Seems like a bit of DIS information here.

Yes a skyline does have stock boost control. The controller is not an adjustable type, just bleeds off xxx amount of pressure (to the wastegate) to generate 5psi(stock) to 5000 rpm, and 7 psi (stock) 5000-7000rpm.

the reason a cat back will raise boost (on stock boost control) is, as mentioned, the drop in back pressure, you should expect around 2psi - if of course you have an EBC it will not make any difference.

Boost is measured from the plenum, boost for wastegate control is usually taken from the compressor outlet, or very close to it - there is a difference.

Stock intercooler can have a massive pressure drop above 6000rpm, as the boost is measured from the plenum, even though the boost guage see xxx psi of boost, the turbo will be producing much higher boost than being measured.

A good intercooler will allow you to run higher boost more safely than the stock intercooler due to a lesser pressure drop over the stock unit, also, it is most likely more efficient than the stock nissan interwarmer, therefore will give power gains at the same boost over the stock unit as well.

Hope that makes sense.