NZ951

I dont think just yet, Mad still has some explaining to do about how to limit the pressure difference across the throttle plate to 5-10 psi. I think more data and work needs to be done yet.

toddk911

Definately tap AFTER the IC.

Ahmet

I guess this is going to boil down to personal preference.

I have the reasons (that I've listed) for my take. I don't see how I can contribute further to the discussion.
Ahmet

Sam Lin

Nicely laid out Ahmet and Boostguy951, there's no way I'd remove that banjo, response is so much quicker through it than waiting for the manifold a couple feet down the line.

Sam

cpt_koolbeenz

I am also going to tap the hardpipe after the IC... Don't loose response time and see basically the same pressure as the manifold (assuming WOT).

On shifts, (if tapping off the IC line) the wastegate would open (or remain open) until the BOV vents, dumping all the exhaust pressure. Granted that is not very long, but were only dealing with milliseconds between shifts anyway. If I could find the article that talked about it... I would post it.


This topic has also been addressed on Rennlist already (anyone remember the thread title?)

It is basically personal preference... There are pros and cons to either - but in the grand scheme of things, neither will make a big difference.

toddk911

"response is so much quicker through it than waiting for the manifold a couple feet down the line."

I have ran both ways and saw no difference in response. If there was, it was not noticable. And I will allow a little difference in response if I know that when I am running 18psi, I know that 18psi is actually making it's way to the motor and saving my turbo the extra work and heat of trying to make 20 psi, just to get 18 into the motor.

toddk911

"Maybe the above were at least partial the reasons why Porsche tapped the WG control signal where they did." Laust

Or just another de tuning or safety control from Porsche. That way, there is always 1-2psi less in the motor, than the owner thinks.

toddk911

Found this, not sure if it can help with this situation: It is in regards to another type of turbo car, but the formuals might help.

"How does that equate to Horsepower?
A compressor multiplies the intake pressure (Pi) by the compression ratio (Cr) to get Outlet Pressure (Po). Boost (Pb) = Po - Intercooler pressure drop (Pic). The Comp outlet Temp is a function of the compressor ratio and causes those bad effects, like knock. So if we keep the Cr and Pic constant and only increase Pi, we will increase Pb(boost) without a temperature increase. In a stock system with 2.5" upper IC pipes, Pi is at least 2.3 @17psi & 6Krpm.
This gives a Cr = (17+14.7+2.3)/(14.7-2.8) = 2.86
The change in boost dPb = Cr x dPi (change in inlet pressure) = 2.86x1 =2.86 The new Pb is 17+2.86 = 19.9psi.
Using the equations to determine hp, with Pb=17psi,2001cc's, Ev=.85 ,6krpm, Power = 259bhp.
Likewise at Pb=19.9 psi, Power = 283bhp The power gain is 24bhp! (9%)"

Jason_86_951

Response aside, did it make any difference in your boost profile???If so please explain.

Sam Lin

Last time I checked, KLR and stock boost gauge read off the manifold, not the wastegate control line.

Sam

toddk911

"Last time I checked, KLR and stock boost gauge read off the manifold, not the wastegate control line. "

Then in that case the turbo is jsut working harder to get X amount of boost into the manifold. i.e. if both are taken from the manifold, the guage reads 15 psi and 15 psi is getting into the manifold, however, the turbo is generating 16,17,18 psi or whatever it takes to get that 15psi through the IC to the manifold.

turbite

How is this ever not true?

The only time I see the turbo doing extra work is with a leaky wastegate. In my mind, thats more likely to happen when using the intake manifold pressure to close the wastegate, instead of the IC first pipe.

In my car I think the boost controller measures pressure of the IM, yet controls the wastegate via the first IC pipe.

TurboTommy

It is true that your turbo has to work a tad bit harder than what your intake manifold pressure suggests.
But this is obviously a function of the pressure drop through the IC. Where your line is upstream of your boost controller/wastegate combo doesn't change any of that.

Jason_86_951

True but I think it could change your boost curve.
If you took the WG line from the manifold you wouldn't have the WG opening more than you want. Like in higher RPM's when the boost curve starts to drop. The manifold pressure would let the WG close to compensate, instead of the backpressure before the IC keeping the WG open.

NZ951

Assuming the boost curve does drop... shouldnt now with my setup.