Author Topic: Turbine back pressure  (Read 2425 times)

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SQPerformance

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Turbine back pressure
« on: November 01, 2012, 10:41:48 PM »
Quote from: TainterRacing
I thought I would start this not that I have allot of info but to get all the info we can in one place. I soon should have some good info as I am going to be able to get reading on 3 places on the ex on my brothers MPI starion. I have one in the header and one in the down pipe before the EX-Wastegate is run back in to the turbo and yet another on the Wastegate tube running back in to the down pipe. This is the same header and turbo and intake setup we did the 12.4 at 15psi on and this time we have a wild cly head on there as well as a roller cam. I am looking forward  to getting some good information on back pressure and so on.

In the mean time I thought why not get some info on my 1999 Volvo V70 GLT. So I have put one on my manifold the worst runner to see what it sees and then I am now put on the down pipe as well. Info on the car 100% stock Other then I have a EX Wastegate installed.

1. Motor running like OEM not using the ex-gate I am showing as much as 35-37psi on the EX manifold when I am seeing about 11psi on the intake manifold. SO that’s about a 3.36:1 ratio

2. Next with running both Wastegate I got a high of 27-28psi on the ex manifold and about 9-10psi  intake SO about a 2.8:1

3. I tried to the down pipe out next with it running only the ex Wastegate NO VAC line I have a 15psi spring in there same spring as the other times.  I am only getting about 5-3psi on the intake due to the pressure on the manifold being so high, its over coming the spring. The down pipe is seeing at high rpms about 5psi and at the same time its showing 3psi on the intake side. So I am seeing  more pressure in the down pipe then in the intake.

I will up date this as I get more info please add more!!!!

Quote from: funkyp
Well you are moving more volume through the exhaust than the intake manifold. And with the psi being so low it just makes it stick out. What does the DP/Intake ratio look like at higher boost pressures?

When it comes to the SQ, The turbine housing is the first issue that needs rectified. I know Scott has some good info he wanted to put up aswell as StarquestRescue.

Quote from: funkyp
This an excel I threw together of the power changes from turbine only modifications. I cant thank John enough for doing this. It proves what has being said by a few for MANY years about our cars.

All of these pulls were done with the same 18G @ similar boost levels with minor changes in modifications. (fuel/hardpipes/IC) Now sure, these changes will affect power levels, but I see no reason why they would play a role in powercurve.



Peaky Low end TQ with a low HP plataeu is a perfect example of poor flow/low VE. Ask any performance engine builder. You can see that everytime John increased exhaust flow he traded tq for HP.

SQPerformance

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Re: Turbine back pressure
« Reply #1 on: November 01, 2012, 10:50:43 PM »
Quote from: non-intercooled flatty
Yeah, I've got to make some nice graphs with the data I've collected.

Quote from: non-intercooled flatty

Quote from: funkyp
Too bad we didnt take the time to mess with the ignition timing.

Quote from: non-intercooled flatty
That is a great torque curve.  It needs to be higher, no doubt, but it comes up quick and stays flat.  I'm dropping on the M28 head/schnieder cam combo hopefully this weekend.

Quote from: non-intercooled flatty
One additional thing, the boost pressure was measured at the wastegate line so its reading compressor discharge pressure.  I forgot there is 2 psi of pressure drop across the stock throttle body so the cylinders are only seeing 5 psi of boost pressure.  Should have tapped into the pvc port or HVAC port to measure boost below the throttle plate.

Quote from: TainterRacing
Quote from: non-intercooled flatty
One additional thing, the boost pressure was measured at the wastegate line so its reading compressor discharge pressure.  I forgot there is 2 psi of pressure drop across the stock throttle body so the cylinders are only seeing 5 psi of boost pressure.  Should have tapped into the pvc port or HVAC port to measure boost below the throttle plate.

I forgot about that as well.. I need to see what the drop is. I was able to test my brothers built starion before the tranny gave out on it.
Info.
Header with 1 5/8 ID tube Not equal length 2.5in to 6.5in runners. I made the runners so they all aim at the wastage area and at a 45 degrees from that is the turbo. Has about  3.5inx5inx3.5in plenum. Has a 38mm waste-gate the new tial type. Stage 5 wheel on a .63 A/R Running 14psi at the intake never had more then 3pis over that was from 0-3 more then the intake. I need to see what the pressure drop is on it yet.