Measured Exhaust Manifold Pressure

[Ziggo]

So despite my extreme fail, I managed to capture some data up to 4k RPM. I didn't have the go-pro close enough to the monitor so I got crappy resolution, and it was upside down because I am a nub. Since I lack the video editing SW to flip it back over, so shitty screen caps it is.

Initial Impressions: The Gauge Display on ATR does not update fast enough to really catch spool, even though the dyno was loading me less than the street and I was spooling slower than normal. The go-pro was running @ 60fps, and it was ~6 frames between updates on the computer, which makes me doubt what the latency really is.

Seems like the pressure differential really starts to grow at the 3900RPM, going from a fairly constant -3.5PSI to -6.8PSI and then again jumping at the 4130 point to -10.28PSI. Unfortunately I don't have data to redline because of a CAI + rain + MAF issue. But its clear that at 4000RPM the backpressure is already growing substantially, requiring negative cam overlap to combat reversion. It also appears that with this turbo, you never really get out of the negative pressure differential zone where you would want overlap for scavenging. I wouldn't expect results for an ATP GT30 series turbo to be much different as the hotsides are comparable and the exhaust wheel isn't THAT much bigger. Probably follows the same curve with just a few PSI difference, but until one is measured its up in the air.

Corresponding log attached. You can see in the last line the MAF railed out, and AFRs going super rich. My suspicion being that water was getting on it, causing it to cool abnormally, supported by the fact that when the MAF sensor was removed it was covered in water....

10PSI Backpressure, 6.5PSI Boost, 2768RPM


15 Psi Backpressure, 11.6PSI Boost, 3227RPM


20 Psi Backpressue, 16.33PSI Boost, 3553RPM


25 Psi Backpressure, 18.2PSI Boost, 3900RPM


30 Psi Backpressure, 19.72PSI Boost, 4130RPM

[Ziggo]

Post reserved for same measurements with JBR 3.5" SRI

[Lex]

Where were you taking the measurement?

[Ziggo]

Originally Posted by Lex Where were you taking the measurement?

Exhaust manifold collector

[superskaterxes]

im going to tackle this next week. you peaked my curiosity but i believe your measurements are somewhat skewed because you should have your largest pressure right at peak spool/tq where the turbo is trying to overcome its inertia to spool. once it spools and the air is flowing free-er through the turbine/wg the pressure should subside or atleast not grow as a linear rate.

[Ziggo]

Originally Posted by superskaterxes im going to tackle this next week. you peaked my curiosity but i believe your measurements are somewhat skewed because you should have your largest pressure right at peak spool/tq where the turbo is trying to overcome its inertia to spool. once it spools and the air is flowing free-er through the turbine/wg the pressure should subside or atleast not grow as a linear rate.

I'll be very interested in your results but I highly doubt you will see this behavior. I am 99% sure you will see the backpressure grow as the RPMs climb.

[superskaterxes]

Originally Posted by Ziggo I'll be very interested in your results but I highly doubt you will see this behavior. I am 99% sure you will see the backpressure grow as the RPMs climb.

no no no i def agree it will grow but im just saying how it grows from 2k to 4k wont be the same as 4k to 6k.


im interested to see how my much larger turbine wheel on the smaller ATP housing will perform.

[Ziggo]

Originally Posted by superskaterxes no no no i def agree it will grow but im just saying how it grows from 2k to 4k wont be the same as 4k to 6k. im interested to see how my much larger turbine wheel on the smaller ATP housing will perform.

Yeah I have no idea what the profile will look like. I certainly hope it does not continue to climb at such a high rate, after it reaches full spool hopefully it will increase at a much more linear rate.

[Mizzle]

Originally Posted by superskaterxes im going to tackle this next week. you piqued my curiosity ...

fixed.

[Lex]

So that's just a standard differential pressure gauge measuring pressure at turbine inlet WRT atmosphere correct?

[Ziggo]

Originally Posted by Lex So that's just a standard differential pressure gauge measuring pressure at turbine inlet WRT atmosphere correct?

Yes, it is measuring gauge pressure at the inlet. It has no capability to read vacuum.


Zigatapatalka

[Lex]

Originally Posted by Ziggo Yes, it is measuring gauge pressure at the inlet. It has no capability to read vacuum. Zigatapatalka

There isn't much you can do about the size of the turbine but I wonder how much backpressure the turbo-back is adding. It would be very cool if you put that gauge post turbine so that you knew how much the turbine contributes versus the rest of the exhaust.

[Tomas]

I'd be surprised to see more than 2-3 psi post turbo pressure on the exhaust at red line.

To flip the video 180* get windows live movie maker here.

http://windows.microsoft.com/en-US/w...es/movie-maker

[Ziggo]

Originally Posted by Tomas I'd be surprised to see more than 2-3 psi post turbo pressure on the exhaust at red line. To flip the video 180* get windows live movie maker here. Windows Live Movie Maker - Windows 7 features - Microsoft Windows

Thx for the link, I'll try it out.

I tried to pull the second 02 bung out to verify threads but that sucker is seized in there. and its in a spot I cant use a deadblow. Sprayed some PB on it and I'll try again later. Considering buying something like this Since I don't think the tire pressure gauge has fine enough resolution to make it work and some brief shopping has a 0-15psi gauge alone running $30

S And G Tool Aid , 33600 Exhaust Back Pressure Tester

[Lex]

Or just pull the exhaust off and measure in the same spot

[Mizzle]

Originally Posted by Ziggo Thx for the link, I'll try it out. I tried to pull the second 02 bung out to verify threads but that sucker is seized in there.

You could drive it around to heat it up, then hit it with a can of air held upside down... can break it free sometimes.

[Ziggo]

Originally Posted by Mizzle You could drive it around to heat it up, then hit it with a can of air held upside down... can break it free sometimes.

Thx for the suggestion, but the car is actually in-operable right now while I modify a couple pipes for the 5th port.

[silvapain]

Sounds like the BNR S3 needs a larger A/R @Ziggo.

[Mizzle]

Originally Posted by Ziggo Thx for the suggestion, but the car is actually in-operable right now while I modify a couple pipes for the 5th port.

Torch and canned air

[Dash08]

Subbed for results of further testing. This is very interesting.

[Ziggo]

Originally Posted by silvapain Sounds like the BNR S3 needs a larger A/R @Ziggo.

No Doubt. Car is crazy constipated.

@Tomas the link you sent me only works for windows 7. I looked around for an xp version but couldn't find one. Windows movie maker doesn't process .mp4s

The videos are not really worth it anyway. Just quick pulls and @JacksonMS30 telling the dyno operator all about @djuosnteisn methlocking his motor.

[silvapain]

I'm not up to speed on those BNRs... are they stock turbine? What actually is the A/R?

[Ziggo]

Originally Posted by silvapain I'm not up to speed on those BNRs... are they stock turbine? What actually is the A/R?

They have a 2871 turbine on them. He machines out the area around the turbine but does not make any other changes.

I measured it before at .57 or so. Not the most exact measurement, but I trust it to within .05, which makes it roughly comparable to the ATP housings.

[Lex]

A nice conical port job on the housing right after the turbine could yield some improvements. I am very curious how well an aftermarket high flow cat flows versus the OEM which has a much larger cross section but probably offers more restriction.

[Dano]

Originally Posted by Ziggo They have a 2871 turbine on them. He machines out the area around the turbine but does not make any other changes. I measured it before at .57 or so. Not the most exact measurement, but I trust it to within .05, which makes it roughly comparable to the ATP housings.

I was trying to find the hotside AR of the ATP 2871 but can't find it anymore...Regular Garrett 2871s are a 64 AR but IIRC the ATP version is .55.

is this correct?

[EdgeAutosport.com]

Originally Posted by Dano I was trying to find the hotside AR of the ATP 2871 but can't find it anymore...Regular Garrett 2871s are a 64 AR but IIRC the ATP version is .55. is this correct?

Yes .55 sounds correct, ATP has told me at one point or another it was .72 but I dont think the lady knew what she was talking about lol

[Dano]

LoL @ .72 AR...I wish.....well maybe I don't...how about .64 just to keep things exciting and responsive for a 53.85mm turbine wheel.

[djuosnteisn]

Ziggo, if your going to measure the exhaust restriction, you should try to measure it as close as possible to the turbine outlet. The 2nd o2 sensor will be a ways away, and may only show like 2/3 what the actual pressure is presented to the turbine outlet.

PITA, but i suppose we could just infer what it would be by the length of pipe before and after the spot you measure it. That would probably be close enough.


Great testing man!

[Ziggo]

Originally Posted by djuosnteisn Ziggo, if your going to measure the exhaust restriction, you should try to measure it as close as possible to the turbine outlet. The 2nd o2 sensor will be a ways away, and may only show like 2/3 what the actual pressure is presented to the turbine outlet. PITA, but i suppose we could just infer what it would be by the length of pipe before and after the spot you measure it. That would probably be close enough. Great testing man!

I think you misunderstood the location of my second port. The Cobb DP has 2 ports in the bell housing that bolts to the hot side, and then a third downstream. I would be using the second bell housing port to make the measurement, ~4" from the turbine.

A third sensor post cat in the stock narrowband would be interesting, but I doubt it's more than 1psi at that point and I think I would need an expensive gauge to measure that accurately. It would really just be an engineering exercise to see exactly how much backpressure a high flow cat adds to the system.


Zigatapatalka

[djuosnteisn]

Ah, perfect. Yea, i thought you were using the narrow band o2 bung. Eager to see results so we can see what kind of pressure ratio there is across that hot side.

[boostftw1]

When boost pressure > exhaust pressure = crossover and you can really take advantage of cam overlap. Small 4 cyl acts like large NA V10 . That's how 1.6L 4cyl make 1000hp. But only for 2000RPM

2 to 1 crossover ratio is Heaven like the F1 cars of the 80s