exhaust manifold pressure...

[Homemade WRX]

I was curious to see how the turbocharged teams are measuring/calculating there exhaust manifold pressures.
I know you can use the first law of thermo for it. I also know that there are back pressure sensors on the market. I am curious to see what other teams may have found and what they preffer. Also the accuracy differences they may have found using sensor vs. paper http://fsae.com/groupee_common/emoticons/icon_wink.gif

[Homemade WRX]

I was curious to see how the turbocharged teams are measuring/calculating there exhaust manifold pressures.
I know you can use the first law of thermo for it. I also know that there are back pressure sensors on the market. I am curious to see what other teams may have found and what they preffer. Also the accuracy differences they may have found using sensor vs. paper http://fsae.com/groupee_common/emoticons/icon_wink.gif

[Homemade WRX]

does no one care about there manifold pressure? or maybe the right people haven't read yet

[VFR750R]

It can be important and interesting on a turbo engine to see what's going on. The easiest way is to weld a bung on the exhaust that you can fit a flared copper line. Attach several inches of copper then standard nylon hose or whatever to a pressure sensor. The copper line obviously for heat transfer issues on the exhaust. No specail pressure sensors are required, just one that reads approx 0-25psi

[Homemade WRX]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by VFR750R:
It can be important and interesting on a turbo engine to see what's going on. The easiest way is to weld a bung on the exhaust that you can fit a flared copper line. Attach several inches of copper then standard nylon hose or whatever to a pressure sensor. The copper line obviously for heat transfer issues on the exhaust. No specail pressure sensors are required, just one that reads approx 0-25psi </div></BLOCKQUOTE>
yeah, I had thought of trying that method (along the lines of the budget) but also had looked into the types used for diesel applications. What kind of pressure ratios were you guys seeing on you various 600 turbos?

[VFR750R]

I think the first time we looked at that was 04 (after I graduated) so I'm not really sure but I think around 1:1 or slightly higher on the exhaust side. I think most people would agree that that is typical of a road race setup.

[Homemade WRX]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by VFR750R:
I think the first time we looked at that was 04 (after I graduated) so I'm not really sure but I think around 1:1 or slightly higher on the exhaust side. I think most people would agree that that is typical of a road race setup. </div></BLOCKQUOTE>
hmmm, interesting. I'm use to seeing the drag side of the house being a I work at a dyno shop. I'm use to specing out turbo's that operate at ratios of up to 4:1...most are around 2-2.5:1...
the 1:1 would be much more forgiving on our NA designed cams.
I'm going to be interested to see what I find.

[raska]

Have you simulated it at all? Ours show a high of 4:1 in the primaries, down to 3:1 entering the secondaries. We have yet to measure this though.

[Homemade WRX]

I haven't simulated it yet. I'm still trying to get ahold of our school's virtual 4 stroke software. It's old, Version 5....I also haven't run the numbers on it yet, as I really don't know the VE's of our motor. I will soon though http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

[VFR750R]

Wow, I would have never guessed 4:1. I mean that's higher then the total pressure ratio of the compressor from atmosphere on almost all drag race applications. That would put exhaust pressure at over 100psi??!! Maybe I misunderstood your question. I was refering to intake to exhaust pressure ratio not compressor pressure ratio; since we were talking about measuring exhaust pressure.

I've heard of salt flat racers having less then 1:1 with turbine housings larger then the compressor housings!

[raska]

I think I was mixing absolute with gauge pressure since I didn't have it in front of me. If I remember correctly it was just 1.15 tops then. I can't remember the exact parameters used right now, but it would be between 1 and 1.15.

[Homemade WRX]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by VFR750R:
Wow, I would have never guessed 4:1. I mean that's higher then the total pressure ratio of the compressor from atmosphere on almost all drag race applications. That would put exhaust pressure at over 100psi??!! Maybe I misunderstood your question. I was refering to intake to exhaust pressure ratio not compressor pressure ratio; since we were talking about measuring exhaust pressure.

I've heard of salt flat racers having less then 1:1 with turbine housings larger then the compressor housings! </div></BLOCKQUOTE>

sorry, worded a bit poorly...yes, intake to exhaust ratio I would expect to be around 1:1, maybe a bit higher.
I was really asking about both compressor ratio (don't need just found the GT12 & GT15 files and have all I need) and the intake/exhaust pressure ratio too...hence the questioning of measuring exhaust manifold pressure.

I think I got everyone, including myself, confused http://fsae.com/groupee_common/emoticons/icon_razz.gif