thelevman

hey guys, im looking to do an exhaust back pressure test (post turbine), im using an external map sensor at the moment with my setup, hence the stock pressure sensor is doing nothing

i was wondering can i set the haltech onboard pressure sensor to barometric datalogging with a 0% correction. give it a vacume line to my dump pipe and then drive it and log the amount in psi it is higher than the current barometric reading?

is there something im missing as to why this couldnt work? id use a boost gauge in the exhaust but id like to have a more accurate idea of whats going on, rather than attempting to see a potentially low psi reading from a crap gauge whilst bouncing around at 150kph

thanks!

C. Ludwig

iTrader: (27)

Could work. How much manifold pressure do you run?

thelevman

25psi, gt37r large street ported 13b. full 3 inch exhaust, just concerned the offset/offset muffler may be causing problems. ive got a new muffler to go on but would like to confirm the issue

C. Ludwig

iTrader: (27)

If you're running 25 psi manifold pressure, you will easily top out the 22 psi onboard pressure sensor. You really should have a sensor that is 50+ psi capable.

thelevman

im running a 5 bar external map sensor. i was just wanting to use onboard pressure sensor as a means of checking exhaust back pressure which will be minimal but we are trying to trouble shoot a power drop problem around 6000rpm.

C. Ludwig

iTrader: (27)

Tailpipe pressure (after the turbo) or exhaust manifold pressure (pre-turbo)? If you're checking pre-turbo, you will need a sensor with 2x+ the range of the manifold pressure. If you're checking tailpipe pressure, it would work well.

thelevman

cool yeap i was testing after turbo pressure
the barometric pressure was reading 14.6psi with ignition on, i tested that it would work by blowing into it and it rose to 15-16psi so that confirmed this test would work

i went out for a spin and the pressure never really grew with it plumbed into the dump pipe
heres a screenshot of it

C. Ludwig

iTrader: (27)

Thanks for sharing. I've had similar low power issues with a customer's car. We've seen as much as 8 psi in the downpipe at 20 psi of boost. We've never fully sorted the issue, but have done some testing with an open downpipe and spool and power were dramatically improved. You're pressure numbers are considerably lower though.