|
Title: Pressure difference at WOT between pre and post-throttle MAP. Post by: rnagy86 on March 01, 2016, 09:09:54 AM Hi
Today I noticed something which is as follows. At WOT i noticed that my pre and post throttle MAP sensors read differently, at higher pressures, to be precise the post throttle MAP reads 150-200kPa less than the pre-throttle one. Both sensors are calibrated correctly and are verified with a hand-pump. As far as I know a pressure difference is normal, but since i am not a pro I wonder what difference is mostly normal and I wonder if too much or too less of a difference indicates something, like a too small throttle valve being a restriction would cause higher readings due to pressure building up or something. Of course this might have an influence on fuel pressure as well because the FPR uses a post-throttle reference line. Sorry if this is a stupid question, I am just cuorious :) Thanks Title: Re: Pressure difference at WOT between pre and post-throttle MAP. Post by: Snow Trooper on March 02, 2016, 10:22:16 AM Maybe something is setup wrong with sensor scalings? I have seen a lot of cars miss reading pressure on 4 bar code. The wrong values were put out when everyone first started to do them.
Title: Re: Pressure difference at WOT between pre and post-throttle MAP. Post by: rnagy86 on March 02, 2016, 11:02:00 AM I am running the 03K 906 051 4bar map with DSLGRAD=437.5, DSLOFS=31.25.
Title: Re: Pressure difference at WOT between pre and post-throttle MAP. Post by: nyet on March 02, 2016, 11:08:54 AM That drop does seem a bit high. Are you certain the throttle plate is all the way open when you see that difference?
Not familiar with your setup, is the post TB MAP aftermarket? How are you logging it? Are you measuring absolute or relative pressure? Title: Re: Pressure difference at WOT between pre and post-throttle MAP. Post by: rnagy86 on March 02, 2016, 11:17:17 AM That drop does seem a bit high. Are you certain the throttle plate is all the way open when you see that difference? Not familiar with your setup, is the post TB MAP aftermarket? How are you logging it? Are you measuring absolute or relative pressure? I can only be as certain as the ECU tells me which is wdkba=100. It's a 2.7T, the pre-throttle map is what i said in the previous comment and the other one is a VEMS 4bar MAP sensor, which is hooked up to a VEMS ecu in the glove compartment which i use to log dual egt, dual lambda (also feeded to ME7) , oil and fuel pressure, and the MAP of course, this allows me to use my cellphone to display all the variables I want, but anyway, the VEMS MAP value is a MAP value so it is absolute, and their unit is kPa, but that does not really matter at this point. Title: Re: Pressure difference at WOT between pre and post-throttle MAP. Post by: ddillenger on March 02, 2016, 04:35:28 PM ~5 percent yo.
Title: Re: Pressure difference at WOT between pre and post-throttle MAP. Post by: nyet on March 02, 2016, 06:08:09 PM Well.. if you trust the VEMS MAP you can use it to calibrate the pre tb map :)
Or maybe 5% drop even at 100% throttle plate is expected.. Does the % vary with airflow? Title: Re: Pressure difference at WOT between pre and post-throttle MAP. Post by: Snow Trooper on March 02, 2016, 07:51:05 PM I am running the 03K 906 051 4bar map with DSLGRAD=437.5, DSLOFS=31.25. Those settings are correct. What throttle body setup do you have? Title: Re: Pressure difference at WOT between pre and post-throttle MAP. Post by: rnagy86 on March 03, 2016, 12:19:17 AM It's an RS4 throttle body and RS4 intake manifold. But anyway I will keep testing.
|