apollo
08-14-2010, 04:51 PM
Alright, so I recently installed one of Autometer's fancy electrical boost gauges on my car (the one that comes with a MAP sensor). At full throttle, it shows 11psi. Okay, fine. However, I also have an Anderson Ford Motorsport PMS which also has a MAP sensor (the exact same GM-type 3 bar MAP sensor as the Autometer uses) and it only shows 9psi. In addition, the readings at idle and low speed are considerably different between the two.
The problem here is obvious, in that the PMS is only tuning the fuel, timing, etc. for 9 lbs of boost when there is actually (we'll assume the Autometer is correct...) 11.
So I thought a simple test would be to swap out the MAP sensors, since they are again, the exact same GM 3 bar style. So I did that... and got the exact same readings as before. I tested the vacuum line going to the PMS MAP to make sure it didn't have any leaks, and it did not.
So I've swapped the MAPs back to their original places, and now the Autometer seems to be really messed up. It reads around 0 at idle, while the PMS reads about 14 in. of vacuum, which is about where it was before. ??? Am I missing something really stupid here? I remember something in the PMS instructions saying that they wanted you to keep the MAP located as close as possible to the PMS itself, so I do have a fairly long vacuum line feeding it, but I don't see how that should make any difference. Both vacuum lines (PMS and Autometer) originate at the intake manifold... of the same engine... ha yeah I dunno. :confused:
The problem here is obvious, in that the PMS is only tuning the fuel, timing, etc. for 9 lbs of boost when there is actually (we'll assume the Autometer is correct...) 11.
So I thought a simple test would be to swap out the MAP sensors, since they are again, the exact same GM 3 bar style. So I did that... and got the exact same readings as before. I tested the vacuum line going to the PMS MAP to make sure it didn't have any leaks, and it did not.
So I've swapped the MAPs back to their original places, and now the Autometer seems to be really messed up. It reads around 0 at idle, while the PMS reads about 14 in. of vacuum, which is about where it was before. ??? Am I missing something really stupid here? I remember something in the PMS instructions saying that they wanted you to keep the MAP located as close as possible to the PMS itself, so I do have a fairly long vacuum line feeding it, but I don't see how that should make any difference. Both vacuum lines (PMS and Autometer) originate at the intake manifold... of the same engine... ha yeah I dunno. :confused: