in order to prove or disprove a theory i have i need everyone to post 2 numbers.

turn your key so that you have power to the PFC, but dont start the engine.
the numbers i need are:

1. boost/vacuum value
2. altitude you are at ASL

TIA,

 

I will be out tuning my car today and I live at almost sealevel so I will post later today.

 

Vac reading w/ engine off: -35 mmhg

Altitude: 100-120 ft. above sea level





to find you sea level go to:

http://www.topozone.com/

and enter your city in the Place Name Search

 

I got -23 mmHg at 314 ft above Sea Level.

Richard

 

-20 mmhg @ 74' ASL

 

Did some quick research on the way home tonight. Found that my Defi gauge that I stood by is not as accurate as I thought. It read a peak hold of ~14.5 lbs (PFC is set to pri=0.80, sec=0.75), while the pfc read a peak of 0.83 (roughly 12.2 lbs). Above is my vacuum at feet above sea level with engine off. Just so you have some more numbers to play with, have fun.

Richard

 

I live in SW Houston, the city of Meadows Place,
which is between Houston and Stafford. It's elevation is not listed on the site for elevation.
But you know Houston is very low.

My map sensor voltages at the sensor output match what the PFC dipslays. My test values.


PIM_________PSI______PSI______PSI Diff
Voltage__Autometer____PFC
------------------------------------
2.64_________0_______-.5_______-.5
3.33_________5_______4.6_______.4
3.91________10_______9.5_______.5
4.23________12______11.2_______.8
4.43________14.25____13.0______1.25

 

112 ft asl -18mmhg

 

Anyone ever try connecting the vacuum line for the boost gauge at different outlets? Maybe the nipples at where the extension manifold meets the intake manifold produces slightly more pressure than the nipple that the map sensor normally plugs into. Maybe we should try using the exact same vacuum sorce for both the boost gauge and the map sensor, then see if the readings vary.

 

ive run both out of the nipple on the UIM and both across the hose from the throttle body which is where the MAP usually reads from.

my readings did not differ

 

chuck, i keep hearing different things. what is the PIM voltage? is that coming from a pressure source/sensor? last i was being told is that it had something to do with the fuel system. are you trying to say we should play with the PIM voltage value or is the PIM voltage the voltage reading coming from the MAP sensor to the PFC.

thanks

 

On the sensor display screen you will see pimm voltage. It is the voltage coming out of the map sensor. What that shows is that the PFC is reading correctly but its display does not match what it is reading....
right Chuck?

 

Page 35 of the manual.
PIM voltage is the map/pressutre sensor output voltage.

 

+.26 kg/cm2
310ft ASL

I think my map sensor is f*ed. Got to test those voltages.

 

Okay today I get -23 mmhg at the same place that I got -35 mmhg just the other day. Earlyer today i was down at the beach, probably 10ft above sea level and I got -20 mmhg.

 

Check the weather channel, I'll bet you had a low pressure move though. All the change means is barometric pressure... That's why it's so hard to put a finger on altitude and vacuum reading.

Richard

 

I'm at 800 ft with the PFC showing -48mmhg today.

Tim Benton

 

Its funny how I am the only one with pressure insted of vacuum. I just checked my MAP voltages today, they were fine. Anyone have an idea?

 

So how does all the new numbers stack up? Do they disprove or prove your theory? Just curious?

Tim Benton

 

Just bumping it back up. Any final thoughts with the new data?

Tim Benton

 

well....for a while everything seemed to be falling into place with the theory behind it. a lot of responses went against it and i wasnt getting any real or "good" data. it was all sort of erratic. might be due to different setups and environmental conditions.....but some of those differences....they were pretty strange.

it seemed to be somewhat accurate for my car when i jotted down the #s though....if that means anything....

it still seems like to me that its a factor - the vacuum on the PFC has 3 digits....seems like youd be able to see the difference in atmospheric pressure to me.

i cant get good #s right now though b/c my engine has a crazy surging idle/dying idle vacuum leak that i havent found yet b/c i havent been home to mess with it in a while. *(pray its just a vacuum leak...)

im too busy with school right now to really research this any further.....if anyone else wants to head up on it though - go right ahead.