suprfast

what to trust??? i know this has been discussed a million times but the old threads dont have my info. im running a DEFI water temp and boost gauge. im also running the PFC. the boost varies greatly, and the water goes wacko every once in awhile. the boost reads 12-13 lbs on the DEFI when i get anywhere from .68-.70 BAR on the PFC. what to trust??? kinda thinking about just ditching the whole defi setup, but i like the convience of the quick glances. they would only be convienent if they are accurate though. is there a way to make sure they are properly calibrated?
kris

poss

iTrader: (5)

for the boost, you might try hooking up a test guage, in addition to your current guage and see if they match. Take it easy until you are sure though. If the PFC is only supplying enough fuel for .7 kg/cm^2 rather than the actual 12 psi, you could risk popping your motor.

BoostedRex

Does anyone else have experience with the Defi gauges being inaccurate?? I am planning on running the Defi Link system for a full 5 gauge setup. I would like to find out any bad rumors or truths about them before I sink $1,000 into my gauges to find out that they suck azz. Thanx.

Zach

rynberg

do a search for boost readings in the PFC forum. You will discover that the Commander frequently displays boost 2 psi below the actual number it is reading. There is nothing to worry about, it is still reading the fuel map at the correct boost. Trust your Defi gauges unless there is some error in the installation of the sensors.

rx7speed811

i think the last time this was discussed, the consensus was that the readings are proportionally different just because the pfc reads from a lower pressure area of the compression tract than the defi gauges do (i am assuming the lower intake manifold vs. the upper intake manifold). if i remember correctly, both can be trusted, but tuning should be done according to the mechanical defi gauge, since it is a more conservative way to measure boost.

somebody please correct me if i am my information is misleading, it is all from memory.

maxcooper

It doesn't really matter what the precise value of the PFC reading, as long as the reading changes in proportion to the thing you are measuring, and the tuning is correct for the way it reads. For boost, for instance, it doesn't matter if the PFC reads 2 psi lower than the gauge, as long as the fuel map is setup properly for the reading it does get. I have never really compared my readings between PFC and boost gauge, but I would expect some difference since they read the pressure from two different points on the manifold.

The water temp reading sounds like it might need some attention, however, since it is jumping around. You might need a new water temp sender.

-Max

apneablue

I have the defi link sys boost and it is always higher than the commander. about 2psi to be exact...I have read that if I should trust one I should trust the gauge...

Interesting what Max says though...

cewrx7r1

iTrader: (2)

MAXCOOPER is correct. As long as you adjust fuel and timimg to the PFC boost, all will still work well.

I know it is frustating that for the price we had to pay for the PFC, that is has this bad inherent internal programming error! Pisses me off too!

DaleClark

iTrader: (55)

The case might possibly point to flakiness in the stock sensors. Old sensors, flaky connections, flaky grounds, etc can all lead to the value the ECU sees being less or different than the actual condition.

Regardless, Defi meters are really top drawer in quality. I would trust those far more than what the PFC Commander is saying.

Dale

cewrx7r1

iTrader: (2)

Your assumptions are wrong in my opinion.

I have measured the map sensor output voltages at it's connector and they they match what the PFC displays
on the sensor screen. But when you look aat the displayed boost, it is in error. Internal analog to digital conversion error!!!!!!!!!!!!!!!!!!!!!!!!!

The map sensor voltage to boost matches the Mazda manual perfectly.

SPOautos

REALLY!!!! I didnt realize this, I wonder how they could miss something so easy??? I just figured it was the map sensor or pressure source.

Do basically your saying when you checked the voltage on the map sensor and used the conversion in the workshop manual it read similar to what your boost gague was showing....BUT that the PFC uses the wrong conversion which makes the boost read wrong.

How the hell could they miss that??? I mean surely they tested it on car with boost gagues and noticed it was wrong. Do basically if I want to run 17psi of boost and the stock map sensor cuts off at 17psi of boost, I really need to cut it off at around 15psi according to the pfc.....OR does it go to 17psi in PFC land which is really like 19psi on the map sensor????

I mean the PFC grids goes to 17psi and that is based on what is in the display (from what I can tell) so does this mean we can actually run 19psi????

I'm fuxing to be tuning my car so I'm glad this came up.

STEPHEN

cewrx7r1

iTrader: (2)

Do the test yourself. All you need is a digital volt meter, small hand air pump with a one way valve, some vacumm hoses, and a safety pin to use on the map sensor connector/wire. Turn on the ignition but do not start the car. Have a friend record boost by boost gauge, by PFC, and taaake vootages once at the connector and once by PFC. To be really cool, do it by 2psi steps from 0 to 16psi.

TwinTriangles

Might be time for a beer, chuck...

jr

If it was an internal conversion error on the PFC then wouldn't it always be off by the same amount? On mine sometimes it's real close and other times it's way off. I'm wondering if the PFC is not taking current atmospheric conditions into effect or something along those lines.