After installing new turbos I've notice that the PFC reads a lower Map Boost reading of .6. My defi mechanical still reads 12psi.

So I'm wondering what could cause this discrepancy. I know the boost gauge is tapped off the UIM. Where is the PFC reading boost from and why would it be different?

Most importantly is the car running very LEAN because it's adding fuel for 8.5 psi while I'm actually seeing 12?

Thx!

matt

 

Defi is a very accurate guage from my experience. And since it is run straight off a nipple from the UIM this could support its accuracy. Do you have an A/F gauge with wb02? Are your plugs coated in white residue/power-ish stuff?
The PFC I believe reads boost from the boost sensor. If the filter in between the line going from the sensor and the TB fails and gets the sensor dirty, it may give false readings. I'm not sure so I'll try to double check.

Jeremy

 

make sure the sensor line does not have a leak or a hole in it. off the map...

 

the pfc is getting its reading off the stock mazda map sensor, the gauge is taking its own readings.

between a mechanical defi gauge and the pfc and mazda boost sensor I would lean towards the pfc being the more accurate of the two. And yes ive seen a good share of defis reading inaccurate, not alot but enough that it DOES happen.

im confused though. your saying the difference is .6psi? or .6bar? cause in your latter statment your saying the car could be running 12 and showing 8.5.

just how far are the two off?

if its .6 psi difference i wouldent worry about it, just set and tune for the lower reading of the two.

if its 3.5 psi off then you should find a 3rd gauge and just run it outside the car through the window to quickly check which of yours is reading incorrectly.

 

Mines the same. PFC @ 1.0 Bar

GREDDY Electronic Recall Boost @ 1.2 Bar

 

PFC is low...do a search.

 

It is common for the PFC to read lower boost than most gauges. Search the Power FC Forum (section), there have been some discussions as well as tests performed. If you cannot find the test results pm me with your email address and I will send you the document.

I doubt that the reading will cause your car to go lean unless your maps are lean for a particular boost setting in the first place. The PFC will use its reading (not your boost gauge reading) to reference the relative map cells.

 

Given the way the car pulls I'd say it's pushing a strong 12psi in reality. I'm guessing the PFC gauge is off and the defi is accurate.

And yes by .6 i mean bar or (kg/mm^2 or whatever the PFC displays in). So i'm off by 3.5 psi which is a lot at least as far as A/F is concerned.

I'll check for holes in the map sensor line but I don't think that's the problem.

 

Yes, I know that "mr. search god",

but It used to read about .7 or so on the pFC and I'd get the same 12psi on the gauge, now It's .6 peak on the PFC and still 12psi on the gauge. So while I"m used to it being low, i'm not used to it being quite that low.

 

My power fc reads about .85. My autometer boost gauge reads 15psi. I'm trusting the PFC because if I was running 15psi on stock fuel.. my motor would have been toast a while ago.

 

The PFC reads the correct boost value from the MAP sensor just fine. There is a known bug that the Commander displays boost levels that are lower than actual, typically by 1-2 psi.

BTW, the common place to put a boost gauge is the unused UIM nipple -- this is not the best location IMO. My boost gauge is tapped off the MAP sensor, which is what the ecu uses to control fuel. Much better to see exactly what the ecu is seeing IMO....

You are living in a world of denial and it's going to cost you. I run 14 psi and have experienced spikes to 15 psi on very cold nights. My PFC has never read over 0.9 bar. You are making a foolish mistake to trust the PFC Commander, when it is a well-known error.

 

yeah, but he did say he was using an autometer gauge.

 

Well, I kind of doubt it. I dyno'ed at 285 rwhp at 12psi according to my pfc. My a/fs were in the high 10s. That was with the stock fuel system. Now I have a walbro and 1300s and my injector duty cycles are only hitting like 70% at .9 bar.

 

Woha 70%! My 1300's only hit 60% max. for my supposed 12 psi.

Anyhow I still find it funny that after the new turbos and front mount that my PFC reading is so low at .6bar. while I still feel like i'm hitting the same boost i used to and get the same reading on the mechanical gauge.

Could the correction factor in the PFC be off after resetting the power?

 

Well, then why the hell did you make your earlier comment? I assumed you had stock fuel system given your engine blowing comments.

You can choose to not believe me in regards to the Commander displaying incorrect boost levels, but it's a proven, verifiable fact, tested by several of the members here.

 

Well it looks like I had a little of each going on...

I'm sure my PFC reads low as they all seem to but I also tried out another boost gauge at it verified that my Defi read a bit high. I upped my duty cycle and got back up to .75 on the PFC which is where I should be.

thanks!
matt

 

Because I drove my car for 2 months like that and didnt detonate. I'm just pretty sure my autometer gauge is horribly inaccurate. And if my PFC is 3psi low.. that means I'm running 17 psi right now and my injectors are only hitting 70-75% and its very cold outside.