Power FC what does your PFC read for boost when engine is off?
what does your PFC read for boost when engine is off?
Mine changes sometimes but was -42 a few days ago and -50 tonight. It is not at 0.
This was with the ignition set to the on position but the car not running. Also, it was the same numbers on both my cars.
Is this number I am seeing when the engine is off the 'absolute' pressure it is reading that is the offset it uses for the 'relative' pressure it displays when the engine is running?
This was with the ignition set to the on position but the car not running. Also, it was the same numbers on both my cars.
Is this number I am seeing when the engine is off the 'absolute' pressure it is reading that is the offset it uses for the 'relative' pressure it displays when the engine is running?
Last edited by damian; Dec 14, 2003 at 02:15 AM.
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The difference you see is part of the reason that the pfc never matches your boost gauge. The negative number will change slightly because of [I think] the subtle changes in barometric pressure in your area.
You can zero-out the boost reading by adjusting the offset property in the datalogit (Settings 3 page). I took mine from 3947 (stock) to 3340.
You can zero-out the boost reading by adjusting the offset property in the datalogit (Settings 3 page). I took mine from 3947 (stock) to 3340.
skotx,
>>negative number will change slightly because of [I think] the subtle changes in barometric pressure in your area.
yes, that is what i was thinking too
>>The difference you see is part of the reason that the pfc never matches your boost gauge.
the only problem i have with that is even with my pfc reading -50 yesturday (keep in mind this was exactly the same on both my pfcs) is that when the car is running it matches exactly to my boost gauge? So from what I see in my tests, that is not the case.
>>negative number will change slightly because of [I think] the subtle changes in barometric pressure in your area.
yes, that is what i was thinking too
>>The difference you see is part of the reason that the pfc never matches your boost gauge.
the only problem i have with that is even with my pfc reading -50 yesturday (keep in mind this was exactly the same on both my pfcs) is that when the car is running it matches exactly to my boost gauge? So from what I see in my tests, that is not the case.
This is always a newbie question. A search would have returned many such inquiries.
It is an internal PFC conversion error, nothing to do with
your loaction or barometric pressure.
Here is another thing for you to worry about: as boost goes up, the PFC boost reading reads lower and lower than what it actually is.
If you don't like it, buy a datalogit and fix it.
It is an internal PFC conversion error, nothing to do with
your loaction or barometric pressure.
Here is another thing for you to worry about: as boost goes up, the PFC boost reading reads lower and lower than what it actually is.
If you don't like it, buy a datalogit and fix it.
hi chuck, thanks for the input...im such a newbie :-)
actually, my though proccess was off that is why i missed the boat on doing a search on the pfc, it is because i though the avcr was off, not the pfc (that is why i started this post, to try to correct my avcr) ...so what you are saying is that the avcr is actually correct and my pfc is not... (i was doing searches on the avcr not the pfc..doh!!!)
>>It is an internal PFC conversion error, nothing to do with your loaction or barometric pressure.
I was aware of the pfc not reading boost right but i thought it was in the higher boost values not in vac.
>>Here is another thing for you to worry about: as boost goes up, the PFC boost reading reads lower and lower than what it actually is.
great :-(
>>If you don't like it, buy a datalogit and fix it.
and i do have a datalogit...so ill do a search on how to correct the reading...or post one if you know of one offhand.
actually, my though proccess was off that is why i missed the boat on doing a search on the pfc, it is because i though the avcr was off, not the pfc (that is why i started this post, to try to correct my avcr) ...so what you are saying is that the avcr is actually correct and my pfc is not... (i was doing searches on the avcr not the pfc..doh!!!)
>>It is an internal PFC conversion error, nothing to do with your loaction or barometric pressure.
I was aware of the pfc not reading boost right but i thought it was in the higher boost values not in vac.
>>Here is another thing for you to worry about: as boost goes up, the PFC boost reading reads lower and lower than what it actually is.
great :-(
>>If you don't like it, buy a datalogit and fix it.
and i do have a datalogit...so ill do a search on how to correct the reading...or post one if you know of one offhand.
Damian,
Go to settings 3, lower the offset, then write it to the ecu. You should see the commander get closer to 0.
I did this and my car started backfiring while shifting or in some cases, during engine braking if it was hot enough. I didn't change the decel numbers so no extra fuel was being thrown in there. I changed it back to show what it was before...about -43, but then again, my crappy autometer reads under 0 (but in the red square) when the car's off.
Chuck, what Blitz boost gauge are you using?
Tim
Go to settings 3, lower the offset, then write it to the ecu. You should see the commander get closer to 0.
I did this and my car started backfiring while shifting or in some cases, during engine braking if it was hot enough. I didn't change the decel numbers so no extra fuel was being thrown in there. I changed it back to show what it was before...about -43, but then again, my crappy autometer reads under 0 (but in the red square) when the car's off.
Chuck, what Blitz boost gauge are you using?
Tim
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Good Lord, why do I even bother to post? I told you how to zero out the boost reading in the first response to your question.
Are you saying that the pfc always matches your boost gauge, even though with key on it shows -50 vacuum? Even peak boost?
I disagree that it's an internal conversion error, but it's really not important enough of a topic to spend time debating.
Are you saying that the pfc always matches your boost gauge, even though with key on it shows -50 vacuum? Even peak boost?
I disagree that it's an internal conversion error, but it's really not important enough of a topic to spend time debating.
>>Good Lord, why do I even bother to post? I told you how to zero out the boost reading in the first response to your question.
i appreciate the info you posted skotx, i did read it and understood how to chagne the number, but i wanted to know if there was somthing i should do first, like determine some absolute number to adjust it by using some other gauge.
>>Are you saying that the pfc always matches your boost gauge, even though with key on it shows -50 vacuum? Even peak boost?
no, it was off, but i though it was the autometer, but now after reading some posts my autometer was probably correct and the pfc is wrong...
>>I disagree that it's an internal conversion error, but it's really not important enough of a topic to spend time debating.
Im a precision freak, so i think it is... i want the reading to be THE reading, not a.... well, uhh, kinda around here somewhere reading
keep in mind the main reason for me startign this thread was to fix my avcr boost reading that was off from my pfc, and now i see that is it probably the pfc that is off and i should calibrate the pfc to the defi boost gauge and avcr.
i appreciate the info you posted skotx, i did read it and understood how to chagne the number, but i wanted to know if there was somthing i should do first, like determine some absolute number to adjust it by using some other gauge.
>>Are you saying that the pfc always matches your boost gauge, even though with key on it shows -50 vacuum? Even peak boost?
no, it was off, but i though it was the autometer, but now after reading some posts my autometer was probably correct and the pfc is wrong...
>>I disagree that it's an internal conversion error, but it's really not important enough of a topic to spend time debating.
Im a precision freak, so i think it is... i want the reading to be THE reading, not a.... well, uhh, kinda around here somewhere reading
keep in mind the main reason for me startign this thread was to fix my avcr boost reading that was off from my pfc, and now i see that is it probably the pfc that is off and i should calibrate the pfc to the defi boost gauge and avcr.
Originally posted by Tim Benton
Damian,
Go to settings 3, lower the offset, then write it to the ecu. You should see the commander get closer to 0.
I did this and my car started backfiring while shifting or in some cases, during engine braking if it was hot enough. I didn't change the decel numbers so no extra fuel was being thrown in there. I changed it back to show what it was before...about -43, but then again, my crappy autometer reads under 0 (but in the red square) when the car's off.
Chuck, what Blitz boost gauge are you using?
Tim
Damian,
Go to settings 3, lower the offset, then write it to the ecu. You should see the commander get closer to 0.
I did this and my car started backfiring while shifting or in some cases, during engine braking if it was hot enough. I didn't change the decel numbers so no extra fuel was being thrown in there. I changed it back to show what it was before...about -43, but then again, my crappy autometer reads under 0 (but in the red square) when the car's off.
Chuck, what Blitz boost gauge are you using?
Tim
chuck, did you notice tims bad symptoms after zeroing urs out? or did you just leave it off.
I just left mine as it was. Then I mapped the real boost to PIM and PIM V, and adjusted my P rows so that the PFC would use the following.
P17 for 12PSI boost, 18000 PIM ABS
P18 for 14PSI boost, 19585 PIM ABS
P19 for 16PSI boost, 20900 PIM ABS
P20 for 18PSI boost, 21855 PIM ABS
See attachment of boost comparisons.
Was done with a hand air pump, Blitz DSBC boost controller, PFC, and DATALOGIC.
P17 for 12PSI boost, 18000 PIM ABS
P18 for 14PSI boost, 19585 PIM ABS
P19 for 16PSI boost, 20900 PIM ABS
P20 for 18PSI boost, 21855 PIM ABS
See attachment of boost comparisons.
Was done with a hand air pump, Blitz DSBC boost controller, PFC, and DATALOGIC.
Last edited by cewrx7r1; Dec 17, 2003 at 06:57 PM.
Tim,
The reason I did not ZERO out my PIM was that I was afraid that it might shift all my lower row usage up by one then I would have to move them all upby one to keep my AFRS the same as before. I did not feel like retuning that many rows again. Especially since I got the car to pass emmissions with my current fuel maps.
The reason I did not ZERO out my PIM was that I was afraid that it might shift all my lower row usage up by one then I would have to move them all upby one to keep my AFRS the same as before. I did not feel like retuning that many rows again. Especially since I got the car to pass emmissions with my current fuel maps.
Last edited by cewrx7r1; Dec 17, 2003 at 07:11 PM.
Here is a vac/pressure comparison with the defi gauge, avcr, and pfc all hooked together and feed by a mighty vac on the other end.
Vac measured in mm/hg and pressure measured in kg/cm2
I know I'm a newbie on this and this is old news to most, but wow, I cant get over how bad the pfc is off? Is the stock computer just as off? It is rediculous to think that you can be running almost 15 lbs boost when the pfc is telling you only 12lbs...no wonder engines are popping :-( ...and it also means everyones reported vac reading is off so really when you think ur vac is -18~-17...its more like -16~-15....that sucks too. I hate inaccurate sh_t :-( I need to read all the posts on this, I must have some relationship wrong.
Vac measured in mm/hg and pressure measured in kg/cm2
Code:
MVac Defi AVCR PowerFC 0 0 0 -42 -127 -127 -116 -164 -254 -254 -251 -294 -381 -381 -380 -417 -457 -457 -460 -491 -508 -508 -504 -534 0.35 0.35 0.32 0.23 0.56 0.56 0.56 0.45 0.7 0.7 0.67 0.56 0.84 0.84 0.84 0.74 1 1 1 0.88
Code:
Helper Conversion Tables KG/CM2 PSI or LBS 0.35 5 0.42 6 0.49 7 0.56 8 0.63 9 0.703 10 0.773 11 0.84 12 0.913 13 0.984 14 1.05 15 mm/hg in/hg -355.6 -14 -381 -15 -406.4 -16 -431.8 -17 -457.2 -18 -482.6 -19 -508 -20
Last edited by damian; Dec 20, 2003 at 05:15 AM.
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No, you don't have a relationship wrong. That's just the way it is with the stock offset. Now, use the Datalogit to zero out the reading and run your tests again.
Don't be afraid of changing the offset. I did some searching on the Datalogit users group, and those guys were tweaking both the offset and the scale on the Settings 3 screen to get the Apexi and GM 3 BAR map sensors to display zero at key-on. That's what those parameters are for, and are needed since the pfc doesn't have an internal barometric pressure sensor (the stock computer has one, and I'm assuming you're AVCR has one as well).
A little info for you that I've gained from my own research this week:
At the very least, you gave us some confidence in the Defi and AVCR!
Scott
Don't be afraid of changing the offset. I did some searching on the Datalogit users group, and those guys were tweaking both the offset and the scale on the Settings 3 screen to get the Apexi and GM 3 BAR map sensors to display zero at key-on. That's what those parameters are for, and are needed since the pfc doesn't have an internal barometric pressure sensor (the stock computer has one, and I'm assuming you're AVCR has one as well).
A little info for you that I've gained from my own research this week:
- All the PIM values that you see in the manual and in the Datalogit represent kilograms / meters squared (kg/m2). Divide by 10000 to get kg/cm2. This PIM value is important because it's what the raw voltage from the MAP sensor is first converted to, with the offset subtracted later.
- To get the boost displayed on the commander from the PIM value given by the Datlogit (logging Advanced), you must subtract atmospheric pressure then convert to kg/cm2. I'm reasonably certain that Apexi (or the Datalogit at least) uses 10332 kg/m2 for atm press.
- The PIM shown by Advanced logging in the Datalogit has already had the offset subtracted. Note, I said offset, not atm press. Two different things.
- If you're interested, I can PM you the formula posted by Glen that's used to calculate PIM. It employs all the variables: input voltage, scale, and offset.
At the very least, you gave us some confidence in the Defi and AVCR!
Scott
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What I just posted might be a little confusing. Maybe a breakdown will help:
1) A voltage is read from the MAP sensor: 3.516
2) The voltage is converted to PIM: 3.516 = 15121 kg/m2
3) Offset is subtracted: 15121 - 3380 = 11741 (this is displayed as PIM in Datalogit)
4) Subtract atmospheric pressure: 11741 - 10332 = 1409
4) Convert to kg/cm2 (or mmHg if vacuum): 1409 / 10000 = 0.14 kg/cm2
As to why the Datalogit logs don't show a decimal number for boost: I think they divide kg/m2 by 100, then convert the result to an integer. This is pure speculation on my part.
Edit:
I just realized that I did the above test with an offset of 3380, which is the value I came up with to zero out my display. When I run the above with the stock offset of 3947, I end up with a pressure value of 0.08 kg/cm2, or 0.06 kg/cm2 lower. 0.06 kg/cm2 = ~ 44 mmHg, which is close to the -35 mmHg I was seeing prior to the offset change. Not exact, but close.
Scott
1) A voltage is read from the MAP sensor: 3.516
2) The voltage is converted to PIM: 3.516 = 15121 kg/m2
3) Offset is subtracted: 15121 - 3380 = 11741 (this is displayed as PIM in Datalogit)
4) Subtract atmospheric pressure: 11741 - 10332 = 1409
4) Convert to kg/cm2 (or mmHg if vacuum): 1409 / 10000 = 0.14 kg/cm2
As to why the Datalogit logs don't show a decimal number for boost: I think they divide kg/m2 by 100, then convert the result to an integer. This is pure speculation on my part.
Edit:
I just realized that I did the above test with an offset of 3380, which is the value I came up with to zero out my display. When I run the above with the stock offset of 3947, I end up with a pressure value of 0.08 kg/cm2, or 0.06 kg/cm2 lower. 0.06 kg/cm2 = ~ 44 mmHg, which is close to the -35 mmHg I was seeing prior to the offset change. Not exact, but close.
Scott
Last edited by skotx; Dec 20, 2003 at 10:31 AM.
great posts Scott!!
that really helped me understand the situation.... and like you said, the main concern is if I zero out the pfc do I have to re-tune the maps since it may rad from a different row now (and i would think it would)...
so I probably will leave the pfc where it is, and use the avcr/defi gauge to see my actual boost avalues and the avcr to manage boost.
if I get another good tuner in town again (a few of us flew steve kan a while back) then I can zero it out and have them modify the maps if needed.
>>At the very least, you gave us some confidence in the Defi and AVCR!
>>Nice to know my Defi gauge is accurate....
yeah, glad to help (hahaha) ;-)
that really helped me understand the situation.... and like you said, the main concern is if I zero out the pfc do I have to re-tune the maps since it may rad from a different row now (and i would think it would)...
so I probably will leave the pfc where it is, and use the avcr/defi gauge to see my actual boost avalues and the avcr to manage boost.
if I get another good tuner in town again (a few of us flew steve kan a while back) then I can zero it out and have them modify the maps if needed.
>>At the very least, you gave us some confidence in the Defi and AVCR!
>>Nice to know my Defi gauge is accurate....
yeah, glad to help (hahaha) ;-)
I guess I'll restate...has it changed from what Chuck's proven in the past and I missed it? The commander displays the wrong boost, but the ECU itself is in the right row for the boost (or combination of rows 16/17..17/18)
I might have missed something in the datalogit e-mail group or here that has changed this.
Tim
I might have missed something in the datalogit e-mail group or here that has changed this.
Tim
so Tim, ur saying that, for example, the commander shows .7 even though it is more like .8+ but goes to the row for .8 ?
my though was that it goes to the row for .7 still, but that row actaully has fuel for .8 because tuning by afr would make it so, even though the pfc is telling you .7
my though was that it goes to the row for .7 still, but that row actaully has fuel for .8 because tuning by afr would make it so, even though the pfc is telling you .7
In Chuck's document, the PFC and voltage the map sensor give are within 1/100th of each other, so it's reading the map sensor voltage correctly, just showing it correctly on the commander.
Tim
Tim
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Wow, i'm more confused then I was before I read this. Am I right to assume that Steve Kan doesn't do these corrections? Also, it sounds like they can only be done with datalogic?
Can a simple fix be connecting the boost controller to the extension manifold for vacuum rather then the turbo compressor snail? I have the Apexi (Denso) 3-bar map sensor and the kit is supposed to compensate barometric pressure with the additional 2-bar sensor.
Can a simple fix be connecting the boost controller to the extension manifold for vacuum rather then the turbo compressor snail? I have the Apexi (Denso) 3-bar map sensor and the kit is supposed to compensate barometric pressure with the additional 2-bar sensor.
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