tuning VE, question about disconnecting maf
12-13-2004, 02:46 PM
#1
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tuning VE, question about disconnecting maf ok so i am trying to follow the writeup on the hptuners site for tuning LTFT by unplugging the maf...
http://www.hptuners.com/forum/YaBB.p...num=1101426165
i followed the steps listed: disabled the SES light for codes p0101 p0102 p0103, copied the high octane table to the low octane, flashed the pcm with the new tune, unplugged the maf and started the car up to go do some logging. one problem though, with this setup my service vehicle light comes on (NOT the SES light), but if i plug the maf back in and upload the older tune the light goes away. will this affect my logs for tuning the VE table? i did a search but i haven't found any posts about a service vehicle light coming on after disconnecting the maf. thanks for any input.
http://www.hptuners.com/forum/YaBB.p...num=1101426165
i followed the steps listed: disabled the SES light for codes p0101 p0102 p0103, copied the high octane table to the low octane, flashed the pcm with the new tune, unplugged the maf and started the car up to go do some logging. one problem though, with this setup my service vehicle light comes on (NOT the SES light), but if i plug the maf back in and upload the older tune the light goes away. will this affect my logs for tuning the VE table? i did a search but i haven't found any posts about a service vehicle light coming on after disconnecting the maf. thanks for any input.
12-13-2004, 03:02 PM
#2
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Don't disable the codes... those codes (at least 1 of them) needs to be set to cause the PCM to failover into Speed Density Mode...
doesn't matter if the SES light comes on (those instructions appear to be setting it so that the code is still set... but it doesn't set a light) ... I prefer seeing the light as it gives me a visual cue that I'm running in SD
Sounds like you're actually turning the codes off/disabling them from being set .. so the PCM won't failover ... so it's trying to run off a non existent MAF signal ... since it's not failing over it doesn't know what to do so it sets the service vehicle light
doesn't matter if the SES light comes on (those instructions appear to be setting it so that the code is still set... but it doesn't set a light) ... I prefer seeing the light as it gives me a visual cue that I'm running in SD
Sounds like you're actually turning the codes off/disabling them from being set .. so the PCM won't failover ... so it's trying to run off a non existent MAF signal ... since it's not failing over it doesn't know what to do so it sets the service vehicle light
12-13-2004, 03:22 PM
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well, i thought i just disabled the SES light, but i guess not lol. anyways, i re-enabled them and im just going to do it with the SES light on, no biggie. thanks for the help 
12-13-2004, 03:23 PM
#4
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also... you can set the MAF Fail Frequency value to 0 (I think it's under engine diagnostics) and this will cause a P0103 ... puts you into Speed Density w/out having to pop the hood and disconnect the MAF
yup
12-13-2004, 06:00 PM
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Originally Posted by horist
also... you can set the MAF Fail Frequency value to 0 (I think it's under engine diagnostics) and this will cause a P0103 ... puts you into Speed Density w/out having to pop the hood and disconnect the MAF
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12-13-2004, 10:01 PM
#10
I just tried this tonight and it seems to work fine. Connect the MAF back up and change the table mentioned above to 0. You will need to either put the car in open loop or closed loop depending on how you plan on tuning the car. (I prefer open loop). Nice thing about this is you still receive the readings from the MAF like it is connected.
12-14-2004, 10:02 AM
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Good stuff...I haven't been able to try this yet myself seeing as how the car is down. But, if enough of you say that it is working, then I will change the write up to reflect that, as it is an easier change.
Matt
Matt
12-14-2004, 06:56 PM
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Originally Posted by horist
also... you can set the MAF Fail Frequency value to 0 (I think it's under engine diagnostics) and this will cause a P0103 ... puts you into Speed Density w/out having to pop the hood and disconnect the MAF
-With EFI I could log accurate VE's even though MAF doesn't log.
-I adjusted VE values.
-Trims will log.
-It seems we can observe trims without the MAF, determine how close
the calculated IFR's are to correct and set the IFR's. Program the MAF back
and see the affect on trims by the MAF.
-Does this make sense?
PS. SAE MAF can be logged, not GM.
Last edited by gojo; 12-14-2004 at 07:31 PM.
12-14-2004, 07:13 PM
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Yep. I had a feeling there was a way to convince the PCM to allow you to read dynamic airflow and MAF frequency at the same time. I'm glad somebody out there was smart enough to figure it out!
12-14-2004, 08:28 PM
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Originally Posted by gojo
Nice going. Looks like a really good find. I tried only 0'ing the MAF, today and found the following.
-With EFI I could log accurate VE's even though MAF doesn't log.
-I adjusted VE values.
-Trims will log.
-It seems we can observe trims without the MAF, determine how close
the calculated IFR's are to correct and set the IFR's. Program the MAF back
and see the affect on trims by the MAF.
-Does this make sense?
PS. SAE MAF can be logged, not GM.
-With EFI I could log accurate VE's even though MAF doesn't log.
-I adjusted VE values.
-Trims will log.
-It seems we can observe trims without the MAF, determine how close
the calculated IFR's are to correct and set the IFR's. Program the MAF back
and see the affect on trims by the MAF.
-Does this make sense?
PS. SAE MAF can be logged, not GM.
YOu can also use this method to derive a good workable MAF table. I posted about it a few days ago but no one was interested. All you need to do is log dynamic air and plot that against maf frequency and you will see how far off the maf really is
The trims still update wit the maf diosconnected so you will still be able to have all the fruits of live forcing the pcm into SD mode
12-14-2004, 08:34 PM
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Also dynamic air is back calculated from the ve values, iat and map values....
Bes tthing would be to dial in the ve table in forced SD mode and then use the dynair/g per sec to figure out a new accurate maf table
Bes tthing would be to dial in the ve table in forced SD mode and then use the dynair/g per sec to figure out a new accurate maf table
12-14-2004, 08:53 PM
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Originally Posted by HumpinSS
Also dynamic air is back calculated from the ve values, iat and map values....
Bes tthing would be to dial in the ve table in forced SD mode and then use the dynair/g per sec to figure out a new accurate maf table
Bes tthing would be to dial in the ve table in forced SD mode and then use the dynair/g per sec to figure out a new accurate maf table
12-14-2004, 10:26 PM
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Originally Posted by HumpinSS
YOu can also use this method to derive a good workable MAF table. I posted about it a few days ago but no one was interested. All you need to do is log dynamic air and plot that against maf frequency and you will see how far off the maf really is
The trims still update wit the maf diosconnected so you will still be able to have all the fruits of live forcing the pcm into SD mode
The trims still update wit the maf diosconnected so you will still be able to have all the fruits of live forcing the pcm into SD mode
I think when you say disconnected it's confusing. May be the reason for no response. With no MAF you can't get VE's or MAF frequency. With the MAF zeroed you get it all.
What caught my interest was realizing IFR's could be checked for correctness. I'm not sure of the formulas and their accuracy for calculating IFR's for bigger injectors. This new idea seems very important to me. If VE's are corrected then IFR's can be set with the MAF 0'd. When the MAF is hooked up again the trims should then reflect the inaccuracy of the MAF. My hangup is IFR's since if they are right setting AFR gets easier.
