Will a 4 bar map sensor work correctly on a turbo 3800.

Correct MAP sensor is program into ECM/PCM.

Using anything else then ECM gets "wrong" MAP data and likely set DTCs and engine will have problems.
All MAP uses 0-5v but Bar # changes volt output.
Example only:
1 bar on 1 bar MAP sends ~5v
1 bar on 2 bar MAP sends ~2.5v
etc.

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to use a 4bar map sensor on a 3800 you would need to run it through the EGR 5 volt input, or the AC pressure 5 volt input and setup the PID and formula in the scanner you are using accordingly. I could help with the formula but I would need to know what system you are scanning with.

Thanks for the replys guys. Darkhorizon, I will do some checking to see how its wired. I am using hp tuners. Would this cause it to run to rich in pe. We can't get it to go to the correct commanded afr. It goes way richer.

quote Originally posted by yellow fever: Thanks for the replys guys. Darkhorizon, I will do some checking to see how its wired. I am using hp tuners. Would this cause it to run to rich in pe. We can't get it to go to the correct commanded afr. It goes way richer.

I would use an all in one system with its own gauge. Then puse analog output to hptuners. Same with wideband as I don't think the PCM will use it for anything.

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quote Originally posted by yellow fever: Will a 4 bar map sensor work correctly on a turbo 3800.

Will an OBD2 3800 SC PCM be able to correctly understand a 4-bar MAP sensor connected to the MAP sensor input and use it in fuel/spark calculations? NO. You would need to hack/modify the OS in the PCM's programming so it would understand and be able to work with a 4-bar MAP sensor. The amount of work required to do this probably wouldn't be worth it.

Connecting the 4-bar MAP sensor up to an EGR or A/C pressure sensor input is only going to give you the abilitiy of reading the 4-bar MAP sensor in the scan data. It is NOT going to be used by the PCM for anything else.

All 3800 Series 2 SC OBD2 PCMs calculate both fuel and spark based on input from the Mass Air Flow sensor exclusively. The MAP sensor input is used for very little (unless a tuning change or a MAF fault has forced the system into speed density mode).

If you are having a problem with the engine running much richer than what is shown as "calculated AFR" in the scan data, then you need to adjust your MAF calibration settings in the upper portion of the MAF calibration table (boost range) to bring the fueling back in-line and closer to what is being shown in "calculated AFR" on the scan data.

Of course, by altering the MAF calibration table settings, it should be understood that you also at the same time alter how cylinder load (used for spark timing) and calculated engine torque (used for regulating auto transmission line pressure) is going to be computed. IE: If you reduce the MAF flow setting to lean the fuel out and get it closer to "commanded AFR" on the scan data, you also end up lowering how much torque the PCM calculates the engine is making AND you lower the calculated cylinder load factor.

-ryan

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[This message has been edited by Darth Fiero (edited 08-28-2013).]

quote Originally posted by yellow fever: Thanks for the replys guys. Darkhorizon, I will do some checking to see how its wired. I am using hp tuners. Would this cause it to run to rich in pe. We can't get it to go to the correct commanded afr. It goes way richer.

What is "way" richer? The base PE tables are pretty darn straightforward.. PE vs RPM vs Time, base coolant temp PE are the 2 tables you will be changing around... Stock PE values will give you something like 11.8 commanded marching rich quickly... No other tables will be modifying commanded PE very much (there is a TPS PE table, but its moreso an enleanment table).

Thanks for the info guys. We got the pe afr set at 11.3. It goes down to low tens and won't lean out unless you back off the throttle. Go into boost slowly and its much better.we raised the pe afr command to 11.7 at the track to see what it would do. It went down to 10.9, 11.1. We have only been changing the pe afr command. I don't think we were using the other table you talked about DH. Maby that's the problem. Will it running rich while cruising affect what it commands at pe. I'm still working on the maf tables.

quote Originally posted by yellow fever: Will it running rich while cruising affect what it commands at pe. I'm still working on the maf tables.

If your MAF tune is off and the fuel trims are consistently running in the negatives during cruising operation AND they reset to 0% while in PE, then yes, that will cause it to run rich while in PE.

However, if the long term fuel trim is freezing negative when you go into PE, then that fuel trim is being applied while in PE mode. This doesn't mean you don't still have a MAF tuning issue however.

In any case, if you are seeing grossly negative fuel trim numbers while in normal closed loop operation, I would say you need to do some MAF calibration table work to get those numbers as close to 0% as you can. Doesn't need to be perfect (+/- 5% or so isn't bad at all). Remember, you need to combine both Short and Long Term Fuel Trims numbers to get the total amount of trim the PCM is adding or subtracting for fuel from the tune to satisfy stoich (14.7:1 AFR) while in normal closed loop mode.

What I do to tune MAF (in normal closed loop operation) is log these data PIDs:

MAF (hz or gm/sec)
STFT
LTFT

If say @ 2500 MAF hz you are seeing STFT of -4% and LTFT of -6% (-10% total); to correct this, reduce the MAF flow (gm/sec) @ the 2500hz slot in the MAF cal table by 10%. Make sure you smooth the values above and below where you make changes so there aren't any spikes in your MAF calibration table when you are done.

Once the system goes into PE mode the fuel trims should either freeze or reset which means you need to look at your Wideband O2 data to determine what changes need to be made at that particular MAF flow range. Compare actual Wideband O2 AFR with scan data commanded AFR and adjust MAF flow gm/sec in that operational area to correct the discrepancy.

Thanks for all the help guys.

I suggest to run in open loop (no narrowband feedback) while getting the tune setup to run correctly. Adding in closed loop functionality is really not that easy to do... I dont use it on any of my cars.