Question : 2 Bar or 3 Bar MAP Sensor

[G.I.Ceo]

I have a 02 GA 3400 with a 3500 top swap that I have been working on for boost. I will be running a Garrett GT35 on my setup. What I have little understanding of is what MAP sensor to run. I have heard changing over to a 2 Bar setup is easier to tune with boost but I wasnt sure of wich one I need to use. I will be using DHP to tune.

[pocket-rocket]

It depends on how much boost you want to run. A 2 bar only reads to 14.7 psi of boost. Anything more and you need to move to a 3 bar. If you run close to 14, you may want to consider a 3 bar depending on your altitude.

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[G.I.Ceo]

I believe my stock MAP sensor is a 3 bar MAP sensor. So I should be able to use my stock sensor and be perfectly cool then?

[ForcedFirebird]

Your stock sensor is 1bar, it only reads from -14.7 vacuum to 0psi.

[G.I.Ceo]

That makes sense since this car is not boosted stock. So should I use a 2 or 3 bar? Is either one easier or harder to tune for or is the setup the same? I had everything else figured out but I didn't quite do my homework yet on the different MAP sensors.

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[pocket-rocket]

How much boat ate you going to run?

The difference in tuning that I see is sensor resolution. Think of it this way...look at it like a volume knob on a stereo that is numbered 1-10 for a 1 bar. 1 is -14.7 psi and 10 would be 0 (wot).

Then you have another that goes from 1-20 nut has the same sweep, or range of motion. 1 is -14.7psi, 10 is still 0 (wot) and 20 is 14.7psi of boost, but the difference is the distance between 1-10 on the 2 bar is half the distance as the 1 bar because it reads twice the range as the 1 bar, hence it has less resolution.

I hope this helps understand it some. All 3 sensors still have the same output range, but is how they react to vacuum/boost is what makes the difference.

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[G.I.Ceo]

How much boat ate you going to run?

The difference in tuning that I see is sensor resolution. Think of it this way...look at it like a volume knob on a stereo that is numbered 1-10 for a 1 bar. 1 is -14.7 psi and 10 would be 0 (wot).

Then you have another that goes from 1-20 nut has the same sweep, or range of motion. 1 is -14.7psi, 10 is still 0 (wot) and 20 is 14.7psi of boost, but the difference is the distance between 1-10 on the 2 bar is half the distance as the 1 bar because it reads twice the range as the 1 bar, hence it has less resolution.

I hope this helps understand it some. All 3 sensors still have the same output range, but is how they react to vacuum/boost is what makes the difference.

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Yeah it does help a little bit. I still don't know which one would be the best for my build. I need to do more research on the sensors and see how they are effected by boost. Do I need to replace the stock MAP sensor to be able to get the tune in correctly while under boost? Then I seen that they also make a 2.5 Bar MAP sensor which I guess gives you the best of both the 2 Bar and 3 Bar MAP sensors.

[pocket-rocket]

Yes, it will replace the stock map sensor.

I also hate auto correct at times... Boat instead of boost...

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[G.I.Ceo]

What I have found after doing a ton of research is to just change over the MAF sensor to a LS1 MAF. I guess all the tuning I will need will be handled with the upgraded MAF sensor. The nice thing about that is it will be easier because all I will have to do is important the table and thats it and will be a tone easier then trying to tune for a 2 bar or 3 bar MAP. Do you guys agree wit this?

[unchained01]

Its the first step But alot easier then starting from scratch
You will possibly have to smooth out some of the scale to have a more consistent curve
There are posts on powrtuner site on how to do this alng with the guys we both know who have boosted setups Greg (AleroB8 Aaron and Paul (MMGT1) and Paul (lightningGA )
Sorry about those i have forgotten to mention
Also there are more posts on HP tuner site you can read too ,look in the GMV6 tuning section at posts from Russ K he has a simplfied method for smoothing out the scale on the 3400 in grand ams with boost

[TGP37]

The resolution is lower but along the areas in the VE map that are not chaotic, interpolation will keep the readings about the same. It is curves and other non-linear changes which loose resolution the most.

I used a 2-bar MAP on a stock NA PCM, tuned the values and it worked perfectly. I used data from a boosted app (Sunfire I think?)...

MAP Sensor Offset: 7.988281
MAP Scaling Factor: 200
Default MAP Scalar: 0.1799316
Default MAP Sensor Offset: 10
Default Max MAP: 160

My stock 3100v6 MAF hits just under 10000 Hz at 12 psi near redline. If you aren't going past 1 Bar of boost the stock MAF will work.


Tuning the 2 bar map: All non-boost regions are still in factory tune in the VE Table. Just got to log boost with the MAF and calculate how much the VE will be in the boosted regions.

I prefer to have the VE tables tuned in case the MAF fails while in boost to prevent going crazy lean and destroying the engine.


IMHO, anything past 1 BAR of boost on these motors requires lots of $$$. The 2 bar map will be perfect for your build. The stocl MAF will be able to keep up as well, just got to tune the very end of the MAF Table where factory left it flat (assuming the engine will never see that amount of airflow stock)

[rickykline]

MAP Sensor Offset: 7.988281
MAP Scaling Factor: 200
Default MAP Scalar: 0.1799316
Default MAP Sensor Offset: 10
Default Max MAP: 160

without looking at my tune I believe i use the same values for my 2bar map. I am currently running about 170kPa at redline the car runs decent.. although i have this bit of info that made me think twice about the map sensor...

quoted from an email convo with me and Mike Milzy
Mike-"i believe the v6 pcm's use speed density for open loop, which would be rpm and map sensor readings, then it goes into closed loop and uses MAF flow and O2 sensor values to set the amount of pulse width. Like you said, the map readings aren't used for fueling, atleast in closed loop, so why use a 2-bar map? when we do our turbo kits on 3400 cars, the VE table stays as it is, we use a 1 bar map, stock MAF sensor, set the IFR's, and then tune off of base AF vs ECT and MAF freq, and it works out great. We've made 400whp on stock MAP and stock MAF. We did have to add a mini-AFC to get enough resolution out of the MAF to make 400whp. I think we ran out of that around 340 or something."

[rickykline]

I guess milzy isnt worried about MAF faliure and if it did fail hoping the customer wasnt over 100Kpa when it did fail.

[TGP37]

Well, I run open loop and I currently have a 1 bar map sensor installed atm. I boosted up many times in open loop, I can say for certain the MAF sensor is in play in both OL and CL. (at least I can be sure of 96-97 pcms)

Now, the stock PCM file has a setting for Transient Airmass Calculation Mode. It is set at 0 on every stock PCM file I could find. The other options were 1-Use MAF failure mode for transient fueling and 2- Use the VE table for transient fueling. Another good reason to have a 2, 2.5 or 3 bar map.

Because of that, I am curious exactly how transient is calculated as it seems the VE table is not used for transient fueling referrences against the MAF sensor.

After all the time and energy put into a turbo build, backing up a MAF failure with a boost capable MAP sensor is prudent imho. Anything could happen, like the wire melting open and shorting out. If the MAP isn't tuned for boost, and the car is in boost or the driver goes into boost.......boom! Good bye money in the wallet for that repair.

[rickykline]

How are you running open loop? like disable close loop by failing the MAF or are you refering to cold starts? I wanted to build a SD tune and set the max maf failure rate to 0 and see if it would stay in OL and not go crazy on me, but I wanted to wait till i got hptuners for ease of tuning over my powrtuner I'm sure people have tried this i just haven't researched anything on my car in a long time.