this might help others too....

[VanishingImage]

Trying to understand MAP sensors and boost..........

Ok,basically a 1 bar MAP won't work with boost because it only reconizes current atmospheric pressure. For the computer to see boost it needs something to compare and adjust? So with the 1 bar MAP it pretty much peg out and the motor will most likely run like crap and/or cause some major problems.

So for a NA motor you would need atleast a 2bar MAP sensor and some kind of software to program the PCM to read the new MAP sensor?

[Sweet98GA]

Don't quote me, but I don't think you would need a 2 bar unless you are boosting

The guy doing my tuning was originally going to run off the hptuners alone, and then I mentioned I got a 2 bar w/ the s/c kit and he said it would be more beneficial to use the 2 bar... so he'll be tuning that w/ the hp tuners

[Matt95GT]

Correct... 1 bar can only read from vacuum to atmospheric pressure (which is WOT for N/A engines). In fact, there's ongoing debate that positive pressure (boost) will actually cause misreadings (reading partial vac during boost - which will cause a lean condition) or damage the MAP sensor. For that reason, I use a check valve to bleed off boost pressure for the MAP.

2 bar (and 3 bar for higher boost) can sense both vac and boost and how much of it (up to the it's rating... 2 bar is about 14.5 PSI max for example). Since this range translates into a different electrical output, the PCM must be recalibrated. For example... 10 inHg of vacuum will give a different electrical reading on a 2 bar than on the stock 1 bar MAP. The recalibration is so that the PCM will have the correct expected electrical reading for 10 inHg once again, thus can deliver the right amount of fuel.

[VanishingImage]

Originally posted by Sweet98GA
Don't quote me, but I don't think you would need a 2 bar unless you are boosting

The guy doing my tuning was originally going to run off the hptuners alone, and then I mentioned I got a 2 bar w/ the s/c kit and he said it would be more beneficial to use the 2 bar... so he'll be tuning that w/ the hp tuners

correct,no need for a 2 or 3bar for NA motors. Just wanted to know what else needs to be done after getting a 2bar MAP,because the stock PCM won't know what to do with it.

[bballr4567]

http://www.robietherobot.com/storm/mapsensor.htm

There is a good site.

So if you get a 2 bar you will need to have the PCM reprogrammed to accept that right?? I suppose its a rather simple procedure though.

[loud2kse]

if you have a 00-02 2.4 then you can just get it reflashed at the dealer. If you have a pre 00 car, then you have to "fake" a 2 bar tune by using hptuners. You will lose some resolution in the tables, but it will still work out fine if properly done.

[VanishingImage]

even with the stock MAP sensor?

[Matt95GT]

Originally posted by loud2kse
if you have a 00-02 2.4 then you can just get it reflashed at the dealer. If you have a pre 00 car, then you have to "fake" a 2 bar tune by using hptuners. You will lose some resolution in the tables, but it will still work out fine if properly done.

Yup. That's really what the GM reflash is for - adapt to 2 bar MAP sensor and larger injectors.



Originally posted by VanishingImage
even with the stock MAP sensor?

What? Be more specific.

[VanishingImage]

loud mentioned using HPTuners to fake a 2bar map sensor. Was wondering if that ment still using the stock MAP sensor while using HPTuners

[Matt95GT]

Originally posted by VanishingImage
loud mentioned using HPTuners to fake a 2bar map sensor. Was wondering if that ment still using the stock MAP sensor while using HPTuners

Oh... he means use a GM 2 bar map, then use HPT to create your own 2 bar tune - much like a 'fake' version of the GM reprogram.

[VanishingImage]

oooooooh ok,got ya

[loud2kse]

Originally posted by Matt95GT
Oh... he means use a GM 2 bar map, then use HPT to create your own 2 bar tune - much like a 'fake' version of the GM reprogram.

bingo. you just lose some resolution of the scale... best way to explain it is like this

stock 1 bar tune
(vac at idle) 1 2 3 4 5 6 7 8 9 10 (wot/ full vac)
fake 2 bar tune
(vac at idle) 2 4 6 8 10 (full vac) 12 14 16 18 20 (boost at wot)
gm reflash
(vac at idle) 1 2 3 4 5 6 7 8 9 10 (full vac) 11 12 13 14 15 16 17 18 19 20 (boost at wot)

you just take bigger steps to the next level, and lose some of the finer resolution in the scale because you have to double the perameters to fake the 2 bar tune

hope that makes sense

[Matt95GT]

^The loss of resolution is nothing if you compare it to the alternative... having to use an FMU to raise fuel pressure under boost. (not that it's that bad either)

[urweak]

Originally posted by Matt95GT
In fact, there's ongoing debate that positive pressure (boost) will actually cause misreadings (reading partial vac during boost - which will cause a lean condition) or damage the MAP sensor. For that reason, I use a check valve to bleed off boost pressure for the MAP.

I just want to clear this up for anyone that reads it, when you say this you are only talking about a 1bar map. Because i kinda got confused reading it.

Originally posted by Matt95GT
2 bar (and 3 bar for higher boost) can sense both vac and boost and how much of it (up to the it's rating... 2 bar is about 14.5 PSI max for example).

Wanted to add that the term bar is a form of measurement, so 1 bar really means 14.5 PSI of atmospheric pressure at sea level. So really, when your talking about a 2 bar map sensor your saying that it can read 29 PSI at sea level (or atmospheric pressure PLUS the boost from a car with a turbo/supercharger up to an additional 14.5 PSI). But no body really says that a 1 bar map reads the 14.5 PSI b/c its already assumed that its reading the atmospheric pressure. Hope that helps people understand things a little better. In addition, if I made a mistake let me know.

[Matt95GT]

Originally posted by urweak
I just want to clear this up for anyone that reads it, when you say this you are only talking about a 1bar map. Because i kinda got confused reading it.


Right... for the 1 bar. (in that post, first paragraph = 1 bar, second = 2/3bar. Putting a check valve on a 2bar/3bar defeats the purpose of converting to one.

Originally posted by urweak
Wanted to add that the term bar is a form of measurement, so 1 bar really means 14.5 PSI of atmospheric pressure at sea level. So really, when your talking about a 2 bar map sensor your saying that it can read 29 PSI at sea level (or atmospheric pressure PLUS the boost from a car with a turbo/supercharger up to an additional 14.5 PSI). But no body really says that a 1 bar map reads the 14.5 PSI b/c its already assumed that its reading the atmospheric pressure. Hope that helps people understand things a little better. In addition, if I made a mistake let me know.

Correct. I think most people just prefer not to let atmospheric pressure confuse them... and only worry about pressure measurements above atmosphere (boost).

[urweak]

Originally posted by Matt95GT
Right... for the 1 bar. (in that post, first paragraph = 1 bar, second = 2/3bar. Putting a check valve on a 2bar/3bar defeats the purpose of converting to one.

Yea i understand, not picking on you or trying to correct you, just wanted to make it clear so no1 mistaked what you were trying to say.

[bballr4567]

Am I correct in thinking that you can purchase a two bar and plug it into the stock place and just reprogram the PCM correct??

[gdcpony]

Good thread since I have a turbo waiting to go into my wife's car when she blows the current engine. (I just have to build the engine to match it.)

[urweak]

Originally posted by bballr4567
Am I correct in thinking that you can purchase a two bar and plug it into the stock place and just reprogram the PCM correct??

I dont have first hand experience with this, so i may be wrong, but i think you would have to find one from a GM car, and use that. I dont think you could slap one on, from say a nissian or something.

[VanishingImage]

GM,most likely any of the SC'd vehicles,like Grand Prixs or Buick Regals. Then use HP Tuners to re-program the PCM like Matt and Red said

[bballr4567]

Well the actual 2 bar is only $40 on summit or other racing sites. I was just wondering if you could bolt it to the same place with stock parts and retune the PCM.

[VanishingImage]

just depends on the connection. Most likely you will have to splice into the original wiring.

[bballr4567]

MSD Stock Style MAP sensor (http://store.summitracing.com/partdetail.asp?autofilter=1&part=MSD%2D2312&N=700+0&autoview=sku)

See that one looks exactly stock, hell it even says stock style.

[grandam01]

Brought back from the dead, soo If my car is running lean like lets say around the 13.9 AFR would I benefit from getting a 2 bar MAP. Current setup CAI, Granatelli MAF(the only granatelli unit to date that is calibrated for our cars, I was there at their place and they had it on the flowbench) EGR delete, 180 T-Stat, Milzy Stock tuned PCM, and a cat back that is custom made by me ( I cut off the exhaust from the resonator back and put a glasspack muffler and some 2 in piping and have it mounted to exit out the driver side in front of the rear wheel.)

[Matt95GT]

Brought back from the dead, soo If my car is running lean like lets say around the 13.9 AFR would I benefit from getting a 2 bar MAP. Current setup CAI, Granatelli MAF(the only granatelli unit to date that is calibrated for our cars, I was there at their place and they had it on the flowbench) EGR delete, 180 T-Stat, Milzy Stock tuned PCM, and a cat back that is custom made by me ( I cut off the exhaust from the resonator back and put a glasspack muffler and some 2 in piping and have it mounted to exit out the driver side in front of the rear wheel.)

Please note that this thread is in the 2.4 LD9 engine section, which is speed-density managed. The 3400 is completely different, and the tuning process/options are different.

[grandam01]

OK sorry i searched it and saw a few 3400 guys post in here.

[urweak]

Brought back from the dead, soo If my car is running lean like lets say around the 13.9 AFR would I benefit from getting a 2 bar MAP. Current setup CAI, Granatelli MAF(the only granatelli unit to date that is calibrated for our cars, I was there at their place and they had it on the flowbench) EGR delete, 180 T-Stat, Milzy Stock tuned PCM, and a cat back that is custom made by me ( I cut off the exhaust from the resonator back and put a glasspack muffler and some 2 in piping and have it mounted to exit out the driver side in front of the rear wheel.)


It doesnt look like your running a turbo or supercharger, so the answer is no (not to mention what matt said). A 2 bar MAP is used to read boost pressure from a turbo or supercharger and is not ment to be used on a N/A car.