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Discussion Starter #1
Need some clarification.

One atmosphere = 14.7 pounds. If I intend not to exceed 29.4 pounds of boost (2 Bar - Stock MAF Sensors), what would be the reason to upgrade to 3 BAR sensors.

I purchased a set from Werks a couple years ago and have not got around to installing them. I am currently running a Trifecta custom tune and regularly pull 25 lbs. I am now upgrading my turbo to a EFR6758, but once again, do not expect to exceed 29.4 pounds of boost. (Are my expectations wrong?)

I am obviously missing something here. Even the GMPP upgrade requires the installation of 3 BAR sensors. There has to be other benefits associated.

Can someone please explain, and if you have the time and knowledge clarify each individual gain from swapping these guys out.
 

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First it's MAP sensors (manifold air pressure) not MAF (mass air flow) :)

Then, you're missing the fact that 3 bar means from 0 PSI to 29.4 PSI. The stock 2.7 (?) bar sensors only measure up to 24.5 PSI. (All figures approximate.)
 

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Actually, 0 bar = 0 psi. 1 bar = 14.504. 2 bar = 29.008. 3 bar = 43.511 psi.

So if you're going to pull over 29 psi the 2 bar sensor would not be able to measure it.
 

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Actually, 0 bar = 0 psi. 1 bar = 14.504. 2 bar = 29.008. 3 bar = 43.511 psi.

So if you're going to pull over 29 psi the 2 bar sensor would not be able to measure it.
Kinda true, in that 1 bar = 14.504 PSI. But otherwise misleading and why things get confusing when translating from bar to PSI. When we talk about measuring 29 PSI, we are talking about 29 PSI positive pressure (i.e. 29 PSI above sea-level atmospheric pressure) which is actually 29+14.5, or roughly 44.5 PSI above vacuum. When we talk about pressures in bars (or kPa) we mean absolute, which is actually less confusing. Thus a (fictitious) 2 bar sensor, basically means a 2 bar RANGE, i.e. 0 bar to 2 bar, or -14.5 PSI to +14.5 PSI positive pressure. (Note: 1 Bar = 1 ATM = 100kPascals (kPa) = 14.50377 PSI (above vacuum))


That said, now I'm back at my computer I can give the accurate figures for the T/MAP sensors:

- The stock sensor is 2.7 BAR, with an accurate measurement range of 11 kPa to 270 kPa (-12.9 to +24.5 PSI).
- The GMPP Bosch sensor is 3 BAR, with an accurate measurement range of 11 kPa to 307 kPa (-12.9 to +30 PSI).
 

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I should have stayed in school. so lets say you have the 2 bar sensors but upgrade your turbo / tune that can produce over 29 PSI. what happens? does the ECM throw a code or does the whole thing just explode?
 

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Need some clarification.

One atmosphere = 14.7 pounds. If I intend not to exceed 29.4 pounds of boost (2 Bar - Stock MAF Sensors), what would be the reason to upgrade to 3 BAR sensors.

I purchased a set from Werks a couple years ago and have not got around to installing them. I am currently running a Trifecta custom tune and regularly pull 25 lbs. I am now upgrading my turbo to a EFR6758, but once again, do not expect to exceed 29.4 pounds of boost. (Are my expectations wrong?)

I am obviously missing something here. Even the GMPP upgrade requires the installation of 3 BAR sensors. There has to be other benefits associated.

Can someone please explain, and if you have the time and knowledge clarify each individual gain from swapping these guys out.

I was happy to hear you went with the EFR. You will be very, very happy that you did once you start driving it. On that 2 bar sensor issue, I can tell you from experience that you can get away using the stock sensors if you stay under that 24.5 max boost cut off. Dave encouraged me to go 3 bar when I was doing my conversion, but I got cheap feeling I was bleeding too much money, so I stayed with stock and he agreed to tune me with that set up. I asked for max boost not over 24 to help protect the engine on stock internals. In the two seasons I've been driving it, the only code I ever threw was an over boost once last year. It must have popped over the max for a moment and tripped the code. I just cleared it and have no trouble since. In hind sight however, I wish I had gone for the 3 bar as I would have more head room and probably more accurate pressure reading at my max boost settings------hell it would have been less than 100 buck more.

I would like however to encourage you to consider asking Dave to tune it. I realize that's more money out of pocket buying HP tuner, but consider these points. Dave drives and races these cars. He has developed and refined his tunes on his dyno, which applies to his EFR kits-----he really knows these engines from first hand experience. Also with HP tuner, you can look at all the figures you are reading with the data logs. With Trifecta, you are never privy to seeing them.

Which exhaust manifold did you go with-----Dave's original one, or the upgrade "racing" model made by Stainless?
 

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I should have stayed in school. so lets say you have the 2 bar sensors but upgrade your turbo / tune that can produce over 29 PSI. what happens? does the ECM throw a code or does the whole thing just explode?
Seriously? Why don't you try it and find out? :devil:

In reality the ECM expects a reading of max 5V (actually, something like max 4.75V for linear readings) from the MAP. If the tune assumes this equates to 29 PSI (say) when it really means 24.5 PSI it means the closed-circuit fuel and boost management is now open circuit. A completely useless scenario.

By the way (again) NO-ONE in a kappa has 2-bar sensors.
 

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I stand humbly corrected Soup.

I only have a one bar sensor and it went off about 7:30 this morning. (Been a week from hell.) So I'll clear the code by stopping at one bar on my way home.
 

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I'd love to soup but I don't see my kappa feeling 29psi anytime soon. Bummer. just curious that's all. sounds like the only difference is getting a code for overboost but either sensor being 1, 2 or 8 bar affects actual performance.
 

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So I'll clear the code by stopping at one bar on my way home.
Stopping at 3 bars is much better for your performance than stopping at 1 bar. Just sayin'

EDIT: As long as you're not driving :willy:
 

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Discussion Starter #11
So the question still remains. If I plan to never go over 25psi, why would I upgrade the sensors?
 

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So the question still remains. If I plan to never go over 25psi, why would I upgrade the sensors?
Well, you wouldn't. But that's not what you asked. You said:

If I intend not to exceed 29.4 pounds of boost (2 Bar - Stock MAF Sensors), what would be the reason to upgrade to 3 BAR sensors.
So... if you stay under 25 PSI boost, you can stay with the factory MAPs. If you want to go up to 29 PSI of boost, you have to replace them with the 3 bar sensors. OK?
 

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Discussion Starter #13
Hey Soup. This thread seems to of got buried.

OK. I got it now. Guess I should have read my original post. Plus, I was missing the connection between boost PSI and the effective value of a Bar. Confusing - but I got it.
 

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Well, you wouldn't. But that's not what you asked. You said:

So... if you stay under 25 PSI boost, you can stay with the factory MAPs. If you want to go up to 29 PSI of boost, you have to replace them with the 3 bar sensors. OK?
And really from what I've seen GM went with 3 bar on the GMPP tune just because (I think) they wanted a little leeway built in. I have once seen 23 psi briefly, so it seems just like the 2.7 handled the stock 18ish max psi, they built in the same amount of leeway. I'm not sure what these cost, but I think they were just ensuring there would be no chance a GMPP tune would push the limit of the MAP sensor and flip a code/cause issues.
 

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And really from what I've seen GM went with 3 bar on the GMPP tune just because (I think) they wanted a little leeway built in. I have once seen 23 psi briefly, so it seems just like the 2.7 handled the stock 18ish max psi, they built in the same amount of leeway. I'm not sure what these cost, but I think they were just ensuring there would be no chance a GMPP tune would push the limit of the MAP sensor and flip a code/cause issues.
I've also seen they did it for "Emissions"... But I can tell you that I can make it go to 24PSI (4th gear, 60 mph, WOT) and that's at (close to) sea level. Up in the mountains of Colorado that'd be good for several PSI more than that - beyond the stock sensors anyway.
 

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I think P werks sells these with pigtails for $96.00
 
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