reading low boost on new whipple.... accept it and move on?

[peiserg]

Guys, I just had a 3.4 installed along with the MAFia. The 19psi system is only reading 12.5 on my stock gauge. This is inherent to the MAFia system? Assuming this is how life is, is my gauge now "relative" vs. absolute? I.e. from now on, i just assume 12.5 psi means full boost, and if it reads 10psi, then there is an issue? with the pulley and tune, the gauge pegged at 15. I kind of expected the same to happen, except faster.

dyno sheets to follow, along with AFR and boost graphs.

 

[BlackICE]

It is inherent to most all tunes used with the Whipple, no worries.

 

[nota4re]

Gerry, as we discussed, the GT calculates boost as opposed to reading it directly. Since it "knows" RPM, displacement, temps, etc. AND how much air is being ingested via the MAF sensor - it has everything it needs to calculate boost and then display it. BUT, when a MAFia is installed, the function of the MAFia is to scale down the MAF signal so that with more boost from the Whipple, the MAF will not hit it's max 5v output. (If the ECU sees a 5v+ signal from the MAF, it will assume a fault in the sesnor and it will throw a CEL and put the car in limp mode.) A MAFia is used to prevent this from occuring and as long as the tune is built knowing that a MAFia is being employed, everyone is happy.... except for the poor 'ol boost gauge.

 

[peiserg]

Kendall, I guess the thrust of the question was more along the lines of "is the gauge still useful at all... can i at least make "relative" judgements from it?" i.e. it says 12.5 psi, will it one morning start saying 14 psi, then the next day 12.2 psi? or is it always going to be 12.5 psi, and therefore if it says 11 psi i know there is an issue?

 

[33Bravo]

Gerry, as we discussed, the GT calculates boost as opposed to reading it directly. Since it "knows" RPM, displacement, temps, etc. AND how much air is being ingested via the MAF sensor - it has everything it needs to calculate boost and then display it. BUT, when a MAFia is installed, the function of the MAFia is to scale down the MAF signal so that with more boost from the Whipple, the MAF will not hit it's max 5v output. (If the ECU sees a 5v+ signal from the MAF, it will assume a fault in the sesnor and it will throw a CEL and put the car in limp mode.) A MAFia is used to prevent this from occuring and as long as the tune is built knowing that a MAFia is being employed, everyone is happy.... except for the poor 'ol boost gauge.

Hi Kendall (Happy Holidays!!)

This is curious.. We've discussed here (and you always have very useful information) about my boost situation (the 2.5" Kenne Bell pulley).. Per your suggestion - I'm having Torrie up this spring to make sure I have the best tune. Although my boost gauge pegs with the 2.5" pulley - is it a fair assumption thawt I've not hit the 5v max (I don't have a MAFia) - because I have not thrown a CEL and hit limp mode?

Thanks

 

[nota4re]

Although my boost gauge pegs with the 2.5" pulley - is it a fair assumption thawt I've not hit the 5v max (I don't have a MAFia) - because I have not thrown a CEL and hit limp mode?

That's correct. If your MAF gave a 5.0v signal to the ECU, the ECU would let you know right away of the fault. There are different degrees of CEL's - all of them manifest themselvelse in the illumination of the light. However, some faults are minor and not deemed engine/safety threatening. For example, a catalytic efficiency fault code will simply display the CEL and the car will remain perfectly driveable. If the MAF gives the ECU a bad signal, the ECU is going to consider that the MAF is no longer reliable and since the MAF plays a BIG role in the safe operation of the engine, the ECU will immediately go into limp mode. You'd know it!

 

[paul b]

Would using a mechanical gauge help, if only used as a diagnostic tool to remove any doubts.

 

[tmcphail]

Would using a mechanical gauge help, if only used as a diagnostic tool to remove any doubts.

Yes, that would show exact manifold Vacuum and Pressure.

 

[tmcphail]

Hi Kendall (Happy Holidays!!)

This is curious.. We've discussed here (and you always have very useful information) about my boost situation (the 2.5" Kenne Bell pulley).. Per your suggestion - I'm having Torrie up this spring to make sure I have the best tune. Although my boost gauge pegs with the 2.5" pulley - is it a fair assumption thawt I've not hit the 5v max (I don't have a MAFia) - because I have not thrown a CEL and hit limp mode?

Thanks

You can easily hit 5v with a 2.8 Pulley and everything else being stock for the most part. So I can almost guarantee you have gone past it unless you don't spin the motor very high. What I do is set the actually MAF AD Count ceiling all the way up to 1023 that way in the event you go past the factory roof of 980 it won't invoke an error. I would estimate whatever calibration resides on your car has this configured already.

 

[33Bravo]

You can easily hit 5v with a 2.8 Pulley and everything else being stock for the most part. So I can almost guarantee you have gone past it unless you don't spin the motor very high. What I do is set the actually MAF AD Count ceiling all the way up to 1023 that way in the event you go past the factory roof of 980 it won't invoke an error. I would estimate whatever calibration resides on your car has this configured already.

Well - I've frequently brought the engine up to redline - but never have thrown a CEL (or gone into limp mode). Makes the mystery of my 2.5" pulley even more intriguing.
The good news is that you are coming this spring - and getting everything sorted out!

 

[tmcphail]

Well - I've frequently brought the engine up to redline - but never have thrown a CEL (or gone into limp mode). Makes the mystery of my 2.5" pulley even more intriguing.
The good news is that you are coming this spring - and getting everything sorted out!

Completely agreed.

 

[2112]

Has anyone run a mechanical gauge and been done with it?

In Marine engines costing in excess of $60,000 a pop, all critical gauges are mechanical. Guessing over. :bored

 

[tmcphail]

I use a GM 3 bar map sensor tied into my TSX so I can monitor and log it in my GT. I haven't looked at my factory boost gauge in years.

 

[Black GT]

I have a factory looking 30 pound mechanical gauge I got here on the forum. Works great and looks stock. I am a mile high and I see about 19.5psi. I think I have a 21 or 22 pulley can't remember.

 

[2112]

I have a factory looking 30 pound mechanical gauge I got here on the forum. Works great and looks stock. I am a mile high and I see about 19.5psi. I think I have a 21 or 22 pulley can't remember.

Where do you pick up the manifold pressure? Are you running Hi-temp Teflon tubing?

Any pics of the sender location?

Thank you!

 

[tmcphail]

Where do you pick up the manifold pressure? Are you running Hi-temp Teflon tubing?

Any pics of the sender location?

Thank you!

I have a boost/vac line that runs into the passenger compartment and connects to my boost controller. I tee'd into that and have the 3 bar sensor chilling out behind the driver's seat.

 

[2112]

Where are you picking up at the Manifold?

 

[tmcphail]

Where are you picking up at the Manifold?

See arrow at bottom right.

 

[2112]

Just below the fuel rail on the intake itself?

Thanks for posting. Saved to hard drive. :thumbsup

Are you using any special type of hose into the cockpit?

 

[tmcphail]

That's correct, there is an available port there. I have always just used standard boost/vac hose.