Boost guage compared to enginuity

Phibs · Post by **Phibs** » Sun Nov 18, 2007 7:32 pm

So my boost guage hit about 24 PSI and enginuity read a max of 22.20 PSI, which is right? The parameter in enginuity I logged was manifold pressure, corrected.

zaxrex · Post by **zaxrex** » Sun Nov 18, 2007 9:40 pm

Where did you tap for the pressure guage? Where is the engine receiving pressure information from? If they are in different locations, then there can be some differences.

You say your software is showing "corrected" pressure, what parameters and calculations is the ECU using to "correct" the pressure?

Try switching the mode to uncorrected and see if it then matches your gauge. If it jumps up by ~14 PSI, then all it is doing is subtracting "atmospheric" pressure from the total pressure. This will give you a reading of the pressure above atmospheric withing the manifold.

Phibs · Post by **Phibs** » Sun Nov 18, 2007 11:06 pm

zaxrex wrote:Where did you tap for the pressure guage? Where is the engine receiving pressure information from? If they are in different locations, then there can be some differences.

You say your software is showing "corrected" pressure, what parameters and calculations is the ECU using to "correct" the pressure?

Try switching the mode to uncorrected and see if it then matches your gauge. If it jumps up by ~14 PSI, then all it is doing is subtracting "atmospheric" pressure from the total pressure. This will give you a reading of the pressure above atmospheric withing the manifold.

Guage is tapped on the BOV, I assume the ECU gets it from the Manifold tap. I will check both next time, corrected vs uncorrected. Thanks for the response.

midnit · Post by **midnit** » Mon Nov 19, 2007 12:14 am

I know this is a bit OT, but...

Bryan, I just want to say thanks to you and Ben for helping out as much as you guys did with installing the boost gauge with me. And thanks a bunch for picking that stuff up for me in Ashburn!

You're awesome man, I appreciate it!

Phibs · Post by **Phibs** » Mon Nov 19, 2007 10:35 am

NP dude, you get it installed yet? Post up some pics! ( I need to take some of mine too )

Forevapmp · Post by **Forevapmp** » Mon Nov 19, 2007 12:14 pm

in for pics........

well I've seen them in person......

It was nice hangin out with ya'll...

Bryan, I still think it's a boost leak somewhere.....

Phibs · Post by **Phibs** » Mon Nov 19, 2007 1:33 pm

Forevapmp wrote:in for pics........

well I've seen them in person...... It was nice hangin out with ya'll...

Bryan, I still think it's a boost leak somewhere.....

Nice hanging out with you for sure, next time you can come visit us in VA.
lol it'd show up in the logs if I was boost leakin bro

gsx-lex · Post by **gsx-lex** » Mon Nov 19, 2007 4:32 pm

I've seen mechanical gauges that have been of by as much as 3 psi! I'm not very familiar with enginuity stuff, but I will always trust a map sensor over a mechanical gauge. What does your enginuity gauge read when the car is off (log it with ignition on but car turned off).

Phibs · Post by **Phibs** » Mon Nov 19, 2007 6:07 pm

gsx-lex wrote:I've seen mechanical gauges that have been of by as much as 3 psi! I'm not very familiar with enginuity stuff, but I will always trust a map sensor over a mechanical gauge. What does your enginuity gauge read when the car is off (log it with ignition on but car turned off).

-20, Vacuum. The sensors are reading from different places so that could account for it. But 3 PSI is about what it would be off... hmm

Post by **Sabre** » Mon Nov 19, 2007 7:11 pm

Alex meant when the car isn't running at all. -20 mmHg is definitely with the engine on at idle

FYI, my hydra reads about 3PSI below my mechanical guage tells me.
aka
Mechnical = 21PSI
Hydra = 18PSI

and they are T'ed off of the same connection!

Phibs · Post by **Phibs** » Mon Nov 19, 2007 7:13 pm

Sabre wrote:Alex meant when the car isn't running at all. -20 mmHg is definitely with the engine on at idle

FYI, my hydra reads about 3PSI below my mechanical guage tells me.
aka
Mechnical = 21PSI
Hydra = 18PSI

and they are T'ed off of the same connection!

Oops I'll check next time I go out there. Currently trying to hook up this
LC-1 Wideband sensor from Darrin. With a CAT in my DP I know the reading will be off, but will it be off by some reliable constant? The directions say basically only use the tail pipe mount option if the vehicle has no cat

LOL that's awesome

Post by **Sabre** » Mon Nov 19, 2007 7:48 pm

Phibs wrote:With a CAT in my DP I know the reading will be off, but will it be off by some reliable constant?

Yep, it will be off, but by a constant

Easy way to fix that:
At idle, you'll probably see 14.7AFR's in Enginuity and 15.7AFR's (for instance) at the wideband. You can then just subtract 1 from the WB and you'll get your actuals. There is the problem that as the gas velocity increases, the cat will not be as efficent and will vary a little. I don't think that little bit is much to be worried about though.

Phibs · Post by **Phibs** » Mon Nov 19, 2007 8:12 pm

Sabre wrote:
Phibs wrote:With a CAT in my DP I know the reading will be off, but will it be off by some reliable constant?
Yep, it will be off, but by a constant Easy way to fix that:
At idle, you'll probably see 14.7AFR's in Enginuity and 15.7AFR's (for instance) at the wideband. You can then just subtract 1 from the WB and you'll get your actuals. There is the problem that as the gas velocity increases, the cat will not be as efficent and will vary a little. I don't think that little bit is much to be worried about though.

Sweet. I have the unit powered and calibrated. If anyone wants to help tomorrow @ the meet we can take it for a logging run