suganuma

I just got my engine back up and running after a rebuild and single turbo conversion, etc etc

I had the haltech on for probably less than a week before rebuilding everything and cant remember how things were before the tear down.

Problem:

I have a Defi guage that at idle reads 11.5-12 inHg while the engine data page for the Haltech reads 18.5-19.

I have the boost gauge running off of one of the intake runners on the UIM while the MAP sensor is taking readings from the plenum right after the throttle body (stock location). I could see how there might be a small variation in pressures due to different locations, but a 7" difference seems pretty extreme to me - any of you have any ideas???

I have not gotten time to play with placement yet, but hopefully will soon. Give me some things to check for.

only thing i can think of is that maybe the map sensor is messed up - do they ever go bad??

TIA

RETed

Yeah, you're right...

Do the quick&dirty test - swap the vacuum leads and see what happens?
It could be that there's something clogging the port that's reads lower.


-Ted

suganuma

no diff in changing leads, but i did figure this out:

after freaking out for a while b/c it read even more of a difference up near the dorms than in town, I turned power onto the haltech without starting the engine and it reads around 6.6inHg with no load on the engine(obviously). So that is its starting point whereas the gauge starts at 0. (one uses absolute pressure versus gauge pressure)

had a little flashback to when i owned the power FC and did some quick calcs to find kinda the same results...

place where i took the 6.6inHg measurement is a little lower in altitude than the 7,258ft ASL that the dorms are at and where i did the calcs for, but they make sense - hopefully they are right on when i go to Denver which is about 2,000 ft lower in altitude.

6.6 inHg = about 3.24 psi

used this chart ( http://home.flash.net/~rfm2/altitude.htm ) to do some interpolations of differences in atmospheric pressure between 7,258ft ASL and seal level.

ends up pressure at 7,258 ft ASL is
22.826 in Hg
OR
11.211

seal level is
29.92 in Hg
OR
14.7 psi

so difference is:

7.094 in Hg
OR
3.489 psi

compared to my readings of 6.6inHg baseline for map sensor at a lower altitude than 7258ft ASL, this makes sense, but i'll have to do some other measurements at other altitudes to make sure and hopefuly things will go back to near 0 and little difference from the boost gauge as i get out of all these mountains and closer to Dallas.

-Nic

RETed

Wow, that's some troubleshooting!


-Ted

suganuma

I guess this mechanical engineering major and all these ridiculous Academy core classes like AeroEngr HAVE taught me something....