EFI log reading 18psi while mechanical reads 42psi

[NevadaLLY]

Anyone know why my sensors would only be reading 18psi while mechanical gauge is reading 42psi? Bad MAP? Maybe?

 

[slipclutchms]

What PID are logging ?

 

[jedenbeck]

LLYS will only read to 22 or 23 psi with the factory sensor. So I wouldn’t be to worried about the difference. Why it isn’t maxing out the sensor idk. Maybe a boost leak at the sensor. Mine was leaking there and I couldn’t tell on my mechanical gauge.

 

[NevadaLLY]

No PID’s. I know the sensor maxes out but my tuner has accounted for that. They’re only seeing total boost for compounds at 18psi. I did a leak test, found a small leak at the intercooler but can still build pressure. I’m expecting 50-55psi, mechanical reading 42 which is why I started looking in the first place. Now the tuner says my valley charger isn’t building any boost according to the data logs. I’m a bit puzzled.

 

[Bdsankey]

No PID’s. I know the sensor maxes out but my tuner has accounted for that. They’re only seeing total boost for compounds at 18psi. I did a leak test, found a small leak at the intercooler but can still build pressure. I’m expecting 50-55psi, mechanical reading 42 which is why I started looking in the first place. Now the tuner says my valley charger isn’t building any boost according to the data logs. I’m a bit puzzled.

Where is your mechanical gauge plumbed? You have to be referring to a PID if you're referencing a datalog. I'd assume you're looking at MAP or a boost pid?

 

[NevadaLLY]

Not sure why I was thinking PID vs codes. Oops!

Mechanical gauge is plumbed at welded bung fitting on the y-bridge provided by HSP diesel for the twin kit.

PID’s - yes measuring a data log for 0-80mph, 100% throttle, on max effort tune 5.

 

[NevadaLLY]

Boost PID is showing 18psi at 3000rpm

 

[Chevy1925]

if your tuner re-scaled the map sensor for what ever reason, that may be why.

hook the boost leak tester back up and start increasing boost 1-2psi at a time and see if the PID is following linearly to the 18psi and just holding or if its doing something funky.

 

[NevadaLLY]

Will do. Hopefully can accomplish this weekend when I put in the new IC. I’ll follow up with results.

 

[Mikey52]

I though I read somewhere and it might have been on older trucks but the internal boost would only read up to 20.

 

[NevadaLLY]

Tuner says it’s an issue. I’ll be correcting the small boost leak with a new intercooler. I’ll run the full boost test which should be:
1) hot side CAC
2) compound atmosphere charger inlet

The first test will look for leaks at intercooler boots and y-bridge. Once I’m satisfied there, the 2nd test will look for leaks between atmosphere and valley turbo, as well as pressurize the whole system but the hot side through will already be vetted.

I’ll then try to re-run my data log and see what’s next. Has anyone ever had a failed MAP? Is it an item that should be cleaned like the MAF?

 

[NevadaLLY]

Re-did all the tests, also upgraded my intercooler to CSF HD. Held test much better (slight leak down), but my mechanical gauge still topped out at 42PSI - now thinking its a gauge issue.