2021 ZL1 - Low Boost, less than 2 PSI
 

I have a 2021 ZL1 A10 and wanted to keep an eye on my MATs during a track event here in South Florida. I logged my session using the HP Tuners MPVI2 adapter and after reviewing the logs, noticed that my boost stayed below 2 PSI for the entire run, even under WOT. See attached photo and HPT log.

I checked the bypass valve set screw, took of the SC lid and the valve looks like it closes ok. The boost calculation in HPT shows MAP minus Barometric Pressure. The Barometric pressure shows 96 kPa which is about 14 PSI, I think that's right for South Florida sea level. It looks like my MAP is low at ~110 kPa which is about 16 psi.

I took a look at another ZL1 log and his kPa was in the 160's which makes sense and it was showing around 10 psi of boost. My MAF reading was also similar to the other ZL1.

Took the car to the dealer and they didn't want to help me or maybe couldn't help me.

Any suggestions?

If you are in the southflorida area and your car is stock....take it to autonation chevorlet pines...ask to see Guy in the service department...their techs are pretty good..

are you sure the channel config is correct?
the car would be really slow with only 2psi - you would immediately know there was something wrong.

Try using someone elses channel config.

That MAT temp of 149°F is about right for a well maintained stock LT4 IC system with 195°F ECT in 95°F ambient. It picked up ~7° after the pull so something was making heat due what you'd hope was boost.

The MAF flow ~matches a stock LT4 dyno log I found. It made about 170 kPa on the MAP @ 4600 lb/min on MAF. You are hitting 108 kPa @ 4500 lb/min and he rev'd a little higher.

Maybe a bad MAP sensor or logged channels? Not much to go on with parameters you logged, try the set I uploaded. There some stuff in there for M6 car (clutch related) and WB02, ignore those for your logging purposes.

Thanks for the reply! I loaded your channel set and did a few runs. See attached. The second set I did w/o the A/C running, not that it made a difference. What do you think?

I tried with another channel config and same results. You are right, the car does not seem lacking in power. I would think missing 8 psi of boost would be significant. Hopefully just a sensor issue.

I appreciate the referral. I will reach out to Guy and see if he will help. Thanks.

I can't wait for someone to figure this out, this is some weird data your car is producing.

The MAP is isn't following the MAF above 40kPa (6 psi / -8.7 psia) in run 2 but somehow in run 1 it doesn't follow above 100 kpA (14.7 psi / 0 psia). That's confusing... Some of the runs the dynamic airflow ramps very linearly (as if its using another filtered source) and sometimes it is dead flat. Neither are typical. Dynamic uses MAP, MAF, TPS, RPM, IAT, and VE inputs. MAF, IAT, RPM, and TPS look nominal, again that points at MAP sensor.

You have some very weird behavior with Delivered Tq vs. Immediate/Predicted Tq. There are times when delivered is normal but the Immediate/Predicted are very low and no TqMgtAdv is coming into play when I would have thought it should, see attachment.

Low side/High side fueling looks fine. You have some knock which is typical of a stock tune, what kind of fuel are you running?

Is this a stock tune?

You're logging the wrong MAP PID. You have to use the Hi Res Non SAE MAP PID.

His pid is correct and matches his boost pid. Any of the intake manifold pressure will use the generic manifold pressure sensor.


His boost pid hes using the Maths, Airflow, boost which is correct.

I have found on the LT4 you have to log the PID, Manifold Absolute Pressure - Hi Res in addition to Intake Manifold Absolute Pressure for proper MAP readings. To be honest I had to do this so long ago when Gen V stuff was new that I forgot exactly why. But I do remember having the exact same issues with the LT4 where the boost reference and MAP reading was incorrect. Do you have another suggested fix for the incorrect value?

We solved this on HPTuners forum long ago....could the ZL1 have the same nuance? It just might be possible.....


https://forum.hptuners.com/showthrea...-LT4-Questions

https://forum.hptuners.com/showthrea...e-do-I-find-it

https://forum.hptuners.com/showthrea...pressure-ratio

Hi, I added the MAP Hi-Res and did a couple more runs. It looks like the Hi-Res gets to over 160 kPa but then drops down suddenly mid pull. Does this look like the right sensor to read? See attached runs.

Hi, yes the car is stock. I'm running 93 octane pump gas.

Compare vs a stock 2019 ZL1 WOT Log
 

Here's a stock log that shows both the MAP and MAP Hi Res as the same with a healthy 10 psi boost and 160+ kPa MAP reading...I don't think the issue is with the channels on HP Tuners...unless something changed from the 2019 to 2021 model.