[travislambert]

I'm a regular participant of HPDEs at PittRace. I was at the track yesterday and power seemed to be underwhelming on corner exit. Normally, I have to be careful with the throttle to avoid wheel spin, but yesterday, I could just mash the throttle at the apex and wait. My MPH on the straights was noticeably less, to the tune of 6-8 MPH on the ~1/2 mile front stretch.

Overall, my lap times were very consistent, but up 3-4 seconds... ~1:56 instead of the ~1:52-1:53s I can normally achieve on R7s.

• The temperature was in the 80s, about 82 for my last session. I didn't measure the humidity, but it seemed lower than normal.
• PTM was set to Sport 1, which is where I run almost always.
• I've ran plenty of laps in 90+ temps and haven't noticed such a significant difference in power/lap times.
• The engine seemed to be running fine... no misses or hesitation.
• Max engine oil temp was 271.
• Max water temp was 217.
• Tire grip was fine, max G was ~1.5
• Air filter had a very small amount of dirt trapped, certainly nothing above normal.
• Heat exchangers appear mostly clean... a few bugs, but nothing that should have a significant impact.
• Minimum oil pressure was 37.1 psi, Max oil pressure was 69 psi.
• For the last session, I filled up with 100 octane, just to help rule out knock. There was no change in performance.

My first thought was an intercooler pump problem, but I've ruled that out. The pump is working fine. Unfortunately, the PDR doesn't capture IATs or boost pressure. I know that would be useful, but I don't have it.

Anyway, I'm not sure what happened, but I have another track day in two weeks and I'd like to figure out what's going on before then. I've considered unhooking the battery so the computer will reset.

Has anyone else had a similar experience with the ZL1? Thoughts?

[Joshinator99]

Probably Cat Over Temp kicking in... ECU dumps fuel at your engine to keep the cats from melting but really cuts into power. My brother has a tuned 680 RWHP ‘16 Z06 Vette. When we were at the 1/4 mile track this weekend, on his last run of the day he shut COT off and picked up,*5 MPH* in the 1/4...

[travislambert]

Originally Posted by Joshinator99

Probably Cat Over Temp kicking in... ECU dumps fuel at your engine to keep the cats from melting but really cuts into power. My brother has a tuned 680 RWHP ‘16 Z06 Vette. When we were at the 1/4 mile track this weekend, on his last run of the day he shut COT off and picked up,*5 MPH* in the 1/4...

Yeah, possibly, but I don't recall having problems like this last summer. Of course, maybe the CATs are becoming a little more restrictive with age causing the temps to increase. My car only has 6,400 miles on it though.

[Joshinator99]

Originally Posted by travislambert

Yeah, possibly, but I don't recall having problems like this last summer. Of course, maybe the CATs are becoming a little more restrictive with age causing the temps to increase. My car only has 6,400 miles on it though.

I would datalog some runs, especially if you’re under WOT for a bit. Not sure if you have HP Tuners, but that is a great way to log it. You’ll be able to review a bunch of data points at once.

[travislambert]

Originally Posted by Joshinator99

I would datalog some runs, especially if you’re under WOT for a bit. Not sure if you have HP Tuners, but that is a great way to log it. You’ll be able to review a bunch of data points at once.

Yeah, I have HP Tuners (my car still has stock tune though).

I would have loved to have had my laptop at the track yesterday. I certainly would have grabbed some logs. I'll bring it with me to my next track day on the 16th.

Before the track day I'll probably drop the exhaust and visually inspect the cats...maybe do a backpressure test too.

[TrackClub]

New, or old tires? R7s fall off quite a bit with age.

[RUQWIKR]

On the PDR data, does the Pi Toolbox version have that info? It has a TON more data to look at vs. regular Cosworth Toolbox.

https://www.cosworth.com/products/toolbox/


It looks like it has what you are looking for based on zooming into a screenshot here:

https://www.corvetteforum.com/forums...i-toolbox.html

[ICTsccaCamaro]

Sounds like the PTM or drive mode switch got bumped and the car was pulling power out of corners to prevent traction loss. If your truly running in sport 1 it is very intrusive and will pull throttle at almost every corner, if your on R7's you should be at the level to run RACE mode at the track.

[travislambert]

Originally Posted by TrackClub

New, or old tires? R7s fall off quite a bit with age.

They were brand new.

[travislambert]

Originally Posted by ICTsccaCamaro

Sounds like the PTM or drive mode switch got bumped and the car was pulling power out of corners to prevent traction loss. If your truly running in sport 1 it is very intrusive and will pull throttle at almost every corner, if your on R7's you should be at the level to run RACE mode at the track.

Agreed for the drive mode switch, but the overlays on the PDR video confirm I was in Sport 1...But that's exactly how the car felt. It was almost like it was in Dry mode or maybe not in PTM mode at all. Of course with the R7, it's easier to feel the power being pulled because there's usually some traction left on the table. I'm used to that feeling... this was a little worse.

I understand what you are saying about Race mode. I could absolutely run in Race and I have... but I've also done back-to-back comparisons on R7s with Sport 1 and Race and the lap times are almost always within one second. To me, since I'm just running for fun anyway, the stability control to help save my butt when something unexpected happens is worth the time trade-off. That's why I usually run in Sport 1. With that said, I probably should have ran a few laps in Race on Monday just as a test to help narrow the problem. If I don't figure out the issue before my next track event, I'll move it over to Race for a few laps.

[travislambert]

Originally Posted by RUQWIKR

On the PDR data, does the Pi Toolbox version have that info? It has a TON more data to look at vs. regular Cosworth Toolbox.

https://www.cosworth.com/products/toolbox/


It looks like it has what you are looking for based on zooming into a screenshot here:

https://www.corvetteforum.com/forums...i-toolbox.html

Yep. Pi Toolbox is much more powerful! I've been using it for a while now. When I first tested the DSSV swap last year, I used PiToolbox for much of the data comparison.
https://www.camaro6.com/forums/showp...5&postcount=75

[Juiced1]

Intake temps will always rob power. On a hotter day your temps are probably soaring into the 170s and up. The ZL1 has a decent system but its not perfect. Do you have a reservoir? They are nice to have so you can check your fluid levels and ensure that you always have fluid pressure on the head of the pump. I can't even count the number of times we have taken the intercooler line off of a LT4 and had no fluid come out. A little air in the line can really shut down the fun.

[TheRealJA105]

No limp mode issues though Travis? I was at Watkins Glen last Wednesday and my car went into limp mode in 2 out of 5 sessions. A stock ZLE and Z06 also had issues and it was only 78 degrees there so I'm wondering about humidity. I am going to re-bleed my intercooler circuit, but I am also wondering if it is some electrical problem from sensors acting up under heat and shutting me down. I get no CEL, only the Reduced engine power warning, then after cooling down, pitting, and shutting it off for awhile it's fine when restarted.

[travislambert]

Originally Posted by Juiced1

Intake temps will always rob power. On a hotter day your temps are probably soaring into the 170s and up. The ZL1 has a decent system but its not perfect. Do you have a reservoir? They are nice to have so you can check your fluid levels and ensure that you always have fluid pressure on the head of the pump. I can't even count the number of times we have taken the intercooler line off of a LT4 and had no fluid come out. A little air in the line can really shut down the fun.

No question the temps play a role, but this problem seemed to go beyond that. Comparing to laps to last August, I was consistently slower this year. In a couple of weeks, I'll be sure to grab logs while on the track. That should paint a better picture of what's going on.

No reservoir. My engine and cooling system is all completely stock and has never been touched. Just to be sure, I'll double-check for air in the lines. I'm thinking about upgrading the heat exchangers anyway.