[GRUF78]

Gents,

2018 ZL1 1LE bought for track/DE events for wife. Oil pump failure at 6300 miles. GM replaced the short block. With new " engine", car uses 50% more fuel in a 20 minute track session (~9 gallons) than previously. At 6500 miles, left main cat fails and is replaced by GM. At 8500 miles, left main cat fails again-replaced by GM. At 9400 miles, left main cat fails again- replaced by GM. The engine has never been tuned. The car has an AWE track exhaust and a Rotofab intake and has since right after purchase..I.E,..the original engine ran with both of these mods for ~5K miles with no issues.

Additionally, after the new engine , the exhaust heat from the car has exponentially increased to the point of MELTING 3 sets of rear valance reflectors, the license plate illumination lamp and warping both rear tail light assemblies. Also, 2 sets of left bank exhaust bolts and studs have fallen out during this time. The black exhaust tips on the AWE exhaust have turned blue from the heat.

Dealer has run numerous diagnostics and all of the system and according to them, have checked good. They are trying to blame the aftermarket exhaust for the heat damage....


I believe the car is is over fueling a cylinder in the left bank somehow. However, the O2 sensors are good and no codes.

Thoughts? Thank you,

JM

[Gunkk]

Shouldn't be too hard to tell if you have too much fuel. You already see the symptoms that you do. The hard (?) part will is finding out why. My obvious guess, they f'd up the rebuild, but having aftermarket parts on the car doesn't help. At least one person melted their diffuser at Laguna by locking the car in stealth mode, so yes it is indeed possible to melt the rear plastic with an exhaust. Standard RF or Big Gulp? Putting it back to stock and troubleshooting it properly will avoid any second guessing at the dealer.

But that may not be possible for you, so it might be worth taking the car to a professional tuning shop and paying them a couple hundred for a good engine diagnosis. They're probably going to be better than any two-bit dealer tech at troubleshooting modded cars.

But if you can DIY to get some data, then do so:

1. MAF and/or MAP problem? IAT? COT triggered?

2. What are the fuel trims?

3. Use HPTuners to pull the fuel line pressure and injector timing data along with MAF/MAP/IAT, etc. etc..


Plenty of folks around here who can see what's right and wrong in the data if you present it.

[nighttowl]

Its extremely unlikely GM would cover anythign at this point. I would say the car was a lemon, but being 4-5 years old I believe its too late to make a claim against it.
If it were mine, I would either sell it as is or pull the engine and have someone else rebuild it with some more power. at least if it were sold the buyer would have the opportunity to buy a warranty from a dealer and have if fixed.

[GRUF78]

Actually, the motor/emissions system has a factory 60K warranty that was reset when the motor was redone. GM is on the hook for any motor/emissions related repair for up to 60K/5 yrs. The car has 9400 miles on it.

The TX lemon law has timed out as basically, it applies from purchase to 24 months. However, the Federal lemon law is still applicable-I have just hired an attorney and there is a clear case according to the firm. The difference is that GM will have to pay a cash settlement and I keep the car vice refunding my money for the full purchase price. I can expect ~10% of the purchase price as an offer. Attorney fees are paid by the manufacturer as per TX law.

Your advice on having it diagnosed is sound. However, should I chose to repair/retune/et al the motor at the shop, the existing 60K warranty is toast.

Somewhat of a catch-22.

Thank you,

JM

[d15b7]

Hi and sorry for your issues. First thing I’d do is put a wideband gauge in each bank (go to a performance shop and they will weld a bung in each bank preferably before the primary cat). Get a portable wide band with two readouts (or two separate wide band gauges; I like AEM) and see what your A/Fs are when you do wide open pulls on the Highway in 3rd/4th gears. Factory tune I’d figure should be low 11.X maybe? If it’s much lower than that then I’d start wondering if stuck injector or some other issue. Is it making good factory power?

[GRUF78]

All,

In comparing OE engine to "new" engine...

The new engine seems lazy to rev. Uses 9 gallons vs 6 gallons of fuel per track session now......The heat issue is just with the new engine. Over 5K of track miles with the OE engine and intake/exhaust mods with NO issue.

Thanks for your info,

JM

[Vtor_ZL1]

I'd have injectors tested.. almost sounds like one or more is "stuck" open or not closing completely. Diluted oil?

[wakespeak]

Make sure your intercooler is bled really well and you're not getting timing adjustments on the track resulting in dirty burns. I had to replace an 02 sensor at 10k miles.

[d15b7]

^ that’s a great idea - I had an O2 sensor fail on my tow vehicle (Chevy 2500HD 8.1 Vortec Allison) and the fuel mileage TANKED out (went from 9-10 mpg towing to like 6-7) and it felt lazy. I changed out both banks O2 (figured why not) and the truck immediately returned to normal.

[SFV1LE]

You already have a lot of info like excessive fuel consumption, exhaust temps etc.

You should get a wideband O2/AFR gauge, ideally one for each cylinder bank, and do a few relatively inexpensive but very useful tests:

1. Borescope camera inspection of cylinders through spark plug holes
2. Compression
3. Leak-down
4. Dyno pulls with dual AFR

These tests can help you gauge the health of the motor and diagnose the cause of the fueling issue. The information is good to have for anyone running their ZL1 for a few years on track, even if it doesn't get the answer you need. I think it will.

[GRUF78]

Gents,

Thanks for the info.

JM

[SFV1LE]

Originally Posted by GRUF78

Gents,

Thanks for the info.

JM

I'm a HBM ZLE owner since 2018 and track enthusiast...

As a person who tracks a Viper ACR and a ZLE I'm interested in hearing about how they compare on track. The ACR may be the best American track car ever, and the ZLE is up there but not on the same level. The ACR set some of the fastest laps ever at great tracks around the world: 1:28 at Laguna Seca vs. 1:34 for ZLE

How is the ACR in terms of ease of driving fast vs. ZLE? I don't think the ACR has the electronics the ZLE has like PTM. Does it put the power down well or lots of oversteer?

[taylorforschool@gmail.com]

Originally Posted by SFV1LE

I'm a HBM ZLE owner since 2018 and track enthusiast...

As a person who tracks a Viper ACR and a ZLE I'm interested in hearing about how they compare on track. The ACR may be the best American track car ever, and the ZLE is up there but not on the same level. The ACR set some of the fastest laps ever at great tracks around the world: 1:28 at Laguna Seca vs. 1:34 for ZLE

How is the ACR in terms of ease of driving fast vs. ZLE? I don't think the ACR has the electronics the ZLE has like PTM. Does it put the power down well or lots of oversteer?

I can tell you on the street the ACR feels incredible. I couldn’t imagine on the track.. my experience driving one was brief but I think the numbers are clear the snake is quicker. Probably would depend on the track

[nighttowl]

Originally Posted by taylorforschool@gmail.com

I can tell you on the street the ACR feels incredible. I couldn’t imagine on the track.. my experience driving one was brief but I think the numbers are clear the snake is quicker. Probably would depend on the track

Based on the ACR's 7:03 nurburgring lap I would think that the ACR would do best on larger tracks where it could stretch its legs. I seen the video, I dont think it could have gone much faster of a lap if at all. I would love to have one.

the ZLE ran a 7:16, but (and I dont remember the source) I read that a 7:08 was attained but not recorded.