[rpaddicted]

Hello everyone,


After having had some problems with the supercharger cooling system (previous post), I now have a weird problem which I'm going to try to describe the best I can :


My car is a 2018 ZL1 1LE from Canada and has been imported to France in 2019. It is 100% stock mecanically.





ONLY in 2nd and 3rd gear, when I accelerate full throttle around 50 km/h (30 mph), the car doesn't make full power. The supercharger gauge remains low for a few seconds, the car accelerates very slowly and then makes full boost after I hear a "bang".
It only happens in 2nd and 3rd gear, not in any of the other gears.
It is always at the same RPM, around 2300 in 2nd gear, around 1900 in 3rd gear. It happens every single time at these RPMs.
It does not happen if I floor it below these figures : if I accelerate full throttle at 1500 rpm in 2nd or 3rd gear the acceleration is normal.
It does not come from the traction control or diff : it is still happening with everything turned off.


I thought I had a problem with the map but it seems it is 100% stock. There is no warning light, nothing.


My mechanic noticed that when he unplugs the speed sensor on the gearbox the problem disappears (but of course no speed is displayed and a lot of warning lights pop up).



It is not the biggest of problems and when you're used to it you can avoid it, but still... My mechanic and I are at a loss here.
It's as though something is banning the car to make full boost at these precise rpms, so weird...


Many thanks for any advice !

[radz28]

Do you have access to a scanner-like tool, like HPTuners? That’s where I’d start. Stupid question - could this be Traction Control or Stability Control because the tires are spinning. If you’re on OEM tires, they’re recognized to be traction-limited until they’re warm.

[LiqTenExp]

Can you describe the method you use to "turn everything off" referring to TC/SC?

[nighttowl]

A bang?
Im kind of wondering if this is cat related.

[zxspeedspec]

It definitely does sound like there's something going on, but at the same time 3rd gear at 2300 RPM doesn't pull hard even without a problem. The 2nd gear definitely seems like more of a symptom of the underlying problem. I'd get that shorted and worry less about not pulling from 3rd gear at 2300 RPMs.

I drive under 30 MPH in my neighboring in 4th and right when my back tires leave my neighborhood I drop it into 3rd and WOT it until the intersection. That initial 3rd gear pull is extremely weak until the RPMs climb above 4000 so I would consider that normal.

[rpaddicted]

It pulls harder in 4th at 1500 rpm than in 3rd at 2000, so there is definitely a problem.


I also wonder if this is cat related since I have 2 O2 sensors that have failed during the summer (with warning light on dash) : but the problem was there before... I actually wonder if the problem I'm describing caused the O2 sensors to fail !



I will try to make a short video of the problem next week.

[rpaddicted]

Originally Posted by LiqTenExp

Can you describe the method you use to "turn everything off" referring to TC/SC?

You hold the button for more than 5 seconds if I remember correctly. Anyway I know this is not the cause, I have several sports cars and know fairly well how TC and ESP works

[nighttowl]

Have your guy pull one of the cats and see what it looks like.
has you pulled any spark plugs?

[rpaddicted]

Here is a short clip where you can see the problem : on the first acceleration in 2nd gear I am full throttle (green bars) but the car has almost no acceleration for several seconds. It is not an ESP problem as you can see further down that when I do accelerate at 3000 RPM then it's normal.





https://www.youtube.com/embed/LL9NXDmnFTw




I have a much better video where I replicate several times the problem but it's on the SD card in the car... at the mechanic shop...

[LiqTenExp]

That is very very strange. Do you have the ability to take a data log with HP Tuners? Be interesting to see where some parameters are when this happens.