Sudden Power Loss / Hesitation and jerking under WOT
 

I participated in a track day at Thompson over the weekend and I noticed that under nearly full throttle while exiting a corner at a relatively high speed, I would get some stuttering and hesitation then it would pick back up and be fine a few seconds later. If I eased into the gas, the car would accelerate fine. At first, I thought it was traction control because we were in the rain, but I didn't see a slip indication on the dash. Next, I thought I may have been starving the rails of fuel (Was at half a tank) so I topped it off on-site but the problem still persisted. I've read that it's possible on long sweeping lefts, but my issue happened whether I turned left or right, thus eliminating that possibility. The first session of the day was totally fine, however, which is bizarre because I had 3/4 tank of gas.

No CEL .. it just felt like a sudden loss of power and I would get some very sudden jerking, even on the main straight. Like on / off power. Didn't feel like it was misfiring either. Like the car wanted to accelerate but couldn't. I tried to replicate it on the drive home while I was logging but of course, the car was fine. Have these fuel pumps been known to cause problems? I had the HPFP replaced under warranty at around 50k miles, currently have 74k. Car idles and drives perfectly fine. Took it for a spin last night and I could not replicate the problem. New OEM spark plugs were done last year and the coil packs have never given me problems before. It wasn't a hot day either, mid 50's.

I reached out to my tuner for advice as well. I ran a track day at Palmer earlier this year and didn't have a single issue. My guess is something was screwing me up in the rain, but I just wanted to see what you guys have to say.

For the record, I am running a V2 JDL UEL kit with a GTX2860R on a 2013 BRZ.


Thanks,
Jesse

I missed Saturday, stupid wife had an issue and I was half way there Saturday morning.

Thompson holds a ton of water on rain days, especially turn 3. I would bet that something was getting wet in the engine causing a short. First session should have been fairly dry compared to later in the day.
Possible fitting not securely sealing somewhere in the wiring?

You know what, you're absolutely right. The first session of the day was completely dry and the car ran great, I didn't even put 2 and 2 together. I don't recall the hesitation issue I mentioned in the OP. Hmm, I wonder what was getting wet then. I'll have to triple check all my connections. :help:

I remember seeing your car at Palmer, however, I don't think we had a chance to meet. If I see you at another event this year I'll swing by and say hi. :) Thinking about signing up for the June 1st Palmer event.

One thing you can try is di-electric grease in all the connector fittings.
Comes from the all weather motorcycle riders. Much more chance of getting wet.

Displaces any air or water that could get into the connectors.
Keeps the contacts from corroding too.

I should be at Palmer on the first, will try to track you down if you are there. No pun intended

Sounds like fuel starvation. Is the fuel pump up to the task with the extra fuel needs of the turbo?

Fuel starvation sounds like the low hanging fruit here. Is that corner a left hander? If it is you can get a little flab that you put in the fuel pick up from Verus that can help with that.

LINK