DMK

iTrader: (6)

I went to Streets of Willow this weekend and the course has a couple tight turns that I do 4->3->2 downshifts on really quickly. Sometimes when downshifting, my side foot(heel-toe) would miss the throttle pedal to rev-match and I would get a jerky engagements followed by some wheel lock for a second. I went and did my first 5 sessions fine. Each was followed by at least a 20-min cooldown. On my sixth session, my second lap after downshifting from 4->3->2 on turn 2 I would hit the accelerator and the car would not go. I could hear the engine bogging down and it would not let me rev at all. No dash lights came on at all. I put it into neutral and let it coast to the next turn, shifted back into a higher gear at it was fine. It would rev through all the gears again without trouble. Two more laps into it, I missed the throttle while downshifting and when hammering the accelerator after the turn, it would not go again. After the second time, I just brought the car into the pits. If I let it into neutral for about 10-20 second and then put it in gear again, the engine would sound fine and would shift fine. I'm not sure, but I was thinking the tranny overheated from too much downshifting while not rev matching. I did get a bit of wheel lock each time I downshifted too fast while not rev matching. Or was it something else? I posted here because I think someone else with track experience might have had the same thing happen to them.

Btw, car drove home fine.

Engine/Drivetrain Mods:
Non-Revup '04 6MT
Vortech with stock pulley and fuel system.
Split Second Piggy Back
Stillen Oil Cooler
Redline tranny/diff fluids changed 10k miles ago with no track days in between.

dmoffitt

iTrader: (4)

fuel starvation?

Dave 90TT

iTrader: (4)

Well, I had clutch issues at the track before I put in a stainless steel clutch line, but I don't think thats your problem. I would be leaning towards fuel starvation. as well.

How full was your tank? I know that if I have less than 3/8's of a tank left, I get fuel starvation in the corners. I always keep it above half a tank at the track.

Dave

Billhyco

iTrader: (14)

i know I am going to pay for this one day but i am pretty harsh on my tranny at track events. the heat through the floor alone will about cook my feet. but i have never had this issue. Granted I don't know the track you are on but the main track I run is VIR and it has a lot of straights which I am sure gives the trans atleast a little time to cool off. I don't think the trans is your issue, but if you're unsure, put a cooler on it. I would lean more towards fuel as mentioned above. Talk to your tuner and see what he thinks, maybe he can re-map it for you or even give you a few different to work with throughout the day. 10-20 seconds, however, seems like a long time for the fuel to "catch back up". Ya sure you just didn't have VDC on and the "slip" light bulb is out??? Ya never know I guess. Good luck with it and let us know what you find works.

Stack

Curious... what is the "Split Second Piggy Back" in your sig? Does that have anything to do with the tranny?

Have you tried not rowing through the gears on down shifting? especially the 5th-2nd (no chance of a money shift unless you let the clutch out too early).

Dave 90TT

iTrader: (4)

It's an ECU piggyback controller. Controllers timing, and fuel. Nothing to do with transmission.

Stack

Well... as was hinted at before... maybe its a fuel issue. Simplest first: unplug that and see if it makes a difference.

Would be best if we had some video

betamotorsports

iTrader: (1)

The drive-by-wire throttle software int he 350Z sometimes hiccups if the gas and brake are applied at the same time. Its more pronounced for those people that left foot brake and use the throttle at the same time to balance the car. It might also happen on a sloppy heel-toe downshift.

DMK

iTrader: (6)

I had more than 3/8 tank left and I was running a 50/50 mix of 91 and 100. The split second is something I need with the supercharger or else, BOOM goes my engine.

There were times where I did hit the brake and gas at the same time on accident when down shifting, so I could feel my car lurching forward as I engaged the clutch. No dash lights came on at all, that's the first place I looked when this happened.

When the engine bogged, I'm not sure how much time it took to get back to operating condition, but I just coasted into the next turn and then shifted to a higher gear and it worked fine.

It might be fuel starvation, because the Vortech supplied aux. fuel pump and FMU aren't all that great/reliable. I was planning on switching them out to a Walboro later on anyways.

racerbob4

iTrader: (8)

We get fuel starvation when we are about the 1/4 tank mark. This only happens on road courses.

DMK

iTrader: (6)

Are those the symptoms of fuel starvation? What are the symptoms of transmission overheating?

racerbob4

iTrader: (8)

Usually you can smell a transmission or rear end when they get hot. We use Red Line Oil products in our Z from the front to the rear. You can call Red Line and talk to Kelly or one of their technicians and get their recommendations. Good pople to do business with. At one time we had power steering pump problems and they solved those more than a year ago.
I keep getting the idea that this might be something going on in the computer.

mhoward1

reading it, It sounds like an ECU issue to me as well. Did you have TCS turned off? If not, they system could have become quite confused with the wheel lock up, then full throttle applications. The Piggy back could have amplified the issue with a system delay between it and the sensors.

mpowers

iTrader: (7)

+1

dmoffitt

iTrader: (4)

I've run into what you are describing DMK - but I always blamed it on Technosquare's tune (didn't do it before that but I can't conclusively say so because we also put on a 350evo TB at the same time). The one thing I WOULD confidently say is it's unlikely that it's the transmission.

+1 on Bob's comment re: redline though, they make an excellent product, I've run it in every one of my vehicle's transmissions / transaxles.

DMK

iTrader: (6)

I had VDC(Traction Control) turned off the entire time. Your response is interesting because I also forgot to mention, that I have a Technosquare L-Spec reflash. It is their limited reflash where they raise the rev limiter, remove top speed limiter and open the throttle to 100% at WOT. It doesn't mess with the A/F at all, the split second does that.

Btw, what are the symptoms of fuel starvation? Bogging engine as well?

Kolia

iTrader: (2)

+1. Unless the Yaw sensor is disconnected, or the power to the ABS/VDC is cut, you are not the one braking the car. Braking on a race track = emergency stop for the car = Brake Assist, regardless of TCS/VDC switch status.

If you mess up, the system might stay ON longer than usual. If it does, the throttle will be partially closed by the ECU.

That is on a stock car. Who knows what happens on a moded ECU?

Ah and don't row though the gears. 5th to 2nd with a good double clutch rev match is preferable.

dmoffitt

iTrader: (4)

hm, that's interesting - so it's like Porsche's PSM "emergency! turn-myself-back-on" BS?

Kolia

iTrader: (2)

Yeah.

I didn't believe it until I unplugged the Yaw sensor and suddenly had to steer the car while braking from high speed. You'll also be able to trailbrake into a turn. Something that's almost impossible as the ABS usually kicks in on steering input.

From talking with the chassis dynamic engineers at work, that is standard behavior on pretty much all VDC and Brake Assist equiped cars.