How is the battery mounted? Are the plates shorting out on launch?
The coil is mounted on its side on the passenger side inner fender. Not sure if that would cause a problem, but it has been mounted there for many years. @yellow rose tested it along with all the other ignition parts without finding any problems.Is the coil an oil filled style?? If so, maybe some internal slosh.... I've seen them fry and work intermittently so the launch could make sense. I would switch that out to an iron stack first.... It's torture watching that video.
At first I though maybe your converter was screwed up, but I don't know how you would'nt see it at other times.
Do you have a data logger?The fuel tank is a 4 gallon cell under the hood that gravity feeds to a belt drive gear pump.
The Optima Yellow battery is in a box in the trunk held down with two 3/8 studs so it’s solid. Goes to a 4 post master switch that the alternator is also wired to.
The tranny was built in 2017, Coan 8” spragless converter, Coan pro-brake valve body. I change the fluid at the beginning of each season, and haven’t seen anything strange in the fluid. I considered the trans brake trying to reactivate until it also happened off the foot brake.
Plugs are gapped at .030 as they have been for the past 4 seasons I’ve been using the injection system with methanol. Other than freshening up the motor nearly everything is the same as it’s been since 2017. I was having some issue last year with the shift box. As soon as I’d launch it would shift to second gear. Totally unhooked the box thinking maybe it was shorting out, but it didn’t change the sputtering problem.
My next thought was maybe it’s something in the barrel valve on the injection. However I don’t understand why it would happen only on the track, and only at the starting line. Throttle response and fuel mixture is fine the rest of the time. I use a wideband gauge to monitor the air/fuel.
I do not. I’ll have to try it again, and watch the volt meter when I launch. Unfortunately there isn’t another race for a couple weeks, and it’s 250 mile away. Don’t think I want to drag my car all the way there just to fight it all weekend.Do you have a data logger?
A video of the voltmeter may tell the story if it is a battery/ground issue.
Not discounting any of the other posts I think they are all valid.I do not. I’ll have to try it again, and watch the volt meter when I launch. Unfortunately there isn’t another race for a couple weeks, and it’s 250 mile away. Don’t think I want to drag my car all the way there just to fight it all weekend.
I don’t know anyone who runs a Mallory box. I’d have to switch everything out to MSD stuff which would take a bit. I’ve poured over the wiring the past week other than the wires that go up into the column.I think its Power Lose....... trans brake????? Remove the power to the relay that activates it. could be the g forces messing with a weak relay contact.
Like the battery plate idea.
Ign tested.........But not under launch conditions.......do you know any racer buddy that would let you swap boxes for a run?????
I just can't see it as a traction issue. if the tire slipped and then grabbed. the exh not would go up and then back down. The exhaust is going a way and then comes back.
GROUNDS are the last thing to be looked at and can cause all kinds of problems. At least remove the ground and power wire from the battery and clean them. Even if they don't look dirty. What you got to loose.... and its free.
When the exhaust note goes away the nose drops and then jacks back up.
I don’t know anyone who runs a Mallory box. I’d have to switch everything out to MSD stuff which would take a bit. I’ve poured over the wiring the past week other than the wires that go up into the column.
I’ve watched the video now so much the wife has banned me from doing it again (a OT that I listen to her).
If you slow the video down to 1/4 speed and watch the front end, you’ll see it never drops. If it had a miss that bad, power would be down and the front end would take a nose dive.
Instead, it looks to me like the front is still on the travel limiters. And the back looks like it’s almost lifting the tires off the ground. That can’t be electrical or fuel.
IMO, the reason it doesn’t happen on the return road or the driveway is because it’s not a prepped surface and it doesn’t have the bite there like it does on the starting line.
That’s what I’m seeing.
how would that cause an engine cut out ??
sounds like a stutter box a little . why would unloading the tires cause an engine to cut out ? I have had the old hemi car unload the tires before we got it sorted out years ago , and it didnt cut out ---??The same reason I ask about the transmission brake. And to check if it’s scorching fluid. It acts like a pro car bumping in on the transmission brake, but instead it’s doing it at the launch. If it’s a mechanical or electrical issue causing it to activate after launch, disaster is imminent.
sounds like a stutter box a little . why would unloading the tires cause an engine to cut out ? I have had the old hemi car unload the tires before we got it sorted out years ago , and it didnt cut out ---??
I kind of wonder if the rev limiter is shutting it down...it almost seems to me you may be getting a little wheel spin and the limiter shuts it down. Once the car gets rolling the wheel spin goes away and the rpm's drop a bit so, it clears up. Have you tried launching it at a lower rpm? Like YR said it almost picks the rear end off the ground and that would cause some wheel spin really fast and, since it comes back real quick it gets traction and, drops rpm slightly. It would be interesting to know what your limiter is set at and, how close your are to that number when it launches. Just my 2 cents...could be way off. Hell, could be your dishwashing detergent...
I just wonder if it's unloading and rebounding so fast that it doesn't have time to studder on the chip like it normally would.It’s possible when it unloads the tires it’s getting enough RPM to make it hit the chip. If it is hitting the chip my deaf ears can’t hear it.
I know the Rev limiter works like it should. After I did the video I checked it at several other RPM and it was spot on.