Pulling my hair out
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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
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At first I though maybe your converter was screwed up, but I don't know how you would'nt see it at other times.
.At first I though maybe your converter was screwed up, but I don't know how you would'nt see it at other times.
I though about this too.. Dunno if he has an alternator or not, but wouldnt that prevent this craziness??
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.
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.
yellow rose
Overnight Sensation
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.
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.
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.
512Stroker
We are all here because we are not all there.
Do you have a data logger?
A video of the voltmeter may tell the story if it is a battery/ground issue.
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.
justinp61
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I do agree with YR that you need better shocks but I don't think when it hooks it's pulling the engine down as much as it sounds in the video. Shocks do go bad, I had one Rancho 9 way and one of the CE 3 ways on the front go bad on my Dart. Instead of spending the money on the same shocks I upgraded to Viking DA's.
Even though the box has been tested I'd still borrow a known good box just to test. I'd be willing to bet that if I sent my Digital 6 back to MSD it would test fine even though something screwy is going on with the rev limiter. Bench testing doesn't match what happens in the car.
What ET's and 60' does this car run?
Even though the box has been tested I'd still borrow a known good box just to test. I'd be willing to bet that if I sent my Digital 6 back to MSD it would test fine even though something screwy is going on with the rev limiter. Bench testing doesn't match what happens in the car.
What ET's and 60' does this car run?
512Stroker
We are all here because we are not all there.
Not discounting any of the other posts I think they are all valid.
That happens so fast I cant imagine that is a fuel issue.
If it were a chassis issue I would think it would unload the tires and spin per the video it looks like the tire plant hard. I dont doubt that the violence of the launch is promoting the problem but the actual cause lies somewhere else.
IMO the speed at which this happens lead me toward a electrical gremlin.
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.
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.
looked@it several times as well, to me it looks like your front end travel is most of the issue, as soon as it hits the front it unloads the back, run it@0.25 speed and then click it on and off and you'll see the hit better, put a limiter on there for just 5" not the masses it has cos the further it has to go up the harder its going to hit under that power and the worse it will unload the tyre....my2c's
If you think you have a launch related electrical issue you could do a bit of an oddball thing...
One at a time on each electrical component, battery too, rotate them 90 degrees to their current orientation (horizontally)
If a battery cell is shorting and the battery is mounted such that the forces at launch cause a plate to move for and aft, rotating it 90 deg should eliminate that movement.
It's a PITA but might pinpoint an issue.
You could do all components that way at once and un rotate one at a time if the problem goes away.
One at a time on each electrical component, battery too, rotate them 90 degrees to their current orientation (horizontally)
If a battery cell is shorting and the battery is mounted such that the forces at launch cause a plate to move for and aft, rotating it 90 deg should eliminate that movement.
It's a PITA but might pinpoint an issue.
You could do all components that way at once and un rotate one at a time if the problem goes away.
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yellow rose
Overnight Sensation
Hey, when I send your stuff back to you I can loan you my known good 667s box. I know it works.
Let me know if you want to try that. I’ll send it out with your stuff today.
famous bob
mopar misfit
how would that cause an engine cut out ??
yellow rose
Overnight Sensation
I say it isn’t cutting out. It’s loading and unloading the tires. At the hit it unloads and almost lifts the tires off the ground. When it unloads the engine speeds up, then when the tires plant again it pull the engine back down until it unloads again.
If it was an engine miss, it wouldn’t miss three times and then hit all the way down. Besides, ignition issues pop and bang. The OP’s engine never misses a beat.
I sent the OP’s stuff back to him yesterday, with a 667s box I have on the shelf that is a known, good box. If he puts my box on and it does the same we know it’s not the ignition because there is little to zero chance that two identical ignition boxes would have the exact same issue.
It will be interesting when he heads to the track the next time.
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.
famous bob
mopar misfit
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 ---??
yellow rose
Overnight Sensation
I’ll go watch it again after a bit. I don’t hear any miss. Or any stutter. I just hear the engine gain and lose RPM very quickly.
You can’t see the rear tires are almost off the track after the first hit? A miss wouldn’t get the tires off the track.
plymouth67
It be a lot cooler if you did...
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...
yellow rose
Overnight Sensation
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.
plymouth67
It be a lot cooler if you did...
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.
yellow rose
Overnight Sensation
Just watched it again at 1/4 speed. When it’s that slow you can see and hear it’s not missing.
Get a $2 buzzer & an old tail lamp/with socket.
[1] Buzzer. Connect one end to grd & the other to the thick red [ + ] wire going to the ign box.
[2] Lamp. Connect one end to grd, other end to the red, switched ign lead, that goes to the ign box.
Have both in the cab with you. If the buzzer stops &/or lamp goes out, you have a problem with supply to the box.
[1] Buzzer. Connect one end to grd & the other to the thick red [ + ] wire going to the ign box.
[2] Lamp. Connect one end to grd, other end to the red, switched ign lead, that goes to the ign box.
Have both in the cab with you. If the buzzer stops &/or lamp goes out, you have a problem with supply to the box.
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