We tried to do some TnT this weekend and ran into a new issue for us.

Our TD engine won't run over about 5000 RPM!

Stumbles in the burnout. Idles fine and comes up on the converter OK, but when you launch, the RPM's flash right up to just about 5000 RPM and won't climb any higher? Just stays right around that RPM and makes like a bus going down the track until you click it off.

None of the rev limiter settings in the grid setup are anywhere 5000 RPM, except Launch Limiter is set at 4500 RPM.

Outside of the plugs looking like crap, the rest of the engine seems to be fine [running battery voltage, engine pressures and temperatures, valve lash, springs, leak down, etc.

Any ideas out there?

If you send me the Data Acquisition of the attempted run I will give you my opinion.

Without the DA I wouldn’t even want to make a guess.

PM me if you decide.

I'd say likely suspect is the pickup or rotor phase but certainly could be a multitude of other items.

Does it sound like its on the Chip from the ignition? Or is it just laboring at 5000 RPM?

I will bet the farm that it is rotor phasing. Depending on how much if any you are retarding it, double check the phasing. If you are retarding it more than 3 set it in the middle of the lug, if not, set it toward the front of the lug, but not at the very front.

quote:

Originally posted by DragRaceResults:
I'd say likely suspect is the pickup or rotor phase .

We checked that, but thanks...

Safety run time ?

quote:

Originally posted by DaleH:
Does it sound like it's on the Chip from the ignition? Or is it just laboring at 5000 RPM?

Wouldn't RPM in the burnout, usually gets right up to 6500-7000 RPM. Came right up on the converter, as normal.
At the launch, the converter flashes right on up to 5050 RPM at 0.2 seconds, slowly drops to 4550 by 1.1 seconds and then pulls slowly back up to 5080 at 3.0 seconds, and runs around there until around four seconds when the driver lifted. Never got above 5200 RPM.

quote:

Originally posted by 68TSCAMARO:
Safety run time ?

SRT: 9.0
SRV: 2000
ST RPM: 6000

Thanks to Mark Nettesheim for all of his help and advice. Still no solution:

UPDATE

We are running a NHRA LODRS Top Dragster with a 548ci BRODIX aluminum Big Duke BBC with a 400HP Nitrous system. We usually run in the low 6.6 second range at 205+/- MPH. We have a MSD POWER GRID 7720/7730 #13491 [replaced 4/2019] with 8261 coil [9/2019]; 8276 Non-Magnetic Pickup [Replaced 9/2019]; Cap 8408 [9/2019]; Rotor 8457 [9/2019] and MSD wires. This combination has been running with no problems.

When we took off the body and visually inspected everything. The only thing we found was the MSD Fiber Optic Inductive [PN 7555] cable, was not connected to the MSD 7730 box.

We ran the following MSD Tests: [MSD Digital Ignition Tester: PN 8998]
1. Checked MSD for “Alerts” NONE
2. Downloaded and saved current configuration.
3. Updated Data Acquisition Options:
Launch Input, Gear, Shift Light, Output Switch, Ignition IN, Ignition Out, Rev Limit Active, Rev Limit RPM and Battery Voltage.
4. Saved and downloaded new above configuration for testing.
5. TESTS:
a. Ran up RPM from 0 to 8500+ to determine if any problems.
1. Shifted at 8000 RPM.
2. Rev limiter cut off ignition at 8500 RPM.
b. Engaged transbrake and ran up RPM from 0 to 4500+ to determine if any problems with launch rev limiter setting. None!
c. Engaged burnout switch and run up RPM from 0 to 7000+ to determine if any burnout settings problems. None!
d. Verify 150 engine start timing retard:
1. Set tester to 200-300 RPM and check Racepak timing. [210]
2. Set tester to 600+ RPM and check Racepak timing. [360]
6. Downloaded multiple run files for ReView software application.
7. Checked hardware:
a. Rotor/cap phasing.
b. Inside cap and rotor for any abnormalities. Cracks, soot, hits, etc.
c. Wiring to coil.
d. Plug wires: Ohms, melts, breaks, etc.
8. Crank trigger:
a. Gap: around 0.065”.
b. Ohms on wires: 72 ohms.

All of the MSD *.dqi files looked normal!

not saying this is your issue, but i chased fuel, ignition and then found out it was a broke a-- converter. anything funny going on with the trans temperature?

Joe

Even though the engine would not rev up much more than 5K, it went right up on the converter to 3850 RPM without a problem and launched well initially. At around 5K RPM, the revs flattened right out and would not climb much more.

Trans temp was normal and we had just replaced the ATF.

quote:

Originally posted by David Gerard:
Even though the engine would not rev up much more than 5K, it went right up on the converter to 3850 RPM without a problem and launched well initially. At around 5K RPM, the revs flattened right out and would not climb much more.

Trans temp was normal and we had just replaced the ATF.

I'll bet it's a active stator torque converter, correct?

Spun the stator tube or broke the spag - mech diode (one way clutch).

been fighting an issue last couple weeks with mine missing lightly under serious load. Checked wiring, changed crank trigger, coil, cap and rotor didnt fix it. Put a new 7720/7730 in the car and straightened right up. My plugs were looking like **** until I changed plugs. In all fairness, the boxes were from 2014, were in 2 different cars, and seen a 12 volt to 16 volt change 3 years ago.

quote:

Originally posted by 329L:
been fighting an issue last couple weeks with mine missing lightly under serious load.

What’s serious load ?

When the converter grabs the engine after the launch, top of gear change if im on the bottle, and the last 100' of track.

quote:

Originally posted by 329L:
When the converter grabs the engine after the launch, top of gear change if im on the bottle, and the last 100' of track.

Curious, about how much HP NA and how much nitrous ?

Look at the ignition in Grid data acquisition file. This will give you insight if the crank trigger is working correctly.

I didn't have enough channels enabled when we ran the TnT, but in the static tests at home all of the dqi files looked "normal". We were using the MSD test box so no crank trigger. It did OHM out right in the middle of the MSD range [72 OHMs] and the gap was correct.

Is the engine limited to 5000 with trans in park or neutral?