I am having issues at the track my car is breaking up in the mid rpm range, only seems to be breaking up at the track ,i guess it's loaded more than the street......it leaves the line pretty good but as soon as I get around 4,000 rpms it starts breaking up, if I keep in the throttle it will clear up around 5,000 or so rpms, as soon as I shift it drops down to 4,800rpms and breaks up again and will clear once it gets up in the rpms again....my tune up is fine and is running around 11.0-11.5 af.....I have a fast xfi running the tfi distributor ...seems like an ignition problem but not sure , plugs are gapped at 20....any help would be great thanks

 

Are you running an ignition box?

 

yes I am running a 6al

 

anyone?

 

Somethings to try:

Reduce the gap on the spark plugs by .010. It may be possible that at max torque (3500-5000 rpm) you have more cylinder pressure then the MSD 6 box and coil can fire through reliably. If reducing the gap helps, you may want to upgrade to a 7 box for a hotter spark.

If it doesn't help you may want to try (borrow) a different MSD box, I have had a few do "funky" things over the years.

Check to be sure your MSD pick-up wire and the wires to the coil are not routed in the same area or are at least separated from each other to avoid false triggering from EMI

Scott

 

+1 on the msd box, we see those things go bad in the shop all the time, but definatley verify by tightning the gap to see if it improves!

 

I went down from 30 -20 last week and it was the same, I will definatly try a 7al I have one laying here......i may try a distributor also ....hoping for somthing simple

 

Just had one in the shop today that was breaking up at very low load and from 3000 rpm up and would not make a wide open throttle pull past 3500, it had a brand spankin new mallory dist and coil! Had the custumer bring his stock dist up, installed it and fixed the low load ignition problem but still would not pull clean in wot so we put a stock coil back on plug gap was .020 and it pulled perfectley to 6300. Gota love some brand new broke junk!

 

What is the rest of the tune?
Timing?
Fuel?
Intercooler?
How is the box wired?

 

the tune up hasn't changed from before when it was running fine, liquid intercooler, the box is wired directly from the battery for ground and power, and powers up with key ...according to my data log the af seems right around 11-11.5.........i swapped the distributer and am going to the track tomorrow night.... i am taking extra everything to try and resolve any issues hopfully.....will let you guys know thanks Sonny

 

What kind of fuel?

 

c16/110 mix