Anyone played with Spark dwell times?

[jfpilla]

Jesse,
While on the subject of spark dwell.
Have you compared the LS7 vs LS1 'spark dwell time" tables? The LS7 values are lower and so far no one knows why. I have an LS7 crate in my 2003 C5 and am using the LS7 tables. Do you know if that's the right thing to do? It runs fine. No apparent negative results, so far.
Joe

[SSpdDmon]

Jesse,
While on the subject of spark dwell.
Have you compared the LS7 vs LS1 'spark dwell time" tables? The LS7 values are lower and so far no one knows why. I have an LS7 crate in my 2003 C5 and am using the LS7 tables. Do you know if that's the right thing to do? It runs fine. No apparent negative results, so far.
Joe

Are the coil packs different (LS1 vs. LS7)??

[wait4me]

Every coil is just like a fuel injector, they all need different things to make them right just like an injector.

[jfpilla]

Every coil is just like a fuel injector, they all need different things to make them right just like an injector.

We are all guessing that's the case and hopefully is the reason. What would you look for regarding results. Plug color, backfires, missing at WOT, etc? Or, is there a known voltage to measure?
Joe

[jfpilla]

Are the coil packs different (LS1 vs. LS7)??

Yes, but how they differ is a question.

[joecar]

My point is though, that with the stock dwell settings, they are set up expecting a 700ish ohm resistance, so they dont dump the reserve voltage as fast. With a wire that has 125 ohms, the voltage gets cleared out faster from the coil so it has to take longer to fill that lost voltage back in. Hence why it starves on the top end of the rpms and has stronger on the low rpms range.

Ah, I get it. :lightbulb:

[wait4me]

Increasing the power output of the coil just allows you to open the gap more on the plug. Same kind of example when you go with an aftermarket msd ignition on the older gm stuff. It wont show a difference unless you raise the plug gap. The larger the spark the more the power due to better fuel ignition.

[oztracktuning]

My engine is experiencing spark blow out at higher boost levels. The solution thats common is to decrease the gaps. can i increase the dwell values at high rpm and solve the problem an alternative way?? Its an E38 ,using TR6 gapped near 0.9mm (0.035")

[neil]

Hi Steve,
I don't know whether increasing the dwell would help your problem.
I would have thought that you would need to increase the current and if required the dwell rather that increase just the dwell. If the spark is blown out I think you would need to increase the strength of the spark (ie. current) to overcome the problem. To me decreasing the gap would cause other problems.
Just my 2 cents.

Neil.

[oztracktuning]

Thanks Neil for the input. Gapping the plugs smaller is the common thing that people need to do when increasing boost. Mine are gapped at 0.8mm now but its common for them to be 0.65mm, this is with GenIII/IV and also lots of Turbo imports. The question is if the dwell is near the lower limits of coil function which i am told it is. If so more dwell is supposed to be able to help, its already optimal as you have said it wont.