Dwell vs rpm?

Tuning, troubleshooting and the nitty gritty of using rusEFI to make your engine run nicely!
Post Reply
mk e
Posts: 547
Joined: Tue Dec 06, 2016 7:32 pm

Dwell vs rpm?

Post by mk e »

Can someone explain why the base dwell table is dwell V rpm table and the dwell v volt is a correction instead of the main and only table? I just can't figure-out what dwell and rpm have to do with each other and how that table is ever anything but the running voltage dwell? It seems like a useless table?
User avatar
mpgmike
Posts: 44
Joined: Thu Aug 15, 2024 2:49 pm
Location: Oklahoma, USA

Re: Dwell vs rpm?

Post by mpgmike »

You may wish to use a less-than-maximum dwell for lower RPMs, which would yield a less-than-maximum spark intensity. Running at max dwell all of the time creates heat in the coil(s), which would shorten their life span. Reserve max dwell for WOT conditions. That's my guess anyways.
'95 Jeep Grand Cherokee, 4.6 Stroker
mk e
Posts: 547
Joined: Tue Dec 06, 2016 7:32 pm

Re: Dwell vs rpm?

Post by mk e »

mpgmike wrote:
Fri Jan 24, 2025 4:07 am
You may wish to use a less-than-maximum dwell for lower RPMs, which would yield a less-than-maximum spark intensity. Running at max dwell all of the time creates heat in the coil(s), which would shorten their life span. Reserve max dwell for WOT conditions. That's my guess anyways.
That makes sense but then it would be dwell v load (map or TPS) berceuse I can have WOT at any rpm. Cylinder pressure peaks at torque peak and that should require the highest voltage spark so maybe that is the idea? Just something I've never run into before.
User avatar
mpgmike
Posts: 44
Joined: Thu Aug 15, 2024 2:49 pm
Location: Oklahoma, USA

Re: Dwell vs rpm?

Post by mpgmike »

It may also be that if you're running 8k RPM there simply isn't sufficient time for the normal dwell before the coil has to fire again. Reducing dwell at extremely high RPMs would allow the coil to do it's job, recover, and be ready for the next pulse. These are mere guesses, as I always bench test the coil for best dwell at a few voltage levels and run with my numbers -- at any RPM/load.
'95 Jeep Grand Cherokee, 4.6 Stroker
Post Reply