spark dwell...can somebody give heavy details

[WS6FirebirdTA00]

Let me see what exactly is going on with the dyno this Sunday. I may have to get an hour of time on there to screw with, thats $100. I may make 3 pulls and just put this in there and see if he will let me make one change, and just change that. Anyone who REALLY wants to see this and wants to throw in a few bucks just let me know

Then once I have a baseline for what is in the car now, I will go to a dynapack at a local guys shop and see what he can do for me if I spend some time on there. I may try to play with it and if gains show, I will mess with it until I get a table in there that works out well. Plus by then I should have some money haha

[MeentSS02]

I told you to send me a PM mofo

[WS6FirebirdTA00]

Just seeing if there are any more offers lol

[Main_One]

Hey, I've been silently reading this thread curious about this too. Please post your results when you get them, and who knows, I might even throw some paypal your way too!!!

I just last night noticed something strange in my spark dwell Mult Min table, which currently is the same as stock for my 03 5.3L truck engine. The table basically gives a multiplier for increasing RPM values, but it goes like this:

.1, 1.02, .1, 1.02, .1, etc.

This seems very strange to me. Anybody know why GM has it set this way??? I've downloaded a custom tune from a buddy's truck, and the shop that did his changed all of these values to 0.9 .

[WS6FirebirdTA00]

post up your file so we can take a look, I dont have one on hand. The most difference I have seen so far with these settings are seems to be down low/mid range, mainly in the peak torque area. The dyno will not be at the track this weekend but I am going to try and get on one shortly.

[Main_One]

Here it is. First is my file, second is friend's from a custom tune shop.

[Rammer]

My 05 5.3 stock tune uses .9 across the board in the spark dwell Mult Min table .

[Main_One]

Thanks Rammer!

[Main_One]

I recently purchased the book "How to Build High-Performance Chevy LS1/LS6 V-8s" by Will Handzel, Program Manager at GM Performance Parts division. Here is a quote from the book that applies to the topic of this thread:

"The factory coils have about a 60 mJ spark, which can knock you on your can if you get the full blast - so these coils are good for big power. In fact, stock coils have been known to handle over 1000-hp turbo apllications with no problem. They've gotten a bum rap from the blower and turbo crowd as many claim the coils struggle to handle high-RPM, big-number power. Actually, the problem is not with the coils, but with SPARK DWELL timing.

On boosted engines, the dwell needs to be lengthened at higher RPM but kept near stock levels at low RPM to avoid overheating the coils.

As a tip, the truck coils have slightly larger heat sinks, so many Gen III enthusiasts believe they are better suited for high-horsepower, higher-heat applications."

Looks to me the dwell times should be kept close to stock at RPM levels seen under normal cruising conditions, and should be bumped up for RPM levels above that.

[WS6FirebirdTA00]

Great find! This is what I was wondering. I think I will rework my tables to stay stock down low and ramp up right before peak torque.

[MeentSS02]

Damn...and I even have that book

[MNR-0]

Another thing you might consider is keeping your dwell stock and using the dwell multiplier vs. MAP to ramp it up to max. multiplier by 95kPa. This simulates load based increases in dwell while leaving light throttle stuff unaffected.

So you might begin ramping from 1.0 at 75kPa to 1.3 by 95kPa. If your base dwell is 5, then it will be 6.5 by 95kPa.

[MeentSS02]

I wish I knew how much damage I am doing to my coils right now...I've ramped mine up 2 ms from stock across the board, and I love the response it has had to that change. But if I'm gonna have to replace my coils in a few thousand miles, that might not be the best...oh well. Guess I'll be the guinea pig on this one...

I also use the MAP multiplier...

[hirdlej]

I wish I knew how much damage I am doing to my coils right now...I've ramped mine up 2 ms from stock across the board, and I love the response it has had to that change. But if I'm gonna have to replace my coils in a few thousand miles, that might not be the best...oh well. Guess I'll be the guinea pig on this one...

I also use the MAP multiplier...

I will join you. Send me your current HPT file and I'll copy and paste all your dwell settings exactly to mine. We can be twin pigs on this one. I'm not afraid

[MeentSS02]

I'll try and get it up here tonight...

[Main_One]

I wonder if the MSD coils can take more dwell time???

[WS6FirebirdTA00]

might, MSD could prob tell

[pwrtripls1]

good thing I have a truck. LOL I will up mine 2-2.5 across the board. Mine is still under warranty for quite some time. hehehe

Plus if the issue is overheating the coils, just run it around town hard and every once in awhile just pop the hood and feel them.

[pwrtripls1]

I added 2.2 to the table on everything below 6. Its freaking awsome!!!!!!!! I can spin my tires off the line now for a few feet. I never could do that before. Also I'm running between 33-35* timing with NO KR at all. Its alot better at part throttle and WOT is better as well. I guess we'll see if my coils have any issues, but I'm not changing it back.

[speedy]

Humm, I haven't never messed with spark dwell before... Maybe i should give it a try..