Good morning, I've been tuning with the sert.and reading threads. Everybody seems to be dancing around the timing issue. with also complaints about clatter/chatter in the 07"s first, I've been building stroker chev smallblocks timing has always been an issue. should be a certain relation to bike motors. longer rod longer dwell time at tdc and bdc hence better cylinder filling. stroke increases piston speed also builds torque at lower rpm's seems some of this info should relate to the 96's I know they didn't change rod length but moving on you get the idea. I'm pretty sure the moco had to put cams with less duration and overlap for epa which of course raises cylinder pressure at lower rpm which would less spark lead because of octane requirement. To run clean/lean they went 14.6 AFR and it appears that the timing really ramps up in the lower rpms and maps I've been comparing the cal maps in the cert looking at the spark tables and there appears to always be up to a 10 degree increase between 30 kpa and 70 pa the spikes being focused from 40kpa and 60kpa from 2000rpm to 2500rpm advance drops off at 70 and 80kpa as the rpm increases. I'm going to start dropping adv in the 40 to 60kpa between 2000 and 2500rpm range. i've already took out 2 degrees with a certain amount of success. any thoughts anybody?

 

Dave
You are correct in your theory with the stroker motors...the timing should be a bit different from a shorter stroke motor. The motor co makes the timing tables for their bikes with efficiency and good power in mind with what they have to work with, meaning the cams and EPA regulations. The timing is then softened a little to assure no damage will happen to the bike if it happens to be a very humid day or the chance you might get a batch of bad fuel. In most cases I see by advancing the timing (with the stock cams and heads) I gain a bit of power. (I haven't done this in a 07 so it could be totally different situation)
The biggest problem Isee with the96' motor is the customer expects all this torque because it is a stroker....in reality the headsare restrictive and the cambarely has lobes on it...the engine doesn't breathe.The EPA regulations have to be met and this is done by restricting the air flow through the motor....less air equals less emissions.
We can unleash awesome power from these motors with some head work, cams, pipes, air intake,and a bit more compression....(plus a good tune).Once you have this work done thenyou can and will see more power made be changing the timing tables up or down but a stock motor won't benifit enough to go through all the hassel.
To do the timing tables a Dyno Jet is needed to see the subtle changes that are gained.ie something has to tell you if your gaining or loosing with your timing change and how far to go...the Dyno is the only way to see these gains or losses.Even with the Dyno it is extremely hard to adjust timing inevery throttle position and rpm....most tuners will do 100%TP runs and see the gains in the tq or hp and call it a day. If you want to do the complete timing table you will need the Torque Link program from Dyno Jet, this program and hardware run about $2500.00...so don't expect to see this added to your nearest dealers Dyno...lol. This program allows the tuner to measure how much resistance the eddy brake is giving to hold the bike at a certain TP and RPM range. Example; if your testing 20% TP at 3000 RPM you canrecorda run then change the timing in that grid, make another run and see if it took more resistance to hold the bike or less resistance to hold it there. If you had more resistance then you gained power with your change...if you got less then you went back wards .This process will takeyou a LONG time to do but thats how it has to be done to be accurate.
To feelgains in power, or losses in power,in the seat of your pants you would have to gain or lose 10%. Most gains inpower by timing alterations are much smaller than these and that's why you have to have a dyno to see them, without the Dyno you're just guessing.
Cams, pipes, and types of fuelsmake a big difference in the ignition timing.When you see big jumps in the timing tables even with a stock motor it could be exhaust flow or the cam coming on or fuel delivery, remember the Harley motor has a strange timing to it anyway, the front fires at 405 degrees and the rear fires at 315 degrees so this isn't like any Chevy that you played with.....lol.

Hope this helps
Doc

 

Well put doc!..........do you by chance know if the tuning link from dyno does anything to the ign??

 

Yes the Tuning Link PCIII usb software can change the timing but not automatic like it does the fuel unfortunely. You have to have the Torque Link program even then it's all manual effort as far as I know.