Dumb Q,,
Is the intial timing setting supposed to be set to what the mechanical setting of the distrubutor is set at. I.E. mechcanical set to 6 software set at 6??

Chuck :flag

 

As far as I am aware, this is correct.

The initial timing programmed in the chip should match the mechanical initial timing. 6 degrees is the stock setting for L98's.

I run 12 initial, with 12 also programmed in the chip, (for idle reasons). This value is used in the code as a reference for advance and is considered in the spark advance calculation to determine how much electronic advance to add to produce the desired total advance.

By adding more initial mechanical advance than what is programmed, you can "trick" the ecm to add more advance, if that is desired.

 

Ok I guess I screwed up something fierce. I had mech set at 6 and initilal programmed to 16.5, with a max at 38. So that would only net me 28 total, correct? If that is true than I guess 300rwhp is not bad for timing be messed up.

Chuck

 

I would fix it and then make sure you do some part-throttle runs (stepping up in throttle to a WOT run) to check for any knock or too much timing in some spots.

I know with my superram install, the timing maps were off enough (I'm still wondering why) to induce knock in several locations... but that will happen with a radical change in intake/cam anyway I suppose.

The short of it is just don't assume that by fixing the timing discrepancy that there won't be any side effects (ie detonation in some areas).



EDIT - I also have 42 degrees as MAX timing, but this will be remarkably reduced under higher load / RPM scenarios... again, do plenty of part-throttle runs with datamaster to keep things happy, but the 42 degrees will be fine in medium LV8's and RPMs (in my limited experience).

 

While we're on the subject, if the actual timing were advanced a few degree's or retarded for that fact) and the chip still set at 6, what would this do to your idle.

After I had some work done on mine involvong distributor removal, my idel is a little rough, as soon as I touch the gas pedal it smooths right out.

My scan tool shows total timing over 43 degree's at cruise, seems higher than it used to be.

TIA

Mark

 

ttt

 

advancing base timing will speed up the idle and retarding it will decrease the idle. Also, in your chip the timing tables are based off of the value that is entered for base timing. With a mail order chip my timing at part throttle would be as high as 47 degrees, which made it miserable to drive. I went down to 38 which really helped drivability

 

Thanks! I need to have mine checked then because when I was resetting my IAC it would not idle whithout my foot on the throttle, even after it was at operating temp.

I have not touched my timing tables yet, but it idled prefectly before I had this work done, so I suspect they did not get it set correctly i.e. it is retarded a bit.

 

Did you adjust the throttle plates when resetting the IAC? With the IAC unplugged you want to set a base idle by adjusting the throttle plate stop and THEN plug the IAC back in. So I think you should still get it to idle (abeit not at the RPM you want, necessarily) with the IAC unplugged unless your timing is completely out of whack (unlikely if it drives well, but I don't know what your mechanic has done).

Also, a quick check with the timing light (borrow one from autozone or something) might save you some trouble.

 

Update. I did not touch my idle screw, still has the cover on it. What I did today was add 4 degree's to the table for 400 and 800 RPM across the LV8 axis. This did not help the rough idle and my scan tool indicaed more total timing than I should have vs the stock timing table. I then went back to stock spark advance in the table and set my initial timing to 4 degrees as opposed to the stock 6, this did nothing to help my idle and again showed more total timing than I should have for the stock table settings. Lastly I set my initial timing to 7 degrees, this helped smooth out my idle and my scan tool indicated total timing to be in line with the table. It appears my distributor is mechanically set at or around 7 degrees as opposed to 6 as it should be stock, not surprising after all the other things I had wrong after the intake gasket was repaced at a shop.

I will say that other than the rough idle (jumping between 650 and 750 RPM instead of steady at 575-600) the car really took off once I got into the throttle, attributable to the extra mechanical advance I had and not programmed as such. RPMs now build a little more slowly at part throttle than before but very smoothly as one would expect for stock timing. Next I will try 8 degees initial timing to see if there is any more to gain at idle, then go back and start working on the table from about 1800 RPM and up.

BTW, thanks Jesse for the tip on idle BLM's, that is the one area where I am still rich, I'll be going there after I get my timing done.

 

For explanations sake.....

If your base timing is set to 6* and in the chip it is 8* then you will have 2* less across the whole board.

 

Yep, and in my case base timing is set at 7 or 8 and my chip was set to 6, I had 1 to 2 degrees more across the board. What's amazing to me is how just that little bit can affect idle and light load RPM quality.