F8L Z71

I want to add timing at WOT and I am not sure how much timing I should add througout the rpm band.

On the timing "High octane spark vs load" There is an axis for load in grams per/cyl and a horizontal axis for RPM. On my chart at 3000RPM my timing is at 28deg then from 3800-5000 it dips to as little as 23deg then right back imediately to 28deg and stays there for the rest of the time till 8krpm.

My question is can I just use the fill function and make all the cells from 4000rpm to 7200rpm with 30deg? I'm sure I have to add fuel accordingly. I read that most people can get away with 30degs of timing but I am not sure what RPM they are adding it at and what load value. Anyone have any ideas?

99 WS6

I would not fill-in the values to be the same. I am no expert, but I think that the dip in timing is to prevent detonation. The peak cylinder pressure occurs at peak torque, so to help prevent detonation, the timing is reduced. Again, I am only repeating what I heard, but it sounds right to me.

Reckless

iTrader: (9)

FWIW, my tables (both Hi and Lo octane) show 31 degrees from about 3500rpm on up. Dynoed several times yesterday on 92 octane with no KR problems at all.

Mr Cowl Hood

Typically, you want to set timing values from ~4000-5000 a few degrees lower on most cam setups in the higher MAP areas during WOT.

That is where most make peak torque and you'll get more torque if you tune to that. You can get away with setting the whole WOT section to 31* if you like, and not get knock, but you may be leaving some torque on the table. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Don't be worried about adding so much fuel to make up for the added timing. GM did that already for you! <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

Reckless

iTrader: (9)

Interesting. I noticed the lower values in the stock programming in that area. Why will it make more torque with less timing?
Todd

really slow truck

sorry for the newbie question, but when you guys talk about modifying the timing, which gm/cyl loads are you talking about modifying?

F8L Z71

I was also told not to add too much timing if any at all where my TQ and HP curve crosses, which if you look on the tables thats where we have the least amount of timing. I think I am going to try to add timing in the 5600-7000 range by maybe 2* and see how that works then slowly add timing in the 4000-5400range while on the dyno and see if that helps or hurts, if it hurts I will try lowering it and see what that does and I'll post results.

I am chaning to a bigger cam on Sunday so I'll be dyno'ing next week or so.

Reallyslowtruck, I think some people are doing it from .60 gm/cyl-1.2gm/cyl since that is the area where your factory set timing starts to lower from your cruise timing or 35+* and stays steady at or near 28*. If that made any sense. LOL

really slow truck

yeah, it was understandable, thanks for the reply.

bryan

G ForceSS

The only spots you have to really watch and lower timing is 3200-3600 and 4600-5000. These are the spikes in cylinder pressure areas and for a FI car are VERY sensitive. The same shouls apply for NA but with more forgiving factors. You correct about increasing fuel accordingly.

I think with everyones knowledge on these subjects we will all have kick @ss tuned cars for every application. <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />