timing curve

[treeZ24]

anyone got a guess on what my timing curve should look like?

3.2L hybrid engine, 10:1 compression and a 260h cam.

i have it set at 12* base, ramps up to 34* by about 3400 rpm iirc and stays there.

i tried bumping all the values 2* more at all the ranges but the car felt like it lost power so i moved it all back to 12* base

[SappySE107]

34 is ok at cruise areas but thats a bit high for WOT. If that works, then cool, but its just higher than I have done on the various setups I have tuned. I dunno what your pistons are like though nore the combustion chambers so its hard to say.

[treeZ24]

3100 hypereutectic pistons by federal mogul and the heads were done by sharkey's dad, he just cleaned them up nothing serious in the combustion chambers.

i'm using 89 octane fuel right now with no detonation.

do you have any examples or maps that i could experiment with?

[SappySE107]

What setup are you using for tuning? The best way is to see what your gas milage is for the cruising areas, along with throttle response. If you don't have knock then thats fine. How did you get 10:1 using 3100 pistons?

[treeZ24]

from what i calculated, because the pistons come out of the deck a bit, using the cc's of the combustion chamber of the 3400 heads, having .020" shaved heads and having the block bored out .040".

dd2000 said something like 9.8:1 , i just said 10:1 cuz i was in a rush?

i'm using an sds em4-f standalone for tuning.

[SappySE107]

How is that setup? MAP vs RPM? Can you give me the increments or a picture of the table setup? You would probably be best off looking at a 3100 or 3400 spark table from the factory as they have more timing than the code I start with. Your compression isn't going to be a factor compared to stock.

[treeZ24]

you wouldnt happen to have that spark table would you?

i currently dont have any of the programs needed to veiw such data, nor the files.

uhm the sds system is set to rpms, whether the ecm takes that data and builds a map with the MAP sensor i dont know.

thanks for the info.

[TurboGTU]

I'd lock the base timming back to 9. Id would then advance the low rpm more advance like 2-6* and from 3k on to 4500rpm I would only do 1-3* and beyond that, back to stock. This is because of the cam. It doesn't breath well under, but it wakes up midrange alot. After that its back to stock.

You can add 3* to the base if you use 94oct.
Better breathing, high compression, fast burn headed engines don't like alot of timming.

[treeZ24]

I'd lock the base timming back to 9. Id would then advance the low rpm more advance like 2-6* and from 3k on to 4500rpm I would only do 1-3* and beyond that, back to stock. This is because of the cam. It doesn't breath well under, but it wakes up midrange alot. After that its back to stock.

You can add 3* to the base if you use 94oct.
Better breathing, high compression, fast burn headed engines don't like alot of timming.

sorry i dont quite understand the way you've worded the info there... should i be looking that the base 3100 spark table and modify it with your values ? or were you thinking of other specific values?

thanks for your patience lol i dont know much about spark timing..

[TurboGTU]

Well I looked at my A1 code and my TGP code. The initial spark advance is 9*or base timing. I guess if it were a ford..its with the spout out. No ecm controll and it only fires at that crank angle.

Well...I yet to look at 3100 spark tables. If your code started at 12*, I would then keep there and just move the main spark advance table VS map and RPM. I had success with my spark table something like how I explained it. I have the 260 cam but on a boosted engine. Off boost...it likes alot of spark advance in low rpm. mid range off boost is does good with just a little more spark advance than what the factory had..like 1-3*. Considering all the head porting I did...I thought I would need less than stock..but I don't. ON the boost..ofcourse I use less than stock...but thats another story.

Just keep doing what your doing. If it don't feel right..pull timming out. If its lazy..jump up one or 2*.

[treeZ24]

my timing starts wherever i want it to lol

its fully programmable with the touch of a button.

unfortunetly the system came with a base time more suited to sbc's, conservativly so they can break in etc.

i was talking with sharkey and he said he was running 38* timing total but he's got iron heads not the aluminum ones.

i guess i'll have to go find a program to start viewing some tables so i get an idea.

basicly my timing curve looks like this.

rpm spark

500 12*
750 12*
1000 12*
1250 12*
1500 15*
1750 19*
2000 23*
2250 26*
2500 29*
2750 32*
3000 34*

[SappySE107]

Is that WOT or what? There has to be something else unless that computer sucks. Load based is how it should work.

You don't want to go anywhere near iron head timing specs on an aluminum head motor. Is there a base timing? The GM computer has a spark reference angle of 59.8. Dunno if that really matters in your ECM.

Go to the downloads section, computer tuning or whatever to .ecu files. Grap the a1.doc file and look at the 0100 address. That is a stock 3.1 spark table. You can go from that to get an idea.

[treeZ24]

yeah ben thats wot, the reference angle, what is that for?

[TurboGTU]

There has to be one based on manifold presure..there has to be. If not...its not good for boost or only for racing use..where fine tunning doen't matter.

Its like having a distributor without the vacume advance. IT works, but not for boost or you comprimise WOT for part throttle performance or part throttle for WOT performance.

[treeZ24]

there is most definetly a timing modifier based on map settings. how i understand the system to work is you set your timing curve as a base map and then start adding numbers for map settings.