A/F ratio and ignition timing

I just started running ignition timing with MS and built a pretty good spark map. Im running 16psi on the 14b and had a good bit of knock around 5k and 6k. My AFs are in the mid to low 11s under boost. I set all timing advance to 14 degrees when above 125kpa and over 4k rpms and all knock went away. My question is what kind of timing advance do most people see under boost? I thought I should set advance to 15-16 degrees around 5k which is peak tq and start advancing after that to around 18 degrees at redline.

I plan on slowly start advancing timing till I start seeing knock then retard it 1 degree but I would at least like to have an idea of where I should be in boost.

yea thats right on man. Most people make high teens timing advance on pump gas near redline. Obviously more if you can run higher octane. your numbers look good!

so how much does timing effect hp. Say I can only run 16degrees of timing max around 16psi with out knock. Would it be better to run higher boost with lower timing or say drop the boost to 14psi and run 18-19 degrees of timing. I know most of this is trial and error and see what works best.

Steviek - What does your timing look like at full boost from 4k - redline?

Also if I lower the AF to say more around 11.0 would I be able to run another 1-2 degrees? And would this be better than running a little leaner as far as HP and running the motor safely.

Typically more power can be made from boost and timing than extra lean conditions yes.
4688 rpm 11.2d
5081 13.3
5531 14.7 peak ve begins to end
5981 18.6
6510 19
7009 18.3

as for what is better boost or timing. Boost is until your compressor efficiency starts to drop off. When that happens then it would be far more productive to cease to raise boost and begin increasing timing (provided no knock) only a compressor effieciency chart can tell you when that is.

http://www.stealth316.com/images/td05h-14b-cfm.gif
flow map


http://www.stealth316.com/images/td05-14b-raw.gif

Raw map



Reference Site
http://www.stealth316.com/2-3s-compflowmaps.htm

So on the 14b anything over 18psi is no good basically. So I need to raise the boost a tiny bit and get the AF in the low 11s or so and then slowly increase timing until it knocks. And thats all the power the motor will push on this turbo.

Here is my spark map right now. I added a little timing around 6k and have yet to test for knock. I rarely see that part of the map anyways. It seems that you run real low timing around 4k or so. I always thought you should start around 20 or so at 3k, drop to 15 around 5k and increase a little more toward redline. Check out my map and let me know what you guys think. I hit about 16psi @ 3500rpms.


http://i189.photobucket.com/albums/z173/SilvrEclipse/SparkMap.png?t=1220477898

Ya anything under 4500rpm i don't even really bother with because I don't make any power there anyways. Your timing chart looks pretty solid for a base tune but it really means nothing without knock being registered at the smae time.
Ilike the colour coordination showing you what is aggressive (red) and safe (green) I think that feature helps a lot cause you whant to see smooth colour transitions not a red bloch beside a green one type of thing. I like MS.

If I run threw the gears all at full boost I can keep the turbo spooled at low rpms so Im going to lower the timing in the high boost/low rpm range so if I happen to hit that point some it wont be such a jump in timing when it goes down to 15degrees or so. It needs a little more work but the car runs good for now. I want to hit up the track next week so I may do some more tuning this week. Im going to run a pretty safe tune so no chance of knock.

It is a real pain for MS to log knock. And even when you get it working it phantom knock is still a problem. I tune for knock by listening to the motor. I have a stethyscope(sp) type system I am using and its sweet. You can hear any bit of knock but you just have to remember at what rpm range it was at.

MS is pretty f*ckin sweet. I wish I would have gone to in a long time ago.

Steviek - What are your intake temps at under boost? After a few hard runs mine are around 140F. Temps here are around 90-95F. I would like to get some logs done at night to see how much the temps drop and how that effects knock and AF ratios.

A little off topic, but should I be concerned with heat soak on the intercooler at the track. I was planning on taking a bottle of ice water and soaking the intercooler between runs with it.

MS is pretty f*ckin sweet. I wish I would have gone to in a long time ago.

A little off topic, but should I be concerned with heat soak on the intercooler at the track. I was planning on taking a bottle of ice water and soaking the intercooler between runs with it.

I would love to get MS at some point, but I don't know if I'll ever get to that point in this build.

If your temps down there are mid 90s, I would say heat soak would be a problem. It'll probably be sitting out in the sun for a while right? Never hurts to ice it down.

Now I don't know what ambient temperatures were this day but my intake temps are pretty good relative to other people. Especially under WOT. I have my intake dam which keeps the engine heat away and if I'm racing I take out my passenger light which basically rams in ambient temp air. o On the run where I gave you the timing numbers I did not have my light out and my intake temps were as low as 83f with a max of 97 right after a shift.

Compressor efficiency doesn't mean anything with good intercooling. Just food for thought. As far as the timing goes, that seems too high to me at peak cylinder pressure. The 2g timing map is a great place to start, you should be able to find it in the DSMlink documentation. I build it into my AEM cal files as a starting point, even on the RWD.

Thanks for the info Kevin. I would actually like to get a hold of a 4g63 timing map but cant see to find one online. Maybe someone with link could post up a screen shot on theirs?

Kevin what should my timing be at peak pressure? 13degrees, 12degrees? 14 degrees seems to run with no knock right now but maybe Im on the verge of getting knock and to run 13 or so may be a little safer? Is that what you were getting at?

Also how much more HP do you get from advancing the timing. I wouldnt mind runing a little less to be safer if I was only going to loose like 5-10hp. But I dont want to lose 30.

http://jeffgst.com/id20.html

Yea you won't lose 30hp with one degree of timing. BUt if you're not knocking why bother?

Awesome link steviek. Thanks

Im going to build a new ignition table that is pretty close to the stock 2g one and see how the car runs with each map.

I've found that you can be running as much as 5 degrees too much without knocking. The only way to be sure is on a dyno. When you stop picking up significant HP with each degree, you've gone too far, and it has nothing to do with knock. Assuming there is nothing "wrong," knock comes in well after the point of diminishing return. On pump gas this conversation gets a little more complicated, but the principle is exactly the same.

I don't have the timing maps handy, but if you are reaching full boost below 3500-4000 rpm, you should probably be in single digits at this point. Of course with this being a 420A turboed (I think), boost may be lower, making 10-12 acceptable. Only way to be sure is on a dyno. Prefereably one that can load the motor and hold RPM while you tune.

Wow single digits. I never thought I would have to set the timing that low.

The car blew out the exhaust manifold gasket again and one of the studs stripped. I got a gasket I can put on it but I need to have a helicoil installed also. Damn it is always something with this car.

There is something I dont really understand. When the turbo spools up it will hit 16-17psi around 4k or so. The wastegate opens and boost stays there only for a sec and then starts to drop as the rpms increase. By 6k Im only at 14psi or so. The thing I dont get is that the wastegate will stay open allowing the boost to continue dropping. I am running the wastegate off the intake mani so shouldn't the gate close as boost drops? I know I should check for boost leak and the BOV leaking but the wastegate should still be closing I would think.

Boost dropping as RPM increases is generall a maxed out turbo. It seems like a 14b should be able to hold that boost to redline though, so something could be up. Boost leak, etc. It's possible that head just flows really well, but I don't see cams in the sig, so I'm not sure how likely that is... Turboed 420s are completely outside of my experience.

The 14b cant be maxed out yet. The head should flow pretty well, it was ported pretty good along with the intake manifold and I upgraded to the 60mm TB. It just doesn't make sence that the wastegate doesn't close when the boost drops. I got a bad exhaust leak today before the turbo so maybe thats hurting it also. Here is a log I took earlier today, you can see the boost dropping off and also the intake temps shooting way the hell up there.

Is the cheap ebay FM why my temps raise so high so fast? Ambient was probably around 90F or so.

http://i189.photobucket.com/albums/z173/SilvrEclipse/MSlog.png?t=1220923674

That boost taper doesn't seem like enough to worry about. EVOs do it too, I've never been able to get rid of it completely on mine. Is MAT the temp? If so, it looks to be on par with a mediocre intercooler. A good IC will only allow a 10-20 degree temp rise on a quarter mile run.

Hoping to install a small 16g in the next few weeks. So we will see if there is any change. The MAT is the manifold air temp, I guess a nicer intercooler would be a good bit more efficient. Then again the temps here are in the 90s. Once it starts to get cooler Im sure the temps will not rise as much. I should do a few runs in the evening and compare logs.

Temp rise has little to do with starting temps, since the air cooling the core is the same temp throughout the pull. Efficiency will change, but the result is insignificant. Your numbers aren't terrible, fairly average. Only the very best of cores will provide the performance I mentioned above. In fact there are only two that I am aware of, the most popular being the garrett 24x13x4, which is more than most people are willing/able to run.

Mine is a good bit smaller than that. I think its around 24x7x2.5. How much does the intake temp effect knock? Say between 100F and 140F. With a 40 degree increase in air temps is the chance of knock going to increase a good bit also or not enough to notice.

from what I understand and don't quote me on this. I think 10 degrees equals about 1 degree of timing. So 40 degree intake rise may require you to subtract about 4 degrees of timing.

from what I understand and don't quote me on this. I think 10 degrees equals about 1 degree of timing. So 40 degree intake rise may require you to subtract about 4 degrees of timing.


Holy shit - thats not really what I was expecting. I guess that is why people make so much more power with meth injection systems.