Timing Curve

[jibberishballr]

I was wondering what a typical timing curve should look like? I've been reading up and understand it should be higher at what and it should typically increase as it does in rpms. Does anyone have some typical numbers on a 2g that are healthy? Also any links to timing thorougly explained would be helpful.

Thanks

Josh

 

[Kevin Jewer]

On our cars there is no magic in timing. We really can't run the "ideal" timing values under load, so we just run as much as we can without knocking. In some unusual cases on high octane race gas (~117) and relatively low boost you can actually get mechanical damage before it knocks (ask me how I know), but it's very unusual. Careful experimentation on your specific setup at the track (trap speed) or dyno is the best way to optmize timing.

That being said, the 2g max load (over 2.1 g/rev airlfow) timing curve tends to do pretty well in my personal experience, on 1Gs and EVOs as well. It's pretty linear, 3500 rpm is 4 degrees, rising to 16 by 6k rpm where it flatlines. I would continue that trend upward to your redline, or move the 16 degrees to your redline and interpolate (I prefer to do the former). This is a good starting point from which to do your testing.

Getting into a little bit of the thought process behind modifying the curve, it should generally rise with rpm since higher piston speed vs static burn rate requires more advance. You may want to depart slightly from the linear curve at times. For example, pulling out another degree or two at peak torque (peak airflow/rev, peak airflow based cylinder pressure, typically occurs as soon as you hit full boost, then tapers). I do this especially when on nitrous, since having the nitrous hit before the fuel (nitrous pressure higher than fuel pressure, etc) at the same exact time as the boost spike I get with no signal to the WGA isn't necessarily a good thing. At the track this is 6k rpm, so my race timing curve looks odd. You can also get a little more aggressive at high rpm due to VE dropping off, or get a little more conservative if that's how you roll. And so forth.

Another point worth making is that due to the slow decay rate of the stock ECU, a couple degrees of knock retard early in the gear can bollix the rest of that gear to redline. So start taking out timing at the lowest RPM breakpoint that correlates to the knock retard only. Odds are it will clear up a whole gear's worth of knock. The ECU will reset the knock retard at throttle lift, so if you no lift shift it can actually carry on into the next gear, unless you have DSMlink which has been updated to clear on clutch in as well.

 

[jibberishballr]

Thanks. That was really helpful info.

I figured id put my setup down for what i will be running and maybe some people with similar setups or any estimations could put what kind of timing numbers they think are good.

Evo III 16g- now running 14psi of boost..will be at 18 or so when i get bigger injectors(550-650)
tuning with safcII+datalogger, turboback exhaust, intake, mbc, and some other basic stuff (drivetrain, suspension, tires, etc)

On our cars there is no magic in timing. We really can't run the "ideal" timing values under load, so we just run as much as we can without knocking. In some unusual cases on high octane race gas (~117) and relatively low boost you can actually get mechanical damage before it knocks (ask me how I know), but it's very unusual. Careful experimentation on your specific setup at the track (trap speed) or dyno is the best way to optmize timing.

That being said, the 2g max load (over 2.1 g/rev airlfow) timing curve tends to do pretty well in my personal experience, on 1Gs and EVOs as well. It's pretty linear, 3500 rpm is 4 degrees, rising to 16 by 6k rpm where it flatlines. I would continue that trend upward to your redline, or move the 16 degrees to your redline and interpolate (I prefer to do the former). This is a good starting point from which to do your testing.

Getting into a little bit of the thought process behind modifying the curve, it should generally rise with rpm since higher piston speed vs static burn rate requires more advance. You may want to depart slightly from the linear curve at times. For example, pulling out another degree or two at peak torque (peak airflow/rev, peak airflow based cylinder pressure, typically occurs as soon as you hit full boost, then tapers). I do this especially when on nitrous, since having the nitrous hit before the fuel (nitrous pressure higher than fuel pressure, etc) at the same exact time as the boost spike I get with no signal to the WGA isn't necessarily a good thing. At the track this is 6k rpm, so my race timing curve looks odd. You can also get a little more aggressive at high rpm due to VE dropping off, or get a little more conservative if that's how you roll. And so forth.

Another point worth making is that due to the slow decay rate of the stock ECU, a couple degrees of knock retard early in the gear can bollix the rest of that gear to redline. So start taking out timing at the lowest RPM breakpoint that correlates to the knock retard only. Odds are it will clear up a whole gear's worth of knock. The ECU will reset the knock retard at throttle lift, so if you no lift shift it can actually carry on into the next gear, unless you have DSMlink which has been updated to clear on clutch in as well.

 

[donmagicjuan]

In some unusual cases on high octane race gas (~117) and relatively low boost you can actually get mechanical damage before it knocks (ask me how I know)

Ok, how do you know? I love story time.

 

[Kevin Jewer]

Basically, I have seen it on pump gas (with knock) at 28 degrees of advance (don't ask) at 63 lbs/min, and at some mid 20s level of advance in similar conditions with race gas (no knock). In both cases the spark plugs came apart in small pieces ruining the motor and turbo. My problem is that I'm not afraid to blow things up in the name of experimentation and data collection.

 

[scottsee]

Kevin, You are by far the most intelligent, helpfull DSM'er I have ever encountered in the past 3 year I've been around the game. It's amazing the things that come out of your posts. It's nice to see you around again..

 

[donmagicjuan]

My problem is that I'm not afraid to blow things up in the name of experimentation and data collection.

Spoken like a bona fide engineer of the highest caliber. Amen to that.

 

[Kevin Jewer]

Thanks for the kind words. I'm still not sure if it's really intelligence, or just insanity combined with a lot of actual experience.

Yesterday I spent an hour or two doing my whole AEM timing map over (instead of sleeping of course...). I used the 2g map as the base and rescaled to fit my map. I set the high load line to coicide with the 17 psi load row tapering it down slightly to 30 psi, and manually scaled it up from 6000 up, as stated above, to 9500 rpm. Essentially it's a boost dependent (as opposed to airflow) 2g timing map with this 6000-7500 flatline removed and continued to 9500. Looking at the shape of the map this looks much better than the cobbled together hackjob I have been using. Can't wait to try it out today.

 

[94Jettameowpsst]

wtf
you said pump gas, 28 deg adv. and 63lb/min in the same sentence WTF

 

[aero_sallee]

Basically, I have seen it on pump gas (with knock) at 28 degrees of advance (don't ask) at 63 lbs/min, and at some mid 20s level of advance in similar conditions with race gas (no knock).

Sounds like a recipe for engine internal soup.

 

[jibberishballr]

So does anyone with similar setups or any estimations could put what kind of timing numbers they think are good? I know i cant get exacts just something in similar range to look for when tuning.

Also i forgot to mention this will be on 91 octane (California)

Setup Below:

Evo III 16g- now running 14psi of boost..will be at 18 or so when i get bigger injectors(550-650)tuning with safcII+datalogger, turboback exhaust, intake, mbc, and some other basic stuff (drivetrain, suspension, tires, etc)

 

[LRS95TSI]

i would say when you hit boost probably arond 8-11 deg and maybe 16-18 deg at redline...my midrange on this simlar setup kinda sucks...i get like 12-14 deg between 4300-5400... but all our cars are diff just gotta see what it likes.

 

[JayRolla]

Ok so what about 1g's because I know I flat line at like 24* and my brother at around 26*. Is this bad on our motors?

 

[iiiwildfireiii]

wtf
you said pump gas, 28 deg adv. and 63lb/min in the same sentence WTF

Wow. I think I've seen similar results with engines using napalm as fuel. I'll bring the marshmellows.

 

[spyderturbo007]

Kevin, You are by far the most intelligent, helpfull DSM'er I have ever encountered in the past 3 year I've been around the game. It's amazing the things that come out of your posts. It's nice to see you around again..

I agree completely. I have learned so much from you over the past couple of years it's not even funny.

My favorite posts are where you tend to ramble on paragraph after paragraph. I really look forward to those. But not to the 2+ hours I normally spend searching the net so I can understand what you are saying.

Thanks a bunch for imparting your wisdom on the members of this forum.