1G: factors that affect timing and to what degree

[IronnFisTT]

ive noticed that some dsm'ers are getting around 20deg timing with even a fair amount of knock (10+). Ive been datalogging my car and noticed that I was only getting 13deg max timing and that was with knock counts under 6. Ive read on the TMO pages that knock, intake and coolant temps have an affect on timing. Everywhere I read, people only talk about knock effecting timing. So I decided to put in some 100 octane. It eliminated knock completely... at which point, I was only able to get a max of 15deg timing by redline. I was only able to gain 2 degress by eliminating knock completely. I then let the coolant temp come down from 202 to the 180s and pulled my headlight so intake temps went from 140 down to 70s.. which yielded me 19deg! Anyone know at what magic numbers the ecu pulls timing at and how much it pulls? I already know what it does for knock, i want to know what it does for intake and coolant temps, this is taken from the tmo pages about knock:

3 or below, the ECU will advance timing.
Between 3 and 7, the ECU leaves timing alone.
Higher than 7, the ECU will begin retarding timing.

For those guys that get 20deg timing on pump gas with some knock, what do your intake and coolant temps look like? What other factors could cause my lack of timing advance?

Lastly, I have set my base timing to 5btdc, ive checked and made sure that my cam gears arent off any teeth, theres no boost leaks except a tiny one in the TB. Im running a 14b, runs were logged at 14psi only.

thanks in advance,
attia
94 Tsi AWD
98 Supra Turbo

 

[nine5raptor]

Max timing I see on a 2G with coolant temps at 206 and intake temp permanently set at 80* (gm maf, so I don't know what my intake temps actually are) is 13* advance. This is with it leaned out some on stock injectors. Completely stock, I saw 7* The guys who post big timing numbers even with knock are running big injectors. The ecu will pull timing with higher injector duty cycles so with big injectors, dtc stays low and timing stays high.

 

[IronnFisTT]

A guy on the chicago mailing list said that the 2g ecu pulls 1deg of timing for 205+ F, and 2deg for 224+ F coolant temps. And pulls 1deg for 84+ F intake temps. Anyone got this info for the 1g?

Its good to know that a low inj p/w increases timing. I got 640cc inj in there right now with a 2g maf and im leaned out about 15% across the board. I guess could lean it out some more.

-attia

 

[kpt4321]

Timing advance is *not* related to IPW, at least not directly. The timing maps are indexed off rpm and airflow, in a similar manner to the way the fuel maps areindexed. Higher airflow rates (this is total calculated airflow, not Karman Hz) yeild lower timing.

As such, simply installing bigger injectors will not change the timing. Also, if you use some device such as a PMS (or DSMLink) to alter the IPW *after* the ECU outputs it, this will not change the timing.

The reason bigger injectors give you more timing, is because the majority of people use a SAFC in order to compensate for the extra flow. The SAFC reduces the Hz signal that is seen by the ECU, and as such it sees less total airflow, and gives you more advance.

Knock also effects timing, obviously.

If IAT goes over a certain temp, it pulls timing, as mentioned above.

There are all kinds of little safety modes within the ECU as well, that will pull timing.

....Kyle T.

 

[nine5raptor]

gotta love all of those little "safety protocols"

 

[DSM90AWD]

On my 1990 I saw Timing up to 23deg on one of my last track runs (<6 counts knock) w/VP110. DATALOG
I noticed that my knock came in the form of "tip in" Knock (i.e. btw shifts) which would reduce to 0 by gears end.. and worsened as I leaned it out. I'm considering running a "dead" knock sensor next time at the track to see if I'd get more timing. You can also see by the O2s I'm horribly rich too.

I also remember Todd's discussions on the ECU "Learning" from past knock events..etc which would lower your max timing for a set period of time or until the ECU is reset.

I've a 180deg thermostat in my toolbox.. seems also a good idea to mitigatte pulled timing.

 

[pneumo]

Yeah, the ECU remembers knock. I once saw a max of 9 degrees of timing with no knock. Since then I leared to sweat the details, keep the intake temps down and keep the engine temp down.

 

[DSM90AWD]

Leaned the S-AFC from +8 to +3 and now see up to 24deg advance on 93pump on 2nd-3rd romps (was 20-21deg).

I never thought of the correlation of S-AFC settings and the ECU timing maps so great thread! Still don't see any significant knock.. so more room to go.

 

[IronnFisTT]

wow, thats alot of timing. what injectors and turbo are you running?

-attia

 

[DSM90AWD]

small 16G, 2G MAS, RRE FMIC and 550s w/base FP set at 40psi, base timing 5Deg (check profile for more).

This run was with a homade coldair box ala popup headlight
Only saw 1-3 knock >6500RPMs ..otherwise 0

 

[ItsStockOfficer]

On my 20g, I used to run 12.6's on 450's and no fuel control. On race gas I could get perfect knock, but at 6000 rpm, I could have zero knock and 10 degrees of timing because the ecu was seeing so much airflow. Hated it. After I got 720's I could always get much more timing for the same amount of airflow.