testing timing advance

[juma]

Thought I would generate some data and see if timing is advanced with higher octane gas. Using my Actron III that can read timing advance I got out on the highway with just regular in the tank. I floored it at 70 mph on flat ground and got 12 degrees advance as the motor wound up. At a steady 70 mph, flat ground, and a load of 52 (just a figure of merit, probably an approximation based on vacuum), I got 28-30 degrees of timing.

I had about 7-8 gallons of regular in the tank and I added 10 gallons of 93 octane. This should have put the average octane in the tank up to at least 89 and maybe 90. After driving around for about 20 miles and sloshing the tank pretty good, I hit the hiway again. On a flat stretch, at 70 mph, it seem like maybe I got a steadier 30 degrees of timing. But, on the full out acceleration from 70 on flat ground, I got the same 12 degrees of timing advance. WTF.

I was expecting to see some more advance than that and hoping I would too. I'm gonna give it another test tommorrow on a run I have to make south on I95. Maybe it will show something different then.

Right now, I gotta conclude the Titan can't advance timing for more performance but maybe can slightly at cruise for better gas mileage. I could see the logic in that to protect the truck when running it hard but still gain something with higher octane at cruise.

still wondering - juma

[Slurppie]

Would the ECU have to learn that the truck has higher octane gas? Maybe learn and change to a different fuel map?

[juma]

Originally Posted by Slurppie

Would the ECU have to learn that the truck has higher octane gas? Maybe learn and change to a different fuel map?

yes, but this is something that happens continuously and rapidly. Most ECU's I am aware of are always running the timing up and checking for knock. If they get knock they back off. If not, they press on till they do. The titan has knock sensors in both cylinder banks and I assume it makes this test all the time too. it should learn it pretty quick, if it does learn, because if you are going to better mileage with a fresh tank of premium, it has to start happening pretty quick. In cruise, the timing flutters around adjusting to the load, throttle, etc. But on hard accleration it is rock steady (like it was hard wired for that). anyway, just making educated guesses...juma

[Slurppie]

I would guess that a quick way to test your theory would be to remove both knock sensors for a very short period of time and see if the timing changes.

[juma]

If it didn't receive a knock sensor signal it would most likely hold to some conservative timing advance and throw a code. It wouldn't run off the end of the scale and give you a buttload of timing. juma

[Slurppie]

Don't actually remove the sensor out of the loop, just off the cylinder banks. Nissanperformancemag.com did some dyno testing on a Sentra SE-R where they moved the knock sensor to the firewall and picked up some hp. Of course this can be dangerous but for testing it would be interesting to see.

[juma]

hmmmm....yeah, that might work but you are playing with fire:>) I thinking that full on 12 degrees is a hard factor and not variable but if it varied on a sentra it might on the titan too. but, as far as just putting premium fuel in and getting more horsepower, I'm still not convinced it works. juma

[JetTech]

sounds like your close to answering the question I've had for some time Juma. I look forward to reading your results after the 93 has been in there for a little while...

thanks for the great work....

[Titan Power]

12 degrees seems pretty low. Maybe if the ECU sees high knock counts, it gets more conservative with the timing and takes longer to build back up.

I don't know much about the Titans ECU programming, but on the cars I'm familier with (turbo Mitsubishis) the ECU stores an "octane value" that remembers the degree of knock expirienced over the longterm. It drops the more knock is expirienced. The lower the rating, the more conservative it is with increasing timing, even without knock. Even adding 110 octane race gas, it takes a few runs before the octane value increases, and the ECU allows more timing. If I reset the ECU, the timing goes up right away.

Like I said, 12 degrees sounds low. On my cars, I shoot for around 20 degrees under full boost, and that is on a highly stressed little 2.0 The ECU could be programed to allow less timing at certain abouts of airflow or throttle openings. If so, I bet quite a bit more power can be found with some tuning.

It's too bad you can't datalog actual knock counts.

Jason K.

[juma]

Originally Posted by Titan Power

12 degrees seems pretty low. Maybe if the ECU sees high knock counts, it gets more conservative with the timing and takes longer to build back up.

I don't know much about the Titans ECU programming, but on the cars I'm familier with (turbo Mitsubishis) the ECU stores an "octane value" that remembers the degree of knock expirienced over the longterm. It drops the more knock is expirienced. The lower the rating, the more conservative it is with increasing timing, even without knock. Even adding 110 octane race gas, it takes a few runs before the octane value increases, and the ECU allows more timing. If I reset the ECU, the timing goes up right away.

Like I said, 12 degrees sounds low. On my cars, I shoot for around 20 degrees under full boost, and that is on a highly stressed little 2.0 The ECU could be programed to allow less timing at certain abouts of airflow or throttle openings. If so, I bet quite a bit more power can be found with some tuning.

It's too bad you can't datalog actual knock counts.

Jason K.

hmmm....I'll flog it some more this morning on the way to work...

[juma]

Looks like the guys who said it needed to learn were right. After another 30 miles or so, I whamed it at 70 on flat ground and it jumped to 7, then 12, then 16 degrees advanced. I tried it again 25 miles later and this time it stepped up to 19 degrees advanced. I am leaning now to the view that the ECU does sense better gas and advance the timing.

I'm am gonna run through a tank or two of regular and get it pure again and try it just to make sure I didn't hold long enough to see the advance. I'm pretty sure I did, just want to make sure.

I think I can feel the difference with premium. It may be more noticeable because I have a Gibson swept-side and K&N panel.

I've got a trip to canada coming up in September and that will be a good time to use the ACTRON III to monitor timing while I try different grades of gas. juma

[JetTech]

juma, on the dyno we noticed that the engine will make better numbers if you roll into it rather then slamming it to the floor. Have you tried this to see if the timing goes higher with a gradual application of throttle?

[juma]

no. I can try it next time I'm testing. maybe thats why when you slam it, it retards to 7 degrees, and then builds back up in steps? but hey, doesn't that 19 degrees of advance sound like it means business? juma

[rvsixer]

Originally Posted by JetTech

juma, on the dyno we noticed that the engine will make better numbers if you roll into it rather then slamming it to the floor. Have you tried this to see if the timing goes higher with a gradual application of throttle?

And I thought I was imagining things...but I notice this solely via seat of pants, consistently. I seem to get far better response "rolling" on the throttle till the first shift, and then agressively moving the pedal down afterwards. If I slam from the start, it goes but your really can notice a bog.

Juma thanks for the research on this...very interesting and valuable.

[Big Platinum]

Isn't the initial timing on the Titan set to 15 deg BTDC. It really shouldn't dip below that, and should advance into the 30's as it revs.