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Torque app & octane & timing question

2089 Views 6 Replies 3 Participants Last post by  GM Master Tech
Hi everyone. Long time lurker, happy '12 Eco owner on the East Coast of Canada. :)

I've read so much about octane it makes me jittery. This is not one of those "WHICH OCTANE IS THE BEST" type questions, more of a curiosity thing. I've decided with the cooler weather to drop down to 89, check out the timing with the torque app and then maybe drop down to 87 when it gets really cold.

I do the same highway route, same speed, regularly. When I used the torque app to watch the timing (running 91) while in 6th pulling up some grades (~115km/hr) the timing, according to the torque app, will go down to 1, .5, 0 and sometimes to -.5, -1 for a split second. I'm assuming that's when the knock sensors are doing their thing when it reads negative? I'm not lugging the engine and maintaining speed just fine at this point. Boost is reading 8-9PSI. These grades last for 15-20 seconds, so nothing huge.

Since I've been running 89, going up those same grades, the timing never goes into the negatives. Does this mean the ECU might be running on the 87 map now (I thought I read somewhere there is a map for 87 and 91..), and isn't pulling the timing back?

I'm not noticing any fuel mileage problems with 89, and the power still seems to be there, but was only curious to see why the timing isn't being pulled on 89. Perhaps it's just the cooler weather helping out?

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I'm curious why you never had a response. I'm going to check into the torque readings myself this summer with different octanes and ethenol or not.
You would have to be consistent and do it in the same weather and conditions.And yes lets say i went from 93 to 87 octane.After the re fueling event the car would switch to a low octane map.
Just curious how it works for mid grade? Does it jump between fuel maps. Since from my understanding there is only 2 fuel maps. High and low octane. Guess I'll just check to see numbers with performance. Be a lot easier once this winter blend crap is gone.
The motor is pretty much designed to run on 91 octane.They could never sell it in the US market if it had to use 91.Or lets say the sales would not be as good.So they just us High and low octane maps.Look at it as a protection type system.More or less balance between 87 and 91 octane.Even with my aggressive tune if i threw 87 in it.The engine would go to low octane map.But in my case it would pull a very noticeable amount of power.In your case it wont be real noticeable to the driver.I never do that because the pre ignition event (engine ping) would be more pronounced in my case.Just not something i want my motor to have happen to it.
Just wish there was more u could do to tweak these cars outside of having a tuner play with ECU. Knock sensor is overly sensitive that's for sure. I mean I run 45+ mpg all the time right now pushing 50. I don't go wot so basically the knock sensor is bubble wrap around the box full of packing peanuts. IMO the knock sensor shouldn't really kick in until your over 60% throttle. The power it pulls is typically due to the phantom knock anyways. The knock your getting under 60% is minimal and should be that detrimental to the interworking of the motor. Obviously there should be a threshold set. But it pulls power for any knock it seems even at 30% throttle. I'm no tuner so not sure how all of this is written up in programing but if there were steps to the level of knock retardation? it would be nice. If there were no knock sensor I bet I would be fine to put 200k on the car yet just due to how easy I drive it. Bet 55-60 mpg would be more feasible as well.
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Thats interesting.My car pulls no timeing to very little to speak of.I beat the **** out of it one real hot summer day to just to see if it would after the V Tuner tweaked my power up over his base tune.Of course at my own risk.The car really brings the TQ in fast.Stock the 1.4 feels detuned to me.The new engine even more so
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