A couple questions on knock retard from a total newbie

[Buick Encore]

1.4L Turbo in a 2013 Buick Encore (same drivetrain as Chevy Sonic/Cruze)

I just received my VCM Suite and all I've done so far is use the scanner. Right away I noticed this little car tends to really pull timing out on the highway when climbing hills, especially in hot weather. I had suspected it was doing this, since you can easily feel it when driving.

Would it be OK to try adjusting some of the tables related to this, a bit at a time, until I hear a little occasional knocking? I never hear any knocking at all now (I often drive with the windows down and radio off). I don't know if GM is being overly-cautious with this or not.

Also... before doing any flashing, what if I temporarily unbolted the knock sensor from the engine block to see what effect it has on the scanning data etc? I'd drive the car very carefully.

I know these may be dumb questions but thanks in advance for any input.

By the way... I'm having second thoughts about changing anything regarding the turbo. I'm getting great gas mileage and the stock boost, while conservative, looks pretty reasonable to me. I think if I can do something to reduce the way this car retards timing half the time, I'll be happy.

[Iam Broke]

Log Knock Retard on all 4 cyls and see what cyl it's happening on and when. You should reduce timing in these areas for longer piston life. Adding more advance is just going to make the ECU pull more timing due to knock.

Also log intake air temps to see if it only happens when the intake air is hot, if so you can reduce the IAT advance.

Fill up with 93 or 91 octane to see if it's real knock. It'll decrease if it is.

[Buick Encore]

Yeah, I had a feeling the knock sensor might defeat anything I try to advance timing. There's a table for knock sensor sensivity or something like that. What if I made it less sensitive? I'm not too concerned about long-term engine life since I've always traded cars every couple years. But of course I don't want to blow a hole in a piston or anything either

In regard to fuel grade... I've run both premium (91 around here) and regular (87) and there's only minor differences in knock retard. This coincides with my driving experience with this car... if anything, it seems "livelier" on regular. Weird.

[cobaltssoverbooster]

dont change the sensitivity unless you understand everything about knock sensors and how to set them up properly

[Buick Encore]

Thanks for the input. I don't, so I won't.

Is there anything I can do to simply advance the the over-all timing on this thing a little? I guess I should mention that I'm 55 yrs old, so I remember when I used to be able to do this by just rotating the distributor a bit

[Buick Encore]

Just an update... I searched this forum yesterday for info about this stuff and didn't find anything. But I just stumbled on a post in one of the "newbie" sections about eliminating knock retard. For some reason I didn't think of the fact that I need to experiment with reducing knock retard, before trying anything else. So this should get me started.

[wgr73]

In regard to fuel grade... I've run both premium (91 around here) and regular (87)

Do not run 87 in a turbocharged vehicle, ever, especially if 91+ is available! Run the highest octane you can! Knock kills your engine fast, and the lower the octane the more prone to knock it is!

In regards to knock and the car pulling timing. Log those areas, if it pulls 3*, then try pulling 1* in that area and see if it goes away. If it pulls 4*, try removing 2* in that area and see if it goes away. Don't pull the full amount of timing, it's likely you can mitigate the issue by pulling a degree or 2. Let us know how it works!

[cobaltssoverbooster]

KR is fuel pre-igniting due to cylinder heat.
cylinder heat rises fast in boosted cars so with junk fuel like 87 octane the ignition temperature is lower than premium fuels. this causes the fuel to ignite somewhere in the cylinder before the spark plug gets to it and starts a flame front. then when your spark plug ignites like its supposed to it starts a second flame front. when the two flame fronts smash into each other you get a high pressure spike that is super hot. imagine a torch, now as you let the ignition knock imagine you holding the torch steady over the top of your piston. cylinder heat rises so fast under kr you weaken the ring lands as they try to disperse the heat in the piston and then snap you have no ring land and your motor is toast. the other effect that's just about as common is people let it knock so hard for a long time it blows a hole straight through the top of the piston. looks like something nitrous motors do when stuff goes wrong.

run the 91 premium fuel and give yourself the extra barrier of safety. turbocharged or supercharged vehicles running boost any higher than stock should be on premium fuel only, no if's and's or but's. too much cylinder heat in the modified conditions.

[Buick Encore]

Thanks for the additional info.

wgr73 - The approach you suggested to reducing KR is exactly the approach I'm going to use. I need to go at all this real gradually, since I don't really know what I'm doing. Plus the car is only 5 months old.

cobaltss - Thanks very much for the info. I spent a couple hours on Google last week trying to learn more about this stuff, and honestly your post was more helpful for me. Really appreciate it.

The first thing I'm going to do (just kind of for practice) is replace the low octane table with the high octance table (so both tables are the same). This shouldn't hurt anything since it'll just affect "learning", not actual KR. I've done the editing, but to be honest I'm a little scared to actually flash my car. I'm afraid I might accidentally totally brick it or something

[wgr73]

Thanks for the additional info.

wgr73 - The approach you suggested to reducing KR is exactly the approach I'm going to use. I need to go at all this real gradually, since I don't really know what I'm doing. Plus the car is only 5 months old.

cobaltss - Thanks very much for the info. I spent a couple hours on Google last week trying to learn more about this stuff, and honestly your post was more helpful for me. Really appreciate it.

The first thing I'm going to do (just kind of for practice) is replace the low octane table with the high octance table (so both tables are the same). This shouldn't hurt anything since it'll just affect "learning", not actual KR. I've done the editing, but to be honest I'm a little scared to actually flash my car. I'm afraid I might accidentally totally brick it or something

Do it the other way around. Likely the High Octane table has more timing. If you want to be conservative and work your way up, start low. You will feel a difference in power but it should be a lot safer. Log lower oct timing then raise it slowly (mid-high load areas, those are probably the only difference in the tables). Once you start approaching the high octane timing, just cut/paste that table. If it's knocking then do what I said in my above post.

[Buick Encore]

I see your point. I'll start the other way around.

My main problem right now is getting up the nerve to flash the ECM. I'm not too concerned about my changes, since I can always go back to the stock flash, but I keep worrying that something might go wrong with the process of flashing. I'll do it one of these days... I might have to get a little drunk first so I don't worry so much. j/k !!

[wgr73]

Lol! Dude, nothing will go wrong...the cars nowdays have built-in flash protection, meaning its extremely hard to brick an ECU. If the flash doesn't go thru (i've never seen this) just don't turn off the key and try again. No big deal!

[cobaltssoverbooster]

Like he said flash calibration saver makes it so it won't start. It will still talk to hpt to receive a flash but t that point you will have to revert to a write entire.

All you do now is run you engine for 3 min and shut it off. Have your changes ready then tell it to write calibration only. When its done start it up.


I've flashed my 08 factory ecu about 2800 times for varying setups and its still rocking. Take the leap man.

[Buick Encore]

I really appreciate the encouraging words. I had this worry before I even ordered, and hptuners told me this stuff too. Been busy with other stuff so I haven't had much time to mess with this lately (it seems like I'm actually busier since I retired!). But I'll get to it pretty soon and I'll report back.