Knock on colder days

[ThikStik]

Since having no K this summer on 16-16.5 psi, im wondering why i have 4-5 deg of K and boost goes to 17, 17.5 on cold days. Chip is a 18 psi Testa. My thought is that more air=more boost, cylinder pressure=K given the same fueling and timing.
I almost grenaded motor on a hi end pull and its smoking now. It pulled good till the 3rd time in wot. I also suspect winter gasoline blends. Gas stations are a big enemy to us all, I bet they count on cold days to quell K and chince on octane. Anybody have this? Thanks

 

[Stage 5]

On colder days the air is more dense, boost goes up, but you could adjust back down a 1lb or 2 to compensate a safe and more powerful level with pump gas only. HTH

 

[Razor]

I almost grenaded motor on a hi end pull and its smoking now.

If its smoking something changed. Riding on the edge of knock is dangerous.. and as to the octane thing.. you guess why i'm in business

 

[Ormand]

I've noticed this same problem. You get cooler air into the turbo, plus cooler air flowing over the IC, and that gives you a "double dose" of cooling, thus more air (in gm/sec) into the cylinder. Should show up as higher flow through the MAF, if you have the ability to measure that high, like an extender chip. Seems like the ECM would be "smart" enough to figure this out- more gm/sec at a given rpm means less solenoid duty cycle, or more fuel, or less timing, or something. On the other hand, it does seem to "learn", since the knock is worse when it first turns cool than after it has been cool for a while.

 

[Quiky One]

You need more fuel the colder it gets. Fuel is less dense and there is more boost. Those combined=more chance for error

Jason

 

[ThikStik]

I dont know how much K it was on that hard pull, and have since found out my Casper's audible gauge seems to be less sensitive. It will work when tapping block, but it no longer sounds on grinding of startup like it used too, and has not sounded at all on any recent K.
Im really suspecting varying octane and agree that boost should be left at 16.
I figure that if octane was held constant, that the increase in volumetric efficiency would be offset by lowered temps and would quell K. Ormond, I agree that ecm should figure the boosts, and that begs the question, does the ecm know what the boost is? Does it get it from the map that is just used to give the disco light bar? Qeustions beget questions!
Thanks for info guys.

 

[QUIP'6']

thin cold air equals lean conditions will cause more boost also!!!!

 

[BRAD_PADGETT]

THILKSTIK- My 2 cents is get a Razor Kit and a TurboTweak chip and do a total retune. I have a hot air at 20 lbs boost zero knock on 93 octane. I can go higher but my insurance company won't allow it. Good luck. Brad