KR in relations to octane

[drifter420]

OK.. I know higher octane on boosted car is required to prevent pre-ignition or pre-detonation ( whichever technical jargon it is ). It is due in part to the compress air being heated up when compressed and so on that the air/fuel charge goes in hot and may pre ignite before the spark. My question is during winter time ( when the hi's are well under 0C ) would it be safe to run lower octane fuel such as mid grade or regular? I'm asking cause of A.) the gas price B.) I'm also thinkin since the ambient air tempreture will be cold so when it gets compressed the tempreture won't be as hot as it is during summer time.. so in theory wouldn't lower octane work just as well if not better since lower octane burns hotter?

[ October 22, 2004, 05:43 PM: Message edited by: rugerman1 ]

 

[The_Jeff]

yup, you can sneak by with lower octane in the winter.

Best if your car has a knock sensor, they mostly do. Try half a tank first so if it knocks bad you can stuff it full of ultra premium.

 

[drifter420]

Yea... I tried a tank actually.. and just emptied it and running ultra 94 octane again. It hasn't been that cold lately.. with hi's of 17C ish.. but I notice that I have lost close to 100km from a full tank. My car does have a knock sensor so it's doing its job it seems. I guess I will try it when winter officially kicks in and see from there. One thing I"m worried about though is that I have heard or rumoured that when your car pulls timing and late detonation occurs.. it causes sludge and carbon build up in your engine ?? Is that true?

 

[mechtech]

Sometimes, due to the cold dense air, you can get more knocking in winter. Cool/cold air is beneficial to producing power, and ultimately raises cyl pressure - I've experienced the onset of spark knock with cold air conditions.

 

[ZR2RANDO]

Most vehicles these days have the air intake set up to pull cool air from outside the warm engine compartment. If you really want warmer intake air you can open up that intake snout to underhood air.

 

[n8wvi]

Wife's car has 10.9:1 compression. Calls for minimum 91 pump octane. Here in MI, premium is typically 93, and that's what it gets in the summer. In winter, I've been mixing, typically 8 gallons 93, 4 gallons 87.

Dave

 

[drifter420]

mixing...wouldn't that give you the same as mid grade?? Or in your case it might be different with 93 supreme.

Mechtech.. yea.. I remember bout denser cooler air making more power.. but I thought it might help since it's colder air.. never considered bout denser air raising compression. *Is that why my car is a pig for gas in winter compared to summer*

I guess no one knows how to build a scantool for OBD II and software so I can read and record the KR reading from actual running is there? That way I can tell for sure in winter and let everyone know. Yes.. I"m cheap.. I can't afford it.. I have 2 cars, insurance, house, insurance, tax, 2 horses, 2 cats and bunch of other things to support.. so if I can nickel and dime.. I will

 

[The_Jeff]

Knock retard seems to be proprietary in the OBDII data stream. But total spark advance is in the "generic" portion, that $65 laptop interfaces can handle.

If your car's data stream has been "cracked" in the aftermarket, you might be in luck.

 

[drifter420]

Sorry.. I don't think mine is cracked.. its generic PCM.. so I guess I'm stuck and have to get the cable?