Octane Question

[Ross]

OK, here's a strange one, but I'm good at that. I know that our cars are designed to run on premium gas, and that using lower octane is bad for the engine. Let's say we have an emergency situation, like the hellacious attempted evacuation of the Houston area last year during Hurricane Rita. Gas is in short supply, and if you can find it, only the lowest octane is available.
Is it possible to have a chip or programmer loaded with a special tune to allow for using 87 or 89 octane? Obviously performance would suffer, but in a case like this all you need is for the engine to run and not be messed up by the experience.
For those of us who have X Cal's or similar programmers, could someone like Lidio or Dennis come up with a program to allow the use of whatever happened to be available?
Just a thought as hurricane season approaches.

[Motorhead350]

I don't think that would hurt the car if you only did it once, doing it for it's life is another. I accidently put in a lower octane then diesel a few months back and my car is running better then ever..... after 8 new spark plugs and a fuel filter. :D

[Ross]

I think I remember that kerosene thread. :nono:

[Motorhead350]

It was an honest mistake my friend and you know what I found out it actually cleaned the engine out so I did my own self tune up! I'll remember to use it again at 200,000 miles. :P

[Vortech347]

I think ford programs the cars to run on minimum 87. They recomend 91+ for best performance. The car will run fine. I don't have the owners manual infront of me but I think its in there. Thats why its a requirement with the Tuners you run 91+. They advance the timing to take advantage of the better octane.

With your car having a tune. Put it back to stock, throw crap gas in and you're good to go.

[JohnE]

You can run regular gas with a premium tune, BUT be light on the throttle always. Pull up on the throttle if you here detonation. It's best to have an alternate tune for regular fuel, which retards the spark under medium and higher loads.

I made a regular tune when I left for Rita on my flip chip. Was lucky enough not to need it. I've gotten bad gas once before too, I think the tanker mixed up when they filled the station. I just put up with less power at reduced timing for a tank.


John

[Paul T. Casey]

You can load a "bad gas" program if you have a multiple place chip. I believe Smokie has one for sure.

[Smokie]

Yes I have a bad gas program, it works very well, Lidio loaded it in my SCT 9100 when I purchased S/C.

It provides peace of mind against damage, you may not always hear the knocking during bad weather conditions like heavy wind and rain.

[MENINBLK]

There is only one way of knowing of you can run 87 octane in our engines.
Anyone who has blueprinted our stock engine internals will know.

There is something called a Quench Area.
http://chevyhiperformance.com/techarticles/94138/
If our engines have a large quench area, you should not run 87 octane
even with an 87 octane tune.
This is because our engine cannot physically burn 87 octane.

[JMan]

There is only one way of knowing of you can run 87 octane in our engines.
Anyone who has blueprinted our stock engine internals will know.

There is something called a Quench Area.
http://chevyhiperformance.com/techarticles/94138/
If our engines have a large quench area, you should not run 87 octane
even with an 87 octane tune.
This is because our engine cannot physically burn 87 octane.

Great article!

I'm not an engine builder, but I believe the MM head is an open chamber, hemispherical, head design with very little quench. Dang, I hate to use the "H" word but it is much more true of the Cobra (MM) head than the modern Chrysler Marketing "Hemi".

The intake ports are unusally shaped to accomplish the swirl of the incoming fuel and air charge while also breathing thoroughly at higher revs. That's where the DOHC engines get their power and efficiency. That leads me to believe these engines would work well on lower octane fuels with the correct timing controls/constraints. But, the higher octane timing curves yield greatly more HP.

How this pertains to suitable fuel/octane ratings, I do not know. I'm certain someone with more engine-specific knowledge will chime in here. Not trying to stir anything up . . .

J