Timing for lower octane?

jimberg · 08-04-2006, 12:30 PM

The cost difference betwen 87 and 92 ranges from 14 to 22 cents here in Minnesota. The interesting thing is that that spread always seems to be there. Even when gas was 1.20 a gallon for 87, premium was 1.34 to 1.42. Taking the worse case, you would be spending 18% more to get premium. Gas just hit 3.20 a gallon for 87 yesterday. Premium is now 3.42. Now it's only 7% more to get premium. It's a better deal. If you emptied your tank once a week for an entire year, that's only an extra $176 for the year or about $15 a month. Do you really want to de-tune your fun for $15 extra a month?

We can also purchase non-oxygenated premium here in Minnesota. That means it's pure gasoline. I get at least 10% better gas mileage when I use it than when I use the oxygenated crap. It's actually cheaper for me to use than if I detuned my car to use 87.

Vamp89, Why is your timing set so high? Have you put your car on a dyno to confirm that you get the most average HP at that much advance?

Dark_5.0 · 08-05-2006, 07:52 AM

I made 301 RWHP and 330 RWTQ on 87 octane with no detonation at 14 degrees of initial timing.

jimberg · 08-05-2006, 10:15 AM

No detonation on a DynoJet? If that's what you mean, don't forget that a DynoJet doesn't properly load the engine to test for detonation. That's what Mustang Dynos are good for, however.

Dark_5.0 · 08-05-2006, 12:22 PM

Well considering I raced the hell out of that engine on 87 octane and never had an issue one in 3 years I would say it was running fine. Mid 12's @108 mph. It would start to detonate at 16 degrees of initial timing with 87 octane.

I ran 93 octane and bumped the timing as high as 18 degrees initial but it ran the fastest at 14 degrees and 87 octane.

I tweeked it out over the course of a couple hundred 1/4 mile runs.

It could have something to do with the crappy air where I am at.

3000-5700 ft density altitude.

Vamp89 · 08-05-2006, 06:45 PM

She run better set that high.

jimberg · 08-06-2006, 12:30 PM

Quote:

Originally Posted by Dark_5.0

It could have something to do with the crappy air where I am at.

3000-5700 ft density altitude.

That makes sense.

08-04-2006, 12:30 PM	#1
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	Re: Timing for lower octane? The cost difference betwen 87 and 92 ranges from 14 to 22 cents here in Minnesota. The interesting thing is that that spread always seems to be there. Even when gas was 1.20 a gallon for 87, premium was 1.34 to 1.42. Taking the worse case, you would be spending 18% more to get premium. Gas just hit 3.20 a gallon for 87 yesterday. Premium is now 3.42. Now it's only 7% more to get premium. It's a better deal. If you emptied your tank once a week for an entire year, that's only an extra $176 for the year or about $15 a month. Do you really want to de-tune your fun for $15 extra a month? We can also purchase non-oxygenated premium here in Minnesota. That means it's pure gasoline. I get at least 10% better gas mileage when I use it than when I use the oxygenated crap. It's actually cheaper for me to use than if I detuned my car to use 87. Vamp89, Why is your timing set so high? Have you put your car on a dyno to confirm that you get the most average HP at that much advance? __________________ 351W 89 Mustang GT Convertible

08-05-2006, 07:52 AM	#2
Dark_5.0 Registered Member Join Date: Apr 2001 Location: Staging lane Posts: 4,337	Re: Timing for lower octane? I made 301 RWHP and 330 RWTQ on 87 octane with no detonation at 14 degrees of initial timing. __________________ 92' LX-Big brakes, Lots and lots of suspension, GT40X heads, Ported cobra intake, stock cam, Vortech SC trim. 00' Lightning-Stock 88'CRX-13 second ego killer

08-05-2006, 10:15 AM	#3
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	Re: Timing for lower octane? No detonation on a DynoJet? If that's what you mean, don't forget that a DynoJet doesn't properly load the engine to test for detonation. That's what Mustang Dynos are good for, however. __________________ 351W 89 Mustang GT Convertible

08-05-2006, 12:22 PM	#4
Dark_5.0 Registered Member Join Date: Apr 2001 Location: Staging lane Posts: 4,337	Re: Timing for lower octane? Well considering I raced the hell out of that engine on 87 octane and never had an issue one in 3 years I would say it was running fine. Mid 12's @108 mph. It would start to detonate at 16 degrees of initial timing with 87 octane. I ran 93 octane and bumped the timing as high as 18 degrees initial but it ran the fastest at 14 degrees and 87 octane. I tweeked it out over the course of a couple hundred 1/4 mile runs. It could have something to do with the crappy air where I am at. 3000-5700 ft density altitude. __________________ 92' LX-Big brakes, Lots and lots of suspension, GT40X heads, Ported cobra intake, stock cam, Vortech SC trim. 00' Lightning-Stock 88'CRX-13 second ego killer

08-05-2006, 06:45 PM	#5
Vamp89 Registered Member Join Date: Mar 2006 Location: Fort Wayne, Indiana Posts: 49	Re: Timing for lower octane? She run better set that high. __________________

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