Gasoline grade and tuning

[Tsani]

Queston, and I know it has probably been gone over somewhere. Does it make a difference if you have the bike tuned with 89, and then use 92 or 93 octane fuel? I mean, I know that the octane affects the burn of the fuel, but if the bike is tuned and runs fine on 89, what is the affect if any? Trying to decide weather I should have the bike tuned with a mid grade gas or high test. And if someone can point me out to the thread that dealt with it,Thanks. Not trying to start a war, just get a little understanding.

[Steve Cole]

You can tune for 89 and the end result will be the bike will be down on power from what it could be on 93 fuel. That said we cannot event get 93 in CA any longer, the best we have is 91 and I here that is going to drop to 90 in the near future. So if you not looking for max power, if tuned properly 89 will be fine.

[rbabos]

I'm faced with the same problem at the moment. Was running 94 and went to get gas last night and the pumps were gone. In the middle of company change, but 94 is rare around here. Tired of being a slave to this blend and seriously thinking of tuning it for readily available 91. That way I can go anywhere here with 91.
Steve, generally what's a good starting point from the canned map NO-176 in general  timing reduction to run 91, from the 93 it was likely calibrated for?
Ron

[Steve Cole]

I would take the calibration your running now and drop 3 degrees timing from 50 kPa to 100 kPa at all RPM's. Then work with the timing and DataMaster to get any pinging out. Once that good then go back and tune the fuel side. When complete you can go back over the timing side and may find a few areas you can add a little timing back. Since your dropping down (94 -> 89) it's best to solve the timing first before the fuel side.

[rbabos]

I would take the calibration your running now and drop 3 degrees timing from 50 kPa to 100 kPa at all RPM's. Then work with the timing and DataMaster to get any pinging out. Once that good then go back and tune the fuel side. When complete you can go back over the timing side and may find a few areas you can add a little timing back. Since your dropping down (94 -> 89) it's best to solve the timing first before the fuel side.

Hmmmmmm. With this bastard I don't think I could pull 50 kpa unless it was pulling another bike, uphill, from 30 mph in 6th. Unless I can find a cause for these low kpa numbers, I might need to maybe start at 30 kpa and up. Just a thought.
Ron

[Tsani]

Thanks for the replies. About how much of a power loss are we talking about? A significant loss? If I tune for 89, but use higher, will I gain a bit? Just rying to prepare, what Cali does usually happens else where sooner or later. Thanks.

[Steve Cole]

I have not tuned for 89 then change fuels to see if it helped on a HD motor but we have done it on our car side here. The results were that once tuned and running properly on 89 adding better fuel gave very little power change. We compared tuning on 92 (back in the days when we could get it) to 89. Ran several test on performance and mileage. We quit trying to use MPG and switch to cost per mile and 89 won hands down. We found a drop of about 1- 1.5 mpg with 89 and a drop of 3 - 5% hp compared to 92. Funny thing was when you factor in the cost of the 2 fuels 89 won the cost per mile by a long shot. One would need to look at the cost difference today and see if it still holds true but this testing was all done back in 1994. Remember back when fuel was only $1.00 a gallon and we all thought that was crazy high!

[Tsani]

Thanks Steve. Interesting way to look at it! So maybe about 4 hp. I can live with that. Weather we like it or not, fuel is just going to get worse. I would love to see $1.00 a gallon! But I remember living overseas in europe in 1972, we were paying about 34 cents a g and they were paying over a dollar per liter! Knew it was coming sooner or later. It would be interesting if another "study" was done, especially for stock HDs.

[Steve Cole]

Bad part of it is I was working at a gas station back in the day and our big contest was to see who could get the most fuel into a VW bug. Whoever got the most in that day would get a free lunch for the next day. When you would see a VW roll in everyone ran to get it. I can remember pumping gas when it was only .10 a gallon! Back then to get $2.00 in to a VW was very hard to do on a fill up. That's also back when you use to get full service as part of buying gasoline.