Octane for Chad’s maps?

Tom

New Member
After looking in the manual today, I saw they recommend 91 octane. I’ve been using 93 lately, and I know this will produce less power if timing isnt tuned for it.

Seeing as how our bikes have no knock sensor, and thus doesnt pull timing on detonation, I was just wondering what the recommended octane was for Chad’s map.
 

green_bread

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I have run 91 and 93 both (depending on availability around the tracks Im at) and havent really noticed any difference, one way or the other. Im sure if you put the bike on the dyno, back to back, there would be a small percentage of difference. Im 100% willing to bet that small percentage isnt going to make any difference, at all, to someone with my, your, or anyone else doing track days/racing at this level's abilities. ;-)
 

John390

New Member
its 12.6:1 compression ratio and runs hot. That says to run high octane fuel to me.

I'd be open to hearing facts to refute that.

Either way, given the fuel economy of these engines and the small tank, its not a hurt to the wallet to fill them up. :)

also, I'd be curious to know if anyone has done any real research towards ethanol blended fuels and thier use on these bikes? many cars don''t do as well on ethanol blends as you might think
 

Tom

New Member
We all mod our bikes to get the most power out of them. If something as simple as saving a few bucks and using 91 vs 93 equates to more power, then why not? The reason I mention a lack of knock sensor is because we will have no idea if the motor is suffering from pre-detonation, until we open it up and see all those pretty little pits everywhere. If the ECU doesnt add or pull timing based on knock, it's difficult to know which octane is optimized to the static timing values on the tune. Knowing the PCV doesnt control closed loop areas of the map, I can surmise that 91 octane would be the minimum for the timing values within those cells.

I know unnecessary octane kills power, back when I was getting a tune for race fuel on my MR2, the baseline was about 20 HP shy of what the pump gas map produced earlier in the day. I dont still have the maps to prove it, but a quick google search will yield articles that show similar results:
https://nasaspeed.news/tech/engine/...-the-debate-over-which-fuel-makes-more-power/

Granted, my MR2 made 357hp on pump, and the car in that article made 155. The engines in cars are much larger, and the differences in power output for over octane may be much larger than our small displacement bikes; even a 1 horsepower difference is noticeable on such a light weight vehicle.

Also, John, to answer your question, blended fuel that contains 10% or less ethanol has roughly the same stoichiometric ratio as straight gas. The problem you see on most newer cars is due to the fact they have direct injection. When alcohol reaches the hot cylinder walls, it vaporizes at a very high velocity. Enough to force atomized alcohol and oil from the cylinder walls back through the intake valves, before they get a chance to close. This even happens on methanol injection motors that use traditional intake port injection. The problem with direct injection is that there is no fuel flowing back into the cylinder, over the intake valves, to act as a solvent for the freshly deposited sludge. Overtime it builds to a point the motor looses power and begins to have problems. There was a guy on the Audi forums that ran dyno tests every 5k or 10k miles on his rs4, and the results were astounding, each dyno showed a significant loss until the car made about the same power as a Honda accord. I cant find the thread, but here is a similar one with a before and after dyno of another Audi's intake cleaning:

https://www.audizine.com/forum/show...th-Dyno-B7-Audi-RS4-by-rs4max-on-QuattroWorld
 
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John390

New Member
great stuff gents!

I am more of a turbo 4 cylinder tuner, but I have some experience with high compression n/a 4 cylinders, albeit multi carb setups not fi.

Fully agree about the DI gas engines needing to stay clean. I have two of them, one being a Mazdaspeed 6 and the other a VW Alltrack.

As for alcohol blended fuels, I am not as worried about stoich, but about actual energy per unit of fuel. Alcohols have approx 60% of the BTU's of gasoline. I have noticed this on port injected turbo engines, both on the dyno and on the street, as well as real time datalogging and tuning. You can see the maps being changed as you drive, and you can see your AFR change from where you had a perfect map before. I have tuned my car tuned for both power and fuel economy and so I had my cruise and off idle very lean. Just rich enough to not misfire or act poorly in traffic. With E10 fuel, once the E0 was out of the fuel lines and injectors, you could feel the engine stumble a bit, and it didnt get better until I added a few percentages of fuel in those areas. I have my maps on that car set to stay in closed loop a bit longer because it gets great mileage like that and went thru local dyno based emissions testing exceedingly well! not so much in open loop, no matter what I did. I got many other cars thru by putting them in closed loop too, despite what everyone told me.

Also, on all of our turbo cars(we currently have 3) they all pull less timing and can tolerate more boost at higher ambient air temps when running quality E0 fuel VS the same octane rated E10.

However, like I said I am new to the KTM 390 platform and a bit new to small high compression engines.
 
My maps are built on 93 pump fuel @ e10 here.
Do you have any built on 91 pump fuel? I was thinking of getting a power commander from you guys cause I hear your maps are worth their weight in gold, but there's only 1 gas station I've found so far within an hour of me that has 93 octane gas and it's way out of the way

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cjwell

Supporting Vendor
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92/93 is what we have 91 will make no difference. You can pull a degree of timing out if concerned.

Do you have any built on 91 pump fuel? I was thinking of getting a power commander from you guys cause I hear your maps are worth their weight in gold, but there's only 1 gas station I've found so far within an hour of me that has 93 octane gas and it's way out of the way

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92/93 is what we have 91 will make no difference. You can pull a degree of timing out if concerned.
Pull a degree of timing out? What would that imply doing and how would I do that?

Sorry I'm sure it's a simple answer. I haven't really had much opportunity to learn about this stuff but I'm always trying to learn

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cjwell

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In the PCV, I can do it for you.

Pull a degree of timing out? What would that imply doing and how would I do that?

Sorry I'm sure it's a simple answer. I haven't really had much opportunity to learn about this stuff but I'm always trying to learn

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Zigoron

New Member
Do your maps work with 91RON fuel.

Hey Chad, I was wondering whether your maps work with 91RON(87 US Octane I guess) fuel which is the only fuel available widely in India. I have been running my 2017 RC390 on 91RON from day 1. We do not have the recommended 95RON here but we do have 97RON but thats very rare only around 3-4 in every state.
 
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