Other Fuel chart/compression

[EXPERIMENTAL]

does anyone know where there is a chart for suggestions on what octane fuel requirements to run with certain compressions? for example 35cc domes=185psi=91+ octane gas

 

[WaveDemon]

assuming you mean for a yamaha 701 with domed pistons....

straight from the ada website:

 

[EXPERIMENTAL]

thank you

 

[Matt_E]

That chart assumes an otherwise stock engine. A dry pipe can increase octane requirements. A programmable ignition can lower them. An over-propped pump can increase them.

 

[EXPERIMENTAL]

well i have a stock bore (ported) 701, with an MSD, and a low propped engine. another question, what about mixing ratios....example 1 gal of 93 octane + 1 gal of 110 octane = 2 gal or 100 octane????? or something like that.....

 

[Matt_E]

That chart should work for you, then. Your mix should be roughly 101.5

 

[EXPERIMENTAL]

what chart???? i was giving a made up example......just to show people what im looking for

 

[Matt_E]

I was referring to the pics that wavedemon posted. Those numbers should work for you.

 

[EXPERIMENTAL]

gotcha, sorry.... anyone know about the mixing of gas to get certain octanes?

 

[Freakrider]

what kind of compression u running ? some guys run up to 210 compression on 93 with an enhancer and no wide open runs...MSV ( max squish velocity) plays a factor with deto also besides other things mentioned above.

 

[Matt_E]

I personally don't like limiting myself to no wot runs. I run 96 octane on 200psi. To calculate mixed octane, just figure out weighted average.
Example: I mix 3 gallons 100LL with 2 gallons 91.
(3 x 100 plus 2 x 91) / 5

 

[chasingdaylight]

a properly tuned ski with the proper fuel is best but adding 1 or two points on octane on a normal mod ski will not make a power change. If you are right on the thresh hold of being to lean or cylinder tempt too hot, making long wide open runs ect... it can save your motor. Use good fuel and properly tuned ski and rip it. as an elder once told me make good horsepower and don't try to break down molicules. just my 2 cents

most super unleaded here is only 91 maybe 93 if you look how about where you are?

 

[EXPERIMENTAL]

well see im not thinking that higher octane will make my boat run better, i was just thinking about swapping out my 35cc domes for like 33cc or 31cc, just seeing what kind of gas i would have to run. i have a close source on 110 octane turbo blue. i just don't have a lot of spending money for toys, would this be a good mod, instead of a bore? i defiantly considered doing this change over the winter, along with maybe selling my MSD and getting and EPIC ign. unit.

 

[Matt_E]

High compression and oxygenated race fuel can make a HUGE difference.
Heck, I tried out a 50/50 mix of MS109 (oxygenated race fuel) and pump gas to compare it to my usual avgas mix a couple of weeks ago. Compression did not change, but power and throttle response increased dramatically.

 

[EXPERIMENTAL]

yeah, i read that whole thread, i could tell that people liked that ms109, but i just can't find a source near me. im thinking about changing the domes because it will give more power, while still staying stock bore and stroke, i went to BlakcJack 44's just recently and man that was the best move i could have made, i think with a better ignition, higher comp. domes, maybe lighted stock flywheel by #zero, i will be where i want to be as far as power goes. the boat is already freestyle ported and has a mag pump with a SS 12-17 prop, i think im heading the right direction for my freestyle ability.

 

[QJS]

You should be able to run 33cc domes with high octane pump gas with a programmable ignition, we do this all the time our octane rating is worked out differently (one is MON the other is RON) we use 97 RON, do some research and see if your gas matches this and you should be fine.
Chris.

 

[chasingdaylight]

well see im not thinking that higher octane will make my boat run better, i was just thinking about swapping out my 35cc domes for like 33cc or 31cc, just seeing what kind of gas i would have to run. i have a close source on 110 octane turbo blue. i just don't have a lot of spending money for toys, would this be a good mod, instead of a bore? i defiantly considered doing this change over the winter, along with maybe selling my MSD and getting and EPIC ign. unit.

Chuckie at team makes some nice custom 33.something out of 33 that run pump gas and msd very well. you might talk to him about how much more you can get running the proper curve with the epic. I ran really close or at 200 lbs with the old advents, on pump gas..to bad they are not reliable. Do you have a trusted engine builder that you can call..or call Chad at x-scream number is 727-442-7700 and have him ask chuckie

 

[craven]

what about elevation? if you are at sea level your comp. will be higher that if you are at 2000ft. at 700 ft I am around 185 comp. and I run 94 octane, when I go to 2800 ft I am around 165. Just saying that if you are 1000ft +, a 33cc dome will not give you the same comp. as a chart that was made at sea level .
I figure that if you are 185psi or lower, than you can get away with 92 octane, 94 would be better

 

[EXPERIMENTAL]

i don't know my elevation, but i know form a compression tester with 35cc domes i am running about 182-185psi both cylinders, i called my local turbo blue 110 octane dealer and found that they run about $6.25/gal.....is this a good price?

 

[EXPERIMENTAL]

one more question, and i think i am being too paranoid, but i just want to make sure i don't blow up my engine, i am safe by running that 110 octane in my boat right?? even how it is set up now?