Topic: does ethanol fuel make engines ping? or is it lack of octane ?

[grcamna2]

I have a piston in my engine that's about 10.5:1 and stock was 9.5:1.I travel up high altitude mountain roads sometimes and get a lot of pinging and I don't use octane booster. Anybody have similar experiences ?

[RAFster122s]

As you go up in altitude you see less air density and the mix changes, so, yes octane plays a factor. The ethanol serves to increase the octane a little.  But the burn rate slows as octane goes up, this is needed. It is not uncommon to have no pinging at lower altitudes only to see it appear in hot weather or at higher altitude.

Only solution is to increase the octane. You may have to run premium fuel and or make adjustment to the timing
I would not expect only a 1 point increase to have that much of an impact,  but other changes may have contributed.

[Retro Rocket]

Only solution is to increase the octane. You may have to run premium fuel and or make adjustment to the timing
I would not expect only a 1 point increase to have that much of an impact,  but other changes may have contributed.

Retard the timing a touch....

[scottly]

Retard the timing a notch to reduce ping. Higher altitudes should reduce pinging, due to the lower density. What bike are we talking about?

[Retro Rocket]

Retard the timing a notch to reduce ping. Higher altitudes should reduce pinging, due to the lower density. What bike are we talking about?

What you talking about Willis...?     





Fixed that for me...

[333]

Regardless of the bike, consistency in what gas you use is important. And once you are sure the gas in your tank is uniform, do a tune up.  A motor without the benefit of a computer needs to be tuned to the gas it uses. Then, if you travel to higher elevations frequently, you might try setting the timing a bit on the retarded side.  This should reduce the amount of pre-detonation.

[grcamna2]

The bike is a small Honda CB125 single w/ a 5mm overbore high compression piston and the cylinder head hasn't been opened up to the new larger bore size yet so I believe the compression is still(I shaved the crown a bit flatter)too high.I retarded the timing quite a bit;this bike has factory CDi ign. I tried some 100 octane airplane fuel in it.. 1/2 a gal. mixed w/ 2 gals. of 91 oct. ethanol pump gas and it seemed to help a bit more than octane booster(which fouls plugs sometimes).

[333]

I'm not sure what you expect out of that bike.  But just using 91 straight from the pump gas is too much octane for a 125.  I've had a couple of those bikes, although mine were older 6 volt units with points.  But they are gutless.  People wouldn't believe that I could get mine to 70.  I had to be going down hill, tucked in to a full Rollie Free to do it, but I could do it.

I'd suggest putting in 87, and taking a bigger bike to the mountains.