Is this normal?

[ducpainter]

Ok I'll start putting 87 and see how it goes .. how abt on my 12 1100evo? High or low octane fuel ??

I'd try 87...if it pings go to 89...and if necessary go up until it stops pinging. As long as you know how to identify pinging when you hear it.

The evo has higher compression than your older bike.

[desmodoktor]

I'd try 87...if it pings go to 89...and if necessary go up until it stops pinging. As long as you know how to identify pinging when you hear it.

The evo has higher compression than your older bike.

And how do we identify pinging ? 

[He Man]

You would hear pinging (more like a tick) inside your motor, because the fuel is detonating before the sparkplug fires. it kinda sounds like a tick during idle and you get really unsmooth response from the motor the higher rpms you go (since theres less tiem for burning the fuel).  if you dont hear a tick during idle, it might only occur at higher rpms.


I run 89 on my EVO1100. Ive also ran 87, it doesnt seem as smooth, but i havent really put that many miles on my new motor to say absolutely. And as DP said, the 1100 single spark evo is a bit higher compression.

the DS1000 motor runs 10:1
the SS1100 motor runs 11.3:1
the 1098 motor runs 12.5:1

[brad black]

often there may be no performance improvement with higher octane fuel, but you may get better fuel economy for instance.  or it may be smoother.

[ducpainter]

And how do we identify pinging ? 

The easiest way is to grab a handful of throttle in a high gear going up a hill.

You'll hear what sounds like marbles in the motor.

What Brad says about fuel economy and smoothness is very valid and would be good reasons to use higher octane fuel.

I just don't believe in throwing octane at a motor for no reason, and really don't think you need 93 under any circumstance.

[scaramanga]

your evo with 11.3/1 comp ratio needs high octane fuel. listening for pinging under load is a good way to tell if your fuel's octane rating is high enough but the last thing you want is to be stuck driving up hill on a hot day and listening to your gorgeous bike complain. low octane + high compression+lean condition=pre-ignition. pre-ignition=pitted piston tops, very worst case....melt down.
evo=93 (buy it from a busy gas station, you don't want stale gas)
dark= don't matter

are you using good quality oil and the proper weight? what do the plugs look like?

btw, don't panic about any of this

[He Man]

That doesnt make sense.

If 87 is good for 10:1
and 93 is required for 11.3:1
then the 1098 should use the equivalent of 98 octane. which doesnt exist.
1098 will is noticeably smoother on 93, 87 blows chunks. 89 is meh.

You should use what prevents pinging and gives you the best fuel economy and optimal smoothness. If 89 fits the bill then there is no need for 93.

[Speeddog]

That mathematically doesnt make sense.

If 87 is good for 10:1
and 93 is required for 11.3:1
then the 1098 should use the equivalent of 98 octane. which doesnt exist.
1098 will is noticeably smoother on 93, 87 blows chunks. 89 is meh.

You should use what prevents pinging and gives you the best fuel economy and optimal smoothness. If 89 fits the bill then there is no need for 93.

You can't compare compression ratios between 2-valve and 4-valve engines.
The combustion chambers are radically different.

[He Man]

You're right,Just looked it up. Compression ratio is just part of the story. The design of the combustion chamber and the when the valves open up plays a bigger role.

So throw that out the window, octane is still the resistance to knocking. You should run what makes your motor run smooth and has the best MPG and not by a blanket statement of 11.3 needs 93.

[desmodoktor]

are you using good quality oil and the proper weight? what do the plugs look like?

btw, don't panic about any of this

Using MOTUL 7100 10W40 every 2000miles .
the farthest to the left is the one from the horizontal cylinder (the pics that i posted before) i dont like the way it looks . looks like there is oil there...
the cylinder is fine (clean) no signs of bad piston-rings. one of the o-rings that are between the cylinder and the valves was smashed (the smallest o-ring) im going to replace all of them.
also the same cylinder backfires from the intake when i flick the throttle fast. it went away last season from adjusting the throttle bodies...

[scaramanga]

You're right,Just looked it up. Compression ratio is just part of the story. The design of the combustion chamber and the when the valves open up plays a bigger role.

So throw that out the window, octane is still the resistance to knocking. You should run what makes your motor run smooth and has the best MPG and not by a blanket statement of 11.3 needs 93.

i thought he was just looking for some advice and not a course on combustion swirl,valve angles and spark advance not to mention the other 50 things that affect pre-ignition.
I never meant for it to be a blanket statement only that HIS bike with a high comp ratio and being in a lean condition would be better served with a higher octane fuel. there was no bad advice given, just trying to help.

your plugs will give everyone alot of info, see if you can get some better shots like your previous photos which btw where very good.

[scaramanga]

this is a piston from an old chevy race engine of mine. the pitting around the bottom edge was caused by detonation.