Why 91 RON?

[ksquared]

I've been looking through the owner's manual on line in anticipation of taking delivery of my R3T on Saturday. I note that while the engine specifies that the compression ratio is only 8.7/1, the fuel recommendation is for 91 RON? Why, with such a low CR should I need premium fuel.

I've used the search function and found that many of you recommend 89 for this engine, but why wouldn't run just fine on 87? Also, would 87 or 89 have any effect on the heat the engine puts out in traffic?

Everything is stock, the bike is brand new (13 miles) and will remain stock for the foreseeable future.

Thanks for any information you can provide.

 

[tdragger]

This is a common misunderstanding. The 91 RON that you are referring to is how octane is measured in most of the world OTHER than the US. In the US, the measure is (R+M)/2 which is roughly 2 points below the RON method. In other words, 91 RON is equal to our 89 (R+M)/2 mid-grade. Look at the yellow octane rating sticker on the gas pump and you will see the (R+M)/2 method shown.

Only use Premium as a last resort in your new R3T. The Roc runs like garbage on premium with a lot of decel popping and such.

You are right on the money when noting that the R3/R3T is a low compression engine. Being such, higher octane fuel does not have enough time to propagate the flame across the entire volume left by the compression stroke and thus unburnt fuel is released into the exhaust where it ignites late resulting in the popping. Unburnt fuel does not contribute its energy to drive the piston downward which results in loss of efficiency and power.

I run Mid grade most of the time and will occasionally run Regular with no consequence.

 

[ksquared]

Thanks for the insights. It makes sense to me. Seems as if this engine should do just fine on 87. heat might be a little higher, however.

 

[HeR3tic]

I too run mid grade 89 and occasionally 87, when mid grade had been not available, with absolutely no performance degradation. I should try a couple tanks of 87 with these recently installed Mad Dogs to see if the decel pop is quelled. thanks, tdragger for the explanation. With the stock Bologna pipes I had absolutely no decel pop, post Tuneboy remapping. The Mad Dogs have truly made me a believer. A whole lot more giddy-up and went

 

[RocketDaryl]

I don't have the manual in front of me, but I'm certain it says 87 octane is minimum, not 89.

 

[HeR3tic]

I don't have the manual in front of me, but I'm certain it says 87 octane is minimum, not 89.

the manual for the R3 standard does read 89.

 

[TriumPhil]

Knock! Knock!
Who's there?
Bad fuel.
Bad fuel, who?
Badfuelgetcha.

 

[rainman]

i run my r3t on 89 and sometimes on 87 and no problems and in the owners book for the r3t it says 87 r+m/2 unleaded 91 ron unleaded miniumum octane rating

 

[Ygransom]

The R3T only needs 87 octane. It'll run fine on regular even fully loaded 2up and at extened high speeds. Don't waste your money buying the higher grades.

 

[crazyman]

Huh. I've been running 87 Regular since I go the Rocket. I thought the R3T only required 87.
Only recently have I noticed knocking / pinging at some times. Might be time for a valve adjustment. 19k miles in 10 months.