Honda CBR 250 Forum banner

21 - 30 of 30 Posts

·
Super Moderator
Joined
·
6,934 Posts

·
Registered
Joined
·
159 Posts
I'm with the others. The 250r does not have a high compression engine. I'm betting that the high octane was 0 or very low ethanol. I've been using 10% ethanol fuel for most of the time since '13. The only thing I add is some fuel stabilizer in the winter. But, recently I tried a couple of tanks of non-ethanol and what a difference! Yep, 87 octane. On one tank I drove about 80 miles on the highway and really blew it out. I think it was once of the best things I did for my weebee. I have one gas station within about 10 miles that offers non-ethanol and I will be filling up there whenever possible.
 

·
Registered
Joined
·
202 Posts
Discussion Starter #23
So is the higher octane gas you're using now pure gas with no ethanol?
I'm not entirely sure. I bought it at a Sunoco station. Only one local Sunoco is listed on that site which is close by but not the one I went to. However, I would think all Sunocos have the same gas sold at their locations which makes me think it was. The previous tank was filled with Exxon gas which was listening on the other site as being top tier gas.

As a goal I'm going to try and get the same gas, 93 octane, from the same Sunoco station for a few tanks. Then I'm going to get the 87 octane for a bit again from the same station. Then I will let you know what I think.

I wish I could have some sort of blind test with a friend filling up my tank with one or the other.
 

·
Super Moderator
Joined
·
2,039 Posts
I wish I could have some sort of blind test with a friend filling up my tank with one or the other.


I love it!

Next comes a plan for a double blind test. Does your friend ride a CBR250?
 
  • Like
Reactions: shisoshin

·
Registered
Joined
·
5 Posts
In Aus, I use Shell V-Power in anything automotive which has a octane of 98. This fuel has carbon detergents 7x the recommended amount to Aus standards and will help prevent carbon build up in the chamber whether it be around valves or the top of the piston. Plus it ignites more reliably without detonation in high reving engines. I used it in my Falcon XR6 and noticed a big difference in smooth acceleration and also fixed any misses in the higher end rev.
I would also recommend resetting your ecu, to unlearn any previous driving/riding on lesser fuels so it advances or retards timing more efficiently.
 

·
Registered
Joined
·
1,917 Posts
If 92 octane is giving you more power with a CBR you may have deposits in the combustion chamber that are bumping the compression ratio.

Typically, higher octane than required to just barely ward off detonation will make less power - not more.
 

·
Registered
Joined
·
34 Posts
Also carbon-deposits retain heat, leading to detonation even without significant increase in compression.

Yes, bike was designed and ECU programmed with lowest-octane in mind. This is good durability measure from manufacturer in case owner gets crappy gas in boondocks on super-hot day. Long time ago, I wrote an article on what octane really is: Porsche 951 RacerX - What's Octane

I noticed it's been swiped and copied without credit, typos and all! :)>

Note that unless your engine has been designed and tuned with high-octane fuel in mind (race-bike), it won't make any more power than stock. To extract higher power possible from high-octane fuels, you'll have to install higher-compression pistons and increase ignition-advance. Which precludes you from ever using lower-octane fuels again. I have turbo race-car that absolutely, positively requires VP100 race-fuel due to turbo boost-level. If I ran 99-octane gas, it would self-destruct engine from detonation & knock within 2-3 seconds of going full-throttle.

So, IF your bike can run on low-octane fuel, using higher-octane will result in no extra power. There's been tonnes of dyno-tests that has proven this; in some cases, high-octane fuel actually decreases power. Unless you've got maintenance issues like jkv mentioned.

Additional reading:
Octane Booster Comparison - actual testing of OTC mixes from Fast Fours Mag
Homebrew Octane Boosters - way higher than pump gas
F1 Rocket Fuel FAQ - based upon Maclaren-Honda's F1 cars 1986-1988



Dyno - Octane vs. Horsepower - Separating fact from myth in the debate over which fuel makes more power - NASA Speed News Magazine (some misinformation, but good dyno-testing shows most power on 87-oct)
Dyno - Fuel Rating - Octane Comparison - Dyno Tests Graphs - Hot Rod Magazine (2% increase required 114-octane, and also needs adjusting ignition-timing. No one's butt is going to notice 2% difference, but your wallet will notice 400% increase in fuel-cost).
 
21 - 30 of 30 Posts
Top