Sam.
New cam! Nice!!!
Intermediate
Joined: Apr 2010
Posts: 47
Likes: 0
From: Central Ohio
Octane prevents fuel from pre-ignition. meaning the compression ignites the air fuel charge not the spark from the plug. on stock, 8-ish-1 compression, 87 octane fuel is sufficient. also a raise in octane on a stock engine will not give a raise in performance. as you raise compression the fuel wants to ignite b4 the plug fires causing the "ping" that can burn holes in pistons, damage bearings, rods, etc.On a high compression engine raising the fuel octane prevents this pre-ignition, or "ping", also allowing for timing advance for performance gains.
Any time you raise the stock compression ratio in an engine you need to run premium fuel, no ifs, ands, or buts....
Any time you raise the stock compression ratio in an engine you need to run premium fuel, no ifs, ands, or buts....
Tourer
Joined: Apr 2010
Posts: 293
Likes: 7
Octane prevents fuel from pre-ignition. meaning the compression ignites the air fuel charge not the spark from the plug. on stock, 8-ish-1 compression, 87 octane fuel is sufficient. also a raise in octane on a stock engine will not give a raise in performance. as you raise compression the fuel wants to ignite b4 the plug fires causing the "ping" that can burn holes in pistons, damage bearings, rods, etc.On a high compression engine raising the fuel octane prevents this pre-ignition, or "ping", also allowing for timing advance for performance gains.
Any time you raise the stock compression ratio in an engine you need to run premium fuel, no ifs, ands, or buts....
Any time you raise the stock compression ratio in an engine you need to run premium fuel, no ifs, ands, or buts....
There is some truth in areas of your post, but some not quite as accurate as it might be.
Just in general, octane is a rating system. It refers to the chemical structure of the fuel. Put simply, the tighter the bonds, the less likely they are to come apart. So you can exert more pressure on the fuel before it suffers degradation.
Pinging is not only caused by pre-ignition.
Raising compression does not necessarily mandate higher octane. Could not be more wrong. It may, but not necessarily so. There are many scenarios here. Timing, VE, spark plug set-up, for starters.
Remember, not knowing something does not mean it is not so. It merely means that you do not know.
Stellar HDF Member
Joined: Jan 2007
Posts: 3,447
Likes: 163
From: Northern VA
Finished my EV27 install a couple weeks ago and am happy with the results so far. Piper, did you tweak the carb/ignition any after the EV27 install or are you riding the bike "as is"?
Intermediate
Joined: Apr 2010
Posts: 47
Likes: 0
From: Central Ohio
A : never said pinging was only caused by pre-ignition
B: as a pretty handy shade-tree mechanic i did substantial reading to substantiate my post &....your right, you dont need to raise the octane rating in the fuel when compression is raised....however, it seems that either extensive head work, timing retard, higher revs, enriching the fuel mixture, or a host of other things need to take place to prevent this from happening (several hindering performance, fuel economy & negate the use of higher compression pistons to begin with in my opinion) so it would seem that a good rule of thumb would be...if u raise the compression of a stock engine to ohhh say...10:1 it would be a very good idea AND cheap insurance to run premium fuel. If you still experience ping, knock, pre-ignition or whatever u wanna call it, you may want to venture further.
C: I was only trying to help someone
B: as a pretty handy shade-tree mechanic i did substantial reading to substantiate my post &....your right, you dont need to raise the octane rating in the fuel when compression is raised....however, it seems that either extensive head work, timing retard, higher revs, enriching the fuel mixture, or a host of other things need to take place to prevent this from happening (several hindering performance, fuel economy & negate the use of higher compression pistons to begin with in my opinion) so it would seem that a good rule of thumb would be...if u raise the compression of a stock engine to ohhh say...10:1 it would be a very good idea AND cheap insurance to run premium fuel. If you still experience ping, knock, pre-ignition or whatever u wanna call it, you may want to venture further.
C: I was only trying to help someone
Tourer
Joined: Apr 2010
Posts: 293
Likes: 7
A : never said pinging was only caused by pre-ignition
B: as a pretty handy shade-tree mechanic i did substantial reading to substantiate my post &....your right, you dont need to raise the octane rating in the fuel when compression is raised....however, it seems that either extensive head work, timing retard, higher revs, enriching the fuel mixture, or a host of other things need to take place to prevent this from happening (several hindering performance, fuel economy & negate the use of higher compression pistons to begin with in my opinion) so it would seem that a good rule of thumb would be...if u raise the compression of a stock engine to ohhh say...10:1 it would be a very good idea AND cheap insurance to run premium fuel. If you still experience ping, knock, pre-ignition or whatever u wanna call it, you may want to venture further.
C: I was only trying to help someone
B: as a pretty handy shade-tree mechanic i did substantial reading to substantiate my post &....your right, you dont need to raise the octane rating in the fuel when compression is raised....however, it seems that either extensive head work, timing retard, higher revs, enriching the fuel mixture, or a host of other things need to take place to prevent this from happening (several hindering performance, fuel economy & negate the use of higher compression pistons to begin with in my opinion) so it would seem that a good rule of thumb would be...if u raise the compression of a stock engine to ohhh say...10:1 it would be a very good idea AND cheap insurance to run premium fuel. If you still experience ping, knock, pre-ignition or whatever u wanna call it, you may want to venture further.
C: I was only trying to help someone
B. It was already clear that your post is merely internet research, and no actual experience. And I really do not need you to tell me I am right.
C, Then offer advice from proven experience only, not from web browsing.
Elite HDF Member
Joined: Sep 2007
Posts: 4,468
Likes: 12
From: Bluffton, South Carolina
C, Then offer advice from proven experience only, not from web browsing.[/QUOTE]
Iron geaar, Seeing as you brought this subject up, why don't you post your resume. That way all will know your "experience"?????
Iron geaar, Seeing as you brought this subject up, why don't you post your resume. That way all will know your "experience"?????
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Southpaw Super Glide: A Left-Hand-Drive 1979 Harley FXE Built to Fit the Rider
Verdad Gallardo
Road Master
Joined: Jan 2006
Posts: 1,192
Likes: 4
From: Columbus, OH
I'ts a great cam for my bike, with a S&S super E and a SE ignition module, I have eliminated all the coughing and spitting it used to do and it runs strong. No pinging either but I run 89 to 91 octain.
Thread
Thread Starter
Forum
Replies
Last Post
