Harleys and premium gas

Just more hardly BS. At one time, many, many years ago, they were the bad boys. Now they are just shiny antiques. Usually when you come upon a herd of them on the side of the road somewhere, they ain't there to BS, they are waiting on their over priced POS to cool off, so that they can continue on their "look at me" parade. I've been told some of the newer ones actually shut the rear cylinder off when caught in traffic and overheating. And yes, I have a 06 sportster sitting in my barn growing dust and cob webs. I'd love to sell it, but can't see getting about a dime on the dollar! Ha!
 
R3Tex said:
I run premium in both my Rocket and HD. The little bit of extra $ on 5 gals of gas isn't worth pissing and moaning about IMO...if it helps great, it can't hurt
Click to expand...

How do you know what your getting.. I don't know anyone that buys premium gas these days, at least in my neck of the woods. I'd rather run fresh 89 than stale 91.. JMO
 
My Bro-in-law drives a gas tanker, and delivers to many gas stations. According to him it all comes out of the same tank at the port. Each individual company specifies which crap they want dumped in. When he takes on a load for company "A", he dumps this crap in, for company "B" it gets something a little different dumped in. But it all starts out the same with no additives.
 
First, some of you keep comparing static compression ratio with dynamic compression ratio. Static compression ration is based on cylinder and chamber displacement at TDC and BDC, Dynamic compression ratio is based on cylinder and chamber volumes when the exhaust valve closes. This plays a very important part in how much cylinder pressure is actually produced.

This means that an engine with 8.1:1 static compression ratio can actually have a dynamic compression ratio higher than that of an engine with a 10:1 static compression ratio.

While dynamic compression ratio is a better indication of ocane requirements, it still does not account for very good or very poor cylinder filling due to strong intake and exhaust harmonics at different parts of the operating range.



Second, ethanol causes problems due to the fact that it is an oxygenate that causes rust and corrosion in parts that are not coated or treated correctly - like motorcycle, chain saw, and lawnmower fuel systems.

E10 (9-10% ethanol) can actually make a very slight increase in output if you are pushing the limits of detonation. Stock R3s are not.

I hope this helps.
-Wayne
 
 
Most stock R3s run well on 89 PON (USA), and 91 RON (Europe) just like the manual states. On the dyno, I normally see 1-1.5 hp more (MAXIMUM) at peak, but less response at lower revs - when using 93 PON/ 98 RON fuels in the Winter, and little to no difference in the Summer here in the HUMID Deep South.

Remember that Summer and Winter fuel blends differ considerably. Winter blends contain considerably amounts of Butane - high in octane and easily evaporated, but low in output.
 
Now for the real problem with determining octane requirements... CARBON.

Below I have loaded a photo of two R3 pistons. One is clean, and the other is very typical of what I see on stock pistons - lots of carbon. The R3 chamber has poor pressure recovery and the piston design does not get close enough to the head to have good squish velocity. As a result, the pistons and chambers tend to develop carbon deposits. It is these carbon deposits and poor squish velocity that cause one engine to need higher octane than another.

Gummout makes a product called Regane that has 10 times (or more) the detergents as other comparable products. This helps to clean pistons, chambers, and valves when used in the fuel with each oil change.
 
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