Hi All,

I recently picked up my new 2002 HD with the supercharger similar to the one in the Lightning. I have a question for you Supercharge pros. What are the ill effects of using 87 octane vs 91 as the manual recommends? A buddy of mine that use to own an auto repair shop claims that using 87 octane would not harm the internals of the engine or the performance. Can anyone here shed some light on this?

Thanks

 

Lightning Boy sees fried spark plugs, holed pistons, among many other possible bad things that are liable to happen in the future useing 87 octain fuel.

 

Your mechanic buddy obviously doesn't understand how octane, boost and knock inter-relate.

Find a new buddy for advice.

87 has no business in any engine running boost.

 

Thanks for the response. I figured that did not sound right.

 

Hopefully you'll never let that moron touch your engine.

 

lol stick with super !!! lol 4D hahaaa or mine at that!


Dave

 

91 is marginal

87 is out of the question

Andy

 

Use 87 octane and you will be like your Hardly-Davidson bike-riding bretheren; broken down on the side of the road with oil leaking out everywhere.

 

What's that pinging noise????

 

a supercharger compresses the air before it enters the cylinder. Because PV=nRT, the temperature of the gas must increase. Thus, you could have spontaneous ignition of the fuel ("knocking") before the spark plug can fire. The flashpoint of 91 octane gas is higher than 87 octance because it is "purer," so less spontaneous ignition. Only run 91, and 93 if you can get it.

 

I understand what you're saying here, but could you further explain the PV=nRT

 

It is the ideal gas law:

PV=nRT

(pressure)(volume) = (moles)(constant)(temp)