Leaded gas

Lead has always been a very inexpensive way to raise the RON and especially the MON octane rating of a fuel. It also works really well at giving the tuner an extra margin of safety when tuning close to the edge due to it's chemical properties and the way it influences active radical formation. If you guys are interested I'll be happy to bore you to death with some of the details :)

For late model engines (2 & 4 stroke ) lead serves no other useful purpose other than raising octane . Stories of it saving valves, running cooler, or making bottom ends last longer is total bunk when talking about the engines built in the last 15 years.

The only way lead can make an engine run cooler is if it were detonating without lead and the octane increase WITH lead stopped the detonation. Any fuel that satisfied the initial octane requirement and stopped the detonation would have the same effect on temps wether it had lead or not. In other words, adding lead to the fuel of an engine that is not detonating will not change the combustion chamber temps to any measurable degree.

Like so many magazines TWMX needs to do their homework and better understand fuel specs and how engines produce power before they put things in print. ;)

Let's take a look at a couple of the Firepower brand race fuels and see if we can't get a better idea about this :

Firepower Leaded 893 - 118 octane (6.00 grams lead /gallon)
Firepower Unleaded 324 - 101 octane (oxygenated no lead)


If you look at the heat energy (heat of combustion) available from a pound of fuel you get :

Leaded 893 19020 BTU/lb
Unleaded 324 18747 BTU/lb

If you only looked this at the spec sheet it would appear that the leaded race fuel would make more power due to it's higher energy value, but that isn't the case. You can't just look at the heat energy of the fuel, you have to factor in how much fuel will react with a pound of air to release that energy. In other words you can't tell how much energy is really released until you divide the the true air fuel ratio of a fuel with the heat of combustion value to get what is commonly referred to as the specific heat or combined heat of the fuel.

So lets take a look at what these same fuels look with that in mind.


Leaded 893 19020 BTU/lb of air divided by it's air/fuel ratio of 15.29:1 gives us a specific heat value of 19020/15.29 = 1244 BTU/lb of air

Unleaded 324 18747 BTU/lb of air divided by it's air/fuel ratio of 13.84:1 gives us a specific heat value of 18747/13.84 = 1355 BTU/lb of air

Well look at that, the unleaded fuel will produce more usable energy when all is said and done. :laugh:

This is just one example to illustrate a point. If you look at the heat energy value of methanol it's only 8750 BTU, yet due to it's very low air/fuel ratio 6.47:1 it has a specific energy of 1352 BTU/lb of air.

Dr. David Redszus of FirePower Fuels has shown me on numerous occasions that almost all legal fuel blends make about the same power when tuned correctly. The difference between the highest and lowest fuels in terms of BTU/lb air is only 4% unless you start getting into the exotic stuff. Other factors are much more significant so don't worry about the heat energy. While it may be sort of fun to dissect it like this , it is for our purposes pretty unimportant and ultimately so is wether or not there is lead in the fuel. :thumb:

*^%(^ moderators!

The history shows it was moved to advanced technology by one mod, then moved back by another. I tell ya, finding perfect help is impossible these days.

Someone probably moved it to the Advanced forum hoping I would see it and help get it rolling. Once I saw that no one was jumping in it was clear to me that more members visit this forum and might add something to the topic or get something out of it so I moved it back. If we see a post can fit well in more than one place and it isn't getting enough of a response we'll move it in an attempt to get people to respond.