In the real estate business there is a saying that goes “location, location and damn location”. Quite a few years back, an engine builder found that his real estate agent’s saying was correct in more ways than one. I’m referring to the use of Dominators and even Split dominators on the modern day racing engine. Dominators and of course Split Dominators improve what is called the “venturi’s line of sight”. This improvement of “line of sight” decreases the fuel droplets loss of suspension percentage and takes more advantage of fuel shearing cylinder pulses. At that time they probably also noted they could use a fuel with a lower distillation curve, operate with less ignition timing (or tolerate more) as a result of the cooler (less heat absorbed) incoming charge this placement offered.
As nitrous technology moved into the picture, racers were beginning to realize placement of fuel delivery devices and the resultant effects of improper placement. Nitrous systems at that time were just pouring in un-atomized raw fuel and hoping that most of it would burn and not get in between the ring lands and hurt the engine. Later on nozzles and plate designs improved and multi stage systems stepped into view and tremendous performance followed. The modern day Pro-Mod engine churns out well over 2000 horsepower and most heavily dosed single carb engines are in the 1600 horsepower range. That’s when the problems begin to surface. The use of analysis equipment is required in these power plants as often the sparkplugs can be deceptive. Oxygen sensors are a reference tool but they can really get you in trouble if you don’t know what you’re looking for when first getting a program going. So EGT, RTD and CHT sensors were used to offer up information on what’s going on in the chamber. However, due to the increase in fuel required to burn and the lack of ignition lead time required, EGT type sensors were relegated to a reference implement as well. Oftentimes EGT readings in the 1500 degree range would result in very fast elapsed times and not a piston would be scorched. However, some racers would see 1400 degrees and wipe out half a dozen pistons. In our High Performance tuning video, we discuss residual fuel burning in the pipes. But the real problem isn’t the unburned fuel; it is why unburned fuel exists at all. Offering up a variable fuel curve and tighter stronger spark may help lower this residual number, but the bottom line is one word. TIME. The modern nitrous systems are supplying the fuel in a burnable fashion, but time is that one limiting factor that just can’t be avoided.
So since time is the problem, how about speeding up the burn rate of the fuel. Well, you can make your own fuel blends to speed up the combustion process and that works. You can get in touch with a reputable carburetor builder to improve the atomization of your carburetor and that works too. You can also work the ignition timing to change it with the engines needs to more completely burn the available fuel as the rpms change. If only for a moment we could burn all the fuel that actually entered the engine and wasted nothing I don’t see any reason why 6 horsepower per cubic inch could be attained. Formula One engines are already flirting in the 5’s.
While we’re touching on the subject of fuel blends, remember, more than one engine has been burned up as a result of fuel tampering. Some people know how far they can push fuel tech dept. but these numbers have no bearing on the performance potential of the newly constructed fuel. Additives and bases such as Tri-Nitro, Prop Oxy, MEK, Dioxane and Acetone are pretty rampant in the karting industry. A good blender will know that it takes typically a 12 percent blend of propylene oxide with its high heat of vaporization ability to even see a difference in your program and he knows how much to adjust the ignition timing to avoid a melt down. But do remember, there are no miracle fuels that you can just pour in horsepower without some type of evil trade off. Be it heat, or engine wear or even cancer causing agents. Fuel is tricky stuff. If you’re thinking of Dioxane, remember it takes 10-15 percent to make a difference and this stuff is a Class A carcinogen. I won’t even be in the room if anyone cracks open a can of that stuff. So work on other things. Its better on you and your competitors. Noone needs to breathe that stuff.
Talking about performance potential, lately we’ve been doing a lot of testing with different emulsion programs and fuel shapes. As a result we have improved the fuel mileage in our Trans Am carburetors by 10 percent (showing an improvement in power as well) and a recent test of a pair of these Dominators equipped with these programs have once again outperformed EFI on a 1200 horsepower engine. So carburetors still hold the crown as a superior mixing device.
Lastly, this is not a sales pitch, this is just good advice. Don’t over carburate an engine, especially a nitrous engine. If you’re burning or detonating pistons, blaming the nitrous company may not be the correct direction. A solid nitrous tune-up is a serious heat and power maker. As a result detonation is always lingering nearby. So be sure to have your carburetor built for nitrous (there is a difference). The pistons you save could be your own. I get the carbs and stories everyday.