FUELforTHOUGHT

by Dave Koehler
9/7/04

Hi Dave, We recently installed a racepak into our car, which includes the exhaust temp sensors. But I cannot find any info anywhere as to the heat range that the exhaust header temps should be. The basic info on the motor is as follows ... KB 526cu Veeney Heads 1471 Littlefield blower Alcohol injected ... Approx. 1800 hp Truck weighs 3200 lbs. and ran a 7.87 at 165 mph last year before the new updates. Anywhere you could direct me or any info. you could give me would be great. Thanks, Arthur H Irwin IV Snap-on Tools

Arthur, This is a good news/bad news thing. The bad news is that there is no magic number to shoot for. The good news is that you won't have to worry about comparing numbers with your pit neighbor. Due to probe placement, type of probe, camshaft, engine load and overall engine design there will not be two engines with the same egt numbers. If you are currently running well and like the looks for your spark plugs then whatever number comes up is your baseline reading. Now ... exhaust temp numbers are great for balancing cylinder to cylinder power via nozzle changes or individual cylinder timing changes. They are also useful as an early warning system for catching something going south on any particular cylinder, bad plug wires, etc. Watch for overall changes in the graph. If one is trying to climb faster than the others or a lot slower than the others but ends up about the same temperature, then that particular cylinder should be looked
at. Hope this helps.

Have a safe race,

Dave Koehler
www.koehlerinjection.com

Hey Dave, I am new to the world of "Pro-Mod" racing. I have seen a few at the NHRA races. Would you tell me the purpose of the mist or spray coming from under the hood by the windshield on nitrous cars before they launch? Thanks ahead of time. Drag Racing Fan, Hank Heberer

Hank, Good question. Nitrous is a steady rate system. The racers can keep their fuel pressure relatively steady but at the moment there is not a regulator that can handle the volume of compressed nitrous correctly. The racers want to leave the line with the same nitrous pressure each time. What they do is warm the bottle so that they have about 950 lbs. of pressure before staging. When they are done with the burnout and ready to stage they activate an auxiliary solenoid that is tied into the hose leading from the nitrous bottle. They let off enough pressure to bring their launch pressure down to 900 lbs. each time and then stage. The spray you see is nitrous being expelled and the process is called "The Purge". It also makes for a neat show and announces to the world that "yup I am bad, don't fool with me." Keep watching and reading. There is much to learn.

Have a safe race,

Dave Koehler
www.koehlerinjection.com

Previous Stories Fuel for Thought — 7/7/04 Dave Koehler answers your nitrous & fuel-injection related questions