Todd H wrote:Darin, I don't doubt what your say at all. It's just that I witnessed this time and time again. Would the carb jetting change from a cool engine to a hot engine? What could or would cause the power to rise as the motor got hotter? Like I said I wasn't the dyno operator just the machinist. I always thought it was odd that the motor made more power hot than cold and I'd love to know the answers. Todd H
I don't doubt that you saw the engine do exactly what you say it did. I have seen the same thing. In its current tuning configuration is was tuned well at that temp. The oil was happy, the jetting was happy and I have no doubt that the cam timing was also happy at that temp. Now, If you took that engine and tuned it to run colder, it would make more power. I have seen engines on the dyno with that thick monkey snoot 20w50 oil in them and we take it out, put in some good 05w add some jet, advance the cam and rank the thing at 100 degrees instead of 180 and it gains about 15 to 20 horsepower every time. I am not trying to make a case for ALL engines to be run in this manner, A lot of Super Gas racers cant get away with running them at 100 or 120 because they are making so many runs its hard to get that temp back down before the next run. They have to have a consistent temp to make consistent runs so fighting temp for that last hundredth of a second is not in there best interest and totally contradictory to what they are trying to achieve which is the same ET run after run. They should still try and keep them as cool as they possibly can. With some of these high horsepower engines ( 1200 to 1300hp) that these guys are trying to run in S/C you will see engine damage at high temps. If the chamber temp gets to high they will lift a ring land. I had a customer that purchased one of our 622 engines for S/C and he kept melting the thing. He was running it at 220!!!! I was on the phone with him for over an hour walking through everything he does prior and after a run but nothing stuck out. He did everything normally except one thing. He used the propylene Glycol instead of plain water and the guy who sold it to him told him told him it would dissipate heat better at a high temp so he believed him and melted his engine, TWICE. by the way, there is nothing better to cool your engine than plain old water. A water wetter helps but Anti freeze actually degrades the rate at which water can pull the heat out of the head Propylene Glycol is the worst! Its like trying to cool an engine with molasses. If you have to run antifreeze run the Ethylene Glycol and run it as low a percentage as possible.
In our case that last hundredth is a life or death matter so we take things to extreme. We have a high pressure Ice water injector in the pits that can take the engine temp to 50F in a matter of minutes. We warm the rear end up and break in the clutch, go through the gears, make sure everything is fine then shut the engine down and flash cool it to 50 or 60 degrees. Then we are ready for a run. After the burn out the engine is at 100-110 and that is the launch temp.
by la360 » Mon Dec 06, 2004 2:11 am 
