In the off season it is a good time to reflect back on a specific event that took place this last summer.
At the last race at Pacific Raceways on July 30, 2011, Paul made a pass at 12.54 @ 106.12 MPH at a density altitude of 1673 feet in Torri’s Tempest. Prior to him going to Boise, Idaho for the E.T. finals, we calculated and adjusted the main jets in the carburetor and the ignition timing to minimize the loss of power running at higher altitude.
In one pass at Boise he ran a 12.758 @ 105.770 MPH at a density altitude of 3812 feet. And the highest density altitude he ran at Boise was 5029 feet, and even at that high density altitude went 104.68 MPH. [Only 1.44 MPH off the above mentioned run at Pacific Raceways]
Yet we know of many Pro and Super Pro cars that came to Boise from Pacific Raceways and saw their performance drop off markedly by .6 seconds and 6 mph in higher horsepower vehicles. Why? Because they failed to calculate or make any adjustments to their air/fuel ratio prior to going to Boise! They were simply running far too rich at Boise and their performance markedly suffered.
I recommend that our fellow racers spend some time on our Tech Tip page where we address the need for changing main jets when going from a low altitude track to a high altitude track or conversely, going from a high altitude track to sea level.
The specific article dealing with this is: Air Density & Fuel Mixtures which I wrote in February 2004.
I have a lot of information on that page that may help your program and it’s all for free. You just might learn something!
Roger Young – Edwards & Young Racing, bear317@aol.com
It was sure fun times at Boise, that was for sure. I think the biggest thing I noticed was the difference with 60′ times as the mph was pretty good thanks to the adjustments you guys made prior to the race.
Paul, knowing what we know now since that was our first time running at Boise, we could have taken away some pumpshot and improved the 60′ times also.
My concern was that occasionally, the Pontiac had experienced a hesitation on the initial hit of the throttle and I knew by not adjusting the pumpshot that would be completely eliminated at the higher atltitude – in affect the pumpshot would be a tad rich – but the trade off was it makes it a bit lazy.