In contrast, the Top Fuel clutch uses similarly placed springs to keep the clutch slipping with the pedal out. As you can see, these two functions are completely opposite. In a Pro Stock or Pro Mod style clutch, also known as a pedal clutch, releasing the clutch pedal pushes the throw out bearing in. But in a fuel clutch, also called a glide clutch, the process is vastly different. Based upon a pre-set timing sequence that begins off a wide-open throttle switch on the gas pedal, the throw out bearing moves more or less quickly, which applies more or less clutch as the car moves down track.
The speed of the throw out bearing also determines how much the clutch will wear, so you are constantly in a state of chasing the wear, compensating for it, and at the same time applying clutch pressure, which eventually results in lockup. When it comes to the wear endured by the two styles of clutches, differences abound. On a typical, successful quarter-mile pass, a Pro Mod clutch should wear four to seven thousandths of material off, whereas a Top Fuel clutch will wear of to thousandths.
Pat Norcia of Ram Clutches offered more explanation of the wear endured in the Pro Mod and Pro Stock classes, but from the extremely important perspective of slippage. However, the racetrack does the opposite in that as it cools, the clutch will normally slip longer.
This is why you see crew chiefs nervously pacing the starting line on an evening session where the temperature is dropping quickly, or looking for a friendly cloud during midday eliminations that might drop the racing surface temperature five to ten degrees.
The clutch normally locks up right when the second system engages. Blower cars have a little longer slip time, usually eight tenths to one second, because they are trying to harness more power and, with their three-speed transmission, will be in low gear much longer than a Pro Stock or nitrous car. It may not sound like much, but the differences in all these numbers are huge.
Top Fuel and Funny Car clutch discs slip and wear to the point that they may go back in the car for a second pass, but are usually trashed after one run. Nothing in fuel racing is cheap, and the same goes for the clutch. There are also several prominent differences in the way the two different styles of clutches are tuned and applied. In most forms of high-horsepower drag racing, to get the car off the line successfully one of two things almost certainly has to occur: either the clutch has to be slipping or the tires have to be spinning.
Charles Carpenter, driver of the Embee Performance Chevy nitrous-assisted Pro Mod, explained this concept in depth. If neither happens, tire shake is the inevitable end result. On a hot, greasy, or just generally bad track, the tires are much more likely to spin, so the clutch is much more likely to lock up.
Those guys can only spin the tires so much before they go completely up in tire smoke. Where tuning the clutches is concerned, the two drivers both weigh in on how they dial in a perfect clutch run, in hopes of seeing that beautifully aligned data graph on the computer monitor back in the trailer after the run.
The eight-inch is smaller and lighter, but has a narrower window in which we can work. Norcia also believes in taking a look beyond just the clutch when it comes to determining a window. Taking this one step further, you need to evaluate the weather conditions you'll be racing in, as well as the track temperature and condition. How long does a Top Fuel dragster engine last? Are Top Fuel dragsters automatic? What happens to a Top Fuel dragster engine?
How much fuel does a Top Fuel dragster use per second? How many G's does a Top Fuel dragster pull? How much horsepower does a NHRA funny car have? How much horsepower does John Force Funny Car have? Car Specs. How much do funny car drivers make? Are Funny cars faster than dragsters? How much horsepower does a Top Fuel dragster have? Why do they call it a Funny Car? How much does a funny car engine cost?
How dangerous is nitromethane? What is better for drag racing automatic or manual? How much does a dragster cost? Similar Asks. Popular Asks. Some drivers use a five-disc system and some use a six-disc system. It all comes down to tuning and preference and requirements.
Lex is someone that I connected with via social media. There's a lot of science and technology behind the sport of drag racing. And the clutches just scratch the surface! An error occurred while submitting your email address to the mailing list. Please try again or contact us for assistance. By submitting your email address you agree to receive email information, great offers, and more from Team Valvoline. Thanks for signing up. Set your password and start earning reward points for everything you do on the site.
Blake is an automotive technology student with a passion for drag racing and is pursuing a career working in the NHRA on Top Fuel Dragsters.
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