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Old 03-25-2008, 11:49 PM   #21
hjkim550
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Join Date: Feb 2008
Location: chicago
Posts: 85
Quote:
Originally Posted by 986chris
downshifting at the track with a throttle blip helps shorten the time it takes the engine to recover from the lower ratio you're about to engage.
Chris,

Hate to nitpick but I just wanted to clarify. I believe the real reason why we heel-toe and blip the throttle for downshifts is to match revs and minimize shock to the input shaft / output shaft / synchronizers and most importantly the rear grip = overall balance of the car through the corners.

When we depress the clutch the engine is no longer connected to the input shaft. With your foot off the throttle the engine falls to idle speed 1,000 RPM. You are correct in stating the throttle blip will help the recovery and keep it from bogging. However, the real reason is that if you release the clutch without the throttle blip to match the input shaft spinning at 3,000 RPM in 2nd gear, (even with the synchronizers) there is that lurch as the engine puts a huge strain on the input and output shaft and the rear tires as the teeth come into contact. The rear tires strain to speed up the engine and the engine in effect puts the brakes on the rear tires. Nothing like having the rear wheels lock up and spinning your car in mid-corner. With the throttle blip, there is ideally no difference in RPM speed between the engine and input shaft... no change in cornering stance and a smooth and gentle turn.

Believe me, I do not have any delusions of being a smooth and proficient heel-toer but I get this driven into me by my friends who race regularly. Like they always say, downshifting for corners is not to help slow the car down. Brakes slow the car down. You downshift to get the car in the right gear for the exit out of the corner.
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