I wrote this up for an AutoX class years ago and saved it.
I just match revs by pushing to neutral on brake application and holding revs up and letting the speed reduce to where the shifter goes into the lower gear without any clutch action or crunch. Never broken anyones trans doing this and then the shift is completed prior to apex so I just power out of the corner. There is no lost time for 1st gear downshifts this way.
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Proper method for Double Clutch down shift with Heal & Toe throttle blip....for short “DCHT”.
Example A
In this example you are in 3rd gear and downshifting to 2nd.
1) Push in the clutch and at the same time push the shifter into neutral.
2) Release clutch and blip the throttle the correct amount for your speed. (This brings up the clutch/input shaft up to the same speed as the output).
3) Push in the clutch and pull the shifter into 2nd. You should not feel any crunch or kick in the shifter (hot knife through butter).
4) Release clutch. There should not be any “bobble head” feel or change in speed.
In this scenario you get near zero clutch and syncro wear because no parts are slipping.
Note 1: A single clutch push and throttle blip do not match revs properly at the clutch/input shaft/syncro side of the transmission, it just revs up the motor to lesson driveline lash on clutch release. Feels racy but only doing half of the job.
Note 2: Slowing from 5th gear to a stop and pulling the shifter into 1st at 30mph while the engine is at idle is maximum syncro wear…(Honda Crunch).
Note 3: I use the DCHT on the street for comfort and smoothness and to always be in the correct gear for acceleration if needed. It also helps in traffic to be in a gear that will slightly decelerate the car without having to get on the brakes.
Example B
To further complicate the issue…On the track & for AutoX I don’t use the clutch for downshifts…that’s right…only to up shift.
Same 3 to 2 downshift… Car is at 7krpm at the brake point
1) Left foot brake hard and at the same time release a little pressure on the throttle and pull the shifter into neutral.
2) Keep RPM at 7000 and continue braking until road speed for 2nd gear matches the RPM. (Instead of bringing engine speed up you are bringing vehicle speed down).
3) Slip shifter into 2nd. Release brake and throttle out of corner.
This works for 5 to 2 downshift at the hairpin on Barber just fine. Only one broken transmission in 30years and that was on an up shift back when I was 16.
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