Notices
Track & Autocross Talk lap times and race lines.

heel toe down-shifting ? rev-matching ?

Old Sep 12, 2002 | 05:56 AM
  #11  
jaje's Avatar
jaje
HC Racer H5
 
Joined: May 2000
Posts: 4,261
Likes: 0
From: KCK
Default

Originally posted by FourthGenHatch
I thought Heal-Toe was just for drifting.

My pedals don't all line up with each other so I can't do that anyway. I tried and the gas pedal is down way too far for me to reach the brake.
you can adjust the accelerator and brake pedal for height and get pedal covers to increase the size to make it easier...it just takes some time and adjustment to get it all to work right
Reply
Old Sep 13, 2002 | 07:06 AM
  #12  
Andy's Avatar
Andy
Hybrid Forum Moderator
 
Joined: Mar 2000
Posts: 2,363
Likes: 0
From: Southwestern PA
Default What's up?

I just though I'd throw my 2 cents in here. Heel toe is the correct term, but wrong concept. As far as I can tell, it actually came from some much older (maybe even the orignal) Ferrari race cars that had the brake pedal on the right and gas in the middle. If you visualize that, heel toeing makes a lot more sense (foot like this / toe on brake, heel on gas).

Heel toeing and double clutching are two entirely different things, but they can be used together. Heel toe was already described pretty well. Use the left flat of your foot on the brake and the right heel on the gas. It takes a little practice but it becomes very natural after a while. You would use this to slow your car and accelerate your engine at the same time. Imaging pushing your car through a corner at it's absolute limit. You enter the car in 4th gear, you want to leave in 2nd. Coming into the turn, you would brake heavily to slow the car, you would turn in, apex, and then accelerate out. Most of the time for an apex, you need both hands, so that's not a good time to shift (especially if you don't have power steering) and if you wait till after the turn, your going to loose speed as you shift, so you want to shift before the turn. The reason you rev match is to make the transition as smooth as possible. Remeber, your cornering at your cars absolute limit, all four tires screaming, starting to loose control limit. If you had the balance of the car upset by the engine as it surges to match rev's, your probably going coming out of that turn backwards. You stand on the brakes and clutch, slide the car out of gear and into the one you want (4th to 2nd) and slide your foot over to rev the engine up. Once your rev's match your speed in 2nd, let the clutch out and your most likely also starting to turn in to the corner. As you come out, you just push the gas down and acclerate out.

For double clutching you would do the same thing, except you'd have to slide the shifter from 4th into neutral, let out the clutch, rev the engine to match then, re-engage the clutch and then slide into 2nd and let the clutch out. I need to get to class right now, but if your interested, I'll explain why when I get back. With modern transmitions, this isn't really nessicary. Seeya.
__________________
Andy - Reinstated Hybrid Forum Moderator

'06 Subaru Legacy Spec B - Stock, for now
'98 Civic EX - CTR headlights and grill, Kosei K1's, for sale
'90 240SX - SR20DET that will never get installed, project car.
Reply
Old Sep 13, 2002 | 09:27 AM
  #13  
Andy's Avatar
Andy
Hybrid Forum Moderator
 
Joined: Mar 2000
Posts: 2,363
Likes: 0
From: Southwestern PA
Default What's up?

Alright, I'm back. Quick double clutching info (if any of your are familiar with my posts in the hybrid forum you know this is not going to be quick). There are 3 parts to your drivetrain. The engine/flywheel, clutch/halfshaft (which is probably the wrong name, but I'm using it for this example), and other halfshaft/diff/wheels. There are two shafts (I'm calling them halfshafts but I know the wrong name, I just can't remeber the correct one) that run parallel to each other in the tranny.

The flywheel is obviously bolted to the engine and turns the same speed as the engine no matter what. The halfshaft/diff is attached to the wheels and can only turn how fast the wheels are turning. The clutch/halfshaft is the one your concerned about when you double clutch. When the car is in gear and the clutch is not pushed in, everything is turning the same speed. When you push the clutch in, the engine disconnects and only the clutch/halfshaft and diff/halfshaft are still turning the same speeds. Slide the tranny out of gear and they all turn seperate speeds (they'd all start to slow down at different rates, in that example). If you put the car in neutral and leave the clutch pushed in, the engine is turning whatever speed it is (idle or if your holding the gas) and the halfshaft/diff is turning whatever speed the wheels are. The clutch/halfshaft is just freewheeling.

Lets say for a second that you don't have any syncro's in your tranny (you do, but some much older and some racing transmitions do not). When you push the clutch in and slide the tranny into gear, a shift fork engages one of the gears on one of the halfshafts (usually the clutch/halfshaft, but not on all trannies). If the clutch/halfshaft and diff/halfshaft aren't turning the same speed, your going to grind your gears. With a syncromesh tranny, when you start to engage the gear, the syncro's go to work and help to spin that clutch/halfshaft up to speed so it doesn't grind.

Lets say your moving 40 mph and you want to go into 3rd gear from 4th (you would need to up the revs for the new gear). With a syncromesh tranny, you would only need to push the clutch in, slide the shifter from 4th to 3rd (the syncro's will equalize the speed of the clutch/halfshaft diff/halfshaft, they work very fast), tap the gas to bring the engine rev's to around 3000 rpm (what most Honda's are at about 40mph) and let the clutch out and you'd have a smooth shift.

If you don't have syncro's, You would have to push the clutch in and slide the tranny into neutral and then release the clutch and use the engine to spin the clutch/halfshalf up to speed. You'd then have to push in the clutch again and put it in gear before the clutch/halfshaft slows down. If you did it correctly, when you disengage the engine, the two halfshaft are at equal speeds and the shift will be smooth. If not, you'll get grinding as it equalizes anyway. You then need to keep the engine rev's at the correct level and let the clutch out to re-engage the engine. That's double clutching, fun huh.

Most (probably all) modern tranmsitions use snycro's. They make rev matching a lot easier and they are also very tough and will last the length of the car. The downside is they do take up space in a tranny, specifically part of the gears themselves. This means you have to make the actual gears smaller to accomodate them (smaller = weaker). Syncro's also weigh something, it's not much, but on serious racecars, they're a luxury that can be skipped for weight savings. If you've ever heard of Honda's 3rd gear syncro's going bad, I think there's a reason for that. When your drag racing (or any racing) you sometimes leave your hand on the shifter, in 3rd gear specifically. What kills those snycro's is overengaging the gear (pushing and holding the shifter up rather than letting it rest in the gear) that doesn't allow them to disengage and rest. I don't know if that's true or not, but it's been my experience and I still need to rebuild my tranny. Seeya.
__________________
Andy - Reinstated Hybrid Forum Moderator

'06 Subaru Legacy Spec B - Stock, for now
'98 Civic EX - CTR headlights and grill, Kosei K1's, for sale
'90 240SX - SR20DET that will never get installed, project car.
Reply
Old Oct 3, 2002 | 10:34 AM
  #14  
jaje's Avatar
jaje
HC Racer H5
 
Joined: May 2000
Posts: 4,261
Likes: 0
From: KCK
Default

good article i came across on heel/toe

http://www.nasaproracing.com/hpde/heelandtoe.html
Reply
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
ED9man
Track & Autocross
10
May 25, 2004 03:08 PM
Doc Gyneco
The Basement
9
Nov 21, 2003 04:32 PM
Rawbeef
The Basement
9
Jul 8, 2003 04:10 PM
ballsoutracecar
Integra & 97-01 Integra Type-R
22
Jun 2, 2003 01:50 PM
Kangbateh
Integra & 97-01 Integra Type-R
7
Mar 19, 2003 09:09 AM



All times are GMT -8. The time now is 06:26 PM.