Trading SRT-4 for STi?

Both are used for matching revs while down shifting. Heel & toe (really ball & blade thse days, but named back in the old days when the pedal layout was a little different) - while applying brakes with the ball of the (right) foot, roll foot to right to apply gas with the blade of the foot as the clutch is released to match revs for the lower gears (less transmission wear, but more importantly, no sudden engine braking while the tires are at the limit of adhesion). Optional - can double clutch during the downshift to match the speed of the transmission & sycros, further reduced transmisssion wear but takes longer.

 

here's an article on heel and toe someone else posted some time ago:

http://www.edmunds.com/ownership/howto/articles/45792/article.html

 

Greddy Catch Can

learn it...practice it. it's fairly easy in the STi.

 

If you find that your foot is not wide enough to effectively reach both pedals at once, an aftermarket gas pedal plate can do allot to help with that.

 

When you do this (going into say a 3rd gear corner exit from a 4th gear straight) make sure that you don't use the engine for braking, the brakes are for brakeing. If you use the engine to slow the car, you will need to modulate the brake pedal to keep the deacceleration rate the same. (halfway in the braking zone, you'll need to let up slightly off the brake while you engage the clutch. Once the clutch is engaged, you need to get back on the brake.) This ensures that your car has a smooth weight transition to the front tires. If you are not smooth, your front tires will load up, then unload, then load back up when the shift is completed.

Practice from 5 to 4 and 4 to 3 and get that right, then go 3 to 2. I do this on off ramps from the freeway when I'm not at the track.

Going into second, you may need to double clutch as you are heal-toeing. This is regarded as an advanced skill. You should be competent at both indvidually before you try them together. The pace is very fast and a missed shift into second will either upset the balance of the car, grind gears or leave you out of gear on exit. Practice double clutching when going into 1st or 2nd on slow speed side streets (into your garage for instance, just don't hit the back wall! )

When learning, be prepared to abandon the down shift if you get it wrong. No sense in a mechanical overspeed on the engine or going in the ditch when commuting to and fron work (or at the track.)

 

How do you double clutch? Just out of curiosity?

 

How do you double clutch? Just out of curiosity?

1. clutch in
2. shifter (gear) to neutral
3. clutch out
4. clutch in
5. blip throttle to match revs (very important)
6. select gear
7. clutch out

or something like that basically way more steps than necessary with today's cars.

if you drive a racecar though without a synchro gearbox...you'd better be very good at it.

here's some on-line reading for you: double clutching & de-clutching

 

How do you double clutch? Just out of curiosity?

1. clutch in
2. shifter (gear) to neutral
3. clutch out
4. clutch in
5. blip throttle to match revs (very important)
6. select gear
7. clutch out

when you list it like that, you make it seem like some long drawn out process. Many of the steps are taking place at the same time and for me, it's instinctive now and extremely fast... I learned to do it back on my Protege... HAD to do it on my WRX, and now prefer to do it almost anytime i'm driving fast. Until you're good at it, you don't really realize the benefits.

yes, i see your point.

for example you don't need to actually push the clutch in before shifting to neutral IF you know how and skip steps 1, 2 and 3 on a downshift.

 

Ok thanks i was always curious. What is the added benefits though?

 

Ok thanks i was always curious. What is the added benefits though?

longer gearbox and clutch life.

at a minimum you should be rev-matching for down shifts.

 

just installed my k@n typhoon

Ok thanks i was always curious. What is the added benefits though?

When you match with the clutch engaged (neutral) you're spinning up the layshaft. When you match with the clutch disengaged you're only spinning up the engine, so obviously there's a considerable difference in the amount of rotating mass.

Without synchros you have to double-clutch to match. My opinion is that it's not asking too much of modern synchros to reconcile the mass of the layshaft and gearing, and my experience is that it's faster to match single, because the engine spins up faster by itself.

I think Nick's position is that the double-clutch match is always best. There was a brief exchange on this in another thread a while back. Certainly there is an elegance about double-clutch matching, and kudos to anyone who can pop them off spot-on every time.

Most of the time when I double-clutch match with the STi, I get about the same amount of resistance at the shifter as I do on a single match = very little. Sometimes I can get that near-perfect alignment that Nick was/is talking about.

From a practical standpoint, I think double-clutching is a good idea if you have a lot of RPM's to make up - eg. skipping gears. In terms of time, all of this is going on in the breaking zone, so it seems to me that the breaking is the limiting factor.

Certainly an interesting topic.

 

when i rev match, i clutch in, shift to another gear, rev, and clutch out. i don't have a problem downshifting to 1st gear even running at 30mph when rev matching. as long as the car doesn't jerk your gear box and clutch should be healthy.

 

Dock Connector

Me too. I think the issue is one of how much the synchros are being forced to make up.

 

One thing I've always wondered about Double Clutching and Heel-Toe shifting is how do you know which RPM to blip the throttle to. Is it a specific area depending on speed, or is it uniform for every shift? Say for instance, you are downshifting from 4th ----> 3rd, what would be the optimum RPM range to be in for the shift to go in seamlessly?

 

Rubbing? 245's 17x8 STi Wheels lowered with GF210?

Really you won't know how much to blip the throttle by without practice. Starting RPM in the higher gear, rate of deceleration, and desired exit gear/engine speed all will determine how much you blip the throttle.

Just work on one thing at a time. I find myself doing it all the time without thought just as it has become a normal practice for driving. Just like anything else, it is usually quite obvious when you get it right vs. when you do not. If the car jerks or it doesn't feel smooth then you didn't hit it quite right.

 

My dyno results

ok i really got 1 stupid question...
when should i use heel & toe and rev match? In what scenario?

 

when should i use heel & toe and rev match? In what scenario?

When you have to break and downshift at the same time.

Nick: I'm with you on all the technical mechanics, no problem. All I'm saying is that I don't think double-clutching will actually improve lap times in the STi, and that spinning up the layshaft with the synchros is not going to wear them out prematurely... assuming one can match pretty well. There's no question that perfect double-clutching gets the style points. I can match just slightly smoother double than single, but I'm not as smooth with the extra 1/4 second or whatever you need to stay on the throttle to spin up the extra hardware. No doubt I'll continue to play with it, I'm a geek. Single heel/toe is second nature to me though, so that's what I'll use at A/X and track for the time being. Actually, I think for A/X with the STi, just simply not downshifting is often the smarter thing. The downshift is basically free if you can do it right, but everyone pays for the resulting upshift... and that's expensive.

 

but if you're rev-matching with the clutch disengaged, you're not doing ANYTHING to spin up the layshaft.... So how is your ability to rev-match at all important to syncro shifting?

I think the primary goal of rev matching is to maintain stability of the suspension, which is certainly accomplished without spinning up the layshaft. The second priority would be speed of engagement, which again I think is fulfulled by simply getting the engine speed roughy equal to the drive shaft's speed. The third priority would be wear reduction, and I agree that spinning up the layshaft along with the engine does mitigate synchro wear, I just don't think that is significant in the overall scheme of things. Lastly we have the style parameter, where I agree that a perfect double-clutch match wins every time.

 

Well, maybe this is a fine point. I suppose the synchro wear and engagement speed issues are somewhat entwined. What we would ideally like to do is get everything spinning at precisely the same speed and just 'chuck it through the window' as you do, and tip o' the hat to you... and no I'm not being facetious.

From a practical standpoint, the more stuff we get spinning close to the same speed the better. I'm not a mechanic, but let's say there's #20 of rotating mass in the layshaft and its gearing. That's relatively easy to spin up quickly. We can spin up the engine single-clutch with no problem, so the synchros only have to deal with the discrepancy between the engine and drive shaft, and the layshaft mass.

If we are going from say, 4th at 2500 down to third, there is going to be quite a bit more for the synchros to do if we just push on the shifter without throttling up the motor. Either we are going to have to push harder on the shifter (= more wear on synchros) or we are going to take longer to make the shift. The layshaft is a relatively small fraction of the overall rotating mass, so it does little to slow us down or increase wear.

Strictly from the standpoint of time, none of this makes any difference as long as it can be accomplished in the braking zone.

 

Wrong. With the clutch disengaged (as in single-clutch revmatching) there is nothing to spin up but the gears and input shaft. Rev matching makes no difference UNLESS you double-clutch it, which engages the clutch while you're revving in order to help spin up the input shaft.

But in the context of weight transfer, single-clutch rev matching accomplishes nearly the same result as double clutching. For some people reading this, they might assume that no rev matching on a downshift is necessary, which would be incorrect.

The only advantage I could see with double clutching, would be on a skip shift, say from 5th to 3rd or 4th to 2nd, where the synchros will have to do a lot more work, possibly resulting in a grind or rejected shift.

During a simple downshift, say 4th to 3rd, I couldn't see the added benefit. Though if you can do it consistently, I guess double-clutching for every downshift can only be a benefit, right?

 

Wrong. With the clutch disengaged (as in single-clutch revmatching) there is nothing to spin up but the gears and input shaft. Rev matching makes no difference UNLESS you double-clutch it, which engages the clutch while you're revving in order to help spin up the input shaft.

Now that I think about it, you're quite right about the synchros. With a single-clutch match they have to make up the layshaft's speed, so rev matching makes no difference to their wear without double-clutching. As DF points out though, in the context of weight transfer (I would say power transfer) both techniques accomplish essentially the same thing.

So, basically we are left to decide whether it's reasonable to use the synchros to reconcile the layshaft. This seems reasonable to me, as they are so doing on all the upshifts.

I guess my problem is that double-clutching is always going to be a little bit slower and more complicated than single-clutching. My proficiency with S/C heel/toe is just fine, so that's what I use at HPDE's and A/X. I don't road race. I guess the logical thing is to D/C on the street until it becomes second nature and then try it at the track. It's not good to have the two ideas competing in a performance situation.

 

The thing I find irritating about D/C in the STi is having to stay on the throttle longer to allow the layshaft to spin up. The STi has relatively touchy breaks and relatively slow throttle response. When I H/T downshifts, I punch the throttle pretty quickly... and I have that well coordinated with the break actuation. When I D/C downshifts without H/T, I stay on the throttle about twice as long - maybe 1.5s vs .75s. Having to rock my heel over and hold it there whacks out the breaking a bit. I can do it, it just doesn't flow like S/C H/T. D/C without H/T is no problemo.

I agree that the time difference is a moot point as long as all the pedal work fits into the breaking zone. I have a tendency to break a bit sooner in anticipation of the D/C H/T, but as you say, that's a matter of practice.

When we were kids my friend had a '67 Rover wagon. I never had any problem with that... but then there was never any need for H/T. Maybe I just came to associate D/C with clunking along in a truck.

 

Car bucks from 800 to 3000 rpm if I floor it ?

learn it...practice it. it's fairly easy in the STi.

I am sure its a world of a difference from the S4, eh Tim.

 

learn it...practice it. it's fairly easy in the STi.

I am sure its a world of a difference from the S4, eh Tim.

Word!

did you pull the trigger on an STi or EVO yet?

 

learn it...practice it. it's fairly easy in the STi.

I am sure its a world of a difference from the S4, eh Tim.

Word!

did you pull the trigger on an STi or EVO yet?

Damn!! I can't believe you remembered that. Actually no, not yet. But on a positive note I did pull the trigger on a house . In which I am already investing lots of money $$$$ :-? I did buy myself a 1991 Nissan Sentra SE-R, its going to by my station car. I figure I will have a new car by summer 05'. I am trying to be as patient as possible. My decision is still up in the air about the EVO MR or the STi.