Downshifting On Track

[davepoth]

Turkish91 said:

I agree with one of the above posts, it's kind of tricky to explain just how to do it right... With practice you yourself just know when it's right!

If I ever try to do it on the road, I find it very jerky, almost like I'm briefly pressing the brake pedal too much. On track though, under heavy braking and higher speeds it feels perfect.

On most cars it's easier to do it when you're pushing hard on the brake pedal. Out on the road you have to keep your foot in the same position when pushing gently against a pedal with very little resistance, which is much harder.

[waremark]

davepoth said:

waremark said:

DDC may reduce wear on the synchro. I don't understand why you think it adds to perceived smoothness.

What do the synchros do? They allow you to change gear even when the relative speeds of the gears are far apart, which causes wear on them. The greater the difference in speed, the more wear.

DDCing is the ultimate technique for matching the relative speeds of the gears in a manual gearbox, and if you do it properly the speed differences are minimal. Because the gear speeds are already pretty much matched, the difference in torque between the input and output shaft is minimised as much as is possible, since torque is a turning force.

Where does that torque difference go if you don't bother matching the input shaft to the output shaft, or do it badly? Some of it is turned into heat by the clutch, but some of it manifests as undesired acceleration or deceleration. That's what's jerky, and that's what is minimised by DDCing.

No. We are not understanding one another. If engine speed is well matched to road speed a single declutch change does not cause any extra work or heat for the clutch nor any jerk. If anything it is easier to make a perfectly smooth gear change with single declutching than with double declutching.

Is there any chance that you are confusing rev matching with DDC, which simply means letting the clutch out in neutral and then depressing it again before engaging the new gear?

[RenesisEvo]

Apologies for the slight diversion, but this is something to which I've never really found a satisfactory answer.

I accept heel & toe is generally the best method for downshifting whilst on track. But what if that method isn't an option? What if you can't? Either not having learnt to, or having a vehicle that makes it extremely difficult to do so? Then what do you do? Maybe it's just me, but there's a journey between rev-matched downshifts and deft well-practiced h&t; between the start and end points of that journey lies an awkward situation when tackling circuits.

Putting it into perspective, my first foray into track driving had me feeling utterly daft rev-matching each downshift separately the 'traditional' way (on brake, release brake, clutch in, gear, rev match, release clutch, back on brake, repeat, cringe...) which as you might imagine, was dreadful. Mercifully the instructor was kindly ignorant of it, until I snatched the brake once into a tight chicane. I was caught between not wanting to simply lift the clutch and let the driveline take all the pain, and not being in a position to h&t (it would've ended badly). Of course I was not remotely threshold braking - walk before you can run etc. Is it a case of just braking, sticking the clutch in when needed, and throwing in the actual gear you want in after, sacrificing the engine braking?

I'd be very interested to hear the thoughts of those far more experienced than I. Meanwhile, I will continue to learn how to h&t (I can highly recommend a Morgan 3-Wheeler as a tool for that).

[R_U_LOCAL]

RenesisEvo said:

Apologies for the slight diversion, but this is something to which I've never really found a satisfactory answer.

I accept heel & toe is generally the best method for downshifting whilst on track. But what if that method isn't an option? What if you can't? Either not having learnt to, or having a vehicle that makes it extremely difficult to do so? Then what do you do? Maybe it's just me, but there's a journey between rev-matched downshifts and deft well-practiced h&t; between the start and end points of that journey lies an awkward situation when tackling circuits.

Putting it into perspective, my first foray into track driving had me feeling utterly daft rev-matching each downshift separately the 'traditional' way (on brake, release brake, clutch in, gear, rev match, release clutch, back on brake, repeat, cringe...) which as you might imagine, was dreadful. Mercifully the instructor was kindly ignorant of it, until I snatched the brake once into a tight chicane. I was caught between not wanting to simply lift the clutch and let the driveline take all the pain, and not being in a position to h&t (it would've ended badly). Of course I was not remotely threshold braking - walk before you can run etc. Is it a case of just braking, sticking the clutch in when needed, and throwing in the actual gear you want in after, sacrificing the engine braking?

I'd be very interested to hear the thoughts of those far more experienced than I. Meanwhile, I will continue to learn how to h&t (I can highly recommend a Morgan 3-Wheeler as a tool for that).

Firstly, have a read of my post on track braking, which includes a section on rev-matching and heel/toe.

If the problem is that you're finding heel/toe difficult to master, then you simply need to practice. Like any new or different technique, it requires considerable thought and practice at first until it starts to take less thought and becomes more "natural". I find that I can still only effectively perform good heel/toe downchanges under heavy braking, which is fine on track, but requires some careful observations - particularly in the mirror - if you're going to practice on the road.

If the problem is that your car doesn't easily allow heel/toe changes, then perhaps you might want to consider some minor modifications. My track car is fitted with some pedal extensions which I further modified with skateboard tape, and I replaced the flat steering wheel with a dished one which allows my knee more room to heel/toe.

Alternatively, if you're still struggling, you should adopt the more traditional systematic approach to braking and changing down. On the approach to a corner, rather than looking to trail-brake or carry your braking into the corner, aim to get all your braking completed in one go in a straight line. After coming off the brakes, leave enough room to make one block gearchange into your chosen gear with a nice throttle blip or rev-raise before releasing the clutch and then turning in to the corner. Engine braking isn't necessary if you're making effective use of the brakes.

This technique keeps things simple, sticks with the skills you've already got and will still allow you to make decent progress on track. You won't set any lap records, but that isn't what track days are about - they're about stretching your car's legs in a safe environment - within your own limits - and enjoying yourself.

[checkmate91]

I've been driving Fords for the past 15 years, new ones mind, and currently run around in a 2009 Focus RS, which I've owned since new. The whole Ford Power Train Module and ECU philosophy seems to me to be hell-bent on frustrating the progressive driver in favour of the "average motorist". Along with the dual-mass flywheel it seems to me that feathering the throttle, feeding in the clutch is absolutely not what the power train electronics is expecting and over (under) compensates accordingly. Rev matching seems to be allowed but h&t is frowned upon. It doesn't help that in my current car there is an override whereby throttle and clutch has limits to protect the transmission. Doesn't mean that you cant do a full-bore standing start in second but it does seem to try to out-think the thinking driver out on the road.

Best car I ever had for h&t and rev-match gear changes was a 1986 mini with unassisted brakes. You had to apply real pressure on the brake pedal to slow it which gave you the freedom to pivot the outside of your foot on the throttle pedal to blip. I modified my 1991 mini from assisted to unassisted brakes as a result (had to find an unassisted pedal as the drilling points for the master cylinder clevis pin is different on the assisted cars). The ford pedal placement is quite good for h&t but as someone said earlier unless you're on it (i.e on a track) it's very hard to balance braking and throttle on these cars (especially given the ECU is fighting against you). Best car I ever had for clutchless gear changes was a 1959 Ford Anglia 105e. Felt like it was made for them (non-synchro 1st gear too), lovely gearbox on those things.

Having said all of that, I always blip and rev match gear changes and often double declutch going down, occasionally going up in lower gears. Just love it.

[waremark]

checkmate91 said:

I've been driving Fords for the past 15 years, new ones mind, and currently run around in a 2009 Focus RS, which I've owned since new.

Interesting. Can you describe more specifically what the car actually does to frustrate good driving?

[Redline88]

waremark said:

checkmate91 said:

I've been driving Fords for the past 15 years, new ones mind, and currently run around in a 2009 Focus RS, which I've owned since new.

Interesting. Can you describe more specifically what the car actually does to frustrate good driving?

I'm interested in your opinion as well. I have an ST with the mountune 260 kit and the RS clutch. I think the problem is a lack of progressiveness with the throttle and unless you're pretty much spot on with the revs you still get a jerk. That said, if you're a bit slower with the clutch release you can have smooth shifts 99% of the time however when I last had instruction, the instructor said that my clutch release was far to slow. Any faster seems to be near impossible though! I'll try to find a video and post it to describe better.

Cheers!

[Redline88]

Here's an example:

http://youtu.be/ULYCN590sHI

If I release the clutch at this speed, I can et smooth shifts 90% of the time and those which aren't have a minimal jerk. However any quicker at all and I find it near impossible. Is this related to the DMF that you speak about in the RS?

[davepoth]

Redline88 said:

Here's an example:

http://youtu.be/ULYCN590sHI

If I release the clutch at this speed, I can et smooth shifts 90% of the time and those which aren't have a minimal jerk. However any quicker at all and I find it near impossible. Is this related to the DMF that you speak about in the RS?

By the sound of it you don't have the revs matched - they're a bit too low when you're re-engaging the clutch. Either rev more, or brake harder.

[waremark]

Redline88 said:

Here's an example:

http://youtu.be/ULYCN590sHI

If I release the clutch at this speed, I can et smooth shifts 90% of the time and those which aren't have a minimal jerk. However any quicker at all and I find it near impossible. Is this related to the DMF that you speak about in the RS?

When you talk about speed, do you mean road speed or the speed at which you raise the clutch? If you mean the speed at which you raise the clutch, I did not see that speed as a problem. As well as getting the revs high enough, it is also important to get the timing right so that you release the clutch before the revs drop again.

I realise all this may be obvious.

[Redline88]

waremark said:

When you talk about speed, do you mean road speed or the speed at which you raise the clutch? If you mean the speed at which you raise the clutch, I did not see that speed as a problem. As well as getting the revs high enough, it is also important to get the timing right so that you release the clutch before the revs drop again.

I realise all this may be obvious.

Cheers Dave - I think that may be partially down to the crap camera quality!

In terms of the speed, I was reffering to the speed of raising the clutch pedal - good to note that you think that speed looks ok as any faster seems to really just mess everything up. I also don't really see any benefit to raising it any faster eithr if I am honest.

Thanks for the tips