Gear changes with clutch delay valve

[Somewhatfoolish]

Any recommendations on smooth gear changing on a car equipped with a clutch delay valve? Very easy to kangaroo from a start (interestingly this seems to be more likely if you're not accelerating briskly) and 1st - 2nd changes are not that easy either. Not so much of a problem going down gears as I tend to err on the side of blipping the engine a wee bit too much anyway.

Very seriously considering getting the CDV removed but before doing something that drastic would rather pick brains of people here for tips or perhaps a specific technique to try out. I've not really been able to find anything online (other than lots and lots of complaining about them).

[Somewhatfoolish]

I know

[Somewhatfoolish]

Reg Local said:

I've never found them a problem. Are you trying to change gear too quickly? If you're looking to smooth your gear changes out, one of my YouTube videos covers the finer points in detail:

https://www.youtube.com/watch?v=A4rs09AKBc8

I've read both your books, they're fantastic by the way

Been experimenting as advised and I think the key difference with what you're doing is what you refer to keeping the throttle on - as you say in the vid it's the "key to driving smoothly". Problem with a CDV is because the clutch is slipping whether you like it or not, you have to keep a bit more throttle on than you would to change gear smoothly without one. So to answer my question above, the answer is to put on more throttle than you would be doing with a normal clutch.

But this now means that you're slipping the clutch deliberately and also when you transition to another car you're going to be giving it a bit too many revs.

Not mechanically sympathetic

[Somewhatfoolish]

For simplicity imagine you're doing a down change, and you need to take the revs from 2000rpm to 4000rpm. As you're a perfect advanced driver you're doing this downchange to get into gear for a hazard and therefore aren't going to be adjusting speed at all.

So thinking in terms of what your accellerator pedal needs to be doing to keep balanced rpm between the sections of this change (made up figures):

Crusing along at 2000 rpm, fullly in gear - 25% down
Clutch depressed - remain at 2000 rpm initally for milliseconds - 25% down
Bring revs upto 4000rpm in an engine without load of drive train on it - ???% down
Sustain revs at 4000rpm in engine with load of drive train on it ?????% down.

The smooth n calm approach which I think you're advocating is basically to aim to give a bit more ??? than ?????. Works fine, but has the disadvantages I was getting at.

The crap approach is to give less ??? than ?????. Obviously st.

Now what I think most smooth quick gear changers do is they aim, even though they can't really explain why (as this post may be demonstrating), the exact same amount of throttle for ?? and ????. With perfect clutch timing, this will produce the smoothest possible change.

But because you're moving through the power band so quickly the timing really has to be perfect, and the CDV just ruins this, what you end up instead with is:

Bring revs upto 4500rpm in an engine without load of drive train on it - ???% down
React to revs going higher than expected during clutch release by moving throttle to ???%
Jerk as revs crash through 4000rpm as engine gets load of drive train with ??%
Again instinctive reaction to revs by opening throttle to ????%
Kangaroo time!

Notation I have used here means:

? = a throttle level
?? = a throttle level higher than, or equal to, ?
??? = a throttle level higher than, or equal to, ??, and also greater than 25%
???? = a throttle level higher than, or equal to, ???
????? = a throttle level higher than, or equal to, ????

Edited by Somewhatfoolish on Monday 30th January 23:13

[Somewhatfoolish]

Regardless of what the purpose of the CDV may be, one effect of it is to prevent one style of mechanically sympathetic gear change, so can't see why it shouldn't be in this section (it's the obvious section for me as posters in this section are more likely to care about smooth gear changes).

I tried today the opposite of what I did yesterday - changing gear by matching the revs and releasing the clutch as quickly as possible - something I have no problem doing in cars without a CDV. This was horrific, every single change a double jerk. So my own mind is made up and I'm going to get the CDV removed, I see no point in it as I am not in the habit of clutch dumping and nor do I lend my cars to nobs.

[Somewhatfoolish]

Reg Local said:

Why did you try that when almost every post in this thread is advising you to do exactly the opposite?

If you simply slow down your release of the clutch, the valve won't be a problem.

I was trying out one extreme.

One of the things you have mentioned (in my own words) is that one of the best things about the system is it provides a safe + progressive method of driving that a police driver will fallback to when under pressure for whatever reasons.

In a similar way, quick, smooth, and correctly matched gear changes are how I was taught to do it and are what I will fallback to instinctively in a 'situation'.

I'm sure I could retrain myself to change gear more slowly and do it so often so it eventually becomes my fallback - not sure that's best option for me though when I can just get rid of the CDV and focus on other areas of my driving which I think are in more need of improvment.