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Rev match on downshifts - Pros and Cons?
Posted: Thu Apr 02, 2009 12:14 am
by samst0r
Hi
Recently got a Polo 1.2 S 06 and have been looking into 'advanced driving techniques' and I've been trying to find a definitive answer to whether you should rev match when downshifting gears.
I had a go of it today and from what I could tell it does make the ride smoother.
What I did was:
(1) Slow down slightly
(2) Put clutch in
(3) Blip gas pedal to raise rev's
(4) Put into gear
(5) Raise clutch up
Is doing this better for the car than not doing it?
Also if it is better - why do drivin instructors not teach it?
Thanks
(sorry if this is the wrong section to post this in)
Sam
Re: Rev match on downshifts - Pros and Cons?
Posted: Thu Apr 02, 2009 5:38 am
by MeTsU
Hey Sam,
I don't think there are any side effects of doing this, besides using a minimal amount of more fuel. It's something I learnt from my time spent on the track and I must admit that I do it for my everyday driving. I've done it in all three of my cars I've owned, a '99 Mk1 DeCo, '92 Mk2 GTi and now my '05 Sportline TDi. It will certainly lead to a smoother driving experience and depending on the aggressiveness, say an excited overtaking manoeuvre, being about to shift quickly & effectively with a blip in between to rev match will mean you certainly stressing the components less on the initial load.
Hope that makes sense.
Re: Rev match on downshifts - Pros and Cons?
Posted: Thu Apr 02, 2009 5:52 am
by MeTsU
Rev matching is a technique used to prevent unnecessary weight transfer during down-changes in a manual transmission car. For a demonstration of why this concept is useful, select third gear and accelerate to about 3000rpm, then quickly select second and release the clutch fairly rapidly. You'll notice a large forward weight transfer as the engine speed is forced to increase. This can also cause the driving wheels to lock in extreme situations.
Rev matching will make you a much smoother driver when changing down through the gears, a skill which is essential for the track and can lead to faster lap times. This technique is performed by depressing the clutch, selecting the required lower gear, increasing the throttle, and then releasing the clutch smoothly. You'll need more revs if changing from forth to second that from fourth to third. With practice, this can result in very rapid and very smooth changes, and is almost essential if driving on the track. Rev matching can also be performed while braking, this is known as heel and toe. When you first start to learn this technique, you might find it hard to predict the amount of revs you'll need for each gear, but remember any increase in revs is better than none.
LOL, that might make more sense.
Re: Rev match on downshifts - Pros and Cons?
Posted: Thu Apr 02, 2009 8:25 pm
by samst0r
Thanks for the reply
I'll keep doing it then. Hopefully that way i'll get my clutch to last longer :p
Thanks
Re: Rev match on downshifts - Pros and Cons?
Posted: Thu Apr 02, 2009 9:07 pm
by ranson90
now learn to double clutch!
and heal toe!
and you'll be a regular old school ricer!
Re: Rev match on downshifts - Pros and Cons?
Posted: Fri Apr 03, 2009 12:23 am
by captainbeyond88
i'm an observer for the fife group of the Institute of Advanced Motorists and we teach this technique, its called sustained rev downshifting. basically it makes the ride much smoother and reduces the need to brake by using the engine braking to slow the car down to the correct speed for a corner. it does use a bit more fuel but it's pretty much negligable.
i wouldnt want to say its better or worse for the car cause i don't know but i would reckon it's better because the car is designed to use the entire rev range up to the redline and as long as its not pushed over that then its fine. also it reduces the wear on your brakes.
as to the reason why driving schools dont teach it is because its too complicated for someone who has only just got to grips with cluch control to throw this into the mix.
hope this helps...also if anyone is interested in the IAM they should totally do it! it was the most fun thing i've done in ages and it improved my driving so much. (it also makes your insurance majorly cheaper!)
Re: Rev match on downshifts - Pros and Cons?
Posted: Fri Apr 03, 2009 11:06 am
by MarcoPolo
Would it not work better if the clutch plates were closed when blipping the throttle to match the gearbox input and output shaft speeds?
Personally, I don't feel the need for it anymore. It was a requirement in the good old days of syncroless gearboxes, but with modern cars with dual mass flywheels and far superior engine mounts and control systems, there's no need, imo.
If you can drive properly and select the appropriate gear for the road speed, then it's smooth enough for 99% of drivers. Dropping from 4th to 2nd is asking for drivetrain shunt and RWD cars can lock their rear tyres if doing that, so if it's a known consequence of downshifting into a gear that's too slow for the road speed, why do it in the first place?
Re: Rev match on downshifts - Pros and Cons?
Posted: Fri Apr 03, 2009 2:41 pm
by whitegtipolo
whats cheaper to replace clutch or brakes ??? do the math!
Re: Rev match on downshifts - Pros and Cons?
Posted: Fri Apr 03, 2009 4:33 pm
by samst0r
Yeah I I definitely noticed the difference in the smoothness of the ride if I do it.
So can someone confirm that its not going to put extra strain on my clutch and reduce its lifespan?
(sorry I don't really know much about the internal workings of cars)
Re: Rev match on downshifts - Pros and Cons?
Posted: Sun Apr 05, 2009 12:08 pm
by whitegtipolo
but people designed syncro mesh so you dont have do this!! Your driving on the roads not donny park LMAO
