Interesting observation when upshifting

So, I know that our cars come with something called a clutch delay valve, and I’m not entirely sure what it does to be honest. But, I’ve noticed recently that I can get very smooth upshifts when I wait about half a second after I shift into the gear. The process goes like this:

-Release throttle
-Clutch in
-Upshift to next gear
- (Wait 1/2-1 second before moving clutch)
-Clutch out
-Press throttle

That pause after the gear is selected has made a world of difference in my upshifts. What was mildly jerky before is practically buttery smooth now. However, obviously the counterpoint is that you are slower because you have that extra half second of no throttle. I have also tried releasing the clutch to the friction point and pausing for a moment after selecting the next gear and that makes it a bit smoother but nowhere as near as smooth as just holding the clutch pedal all the way in for that time.

Is this the clutch delay valve causing it? I don’t really have a problem with it, but wouldn’t that extra half second with the clutch in mean just an extra imperceptible amount of wear on the clutch? It definitely seems like it does a lot better with slower shifting compared to fast.

Anyone else notice this? I know some people also removed their CDV - was this what caused you to remove it?

Zeffy94 said:

So, I know that our cars come with something called a clutch delay valve, and I’m not entirely sure what it does to be honest. But, I’ve noticed recently that I can get very smooth upshifts when I wait about half a second after I shift into the gear. The process goes like this:

-Release throttle
-Clutch in
-Upshift to next gear
- (Wait 1/2-1 second before moving clutch)
-Clutch out
-Press throttle

That pause after the gear is selected has made a world of difference in my upshifts. What was mildly jerky before is practically buttery smooth now. However, obviously the counterpoint is that you are slower because you have that extra half second of no throttle. I have also tried releasing the clutch to the friction point and pausing for a moment after selecting the next gear and that makes it a bit smoother but nowhere as near as smooth as just holding the clutch pedal all the way in for that time.

Is this the clutch delay valve causing it? I don’t really have a problem with it, but wouldn’t that extra half second with the clutch in mean just an extra imperceptible amount of wear on the clutch? It definitely seems like it does a lot better with slower shifting compared to fast.

Anyone else notice this? I know some people also removed their CDV - was this what caused you to remove it?

Click to expand...

This is two things, clutch delay valve, and rev matching. The wear from the valve inducing slip on the clutch is minimal if you aren't under throttle. Clutch delay valve is annoying, but not enough for me to bother taking it out.....not yet anyway.

Zeffy94 said:

Anyone else notice this? I know some people also removed their CDV - was this what caused you to remove it?

Click to expand...

A form of this was why I removed the CDV. It would grab the clutch when I would do a normal speed shift. If I let out the clutch super slow then it would do fine. It would do good when I went in reverse. I thought it was because I went so slow in reverse, but it could have been because I held in the clutch so long while I was looking around to back up. I will never know now though as my CDV is gone. I love the clutch now.

yeah it's mostly rev matching system in work, I do it similarly as you.
-release throttle
-clutch in
-(wait 1 sec)
-upshift to next gear
-clutch out
-throttle
waiting before upshifting and letting the revs drop, is a bit easier on your synchros, you are making sure you have clutch all the way down before upshift, also you can release the clutch pretty fast and still be smooth.

Unfortunately it will not work if you turn off rev match system, your rpms will blow past the next gear and when you release the clutch the rpms will jump up a bit and it won't be as smooth, one upside to this is with practice and learning the timing you can be a lot faster with you gear changes when rev match disabled.

I meant manually rev matching by waiting for the revs to fall. Only the Type R has rev matching as a feature as far as I know.....however if you enabled cruise control and change gears it will perfectly match the revs for the gear you are going into, kinda cool and yet pointless. At least that is what I have witnessed on my SI.

How does rev matching work on upshifts? All of the YouTube videos on driving manual cars only mention rev matching when downshifting - but I remember reading that the rev matching system works for both upshifts and downshifts.

Zeffy94 said:

How does rev matching work on upshifts? All of the YouTube videos on driving manual cars only mention rev matching when downshifting - but I remember reading that the rev matching system works for both upshifts and downshifts.

Click to expand...

It holds the rpms where they match up for the selected gear. This allows you to clutch out into perfectly matched ratio of rpm:mph for your selected gear. The Nissan 370Z does it quite well. But with any car, spend enough time driving and you can build a habit for how long to wait between upshifts and how much of a poke to give the throttle between downshifts.