What’s the difference between double clutching and single clutching, if in single clutching you raise the engine speed while the clutch is engaged?

Question

I keep reading articles about double clutching and they all say the same thing. You double clutch so you can rev match.

When I down-shift, I press the clutch, and while I’m moving the shifter to the next gear, I rev the engine. Then when I release the clutch the engine is spinning at a higher rate and the transition into the lower gear is smooth.

So why is that not the same as double-clutching and rev matching? Is there an extra benefit to revving while the clutch is disengaged? That’s what I can’t find. If the articles say “double clutch so you can rev-match”, but you don’t need to double clutch to rev-match, then why do you need to double-clutch?

In: Other

Answer 1

You’ve received some decent answers but I wanted to add one thing. None of this will ever be an issue for you on any modern small light weight transmission. Where it is a skill that you must absolutely master is when you try and drive larger vehicles with manual transmissions. Heavy truck transmissions must be shifted properly, including rev matching. If you don’t do this correctly, the transmission will complain loudly and the chance of doing very expensive damage is much increased.

One of the recurring comments is about meshing gears together. This is very misleading as almost all gears are in constant mesh with one another. You don’t move the gears during a shift, you lock the desired gears to the transmission shaft. If you really want to understand what is happening, look for an animation of how a manual transmission, with and without synchronizers, works.