Is rev matching bad for your car?

 

ummmmmm...what are you talking about?

 

Are you talking about rev matching to shift without using the clutch? if yes, it could be disastrous if you dont do it just right. Not to mention, our little 4 bangers rev faster than a big diesel truck engine, FYI most drivers of 18 wheelers dont use the clutch except on initial acceleration from a stop to prrevent wear on the clutch.

 

I'm pretty sure he's talking about rev-matching on downshifting, which is a good thing. It makes downshifts much smoother and it's a lot easier on your tranny. Only negative I could see is a slight increase in fuel consumption which is minimal at best.

 

Rev matching to downshift reduces stress on you clutch. If you are referring to the no-clutch method I would not recommend it especially if you have bad syncros. Bad syncros will cause you to put your car in gear before it is at the correct RPM. Then you will be needing a new tranny.

 

As mentioned, you should always bring the engine speed up by blipping the throttle when you downshift to a lower gear. This prevents the clutch/transmission speed forcing the engine up to the higher speed in the lower gear.

However, rev matching while downshifting does not cause any more or any less wear on the synchronizers. Those are still working just the same whether you rev match or not. The only way to reduce wear on those is by double-clutch downshifting, which is much more tricky. If you don't do it right, you can actually cause more wear on the sychronizers than you would if you didn't do it at all. If your gears are already grinding, then double clutching done right can reduce that.

As for upshifting without disengaging the clutch, that is sometimes known as speed shifting. My dad used to do it in some of the old muscle cars he drove when he was younger. That's also very tricky, and you can only do it at a certain RPM point when the engine and transmission rotation speeds are equal.

Upshifting without closing the throttle is known as power shifting, and that can and will DESTROY synchros and possibly other transmission parts with a quickness. I know because I personally tried it in my old car, and ended up having to get the transmission replaced. Do not ever do this, it's not worth the beating the drivetrain endures, and it will not improve any kind of 1/4 mile ET or anything like that.

 

if youre downshifting to slow down, then forget it. let it coast in gear and use the brakes!

 

This is true, but if you're down shifting to 2nd or 3rd to go around a corner, then you definitely should be rev-matching.

 

its cheaper to replace brakes than clutches

 

yea it is

 

very true

 

lol. you got that right.

 

A properly rev matched downshift saves brake, clutch, and gas usage.

Going into a lower gear for deceleration reduces brake use, as you get more compression braking with higher RPMs.

Since you rev matched, there is no speed difference across the clutch friction surfaces when it is engaged, reducing / preventing wear. Obviously, this only applies if you did it correctly.

You save gas, because you downshifted and have compression braking longer (time duration) before the idle circuit kicks back in, allowing the engine to spin without fuel longer.

 

amen to that! rev matching only has benefits, as long as you do it right. an easy way to practice double-clutch rev matching is to basically shift in at the midpoint of your rpm range.. that meaning, if your redline is 8000, usually around 4000 is a good place to blip the throttle. but then again, maybe thats just my cars... and, its better to have the throttle a little lower than higher when revmatching, cause the clutch can use the rotational inertia from the shift to match it up a little bit...

 

Yes, it reduces brake use, but it also increases clutch use. As a general rule, in most situations it is best to use the brakes to slow down the car, rather than the engine compression of a lower gear. Brake pads are cheap and this is why they are there.

There are exceptions, though. Long, steep downgrades are one, where you would otherwise be riding the brakes. Another is if you're limping the car home after a track event, with a brake issue (pads or rotors that need replacement), and you're just trying to get it home without using the brakes any more than you have to - BTDT!

 

i only rev match because it makes me feel like i am Ricky Racer tearin' up the highways

that and it makes my car sound cool when i need to downshift

i am still working on perfecting my rev-matching while turning a corner.. sometimes i can't focus on listening to the car/looking at the tach/engaging the clutch/watching where im going all the at the same time. it can get a little scary

 

I don't heel-toe downshift, because I just can't do it (feet too damn big and I can't twist my ankle like that, legs too long and not enough room under the dash), and plus that's really totally unnecessary to do on the street. However I ALWAYS rev-match when downshifting, no matter what.

Sometimes I might use the brakes when approaching a corner, then take my foot off the brake to blip the throttle up when downshifting, and then get back on the brakes if needed or accelerate around the corner. But as for heel-toe downshifting, IMHO that's just showing off if you do it on the street.

 

i am gonna be the n00b here and ask....rev matching is?

 

Planned downshift.
Car is in gear. Depress clutch.
"Blip" throttle to bring engine speed up to exactly what it will be in the next gear down while shifting. (this is the hard part)
Release clutch.

If you do it perfectly, both halves of the clutch assembly will be spinning at the exact same speed when you release the clutch, smoothing the engagement.

It is also generally done during braking, using a "heel-toe" downshift. I rev match on the street in preparation of braking. See traffic ahead start slowing or light turn yellow, rev match the downshift, transition over to brake as needed allowing the compression braking to assist in slowing.

On track, I just start braking, press the clutch, and ram it in the next gear. Yeah, its abusive on the car, but I am not skilled enough to heel-toe shift while threshold braking in preparation for turn in. My poor car...

 

Heel-toeing is gooooooood.

 

Ever since I started driving stick, I always rev matched to slow down for stop lights etc. It doesn't take that long to learn your car and do it perfect almost every time.

The only bad part about it is the couple revmatches where you rev too much or too little and the clutch gets worn. Not only are brake pads cheaper, they are in a very more convenient place to get replaced.

 

rev matching is fun

 

In the simplest terms, rev matching is using the gas pedal when shifting so that the engine revs match the road speed of the car before you let out the clutch. When you rev match properly, the revs don't change (or at least, not much) when you let out the clutch.

When upshifting, the revs are lower after the shift than before. You can time your shift so that you don't have to do much with the gas pedal; since the revs are falling when you take your foot off the gas pedal, you can just let out the clutch (and start applying gas) when the revs reach the level to match the road speed.

When downshifting, the revs are higher after the shift than before. To rev match, you have to give it more gas pedal during the shift, to get the revs up to their higher, matching level.

 

oh wow...i do that and i didnt even think it had a name for it...

Btw thank you both Tunern00b and Nsxtasy for ur kind response...unlike flaming a n00b out..like people in this forum like to do sometimes

 

arn't you spinning the fly wheel w/ no load when rev matching?

and i also suck at it =(

does it really make that much of a difference? or cars arn't super old and i've read b4 just down shifting normally with our cars should be fine