hey wolf hunter I'll send you a PM with some rev matching information.
More cost effective: Braking or downshifting?
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The Rat is the first manual transmission I've had in 30 yrs. It is a weekender, round town driver. I have replaced the clutch from the rear main seal to the pedal arm. Then I replaced 90% of the brake system. Brakes are waaaay easier to fix. Drum brakes will fade badly when over heated. Disc brakes resist heat better. I coast up to red lights in neutral when I think of it, The clutch is a PITA job. The 5 spd Mazda isnt a particularly robust transmission. I replaced the rear U-joint. The center bearing rubber is crushed, So, I dont thrash it with down shifts. A whole bunch of stuff is stressed by a down shift. Brakes are just pads and rotors. That said, down shifts remain an option, so does simply shutting off the engine.
Regarding rev matching. It is fine with straight cog gears, non-syncros. But Helical gears with syncros dont like rev matching. You are just wearing out the bronze syncros.
Regarding rev matching. It is fine with straight cog gears, non-syncros. But Helical gears with syncros dont like rev matching. You are just wearing out the bronze syncros.
I think there is a major difference between downshifting for a long downgrade (1 or 2 shifts max then leaving in the lower gear), vs people who downshift to slow the car down for a stop sign/light. The first I do, the second I do not.
My '93 Mazda still had the original clutch when I got rid of it at 340k+ miles (and when I bought it at 80k the clutch slipped on hard 1-2 shifts).
My '93 Mazda still had the original clutch when I got rid of it at 340k+ miles (and when I bought it at 80k the clutch slipped on hard 1-2 shifts).
Unless you double clutch. But for normal driving, it isn't feasible to do so
sometimes it good to practice that if you ever drive a car and suddenly the clutch goes out, and you done have cash to call a tow truck immediatly
sometimes it good to practice that if you ever drive a car and suddenly the clutch goes out, and you done have cash to call a tow truck immediatly
Say you are in 4th gear at 2k rpm, you down shift to 3rd, and as you let the clutch in, you feel a little jolt and you see the revs jump to 3k.
Right?
Now,
If you REV match, you would apply the throttle to to increase the revs to about 3k BRFORE you let the clutch in.
You would then NOT feel the jolt and there would be virtually no wear on your clutch lining.
You could even take this a little further and Double clutch, Or even Heal/Toe Double clutch to help save the syncros on your transmission.
Taken to an extreme, you don't really need to use the clutch at all, if your REV matching is perfect.
Right?
Now,
If you REV match, you would apply the throttle to to increase the revs to about 3k BRFORE you let the clutch in.
You would then NOT feel the jolt and there would be virtually no wear on your clutch lining.
You could even take this a little further and Double clutch, Or even Heal/Toe Double clutch to help save the syncros on your transmission.
Taken to an extreme, you don't really need to use the clutch at all, if your REV matching is perfect.
Gear down but not so high a ratio that the engine revs five grand . i have for years use trans to supplement. the chassis brakes. i don't know anyone i know. that just freewheels to stops. everyone. i know gears down to help the brakes. i personaly never try more then three grand on downshifts.
ken
ken
You are being fed some good and plenty of terrible information here. One person defends engine braking by making the unsupported claim that it takes very little force to get an engine to spin faster.
If you want to have fun, go to town with engine braking. If you want to run your car economically, use the brakes. Further, if you want to save fuel, try to shift earlier.
I had to unlearn what I grew up watching: high rev shifting, heavy engine braking and incredulous confusion about frequent, expensive clutch replacements.
If you want to have fun, go to town with engine braking. If you want to run your car economically, use the brakes. Further, if you want to save fuel, try to shift earlier.
I had to unlearn what I grew up watching: high rev shifting, heavy engine braking and incredulous confusion about frequent, expensive clutch replacements.
Originally Posted By: wolfehunter
But it sounds like I should be rev-matching? Could someone explain?
Rev-matching is a downshifting technique whereby you raise the engine rpm in neutral (blip the throttle) to match the predicted engine rpm once the clutch is released in the selected lower gear. If you are braking at the same time it's referred to as a "heel & toe" downshift.
Once the technique is mastered there is virtually no clutch wear or shock to the drive train.
On some modern manual gearbox sportscars such as the Nissan 370Z and the new Corvette Stingray they will automatically rev' match (blip the throttle) for you on down shifts.
Of course with dual clutch gearboxes the rev' matching throttle blipping is done for you automatically on downshifts.
Last week I was invited to test the new Jaguar F-Type at Mosport and the only gearbox available is a ZF 8-speed automatic.
It's not a dual clutch transmission per se, but the gear shifts are lightning quick and it DOES blip the throttle on downshifts when braking at high rpms. Being an automatic with a torque converter I don't know if it really needs to do that but it certainly does sound neat.
And btw both the supercharged V6 and V8 Jag' F-Types sounded really sweet especially when lifting the throttle at high rev's resulting in a cocaphony of popping and banging on the over-run.
Nevertheless I'm disappointed a manual gearbox is not offered, that's a deal breaker for me and I told Jaguar rep's so.
But it sounds like I should be rev-matching? Could someone explain?
Rev-matching is a downshifting technique whereby you raise the engine rpm in neutral (blip the throttle) to match the predicted engine rpm once the clutch is released in the selected lower gear. If you are braking at the same time it's referred to as a "heel & toe" downshift.
Once the technique is mastered there is virtually no clutch wear or shock to the drive train.
On some modern manual gearbox sportscars such as the Nissan 370Z and the new Corvette Stingray they will automatically rev' match (blip the throttle) for you on down shifts.
Of course with dual clutch gearboxes the rev' matching throttle blipping is done for you automatically on downshifts.
Last week I was invited to test the new Jaguar F-Type at Mosport and the only gearbox available is a ZF 8-speed automatic.
It's not a dual clutch transmission per se, but the gear shifts are lightning quick and it DOES blip the throttle on downshifts when braking at high rpms. Being an automatic with a torque converter I don't know if it really needs to do that but it certainly does sound neat.
And btw both the supercharged V6 and V8 Jag' F-Types sounded really sweet especially when lifting the throttle at high rev's resulting in a cocaphony of popping and banging on the over-run.
Nevertheless I'm disappointed a manual gearbox is not offered, that's a deal breaker for me and I told Jaguar rep's so.
Most DIY'er can replace brake pads in less than 1 hour and a good normal daily drive pad is less than $50-60 a set. Most DIY'er(myself included) can't touch the clutches, the cost of part and labor to replace the clutch can be several hundreds.
Originally Posted By: TomYoung
You are being fed some good and plenty of terrible information here. One person defends engine braking by making the unsupported claim that it takes very little force to get an engine to spin faster.
So do tell me how it is worse for the engine and clutch than acceleration. The forces are less (you're not pushing hundreds of HP through that clutch). There's less slippage than a stop and go and less power going through it as well.
I'll say I've got many hundreds of K in manual transmission cars, and have never replaced a clutch from wearing out other than the 1st one in my 1st car. And I downshift here in the "mountains" of PA.
I'd rather use the engine and be able to stop at the bottom of the hill with near 100% braking power than have 50% or less because I was riding my brakes. Heck, I even downshift in an automatic. 138k on the "[censored]" CD4E in the wife's Escape and it's fine. And 64k on the 6F55 in the SHO and no issues.
You are being fed some good and plenty of terrible information here. One person defends engine braking by making the unsupported claim that it takes very little force to get an engine to spin faster.
So do tell me how it is worse for the engine and clutch than acceleration. The forces are less (you're not pushing hundreds of HP through that clutch). There's less slippage than a stop and go and less power going through it as well.
I'll say I've got many hundreds of K in manual transmission cars, and have never replaced a clutch from wearing out other than the 1st one in my 1st car. And I downshift here in the "mountains" of PA.
I'd rather use the engine and be able to stop at the bottom of the hill with near 100% braking power than have 50% or less because I was riding my brakes. Heck, I even downshift in an automatic. 138k on the "[censored]" CD4E in the wife's Escape and it's fine. And 64k on the 6F55 in the SHO and no issues.
Rev matching on a synchronized transmission is laughable. If you manually rev your engine what are the chances you will pinpoint the perfect RPM every time, especially with a gasoline engine. If you over rev when downshifting which you will, you're going to make your synchronisers work harder and you may cause shock load damage. Just use one single smooth clutch depression to shift and let the synchronisers do what they are designed to do. Sorry to stray from the point of the original post, but there is a lot of terrible advice on here. As for brakes vs driveline wear, brakes are cheaper than driveline components. I highly doubt the brakes on a compact car will fade to a point that requires engine braking, even on a long steep grade.
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If you're still curious about rev matching and what it is, here's a video of me shifting an old semi of mine. FYI I use the Clutch.
Have you driven a synchro transmission with bad synchros? Rev matching helps it shift, so I don't see how rev matching can wear good synchros more than not rev matching?
I suppose its better still to double clutch but I don't practice it enough.
I suppose its better still to double clutch but I don't practice it enough.
It all depends on the length and steepness of the hill.
I have seen people ride their brakes for miles (and smelt the pads burning)
Sometimes I will gear down, or, let my speed build until I feel I need to slow, then brake quite hard for a short period (max 5 seconds) then gear down. or just let my speed build again if the downgrade is not too long.
The thing is, not to get yourself into a situation where your brakes are fading.
5k rpm on over run seems a little much. Maybe 3500 in a higher gear and a little PERIODIC braking would be better.
I have seen people ride their brakes for miles (and smelt the pads burning)
Sometimes I will gear down, or, let my speed build until I feel I need to slow, then brake quite hard for a short period (max 5 seconds) then gear down. or just let my speed build again if the downgrade is not too long.
The thing is, not to get yourself into a situation where your brakes are fading.
5k rpm on over run seems a little much. Maybe 3500 in a higher gear and a little PERIODIC braking would be better.
What gear does one drive in the most? Top gear. The rest aren't going to wear as much.
Also, it's the forward faces of gears that wear, except when engine braking. More virgin surfaces. Have read of some gearbox designs where overdrive is just on the end of a shaft and it's not supported by as many bearings as the lower gears.
Definitely use it on long grades. I also do the "stab the brake" before downshifting, traffic permitting.
Of my cars with bad synchros, 1st and 2nd go out first. You shouldn't be needing these going over 25mph.
Also, it's the forward faces of gears that wear, except when engine braking. More virgin surfaces. Have read of some gearbox designs where overdrive is just on the end of a shaft and it's not supported by as many bearings as the lower gears.
Definitely use it on long grades. I also do the "stab the brake" before downshifting, traffic permitting.
Of my cars with bad synchros, 1st and 2nd go out first. You shouldn't be needing these going over 25mph.
Originally Posted By: CurtisB
Rev matching on a synchronized transmission is laughable. If you manually rev your engine what are the chances you will pinpoint the perfect RPM every time, especially with a gasoline engine. If you over rev when downshifting which you will, you're going to make your synchronisers work harder and you may cause shock load damage. Just use one single smooth clutch depression to shift and let the synchronisers do what they are designed to do. Sorry to stray from the point of the original post, but there is a lot of terrible advice on here. As for brakes vs driveline wear, brakes are cheaper than driveline components. I highly doubt the brakes on a compact car will fade to a point that requires engine braking, even on a long steep grade.
There's a difference between simple rev matching with a single clutch press and double clutch rev matching. In performance driving rev matching is essential to ensure quick, smooth downshifts in the braking zone before diving to the apex. If you don't rev match your downshifts are going to be too slow and you won't be in the right gear when it's time to accelerate. This is performance driving 101.
Double clutching is when you want to ease the load on your syncros, which helps when you're driving a car with a beat up gearbox. It's actually a pretty neat feeling when you nail the timing and get the revs matched perfectly, the shifter actually feels like it gets sucked into gear with zero friction. It's hard to do consistently, but you only need to be close if the syncros are even a little functional.
Rev matching on a synchronized transmission is laughable. If you manually rev your engine what are the chances you will pinpoint the perfect RPM every time, especially with a gasoline engine. If you over rev when downshifting which you will, you're going to make your synchronisers work harder and you may cause shock load damage. Just use one single smooth clutch depression to shift and let the synchronisers do what they are designed to do. Sorry to stray from the point of the original post, but there is a lot of terrible advice on here. As for brakes vs driveline wear, brakes are cheaper than driveline components. I highly doubt the brakes on a compact car will fade to a point that requires engine braking, even on a long steep grade.
There's a difference between simple rev matching with a single clutch press and double clutch rev matching. In performance driving rev matching is essential to ensure quick, smooth downshifts in the braking zone before diving to the apex. If you don't rev match your downshifts are going to be too slow and you won't be in the right gear when it's time to accelerate. This is performance driving 101.
Double clutching is when you want to ease the load on your syncros, which helps when you're driving a car with a beat up gearbox. It's actually a pretty neat feeling when you nail the timing and get the revs matched perfectly, the shifter actually feels like it gets sucked into gear with zero friction. It's hard to do consistently, but you only need to be close if the syncros are even a little functional.
5000RPM? What kind of hills are you dealing with?! I've gone down a 30ish degree decline with an auto in first gear and still never got to those RPMs (maybe just below that)
On the MTX I shift constantly, and what some may consider needlessly, just for the sake of it kind of like an auto. Never worn out a clutch.
That said, shifting to engine brake doesn't wear the clutch out any more than any other (normal) shift- it's just one quick hit to engage & rest is just pistons sucking on vacuum. And with that being said, I rarely use my brakes at all. Riding brakes going down a hill, that's a big no-no IMO... not a fan of light, extended braking actions at speed
On the MTX I shift constantly, and what some may consider needlessly, just for the sake of it kind of like an auto. Never worn out a clutch.
That said, shifting to engine brake doesn't wear the clutch out any more than any other (normal) shift- it's just one quick hit to engage & rest is just pistons sucking on vacuum. And with that being said, I rarely use my brakes at all. Riding brakes going down a hill, that's a big no-no IMO... not a fan of light, extended braking actions at speed
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