Do You "Blip" on Downshifts?

[TrickVert]

I have always "blipped" the throttle on downshifts to match engine speed to the next gear, as I think it's easier on the clutch, brakes, and the drive train in general. I had someone say to me it's not necessary, and could actually be worse(?) than not doing it.

I know in racing situations it smooths the transition and is nearly mandatory for good control.

What say the masses? Pros - cons?

Andy

[BFINCH]

When i did have a manual car i "blipped it" no clutch most of the time

[ermcgrat]

Originally Posted by BFINCH

When i did have a manual car i "blipped it" no clutch most of the time

No clutch? :O

Sometimes I would if I wasn't feeling too lazy. I'm not amazing at heel-toeing it so sometimes I just wouldn't downshift much or not try to rev-match it.

[TrickVert]

Originally Posted by ermcgrat

No clutch? :O

Sometimes I would if I wasn't feeling too lazy. I'm not amazing at heel-toeing it so sometimes I just wouldn't downshift much or not try to rev-match it.

Good point, I wonder how many people just coast without down shifting at all or until they're moving slowly enough it doesn't matter.

Maybe that's what this guy was getting at. Clutch replacement $$ > brake pad $$, but that shouldn't be an issue if you match speeds properly.

Andy

[ermcgrat]

Yea I've never heard of no clutch on downshifts, maybe on upshifts...

And like yous aid, I'd normally just coast down until rpms were low enough it didn't really matter. Under hard/emergency braking there's no way I could be fast enough to downshift and be useful, it's just mash clutch and brake pedals. So that doesn't leave a whole lot of times I felt the need to downshift and rev match on the street

[BFINCH]

sloppy T5's = clutchless down shifts...

[TrickVert]

Originally Posted by BFINCH

sloppy T5's = clutchless down shifts...

Or is it clutchless downshifts => sloppy T5's

g --> chicken --> egg --> chicken --> egg --> ch...

Andy

[MFE]

There's actually no harm in rev-matching. You're right, it's easier on the drivetrain, and it's less likely to upset the car. Your critic must have confused it with double-clutching, which is releasing the clutch as the shifter passes through neutral, then depressing it again before moving it to the desired gear and releasing the clutch again. Rev matching and double-clutching are not the same thing. You don't have to double-clutch in order to rev match, you can simply blip the throttle as the shifter is between gears without releasing the clutch until the next gear is engaged, but a lot of rev-matchers also double-clutch.

[capri]

Originally Posted by MFE

There's actually no harm in rev-matching. You're right, it's easier on the drivetrain, and it's less likely to upset the car. Your critic must have confused it with double-clutching, which is releasing the clutch as the shifter passes through neutral, then depressing it again before moving it to the desired gear and releasing the clutch again. Rev matching and double-clutching are not the same thing. You don't have to double-clutch in order to rev match, you can simply blip the throttle as the shifter is between gears without releasing the clutch until the next gear is engaged, but a lot of rev-matchers also double-clutch.

You're right on the money MFE. Sometimes I just rev match by blipping, other times I double clutch... usually at higher rpms so I can get it in the next lower gear faster and not stress the syncro. It all depends on the situation.

[slowfive0h95]

I blip it.

I rarely use my clutch though on upshifts or down shifts...And I dont exactly have a sloppy t5 either...unless you call a gforce a sloppy tranny.

[TrickVert]

I guess if you rev match perfectly, no-clutch shifts wouldn't be a problem. I think I'd be riding against the syncros until things meshed, though, and would mess things up eventually.

Andy

[Floordford]

Do you ever upshift and blip?


http://www.youtube.com/watch?v=GMc2RdFuOxI
2:25, 3:52, 4:19, 6:30 (it sounds like he hits the governor before he shifts), 6:37 (he does it again), 6:52....enough examples.

Ive tried this and it pretty much just wastes time. It does sound kinda cool if you can do it right and you are a die hard Bullit fan.

[eleanorfox]

i do it out of habit. my dads neon grinds 2nd if you don't blip it a bit on downshifts.

i drove that car all through high school and still borrow it from time to time so i find myself doing it on my mustangs as well.

[TrickVert]

You might be right, MFE. (Big surprise.) He could have been referring to double-clutching.

IIRC, the DC action brings the synchros in line a bit faster, and as a result, might prolong them?

Andy

[Stang777]

I coast down alot and don't do much downshifting unless I need to accelerate hard.

[takdashark]

Blip it, then mash the gas...... or the brakes i guess:-)

[MFE]

OK, I got writing and I couldn't stop.

Double-clutching a downshift takes the job of getting the clutch disc and cluster gear up to speed off the puny syncros and onto the clutch itself, thereby massively extending the life of the synchros compared to not double-clutching.

Why? Let's talk about how the T5 works, understanding that the T5 is a conventional "syncromesh" transmission where all gears are meshed at all times, with friction syncrhonizers that get the assemblies to the appropriate speeds during gear changes, not a dog-ring transmission which operates differently.

A little drawing from Hanlon Motorsports:

In a syncromesh transmission, you have the input shaft (1) that's splined to the clutch disc. Any time the clutch is engaged (foot off the pedal) with the engine running, the input shaft is turning. The input shaft and the mainshaft (9) are co-axial, but not connected. The input shaft is permanently engaged with the cluster shaft (10), off to the side of the mainshaft of the transmission and so named because it is a single, solid (and heavy) piece containing a cluster of all the drive gears for the transmission.

The mainshaft is connected to the driveshaft which is connected to the diff which is connected to the axles, so the mainshaft is turning at road speed x diff ratio any time the car is in motion. The cluster shaft and driven gears (3, 4, 6, 7, and 8 in the picture) are turning at engine speed. The driven gears it meshes with are permanently engaged to it, but they spin disengaged on the mainshaft until one of them is locked to it by a slider (2 and 5), which rides on a hub splined to the mainshaft, so the sliders are also always turning at mainshaft speed.

The sliders are pushed back and forth along their hubs by the shift forks, and thereby engage gears on either side of the sliders, and each gear operates at a different ratio.

When you change gears (briefly described here ), a shift fork pushes the slider one direction or the other, and on either side of the slider is a synchronizer assembly. Teeth on the slider gears engage teeth on the synchro assembly first, before they engage teeth on the face of the selected driven gear. So what happens is, the little synchro ring achieves slider/mainshaft speed immediately, then it applies pressure through friction material to the face of the selected gear, bringing it to proper speed just before the slider continues over to engage the gear. Poof, everything is synchronized.

But remember, the gear is meshed with the cluster shaft which is meshed with the input shaft which is splined to the clutch disc. The synchro isn't just getting one little 12-oz gear up to speed, it's getting several pounds of cluster, input, and clutch disc to the proper speed.

If there were no synchronizer, and in the old days and in still today in many truck transmissions there weren't any, you'd have to have another way of getting the selected gear, the cluster, the input shaft and the clutch disc to the proper speed before the gear could engage. In other words you'd have to manually syncronize the speeds of the assemblies yourself.

You'd do this by pressing the clutch, releasing the clutch in neutral so the cluster was engaged to the engine again, matching the engine speed to the appropriate level, then pressing the clutch, engaging the gear, and releasing the clutch again, so the entire assembly is now tied together and nobody ground any gears. That's double-clutching.

If you think about it, we're asking quite a lot of a little synchronizer ring with a little friction matieral on it, and it's arguably easier to do when moving up the ratios because all you're asking it to do each time is slow the assembly down, which it naturally wants to do anyway.

However, on a downshift, the the cluster/input/clutch disc/engine assembly needs to speed UP. That's asking more of the synchros. If you don't double-clutch a downshift, the synchros have to do ALL the work of getting the cluster and the clutch disc up to speed. If you pop the clutch out while the shifter goes through neutral and you blip the throttle to match engine revs to the upcoming mainshaft speed requirement, you're using the clutch to get itself and the cluster gear up to speed, instead of a tired little synchro.

Double-clutching a rev-matched downshift therefore takes a lot of wear off the syncros. You pay for it in terms of some additonal wear on the clutch actuation assembly, throwout bearing and pressure plate.

Now, everybody wants to zing 6000-RPM rev-matched downshifts, because it sounds so ####in' cool and is satisfying to accomplish when done correctly. But...all we're doing is matching engine speed to required road speed, right? If you're patient, you can accomplish the same thing without a blip and without a double clutch, if you just push the clutch in near the bottom end of the gear, and wait until road speed falls to the idle speed of the engine for the next appropriate gear

But screw that...here's a little music from when I used to mount mic's above the tailpipes

http://videos.streetfire.net/video/c...d-on_68540.htm

[capri]

Very correct once again MFE ^^^^^^^
I have tried explaining all the above to many of my friends who "think" they are masters of driving a stick car, but couldn't get them to understand. Even though it took a small novel to spell it out, you obviously know how and why double clutching is more effective than simply rev matching. The video of you keeping pace with that WRX STi on the track was proof enough to me that you know how to drive a stick.

[NUTTSGT]

Yes I blip it, when the car is drivable. It also has a G-Force with no syncros.

[TrickVert]

Great explanation, MFE. Thanks for the lesson! Now, was that video with or without double-clutching?

Andy

[MFE]

I typically double-clutch on the track unless I blow my corner entry and get too busy controlling the car, in which case I put the downshift on the back burner and take it just before I need to accelerate again.

[Hawaii_5.0]

I usually blip it, at least if I'm actually downshifting for the engine braking I do anyway. Easier on the drivetrain, and it's fun.

[J. Kidd]

Yes. Always. On all my vehicles (except the 4Runner - that's an automatic).

Much easier in my BMW than it is in the Mustang, though. Smaller motor, less torque, closer transmission ratios and lower (numerically) rear gears (along with closer pedals) make heel-toeing MUCH easier...plus the car is silky smooth compared to the uncivilized Mustang - but I get pleasure from driving them both.

Learned how (and why) at a Skip Barber driving school YEARS ago and have been practicing it ever since.

And like MFE said, I always try to do it .... unless other more pressing issues present themselves and it needs to take a back seat to keeping the car on the road and/or undamaged

[Mustang5L5]

I've always rev matched my downshifts.

I used 2K as the magic number. Blip up to 3K and let out the clutch and keep going

[flyersfan362]

I know the 370z even has rev/match technology. It basically "blips" the revs up on downshifts pretty cool.