GULAMAN

[QUOTE=missinmahseven]1. Going around the big roundabout in downtown Hollywood (FL) with all 4 tires slipping, tail hanging out, bow pointed into the turn.

2. Stuffing a 70 pound tube amp, a 30 pound preamp, a CDPlayer, a power distro box and a case of CDs in the trunk, plus 2 sixpacks of beer and 1/2 case of bordeaux, then stuffing two huge Klipsch Fortes in the rear seats.
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OK I'll bite: what amp/pre ya got??? 30 lbs for a pre is pretty damn unusual! I'm gonna take a stab: Audio Research??

Ike

I'm more curious about what Bordeaux it was...

saturn

I'm more curious about when and why Hollywood was moved to Florida...

Raptor2k

Why not??????????

Going from 6th to 3rd (and rev-matching) is one of the most fun things I do on most days

saturn

Hey, I don't wanna turn this into a "how to drive manual" thread any more than it already is, but why do you rev match when going from 6-3? Isn't it faster to just throw it down and go like stink? I mean, isn't it going to be in the appropriate powerband no matter what since you're dropping 3 gears?

Raptor2k

Holy crap, this thread made me wince a few times

Saturn - say you're cruising in 6th gear at about 70 mph, so your RPMs are at about...trying to remember...I think it's about 3500 in the rx8. Then you have a sudden urge to go all kamikaze and stuff, so your best way to get all the acceleration you want is to get those RPMs up where the power is (6000ish-9000). So you're going to 'downshift' into third.

The reason why you rev-match has been said a few times already...you don't want to hurt your car. If you just go straight from 6th to 3rd (3500 rpms, and then BOOM, your synchros get you up to 7000rpms), it's hard on the tranny. So yes and no, it will go to the appropriate RPMs if you don't rev-match, but you're going to get a whiplash and you'll really have a feeling that you're hurting your car.

So if you rev-match, by blipping the throttle all the way to 8000 RPMs, then shift into 3rd, your shift will be smooth, and no harm done on the tranny/gearbox/etc. I believe 70mph in 3rd gear is around 7500~ RPMs. So by rev-matching, you're making the illusion as if you're redlining in 2nd gear, and shifting into 3rd (which naturally is a smooth up-shift).

And this applies to every downshift...you want to estimate at what RPM your gear will be in according to your speed. So a downshift from 6th gear to 5th gear wouldn't need 'as much' as a rev match. Knowing what RPMs are appropriate takes getting to know your car.

saturn

Good to know. Thanks for indulging me.

Raptor2k

edited a few things in

btw...I'm not entirely 100% sure what double-clutching is. Anyone? Is it shifting into neutral, clutch out, rev-match, clutch in, shift into gear?

saturn

According to my vast experience in manual shifting, yes. Actually, I Googled it when I heard it in Fast and the Furious -- awesome.

Ike

Double clutching is typically used on an upshift, it's pretty much what you think but rather than bliping the throttle the purpose is to slow the engine revs down so it's speed matches that of the tranny more closely. In a car with synchros it's not needed, though old cars without synchros and usually semi trucks need double clutching in order to shift properly. You can also double clutch on a downshift but rather than letting the engine slow down you increase the revs, but again there's no reason to double clutch, just plain old rev matching is easier and quicker.

People will still argue that if you don't double clutch you will wear your clutch and synchros out quicker. However, with modern cars there's no reason why a clutch and synchros can't last 100k+ miles. I drove the hell out of my DSM, lots of AWD launches with about 250whp, and older technology, I managed to 96k out of my stock clutch. I don't even think I rev matched much back then...

saturn

Check this out: http://domo-kun.nedved.com/avi/18-domo-xanadu.avi

I'm pretty sure I could watch this thing for hours. I find it hilarious for some reason.

Raptor2k

Ah, ok, that's the answer I was looking for. I was pretty sure that's what double clutching was (as far as down-shifting) but thought it was useless, but then I've seen other members here post on how double-clutching is easier on the synchros than straight up rev matching. But I feel/see no difference in how the synchros act...so ok, cool.

Raptor2k

^ya, that's rev-matching

mlaird

If you "rev match" without letting the clutch out, you are only matching the engine speed to the speed of the clutch plate. This doesn't help your synchros at all.

Letting the clutch out in neutral, or "double clutching," lets you spin up the transmission's layshaft so that its speed matches the speed of the new gear you're shifting into, thus saving most of the wear and tear on the synchros. By letting the clutch out in neutral, you're connecting the engine to the layshaft. Only then can the engine spin up that side of the tranny. If you skip this step, the layshaft will be coasting down to a slower RPM and the synchros will have to spin it up to match the lower gear (e.g., 3rd). That is hard to do when you're trying to spin up the layshaft from 3500 rpm (in 6th gear) to 7000 rpm (for 3rd gear).

So "rev matching" is helpful to save wear on your clutch, but doesn't save your synchros. Only double clutching helps the synchros.

Both techniques are most helpful when downshifting (e.g., 6th to 4th). When you're upshifting, the engine and tranny need to spin at a lower speed than before the shift. They tend to do that naturally, so you don't need to do anything special to match the rpm. But when downshifting, they both need to be spinning faster than before the shift, and that's not going to happen without some help.

Michael

Ike

Synchros are there to help you, not the other way around

daisuke

snychros are there to make your shifting possible without learning to double clutch, but if you help them, they'll last longer. that said I don't do it, what's the point.

Curley

Did anybody else catch the irony in the last part of No. 3?

zoom44

whenever i am thinking "im going to need 3rd gear for this" when im in 6th i alway sdrop it to 4th first. then get my revs up to a suitable rpm (i dont look anymore i just "feel it", too busy watching my opening) then when im truly ready to go drop it from 4th to 3rd and slam the throttle- its very very satisfying D

Krankor

Sigh. Another member of the my-transmission-is-made-out-of-crystal school. Quick informal poll: How many people here (who don't double-clutch) have ever had a problem because their syncros wore out? Vote me a big no, in 5 manual cars so far.

mlaird

Just for the record, I didn't say how often anyone should use these techniques, if at all. My point was that rev matching is different than double clutching.

However, just to throw some gasoline on the fire :-), have you ever watched one of the many videos where a good driver drives an RX-8 and they have an inset picture of his feet? Have you ever seen them heel-toe? Why do you think they are doing that?

Hint: they are rev matching in order to downshift smoothly and avoid upsetting the balance of the car while they are going through a corner quickly.

The bottom line is that if you understand the point of these techniques and what they are doing, then you can decide if it is appropriate to use them or not.

Michael

Krankor

heel-toe is not the same as double-clutching.

mlaird

Sorry -- I was typing in a hurry. You can actually use heel-toe to do either rev matching or double clutching, although rev matching is more important in the scenario I was describing. I've corrected my post above to say what I meant.

My point remains the same -- you need to understand the purpose of each technique to decide if it is appropriate for you as you're driving.

Krankor

Well I'll certainly agree with that.