I'm fairly new to the manual transmission. I've owned a brand new black Enthusiast since last Thursday and I absolutely love it.
But I have some technical questions regarding the manual shift.

A friend told me that gearing down when approaching a stoplight (or similar) is ok for the car. Even if it is, I just won't do it. It seems to be bad because of the car suddenly pulling back. Personally, I'd rather my brakes suffer than my drive train. I'd like some further information on this if anyone can supply it.

How fuel economical is a manual compared to an automatic? Please elaborate.

Thanks guys.

 

I never downshift when slowing at a streetlight. This makes no sense. I usually do use the engine to help me brake, but only in the gear I was cruising in. Once the RPMs drop, I put the car in neutral.
Traditionally, manual transmission cars are more fuel efficient. This is because the transmission forms a direct mechanical linkage between the engine and the wheels. On automatics, power is transmitted through a fluid coupling (an oil bath of sorts), so there are more drive-train related power losses. All modern automatics attempt to improve fuel efficiency by locking up at cruising speeds in the top gear or two. On the highway, there's really no difference in economy. Automatics have come a long way, and are catching up rapidly in terms of efficiency.
Mika

 

Nothing wrong with down shifting as long as you don't overrev it into the redline area.

I don't downshift at lights/stopsigns but do on the twisty turny roads if I'm in the mood to play junior road racer. LOL.

Only problem I've encountered is being sure I don't go into second instead of 4th comming out of 5th. At least for me, my "touch" is off on finding 4th and I have put it in 2nd a couple of times. Immediately recognized the mistake and threw in the clutch.

 

what he's saying is called engine braking, and its a viable option. on the track this is often used since its heat free braking. however for the streets, brakes are easily replaced, clutches are not.

in the perfect world, youd rev match when you down shift. but if your anything like me, thats easier said than done. so you end up slipping the clutch a bit(and get the jerky movement) this isnt good.

also never downshift to 1st unless your going <5mph atleast, and if your going to be stopping, wait till then.

 

or drivetrain.....if u pay attention to engine rpm and vehicle speed relative to the gear u are in and the one you are thinking of downshifting to.....just make sure u downshift in order....its not adviseable to downshift from say, 5th to 2nd......let common sense prevail......your brakes will indeed last longer.....

 

I've always downshifted in past cars and will in the Z when it arrives. I never downshift to 1st though. I've never seen symptoms of accelerated wear and I've had my current car 8 years.

The other advantage apart from engine braking is you're always in the correct gear if you need to get on it again.

 

I downshift all the time, mainly to practice revmatching which is essential for smooth high speed turn exits.

 

Can someone explain the term "rev matching"?

 

Put simply it's when you blip the throttle while downshifting to match the revs. If you don't do this as you let the clucth out the revs will come up. The objective of rev matching is to blip the throttle so that as you release the clutch the revs are already at the point they would've rised to if you hadn't blipped.

Make sense?

 

My experience has shown that using the engine to slow the car results in fewer clutch replacements. Downshifting is an integrel part of owning a car like the Z. What do you do if you come to a 90' right hand turn - stop? - or down shift from 3rd to 2nd and drive throught it? Your choice.

 

Thanks, apsilon. Think I got it!

 

yeah downshifting can be handy sometime.. but i personally don't down shift at a stop light. I just usually downshift exiting the freeway at 80mph anyways.. i like to downshift when the rpms are around 2K-2,5K.. so it doesn't rev that high goin into the lower gear.. haven't got the hang of rev-matching yet

 

Takes some practice and experience before it comes naturally. Also helps if you don't have a banged up ankle like I do.

To be honest with modern transmissions it's really not necessary. I could be wrong but I'd say one of the reasons it came about was on trannys without syncros or even early trannys with them. It does reduce stress on syncros more than anything.

 

So are you saying that it is bad to downshift without rev matching? Or just lettin out the clutch to fast when downshifting?

 

Not really a good or bad thing, just a matter of smoothness, of course if you're downshifting too low and redline your engine that can't be too good, neither can slipping your clutch too much. the best test is to keep a constant speed and select different gears, so say 40mph in 3rd gear is 4000 rpm and in 4th it's 3300 rpm, so when you're downshifting and revmatching, at 40mph in 4th, clutch in, downshift to 3rd, blip throttle to 4000RPM, release clutch for smooth transition to 3rd gear. Basically, that's how it works.

 

I don't think it really matters now. I was referring to transmissions of 30+ years ago without syncros. Just a bit of trivia (although I'm not 100% I'm correct in that theory).

Just enjoy the drive te way you want. I personally downshift and always will.

 

actually, those are 2 different things, rev matching can help both, but synchros are the only reason you can downshift at all without either rev matching or double clutching. now once youve actually SHIFTED, then you have to let out the clutch, which can just put wear on it if it rubs too much(synchros are not involved in this part of the process at all); of course this is no different then getting the car going when you slip the clutch to get moving, its just better to minimize the amount of slipping you do.

 

I don't know about you but I rev match as I shift ie as I move through neutral. You're wasting time if you shift fully into gear then blip the throttle. Different tehcniques I guess.

Anyway that's why I mentioned the syncros (or lack thereof as the case may be). On a similar note that's why truck drivers used to (still do?) double clutch. A form of rev matching.

 

Think of the drivetrain as three sections:

1. The engine and flywheel assembly
2. The clutch disk and input side of the transmission
3. The output side of the transmission and the rest of the drivetrain.

The first two sections are locked together when you let the clutch out. The last two sections are locked together when the transmission is in gear.

The link between the first two sections is the clutch, and it's designed to allow gradual engagement by slipping. No problem there, a clutch will last a long time under the conditions of normal driving, and it will probably last longer than you think even when you are abusing it.

The link between the second and third sections is a direct mechical link. Its the OD teeth on the gear engaging the ID teeth on a ring that is locked to the output shaft (and it's not the teeth around the outer perimeter of the gears that you are engaging when you shift, it's actually more like splines on the side face of the gears that engage. Hard to describe without a picture). In order for those teeth to engage, the input and output sides must be spinning at pretty much the same speed. That's where the syncros come in.

Syncros use an angled surface to gradually create friction between the two sides and bring their speeds together. If you take your time and don't force the gearshift lever, there is a little friction created and the gear slides in. If you are shifting hard, then your force on the gearshift lever causes a lot of friction which matches the speed of the two sides faster. That is what wears out syncros. The syncro ring itself is usually made of a softer metal like brass (someone correct me if the Nissan is different). The mating surface of the syncro wears out and can no longer provide the friction necessary to match the speeds, and ultimately you grind more gears unless you shift easy all the time.

Blipping the throttle with the clutch pushed in doesn't help the syncro match speeds because the link between the engine and the transmission is broken when you push the clutch in. So rev'ing the engine while downshifting just eliminates the lurch associated with a badly matched shift. The lurch will send you spinning if you are already on the edge of traction, because it's sorta like yanking the emergency brake until the engine speed has a chance to catch up.

Double clutching does help the syncros. Assume you are shifting up while accelerating. At the top of first gear the engine, input side, and output side of the tranny are all spinning fast. You push in the clutch and the engine slows down, but the input side of the tranny is still going fast because it is locked to the output side. So to release that lock you shift into neutral. Now the input side is just freewheeling, but it's doing so about as fast as it was. If you continued shifting into second, the syncros would have to exert friction to slow down the input side of the tranny to match the new gear ratio of the output side. But, if while in neutral you let out the clutch, you have now used the slow spinning engine to slow down the input side of the tranny. Then you push the clutch back in, and shift into second. The syncros probably had to do a little work, but the majority of the speed difference was absorbed by the clutch and it's more than up to that task. So now the input and output sides of the tranny are locked together by being in second gear, and the engine is spinning about the right speed, so you let out the clutch and enjoy and nice smooth shift that was easy on the syncros.

Personnally, I match revs on downshifts to avoid upsetting the car, and I never double clutch because modern trannies don't require it and I figure one screwed up double clutch shift will do more damage than 100 normal shifts. Also, double clutching is slower than normal shifting unless you are really good. During normal driving I shift slow enough so that the syncros aren't overstressed. When I want to haul ***, then I yank it into gear pretty hard and assume that the tranny was designed to handle it for as long as I'll have the car.

How boring was that answer?

Desmo

 

I give you some useless points good sir. very informative, I enjoyed it.