Skip Shifting

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theholycow
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Re: Skip Shifting

Post by theholycow »

I doubt 2500 is too early for your purposes.

In my 2008 VW, short shifting was much more effective than skip shifting, although I have doubts about my data; the car was brand new and still breaking in and every tank was better than the last, and I never did go back to retry skip-shifting.

Really, just keep a good gas log and try different strategies repeatedly until you find what works best for you.
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Re: Skip Shifting

Post by LHOswald »

six wrote:I sometimes skip-shift, but to minimize wear, I either double-clutch, or I shift through the gears sequentially while holding the clutch down until I reach the desired gear. An example of the latter, let's say I'm just putting along in city streets, and want to shift from 2nd to 4th: I step on the clutch and hold it there, move the stick from 2nd > 3rd > 4th, release clutch. That way, I am still skip-shifting as far as the engine, clutch, and wheels are concerned, but spread out the synchro wear.
i thought this technique was common knowledge? i remember SCREAMING at my friend (drives an MR2) for skip shifting from 2nd to 5th while i was in the car with him...right after we got done rebuilding his transmission. talk about epic f*cking facepalm. ironically enough the only synchros that were bad were 2nd and 5th. we replaced them all anyway.
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Re: Skip Shifting

Post by Rope-Pusher »

^ 2nd gear synchro typically gets the most use, since you often upshift or downshift into 2nd, while you can only downshift into 1st and even then many/most shifts into first are from a stationary position.
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Re: Skip Shifting

Post by ClutchFork »

Interesting. So skip shifting is hard on the syncros, eh? Why would it be hard on my 4th gear syncro to enter 4th at 45 mph from 2nd when that is the speed limit, so if I had used 3rd, I would still be entering 4th at 45 mph?

By the way, if it is hard on the syncros, then my skipping 3rd is good because I don't think my 3rd gear syncro is as good as the others. Sometimes it makes a brief clashing noise if I up shift too fast into 3rd.

Also interesting are the couple of posts (copied below) noting that skip shifting is done for fuel economy, but lately everyone is telling me I need more gears to get better fuel economy. Image
Tups wrote:They teach skip shifting in our driving schools as a fuel-saving measure.
Shadow wrote:... In most cases, the manufacturer is trying to avoid gas guzzler status (and tax), so they put a skip-shift feature in the car to bring up the fuel economy rating a little bit over the gas guzzler threshold. ....
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Re: Skip Shifting

Post by IMBoring25 »

Starting with tankinbeans and moving down, skipping the quotes because context is obvious:

At 2500 you are almost certainly shifting much later than the equivalent automatic would be for gentle acceleration on level ground. My dad inculcated me with the opposite prejudices and it's not uncommon for me to shift to put the engine at or near idle in the new gear when accelerating lazily on level or downhill ground. You're not hurting anything and are probably actually shifting too late for optimum economy, but in the name of harmony you could always shift later when your dad is in the car.

In theory, there's one optimum combination of throttle opening and gearing per speed and desired rate of acceleration. Typically this would suggest more gears = good in real-world driving, provided you select the gear nearest this point. That's the problem, though...Most people shift too late. At the speeds CAGS activates it is likely it causes most drivers to do most of their accelerating at a lower RPM than they otherwise would (at least until they get used to the system, which the CAFE testers would not have the opportunity to do). But as thc indicated, trial and error should reveal any quirks with your vehicle if you can do a bunch of tanks that are otherwise identical.

In theory, if you have a timing worked out for sequential shifts that lets the shifter drop right in with no synchro resistance and you use the same single-clutched timing for a block shift, since the engine/input shaft are starting at a higher RPM, you will wind up moving the shifter while the input shaft is still spinning too fast for the new gear and letting the synchro drag it down. That said, the input shaft doesn't have a whole lot of inertia and the error is in the "right direction" as it will be spinning down on its own as well. It should not be a huge deal in most cases and you can make it no deal at all by either double-clutching your block shifts or putting in a little extra delay in neutral before you try to move the shifter into the new gear.
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Re: Skip Shifting

Post by theholycow »

InlinePaul wrote:Interesting. So skip shifting is hard on the syncros, eh? Why would it be hard on my 4th gear syncro to enter 4th at 45 mph from 2nd when that is the speed limit, so if I had used 3rd, I would still be entering 4th at 45 mph?
Road speed is only half of the equation. The other half is input shaft speed.

If you come out of 2nd at 4000RPM and enter 4th at 2000RPM, your 4th synchro needs to do 2000RPM worth of work. If you come out of 3rd at 3000RPM and enter 4th at 2000RPM, your 4th synchro only needs to do 1000RPM worth of work.
By the way, if it is hard on the syncros, then my skipping 3rd is good because I don't think my 3rd gear syncro is as good as the others. Sometimes it makes a brief clashing noise if I up shift too fast into 3rd.
I bet this is by far the most common reason for skip-shifting...nobody wants to use a grindy gear.
Also interesting are the couple of posts (copied below) noting that skip shifting is done for fuel economy, but lately everyone is telling me I need more gears to get better fuel economy. Image
Skip shifting is not a universal answer to fuel economy.

CAGS (and whatever other forced skip-shift "features" might exist) is a dodge, attempting to abuse a technicality. It's probably not actually going to increase real world fuel economy. It's designed specifically for the CAFE test cycle. Ford dodges the chicken tax by building Transit Connect vans with seats, then ripping out the seats between import and sale so they can be sold as trucks...that doesn't mean seats are better for shipping vans, it's just a smart aleck end-run around a technicality.

For real world fuel economy, voluntary skip shifting can work, but certainly not in all (or possibly most) situations. It varies widely by vehicle, driver, roads, traffic, etc. Generally it's better to keep the engine at its most efficient RPM and throttle.

However, what "everyone is telling you" (regarding the 8 speed thread) is that more gears are better, not more shifting. Let's say for a moment that skip shifting is better for your specific situation. If using only 4 gears for acceleration is better, having 8 means you can choose the most efficient 4 when the situation changes a little bit. It also provides more options for steady-speed cruising; you might skip-shift while accelerating, but then have a most efficient gear for cruising at 40mph and another for cruising at 50mph, where with half as many gears you might have to use the same gear at those speeds.

More shifting is better, though, because it's fun! Image
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Re: Skip Shifting

Post by ClutchFork »

I would think on the skip shift that the input shaft speed will drop pretty quickly unless the engine is plagued with rev hang.

To get optimum fuel economy one would need to know the ideal rpm to run, else they may run a gear at a higher rpm, or too low possibly lugging. I think some people will run the gears out harder for fun and not get all the fuel economy benefits, as it seems the worst fuel economy comes in accelerating.

I can't imagine more gears in the Ranger. If I had a one liter engine I might like having 8+ gears.
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Re: Skip Shifting

Post by tankinbeans »

On the contrary, 8 gears in a small engine might not work some more. Wouldn't that take you way out of your already meager power band, unless your final gear is the same as a typical 5th but with more in between?
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Re: Skip Shifting

Post by Rope-Pusher »

^ Depends on how the 8 available ratios were spread. With a 12:1 spread, prolly not enuff motor. With 6:1 spread, might be a good launch ratio, a good highway cruise ratio and 6 others closely spaced in between - perfect for smallish motor?
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Re: Skip Shifting

Post by ClutchFork »

There has got to be a point where it becomes no fun. To me, part of the fun is running each gear out. If I have 6 gears to go through to get to 45 mph, there is no fun unless I skip two gears at a time. Skipping gears is easy but it is nicer to run the H pattern instead of some strange convoluted pattern through an HH pattern.

In the total picture, it is not the shifting, nor the clutching, nor the launch, nor running out the gears; rather, it's all of them!
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theholycow wrote:Why in the world would you even want to be as smooth as an automatic? Might as well just drive an automatic...
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Re: Skip Shifting

Post by theholycow »

InlinePaul wrote:I would think on the skip shift that the input shaft speed will drop pretty quickly unless the engine is plagued with rev hang.
Sure, if you double clutch.

If you don't double clutch it doesn't matter what the engine does, the input shaft only slows according to its own drag.
InlinePaul wrote:There has got to be a point where it becomes no fun. To me, part of the fun is running each gear out. If I have 6 gears to go through to get to 45 mph, there is no fun unless I skip two gears at a time. Skipping gears is easy but it is nicer to run the H pattern instead of some strange convoluted pattern through an HH pattern.

In the total picture, it is not the shifting, nor the clutching, nor the launch, nor running out the gears; rather, it's all of them!
For me, it is the shifting and clutching. I don't get any satisfaction from hearing the engine rev up, and I certainly don't get any satisfaction unique to manual transmissions from it...I have no difficulty making an automatic rev to redline. I like the feel of the shifter as it encounters the synchros and then engages the gears, the movement of the clutch pedal, and the feel in the seat as I interrupt and resume power flow. More gears is more fun for me.
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Re: Skip Shifting

Post by daleadbull »

As far as skip shifting and syncho wear; as long as we take our time moving the shifter and not rush it, there shouldn't be any additional wear. Is that correct?
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Re: Skip Shifting

Post by theholycow »

Shouldn't be any excess wear. Certainly no wear to worry about any more than you'd worry about a single-clutch downshift.

No matter how you slice it, if the synchro has to do more work it will have more wear. They are designed to last the life of the car with the kind of shifting done by the sort of people who don't visit StandardShift.com, so do not worry.
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