Some Hypermiling questions

[Fat Charlie]

Originally Posted by groar

I never rev matched on any car I drove, gasoline or diesel, and never heard about it before reading hypermiling forums.

Is it how old cars (older than late 70's) had to be driven or is it an hypermiling trick ?

May be when decelerating as the rev after the down shift is higher than before; noticeably when racing as the rev will be as high as possible to have more engine brake.

In fact the single time I hear about rev matching is when you want to drive a manual and the clutch doesn't work anymore...

TIA,

Denis.

I've never really heard the term much outside of hypermilers and riceboys. Hypermilers have to rev match because they're going into gear from neutral so much, while riceboys think it makes them sound more 1337 than simply saying "downshifting." But you've either been rev matching every shift or you've been using your clutch as a very expensive brake pad. It's something you automatically do when shifting normally, but it takes a lot of focus when hypermiling. There's no intuitive "just a little bit" of gas you can give it to match revs when you've been coasting at 800 RPM for the last minute. Now you need to watch your speed and figure out where you need to put your revs to get into the gear you're looking for.

[vskid3]

Originally Posted by PaleMelanesian

I'll weigh in this. My next-gen DX should be similar in gear ratios and engine power to yours.

Here's how I handle my shifts. You can shift even sooner but these are close enough and easy to remember.

1st: just enough to get rolling for a few seconds. This gear gobbles gas so get out of it.
2nd: up to 20 mph
3rd: up to 30 mph
4th: up to 40 mph
5th: anything above that

I believe the 5th and 6th gen DXs and LXs were nearly identical for gears and power, my parent's have a 94' LX that drives almost exactly like my 97', except that the clutch engages earlier (I was used to only pushing the 97's clutch halfway to shift).

Those are the speeds for acceleration, if you are cruising on flat or slightly downhill ground, you should be able to use the next higher gear (like at 35, I usually shift to 5th if I know I won't be needing any power soon).

[Kodak]

But Fat Charlie, what about the role of the synchronizers?

I'm awful at rev matching. Takes me too long. I want to get better at it though.

Edit: Takes too long when I'm trying to rev match a downshift, not when trying to rev match from N to a gear (although I only occasionally do it).

[PaleMelanesian]

That's true. Those gear shifts are for acceleration. I exclusively drive pulse & glide so that's all I'm ever doing. If you're willing to do the work, it's the most fuel-efficient way to drive.

For steady speed, use the highest gear that can maintain speed. My car can do that in 5th as low as 25 mph.

[Fat Charlie]

Originally Posted by Kodak

But Fat Charlie, what about the role of the synchronizers?

The synchros let you engage gears without grenading the whole box. Now that the gears are all meshed and doing turns for 40 MPH, your crankshaft is still spinning at idle. You need to bring your engine revs up to match what your transmission is doing or your clutch will have to do it for you, acting as a big, expensive brake pad.

Rev matching coming out of a glide can't take too long. Except for an emergency it should be pretty well planned- you've got your whole glide to think about it. Pick your re-engage speed before you decelerate to it and work to meet it: I'm decelerating pretty quickly through 40 so I have to get ready. I'm going to jump back in at 30 and I want to be in 3rd gear for a quick, strong pulse so I need to be at about 2500 RPM. And... go!

[Kodak]

Ah, okay. I didn't realize that.

Every heard of the abbreviated method, in which you simply clutch-in, downshift the gear shifter, and blip the throttle (rather than going into neutral) before letting the clutch out?

Is this method inadequate? It must be inferior somehow, or who would do it the typical (longer) way?

[Fat Charlie]

Okay, what you're thinking of is "double clutching." I've never driven an unsynchronized manual, so I've never had to do it. That's where you go fully into neutral, rev match then hit the clutch again and shift into gear.

With a synchronized gearbox you just shift normally (your abbreviated method). Upshifting you match revs without trying because the engine slows when you lift off the throttle and hit the clutch. Downshifting you match with that throttle blip. It's almost as easy as on the upshift, but it does take a little more involvement on your part.

[larrybuck]

We are trying to help a raw beginner here! The advanced stuff might be a bit much at first.

My daily driver is an '87 Honda CRX. 1st gear just to get you rolling...2nd to 3rd at around 15mph...into 4th 22-25mphish.... into 5th by 30mph on downhill or level roads, if I'm slightly accelerating to approach a slight hill, I might wait on 5th until 35mph.

You are on your own on hills... from your motorcycle, just remember not to let it bog down. For the most part....forget about downshifting... go into neutral.. practice coasting toward stoplights, and signs, as much as following traffic will allow. You MUST learn to MIRROR DRIVE alot to help yourself set up your next best move!

Try to find good 30-45mph. roads in your area to take that have the fewest stop/light/signs... just work on being Smooooooth!!!

Try to use the brakes hardly at all.... anticipate traffic problems ahead, so you are never surprised into having to brake hard.

rpms.... most of my upshifting is between 1,200 and 1,500...very mello. If you commute in a busy place during rush hrs, people behind you aren't going to appreciate your econo efforts! Be ready to back off perfection, or grow a hard turtle shell.

Don't go over 50-55mph anywhere if you can help it.

Think about bumping up your tires to maybe 5-7 psi above what the sidewall cold max. says on the tire. That's not too much to ride real rough, or wear the tires out too fast. It does mean to remember common sense to NOW go into wet corners a little slower than you used to....my latest idea for a bumper sticker would be this: Friends don't let friends do LATERAL SCRUB!!

Have fun and practice, practice, practice!!!!! Never use the clutch like a brake!!

[bhazard]

Sometimes Im in 4th by 15 and 5th by 25. But then again my power/weight ratio is a bit excessive, and I dont get the MPG a stock car gets either...

[Big Dave]

I usually shift at 1200 RPM.