taller tranny

[MetroMPG]

(* motivated by SVOBoy's Project: KDA (Engine and Auto to Manual Swap (http://www.gassavers.org/showthread.php?t=911&highlight=kick+dan%27s))

Exactly when I would make the time to do this, I don't know. I already have too many projects stacked up in a holding pattern over the airport.

But, I figure: start this thread and maybe it'll motivate me or someone else.

[SVOboy]

Man, your gear ratios suck! :p

Anyway, I'd def do it, I'm already loving the rpm change from my own conversion. With this you can go faster at the same rpm level, which doesn't mean you should go faster, but means that places where you might be forced to go faster will not take such a toll on your total FE.

[MetroMPG]

Man, your gear ratios suck!

I'm not surprised. Why do they suck? I'm guessing it's because my torque sucks.

[95metro]

Man! I am so jealous of your guys' garages and wealth of junk/spare parts. If I had the parts I would have no where to put them...I need a garage! :mad:

[MetroMPG]

Garage, schmarage. The transmission isn't very big, and it only weighs 65 lbs. You could easily put it (hide it) on the shelf in a coat closet. :D

[95metro]

Hmmmm...

*considering it*

[MetroMPG]

Some more to think about: this car's 0-60 time in stock form is about 15 seconds. This swap will make it ... much worse! One teamswift member found this swap intolerable.

Then there's the issue of the speedometer/odometer being off. Can compensate for that in the ScanGauge though.

[MetroMPG]

.I need a garage! :mad:
Put stuff in the Aerostar!

[95metro]

So it's just the torque difference between the 3 and 4 cylinder that makes it bearable with the 4? Any possibility of keeping the 3-cylinder final drive and just changing the 3rd, 4th, and 5th gears to smaller sizes?

[95metro]

Put stuff in the Aerostar!

Where do you think most of my tools are??? :D

PS: I'm serious on that one!

[MetroMPG]

So it's just the torque difference between the 3 and 4 cylinder that makes it bearable with the 4? Any possibility of keeping the 3-cylinder final drive and just changing the 3rd, 4th, and 5th gears to smaller sizes?
It's all about the torque.

[SVOboy]

If you took all the other crap out of my swap it would've only take a few hours with jared's help. The biggest thing I think is experience. Now that I've done it I don't have to fool with all the stuff that went wrong, :p

EDIT: Just saw I was the motivation, yay. When I get home from this graduation party I'll post my gear ratios for you to drool at.

[95metro]

Also, that would mean taking the tranny apart, which is slightly scarier and requires special tools, I think.

Yeah, I know. I tend to make projects more difficult then they generally have to be, but I'm also generally happier with the final results. Of course, in our case maybe the slower 0-60 time is a good thing. We're hardly trying to break any speed records.

A perfect solution would be to fabricate a custom six-speed. I'm always reaching for the shifter and suddenly realizing I'm already in 5th. But, there I go making it even more difficult again. :D

Still, a full custom gear set would be really cool. 1st to 4th for town and a cruising gear for the highway. Perhaps one of these days when I have a garage...:cool:

[95metro]

You got my brain scheming, Darin. Here's some good, general info on transmission gears (copied from http://www.innerauto.com/Automotive_Definitions/Transmission_Gears/):

Most cars have from three to five forward gears, and one reverse gear. The transmission changes the ratio of the engine speed and the wheels by connecting gears in various combinations. If a gear with 10 teeth is driving a gear with 20 teeth, the drive would be said to have a 2:1 ratio. First gear connects the engine power to the drive wheels via a pair of reduction gear sets, which gives increased power and reduced wheelspeed when the car is beginning to move. This means the engine is turning much faster than the output shaft, typically around a 4:1 ratio. Intermediate speeds are delivered by changing the gear ratio closer to 1:1. Final drive is usually accomplished by directly linking the input and output shafts, giving a 1:1 gear ratio. Using a moveable set of different sized gears, it's possible to get several degrees of torque output. The differential pinion, driven by the drive shaft, turns the ring gear, which acts like a single speed transmission. This further reduces RPM's and increases torque by a set ratio.

Gears work exactly like levers. A small gear driving a larger one gives an increase in torque, and a decrease in speed, and vise-versa.

Transmission gears are heat-treated, high quality steel. They have smooth, hard teeth, cut on precision machinery while red hot. There are many types of gear teeth, but most transmissions use spur and helical gears. Most of the gears are the helical type, because they last longer and are more quiet than spur gears. There has to be enough room (a few thousandths of an inch) between the gear teeth for lubrication, expansion, and any irregularities in size.

[MetroMPG]

Any possibility of keeping the 3-cylinder final drive and just changing the 3rd, 4th, and 5th gears to smaller sizes?
Sounds like the "nerd gear" option that my brother in law and I talked about. As in - why wouldn't the manufacturers offer a taller that stock top gear for the hard-core FE nuts?

[95metro]

Just pondering some more and I was wondering if those two older Swiftclones you have actually do have the same gear ratios as the Blackfly. The late 80s early 90s clones certainly seemed to get better FE than the mid 90s to 2000 3-cylinders.

They were lighter, maybe even more underpowered, but were the gears identical? Maybe look at putting the old Firefly tranny in the blackfly? I thought I read somewhere that there were some slight transmission variations besides final drive.

[MetroMPG]

They were lighter, maybe even more underpowered, but were the gears identical? Maybe look at putting the old Firefly tranny in the blackfly? I thought I read somewhere that there were some slight transmission variations besides final drive.
Lighter, less rotating mass (12 in wheels & tires); also the pre-86 cars EPA ratings were higher, even though they used the same test method (they introduced a "fudge factor" and changed the ratings even though the cars didn't change).

[GeoMetry]

I think I am accomplishing basicly the same thing but doing it a completely different way. The whole point of switching out the transmission is to get further down the road for each revolution of the engine. I opted to just swap out the wheels and tires. Going from 155/70-R12 to 155/80-R13 has the same effect as putting in a transmission from an XFi. In addition it only cost me $50 for the wheels and tires. I have ordered the proper lug nuts for another $20 and I am expecting them this week. In my case this has the added benefit of greatly simplifying the task of getting replacement tires as the 12" tires are getting hard to find.

I already swapped out the camshaft for the camshaft from an XFi. I was told that the XFi camshaft gives the engine better low end torque. So I hope to be reporting some excellent numbers when the Gas logs come back.

[95metro]

(they introduced a "fudge factor" and changed the ratings even though the cars didn't change)

Oh right, I totally forgot about that. The "decreased percentages" from everyone whining that they couldn't attain the numbers the EPA posted.

Thanks for the bedtime reading - but I'll have to do it now. I'm busier at home than at work lately...:mad:

GeoMetry - That's very cool about your cam swap. What's the major difference between the standard and XFi cams?

[MetroMPG]

I opted to just swap out the wheels and tires. Going from 155/70-R12 to 155/80-R13 has the same effect as putting in a transmission from an XFi. In addition it only cost me $50 for the wheels and tires.
You're right - same effect. And truth be told, if I knew someone with a big honking set of 14 or 15 inch wheels that would fit our odd-ball bolt pattern, I would like to try them first and do some calculations to see whether or not I'd be happy with the transmission swap.

I probably wouldn't be doing any of this if I didn't have the transmission. It was essentially free.

I'm eager to see your gaslog results too. FYI, I helped Matt with the gaslog a little bit today, running through the new setup looking for bugs/improvements. I think he's close to switching the new garage/gaslog back on.

[MetroMPG]

GeoMetry, if you still have your calculations of what you accomplished with your wheel/tire upgrade (e.g. wheel revolutions per mile, or engine RPM at a given road speed), do you mind sharing them here? Or start a new thread? It's good to have that kind of thing worked out for everyone to see.

[95metro]

Some bedtime reading...

http://www.teamswift.net/viewtopic.php?t=14845
http://www.teamswift.net/viewtopic.php?p=163307
http://www.teamswift.net/viewtopic.php?t=23748

Pretty interesting. So there are no major gear ratio changes (besided FD) until you hit the 1.6L Swifts. At that point you'd be looking at a huge torque difference between the 1.0L and the 1.6L so that probably wouldn't be a wise move at all.

Plus it does nothing for you since you already have the "free" transmission. It's a lot of work for an "experiment" isn't it?

[katman]

Larger diameter tires would be the same as changing the final drive, just looking at the numbers. But a larger diameter tire also has a bigger contact patch and that means more rolling resistance. I don't know how much it would affect things, but if nothing else your car should handle better.
On second thought maybe not. A taller tire will raise your center of gravity and your might loose handling. Another factor with the taller tire and the car sitting taller is more air going under the car with more aero drag.

[GeoMetry]

I do not claim to actually know anything about camshafts. I will point you to http://www.teamswift.net/3tech/ They sell several different camshafts for the 3 cylinder Geo Metro including an economy camshaft that is very similar to an XFi camshaft. So close in fact that when I inquired about their economy camshaft they advised me not to purchase it since I already had an XFi camshaft. There are links to reviews of many of their products. I have never actually purchased anything from them but they seem to be highly regarded.

Using the tire circumference calculator at http://www.5speedtransmission.com/calculators.html (http://www.5speedtransmission.com/calculators.html) it appears to me that switching from the standard 145/80 R12 tires that are specified for my 1994 Geo Metro to 155/80 R13 tires would produce almost exactly the same result as swapping the standard 4.105 final drive transmission for an XFI 3.789 final drive transmission.

Cross multiply and divide.

66.3 71.6 Tire circumference
3.789 4.105 Final drive ratio

(4.105 * 66.3) / 71.6 = 3.801

You would have to drive well over 300 miles for the difference to add up to one mile. Since both 4.105 transmissions and 155/80 R13 tires are easier to find I am using the 4.105 transmission and the larger wheels/tires. There are implications to the brake system as well, the larger wheels will make the brakes less effective. I have read a few posts talking about rotational weight and how important it is to keep that to a minimum. What is that all about and how much effect will what I am doing have in that respect?

[katman]

The more weight you have the more gas you use to get it to move. I forgot about the brakes. Most people go to larger diameter brakes and that's just more weight. You need to keep the same size rotors and go with better calipers that have more clamping power.

[MetroMPG]

Plus it does nothing for you since you already have the "free" transmission. It's a lot of work for an "experiment" isn't it?
Well, there's no doubting it would help my overall mileage. The only experimental question is whether it would hurt the car's driveablility so much that I wouldn't like it.

[GeoMetry]

In my case we are talking about going from 12" to 13" in your case it would be from 13" to 14". I have an XFi transmission sitting in my garage but it has a bad syncro. The advantage to me of using the XFi transmission would be that my speedometer would read correctly. The disadvantage would be the difficulty of finding 12" tires next time I need them. The way I drive these days my tires will probably last forever. I accelerate slowly, I rarely use the brakes. About the only thing I do that stresses the tire is occasionally take a corner a bit fast.

[Compaq888]

My car has the best gearing for fuel economy, if you upgrade to that transmission you'll hate it. I have no power whatsoever in 4th till about 55mph.

I'd love to switch to the 2000-2001 manual tranny, not only will I have manual but it will lower my 1/4 mile time more than a full second. From 16.9 to 15.7 or maybe lower. I would still gain mpg because of the fact that I could do engine off coasting and could coast anytime I want in the top gear.

[SVOboy]

I wouldn't call your gearing the best for fuel economy, since mine is better...

Besides, I don't think any gearing that is attached to a torque converter can rightly be called the best, at least not until auto transmission surpass driver abilility.

Anyway, I also do not think darin is terribly concerned with his speed, I know that my car is much slower now and I don't care, though to be honest I'm prolly way low in the rpms, but I dunno since my tach isn't working...

[Compaq888]

you're right, I wish I could put in a 2000-2001 gearing or even get a manual car.

[SVOboy]

Sell the damn thing already, it's not getting more valuable.

[MetroMPG]

I have an XFi transmission sitting in my garage but it has a bad syncro.
:( 2nd or 3rd gear?

[DaX]

Garage, schmarage. The transmission isn't very big, and it only weighs 65 lbs. You could easily put it (hide it) on the shelf in a coat closet. :D

I ran out of space in my shop, so now I have an Integra engine in my closet at home. :)

[95metro]

I ran out of space in my shop, so now I have an Integra engine in my closet at home. :)

I take it you're not married, right? :D No woman would let you put an engine in their closet.

[DaX]

I take it you're not married, right? :D No woman would let you put an engine in their closet.

August 19 of this year my friend. ;) I've already been warned that there will be no car parts stored inside our house.

[SVOboy]

What ever happened with this, darin? Getting razy?

[95metro]

He's off on his boating excursion. I think the Forkenswift is taking up most of his free time as well. :cool:

[SVOboy]

Yeah, I figured I'd bug him about it when he was gone so he couldn't fight back, but if he ever wants to see a 110mpg segment...

[MetroMPG]

Defending myself, briefly, from an internet cafe in Gaspe, Quebec. Another week or so on the water, then we'll get back to the KDA MPG game. - D

[SVOboy]

I think you've already KDA'd, D.

[MetroMPG]

Some more thinking out loud... (have a highway trip coming up in the next couple of weeks, which gets me thinking about aerodynamics and gear ratios)

[SVOboy]

Indeed, you should be fine, my jump was even bigger (I forget the gearing on the auto right now) but it's not even an issue. I think you'll love it, :p

[MetroMPG]

So I'm kind of "gaining" another gear. The stock tranny 5th gear/diff product is actually slightly shorter than the product of the 4-cyl tranny's 4th gear/diff.

[DaX]

Just do the swap already. :D

[MetroMPG]

Just do the swap already. :DTell you what - I'll go pick up the transaxle from Ivan's garage tomorrow. Maybe I'll do it this weekend. I have all the research done & bases covered.

[Matt Timion]

Tell you what - I'll go pick up the transaxle from Ivan's garage tomorrow. Maybe I'll do it this weekend. I have all the research done & bases covered.

YAY! Maybe we'll be working on our transmissions at the same time. :)

I still need to fix my axle seal.

[MetroMPG]

I figure the timing is pretty good for this weekend. Project ForkenSwift is on hold for a week while Ivan works on his driveway (paving stones). Might as well check something else off my list while waiting to resume that...

[95metro]

my OEM odo/speedo will go wonky if I do the swap

Are you sure? The cluster in my Aunt's Metro is identical to mine (with the exception of the trip meter). I assumed the gear on the speedo cable was just a different size to allow the same cluster to be used regardless of engine/transmission...???

But of course I could be very wrong. :p

[MetroMPG]

I deleted the word "motivation" from the thread title. Started working on the swap this morning.

[MetroMPG]

Lunch time break. So far, only 2 minor snags.

[SVOboy]

How much does one of your transmission weigh?

[MetroMPG]

65 pounds. Close to what yours weighs, if I remember talking about that from earlier...

[SVOboy]

I'm notsure if I have ever weighed one. All I know is I can pretty easily haul it around with one hand, so it must not be too heavy.

[MetroMPG]

I worked on the car most of this afternoon, with a couple of breaks for family stuff.

[SVOboy]

Rather exciting, good sir, rather exciting indeed. I hope you had the tranny in neutral while trying to put it on!

[MetroMPG]

Now You Tell Me!

[SVOboy]

Time for a speedometer swap!

Anyway, in the two transmissions I've done I don't think I've remembered to put either in neutral, just get some bolts threaded and sneak it on is my strategy these days, but I'll have to remember in the future.

Glad you're happy with it!

[MetroMPG]

Of course, I also have the gauge cluster from the red ForkenSwift in the garage. So that's definitely an option.

[SVOboy]

Hmm, I like my trouble free speedo that will work with any transmission, or mehbe it's my trouble free transmission that will work with any speedo. Or mehbe it's my trouble free auto manufacturer.

:D

[MetroMPG]

Strangeness.

According to Google Earth, my odo (and speed I assume also) is under-reporting by about 5.7%.

[SVOboy]

Ah, you're nuts, but anyway, FE? FEFEFE?

[MetroMPG]

Sorry - can't do FE until the SG is reporting the right KMs.

[SVOboy]

You can convert it by haaaand. Raaaaawr.

[MetroMPG]

Yeah, but that's hard.

[SVOboy]

I'll just say good luck. My vss has a little gear on it that spins, and the gear on the FD determines the spinning, so regardless of the tranny/fd there's a gear that makes sure it's always correct. So Iono jack about FD/VSS correction besides honda did it for me.

[MetroMPG]

I wish I had a little gear that spins and makes things so I don't have to do math. Math is hard.

[SVOboy]

Don't worry, Math, I will defend your honor!

Anyway, it would really depend if it were a linear relationship or not, but this I do not know.

[MetroMPG]

Figured out the odo/speedo difference. Man, I'm not very swift sometimes (actually I'm part Swift now, but... bad pun, never mind).

[95metro]

Woohoo...nice work! :cool:

[SVOboy]

Feeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee!

[MetroMPG]

OK Ben: since you can't wait to find out (neither could I)

For an average FE improvement of 8.8%

Feeeeee! :)

[SVOboy]

RPM difference!?!?

Anyway, what's the lowest speed you can go in 5th with the new transmission?

[MetroMPG]

RPM difference @ 65 km/h

[95metro]

So when are you going to attempt a 110 mpg segment? :D

[SVOboy]

So when are you going to attempt a 110 mpg segment? :D
YA RLY!

[MetroMPG]

No pressure, eh?

I don't think the new legs are going to make much of a difference in city/suburban driving, where I did the 101 mpg loop.

I may try again sometime though.

Now that this is done, I'd like to have a second look at the belly pan. But not likely soon. I want to get back to Project ForkenSwift.

[95metro]

No pressure, eh?

I don't think the new legs are going to make much of a difference in city/suburban driving, where I did the 101 mpg loop

No, no pressure :D

The lower rpm acceleration should help a little. Too hard to say how much. Can you still shift at 15, 30, 40, 50 or do you have to stretch it out a little more?

[SVOboy]

But with taller gearing and aero mods going 50 will be like going 40, and then you can speed your way to victree.

[MetroMPG]

Yeah, theoretically, the lower RPM should help with the moderate load/low RPM accel technique. (But it's not proven one way or the other yet)

[95metro]

I definitely have to shift later now. Up by approximately 7-10 km/h per gear. (e.g. 1-2 @ 25k, 2-3 @ 35-40 k, 3-4 @ 45-50 k, etc.)

So cruising in 5th will definitely see the major benefit since your shift revs are probably similar to the old transmission.

I just realized - you've got a practically new 1.0L transmission lying around now...

[MetroMPG]

Yes - I effectively gained another gear.

[SVOboy]

Hmm, just like some people think shorter gearing is better for FE, some people think taller gearing is better for going fast...

Anyway, how clean is that old tranny? I want a picture!

[MetroMPG]

some people think taller gearing is better for going fast
Accelerating fast, or top speed? Hmmm?

The photo at the top of this thread is the Actual Unit. I cleaned it up some since that photo, but it's still a little greasier than the box I took out.

Enough GS! must do some work today...

[Matt Timion]

Enough GS! must do some work today...

Muwhahahah! NEVER!

[SVOboy]

Accelerating fast, wackos!

[JanGeo]

NOPE the top speed is achieved when the gearing allows the engine to reach maximum HP at or before it - the Geo I have is geared for redline at 130-135mph and it only reached that a few times HA just kidding terminal speed was 93.7mph GPS measured - speedo needle was straight down way past 85mph max . . . . still pretty good.

[SVOboy]

Yes, but we're not discussing top speed anyway, besides, my car is geared for a 210mph top speed but I'm not showing that off, :p

[95metro]

Yes, but we're not discussing top speed anyway, besides, my car is geared for a 210mph top speed but I'm not showing that off, :p

Ah...so that's how I managed it in Forsa for the XBox...(205+ mph CRX) - I basically tuned up an HF tranny. :D

[SVOboy]

Either that or you were revving to 10k, :p

[DaX]

Awesome. Mine does too...just need to get the AC fixed so I'll WANT to drive it.

[MetroMPG]

Update: I've noticed one mechanical issue with the 3.52.

[95metro]

My dad had something similar happen with his MT Ranger - not that he engine off coasts, but the sticking gear-neutral issue. I'll e-mail him about it and see what it was (but he did end up with an $800 clutch job).

I've never changed a transmission or clutch so pardon my ignorance, but is the clutch part of the transmission? Is the old Swift clutch in the car now as opposed to the Blackfly's practically new clutch?

If the transmissions are interchangeable then the clutch should be as well...??? But I really have no clue if that's correct. :D

[brick]

The first problem sounds like a clutch issue to me. You shouldn't get a "crunch" of any kind as long as the input shaft is allowed to spin free of the engine, and bad synchros would show up in normal engine-on driving. The second problem I can't explain, as there really shouldn't be anything dragging if the trans is truly in neutral.

Maybe something is off with the shift linkage?

[MetroMPG]

95: The clutch assembly isn't part of the transmission - it's attached to the flywheel. When you pull the tranny, the clutch assembly remains behind, on the engine. I retained my original assembly in the swap.

Brick, your comment and another page I just read suggests it may be the bearing supporting the input shaft hanging up a little:

http://www.drivetrain.com/clutcharticle.html

There are two potential bearing-noise makers in the clutch system-the release bearing and the pilot bearing. To determine which one, if either, is making the noise follow these steps:

Step 1 With the engine running and the transmission in neutral, if the noise occurs it is in the transmission, most likely the front bearing supporting the input shaft.

If that's it, it's not a huge deal. I can simply key-start the engine when I occasionally can't get the shifter to go in. I'm not going to pull it apart again any time soon :)

I would however still like it to be a linkage or cable problem.

[Matt Timion]

Ah.. if it's the clutch release bearing... that kinda sucks...

Not that you can't fix it in an afternoon, but who's motivated to take a tranny off just to replace a tiny part?

Someone recommended to me that I put a new clutch release bearing on my tranny when I got it. Now I'm glad I listened ;)

[MetroMPG]

It's really not a big deal. Just came back from a longish drive and out of maybe 2 dozen codfish, I only had to keystart twice due to the shifter not wanting to slot into gear.

I've decided not to worry about it. It's a minor issue and I'm very happy with the FE gains it's brought.

[MetroMPG]

Adjusted my clutch cable this afternoon

[MetroMPG]

Seen posted at teamswift (after sharing the details of my swap) ... :D

Posted: Fri Jul 14, 2006 10:47 pm Post subject: WTB: 3.523 ratio final drive

WTB: 3.523 ratio final drive crown wheel & pinion from a 1989- 1994 1.3 sohc swift, to put in my 1991 5-speed geo metro trans.

Thanks
Daryl

[Gary Palmer]

Compaq888: Did you get a replacement vehicle already?

[MetroMPG]

Update: since the clutch cable adjustment, I've had absolutely NO problems with the 'new' long-legged transmission in any way.

[SVOboy]

Told you so, told you so!

Where's the 110 segment!?

Hell, I'll settle for 105.

[krousdb]

Ye have little faith......

[MetroMPG]

Can we split the difference? :o

[SVOboy]

I'm really pissed right now.

[MetroMPG]

Oh? Do you mean angry, or drunk?

[krousdb]

With or without the alternator belt?

[MetroMPG]

Without. Best I've been able to manage with the belt is around 100.

Edit: which, now that I think of it, is actually an improvement since my previous best of 101 was without the belt.

[DaX]

Man I've got to get an MID...maybe christmas.

[MetroMPG]

In mpg vs. speed - metro graph (http://www.gassavers.org/showthread.php?t=858), I wrote. ...

I realized last night that my claim of 8.x% improvement with the taller transmission is faulty, because I based it on the colder ambient speed/mpg data. The actual transmission improvement is less.

There was a 20+ F difference between the runs I was comparing. :(

I'm going to have to hunt around for some more relevant mpg data for a better pre-tranny swap comparison. I'm surprised nobody called me on my exorbitant claims!

(Anyone want to buy of my some bio-fuel pills? They really work!)

[SVOboy]

I didn't think 8.8% was all that much, :)

[MetroMPG]

Depends on how you look at it. I think 8.8 is fantastic if you've otherwise plateau'd your FE!

[SVOboy]

Haha, I only get like 26-27%, :p

I wish I could plateau, but not enough time and it seems my numbers just keep improving.

[MetroMPG]

the FE improvement from the transmisison is likely closer to 5% (5.6%, based on the single 70 km/h point comparison) than 8.8% I claimed before.

[MetroMPG]

Collected a bit more info:

[ZugyNA]

All of this is a long-winded way of saying that the FE improvement from the transmisison is likely closer to 5% (5.6%, based on the single 70 km/h point comparison) than 8.8% I claimed before.

I'm wondering how this 5.6% mpg gain compares to the % change in overall gear ing? Not sure that you mentioned this.

[MetroMPG]

The taller transmission lowered RPM by 19.8%. It was lowered a further 5.8% because the OEM tires on the Blackfly are taller than the tires originally spec'd on the taller transmission car.

[Compaq888]

Compaq888: Did you get a replacement vehicle already?

Yes I did. 99 civic dx 5 speed manual.

[MetroMPG]

Some rough temperature calculations:

So roughly 2.5% of the increase could be attributed to the temperature difference, which leaves about 5.2% of the FE improvement attributable to the transmission change.

[Silveredwings]

Wow, there's some great info here. Now I'm considering doing something like this.

The bimmer is geared extremely short (IMHO): final drive is 3.46:1

5-Speed ratios:
1 - 4.23
2 - 2.52
3 - 1.66
4 - 1.22
5 - 1

With 3.46, the final ratios are:
1 - 14.64
2 - 8.72
3 - 5.74
4 - 4.22
5 - 3.46

Being RWD, I can change the final drive to 2.93:1 (also avail 2.79, 3.07, 3.15, 3.23, 3.38). That would give me:
1 - 12.39
2 - 7.38
3 - 4.86
4 - 3.57
5 - 2.93

I don't think this is too radical. In comparison, the Firefly went from (correct me if I'm wrong):
1 - 15.00
2 - 8.31
3 - 5.62
4 - 4.01
5 - 3.32

to:
1 - 12.03
2 - 6.67
3 - 4.51
4 - 3.22
5 - 2.67

...which is still taller.

BTW, phase 2 would entail dropping in a 6-speed tranny:
1 - 4.35
2 - 2.5
3 - 1.66
4 - 1.23
5 - 1
6 - 0.85

With 2.93, I'd get:
1 - 12.75
2 - 7.33
3 - 4.86
4 - 3.60
5 - 2.93
6 - 2.49

Now all I need is to find the hardware. ;)

[onegammyleg]

I haven't read the other postings on this thread , so perhaps I am repeating others words.

When doing a final drive ratio change , especially in a 4 cylinder , you may drop the car out of its usable power range at normal speeds.
This may force much higher cruise speeds to keep the engine happy , but at the sacrifice of aero drag losses.
Also it may force staying in lower gears longer - the total of the two may result in worse FE.

I wouldnt go nuts on a diff swap , you could test it with oversize tyres and see if a similar ratio works OK then go with the diff swap if your see an improvement.

[MetroMPG]

I agree with the idea of trying the effective gearing change with oversize wheels/tires first, if you can. Simpler & easier to undo if you don't like the results.

BUT ... I think I've done what a regular driver would describe as a pretty "radical" final drive change. And on a 1.0 3-cyl the possibility for negative effects (moving the engine outside of its usable power range for a given road speed) is even greater.

Yet that hasn't happened (to the point of making FE worse than it was before the swap). The before/after speed vs. mpg chart (http://www.gassavers.org/showpost.php?p=23449&postcount=114)shows this empirically.

It is true that I now have to sometimes downshift at highway cruising speeds (< 90 km/h / 55 mph) to accelerate and/or climb hills, where before, like almost all other cars, I could have remained in top gear. But I don't have a problem with shifting. It's why I bought a manual.

I'd recommend the same mod to any Suzukiclone hypermiler, with the disclaimer that I live in a relatively flat geography. I'd question its suitability in steep mountainous terrain.

[Silveredwings]

I haven't read the other postings on this thread , so perhaps I am repeating others words.

When doing a final drive ratio change , especially in a 4 cylinder , you may drop the car out of its usable power range at normal speeds.
This may force much higher cruise speeds to keep the engine happy , but at the sacrifice of aero drag losses.
Also it may force staying in lower gears longer - the total of the two may result in worse FE.

I wouldnt go nuts on a diff swap , you could test it with oversize tyres and see if a similar ratio works OK then go with the diff swap if your see an improvement.
I would agree, though the car in question has a fairly torquey 2.5L straight 6. The current first gear is so short (final ratio is 14.64) it's almost useless when I'm not pulling stumps. :)

There is an AWD version of the same car/engine that was offered with a 3.23:1 final gear. The two reasons I guess they went with a taller grear is mpg and traction.

I frequently start out with second gear (final ratio 8.72) with the stock gearing. Changing the final gear to 2.93 would move first gear to a more useful 12.39. As for the rest of the gear range, I'm not trying to optimize the zero to sixty specs, but how can I tell if I'm really moving out of the sweet spot of the power curve?

[MetroMPG]

but how can I tell if I'm really moving out of the sweet spot of the power curve?

Do you have a BSFC map for the engine, or a similar one? That would be the best way to figure it out.

Mainly, I'd think you'd want to ask: at your typical highway cruising speed (where a final drive change should reap the biggest reward), what would be your effective change in RPM? From what to what?

With the BSFC map you could then see how far out of (or towards) your peak efficiency you're heading with the change.

[Silveredwings]

OK, it looks like I'm in need of some more edumacation.

I can easily calculate the rpms vs mph for each gear combo (e.g. 60 mph in 5th goes from 2711 to 2295).

I have no idea where to get a BSFC graph of my engine (model M54B25). If I had one, how would I use it? Isn't it something that shows where the engine produces the most HP per unit of fuel used? The problem with minimizing overall fuel used (maximizing mpg) is that I'm not always trying to get the most HP out of the engine. At 60 mph, I doubt any gear is going to be at peak, and since I need less than 20 hp to go straight and level, the top gear should simply bring the rpms down somewhat. I'm clearly not getting something here.

BTW, I realized another more likely reason that BMW used 3.23 instead of 3.46 in the 325xi AWD version: a 0-60 score that's more competitive in the marketplace. It can reach 60 in 2nd gear whereas mine has to shift into 3rd to get to 60. I'm not sure why this was important for one model vs. another but I'm not a marketeer either.

[MetroMPG]

No, you're right: a 400 RPM difference isn't going to move you far enough on a BFSC map to make your fuel consumption lower at cruise than it is now.

[Silveredwings]

The dotted lines are existing gear ratios, the other lines are proposed. The old 5th and new 4th are about equal. Then there is 1 or 2 more gears (depending on if I do the 6-spd).

If the BSFC roughly follows the torque curve, then it peaks at about 3000 rpm. That would make sense as typical shift points under moderate accelleration. Shifting from 5th to 6th at ~70 mph (a kind of upper range use case), would bring my rpms from ~2800 down to ~2300.

http://www.gassavers.org/attachment.php?attachmentid=69&stc=1&d=1164943612

The biggest difference seems to be losing that very short 1st gear for towing a Winnabago up a hill. :D

(edit: changed mild to moderate)

[omgwtfbyobbq]

Any drop in gear ratio should make it lower, since more fuel is needed to make the same amount of power when the engine is moving slower, but it probably wouldn't be noticeable. Going from 4th to 6th in a 330i only increases mileage by 12% according to C&D, and 400 rpm drop may only net ~4% or a little over a mpg.

[onegammyleg]

I'd recommend the same mod to any Suzukiclone hypermiler, .

My Swift must have a different ratio than normal metro's.
I rarely get to use fifth gear around the suburbs , definitely a highway gear for me.

[onegammyleg]

There is a point at which the gearing can get too high..

Yeah , like what I said.
I couldnt imagine any longer legs on my diff.
My Swift (which seems to have many differences to a similar year metro in places) always needs a downshift to 4th on small/medium sized gradients at highway speeds.

I dont know what the ratio is , but it certainly doesnt scream its head off.

I can still be happily driving along in 3rd at 35mph. -- and on the other side , 130kmph in my Swift wasn't over reving the motor in anyway.
In fact it was very happy to sit on this speed.

I wonder how that compares to other metro owners. ???


A diff ratio swap is a great idea , if the car in particular has been fitted with unusually low gears., but for most cars , the cost of this mod is a bit high especially if your not certain that it will bring an improvement.

[Silveredwings]

A diff ratio swap is a great idea , if the car in particular has been fitted with unusually low gears., but for most cars , the cost of this mod is a bit high especially if your not certain that it will bring an improvement.
In this case, bimmer forums have batted around $200 as an average cost of a used diff, plus changing a pumpkin with separate half shafts is fairly easy compared to a live-axle setup or worse, a FWD gearbox. Also, BMW does something unusual, they hook the speedo up to the rear axle in the diff so it doesn't introduce an error with the speedo/odo. So, asside from actually getting the diff, it may be easier than trying to get an oversized tire setup to fit.

[MetroMPG]

I wonder how that compares to other metro owners. ???

Got some RPM figures? (Otherwise we're just batting around subjectivity about what's "screaming" or not.)

[red91sit]

Hmm, for fuel mileage, it almost seems as if slightly higher FD with a much higher 4th and 5th gear would be the best way to go.

I don't mean to brag, but my FD is 3.08 and my 4th gear is .67, for a final motor revolution/wheel revolution of 2.0636. Highway speeds are in the 1000-1200 rpm range. I've noticed certain things that make for this possible, more torque down low. I've heard that engines are most efficient at their torque peaks, even though they waste the most energy here, so I was thinking what if we modified are smaller fuel efficeint cars to have more torque? right now I"m sure their torque peak is well above our crusing speed. I would imagine the torque band could be lowered for those of us running our engines at speeds lower than stock.

Even with my cars monstrous frontal area, drag C/D of .48, and 4.9 liter engine, I still managed 26 mpg at 60 mph, on e-85! this got me thinking maybe this platform isn't so horrible after all? after all, a 5.0 liter at 1000 rpms, is pumping the same amount of air as a 1.6 cylinder at 3125 rpm's, this would explain why my two cars are getting fairly close mpg. The motorcycle engine would have to be at 12,500 rpm's for the same air pumping, which would explain why even at 5000 rpm's with old carbeurators, it's still my MPG champion.

Well, now that i've shared some useless information, i'm more confused than ever as to what is ideal for gas mileage. :(

[SVOboy]

I don't mean to brag, but my FD is 3.08 and my 4th gear is .67, for a final motor revolution/wheel revolution of 2.0636.
.692 * 2.95 = 2.0414

Be jealous!

[SVOboy]

True, my tires are only 175s, :p

[SVOboy]

I always thought it was height/width/rim size.

175/55/13 I believe mine are.

[SVOboy]

Oh shucks, :p

Things like that I could never keep straight. Thanks for the info.

[Spule 4]

Mmm, swapping with a long-legged taller tranny beauty here in Metro...oops, that is another forum I am on, sorry!

My Swift must have a different ratio than normal
metro's.
I rarely get to use fifth gear around the suburbs , definitely a highway gear for me.

US Metros are the same in behaviour, not sure if the box is the same between the US G10 motor and the European G13?

So, asside from actually getting the diff, it may be easier than trying to get an oversized tire setup to fit.

In the 13 years we had our Metro, even simple tire changes would impact FE. In the end, I even thought of larger (155) tires Vs. the 145 to give better economy at highway speed (less rotations per mile) but this did not actually work out. Metro FE drops fast over about 55 MPH for sure, and I did not impact FE but I did impact acelleration.

[onegammyleg]

Metro FE drops fast over about 55 MPH for sure

Yeah , but my Swift /metro thing the economy is great still at 60+.
On one country trip I was still just getting just under 40 mpg with a lot of time spent at 130kmph , which is umm.. 80 mph.
Taking it a bit easier does give 47.

But the around town economy sux big time.(36) , even with pulse and glide I can get no where near the rated metro figures.

[Spule 4]

Yeah , but my Swift /metro thing the economy is great still at 60+.
On one country trip I was still just getting just under 40 mpg with a lot of time spent at 130kmph , which is umm.. 80 mph.
Taking it a bit easier does give 47.

But the around town economy sux big time.(36) , even with pulse and glide I can get no where near the rated metro figures.

Yes, but we were 50 MPG in the US, it drops to the 40-44 MPG range when you are around these speeds you post. A Metro will go 90......if you make it.

[MetroMPG]

For those who are following this thread, I finally posted a summary/report on metrompg.com: Project 'nerd gear': taller tranny transplant nets +5.2% MPG (http://metrompg.com/posts/tranny-swap.htm)

[Silveredwings]

Excellent article, and 5.2% improvement is great. :thumbup: