Topic: The promised full transmission writeup

[evenstephen85]

It's time for me to get the transmission writeup done as well since I did promice it a couple months ago and I just wrote an even larger article on spring rates.

Most of my revelations and the promice for this writeup came from this article here:

http://9glancers.com/index.php/topic,13194.0.html

Essentially what it boils down to is that we really really need an extra gear in our manual lancers GTS, and the CVT folks do have the extra gear plus a couple really ingenuitive fixes to their gearing ratios.

Lets take a look at the manual.  The first attachment shows a plot of the torque curve in each gear.  Rather than showing the torque for any given rpm I took those rpms and converted them to miles per hour for that specific gear so we can take a look at what the driver can do in any gear given his current speed.  It should also be noted that these values are for WOT.  You could get the torque in 1st and 4th to match if you provided very little throttle in 1st and WOT in 4th etc.

So essentially at WOT you take off in 1st and fly through your rpms on your way to 31 mph.  This is because even though the torque at the flywheel is always the same at any given RPM the gearbox converts that torque to a higher value for lower gears so you can get off the line faster.

At 31.3 mph you hit the electronically governed redline (some tunes move this to 6800 rpm and seem to run fine.  This would help to smooth our transitions out and keep us in our power band longer) and you have to shift into second.

This is where so many people say our car really falls flat on its face.  back in the day cars had fewer gears (remember 3 on the tree anyone).  They're expensive, heavy, and eventually will fail so cars ran fewer of them especially since 55 mph was pretty much the maximum speed you could go anywhere in america anyways.  When gears are far apart they are called wide.  when gears are close the transmission is said to be close.  Our first and second gear ratios are 3.833 and 1.913.  This is about 2 times as large going from first to second.  2x is generally accepted as the ratio for a wide transmission.

So our 1st and second gears are wide while the rest would be considered close.  so you get to 31.3 mph and shift into second.  This drops your revs from 6500 clear down to 3200 which, forturnately, is right about where maximum power mode kicks in and the beginning of torque curve lies but you still have lost about 44% of the force you were previously applying to the road... sucks! at these speeds wind resistance still is not playing a very large factor which helps us move through 2nd rather quickly.  (in fact the change in wind resistance from 0-55 mph is about the same as the increase in wind resistance from 55-65 mph meaning if you were using 5% of your engines power to cut through the wind at 55 you'll be using about 10% at 60.)

As you move through 2nd gear you will hit the redline at about 62.8 mph which will drop you to about 4500 rpm in 3rd (just past peak torque) a much better place to land.  3rd gear will carry you to 90.2 mph and you'll shift into 4th at 4700 rpm.  fourth goes to 123.7 mph and drops you into 5th at about 5100 rpm.  At this rpm and gear ratio you will barely even knotice the change as it will only be about a 4% loss in torque compared to the 44% from first to second.  Now, some cars seem to have a limiter at either 120 or 125.  I haven't ever reached a speed governer on my GTS, and I also haven't toped out on speed either so I don't know what happens at this point.  Either you will succomb to wind resistance (most likely to occur at your peak power at about 145 mph) or you will hit your rev limiter at 155 mph.  I read somewhere the theoretical maximum for our car was 152 because it takes all the cars power to cut through the air leaving no extra power to accelerate it any faster.

Now, a 6th gear would really help us out in two reguards.  First they could make 1st and second a little closer which would ease that transition and second we could throw it into 6th to cruise on the highway and save a little gas.  Now depending on your local laws, and your willingness to follow them I generally cruise around 3300 rpm or 78 mph in 5th. Dropping this rpm down would probably help out our gas mileage as well as the highway drone for people with an exhaust.  (a sixth gear probably wouldn't help us much for top speed due to wind resistance.)

Given the flaws of the design I still have to give the Mitsubishi engineer that designed the transmission props because if you look at it on the transition from first to second they put it right about at maximum power mode. The 2-3rd transition they put so we would not have to shift until right after our 0-60 mph time.  With a quarter mile speed of 88 mph they put 3rd out just far enough to complete the quarter mile without the extra shift into 4th, and the transition from 4th to 5th is nearly flawless at the top end of things.  Props Mitsu on those facts.  I still want a 6th gear though... or maybe even a second cog on the final gear ratio to have a 10 speed bike effect lol jk.

Now lets take a look at the CVT.  Obviously the advantage of the CVT is that there would be no shifting if they programmed it up differently so you had "drag mode" or something like that that took you to your peak power asap and just kept you there.  That would be sweet... Unfortunately to get the most out of your car it seems best to use the paddle shifters and treat it like a manual with really really fast shiting abilities.

From my previous article they hooked me up with this second attachment.  It did something similar to what I did with the torque curve only they left it in RPM plotted vs MPH.  Now I don't know the spycifics because I don't have a CVT, but it looks like there is a low gear setting and an overdrive setting.  If there is a low gear setting (probably on the shifting console) here's my tech tip... since there's not a "drag mode" you'll likely have the best results launching in 'L'.  Run that up to the Redine (probably about 34 mph based upon the second attachment) then throw it into first in sport mode and continue shifting at redline all the way through.

If that does not work then I'll walk you though what will happen if you launch in sport mode and just leave it there.  from the previous tech tip everything will be the same after you throw it into sport mode from then on up.  The other question this graph begs to ask is whether one is allowed to shift into higher gears before 1200(ish) rpm (could be usefull for lower wheel torque in the snow if you don't have traction control) and if you're allowed to either (a) rev past 6100 in sport mode, or (b) let the cvt take over at 6100 rpm and just keep your rpm there while it did it's thing to change up your speed <---- this would be ideal ("drag mode")

For this example I'll assume you have to go through the gears one at a time and can to rev to 6500 rpm though this chart is misleading in many ways.  So in sport mode (all numbers are approximate) You'll run up to 3400 rpm or so then the computer will do a little "minishift" for you.  You likely will not even notice this because they put it right where the car shifts into maximum power mode and all us manual folks really feel it pull (I mean you might even feel a small loss where we feel like we just hit the NOS by comparison).  You'll shift at the redline every time in first it will be at about 48 mph, in second it will be at about 59, in third it will be about 75, 4th 93, 5th, 119, 6th, 125, and with a really long hill and massive tailwind you might be able to get moving 190 mph when you redline in OD, oh yeah, and you'd have to be dreaming, or running insane boost with a seperate transmission for each wheel so you didn't slip or burn up your belts on you CVT.

Some of the interesting things to note on the CVT are that when you're shifting in sport mode nearly every transition occurs at right arround 5200 rpm or so which is about the exact point where the downward slope of your power curve at 6500 rpm meets up with the upward curve of the next gear at 5200 rpm meaning you will always be using the whole of your power curve every time you shift.  This right here is perfectly engineered by mitsubishi so I'll give them props for this too.  Given this fact I don't know why they chose to work 6th like they did.  the transition from 5th to sixth will put you at about 5800 rpm which means you will actually want to go from 5th to 6th a little before the redline at 6400 or so to maintain the peak of your power curve.  With the curve on 6th my assumption is that they were going for linear acceleration above 85 giving by increasing the force applied to the road at the same rate as the increase in the wind resistance as the curve looks nearly quadratic.  They did you a bit wider gear ratio down low to conserve gas mileage (running at about 2900 rpm at 78 mph as per above in 6th or 2700 rpm at 78 mph in overdrive) before this curve kicks in at 85 mph or so.

It's interesting to note also that if there truely is a 'L' setting on the shifter and an OD setting you actually have 8 gears to play with in all reality: Low (and 1st below 3400 rpm) 1st above 3400 rpm, 2nd-6th, and overdrive.  Based on all of this the CVT should be silky smooth when you're running through gears whether you're in CVT mode or sport mode it will still be silky smooth all throughout.

Now this begs the question which transmission is better... Truth be told looking at the numbers I would honestly lean towards the CVT winning a head to head race.  It stays in its power curve more, and should have just as fast if not faster transitions than a human can input.  The cons of this transmission obviously being greater weight and the increased likelyhood for it to slip.  One way to find out would be to run a dyno for both under the same conditions and see which car has a greater loss of power to the drivetrain.  It would also be great to see a head to head matchup of the CVT vs. the Manual to see which one really is king.  Also any advantage the CVT had in the beginning of the race is virtually eliminated after a quarter mile as the manual does not have the same loss in power when shifting as it does in the lower gears.

It is interesting too when looking at the transmission to note that some tunes allow you increase the rev limiter.  This would do wonders to help the manual shift smoother and stay in its power band, but would do very little to actually help the CVT (this may not be true after modding, but remember shifting at 6500 rpm in the cvt is the ideal unmodded anyway).  The one main point for the manual over the CVT obviously is you need the manual if you intend to go turbo at any point.

As always I appreciate any corrections where I go off course and especially for this article where people can give some real word results of their testing (especially you cvt people since I cant test my theories on your car) and take it with a grain of salt because I've only been a "car guy" for about 3 months now. 

Either way, Kudos and happy driving!

And P.S. I still don't know how to place images in my writeups if anybody can help me there.  Thanks.

[webzes]

nice write up! you misspelled promised though

[somedood451]

Nice write up.  I think we could use a 6th gear as well.

Any thoughts on these two?  I'm not sure if either will fit.

http://www.getrag.de/en/245
http://www.getrag.de/en/246


Also, the mfg of the 5mt might have something too.
http://www.aisin.com/product/automotive/drivetrain/mt.html


With moving & all I don't really have the time to start even looking very hard at this stuff.  But if someone else is interested, these may be good places to start.

[tatsujo]

Great write up, if you can format it and organize it a little more along with your other ones, let me know and submit it in the knowledge base and we'll sticky it.

[Matchstick]

Oddly enough, I noticed right off the bat that the lancer seemed to need a 6th gear...

But actually at the other end of the spectrum, I don't know if what you are saying would change this... probably. Because why I do cruise in 5th, I keep wanting to shift into a higher gear, and I have never drivin a 6 speed, it just feels like there should be more power after 5th.

[webzes]

why wouldnt they make the evo a 6 speed? isnt the MR a 6 speed auto twin clutch?

[DuffmasterFresh]

Great write up! You had me captivated and on the edge of my seat the entire time

I was driving my friends EVO and was in 5th at about 50 just cruising and I instinctively tried to throw it into 6th. It just feels like it needs one, like it has one, like it was designed for a 6th gear but someone forgot to install it, haha.

So what are the best shift points for each "gear" when using the GTS CVT in sport mode?

[evenstephen85]

Hey thanks, I'm not sure if anybody would actually make it through the whole thing.  Truthfully I'm suprised more things weren't spelled wrong.  I can't help ya out with the transmissions somedood I'm an engineer professionally not a mechanic so I'm pretty good at analysis/charts/numbers, but telling you whether a transmission will bolt up is not my realm of expertice.  This is probably also why I'm so bad with spelling and grammar. 

Tatsujo, what type of formatting are you looking for?  Primarily just bringing them together into one document, or are you looking more for intentation etc?

Matchstick, I think you may have things a little bit backwards actually.  If you are looking for more power you would generally be looking to downshift not shift into 6th.  Downshifting is what you would do to pass people or get up a hill, throwing it into 6th would drop your rpms and cause you to loose power.  It would be great for your gas mileage, but just like there's no power there to start in 3rd (though possible) there's no 'power' to pass in a 6th gear.  Unless you cruise at over 90 you could drop it into 3rd for the most power.

Duffmaster, even in the CVT the ideal shifts would be at redline in every gear except going 5-->6 where I would advise shifting at about 6400 rpm.  Obviously that is if you want to go as fast as possible.  If you're looking to preserve your motor longer or get better gas mileage your 'ideal' shiftpoints would definately not be at redline.  The easiest way to determine shift points is to get a dyno for your spisific car then go out and get in your car and shift at the redline.  Then, check your rpms in the new gear.  With your cvt it will be close to 5200 every time, and even higher in 6th.  Then you'll want to sit down and look at your dyno.  What you're looking to do is to either a) shift at your redline so you have the most hp after you shift, or b) shift when your power starts to drop below what would be if you were to shift into the next gear.  To put it a little more simply you you're looking to have as much hp as possible at all times for racing.  If your hp is lower in the gear you're in than in the next gear you want to shift.  If there's more hp in the gear you're currently in then leave it there.  If there's more hp available to you after a downshift then that's what you want to do.  There are times where a downshift would unsettle your car or shifting would eat up more time then just running it up in your current gear, but thats generally the idea for racing.

[darealgts]

Very nice info, I have a 5speed manual and yea i want a 6th gear too lol, but the manual is hands down faster than a cvt, the cvt would be heavier not much but stil heavier and it robs more power, it has been proven before, manuals will always be faster, only the sst trans can be put up against a manual one.

[evenstephen85]

I wouldn't go so far as to say manuals will always be faster.  I've not even looked into the cvt, but the theory behind them only requires 4 pieces of metal (both sides of 2 variable gears) and a belt which could be trimmed down one day to weigh less, and once again the theory behind the cvt should make them faster if programmed for power instead of economy... always at peak power with no shifting would win a race for sure vs a manual if they can get rid of some of the losses they currently experience.

[Belgaram]

The Shift point in the CVT is at around 6000 RPM's.  It actually hits 6300 and goes flat.  I shift at around 5800 in 1st, 6000 in 2nd, 3rd and 4th. 5th I usually hit at round 90+ MPH to 6th which really is just a cruising gear.  Actually, the CVT is almost more like a 7 speed, because If I am at around 90+ in 5th at 5500-6k (not sure exactly what RPMs Im at at 90 in 5th) but if I shift to 6th it will drop down to about ~3K (+/-) then if I tap it over to D it will drop down to about 2600.

I may be a little different because of my build and tune, but that's pretty much always how it's been.

[-skywalkerGTS-]

The Shift point in the CVT is at around 6000 RPM's.  It actually hits 6300 and goes flat.  I shift at around 5800 in 1st, 6000 in 2nd, 3rd and 4th. 5th I usually hit at round 90+ MPH to 6th which really is just a cruising gear.  Actually, the CVT is almost more like a 7 speed, because If I am at around 90+ in 5th at 5500-6k (not sure exactly what RPMs Im at at 90 in 5th) but if I shift to 6th it will drop down to about ~3K (+/-) then if I tap it over to D it will drop down to about 2600.

I may be a little different because of my build and tune, but that's pretty much always how it's been.

Dam Bel, where u been at?
How's the car treating u?

[evenstephen85]

beautiful, thanks, that clears up part of the second graph so that horizontal like is a limit to how high your revs can go while in a particular gear.  In that case you would want to get as close to 6300 without hitting the limiter for ideal shift points... just like in the manual you wouldn't really shift at 6500 because your fuel would get shut off so you shift at like 6400 instead.  Good work.  You may want to test if when you get to 6300 it will still gain speed (switching into a higher version of cvt mode at 6300 rpm) because that's actually what the graph shows though I doubt that is the case.

And when you go from 6th to drive it should definately kick you down to a lower rpm (probably the overdrive line on the plot).  One question... does your transmission have a selection for 'L' because you could effectively have 8 gears if it does by going in low to redline then sport mode to 1st above 3400 RPM then going 2-6 and finally to "D"

[evenstephen85]

also, your mods shouldn't affect the transmission (other than causing it to slip/overheat a little more if you've made a little torque monster) because my understanding is that the transmission has its own computer and would not be effected even by an ecu reflash.  The shift points might change if you move your torque curve down to a lower RPM, but that would take runners/header/cams to effectively do so you'll still what to shift at as high an rpm as possible without getting cut off.  I still think it would be one of the best mods would be a chip for the cvt to give it a "drag" mode.

[somedood451]

I finally got a chance to look at the pdf & wow, it really says that someone forgot a 6th gear.

Asin Ai is the company that makes the F5MBB 5-speed m/t for our cars, and Getrag has always made some nice transmissions over the years.  I'm sure that we can get specs for mount points and bolt patterns for mating surfaces, weight offsets, etc.  I'm hoping it is entirely possible to pickup a 6 speed transmission for our cars that would just bolt in.  We could pickup some good time if this was a reality.  Also, there's that whole LSD thing.  Someone would just need to take the time to compare the specs, assuming both were readily available.

Of course, that would add a whole lot of complexity to changing out a clutch or drive shaft.  Still, it would be nice.  Probably be cheaper just to buy a new car in the long run.