hadokenny

May be the 3th-6th gear is not what people want, hence the low sales? Just thinking out loud...

mooty

i agree with matt
lots of ppl take free advises and lots of chatter.
but few step to the plate
i have the 3-6 gears
great stuff
not cheap
nothing good is cheap
i sold my gt4. afterall i had it for 6 months and needed a new fix lol
if not i would cough up whatever it takes to do the main shaft
some ken has to
do it first
group guy is a waste of everyone's time in my experience


frankly these issues were all discussed b4 with gt3 application

it can work great
someone just step up to the plate

mooty

i'm not sure what u mean

changing R and P is a short cut.
to do it right u need gears
to do it perfect u need gears and r and p which also calls for new main shaft and all six cogs

so in the real world chang 3-5 or 3-6 is
most beneficial

perfect? no
but it's pretty good

GTgears

I didn't say sales where low. You don't know what my expectations are or how many I made.

I don't make parts for DE cars. No offense but you guys are not my target customers. 90% or more of Cayman race cars run in classes that do not allow gear changes. I knew that going in. It was unusual for me to make the 3 gear kid with you DE guys in mind. Almost every set I've sold has gone into a 987 racecar. Moody and SW are the exception. I'm perfectly happy with the sales volume of the product line. My remark was not a complaint.

AutoQuest Motorsports

Heads up guys! We just released our shorter final drive ratio to take care of that long gearing once and for all! : )

Mech33

Since a different final drive is actually available now, I was curious what the specific offered final drive would provide in terms of available power or force vs. vehicle speed for the GT4's gearing.

As discussed previously, gearing doesn't change the power output of the motor (duh) but rather changes the speed range over which that power is available. In the case of changing to a 4.62 (vs. the original 3.89) final drive, this shifts all of the power curves down in speed ratiometrically (leaving ideal shift-points unchanged as the power curves still overlap at the same RPM points).

Translating that to effective force at the tire, here is a plot of the 4.62 vs. 3.89 vs. gear showing the differences:



As you can see, 1st gear is now effectively lower so there is more force available, but once the 4.62 car shifts to 2nd, the 3.89 car that is still in 1st now has more force available until that car has to shift, etc.

Here's a plot of the difference in force available for the 4.62 car vs. the 3.89 car (assuming each car is in the most ideal gear at every given speed):



For completeness, here's a similar plot of the difference is *power* available for the 4.62 car vs. the 3.89 car (note the very similar shape):



What's the conclusion? Here are my takes:

1) In 1st gear below 40 mph, the 4.62 car will clearly accelerate faster.

2) If you integrate the relative force curve from 40 mph onward, it's essentially a wash between the two (net is approximately zero). So as far as which will be faster either at the track or in a straight line acceleration "race", that will very much depend on the specific ranges of speeds seen on that particular track, or the particular starting speed for the "race".

3) You still only get to rev out 2 gears to redline (1st and 2nd) on the street before you are breaking highway speed limits.

4) I suspect the 4.62 will be more fun on the street as the RPM will be higher in each gear at any given speed, requiring you to either shift more or drive at higher RPM (more sporty).

5) Cruising in 6th with the 4.62 is essentially identical to cruising in 5th with the 3.89 (notice the curves overlap in the 1st plot).

Alan C.

Thanks for the data.

ExMB

Engineering versus sales.

Who will win this battle?

GTgears

When are you ever under 40 on a track?

Its faster to 40 IF you don't now have more power than traction. I suspect it will be tire dependent.

Mech33

Agreed. Another take-away is that the difference in power (or force) available over 90 mph is virtually identical and flat up until over 150 mph when 6th runs out on the 4.62 car.

Like I mentioned, either the 3.89 or the 4.62 could be faster than the other on the track depending on that track’s particular layout and resulting speed ranges for the GT4 gearing...

In other words, don’t jump to replace the final drive on your GT4 thinking it is going to make any difference for you on the track until you carefully analyze it (it might actually make you slower).

MagicRat

Thanks for that analysis - really interesting. If I tracked my car I’d leave final drive alone I think because I lose time each time I shift. For fun on the street though, it’s pretty tempting to get more revs and more use out of that gearbox.

Mech33

No problem. Without analysis like this, I think it's hard to wrap one's head around what a different final drive actually does to the car's performance.

I think there is a misunderstanding that increasing the final drive ratio by +19% somehow equates to effectively increasing the torque output to the wheels by +19% at every speed (which would mean increasing the power by +19%, and that is clearly not possible).

Honestly, the stock GT4 gearing isn't bad from an optimal use of power standpoint on the track. The power curve is relatively flat up top, and the 3rd-6th spacing is such at you're always going from one max power band to another when you shift. The biggest gap is from 1st to 2nd (and a little one from 2nd to 3rd):



"Fun" on the street is a different matter...

Mech33

Here's some more data for discussion: a comparison of a stock GT4 gearing thrust curve set vs. one retrofitted with GTgear's 2nd through 6th close-ratio gear set.

The close ratio gear set gives a lot more power band overlap between gears, relaxing some of the requirements to always shift right at redline to maintain maximum thrust.

mousecatcher

Mech33, what software/spreadsheet did you use to generate the graphs? Can you share?

Mech33