sergiDA

I just ordered from Guard Transmission shorter 3rd, 4th and 5th gears...I have decided this route as is the most cost effective alternative as getting a 993 mk1 box is expensive and difficult...

I have got 2 doubts which you may help me with:

1) I am regearing looking at 6800 rpm, is that too high? Iam using stock engine with SW chip, filter and the usal bypasses and not looking at modifing the car to go above stock rpm...

2) GT tells me that my box ( 964 c2 european1990) should be g50/03, but i think it should be g50/10... ?


Thanks for your help.

I enclose 2 charts: 50/03 stock and g50/ sergi ( proposed one)


Sergi

Porsche917K

I can't offer any answers to your questions but I am interested in the results. Do you have a projected MPH for each gear?

sergiDA

Look at the attachments, but km/h

KaiB

Interesting.

Here's where Sergi is:

1st: 3.50
2d: 2.059
3d: 1.526
4th: 1.200
5th: 1.00 (with a 3.44 final drive)

Here where I am:

1st: 3.50 (43mph)
2d: 2.25 (66mph)
3d: 1.684 (89mph)
4th: 1.286 (117mph)
5th: 1.04 (146mph with a 3.333 final drive)

The biggest difference being my much shorter 2d and closer drops across the board.

For euro use, and depending of track, Sergi may have a good compromise. Tradeoffs across the board, of course

Bill Verburg

the g50/10 was used in RS, g50/03 in normal C2

Here is a stock RoW g50/03


here is the same w/ the gear mods you propose. It looks good if you can live w/ the low top gearing 2k rpm in 5th is ~42mph, 3500rpm in5th is ~73mph


If you don't have an lsd that would be the first priority, before gear changes

the nice thing about the 6spds is that the extra gear gives you a lot of flexibility it would be expensive though

GTgears

We discussed using a 0.96 5th instead, but he decided he wanted the better acceleration over the highway cruising differences. The car is 80%+ track and really only sees the motorway to and from the track.

regards,

Matt

sergiDA

Hi Bill:

G50 03 vs 10, thanks on the clarification.

Your chart is very good, much more info than on mine, it looks as the 5th should be a little longer... otherwise i will dye commuting.

I already have the LSD

Bye
Sergi

Bill Verburg

I like the .96 5th better if nothing else you get a hunting gear set, 2k rpm is ~43mph, 3500 is ~76mph

GTgears

Bill,
Could I trouble you to throw up your G50/10 chart for Sergi to look at?

Regards,

Matt

Bill Verburg

Sure, all the guys i talk to that race these want shorter gearing


I'll also throw in my 993Cup g50/30, which in my mind is perfect for track use and very acceptable for street use.

Jimjacqmx5

Now for the next question.
How much performance gain could one expert for 0-100 and lap times with a set up such as the 3,4,5 Sergi with 0.96 5th gear. ie, would you expect a second per 60 second lap improvement.
(Obviously this would vary on circuit layout)

GTgears

I won't speculate on straightline acceleration numbers, but I think your track gains number is in the right ballpark. Figure around a second per minute of lap time.

sergiDA

I have finally thought that I need to change 4 gears ( 2nd to 5th) to obtain an adequate cruIsing speed with 5th combined with a very closed ratio from 2nd onwards. We will compromise on a higher drop from 1st to 2nd but since i don't race it is good enough.

I enclose the latest chart proposed by Matt at GT, I would apreciate your comments, Bill could I ask you to produce one of your great charts and tell me what you think?

Bill Verburg

This one is your last proposal, I don't like 3rd


here's yours w/ the 3 i'd suggest


w/ either 3500 in 5 is ~76mph and 2000 in 5 is ~44mph

Jim Richards

Bill, what do the colored lines signify on your plots? Thanks.