Blueman33

Our cars do 150-60 mph so they say.

At the track I drive there is no straight long enough for that, in fact the 14 turns in the track can keep you looking for power down low.

What gear would i change and to what specific size to lower the overall gear ratio which would increase my quickness at the expense of some speed?

If i can go 160 mph or 140 mph, it doesn't make much difference as i have to place to GO 160. I'd rather have more 'get up and go'

please advise, thanks

Ski

By the time you paid for the gear(probaly 3rd and 4th from Powerhaus II) and the labor to do it, you could easily buy a LSD tranny from the S2 model. IMHO.

billgot

The final drive ratio is the one to change. The S2 has a 3.87 to your 3.37 -1 ratio.Do you really want to hurt top end speed? You never know when you are going to need to out run the cops.

Blueman33

What I usually do with the cops as they approach at high speed is first hit the 'greasy oil dispursemnet' button to fling oil on the road behind me. I then immediately hit the 'highly flamable liquid' button to cover the road and toss a match out the top. They slide out of control and into a mushroom of flames. So with my anti-cop gear, I can afford to lose a little top end.

Blueman33

On a 1987 951, what would be the recommended specification of the new final drive gear?

And could I get more 'get up and go' with only a sacrafice of 15-20 mph?

87_944s

Hey Blueman,

You're talking about 'No Problem Raceway' I guess right...?

Given that the guys I know that run there haven't bothered addressing this as a problem, I'd guess that you're not exiting the final right hander as fast as they are.
What are your revs before letting off the throttle for the l/r chicane....?
I have yet to drive there to give any *real* insight to your problem but I guess I'll be there soon with what was really supposed to be my street only car... Have you talked to Jon or Byron that run there alot from the Mardis Gras region....?

Anyways, to answer your question, you'd want to figure exactly what range of revs you want to be in, factoring wheel and tire size which will affect your gearing. To change ALL ratios it'll be chaeper to change the final drive which is determined by the tooth count on your ring and pinion gear of the differential. To change ratio of a specific gear it'll be necessary to replace two gears, a mainshaft and countershat gear as a set.

Think about it like this- You have a ten speed bicycle.....
The front gear will affect ALL gears on the rear axle, this is akin to changing overall ring and pinion ratio.
If you kept the chain on the same sprocket in the front and physically change the rear gear to a larger size this will raise the number of revolutions required to to make the rear wheel rotate at the same rpm.
This is akin to changining a specific gear, like 5th.

I'm in the tranny biz, feel free to call or email me directly.
If you're set on raising revs I think your best bet is to find a 944S gearbox since the final drive is geared lower and you'd still have your original transmission intact should you decide to reverse what you did.
As another alternative you could use a 968 6 speed which would give you another available ratio that may keep you in the powerband that you wish.
I can put you in contact with a near-local supplier that would have each..

Terry S.
944t@bellsouth.net

<edit> accidentally posted under my son's username....

hosrom_951

So it is better to change the ring and pinion ratio in order to keep the same revvs right?

Blueman33

Yes, No Problem Raceway is the track.

I am a beginner driver so I'm not on top of the game. The best I could hit on the long straight was 110. I was told that a really fast car with a good driver could hit 130.

The track has turns you are doing at up to 70 (turn 1), then there's a hair pin turn (turn 4) which is a 30 mph turn. 14 Turns, 2 straights. Some of times I feel like just a little more bottom end would save me from a downshift and the corresponding upshift 2 seconds later.

I have a lightly modified car and will likely never see another track and don't plan on going 160 mph on a public street, so it seems the final gear would be an easy way to increase low end response.

My plan would be the final drive gear since it would more simple.

Let's say you put in a final gear and it decreased top end 10% from 160 to 145, would that make a noticeable difference in low end performance or just a waste of top end?

jyoon

i have read bad things about using a 944s ring and pinion in a 951. they eventually break.

Peckster

You'll see a lot more gain with increased seat time, rather than looking to modifications to your car to decrease lap time. Way more fun too!

Most of it happens in the corners, not the straights

944Willie

Another option is to change the rear tire profile/wheel. Around here it's easy to borrow a set from other racers, someone. It's easy to get a 3, 5, 7, even a 10 % change by changing to a lower profile tire/wheels. You could try a few laps and note the difference in power out of the corners and speed down the straights. After finding the combination that works match that to the what change in gears would be required. It's pretty simple after you do it a few times. If you have any questions I will gladly help you find the right ratios. Just remember lower series profile tire (same wheel) means more power out of the turns and less top speed. you may need to change a wheel size in conjunction with the profile change. This is for test use and again after you find the rear wheel/tire size works best, then you will know what ratio you need. Cheaper to change these than tranny's and pinions. Again this is just to see what works the works best/easiest. It is also easy to reverse if you change HP/weight, suspension, etc.

Matthew West

I read recently that you want to modify your gear box so that when you come out of the corner before the fastest straight you make it out of the corner and grab the next gear. When grabbing the gear you want your engine revs to drop so that you land near your peak torque point.

Blueman33

You'll see a lot more gain with increased seat time, rather than looking to modifications to your car to decrease lap time. Way more fun too!

Most of it happens in the corners, not the straights.
~~~~~~

No one is argueing that and no one, that is NO ONE follows that on this board. I have never seen a thread that says, "I am not modifying my car in any way whatsoever because track time will make me a better driver" even though it's true.

A totally stocked 951......wait i'll go further than that......a totally stock 944NA with a driver who drives on the track 30 hours a week will beat a 951 with 400 hp on my track. and yes, last DE there was a GT3 which never passed anyone that i'm aware of. so clearly seat time is better than moddin your car, BUT it's not one or the other.

My time in the seat will be the same whether I have 968 sway bars, lower gears, Vitess kit, test pipe or a totally stock car.

I see that a wider power band saves me a downshift and upshift through some corners.

So it is my contention that seat time AND mods to have a wider power band will be the best of both worlds since my track has no run that I can use a 160 mph car.