Tach-MPH question
 

Hey folks. My speedo is broken (on the to do list) and I will be driving cross country soon. Could someone post 5 th gear speeds for various driving speeds so that I can be reasonably sure how fast I am going by watching the tach?

I drive around 65 (ish) to save gas usually.
I think the 5th gear on a 924S is slightly different than a 944, but 944 info will prob be good enough. I have stock size tires on stock rims.

Thanks.

A chart is given in the owner's manual; If someone has one maybee they can post it. Otherwise, maybee just conside picking up a GPS - I've seen some Tom-Tom ONE models going for less than $100.

Around 2500 RPM. How lax are your cops?

I have an owners manual at home, I'll check it tonight.

on the road again...
 

Slam: Will be driving from CA to TX, How lax are NV, AZ, NM, and TX cops to Porsches from California? Needless to say, radar detector in hand. Driving slowly.

2500, is that all? OK dokey.

JPK: yea, I might have a GPS, but for the 100 dollars I would rather just fix the speedo, ha ha

The 944 5th gear IS substantially different than the 924S 5th gear. Id say about 400rpms worth of difference. at 60mph. While a 944 will sit at 3000 rpm at 70mph my 924S is usally around 3300 to 3500 rpm if I remember correctly.

On 195-60-15 tyres , work on about 23.5mph/1000rpm in top for the 924S.

i.e. about 2750 rpm = 65mph. This ratio is from memory, check it with the table in the handbook.

er....
 

I don't have a handbook. The PO forgot to leave one in the car when he abandoned the vehicle after it broke down.

Shumi: around 3300, K then.
Petrolhead: 2750, K then.

Well folks, we are narrowing it down.....ha ha.

I have 205/50/R15 tires.

after doing a bit more math, 60mph should be more like 3000rpm.

Don't you guys all drive 55?

Porsche recommends drivers follow all posted speed limits.

I'm usually at 55 in 2nd gear.

What speed limits? Are those the funny looking white signs on the side of the road with some kind of scribbling on them?

my 944 auto (w/o overdrive) is running 3000 revs at 60mph in top gear...

Would expect a 5speed to be substantially lower. the gear ratio for the auto is 1:1 but the gear ratio for the 5-speed OD is ..83 according to clarks. therfore a 5speed would be running ..83x3000=2490revs at 60mph. (unless the axel gear ratio is different between the auto and 5sp) this is for a 85.5

55? what roads are 55 anymore? Oh wait, lettered highways. Well, who drives the limit on those anyways.

Early this summer I spent a week in southern california. Early morning rush hour, on the I10, speed limit is 65 to 70... people are doing 90 like its no deal. Now here in Missouri the standard is 10 over. If you are not doing 10 over then you are getting passed. But 20mph over the limit? It was crazy. I loved it. It is the real reason they do not raise speed limits. They know people already do 80 to 90, why let them add another 10 to that...

going with the flow
 

Shumi: that's Nothing! there are feeder highways like the 405 and 10 coming into LA LA land that regularly get to 90 and above as commuters rush to beat the morning rush. One morning I had to go over 100 to keep from getting run down by Ma and Pa Normal in thier minivan!

OK, around 3K then as a cruising speed. Give or take depending on traffic and conditions. I am noticing that Blinky is getting better mileage as the engine gets more and more used to running. This car has Sat since at least 2003 and possibly 2000 so I am staging up to a cross country trek. The top speed is not a problem. I just don't want the car to get away from me as it tends to creep up on the speed a bit if I don't pay close attention

When did you last change your belts?

The speed limit on I-40 ( Arizona & N.M.) is 75 and even the big trucks are going like 80, lookout, you feel pretty small when one of those suckers is pushing your rear bumper. What's wrong with your speedo? Putting a new cable in is not that hard and could save you from a speeding ticket fine. Also, you get a portable GPS for around $100. that will tell you MPH. Good luck.

fresh belts
 

Shcumi: changed belts last week.

Fixing the ODO is a lower priority, I did the belts, OC seals and CLutch. It is now time to go. If I waited until I had everything done, I would never get out of here.

2100rpm=55mph. 2600=65 round about.

1800 in 4th=near 35 mph.

Not from book. From the guy driving behind me with a cell phone in his hand yesterday :D. Maybe it'll help a little...or give ye an idea fer getting your numbers ;)

You're local to me - I have several spare speedos if you're interested.