Calculating maximum speed

[AndyS2]

Does anybody know how you calulate speed using gear ratio's & revs?
The reason I ask is I saw a reading on my speedo yesterday ( on a private runway obviously!! )that I didn't think was possible and I wanted to see what I was really doing.

Andy

[AJLintern]

5th gear ratio is 0.778:1
Final drive is 3.875:1 (or so it says in my S2 handbook)
To work out the rotational speed of the rear wheels in 5th you do the following calculation -

Wheel speed = (Engine speed/0.778)/3.875

To get the speed you need the circumference of the rear wheels which you can find from the diameter x Pi
Then just multiply the circumference by the wheel speed to get the distance covered per minute. Multiply this by 60 to get per hour

So what did the speedo say??

[AndyS2]

Now I know I was cheating by going slightly downhill but I'm still impressed:-

Engine was redlining in 5th

Speedo reading just over 160mph

According to my calculations that's a real 155.5mph

The car ( Porsche 944S2 ) felt really stable and if it wasn't for the extra noise it didn't feel any different to 100mph. Incidentally on the way back it pulled an indicated 150mph uphill, on the same stretch of road...I mean runway...Officer.

Andy

P.S. New shape 325Ci's are really quick, but not quick enough!!

[AJLintern]

How was the accelaration up to the red line? Did it feel like it could go quicker if it had higher gearing?
Imagine 300+BHP and a higher final drive ratio

[pesty]

Never heard of a runway that goes downhill

[AndyS2]

Definatley would have gone quicker if it had taller gearing, I backed off to avoid the rev limiter!! I like the gearing as it is, gives good mid-range acceleration for over taking.
As for 300bhp, I check on this site a least twice a day to see if Ninemeister has posted any results from the QTB conversion!!

Andy

[AJLintern]

AndyS2 said: ...I check on this site a least twice a day to see if Ninemeister has posted any results from the QTB conversion!!

Andy

Yes me too! But I think he's snowed under working on those funny lightweight back to front cars

[diver944]

It seems there are quite a few of us S2 owners hanging on Ninemeisters every posting

I wonder which of us will weaken first and throw lots of money at him

[JamieBeeston]

I was wondering the same today...

is the digital/analogue speedo on my 996 calibrated, or overreading.

I ask as i seem to be doing silly speeds on the motorway, whilst my own brain speedo says otherwise..

maybe I am just used to the RAW TVR feeling...

car is evil tho, 130 in 4th, 150 showing with no issue at all, 160 was easy, pushing past that wasnt an option given the circumstance.. and all this with the roof down, v.v.impressed with the stability (tho dont stand on the brakes as it did induce some flex/wobble/lurch!)

but seems to have cured the rear pads smoking problem it had when delivered!

[dontlift]

Try borrowing a Road Angel - acts as a GPS speedo (very accurate) when not telling you about traps etc

Which reminds must go and get mine out of the car and update the database thingy off the net

>> Edited by dontlift on Monday 12th May 00:05