19 replies to this topic

[KernowCooper]

Some have buts its a difficult job and faster and easier to whip the engine and box out and change the final drive ratio, and lots more space.

Edited by KernowCooper, 06 May 2013 - 05:03 PM.

[Cooperman]

The holding back in top is called a failure to overcome the drag curve. Aerodynamic drag increases as the square of the speed, so to go twice as fast requires 4 times the power. However, that is an over-simplification as there are other factors and if you are not bang on the torque/power curve when you change into top the increased 'grunt' needed to overcome the drag curve will not be there, however much nominal power the engine has.
My advice is to drop to a 3.44:1 FDR. Once the engine is out you can take the diff. casing off and the gearbox end cover (which carries the speedo drive) and, hopefully undo the pinion nut. This can be a big problem, so best be warned before the start and I've resorted to taking the engine off the box to do this job, fitting a new clutch plate and big-end, main and thrust bearings at the same time. Really it's a weekend's job and well worth doing. With a 3.44 FDR the speed at 5000 rpm will be about 85 mph, but it will get there very easily with your engine spec., especially if it is set up correctly.
Remember this will make the speedo under-read and you can either work from the revs or have the speedo re-calibrated.

[coopdog]

The holding back in top is called a failure to overcome the drag curve. Aerodynamic drag increases as the square of the speed, so to go twice as fast requires 4 times the power. However, that is an over-simplification as there are other factors and if you are not bang on the torque/power curve when you change into top the increased 'grunt' needed to overcome the drag curve will not be there, however much nominal power the engine has.
My advice is to drop to a 3.44:1 FDR. Once the engine is out you can take the diff. casing off and the gearbox end cover (which carries the speedo drive) and, hopefully undo the pinion nut. This can be a big problem, so best be warned before the start and I've resorted to taking the engine off the box to do this job, fitting a new clutch plate and big-end, main and thrust bearings at the same time. Really it's a weekend's job and well worth doing. With a 3.44 FDR the speed at 5000 rpm will be about 85 mph, but it will get there very easily with your engine spec., especially if it is set up correctly.
Remember this will make the speedo under-read and you can either work from the revs or have the speedo re-calibrated.

Ah righttt

I'm going to leave it as it is,
The engine is goning to be turboed soon and I think I will have enough torque then :L

[Cooperman]

Yes indeed. A well set-up turbo-charged engine should have a fairly wide torque band which will overcome the problem.

[Alex_B]

my 998 with a 3.44 fd managed in standard form regularly above 80-85 and once managed a tonne on a downhill stretch with the wind! it was a bit of a struggle and it was a long stretch but it got there but the 3.44 feels like a good compromise as acceleration and top speed are both fine :)