Originally Posted by Williami22
Okay, Thank you both. The RPMs were hovering around 2000-2200. I am pretty sure the instrument panel needs some work done on the connections or replaced. The gas gauge worked, speedometer was slow to change (did not instantly drop when braking) and the temp gauge did not move much at all. Hopefully the tach. was accurate on the RPMs as I would really like to get at least 60 out of it haha
So if you approach this logically you can work it all out without getting frustrated.
You need the info from the rear axle housing that tells you the Final Drive Ratio.
You need the tire size.
You need the gear ratios in the transmission (easily found online)
You need an accurate speedometer (GPS works well).
With any three of those four you can calculate the other one. You can calibrate your speedo with the GPS, you can work out the revs with an online calculator once you know your tire diameter, FD Ratio, speed and gear ratio.
If any are off you can fix them.
You can then calculate your maximum speed at you maximum engine revs.
If the bus won't get to it's maximum speed, or close, then the engine is governed, probably electronically and this is easily remedied.
If the max calculated is less than you want, then you have a bigger problem to solve.
Most engines can take a few more revs, so that's one way, but you don't want your engine at maximum revs when cruising. The other way is to raise the FD Ratio (lower its number) from, for example 5.38 to 4.44.
That would give you quite a bit more speed at cruising revs at the expense of some acceleration. It costs quite a bit but would transform the bus.
Here is an excellent calculator: