Thread: Max. engine revs.

Maximum RPM's is when the governor stops it revving

Roadspeed RPM's vary on gearing and tyre size only, its likely if your both running similar size tyres your tacho is out, as they are driven from the alternator, which can be inaccurate as different pulley size, alternator windings will have an effect

Hi rovercare,
Had the same tacho readings when I had similiar size tyres. Has never been a high reving engine(2500rpm max), lucky to get 110kph out of the vehicle. Also engine does not perfom like my nieghbours. Not as free reving or responsive.
Regards Shane.

Hi Shane, what RPM at idle? Is yours an auto?What year is yours and what year is your neighbours?

JC

My 300TDI auto does 100kph @2250rpm and 110 @ 2500rpm, i had never had it past 3200 untill about a month ago, then on a highway trip i needed to overtake some slow traffic and got to 4000rpm.

Hi JC,
Mine is a '96 300 Tdi (with an engine prefix of 20L) manual.
My nieghbours is a '95 Tdi (with an engine prefix of 18L) manual.
My idle speed is approx. 700 R.P.M. Not sure at this stage of the '95 model. Also mine does not feel as responsive at the pedal. Will test on Sunday on a certain hill on our travels. Will have more to report then.
Regards Shane.

i have a 12/95 disco and it sits on 2750 @ 100k (i suspect a wrong sized serpentine belt) and about 700 at idle.
i dont take mine above 3250 at the max and generally operate it between 2000 and 3000 rpm goes quit well in this rev range

A simple way of determining the actual revs of a engine is to make a vibrating wire.
Made by cutting a length of tubing, some old brake line is ok for this although it must be straight.
Then some stiff wire that just passes firmly through the tube and protrudes out each end.
Hold the tube against the side of a motor running at 1000 RPM, move the wire through until the free end resonates (vibrates), finely adjusting the wire for maximum effect, then mark that point on the wire.
Take the setting and do the same on the engine that needs verification of it's tacho. If the tacho is correct, the wire will resonate the same as before.
If not, the motor needs to be varied slowly up or down in Rev's until the wire resonates at it's maximum, take note of the tacho reading. at this point you can calculate the difference in rpm and / or the error of the pulley size on the alternator.

See how you go, I want to know how reliable this test can be!!
.

Hi All,
More to report, Engine only flight reving to 3500 on mine & 4600 on nieghbours. Have to drop 1 gear to retain same speed as nieghbours on certain hill running out of Melbourne. Also empty trailer (6X4) knocks top end performance about. Arthur, would mesuring Alternator pulleys do the same as the vibration test as I am running the longer (1595)of the 2 different belts as the short one (1585) would squeal after a short period.
Regards Shane.