Vitesse Rev limit

[Gengis]

Can a mk2 Vitesse 2.0 engine safely rev to 6000 rpm? It has forged pistons and shot peened and tufrided crank and rods with arp bolts. Also what would I need to do if I wanted a rev limit of 7000 rpm. Thanks

[GT6M]

biggest problemo in sustained High rpm stuff is  no1 bearing running dry

a few things can be done t,sort it though,

 

bar that, the 2L is a revver so short burst there really should,nt doo ne harm

 

just use  good oil, change oil an filter moer often, adjust rockers moer often

 

[Nick Jones]

My internally standard Mk2 engine saw the far side of 7k on a few occasions, albeit briefly (thought I had the rev limiter at 6.2k but turned our to be 7.2k - ooops!).

On your stated engine spec I'd say you are good for short duration 7k already but I wouldn't recommend holding it.  I have an external oil feed pipe on my newer engine to send more oil to the front of the main oil gallery.

Can be done in braided flexihose if preferred or done more elaborately with feeds to every main bearing drilling plug (google Kastner octopus)

 

Nick

[Blitz]

Stop making us little guys jealous. I can’t get that down hill with a tail wind 🤪

[Nick Jones]

Should be able to get 6k in first and second.......  Third presents legality issues on the public highway, though we were finding it quite regularly on the track a couple of weeks back even with a 3.63 diff. Didn’t quite get to it in 4th though.

Nick

[ahebron]

My 1600 would go to over 7000 when the throttle would jam.

The frightening noise that accompanied this was the metal fan blades hitting the bottom tank lip of the radiator.

Killing the motor and restarting cured the problem till I found the issue. It was so long ago I cant remember what the issue was though.

Adrian

[JohnD]

The problem with revving a Triumph six is the stroke.

Consider that a piston will go from stationary at TDC and BDC to traverse the stroke in one two hundredth of a second at 6K.    For a 2L engine, the piston will accelerate at just under 20,000metres/sec/sec, two thousand times the force of gravity on the surfuce of the Earth.   A 2.5L's piston has to travel  another 19mm in the same time.  Doesn't sound much, but the acceleration there is just under 25,000 m/s/s, two thpuasand five hundred time gravity on Earth!      A 2.5L piston weighs 346 grams on the bench, but under these conditions it 'weighs' nearly a tonne!

The calculation of acceleration is not trivial, and more usually the mean piston speed is used, a far simpler sum.  That gives these tables

2L, 76mm stroke

RPM	Mean speed in mm/sec	Mean speed in meters/sec
6000	15200	15.2
7000	17700	17.7
7500	19000	19.0

 

2.5L, 95mm stroke

6000	19000	19.0
6500	20840	20.84

 

It is a 'rule of thumb' that without exotic materials, a conrod will not support a mean piston speed of more than 20m/s.   As you can see, while a 2L doesn't exceed that figure at 7.5K, a 2.5L reaches the same limit at only 6K.     

It is safe to use 7K in a 2L, although such use regularly would benefit from careful preparation, lightening and balancing the pistons as much as possible and treating the conrods by grinding, polishing and shot-peening them.    A 2.5L will not survive long at that speed, without more radical mods, including steel rods and crankshaft.

John

 

[Gengis]

Thanks for your comments