Rover 2,25 a high rev engine?

[Richard]

I'm still contemplating an overdrive, but on an Aussi land rover forum someone says "that all of these engines were designed to operate at high rpm". For that reason he's not a fan of overdrives. But would you describe the Rover 2,25 petrol engine as a high rev engine? In the specs the Series 2a engine is described as: "OHV - 2286cc - 90.5x88.9mm - 7:1 - 3 bearing - 50Kw@4250rpm, 157Nm@2500rpm." So it's almost square. But for a high rev engine you would expect the bore to be (significantly) greater than the stroke, right? And also, a max torque of 157 Nm at 2500 rpm, is not exactly high, is it?

Richard

[Wittsend]

I wouldn't take the word of one person on a forum 

Land Rover petrols are not "race tuned" engines, they are not sluggards either.
There are a few performance "upgrades" you can make to the early 7:1 engines, but they are not ever going to be racing cars. There is some merit in increasing the comp ratio to 8:1 but that's as far as you can go with the low comp head casting. If you want more performance you could always fit a V8.

Look at it the other way ... many, many owners have fitted overdrives with great benefit and never regretted it. They increase the overall gearing by about 30% and greatly improve the "cruising" by lowering the rpm and the concomitant reduction in engine noise. But you won't get more mpg or mph, just relaxed driving.

[whitehillbilly64]

Hi Richard.
Im in The Tweed Valley, Northern NSW.
I have a OD fitted to my S3 Daily. So do mates locally, who have Series Land Rovers.
Purrs at 90klms. Can even have music playing.

whitehillbilly

[ChrisJC]

I've just fitted an overdrive to a Mk1 Ford Transit. The difference is phenomenal.

Chris.

[Richard]

Thanks all. I'm not pining for a Land Rover Veyron, I was just wondering about the "designed to operate at high rpm." A more relaxed drive, especially at motorway speeds is what I'm after. Mine doesn't purr at 90 km/h, if anything, it thunders, rattles and whines. Someone playing music at those speeds – and hearing it, I presume – is music to my ears I haven't got a rev counter, and my electronic ignition is not the kind you bluetooth to a smartphone or laptop, so I can only guess the rpm's I'm driving at. The speedo is just there to cover a hole in my dashboard, I use a GPS-speedo on my phone and at 50 to 55 kmh I'm in fourth. I think I hit 90 once, but it was not a pleasant experience...

Richard

[Genocache]

90kph=55mph, I've had a petrol 88 up to 73mph and a diesel 88 up to 64mph. I couldn't hear music at 55mph let alone above! My 109 with 200TDI I've gotten up to 72mph on the flat, I don't think I could hear music at 40mph. For longer than an hour drive I wear ear plugs. I've insulated the bulkhead, seatbase, floor, doors, roof.

[Peter Holden]

Land Rover described the 2L diesel as a high speed diesel in 1957 when it was launched.The handbook for our 59 2L diesel gives the top speed as 62 mph

My 2.25 diesel with 750 tyres and overdrive will reach 70 on the flat (using a GPS speedo) but it is much more comfortable at 60 to 65.

Peter

[Craig T]

Using the Ashcroft gear calculator it seems my 109" Land Rover all standard gears, no overdrive being driven at 55mph, the engine is revving at around 3250rpm. 60mph is 3500rpm
https://ashcroft-transmissions.co.uk/ratio-calculator/

I don't think it goes much beyond that to be honest, I certainly wouldn't call it a high revving engine.

Craig.

[Gareth]

Using the Ashcroft gear calculator it seems my 109" Land Rover all standard gears, no overdrive being driven at 55mph, the engine is revving at around 3250rpm. 60mph is 3500rpm
https://ashcroft-transmissions.co.uk/ratio-calculator/

I don't think it goes much beyond that to be honest, I certainly wouldn't call it a high revving engine.

Craig.

I'll say these are correct. I used to have an electronic rev counter fitted, and 55 cruise was 3250. The max it would rev to when really giving it beans through the gears was about 4100 I seem to recall. Most cars of the day would have the red line at about 5-5500 rpm. So no it's not a high revving engine in my opinion. It's a good slugger though!

[Robin]

....... so I can only guess the rpm's I'm driving at.

The Ashcroft ratio calculator is useful to work out RPM/MPH
HERE

All things being equal, a 2A with everything standard, 90kph would mean your engine is spinning at around 3300rpm in 4th.

Robin.

EDIT: Beaten to it by Craig!

[Richard]

EDIT: Beaten to it by Craig!

Only by a minute, not much, when you're in a Land Rover

Thanks for the Ashcroft. Interesting. And the standard diff ratio for a Series Land Rover is 4.7:1? Is there a way of knowing what diff you have, except marking wheel and prop shaft, turning the wheel a full turn and counting the prop shaft revolutions? Is there a tag, a code, a number somewhere on the diff? Ashcroft also lists a 4.75:1. I'm afraid turning wheel and counting prop shaft revs won't permit me to tell the difference between a 4.70 and a 4.75...

On the Roversnorth forum TeriAnn Wakeman, of Expedition Land Rover fame, says 3200 to 3400 is the engine's soft spot (and she goes on to explain rpms and shift points under different circumstances).

So, if my S2a is bog standard, with a 4.7:1 diff and 31.8" (7.50) tyres, at my normal cruising speed of about 85 (53) to 90 (56) kmh (mph), the engine would be spinning at around 3200 rpm...

Richard

[autorover1]

When these engines were designed, late 1950's they were probably looked on as high revving, being virtually square ie equal bore /stroke. This was after in the UK, the tax regime had promoted long stroke engines.  By modern standards they are  not high revving by any means and max torque is round the 2000- 2500 rpm range  which is where the Overdrive comes into its own giving 50/60 mph . 

[NoBeardNoTopKnot]

I'm not sure what this thread sets to establish? It's all vastly subjective. To finalise my closed-loop fuel set-up, I recently did a rolling-road session.

In 2.8 later 5MB form and peak power these engines push 4100-4200 rpm. In modern terms that's v.low.

On gear-changes etc, I can run mine at over-run to 4500. This borders abuse and there's little point because power ends after 4000ish anyway. Hence I don't.

In day-to-day, peak torque comes in at 2300ish. With nearer 40bhp more than stock, I reckon to have the ultimate power-train for a Series, yet... even in this form rpm matters not.
The 2.25 engine is a cooking-vanilla power plant, never a racer. In the form I use mine it's set-up to pull far more air than most, and still the rpm is pretty much irrelevant. Running an O/D or higher ratio will drop noise a little, economy and noise will be suffer if you don't. But not by much...

if it's noise that worries most, there's far easier and cheaper ways to reduce this than any O/D, and when they're tired - and many are- they add noise. Factor in their cost....  more for one in decent order - and the fine if you want one. Poseurs will pose. Only the idea you'll save money is not thinking it thru'.

[w3526602]

There is some merit in increasing the comp ratio to 8:1 but that's as far as you can go with the low comp head.

Hi,

My last S1 with OHV engine would scream down the "Glynneath Bank", "off the clock", and the scenery a blur, like the "Millenium Falcon" going into Warp Drive.  A neighbour complained that he was unable to catch me, on the flat, in his 1.3 Ford Escort. Happy Daze!

Er ... what are the physical differences between S2 petrol and diesel engines ... BHP v BHP ... compression ratios ... shape of combustion chambers ... shape of pistons, etc?

Just wondering how the diesel is able to accommodate the much higher. compression ratio?

Memory says the LR DIESEL is an INTERFERENCE engine ... you can not (must not!) turn the engine unless the timing chain is connected. Is the petrol engine also INTERFERENCE?

Does anybody know the difference between the 4-pot Rover car engine (nominally 80BHP) and the similarly based Land Rover engine (72BHP?)

602

[NoBeardNoTopKnot]

Does anybody know the difference between the 4-pot Rover car engine (nominally 80BHP) and the similarly based Land Rover engine (72BHP?)

I don't however I can make a pretty informed guess. In such a cooking-grade state, there's vast headroom in these engines for more air to be put thru'. It's never hard to get much, much more out of them. In stock form they are so strangled it's easy to remove the bottlenecks.

By the 70s a 2L engine would be expected to put out 90-100bhp (at the flywheel) and give 25mpg. Thus our 2.25 80bhp (at the flywheel)  and 20mpg is pretty poor. My breathed-on 2.8 does 105bhp ish (at the wheels), my guess 115bhp ish at the flywheel?

In 2.25 form using the same tricks (big-valve head; SU; cam) we can expect 95ish just as easily. We expect over 200 in modern closed-loop set-ups. With not much more than ditching the stock inlet manifold and love for the Zenith, I suspect 80bhp would be a piece of cake.