2.25 Max RPM?

[Jim-ME]

I have always been under the impression that max rpms the same rpms that peak HP is achieved. If I read the RN catalog correctly a 2.25 L petrol engine peaks at 4,250.

[yorker]

If you like to crunch #s this site has some useful calculators:
http://www.grimmjeeper.com/gears.html

[TeriAnn]

It could be on TAW's page but for some reason every time I start reading her site, I have the uncontrollable urge to just get in my truck and drive, or wrench or kiss it.

Funny, me too!

A lot of that web site was written just after I came back from a trip or just after a Land Rover wrenching session when I wanted to document something before I forget for the next time I have to do that task. Some of it was written in leu of driving when the fuel tank and my pocket book were both empty and some when I just decided it was too cold or wet to work on my Land Rover outside.

My next computer will be a portable. I suspect I will end up writing a big photo & text journal covering my travels. I don't know if anyone would bother to read it other than myself though. If nothing else I could continue to write my book while on the trail.

Actually, I've seen my truck at some unbelievable highway speeds and am really wondering what engine speeds I should be looking for in reality.

While I'm a firm believer in the concept that reality is what you make of it, I've noticed that reality is strongly influenced by physics. Why not put a tach in you Land Rover? A couple of wires, a couple of screws and about an hour or less and your questions are answered more accurately than taking a poll of people with different configuration Land Rovers.

Honestly, have you ever seen your truck read 85+ (very close to 90) while it was wearing 33" tires and in Roverdrive high? I think my numbers and experiences are probably acts of god, rather than what the truck was designed to do.

The Land Rover engineers detuned the 3.5 V8 they put into production Series IIIs because they wanted to discourage drivers from driving faster than 65 MPH in a Series Land Rover. You were driving outside the safety design parameter envelope

When I had a 2.25L engine in The Green Rover I mostly cruised along at 55 MPH. Now that I have a 5L V8 and taller gearing, I mostly cruise down the highway at 60 MPH. The nice thing is that now I do it in the mountains as well. I think the fastest I've ever taken the Green Rover is 75MPH.

But getting back to 2.25 engine RPMs, having driven for a couple decades with a tach & 2.25L engine, I have noticed that a 2.25L engine seems happiest between about 3000 and 3400 RPM with 3200 being the sweet spot. With 32 inch tyres this means between 50 and 60 MPH.

My 5L V8 likes to loaf around in the low mid 2000 RPM range so I have raised my gearing accordingly. I bet a Mercedes 617 diesel also prefers to cruise at lower RPMs than the 2.25L petrol engine.

Be nice to your engine and your engine will be nice to you ... hopefully

[Tim Smith]

Run it up to 65 without the overdrive this morning for you.
Looks like 3500 RPM's.
Looking to get me a 4000 RPM tach the 8000 RPM unit I had setting in the garage just doesn't cut it.
To me it was screaming for the overdrive.
Mine runs nice and smooth at around 3000 RPM's and can still pull itself up a small grade without loosing speed.

Thanks so much for testing that for us! I had no idea the motor was actually going so slowly at that speed. It sounds so much faster when you are behind the wheel.

[BackInA88]

Yeah it sures sounds like it is screaming!

[Alacrity]

2.25 petrol Peak HP seems to be right at TerriAnns sweet spot - 3200 RPM, but nice broad top. Slight continual drop after - Max a bit short of 4200 rpm

http://www.flyinmiata.com/projects/i...basil_dyno.pdf

Engine:
2.25l gas engine
Pertronix ignition
Flamethrower coil (who could resist a Flamethrower?)

Not a fresh engine - smoked blue - curves should still be fairly valid tho.

Plenty of discussion on BenzWorld and other MB boards regarding best efficiency rpm and speed, 300D and others.

Luck
Alac

[Tim Smith]

...I suspect I will end up writing a big photo & text journal covering my travels. I don't know if anyone would bother to read it other than myself though...

I'd read it!

TeriAnn, your website has provided hours of enjoyment and loads of information for myself and I sure others as well. Thanks for all the time you spend on it. It's great stuff!

...While I'm a firm believer in the concept that reality is what you make of it, I've noticed that reality is strongly influenced by physics. Why not put a tach in you Land Rover? ...

Agreed. I've actually got a new tach in a box somewhere. It's filed under "When there is nothing else to do, do this stuff" and unfortunately I've just been swamped for a long time now. One of these days...

...You were driving outside the safety design parameter envelope

When I had a 2.25L engine in The Green Rover I mostly cruised along at 55 MPH. Now that I have a 5L V8 and taller gearing, I mostly cruise down the highway at 60 MPH. The nice thing is that now I do it in the mountains as well. I think the fastest I've ever taken the Green Rover is 75MPH...

You obviously have not driven the Green Rover on the Merritt Turnpike...

However the instance in specific was while driving through New Jersey, after having just bought the truck in Florida. This was my first drive ever bringing it home to CT but it was tight and powerful and it was probably giving me a sense of superiority at the time.

I'm sure I've told this story to the board before but I'm a bit of an egomaniac and just loving talking about myself. So here is the story again.

---
Merging back onto the Jersey Turnpike after a fuel stop and I had a trucker giving me a hard time (tailgating) and as I came into the merge zone I had only one open spot between some other big rigs. They too were going a bit too fast but I had to make a run for it!

Having made that merge, at this point I was doing something on the order of 70 - 75. My next decision to move into the middle lane was what brought me up to "ludicrous speed" but I really wanted to get out of this tight spot between the trucks.

Cars were zipping by and a jeep got into the mix in the middle lane, waving his thumbs-up in the air. Although he was enthusiastic about the old truck, he failed to see that I was in a tight spot with some high tonnage trailing not far enough behind. So as he slowed down to get another look from the back, I darted out in front of him. His thumbs up quickly turned to outrage, and we were off.

Peddle to the metal, my truck was actually still accelerating but I had a beefed up Jeep on my tail who probably had more than twice my power to weight ratio and I now wanted to get away from him. Traffic is still passing me in the high speed lane, but I'm catching up pretty quick. And there it was, the opening I was hoping for. If I can get into this opening in the high speed lane, the Jeep will probably get blocked-in by the car coming up in the middle lane.

Floor it.. Floor it... Bingo! Slip nicely into lane 3, pass the car in lane 2 and then swing back into lane 2 and then 1 again. The car in lane 2 screwed everyone up and so I was no longer the hunted prey.

It was when I slipped out of lane 3 that I noticed the speed. I distinctly remember seeing the speedo waving well past 85 and into 90 territory to which I exclaimed something like "Oh sweet lord, what have I bought!?!" The gears made most of the noise but the motor was also spinning away like a rapped ape. It sounded like the world was going to end.

I also remember looking over at the car driving along right next to me and noticing the expression on their faces. There was none. They had no idea what was going on inside the rover right next to them. I was defying logic, physics and sanity and they could have cared less. They found nothing remarkable about the bouncing ugly brick-like truck albeit with a smoke trail following it at this point and the driver gripping onto the steering wheel, pale faced and yet flushing at the same time.

They just had no idea what life was all about!

It was probably as much my own machismo that got me going that fast as I did. I could have just jumped off into the emergency lane, or something equally sally. But no matter what you tell me, I still say to this day that this truck saved my life.
---

The motor didn't last long after that. It did had the twisty 2.5l cam and some other bits to make it go faster but unfortunately it also leaked like a sieve from every seal, burned oil and had a scary knock at idle. I've since switched it out with an old standard motor I had sitting around.

I'm now a mear mortal again.

...But getting back to 2.25 engine RPMs, having driven for a couple decades with a tach & 2.25L engine, I have noticed that a 2.25L engine seems happiest between about 3000 and 3400 RPM with 3200 being the sweet spot. With 32 inch tyres this means between 50 and 60 MPH.

My 5L V8 likes to loaf around in the low mid 2000 RPM range so I have raised my gearing accordingly. I bet a Mercedes 617 diesel also prefers to cruise at lower RPMs than the 2.25L petrol engine.

Thanks TA! Thats what I was getting at.

I think the 617 is a high revving diesel but again my tach has been broken the whole time I've owned it. So again not sure what it likes to live life at. I do however see that it goes up to 6 grand... Hmm

Diesel Giant has a good few shots of the motor in action.
http://www.dieselgiant.com/diesel_videos.htm

...Be nice to your engine and your engine will be nice to you ... hopefully

Yes! Don't fly too close to the sun folks.

You might throw a rod.

[Jim-ME]

If I remember correctly any engine is happiest at 80% of it's max rpms for peak HP and it's HP for max torque. That is what is refered to as the power bandwidth. If you stay in the range your engine will be working at maximum efficiency(sp?). If you use 4200 rpms you get 3360 which isn't too far from the 3200 sweet spot which has been posted.

[TeriAnn]

I think the 617 is a high revving diesel but again my tach has been broken the whole time I've owned it. So again not sure what it likes to live life at. I do however see that it goes up to 6 grand... Hmm

Just because people can build an engine that rev's to 9 grand doesn't mean that it lives long there or gets its best fuel mileage there.

OK, I just took pity on you and spent 5 minutes doing a web search for Mercedes 300TD gear ratios & stock tyre diameter then ran the numbers. The Mercedes factory engineers gear the 617 engine to turn 3000 RPM at 65 MPH. That should be your target RPM for top gear.

A quick look at the gear charts and the perfect set up would be the drive train from a early US spec V8 Discovery. Find a LT77S with its LT230 from a mid '90's Disco I, grab the 3.54 R&P, order a pair of CV joint Series front axles from HEYSTEE Automotive Components (Netherlands) and you are in business with full time 4WD and Mercedes factory top gearing.

Stock Series ratios wil have you running about 700 RPM too high. Stock with 4.1:1 R&P has you running about 200 RPM too high (but is ball park enough to work if you don't mind the higher low range ratios). An Ashcroft kit in a stock drivetrain is about 300 RPM too low. The engine will be more sluggish below about 75 MPH (!).

You know I really need to add a chart for Roverdrive ratios. I just ran the numbers for a Roverdrive. A Roverdrive will put a 617 engine in the sweet spot at 65 MPH with a stock series drive train. You ARE installing 24 spline rear axles, right?

OK so you have 2 choices for best gearing for the 617 engine.

1. Stock Series drivetrain and a Roverdrive
2. Stock V8 Discovery LT77S drivetrain with CV front axles.

The LT77S is the stronger gearbox and you just have a single lever to shift. A Roverdive is your easiest & cheapest solution assuming Roverdrives are in stock.

[jp-]

Just because people can build an engine that rev's to 9 grand doesn't mean that it lives long there or gets its best fuel mileage there.

Yamaha has come out with the new R6, with a redline of 16,500. They say that driving it at that RPM is like shooting heroin into a vein. You just can't stop. I think it has Titanium rods and valves.

All I know is that I'll have one eventually. And yes, it will spend most of it's time above 12,000.