Hi all, I haven't been active on this forum for about 3 years but I did get a bunch of excellent advice about buying my first diesel. I am about to start a unique project and need some technical help. I live in Florida, where hurricanes and power outages rule the day. My plan is to purchase a PTO generator and power it with a 240D engine. The generator requires 48HP at 540 rpm to generate 200 continuous amps. I have purchased a running 240D from my local MB shop and am in the process of removing the engine and tranny to hook up to the generator. My problem is that I can't locate an accurate torque/horsepower curve for this engine. I know that max HP is 62 at 4000rpm and max torque is 97Lb/Ft at 2400, but I need to know exact HP or torque outputs at various rpms. I also need to find out the gear ratios for the attached 4spd trans. If anyone has this information, or knows where to get it, I would be most appreciative!

Hello Clint
Your best approach is to build the 240D generator.
Slowly put it under full load while watching Volt/AMPS/RPM and step up RPM as needed + make notes of what RPM = which load.

Please note:
You will need a signal conditioner to preserve electronics in the house.

:EDIT:
Thank you "leathermang".
Going to fast and assuming too many things.
Allow me to clear up what I was trying to communicate.
#1. Build it to run off the transmission output shaft.
#2. Take lots of notes and pictures, some of us might want to duplicate what you are making.
#3. Rough your RPM into range with no load.
#4. Start applying electrical load.
#5. Mark linkage positions for required load levels.

What you really need is a loader/unloader, similar to a cruise control, this monitors generator RPM and adds engine power or removes engine power to keep a constant speed.

Central A/C power spikes are hard to smooth out on a generator

You should find 500 - 1500 engine RPM variation no load to full load.

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To find the ratio for your particular transmission... place a ' degree wheel' on the crank pulley and on the output shaft of the trans... then turn the crank one,ten, a hundred, or a thousand revolutions... with someone counting the number of turns the trans output shaft makes.... all depends on how accurate you want to be....

Hunter, I think he knows he needs the generator at 540 rpms and needs to know what speed to run the engine for long life... does not want to ' lug' it... and he does not have much spare hp to waste....

I suggest you leave the car intact... and just cut a hole in the trunk... mount the generator in there and run it off a sheave bolted to the input of the third member.... since you have a four wheel independant suspension the distance from the solidly mounted third member is fixed with relation to the floor of the trunk...

Something to be aware of. I've read Diesel engines last longer when they are being taxed. ESP. when at a constant load like a generator. If you dont have the engine opperating at a RPM that puts a load on the engine you increase the risk of coking the injectors, rings etc.

On a car this coking does not happen as easly because of the moving thru the power band compared to a generator that just stays at one RPM.

With this in mind sounds like your generater head wanting a lower HP than the engine puts out you may have a problem. That being said though from what I have read some suggested that an occasional alcohol injection or water injection might be help clean things and could maybe avoid the coking problem.

Why dont you run this thing on Waste Vege oil fuel?

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The info that you need is as follows:

I am not positive of the torque curve of the OM616, however, I am going to assume that it is flat between 3,500 and 4,000. If not flat, then the torque would be falling off a bit and the numbers below will be on the conservative side, which is preferable:

If the engine puts out 62 hp @ 4,000 rpm, it will put out 48 hp @ 3,100 rpm.

So, in theory, you could run it as low as 3,100 rpm and still get the power that you need for the generator. However, power figures being a rating for a new engine, it would be my recommendation to run the engine between 3,500 and 4,000 rpm to ensure that you have sufficient power available.

So, if the generator must run at a constant 540 rpm, you will require reduction gears of something between 6.48 and 7.40. A ratio of 6.48:1 will allow the OM616 to run at 3500 rpm and a ratio of 7.40 will allow the OM616 to run at 4,000 rpm.

I believe that it will have sufficient power at 3,500 rpm, and, for longevity, it would be preferable to run it there, if the engine is not too old and the power output is not degraded too badly. At 3,500 rpm, you would have a minimum of 54.25 hp available. You might have a little more if the torque curve is falling between 3,500 rpm and the data point at 4,000 rpm. This should provide you with enough margin to prevent cooking the engine prematurely.

So, your ideal gear ratio would be 6.48:1. Anything up to 7.40:1 would be acceptable. Note that there are no automotive gearboxes with a first gear that is that low. The typical first gear is about 3.5:1 or so.

You still have the option of running the engine slower and accepting less generator output. Nothing says that you must have full output from the generator if you do not need it. So, if you ran the OM616 at the torque peak (2400 rpm) you would have 44 hp available. If you did not want to fully load it at this speed (or if it is not brand new), you could assume that 38 hp would be useable. This still allows you a decent output from the generator; about 158 amps.

But, you still need a reduction gearbox with a 4.44:1 ratio to allow the engine to run at 2400 with the generator running at 540.

I would strongly advise against running the engine at less than 2400 rpm because the fall off in torque below 2400 will cause a massive drop in the available horsepower, and you would have a large generator that would not put out very much.

Thanks for all the good information. I'm sure I will be asking for more as the project progresses. I thought of leaving the car intact and mounting the generator in the trunk, or even the back seat, it would certainly look nicer parked in the driveway! My only problem is where do I put the 300 gallon fuel tank? I'm planning to mount the engine, generator, and fuel tank on an old boat trailer so it will be mobile.

Clint,

Why buy a generator that is designed to run off a tractor power take off at 540 RPM? Get a generator designed to run at 3600 RPM and run it direct drive to eliminate the transmission and its loss.

You will also need a governor to keep the speed of the engine steady under varying loads.

P E H

PEH is right on the money with this, Clint. I'm not sure how most automotive gearboxes would hold up with 50 hp continuous going through them.

A 3600 rpm generator is far more preferable, unless you already have the 540 generator and it cost you peanuts.

Having just looked at a 92 KVA generator set, I'd say that is the way to go. Especially one set to run on LP or natural gas like the one I saw.
The maintenance is so much less than one powered by a diesel engine it will be highly appreciated after 8500 hours operating time (one year).

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Unless you plan on going into the power generation business your generator is never going to operating at the 50HP level. I have a 12kW standby generator with a 30hp V-twin engine and I've never even come close to taxing it. If you just remeber to limit yourself to two 240V appliances at the same time (which IMHO is not all that much of a restriction) 10-12KW will be just fine for standby power.

I like the idea of keeping the engine/transmission in the car and mounting the generator head in the trunk. If the cruise control works you could also it as a generator load governor!

All in one neat package that you could push around with an old garden tractor.

Clint,

Tim is right about not ever using the full capacity of the gen. set. I have a 20kw Lima generator powered by a 3 cyl. Yanmar engine. I paid $527 for it as the company where I work. It only had 300 hrs on it. My house is about 3,500 sqft. and has about 7 tons of ac. I never have maxed out the generator and during the last outtage even shared some power with both neighbors.

You can run your 540 rpm generator off your Diesel engine simply by using a double of tripple set of pulleys and C section v-belts. Make a steel frame to mount the gen., engine, switch gear and fuel tank. You don't need 300 gals. My unit uses about 8 to 10 gals. a day. Check at Diesel welding machine repair shops for governors.

As I am sure you know you can get 540 rpm gen. with about 15 kw plus switch gear for about $1,600 from Harbor Freight or Great Northern. What you save using this unit you may spend in fabrication. A 12 kw can cost upwards of $4,000. Check equipment trader catalogs at your local Circle K. Check equipment auction companies and the news papers for construction co.s going out of business. Unfortunately in Fla. after all these storms these gen sets will be like hens teeth. You could take off a few days and go north to some place like Ohio or east to Houston and probably find a deal.

Even more to think about! I hadn't thought of looking for a genset that runs at a higher rpm, I just stumbled onto the PTO generator in a Northern Tool catalog. I want the large fuel tank though in case of extended power outage after a hurricane. There are some folks in Charlotte county that still don't have power since hurricane Charlie, over a month ago! I know that isn't very likely but the thought of living without power for an extended period just scared me to death. Post hurricane cleanup is very labor intensive and having a cool house and hot shower can make it a lot more bearable.
I will investigate alternatives and keep you all posted. Thanks again.

There’s a place called sky craft in winter park that sells Electronic surplus.
It will probably have all the Electronic parts you need
http://www.skycraftsurplus.com/

Neat place to brows too