Hotrodding a small diesel

[EKlem]

I am working on power generation for a formula hybrid SAE race car. The team has agreed that we would like to run a diesel if at all possible. What I need to figure out is whether we can practically do this or whether we will need to go gas to get the power to weight. Ideally, the engine weight will be about 50lbs which really limits our options. I am looking at a couple of engines including the Yanmar L48AE-D and the Hatz 1B20. Both engines are rated at just under 5 continuous horsepower. Our simulations indicate that we need to sustain almost 12 horsepower.



My question is do you think that it is practical to expect either of these engines to last a racing season at 2. 5 times the rated power output? Both are air cooled so we would need to be adding a lot of heat sinks to them. They are also naturally aspirated so they would be getting turbos. I do not know what the fuel systems are like and how hard it would be to turn them up to flow a lot more fuel. I think that my biggest concern is related to whether we will be able to keep the engines cool at these power levels. We do have an engine dyno so these engines would be hooked up to several temp sensors, egt's, boost, etc and run hard.



Any thoughts or suggestions? Does anyone actually have experience with any engines in this size range?

 

[Vaughn MacKenzie]

One immediate problem you'd be dealing with is EGTs, I doubt there is piston cooling. If you could add more oil pump capacity and a small jet you should be able to do that, then add some heat sinking to the crankcase area to cool the oil or do an external cooler.

Another way to get more HP is spin it faster, 3600 looks pretty conservative for a little motor. Could lighten the piston some (shave some off the top to lower compression too), polish and shotpeen the rod and run it to 6000 or so. Piston work would have to be done with care, make it too light & you'll compromise structural integrity.

I could see you maybe getting 8-10 HP out of it but 12 might be a stretch.

Another idea, how about some sort of turbine. . . might be difficult to find a small, suitable one and to integrate it into your vehicle. And the fuel economy may not be that great either.

 

[Vaughn MacKenzie]

Here's a guy with a minibike powered by a Yanmar diesel :-laf

 

[tempforce]

have you thought of using a high compression (12-18:1) engine using alcohol

 

[EKlem]

The fuel sources that we are allowed are biodiesel, E-85 or 93 octane pump gas. We cannot inject drugs but it looks to me like water injection should be legal to help keep things cool. We have a full machine shop at our disposal so making simple stuff shouldn't be too hard.

Vaughn, I definitely had it in mind to try to figure out what the limiting factor on rpm is and see whether we couldn't spin it faster. As far as cooling is concerned, since it is air cooled, would building an external oil cooler make any sense?

I am going to be calling some manufacturer's this morning to see their input.

 

[tempforce]

i've used biodiesel and you can squeeze a little more boost or pressure with it.

shortening the stroke of the engine will allow more rpm. but you will need to lenthen the piston top to piston rod bearing distance, ie custom piston(s). to maintain compression.

cc

 

[EKlem]

I was able to obtain some really good info today on this engine. The rpm is current limited by the valve springs which can be changed to get a few more revs out of the engine. People have gotten it up to 8hp continuous before while still being naturally aspirated. After a more careful look at the numbers, it appears that we only need to be able to sustain 10. 5hp. Is running an oil cooler a reasonable way to cool this engine as well as a couple of heat sinks?

 

[Mhannink]

i know perkins has a little 2 cyl n/a that produces 11 i think water cooled and you can pick the hole thing up yourself maybe weighs a 100lbs

 

[EKlem]

i know perkins has a little 2 cyl n/a that produces 11 i think water cooled and you can pick the hole thing up yourself maybe weighs a 100lbs

Yes, I remember seeing an engine around those specs. We are limited to engines of 310cc displacement. The bigger limitation really is weight. The total weight of the car which is a hybrid so it has 2 traction motors, batteries and a bunch of electronics should only be around 650lbs. There is a slightly larger yanmar and a larger Hatz and a larger Lombardini that all could easily be modified to meet our power specs but they all add 20lbs or so to the car which we really don't want to do. We will go with a gasser if the diesel has to be over 65lbs.

 

[Dieselnut59]

I have an air compressor with the next size larger Yanmar engine (rated for 6. 5 horse), two with the 10. 5 horse Yanmar engines and one with the 9 horse Lombordini. I also have a Robin generator with a 4. 5 horse engine very similar to the Yanmar. It is also Japanese built. All have a "power screw" which you can turn up a bit for some added power immediately, at the expense of having some added smoke. I have turned up a couple of ours to help with getting the compressors going, as they have no clutch. I also raised the rpm's on the smaller Yanmar around 200 or so. Have had NO problems with any of them.

These engines are pressure lubricated so I would imagine it would be fairly simple to come up with an oil cooler. I am not sure if they will interchange, but you could see if you could use the delivery valve and injector off the next larger size engine. I love these small air cooled diesels. Liquid cooled ones are fun too, such as the Fuji 455 cc in my Polaris ATV.

 

[jwgary]

How far do you need to go on one tank of fuel? Can you get the trade off with a heavier engine, but carry less fuel for the same range?

 

[EKlem]

Dieselnut59, I am glad to hear that you have had good luck with them.

jwgary, The distance isn't great, it is something like 15 miles but your fuel allowance is . 9gallons. The weight in fuel is not very great so I don't think that tradeoff would work. If we can't get the yanmar l48ae to work, there is a larger version that would work but it is close to 20lbs heavier which is not ideal.

It looks like we need to spend some serious dyno time with these engines and see what they will do.

 

[Dieselnut59]

Dieselnut59, I am glad to hear that you have had good luck with them.

jwgary, The distance isn't great, it is something like 15 miles but your fuel allowance is . 9gallons. The weight in fuel is not very great so I don't think that tradeoff would work. If we can't get the yanmar l48ae to work, there is a larger version that would work but it is close to 20lbs heavier which is not ideal.

It looks like we need to spend some serious dyno time with these engines and see what they will do.

I have just purchased 3 of the Yanmar L48 engines and one L70 engine. These are the recoil start (no charging system, electrical or starter) and weigh considerably less than the electric start ones. Even our L100 and L70 air compressor engines start easily with the recoil starter. You could free up some weight by removing the starter and charging system components.

 

[tempforce]

have you thought of

have you thought of removing the starter as above. but replacing with a small air starter if it won't start easy with a pull rope. the other idea is to use a air wrench on a nut flanged on the main shaft of the engine. so you would have a remote starter like a formula car.

cc

 

[Dieselnut59]

Never had a bit of a problem starting these engines. They always start on the first pull. I have a little 3300 watt generator with a Robin diesel (similar to the Yanmar) and several small Yanmars. All start easily with the recoil rope.