Is anyone out there converting a petrol engine to diesel?

[Blunt Eversmoke]

Hey, Blunt.
Well I wasnt really suggesting that the needle or vaporizer should vibrate at such speeds, but it doesn't seem a bad idea. No I meant to create a fine mist in say some sort of enclosure bij means of an ultrasonic vaporizer. Next suck the mist in with the intake air. These vaporators can be found in for example those small table top decorative mini ponds or fountains in wich they create a mist.
To get back to you on the Brons motor: It maybe didn't have a low pressure dosing pump in the first few examples. But the one we own (2 cilinder) certainly has! Maybe that is because it was a ship's engine. I am curious though, since you seem to know a lot about this engine, how did they regulate the amount of diesel being sucked up by the intake stroke?

Oh, that's easy enough, and there is very little of knowledge involved, on my side at least. This much you know: In addition to the intake/exhaust valves, there is a second intake valve in the cylinder head - the fuel intake valve, that connects either the fuel pump (as in the case of your engine) or the fuel dosator (as on most of the smaller Hvids) with the spraycup. The dosator is akin to a needle carb - it regulates the exact amount of fuel sucked into the chamber with a nozzle and a tapered needle on a lever that is moved in or out of said nozzle, thereby varying the effective nozzle cross-sectional area and thus the flow. The difference is, air is not being sucked into the spraycup, of course - but that is not needed, since there is also the four-stroke-standard intake valve outside the spraycup, in the head. See this http://www.eldensengines.com/homebrewhv ... whvid.html great page for details. Also fun reading

The vaporizer idea is interesting. I found one on ebay with data: 60 watts, 360 ccm/h with water (less with diesel?), produced particle size 0.1 to 30 micron(mycrometer). OK, so one would have to size the vaporizer accordingly to HP, and this would mean around 40 watts per HP - not really that great a loss at 1/15, and bigger vaporizers might process even more liquid for less power. Also, pre-heating our fuel with exhaust heat should help reduce surface tension.
But look how fine the water mist is! If one managed to get diesel mist as fine as 1 micron with that, it would be 9 times finer than what commonrail injection manages, and could be easily spark ignited(if that is even needed at all!) at petrol compression ratios, with much less ignition delay. And if 0.1 micron were doable with a vaporizer for diesel fuel, oh boy! Now, with a CR of around 12:1 it should certainly ignite by itself, and still allow RPM way higher than diesel standard with diesel-like efficiency - as seen on the diesel Norton. Add a throttle, or better yet, variable CR/charge cooling/water injection to delay ignition at lower RPM - and off it goes...

[espe]

Sounds like something worthy of an experiment eh blunt??

[Blunt Eversmoke]

Hi all.

Something along more conservative lines of thinking:

Take a petrol engine with a diesel-proof bottom end (or downsize bore until pressure x piston area = force is low enough). This has been done in the case of the 10:1 CR "diesel" Norton, with good results. Now, starting with a bike engine, this would lead to pretty anemic results. Question: What if one were to use a high-performance(twin?) turbo arrangement to blow an originally 9:1 petrol engine to effective 18:1, starting on petrol with spark plugs and switching over to diesel injection once the 2:1 charging pressure has been reached? Underexpanding the gas in the cylinder proper would mean the turbo should be getting high-pressure exhaust gas, spinning at high RPM and providing enough pressure for the engine to "diesel" even at idle, once the turbo is spun up at start-up. Would take up lots of space in the cylinder head, so probably better to go two-stroke so there are no pesky valves in the head.

Thoughts, anyone?

[Stuart]

Interesting if the two stroke diesel can be made to be frugal like a 4 stroke version.

[gilburton]

I'm waiting for some talented model engineer to build a large variable compression engine to see if that works?? Or possibly make a variable compression bike engine?? possibly with a combination of a glow plug for starting.
I still think there may be some merit in adapting the Bernard Hooper engine design to diesel. I did email them once to ask them if a diesel version had ever been considered but never received a reply.
I'm not an engineer so I've no doubt the real engineers out there will tell me it can't be done but I've always been struck by the relative simplicity and light weight of model engines.

[sbrumby]

If you go onto the industrial engine tab on Bernard Hooper you will see a diesel version. I did email them and they did reply , I think they get funded by the military so at present there is no mileage in development for motorbike purposes. But I am convinced this would be the ideal engine, The top hat piston engine is powerful lightweight naturally blown, without the need for add ons turbos, superchargers etc.

[gilburton]

If you go onto the industrial engine tab on Bernard Hooper you will see a diesel version. I did email them and they did reply , I think they get funded by the military so at present there is no mileage in development for motorbike purposes. But I am convinced this would be the ideal engine, The top hat piston engine is powerful lightweight naturally blown, without the need for add ons turbos, superchargers etc.

And it's a "clean" 2 stroke. All we need is someone with investment money to take an interest.

[gearhead1951]

Supposedly there is someone up in scandinavia has converted an HD twin cam from a 1340 cc gas to a 950 cc diesel

[zarquon]

Supposedly there is someone up in scandinavia has converted an HD twin cam from a 1340 cc gas to a 950 cc diesel

We are now concerned with dieselmotorcycles for more than 12 years. We heard several stories about conversions like this, but have seen no one. There were enough opportunities, but nobody has noticed.
So, for me this conversions are myths and fairy tales until I see one of them running.

[zarquon]

If you go onto the industrial engine tab on Bernard Hooper you will see a diesel version.

It's amazing how many different engines they must have build. There are many photos on the website. Photos! No renderings!
Is this the same Bernard Hooper that was an engineer at Norton-Villiers?

[gilburton]

It is indeed. I think it's an engine waiting for an application rather than the other way round.
If diesel bikes ever took off then this design might be worth a look. I could see a Guzzi type bike with a V twin or V four.
No valve gear,light weight good proportions and no oil in the combustion process.

[Blunt Eversmoke]

V4 guzzi style installations look and sound wicked cool, especially on choppers. See and hear

http://www.youtube.com/watch?v=FOXqUukxiWA

and

[Blunt Eversmoke]

Interesting if the two stroke diesel can be made to be frugal like a 4 stroke version.

As frugal as a four-stroke? Probably hard to do, especially since you'd be throwing away high-pressure exhaust gas - now if someone tried to shoehorn a turbo-compound into a bike

You've given me the idea of doing it the other way around, starting with a proper diesel engine (because all modern bike-able diesels are four-strokes). That way, you start with an engine that already has robust bearings and conrods and injection pump (and, possibly, glowplugs) and sh*t and only has to get geometrical CR lowered and an appropriate boost figure to get effective CR back or somewhat higher.

It is known and common logic for ages with regard to petrol engines: You blow it - you lower the CR by making combustion chamber bigger, or it's gonna blow. Also, bigger combustion chamber means even more air and fuel. Indeed, Diesel Power Mag as well as various other sources suggest it is already standard practice to do so when REALLY blowing the livin' shiat out of big displacement diesel engines, for sled pulling and such, after-market low compression pistons lowering the geometrical CR from 16-18:1 stock to 10-12:1. Why no stock producer has done it to diesels for a whole century, I cannot understand.




How to do it:

Take any light enough diesel engine with half of your desired power output, drastically lower its compression ratio(thicker head gasket or somesuch), fit a fat two-stage turbo or supercharger to gHowet the effective CR back to what it used to be or above, add a starting aid and you are good to go - with a super-charger starting aid should not even be required.


This patent suggests you can go as low as stock Otto (7:1 or 8:1) without compromising thermal efficiency - as long as you can compensate for the heat loss by appopriate charging and, possibly, air or fuel heating. They also calculate that heating the (compressed) air charge directly by a small diesel blow torch only takes 3.5% of total fuel usage and only 1% power.

Another piece of info from above link with reference to this project: 3,7 bar of blowing pressure combined with heat of 123°C are supposed to be enough for stable Diesel operation. In the linked PDF, however, they state Turbo pressures of 8:1 and 6:1; their turbos have their own combustion chamber for cold starting (hyperbar method).


All the measures below only apply to a pure turbo configuration and are of less necessity if you just use a small, heavily overdriven supercharger as the starting aid and for idling - the electric clutches used on car air condition compressors would make it possible to turn off the supercharger once the turbo is spun up to boost. Or make the charger bigger so you don't need to overdrive it, and you can do away with the turbo - however, you'll be wasting perfectly good high-pressure exhaust gas then. The harder way is going turbo only - read what has already been proposed and tried:


Mazda are making this stock already with their skyactiv-d diesel engines - they have geometric compression ratios of only 14:1, the rest of the compression - and heat - coming from the turbo. They also have a load of other gadgets to cope with cold start and to ensure combustion uniformity when warm, but it probably can all be done in a variety of other ways.

Starting cold:
Has been achieved on the Diesel Norton by Freeman Sanders, forechamber or swirl-chamber, seemingly, compressing only 11.8:1, by injecting some ether into the fuel lines when cold.
On the Yanmar single-stage direct injecting wankel diesel compressing only as low as 10:1, cold starting was coped with by pre-heating the intake manifold by the means of a small spark-lit diesel torch; 10:1 athmospheric seems too low at least for a Wankel diesel, producing white smoke during idle even when warm, and they had to electro-crank it for one or two minutes before it would finally go off.
Some diesel trucks are known to use electric heater grids in the intake manifold - I think that the battery size and weight necessary for that would prove prohibitive on a bike.
Mazda utilize ceramic glow plugs because they allow higher glow temperatures, but also some adjustible fuel spray pattern which would be hard to reproduce with a garage tinkerer's tools and means.


Combustion uniformity:
Where possible, use catalytic glow-plugs, or, if feeling fancy, directly ceramic plugs, produced by both NGK and Bosch.
One could also, idle-to-midrange revs, re-introduce some exhaust gas from the exhaust manifold into the intercooler pipe, instead of "regurgitating" it through the exhaust valve as with the Mazda.
Another possibility would include, as seen on older International Harvester tractors compressing only 16:1, an intake manifold that shares one wall with the exhaust pipe, functioning as a heat exchanger. Only for idling and low revs, because the turbo won't cope with the higher back pressure.
Then, for idling and low revs, there is also this: Once the engine is warm, injected fuel will ignite even at low compression due to free radicals still present in the micro-chambers from the previous power stroke - probably possible to use in a four-stroker as well. Probably the easiest way - if they finally start selling their pistons...
Finally, there is the possibility of pre-heating the diesel fuel via some sort of temperature exchange with the exhaust after or before turbo.

[gearhead1951]

Just a thought , two single cylinder diesel top ends ( separatly removable cylinders) matched to a BMW or Russian boxer engine to make a boxer diesel ??

Any one wanna comment on this ?

[Stuart]

Just a thought , two single cylinder diesel top ends ( separatly removable cylinders) matched to a BMW or Russian boxer engine to make a boxer diesel ??

Any one wanna comment on this ?

Well that would be something eh? Flat engines being more free revving perhaps it would lessen still more the need for the heavy flywheel?

[Blunt Eversmoke]

Just a thought , two single cylinder diesel top ends ( separatly removable cylinders) matched to a BMW or Russian boxer engine to make a boxer diesel ??

Any one wanna comment on this ?

Sound good. In a true boxer the crankshaft bearings and the crankcase only have to bear the odd difference of forces in the two opposite cylinders, not the full force (that's why us Russians like the bikes so much, because we could make them bearings and crankcases so cheap and crappy without them breaking. On Monday bikes this has been overdone, so that they sometimes still break, even in a boxer ).

Start with a 750cc engine. Make a heavily reinforced longer-stroke crankshaft, ask someone knowledgeable what maximal stroke you can get out of such an engine (more stroke=less bore needed=less stress on bearings and crankshaft), and order/produce accordingly. Get the nicest, fattest roller bearings you can squeeze into the crankcase...

In theory. In reality, it is somewhat cramped in there, so your engine conversion will be very limited with regards to bore. Prepare to go down from 750cc to 500, 600 at best, even with a longer stroke. As a compensation for displacement lost, give your creation a lower CR than your donor diesel engine, install a high-pressure supercharger and blow it but good.

Still, I have read on Russian forums that whoever plans to size up or go for higher CR (both operations necessitating heavier cranks and bearings, as does your idea) always run into space problems - the boxer crankcases are not exactly roomy. Some even go so far as to say that a whole new crankcase has to be cast or machined for such upgrades, so be prepared to stumble a lot on your way to perfection.

Indeed, it seems to me as if the best(least risky and costly) way were actually to pick a side-valve boxer, reinforced crank, stroke up, bore down, big supercharger to help build up compression and heat for diesel ignition. The beauty of a side-valve in such an application is that the cylinder head is as primitive as in a two-stroke, has plenty of space and can therefore be easily modified or manufactured to suit your idea whatever that be - DI, forechamber, glow plugs, one or two injectors per head? Just pick a proper sized steel plate and cut, bore, thread.

[gearhead1951]

BMW R75 has a stroke of 78 mm . I found a 10 hp air cooled single cylinder deisel wth a stroke of 72 mm !

what more do you need !?

[Blunt Eversmoke]

BMW R75 has a stroke of 78 mm . I found a 10 hp air cooled single cylinder deisel wth a stroke of 72 mm !

what more do you need !?

Ough. Sould have looked it up. (What's the bore of both, by the way?) If similar, that's a problem, since we don't know if the low-end is over-engineered to any degree, let alone to take diesel pressure(most say it ain't by any stretch). You can probably beef up the crank and the outer bearings, but the bearing between the two crank throws could prove hard to do.
Beefing up the crank: People who up the displacement often cut up VW T2 cranks; some also suggest taking a look at Subaru's.

[gearhead1951]

BMW bikes boxer engines do not (as far as I know)have a center main bearing !

If you want to try VW boxers , consider cutting one in half and using the front part (definantly no center bearing on THAT boxer twin) !

Do that to a subaru and you might be able to build a water cooled diesel !

[gearhead1951]

www.hummelengines.com/ is a good place to start !!

[Blunt Eversmoke]

BMW bikes boxer engines do not (as far as I know)have a center main bearing !

Well, at least the Russian boxers do, and that may be better for a conversion to diesel. Here, it would be nice to know: How many diesel twins are there with and how many without center main bearing, and how thick is the crank on those without?

Also, speaking of VW, boxers and diesels: Here, bhtooefr points out that

Ooh, thanks for the link.

(I was expecting the article from the March 1982 issue of VW & Porsche Magazine. This one's new to me.)

Interestingly, as mentioned in that article, and better explained in the VW & Porsche article, the crankcase in the engine photographed is actually production - the engine shown is a replica made in 1981, using a 3-piece crankcase from a 1.3L Porsche 356. (The crankcase in question was designed for the diesel, and Porsche decided to use it as-is in the later 1.3L gas engine, used from 1955 to 1958. So, that particular engine was actually a gasserized diesel. (And, that story happened again - VAG designed the EA827 engine family, as used in the Golf and Passat families until the A4 and B5.5 platforms, to be a diesel from the start. They did have to strengthen the block, though, after the fact, when they found out that it wasn't strong enough to actually work as a diesel.))

Crankcase DESIGNED for diesel from the start on. 25 HP at 3000 rpm from 1.3 litre seems a bit lame, but then again, turbocharging is the way of the walk with diesels, anyway. The rest is in the article: Prechamber heads, CR 22:1.
Happy huntin' or what?..

[pietenpol2002]

Stuart commented:

interesting if the two stroke diesel can be made to be frugal like a 4 stroke version

I rather like this idea for a 2 stroke in the link below. And even though the additional "crankshafts" would increase weight, the trade-off is the increased effective displacement. Interesting also how one of the secondary pistons assists in evacuating the cylinder of burned gasses and thus avoids the need for a supercharger to scavenge. And while you're at it, take look at the "History" tab for a review of the various valve options developed over the decades - just a fun review.

http://www.new4stroke.com/

[Blunt Eversmoke]

Stuart commented:

interesting if the two stroke diesel can be made to be frugal like a 4 stroke version

I rather like this idea for a 2 stroke in the link below. And even though the additional "crankshafts" would increase weight, the trade-off is the increased effective displacement. Interesting also how one of the secondary pistons assists in evacuating the cylinder of burned gasses and thus avoids the need for a supercharger to scavenge. And while you're at it, take look at the "History" tab for a review of the various valve options developed over the decades - just a fun review.

http://www.new4stroke.com/

Huh? NOT a two-stroke.

This is a four-stroke gasser, just like the .oz invented Beare Head - only this one uses one two additional pistons - one piston for each valve, while the BearHead uses only one additional piston, but uses additional measures such as a reed valve or a ported disk (don't remember whether on exhaust or intake side) to create "valve" asymmetry necessary for four-stroke operation.
Both designs claim less knock sensitivity for two reasons:
First, because the oil-cooled pistons used as valves not only offer more heat dissipation themselves, but as the exhaust ports are covered up by the pistons during compression and work strokes, the hot area around them is also covered up. Less hot area, less knock. For the Beare Head, 14:1 CR is claimed to be easily achievable on standard gasoline - dunno what they have for standard in Australia, 92 or 95 octane?
Second, greater cross-sectional area of the ports compared to valves meas better gas exchange ratio, so more power and also less knock.
Again less actual for diesels, but with a gasser, once you have calculated and properly configured the port opening times, you can REALLY spin up such an engine. Why, the ports don't just open when they have to, they also CLOSE without delay - same as Ducati's desmodromic valvetrain, only tens of times cheaper. The Polish inventor claimes high RPMs for his otherwise quite peaceful donor engine, while the Aussie starts with a Ducati right away.

Other advantages compared to a traditional valvetrain are comparative ease of repair and replacement - no valve seatings, no valve play to hassle with, no complicated hydraulics - and probably lesser cost; also, whereas a standard cam-shaft valvetrain is parasitic in nature, this one is not, and the BeareHead actually helps expand hot gas as the valve piston goes, umm, "up".

[pietenpol2002]

Huh? NOT a two-stroke.

Perhaps my clue might have been the title of the website "new4stroke" instead of just glancing at the GIF. And now my blunder stands for eternity on the world wide web.

[BertTrack]

I'd rather like Koenigsegg to have their future valve control/powersystem be the standard.

http://www.youtube.com/watch?v=Bch5B23_pu0

Finally getting rid of camshafts.

[Blunt Eversmoke]

I'd rather like Koenigsegg to have their future valve control/powersystem be the standard.

http://www.youtube.com/watch?v=Bch5B23_pu0

Finally getting rid of camshafts.

Ah, the pneumatic-actuated valvetrain. Nice, especially since it is lighter than the Polish engine or the Beare Head. But still the valves are there, with the associated problems of overheating and valve seating. And is it really that much cheaper than a camshaft-driven valvetrain? Because both piston valve designs surely are, even if they are probably bit heavier.

[Blunt Eversmoke]

Just a thought , two single cylinder diesel top ends ( separatly removable cylinders) matched to a BMW or Russian boxer engine to make a boxer diesel ??

Any one wanna comment on this ?

Meanwhile, on the other side of the Wall...

MT-10 diesel conversion!

[Tamber]

Whilst this thread has resurfaced, and is reminding me; my dad -- an old HGV mechanic -- mentioned something a while back about Bedfords running with a chevy straight six; where they changed the heads slightly (apparently to change the compression ratio), replaced the distributor with a DPA pump, and pretty much just put the injectors where the spark plugs were on the petrol version of the engine.

Now, I'm taking this with a pinch of salt, because his memory's not what it used to be, and my brain's telling me the mains would be pounded into dust; but I'll admit I have no experience with those engines, so who knows, they might just be beefy enough to have been up to it. (Or he could be thinking of something else, which I suspect is more likely. )

...not that this pertains to bikes in any way, of course, unless you're after a really big bike. (Eeh, now there's an idea! )

[pietenpol2002]

the mains would be pounded into dust

The 3rd generation Chevy in-line six (3.2-4.8L) was a 7 main engine. Still a bit of a stretch to think that components could hold up under the strain.

[coachgeo]

Just a thought , two single cylinder diesel top ends ( separatly removable cylinders) matched to a BMW or Russian boxer engine to make a boxer diesel ??

Any one wanna comment on this ?

Meanwhile, on the other side of the Wall...

MT-10 diesel conversion!

What is an MT-10?