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Why no two-stroke diesel cars?
4

Why no two-stroke diesel cars?

Why no two-stroke diesel cars?

(OP)
Hi all.  I joined purely to ask this question:

I've just been reading about two-stroke diesel engines.  How come there aren't any cars or road vehicles with this type of engine?

Also, there are plenty of cars with turbo-diesel engines.  Why aren't there any cars with supercharged diesels?

Cheers

RE: Why no two-stroke diesel cars?

Two stroke diesels generally do not meet emissions standards which is why they're being phased out in favor of four strokes.

Turbocharging is supercharging.  So is closing the exhaust prior to the intake on a two stroke diesel with a pressurized air box.

RE: Why no two-stroke diesel cars?

Detroit Diesels, of course, were two-stroke, supercharged with a Roots blower. But, I don't think any ever made it into light truck use, let alone pass cars.

RE: Why no two-stroke diesel cars?

(OP)
Blacksmith:  So Two-strokes are being phased out on ships, etc?  What makes the them have poor emmissions?

"Turbocharging is supercharging.  So is closing the exhaust prior to the intake on a two stroke diesel with a pressurized air box."

Sorry, I didn't quite understand your reply there.  I know turbocharging is a type of supercharging, but I meant why don't diesel passenger cars use crank driven Roots or Whipple (screw) type blowers?  Surely their ability to provide boost at low rpm would make them perfect for low revving diesel?

Swall: What were the "Detroit diesels" used for?

Thanks for the answers so far.  Keep 'em coming, people!

RE: Why no two-stroke diesel cars?

Ships don't have any emissions requirements.

Mechanically driven superchargers are less efficient than turbo superchargers.

RE: Why no two-stroke diesel cars?

Beg to differ, ships do have emissions standards, International Maritime Organization has imposed standards, and while currently not as strict as other markets, are having an impact.  Also local air districts in many countries are imposing regulations that restrict using heavy fuel (HFO) on the mains within so many miles of port and for the ships service generators.  Emissions regulations are impacting all internal combustions engines, every year more applications and smaller and larger size engines are being affected.

Detroit Diesel was a brand that evolved from General Motors and Gray Marine.  The 71 series two stroke engine was developed in the 30's but didn't see much use until WWII.  Main use was engines for small marine craft, such as landing craft, tenders, harbor work boats, etc.  Towards end of war also saw use as generators and pumps.  It was a very durable and reliable engine for it's power density in it's day.  It was used in marine, power generation, on hiway and off hiway applications.  The original versions were the 6 and 4 cylinder 71 series, 71 cu/in per cylinder displacement.  The 53 series came out in the late 50's, and was in service until the 80's in lots of applications.  The product line evolved into two larger families, the 92 series, primarily used in on-hiway trucking but saw use in marine and power applications and the 149 series.  The 149 series was originally targeted for the oil and gas industries, mainly well servicing, but had a fairly good run for a short time in the standby power market.

As power density, fuel consumption and emissions improved on the four stroke engines, the two stroke just couldn't keep up in most applications.  High pressure direct injection fuel systems and better turbocharging proably the best mechanical contributors.

I thought there were some European light duty vehicles with a combination of small supercharger and small turbo, maybe someone here in the forum has more info.  I rented a Jeep Liberty in Denmark about 4 years ago with a small diesel power plant.  If I could have bought one in the US when I got back I would have.  I only glanced under the hood, but it was a nice package and it looked like it had a belt driven supercharger, maybe not.  But it ran great, used little fuel and was responsive.  I've heard Audi, Saab, Mercedes and Volvo have made great improvements in automotive diesels, too bad we don't get to see them here in the USA.

Mike L.

RE: Why no two-stroke diesel cars?

Turbos are cheaper and lighter and more efficient than belt driven.

As diesels run full throttle, lag is less of an issue.

As diesels tend to inherently have or to be designed for more low speed torque, lag is less of a problem.

Even without lag, the heavy reciprocating and rotating parts in a diesel causes a slower rate of response than a similar powered SI engine.

While diesels might be economical on fuel, they are expensive to manufacture, they are more difficult to get through emissions, they have less performance from low speed acceleration in lower gears relative to their power level, they tend to be noisy and they are heavy. Also in recent times diesel fuel prices have increased more than petrol so the while the MPG or litres per 100 Km is better the higher price has eroded that advantage.
 

Regards
Pat
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RE: Why no two-stroke diesel cars?

The 6-71 was commonly used as an over the road truck engine in the early to mid '70's in the USA.  It was referred to as the 235 (based on HP rating).  The 8V-71 was very commonly found both in trucks and buses until the 8V-92 came out and then no one wanted a 71.  In trucks that was before advent the days of the big bore high HP diesels.  For buses, they continued to be the engine of choice right up to the end of the last century.

Lots of 4-53's were retrofitted into pick up trucks by hobbyists, but it wasn't really widespread.  It made a nice PU truck engine.  If you had one, you could command a good price for it.  They would snap them up.  They were a popular replacement a lot of the early 5.7 and 6.2 GM and Ford 6.9 DI diesels.

Speaking of Detroit's, they blubbered oil terribly and they burned oil voraciously.  An early '90's vintage 8V-92 O&M manual I have states that the rated oil consumption for a 10 hour operating period (about 500 miles travel in an automotive version) is 1 gallon.  I think that was what it burnt, and didn't count what it leaked.  And, believe you me, it was right.  A tank of fuel was a guaranteed gallon of oil added.

Once I heard a trucker in the late '70's say to his buddy on the CB radio "you know, this truck of mine was prophesied about in the Bible."  His buddy - "what do you mean by that?" Reply, "Well, the Bible says that in the latter days there would be crawling and screaming creatures upon the face of the Earth, and it had to be referring to this Jimmy Diesel of mine."  

When Detroit Diesel determined to come out with a new engine in the mid to late '80's, they started with a clean sheet of paper and designed up a 4 stroke, and a good one at that as history tells us.

Based on the above, you probably couldn't give away a 2-stroke diesel to anyone in the heavy duty transportation industry in the USA, either based on their operating record or the current emissions regulations.

rmw

RE: Why no two-stroke diesel cars?

Why did Detroit diesels consume so much oil?

RE: Why no two-stroke diesel cars?

I think the main reason is the piston rings carrying it up past the inlet ports on the liner, and the fact that the blowers seals all seemed to leak no matter what you did.

I rebuilt lots of blowers in my early mechanic days, using stock parts and procedures, the guys building them for race cars modified the seal bores and used different seals, but any of my customers trying to us "race modified" blowers had early hour failures.

By original design these were not a particularly "tight" engine. I think they leaked as much as they burned, and that was on a "good" engine. Rebuilding a high time engine meant getting REALLY dirty, air boxes were always packed with crud.

In their day they were tough, lots lived second and third lives (a lot used to be available on the military surplus market).  They burned lots of fuel and oil and sometimes ran away.

And it seems the old detroits were bad, get around an old Cleveland 268 engine or an older Fairbanks OP, talk about burning and leaking! These were larger bore slower speed 2 stroke engines used in marine, small locomotive and some EPG markets.  But tough old dogs.

RE: Why no two-stroke diesel cars?

I never thought of Detroits as a "bad" engine.  I considered them to be very reliable engines.  In heavy duty diesels, I have only ever owned Detroits and Cummins (4 stroke).  I spent tons more money rebuilding and/or replacing Cummins than I ever did a Detroit.  In fact I never did much to the Detroits other than steam clean them, change injectors occasionally and run the rack occasionally.  CatServ has it right.  You never knew where the oil in the airbox came from, from piston ring slobber or from blower seals, but the drains always blubbered twin puddles of oil when the vehicle stopped.  And when you started it, the accumulated oil would clean out the mosquitos for blocks until it got up to speed.

Someone got the bright idea to pipe the air box drains back into the sump and promptly suffered an engine failure.  There was just too much fine dust that got past the filters in that oil.  Detroit had stern warnings in their O&M manuals against this practice.

But start... if they turned more than a quarter rev and weren't running, they weren't going to start.  You could grind and grind on a Cummins and maybe it would start if you didn't run out of battery.  If you had to grind on a Detroit, you were just abusing starters and batteries.  If one of mine ever turned over more than about 4 times with out starting, I let go of the key and started troubleshooting.

They were very predictable.  The 8V-71 wouldn't produce squat under 1800 rpm.  But once there it would do its job.  The way mine was geared, that meant taking it all the way out to 2100 rpm (I had the governor juiced to ~2200 so I could go there if I needed.)

But that meant that if you were climbing a hill, and rather than falling back to 1800 rpm to get into the next gear, she fell off to where you got back in at 15-1700 rpm, you were going to do no more than make lots of black smoke.  (That is why I had the governor juiced a little, plus it helped on the top end in the tallest gear).

Later experience was with a 8V-92 TA, a turbocharged aftercooled (as well as blown) engine.  It had a MUCH better torque rise characteristic and after the 8V-71 (non turbo engine) it always amazed me when it lugged her down to ~13-1500 RPM and she just kept pulling.  In fact, I had to overcome some habits developed while driving the 8-71 in order to overcome the urge to shift prematurely.  Shifting prematurely would cost you rather than helping you.  That engine, however, really wanted about 5 psi of boost before it wanted you to pour the fuel to it.  If you feathered it enough to get the 5 psi, you could then mash on it all you wanted.  When I trained drivers I termed it "building a fire in her".  When you wanted to pass a vehicle on a 2 lane road, you started adding fuel well before you changed lanes and mashed on it.

The Cummins, well there was this one water hose, about 3 inches long that was prone to failure that cost me a couple of those engines.  The other one was when a driver went into the pump on his own and turned it way up.  I heard stories for years (my truck was rather distinctively striped) about my truck speeding around other trucks on certain famous upgrades.  He burnt it up like that and I didn't find out about it until doing a post mortem on the junk engine for trade in.

rmw

RE: Why no two-stroke diesel cars?

And I guess the point of all that was back to the OP.  Who'd want to drive an automobile if you had to think about all that to drive it?

rmw

RE: Why no two-stroke diesel cars?

In the UK, the Commer TS3 engine was used in 3.5 to 7.5 ton trucks in the 60's. It was a horizontally opposed layout with two pistons per cylinder, a rootes supercharger and was  two-stroke.
http://picsdigger.com/keyword/commer%20ts3/
http://www.youtube.com/watch?v=mfKmkitnqQY

Also check the web for the comprex supercharger. I drove a small-displacement IDI diesel (1.8l, ~108 cu in) fitted with a comprex in about 1985 and, for its time, it was an excellent drive with very good economy. No electronic management involved.
http://en.wikipedia.org/wiki/Pressure_wave_supercharger

Bill

RE: Why no two-stroke diesel cars?

swall (Materials) 17 Sep 10 10:05  
Detroit Diesels, of course, were two-stroke, supercharged with a Roots blower. But, I don't think any ever made it into light truck use, let alone pass cars.  

 Sorry I don't know of any other way to quote on this site.
=======================================
The roots blower is not a supercharger on a standard Detroit 2 stroke diesel engine. It is the pump for induction and scavenge.(agree some amount of supercharge can be done) If they desire to supercharge a detroit 2 stroke a turbocharger was added.
And yes a turbocharger is a supercharger, I think the OP is asking about a mechanical supercharger, the problem with a mechanical supercharger is it takes crankshaft power to run it, where the turbocharger doesn't. Any engine that is purposly designed with a mechanical supercharger always benifits from an added turbocharger, if for nothing else but to nulify the load imposed by the mechanical one.
The 2 stroke detroit diesel is a good example, as are some old reciprocating aircraft engines.
 
 
 

RE: Why no two-stroke diesel cars?

kj16v,

Automotive diesels are now uniformly 4-stroke engines due to emissions, driveability and durability issues.  

The 4-stroke does not require any assisted scavenge device like a 2-stroke does.  

The 4-stroke rings and liners also tend to be more durable, since there are no ports located in the cylinder walls. The stroke overlap between the oil control ring and compression rings is not severely limited in a 4-stroke, like it is in a 2-stroke.

The thermal loads on a 4-stroke piston/ring pack are also much lower.  Since the 4-stroke has half the rate of firing frequency of the 2-stroke.

In theory, a 2-stroke engine should be more efficient than a similar 4-stroke.  But for many practical reasons, this is not usually the case.  The only exception being, as others pointed out, very large displacement low rpm engines operating at a fixed speed.  The current trend seems to favor a 4-stroke at power outputs up to 5000 hp or so.

Hope that helps.
Terry

The trapping/scavenge characteristics of piston ported 2-strokes usually result in a fairly narrow torque curve, unlike a 4-stroke.

RE: Why no two-stroke diesel cars?

Turbo's still require crank power!, the exhaust gas is pushed out of the cylinder by the piston, which is connected top the crank, this is where the pressure comes from. it just doe's it more efficiently.

Diesels work fine in cars, it is the driver that wants to leave every stop sign like a drag race that has to drive a SI engine so they get that fast take off, also why there mileage is so poor.  This is the #1 reason people trade in there hybrids after a few months be cause they miss the G force leavening the standing start.
Just need to reteach your self how to drive economically!
 

SBI
Central Ne.,USA

RE: Why no two-stroke diesel cars?

"This is the #1 reason people trade in there hybrids after a few months be cause they miss the G force leavening the standing start."

Hadn't heard that before, nor experienced it in my 2006 Prius.

Matter of fact it has too much starting torque.. MG2 (the 50KW, 62 horsepower electric motor) produces 295ft-lbs of torque.. Too easy the spin the tires when starting off from a stop, bringing in the traction control..

Toyota agrees.. On the next generation Pruis they reduced the size of MG2.

RE: Why no two-stroke diesel cars?

DanEE's reply mirrors my only experience with a hybrid.  Given a test ride by a friend (Petroleum E) the most impressive thing about his Toyota Camry Hybrid was the tremendous acceleration away from a standing start.  Reminded me of being in a '57 Chevy back in the day.  One of the only features that really interested me.  I guess I spent too much time driving diesels and just missed the G Forces at take off.

rmw

RE: Why no two-stroke diesel cars?

Turbo's still require crank power!, the exhaust gas is pushed out of the cylinder by the piston, which is connected top the crank, this is where the pressure comes from. it just doe's it more efficiently.

Not just more efficiently - on a well designed turbo setup, a lot of the energy recovered in the turbine is "blowdown" energy which is free. Blowdown energy is the leftover energy in the cylinder when the exhaust valve first opens. This can be expanded and utilised before the piston starts the exhaust stroke which is where the negative work occurs.

RE: Why no two-stroke diesel cars?

Hi Pat. I didn't say it was all free, just that a significant portion of it is free energy. During the initial phase of blowdown, the flow through the exhaust valve is choked and the higher pressure in the exhaust manifold due to the turbine does not reduce the flow.

RE: Why no two-stroke diesel cars?

Given the amount of after-treatment methods and devices that are finding their way onto Euro Stage-V diesel engines, plus the associated incremental electronics and software, I wonder whether a blown 2-stroke, with its initial 'poorer' emissions, might be a viable improved power-to-weight ratio opportunity - with all the same/similar after-treatment effort?

Anyone got an idea?

Bill

RE: Why no two-stroke diesel cars?

Nobody seems to have mentioned what is possibly the main problem with 2-stroke valved engines - both diesel and SI.
 The problem being that the camshaft must run at crankshaft speed - not half crankshaft speed as with a 4-stroke. So even at a moderate rpm like 3000/4000 the valve gear is working at racing engine speeds.
 Ideas like having two cams running at half speed and opening valves on alternate strokes similarly run into valve speed problems.  The valve problem is probably the main reason Junkers/Napier etc. went for the opposed-piston/two-crank layout.
 If it were not for the valve speed problem I suspect 2-stroke diesels and SI engines would be a lot more common.       

RE: Why no two-stroke diesel cars?

A trivial example- I have a Cox Sandblaster somewhere in my basement, a 2T diesel car (albeit methanol/nitro fueled with 0.049" displacement).  I recall it has only ever started in the reverse direction for unknown reason.

RE: Why no two-stroke diesel cars?

Quote:
"Beg to differ, ships do have emissions standards, International Maritime Organization has imposed standards"

Yeah, they are going to reduce sulfur from 4.5% max to 3.5% max in 2012.  Inspect emissions once every 5 years.  Once they are international waters I'm sure they are right back to burning bunker oil and jacking up the injection timing.  Toothless laws with no enforcement.

RE: Why no two-stroke diesel cars?

drwebb, I had forgotten about the blasted things running backward as well as they run forward.  I have seen 2 Detroits do that.  I had always heard that they would, but I saw 2 of them do it with my own eyes (and paid for the damage to other driven components not designed to run backwards like AC compressors myself too.)

rmw

RE: Why no two-stroke diesel cars?

Diahatsu markets a two stroke diesel. Claim it gets 100mpg. I am currently fabricating a three cyl. two stroke diesel but air in through the poppet valves, exhaust through the sleeve ports. Theory is more uniform combustion chamber temp. Possibly no need for coolant in the head. Two lobes per valve position slows cam down to half crank speed. I have a fueling strategy that should allow for HCCI operation. We'll see.  ------Phil

RE: Why no two-stroke diesel cars?

''Also check the web for the comprex supercharger. I drove a small-displacement IDI diesel (1.8l, ~108 cu in) fitted with a comprex in about 1985 and, for its time, it was an excellent drive with very good economy. No electronic management involved"

Mazda Capella? A very strange supercharger that is not self explanatory when you have it in your hands.Physically there is no separation between inlet and exhaust....but it does seem to work.It's belt driven off the back of the alternator,and belt tension is critical - black soot on the engine side of the airfilter is a pretty dramatic symptom of a slipping belt.

Most 2 stroke diesels should have a dephaser in the injector pump drive - the TS3 would switch to reverse running if the idle speed was too low.  

RE: Why no two-stroke diesel cars?

Smokey - sounds like an interesting project - however the two-lobes-instead-of-one idea probably doesn't solve the valve speed problem.  The two stroke engine needs an opening duration of about 120 crankshaft degrees - on a half-speed cam this is a cam angle of about 60 degrees. This is a very short duration and it would be difficult to get any useful amount of valve lift over such a short duration.  
  I note that on the Daihatsu power/torque graph the maximum power is at a very low 3500RPM - it looks like the Daihatsu's RPM is limited by valve speed problems.
  http://www.daihatsu.com/brand/motorshow/frankfurt99/s2cd/photo/img/08e.pdf

RE: Why no two-stroke diesel cars?

AVL and Ricardo, among other engine consulting houses, have been developing small 2-stroke compression ignition engines.  FEV can be counted in this company as Ecomotor's founder  Prof. Peter Hofbauer incubated his OPOC engine idea while working there.

A 2-stroke Diesel loses much of its simplicity advantages compared to small gasoline 2-strokes since a valvetrain (opposed piston engines excepted) and wet sump lubrication are usually needed.  In exchange you double the frequency of combustion heat flux (read higher thermal stress) but you don't get double the specific output.

Emissions is not a major problem now owing to ultra high-pressure piezo common rail injecion, copious amounts of EGR and modern aftertreatment.  Ported liner lubrication, oil consumption and attendent emissions is probably still the biggest issue.  This can be solved, as Toyota and Ricardo have done, by eliminating the ported liner and using poppet valves for both intake and exhaust in a 2-stroke design.

RE: Why no two-stroke diesel cars?

Toyota and Ricardo really haven't solved the problem with 2-stroke engines with poppet valves - they are still very RPM-limited - and they still need scavenging blowers.

Credit where credit is due. Evidence would suggest that the Hofbauer/FEV/OPOC engine was inspired (or possibly plagiarised) from the pre-war NSU opposed piston engine.       

RE: Why no two-stroke diesel cars?

2-stroke engines SI or CI, will ALWAYS need forced scavenging by their inherent operation; the loadings of a CI engine is just not amenable to rolling bearings in the bottom end with oil vapour lubrication, whilst crankcase scavenging presents other problems of emissions and pre-ignition in a Diesel engine.  A scavenging blower is not a big deal, especially when forced induction in the form of turbochargers is now ubiquitous in Diesel engines of all sizes.

There is no particular basis in the combustion process that prevents a 2-stroke Diesel from operating as high of an RPM as a 4-stroke Diesel counterpart; however, the truncated expansion from early exhaust port/valve opening is usually not far from the end of all heat-release from combustion...

Toyota and Ricardo abandoned researching 2-stroke CI engines over a decade ago (the much more recent poppet-valved Ricardo 2/4Sight was spark ignited and not the project I'm referring to), just as development was taking off with modern injection systems and combustion development.  Even if 2-stroke Diesels were limited to, say, 3500 RPM, that suits an application like a range-extender just fine.  The problem is that a poppet-valved 2-stroke would have its valvetrain operating like a 4-stroke at 7000 RPM.  Once again, the RPM limitation in this case has nothing to do with the combustion development.

RE: Why no two-stroke diesel cars?

Oddly enough poppet-valve two strokes will run without a scavenging blower of any kind.  Toyota reported that their six-cylinder poppet valve 2-stroke would run without a blower - but they gave no details of how well it ran.

I know from personal experience with a modified 3-cylinder Charade engine (with a crank-speed cam) that 2-stroke operation without a blower is possible.  The engine ran but not very well.  There was a lot of spitting back out of the intakes - I thought motorcycle-style reed valves might help but never tried it.
Without a blower the induction is basically powered by the exhaust rushing out and drawing the new charge in.

One reason I thought "Smokey's" project was interesting was that the exhaust-powered scavenging should be a lot more effective with his suggested uniflow type of layout. His engine may run quite well with reed valves and no blower.


  


 

     

RE: Why no two-stroke diesel cars?

Just think of a 4 stroke diesel as a 2 stroke that uses its piston to do the scavenging. And what's the matter with developing maximum torque at low speed. Avoids costly and compilcated speed reduction transmissions.

RE: Why no two-stroke diesel cars?

The issue with poppet valve 2-strokes is achieving good scavenging efficiency.  With a conventional diesel combustion chamber; 4 inward-opening valves with central vertical injector, it is difficult if not impossible to direct the intake flow to loop down the cylinder on one side, and then back up the other side and out of the exhaust; it has every incentive to short-circuit straight out the exhaust.

To get reasonable scavenge efficiency, you have to go with downdraft ports on the inlet side (which is what Ricardo did for their "Flagship" SI poppet-valve 2-stroke), but this is formidable to package around the injector.

You can argue that today when all engines use EGR (and usually lots of it) that good scavenging is not so important, but hot residuals are only ~50% as effective as cooled EGR at NOx mitigation, so you really want cooled EGR even in a 2-stroke where the combustion temperatures are lower (than in a 4-stroke) anyway.  Plus, you still need to get the fresh air for the next cycle in on top of the residuals, and there is not much time between EVC and IVC.

So, with a 2-stroke diesel, you need to have directed intake flow for good scavenging efficiency, but you will still likely need well-controlled swirl to get good combustion efficiency.  Achieving both requirements is not easy with a conventional chamber.

PJGD

RE: Why no two-stroke diesel cars?

For what it's worth the valve lift is .190 intake/scavange is 80 deg. crank rotation. (40 deg. cam) With 4 valves should be sufficient valve curtain to provide at least 75% fresh air charge. I've modified a couple of 4 stroke diesels to run on HCCI combustion process. I've been able to get the same power levels without the need for a turbo and nox is a lot lower. Very noisy though. Fuel economy is the best I've ever seen. Hopefully this two stroke will eclipse that.------Phil

RE: Why no two-stroke diesel cars?

@SMOKEY44211: Any videos or publications of your work you can share?

RE: Why no two-stroke diesel cars?

Smokey - I too would like to see videos and more details etc.

Does "without the need for a turbo" mean that your engine will run without any scavenging blower?

Have you tried (or considered) an SI version of your engine?

All 2-strokes are loud.  I found that a test 200cc Yamaha twin with no mufflers was actually far louder than a 4-litre 6 without mufflers.   

RE: Why no two-stroke diesel cars?

Smokey - very nice drawings.  Are you building this from scratch or adapting an existing engine?
I notice that your cam lobes are not "double-ended" - are they still half-speed?
 That is a lot more than 40 cam degrees on those lobes - and a lot more than .190 lift.
  How did you decide on 80 crankshaft degrees for your cam?
 Are you intending to use a scavenge blower?
Sorry about all the questions.

RE: Why no two-stroke diesel cars?

Hello Yes for the most part its a custom assembly. Block, head, crank, rods, pistons, ect. are being fabricated. However they are sized to use off the shelf components such as bearings, rings, valves, springs and so on. the drawing is incorrect as it relates to the camshafts. I'll post the updated version after the changes. The 80 deg. figure is not set in stone. The exhaust/ scavange event is 90 deg. as determined by the height of the sleeve porting. Most engines open the exhaust around 135 deg. ATDC so I used that as a good jumping off point. I am using a traditional rootes type blower for scavenging and possibly for some additional boost. I'm after fuel economy but testing will determine what the final configeration will be. Not much data base to draw from. Near as I can tell no one has attempted doing it this way. I think the idea has merrit so I'm putting my money where my mouth is. I'll post additional info as the project moves along.----Phil

RE: Why no two-stroke diesel cars?

Rotec convert 4 stroke diesels to 2 stroke using a piston scavenge pump timed to the engine. I think each piston serves two engine cylinders. The object is emissions reduction.   http://www.rotecdiesel.com/go.cfm?do=Page.View&pid=5
 

Engineering is the art of creating things you need, from things you can get.

RE: Why no two-stroke diesel cars?

Smokey - I too have never heard of a 2-stroke diesel with the intake through the valves and piston port exhaust. This is a bit surprising as "uniflow" steam engines have this layout.
  Your engine may be worth putting in a provisional patent application - which is quite cheap if you do it yourself.
 Personally I would mention in the application the possibility of operation without a scavenge blower and using much later intake valve closing in conjunction with a reed valve in each intake port.  

RE: Why no two-stroke diesel cars?

After 80 years of development of the 2 stroke uniflow engine I think it will be hard to come up with something no one has thought of already. The use of a separate piston for a scavenging air pump was used on the earliest direct reversing 2 strokes built by Fairbanks Morse back in the '30's. There is a good reason why everybody went to positive displacement blowers as they are more efficient high volume air pumps.  

RE: Why no two-stroke diesel cars?

With the 2-stroke diesel with intake ports and exhaust valves, it's easy to arrange for swirl of the intake charge (necessary for normal diesel air/fuel mixing and combustion processes). With intake valves and exhaust ports, not so much. Not impossible, just harder.

Some lube oil is inevitably going to get past the ports. It's an inherent situation with all piston ported 2-stroke engines. With intake ports and exhaust valves, that excess oil goes into the cylinder where it has at least a hope of being involved in the combustion process. With intake valves and exhaust ports, that excess oil is going straight out the exhaust (think about HC emissions).

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