Lately it’s Diesel Days here at CC. Paul’s put up articles about a gasoline-engine-based diesel that went just fine (VW’s 4-pot), and one that probably shouldn’t have been built but was (GM’s Oldsmobile V8). Now here’s a kind that maybe should’ve been built, but wasn’t: a diesel version of Chrysler’s 225 Slant-Six.
Actually, it’s not just one but three diesel versions of the Slant-Six, none of which was commercialised. Two of them were engineering programs in-house at Chrysler. Bill Weertman—Chrysler’s Engine Design Managing Engineer 1955-’62; Engine Design & Development Assistant Chief Engineer 1962-’76; and Chief Engine Engineer, 1976-’87—says:
“Chrysler Engineering had a major program to develop a diesel version of the Slant-Six engine. The program started in 1975. The first design effort resulted in a design of a diesel cylinder head, manifolding and piston with few changes to the lower end of the 225 engine. The engine was naturally aspirated and utilized an Indirect Injection (IDI) combustion chamber which was in common usage on automotive type diesel engines. A number of engines of this type were built and run. The program was not a high priority and was interrupted at times due to higher priority work.
“In 1980 the program was given a sudden boost in status due to the appearance of a number of competitive diesel powered passenger cars on the market and continued concern about availability of fuel supplies. At this time, the program was changed to add turbocharging and to add a 2.2L 4-cylinder derivative engine (also turbocharged) to power the front-wheel-drive vehicles.
“The extra loading caused by the turbocharging required that the crankshaft and crankcase be redesigned to provide 7 main bearings for the six cylinder engine and 5 main bearings for the 4 cylinder engine. The engine was essentially totally redesigned to give it the best diesel technology available.
“To make the diesel program more viable from a business standpoint, a joint venture was formed with an outside diesel engine company. With both Chrysler’s use of the engines in passenger cars and trucks and the outside company’s sales of the engines, a higher production volume of engines would result with inherently better economic operation of the plant.
“Windsor [Ontario] Engine Plant was designated to be the source of the engines. Prototypes were built and testing was in process on dynamometers and in vehicles when the entire diesel program was cancelled in 1983. The cancellation was based on the sudden drop in demand for passenger car diesel power with the passing of the oil crisis problem that started in 1973 and lasted through about 1982.”
Weertman recalled that he went test-driving with Lee Iacocca in a Dodge pickup truck equipped with the turbo diesel 225. It performed well, but Iacocca decided there wasn’t enough market interest in small diesel engines to justify series production. Too, Iacocca might have been spooked to some degree by the GM debacle. Was cancelling this engine the right decision? We in this timeline will never know for sure. The hot and cold running corporate funding and favour is evident in four Popular Science clips; first from June of 1979:
…then May of 1980:
…then November of 1981 (we learn the identity of the “outside diesel engine company” Weertman mentioned; was there any doubt?):
…and November of 1982:
Weertman says the five or six engines that were being tested at the time of program cancellation were put in storage and later sent to the Chrysler Historical Collection where they still resided as of 2006. But that’s one of the prototypes at the top of this article, and it looks to be in somebody’s private garage; one way or another some of them appear to have escaped the corral. These things happen; six years ago somebody reported encountering a stash of the prototype 225 turbo diesel engines said to have been saved from a scrapyard; perhaps this in the pic is one of those.
And various parts of these engines are floating around, too. I found this exhaust manifold and subsequent-casting-number parts on eBay close to 15 years ago:
When I showed Weertman these photos, he said “I am certain it is the manifold of the turbocharged diesel version of the Slant Six engine; the cross-section [drawing] of the engine displays the exhaust manifold in situ. Just before its abrupt termination in 1983 the program was on a path to go into production, which would account for the manifold having a cast-on part number and pentastar. Since there was a multitude of stockroom parts it is not surprising that a wayward exhaust manifold has appeared on the ‘outside’.”
Here are more bolt-on parts spotted in the wild:
Alright, so that covers, to the best of my ability, Chrysler’s own R&D work on a diesel Slant-Six. But wait, there’s more! A British outfit called Ricardo Consulting Engineers (apparently still a going concern, and a major one at that) published a paper in 1981, “A Passenger Car Diesel Engine For America”, presenting great detail on the development of a diesel version of the 225 Slant-Six. How separate or integral Ricardo’s work was to Chrysler’s is not explicitly specified, but my take is that this was a more or less parallel project: overlapping timeframe, different companies. There’s a lot to be learnt by reading it, such as the power and emissions effects of injection timing, and deliberate exhaust backpressure to improve heater performance. In the end they wound up with a non-turbocharged engine giving almost identical horsepower and torque to the gasoline-fired 225 with single-barrel carburetor, with much better fuel economy and lower emissions. Click the front page here to obtain the whole report (PDF), which contains extensive real-engine test data:
The 225-1v engine was getting wheezier and weaker by the year in the late ’70s, but it still (barely) made 3-digit horsepower, and matching that with a naturally-aspirated diesel—probably with better driveability—was quite a nice achievement that raises questions of what thoughtful, dedicated development of the turbocharged engine might have accomplished.
(there were some diesel-powered Darts and Valiants. They’re outside the scope of this article, though, so we’ll save ’em for another day.)
What might have been…
I’m thinking of a M-body Diplomat with a turbo slant 6 diesel.
I had two Slant-6es, each with the 3-sp column automatic, and had no idea this was ever an experiment. Fascinating stuff.
With Chrysler’s propensity for the occasional grand slam in the face of many strike-outs, if this engine had been completed and been a hit, GM would have been wearing that much more mud on its face, some of which was already due to Chrysler’s relatively successful launch of the K-car compared to GM’s X-car.
Thank you for this look into a program I was vaguely aware of but did not know the details. I hate to be a pessimist, but I have my doubts as to just how well it would have turned out.
I have to assume that Dodge’s poor sales with its 1978 diesel pickups powered by Mitsubishi engines had an impact on Iacocca’s thinking. Dodge sold all of 2835 diesel pickups, and although it was also supposed to be available in the vans, there’s no record of them actually ever having built any:
I love looking at those old “Detroit Listening Post” type articles in hindsight to see all those things that were supposed to start production “soon” that never made it to market. The X-body minivan comes to mind which would have beat Chrysler to the punch and it begs the question of how much influence that not so secret plan had on what Chrysler brought to market.
They may have heard rumors of a GM minivan, but Lee Iaccoca and Hal Sperlich kicked around the small van idea when they were at Ford in the early 70s which reached prototype stage, but management was worried about cannibalizing Country Squire sales and it wasn’t greenlighted. At Chrysler they finally got their chance and they also had the FWD K platform to build it on (the Ford van would have been RWD). I think the Chrysler minivans would have happened anyway without any instigation from GM.
Well they also got a bunch of engineers from International’s Scout Business unit who were working on their own minivan proposal, which was to be a line extension of the Scout III who’s basic front end design showed up on the Chrysler Town and Country.
Here is the GM minivan. https://www.curbsideclassic.com/blog/concept-car/concept-outtake-1979-chevrolet-nomad-ii-gm-shoulda-woulda-coulda-been-the-fwd-minivan-pioneer/
It is also important to note that the Carousel wasn’t really a minivan, it was built on a cut down full size van, basically cut down just enough to be “garageable” and the prototype carried a 460 to give it proper tow capacity.
The first wave of American vans were essentially minivans, being spun off of Falcon, Corvair and Valiant components.
The Econoline was spun off of the Falcon only in name by calling it the Falcon Station Bus. Yes it used the Falcon engine and parts of the manual trans but that is where it stopped. And of course that Falcon 6 also found its way into the Fairlane and Mustang in short order. Things like the instrument cluster and tail lights were from the F-series. I’m sure the Dodge version similarly used no chassis parts from the Valiant. The Corvair Van of course is based on the Corvair’s chassis.
Damn, this is something I had never heard of before. If this had become a reality, that would have made for a very interesting engine swap into my former Aspen wagon. It already had the Super 6 (2bbl 225 Slant 6), swapping into that a turbodiesel Slant 6 would have been fun.
Maybe with a diesel swap the Party Wagon would have passed smog inspection and you would have been able to keep her.
~15 years ago I toyed with the idea of doing a diesel swap on a VW A1 Jetta. I decided that it would be biting off more than I could chew, and I abandoned the idea. But I encountered an interesting point in my research: In a situation like this, you can simply disconnect and tape off the sensors and what-have-you for the gas engine’s emission control system.
I can see why they planned to give it 7 main bearings. I knew of the slant 6’s reputation for toughness, and I was surprised to learn that it had only 4 main bearings.
Four main bearings, yeah…each of which was the same size as that used in Chrysler’s big-block V8. There was no shortage of bearing area, but that didn’t stop dillweeds like Jan Norbye scorning the engine for having only four main bearings.
The Volvo B18 and B20 engines had generous main bearings for their displacement also.
With the increased compression the diesel would have had both main bearing and crank troubles.
Maybe or not—that’s not something that can be stated definitively like that from the comfort of a chair behind a computer, far removed from any calculations or data. The gasoline Slant-6 had a highly over-engineered bottom end: very deep block skirt, massive forged steel crankshaft, giant bearings.
Bottom-end durability is covered at fair length in the Ricardo report.
Interesting. Maybe just as well it didn’t happen, even with a substantial re-design it may not have been a durable engine. And without a turbocharger a 3.7L diesel would not have been very powerful given the technology of the day. By 1985 Dodge was already working on installing the Cummins ‘B’ into the Ram pickup, so the idea didn’t die with the Slant Six diesel project.
Read up on Henry Ricardo and his involvement with diesel engine technology. And yes his firm is still very active and highly regarded:
Or it may have been; we’ll never know. What makes you think not?
This strikes me as a bit of an odd comment given the explicit power and torque figures, equal to the gasoline engine. Anyhow, there weren’t many very powerful passenger car engines on offer in North America at that time.
Number of head bolts for one, assuming that would have been something not changed. I did see Chrysler was intending to go to a 7 main bearing crank, so maybe….. Chrysler was in such dire straits during those years one has to wonder if there would not have been pressure to do a diesel Slant Six ‘on the cheap’.
As for output, those figures were projected, and who knows if they would have been realized. Turbocharging have have made the diesel Slant Six a real contender if the durability was there. Nonetheless you are correct about the output of good many contemporary engines being close to the projected figures of a n/a diesel Slant Six.
The 4.0L Mitsubishi 6DR5 six cylinder diesel as used in the 1978 Dodge pickups made 105 hp and 163 lb.ft of torque.
I think Ricardo’s estimates/goals were a wee bit ambitious for a 3.7L six, especially the torque (171 lb.ft.) The Olds V8 and V6 made less power; the 4.3 L V6 made only 85 hp. But that was in part due to emission standards that kicked in for diesels in 1981 or so. That might well have cut some of the /6’s power estimates too.
The figures on the front page of the Ricardo report are projected, but I don’t think the actual output is a “who knows?” deal; look at p. 5; in section 4.3 they describe and plot performance achieved, not predicted/projected. I think I’m interpreting this correctly, for they discuss running-engine tests done to generate the extensive data plotted in figures 7 through 14 and discussed in sections 5.4, 6, and 7.
There were a couple of other factors that may have tipped the balance against this engine seeing a production line. For one, Chrysler was the one American manufacturer who did not have a big CAFE problem in the early 80s. In the late 70s they had a product mix heavy with sixes and by the early 80s it was heavily fours. While GM and Ford were trying to eke an extra mpg out of their big cars here and there (what were the first cars GM put diesels in?), Chrysler was building CAFE credits that would benefit them for years.
Also, by the time Iacocca got settled he had decided that the big cars had to go, and for reasons having nothing to do with CAFE – he just thought the market was dying and Chrysler wasn’t competitive there anyway. I don’t think he saw a big enough boost from diesel to help that situation, and with the J and R bodies gone, the possible uses for the six cylinder version was down to the M cars. Chrysler’s truck business was at a low ebb too, so there probably was not a good numbers case in Iacocca’s mind.
And from the dates on those press clippings, once Chrysler failed to pull the trigger up front it would have been too late anyhow. The slant six diesel might have been a decent seller in 1980-82 but not after that – the cars they would fit in were disappearing fast and the public stopped caring once fuel costs came down and the economy started to rebound starting around 1983.
BTW, this was a really cool article and something I had only the vaguest understanding about.
Yes, great article!
An equally intriguing contemporary story is that of Ford’s PROCO engine.
I think you’re probably right.
These are real. Early/mid ’80s I saw Slant Six diesels in the flesh, at a closing Chrysler facility. They must’ve been declassified by then? I thought about mentioning it in the other gas-to-diesel entry but figured it might bring the “yah right” response.
What’s not described nor shown here is the pump arrangement. I recall that mostly because I studied it intently, thinking that I might build my own. Haha
Nifty! Can you tell us about the pump arrangement?
The engines I saw, seems like there were about three of them, had aluminum brackets as would be used for typical accessory mounting. A rotary injectionpump was mounted to the bracket. A flat toothed (timing) belt drove the pump via toothed pulleys and the crankshaft.
Yes, Ricardo Consulting does have major credentials in ICE research and design – in fact, going back to 1915. Including leadership in diesel combustion chamber design, starting in the 1930’s, with the early development of diesels for road vehicles in Europe.
The Wikipedia entry for them includes interesting history, on their many and continuing fields of R & D, mostly to do with engines ( I have no connection with them, just an interest in technical stuff ).
CC recently mentioned the absurd statement, by one of the engineers of the ill fated GM passenger car diesels, to the effect that ‘There are no textbooks on how to design a diesel engine’ . Which does seem to imply extraordinary ignorance / insularity / arrogance, considering the experience and knowledge that actually existed. And, in Ricardo’s case, would have been available for hire.
That’s a really good point about GM’s almost comical blindness to anything not done in-house. It’s a far stretch to imagine GM contracting with Ricardo, but if they had, I can imagine one and/or another outcome: a much better result, and/or GM simply yoinking (i.e., stealing) Ricardo’s work—the way (IIRC) they are said by John DeLorean to have done with Holley’s work on a carburetor for the Vega.
I believe GM did consult with Ricardo on the 6.2L diesel combustion chamber.
Would be interesting to find out the figures for the turbodiesel versions of the 225 Slant-Six and 2.2-litre 4-cylinder if the naturally aspirated 225 diesel had a predicted output of 100 hp.
It can be argued the Slant-Six for all its good aspects was a serious drawback when the need for Chrysler to downsize became apparent, when they would have probably been better off replacing it in the late-60s to early-70s with a compact 60-degree V6 (think much earlier 3.3/3.8 V6) that carries over the same architecture as the Slant-Six (as was said to have been the case with the 2.2/2.5-litre 4-cylinder and 3.3/3.8-litre V6).
Is it known if a dieselized version of the LA V8 and V6 was considered akin to what Oldsmobile did with the V8/V6/V5 diesel as well as BL/Rover on the Rover V8-based diesel/turbodiesel Project Iceberg with Perkins?
The 2.2/2.5 and 3.3/3.8 did not have the same architecture as the Slant-Six…just the same (chief) architect.
I don’t see how you figure Chrysler should’ve gone to a V6 in the late ’60s or early ’70s. Why? V6s were still “Well, maybe…we’ll see” novelties in the North American market of that time, while the Slant-6 had an enviable reputation and was performance-competitive, and there were still ~12 years of cars and ~17 years of trucks with engine compartments plenty big enough for their inline motor, the amortised costs of which would’ve meant much better cost-effectiveness/faster return on investment for upgrades to the Slant-Six than for engineering, tooling, and manufacturing a new motor. And considering how almost-not-at-all they upgraded the Slant-Six over its long production life, it’s difficult to imagine them spending the money for an all-new engine not demanded by some hard stop to the Slant-6’s applicability, like a new vehicle that couldn’t take the Slant. The Dakota is what put that push to that shove for Chrysler’s 6-cylinder RWD engines, so they made a cheap and not-very-nice V6 by chopping two cylinders off the 318, which gave further economies by allowing both V6 and V8 engines to easily share production lines. For the FWD vehicles, transverse 4s and 60° V6s were needed, so that’s when and what was devised.
I agree with you it’d be interesting to know what kind of power and torque the 225TD prototypes were producing. We can probably sketch it out with a bit of math: according to Wikipedia, as configured for 1985 models the Benz OM617.912 (2,998 cc, naturally aspirated) produced 87 hp @ 4,000 rpm and 127 lb·ft @ 2,400 rpm (0.029 hp and 0.042 lb·ft per cc) , while the OM617.951 (2,998 cc, turbocharged) produced 123 hp @ 4,350 rpm and 184 lb·ft @ 2,400 rpm (0.041 hp and 0.061 lb·ft per cc).
The Ricardo nonturbo 225 (3,682 cc) is described as producing 100 hp @ 3,600 rpm and 171 lb·ft @ 2,000 rpm; that’s 0.027 hp and 0.046 lb·ft per cc—very similar to the nonturbo Benz engine, so if we plug in the Benz efficacy figures it suggests a turbocharged version might’ve produced something like 151 hp at around 3,900 rpm and 225 lb·ft at around 2,000 rpm
Those strike me as very favourable numbers in context of the 1981 318-2v (130 hp, 235 lb·ft), and the 1985 318-2v (140 hp, 265 lb·ft).
To the best of my knowledge, conversation, and library, there was no attempt at a dieselised LA V8, and the in-house diesel program was long dead by the time the LA V6 came along.
Thanks for clearing things up.
On the subject of Chrysler having an earlier V6, am thinking in terms of how the Cologne V6 (plus Canadian and UK Essex V6s) and Buick V6 (plus GM 90-degree and 60-degree V6) engines allowed both Ford and GM to downsize their cars over time as well as furthering integration with their non-US branches. Whereas the Slant-Six prevented Chrysler from following a similar path.
Compare that with Chrysler. Sure Chrysler UK developed an Avenger-based 60-degree V6 for the 180 project that was theoretically capable of growing to 3-litres (via the 1.8-litre+ Brazilian block Avenger engines), which could have been widely utilized by the rest of Chrysler only to be ditched after much investment on questionable cost-cutting grounds.
An earlier LA V6 followed by a Slant-Six derived (or related) 60-degree V6 could have allowed Chrysler to downsize earlier in the US, been utilized in place of the Hemi-6 in Australia as well as easily fit into the RWD products in Chrysler Europe or at least been used in US built versions and thus help Chrysler integrate their branchs.
Which was not the case when attempts were made to fit the LA V8 into the Sunbeam Tiger and 180-based Chrysler Centura, not to mention an unsuccessful attempt to fit the same engine in a Humber Spectre sometime in the early/mid-1960s (unlike the Humber Super Snipe / Imperial V8 prototype).
Indeed, the numbers for a hypothetical 225TD does sound favorable. Using both the 100 hp diesel and 151 hp turbodiesel figures as a guide, it would appear to roughly translate to the related 2.2-litre 4-cylinder diesel putting out about 59 hp and in turbodiesel form about 98 hp.
Understand regarding the subject of a dieselized LA V8. Recall reading about all-alloy versions of the LA V8, which is what brought the question to mind as far as experimental work was concerned. Also heard the turbocharged LA V8s used in Bristols originate from experimental work done at Chrysler, that makes on wonder if an earlier LA V6 together with turbocharging would have allowed Chrysler to have its own equivalent of the Buick V6 turbo (plus the GM 90-degree V6 turbo).
Returning to the Slant-Six once more, do any figures exists for Chrysler’s other unbuilt Slant-Six related developments such as the 225 Turbo, OHC 225 and more mentioned in the Allpar article? – https://www.allpar.com/slant6.html
Figures, you mean like horsepower and torque for the various experimental Slant-6 variants? I’m sure that information existed decades ago, within Chrysler. I’ve never seen any of it, and I actively looked for three decades!
As to a compact V6 for RWD Chryslers: I’m still not seein’ it. There was very little interest in selling UK or European “Chrysler” products (Simca/Talbot/Rootes, etc) in the North American market, so not much impetus to consolidate as you suggest. Chrysler Australia made their Hemi-6 walk, talk, dance and sing for a car-buying audience that heavily favoured inline-6s, and it’s difficult to imagine how a V6 would’ve been somehow better in that market at that time.
Am more interested in how the experimental Slant-Six and related 4-cylinder petrol derivatives were an improvement over the existing Slant-Six in terms of raw numbers, also curious to know how the related 4-cylinder petrol prototypes compared to the latter 2.2/2.5-litre engine (that seem to recall initially displaced around 2.0/2.3-litres).
Basically am envisioning a scenario where along with the Avenger-based Plymouth Cricket (with 2-litre Brazilian block or Slant-Four engines depending on the market and ideally forming the basis of a direct Sunbeam Alpine successor capable of being equipped with a V6), US bound 6-cylinder versions of the Chrysler 180 (be it Hemi-6, LA V6 – including turbo version**, Avenger-based 60-degree V6 or a Type 180-derived 6-cylinder*) and a further upscaled “D-car” version of the latter with the rigidity required to cope with the LA V8 (specially in Bristol-like LA V8 Turbo form) if not the Ball-Stud Hemi (as a common replacement*** for the US/Aussie A-bodies and Humber Super Snipe / Imperial) find their way to the US.
Also read a SWB 3-door fastback version of the Avenger was developed initially as a possible conventional RWD replacement for the Imp (with a planned entry-level 1100 Avenger unit) that later evolved into the Talbot Sunbeam.
*) – Have also heard the Type 180 engine drew some inspiration from the BMW M10 4-cylinder, which inevitably leads to the possibility of Chrysler Europe having its own potential analogue of the BMW M30 inline-6 as well as other M10/M30-inspired and related derivatives (including a Euro-sized V8 and a flagship V12). – http://www.unixnerd.co.uk/lost_engines.html
**) – Despite the 180/Centura lacking the rigidity to use the LA V8, am envisioning US versions possibly making use of an earlier LA V6 Turbo (basically a V6 version of the LA V8 Turbo powered Bristols) to create a Chrysler version of the 1987 Buick GNX.
***) – The common “D-Car” platform could have also served as a basis to underpin replacements for the A-body Plymouth Barracuda and Chrysler Valiant Charger as well as spun-off an indirect replacement for the Sunbeam Tiger.
Even better if Chrysler via Chrysler Europe were in a position to establish a close relationship with Carrozzeria Fissore to feature a similar exterior styling theme as on the F/M-body based Monteverdi Sierra.
Have not delved into Simca’s FWD products since it is not relevant to the US, however earlier V6s would have laid the groundwork for Chrysler to have a much earlier time in transitioning to the L/K-bodies and probably allow even latter to be produced in Europe as was originally planned instead of the cash-strapped situation where the European Horizon ended up being derived from the aging mechanicals of the FWD 1100/Alpine (before being sold to PSA).
The humber Sceptre LA V8 prototype was ok it just never saw production Chrysler OZ reckoned the body structure of the Centura was too weak for a V8 but a lot of backyard shade tree versions have been produced, that car was very rapid with just a 245 Hemi 6 they would have been lethal with an 8.
Apparently the Humber Sceptre LA V8 prototype suffered from several major drawbacks that precluded it from reaching production, while the Super Snipe/Imperial V8 project was initially considered too quick in 318 form yet being less then impressed by the 150 hp 273 version compared to the existing Super Snipe inline-6, not to mention there by several snaps with regards to installation of the LA V8 engines in even the Super Snipe / Imperial. .- https://www.humber.org.uk/Magazine_pdfs/1981_December_OldMotor_V8Story.PDF
With Rootes / Chrysler’s lack of success in getting the LA V8 to fit into the Tiger and being unable to get away with developing an all-new Tiger, it is surprising nothing was mentioned about using the Rootes Arrow or even the Avenger and 180 as possible starting points for an direct sportscar replacement for the Tiger.
Can only imagine how a LA V8 would have fared in a properly-developed 180/Centura and larger D-Car that was capable of being fitted with a V8 without issue, though quite like the idea of European versions being equipped with a Type 180 based V8 in better circumstances.
Daniel, please note that these numbers from Ricard as to power output are “predicted”; or guesses/estimates.
The 4.0L Mitsubishi 6DR5 six cylinder diesel as used in the 1978 Dodge pickups made 105 hp and 163 lb.ft of torque.
I think Ricardo’s estimates/goals were a wee bit ambitious for a 3.7L six, especially the torque (171 lb.ft.) The Olds V8 and V6 made significantly less power; the 4.3 L V6 made only 85 hp. But that was in part due to emission standards that kicked in for diesels in 1981 or so. That might well have cut some of the /6’s power estimates too.
But close enough, presumably.
Yes, they give predicted figures on the front page, but look at p. 5 of the Ricardo report; in section 4.3 they describe and plot performance achieved, not predicted/projected. I think I’m interpreting this correctly, for they discuss running-engine tests done to generate the extensive data plotted in figures 7 and subsequent and discussed in sections 5.4, 6, and 7.
But for discussion’s sake, let’s say I’m wrong and this is all a simulation exercise: where’s the flaw in my use of Mercedes OM617 efficacy figures (above) for an approximation of this engine’s output? There are giant gaps in my diesel engine technology knowledge, so if there’s something about the Benz engine that invalidates the comparison, I likely don’t know it.
My bad. I never clicked on that. You might add a subtitle to that effect.
I didn’t mean to say it wasn’t possible, just that it would be right at the max for the best engines at the time. Mercedes had a lot of experience by then.
Let me add another thought: equaling the pathetic 100hp output of the gas /6 in 1980 or so with a diesel is a wee bit unfair, inasmuch as if Chrysler had given the /6 a proper fuel injection and a bit of other attention, it could easily have been making 130+ net hp.
It only was down to 100hp (and 90 later) because Chrysler (and Ford/GM) couldn’t be bothered to make any effort to keep up the performance of their sixes as they were the cheapest entry level engines. But the diesel version would have cost quite a bit more; the Olds diesel cost some $750 extra.
So it’s another apples to oranges comparison.
Apart from the short-lived Chevrolet Straight-6 derived Pontiac OHC-6 and the developments the Australian built versions the Ford Straight-6 received (later becoming the Barra), they along with Chrysler’s unbuilt developments of the Slant-6 bring to mind the question (from a UK/European POV) whether the North American market would have been better off had they not basically neglected development of their domestic Straight-6s in light of how they were further strangled by emissions legislation (that even impacted US versions of the Cologne V6 compared to those across the Atlantic)?
Seems a shame none of the Big Three (plus AMC) had any inclination to follow Ford Australia’s evolution of the Straight-6 / Barra in a more Euro-like direction as a means of gradually moving the inline-6 layout upmarket, while shifting the centre of gravity for the entry-level engines down to 4/5-cylinders.
In an alternate reality, where GM didn’t irreparably damage the perception of domestic diesels, the college towns of America would be full (well, relatively speaking) of diesel slant six Aspen and Volare wagons, some in fading biodiesel taxi livery, while Mercedes W123 wagons languished in junkyards and back alleys. In addition, Horizon diesels and much coveted Dodge Rampage and Plymouth Scamp pickups would render the VW diesel pickups also-rans in the Craigslist sweepstakes.
Back in the real world, Daniel, thanks for a fascinating look into something I’d never heard about.
Something else that may have inadvertently killed the diesel Slant Six was what happened at a long term planning meeting Iaccoca held with Chrysler’s senior executives in Florida during 1981. During that meeting, it was decided that Chrysler would abandon all non-FWD products including trucks. The first to fall were the large R body cars, with the M bodies scheduled soon thereafter. The D and B series light trucks were to remain in production with minor trim updates until sales fell to the point they were no longer profitable. That obviously never happened, but given the time frame maybe the diesel Slant Six program was halted as the intended vehicles were to be discontinued.
Hey Dan—thanks for the great article! Fun to learn something new about something that’s old!
Long time Slant Six owner and fan here – but never knew about these – great article!
Great read Daniel. This is a subject i knew little about, so it’s great to read your article. It is very impressive in my eyes that the slant six diesel could potentially make power comparable to the gasoline version.. In fact, if it did make its 100 hp or so and was able to be emission compliant, that compares very well to the 1980-85 version of the 5.7L Oldsmobile diesel, which only made 105 hp in automobile applications. Also in comparison to the Oldsmobile diesel, the Oldsmobile made no where near the power of the gasoline version. The 1978-79 version pumped out 120 hp compared to 160-170 hp for the gasoline version, which was only about 70% of the power. The 1980 version made 105 hp compared to the gasoline’s 350s 160 hp, or about 66 %.
I don’t think basing a diesel engine on gasoline architecture is the best way to build an engine, but in some cases (like VW) it does seem to work out okay. That said, it kind of made sense for Chrysler who was on the brink of disaster to do this, unlike GM who was flush with cash. And unlike GM, it seems that Chrysler put more engineering effort into making a diesel engine out of a gasoline engine. As we all know now, the 350 Olds diesel was highly underdeveloped.
Thanks again for a good read.
The Dodge Dart in Spain (which was the LUXURY car here) also could be found with a diesel engine developed by Chrysler’s partner in Spain, Barreiros. It was a 2 liter good for 65 hp (SAE), so not really powerful and not as good as the ones in this article. They were mostly found in taxicabs.
I once saw one as a child. It was like a tractor engine… Very noisy and smelly
If you can read Spanish, there is a period test (maybe I should translate for this site one of these) here: https://web.archive.org/web/20150924082655/http://www.pruebas.pieldetoro.net/web/pruebas/ver.php?ID=17
Ah, Xavier, you’ve beaten me to the punch! 🙂 I plan to include the Barreiros cars in a future article about diesel-powered A-body Mopars.
Looking at the test results Ricardo achieved with their Volare diesel prototype, I think success would have come down to timing and the program was already too late. By 1981 GM had poisoned the diesel well, and new compacts were starting to achieve fuel economy improvements without diesel smell or diesel sloth. Had the Ricardo program occurred six years earlier and the engine been ready for production as a 1978 model year offering, then it might have been a big success for Chrysler. Sadly, Chrysler’s own program in 1975 would have had nothing remotely resembling the engineering chops of the team that designed the Slant-Six for 1960.
I was with you right up to the last thing you said there. How do you reckon? Weertman was at the top of the team that designed the Slant-Six for 1960…and in charge of the team working on the diesel project.
Between 1956 and 1966, Chrysler introduced pretty much everything lasting and good. In 1975 they were working on Lean Burn, which managed to make GM and Ford’s engineering seem par for the course. The later 2.2 Trans-4 isn’t remembered for being as sound as the Slant-Six. If there’s a metric that indicated a superiority of the mid’70s Volare and Aspen over the 1960 Valiant, I don’t know what it is. People don’t always maintain their passion for their craft.
Even the best, most passionate engineers cannot overcome or override corporate mismanagement.
Thank you for this interesting article. Two thoughts: 1. Perkins already had an excellent reputation in diesel engines-the six-cylinder Perkins diesel engines in Massey-Ferguson tractors of this era (e.g., M-F 1135/2705) had an excellent reputation for power, economy and durability. And they ran really smooth. I wonder what Perkins expected to gain from this partnership, particularly as a slanted engine would not seem to be a good fit for an upright tractor. 2. That exhaust manifold/turbocharger/intake manifold assembly in one of your pictures is extremely compact, and shows one possible advantage of an inline engine with intake and exhaust on the same side (as compared with a cross-flow arrangement). But wouldn’t that side of the engine get awfully hot? And how would you manage that heat?
I had some similar questions about Perkins too. But it was a bit abstract still.
Most/many diesels have their ports on the same side. FWIW, diesel fuel burns at a significantly lower temp than does gas, and diesels run quite a bit cooler. I don’t see any issues at all with having the ports on the same side, especially not with heat.
Ah! That would make sense. The aftermarket turbo on Dad’s 4020 Diesel fit right under the “hood” with no heat issues (at least, to the hood). Some people added an impressive-looking “Engine pyrometer” gauge that monitored exhaust gas temperature so that you did not melt things inside the engine, but that would hold for anything turbocharged.
I knew a guy just outside of Fort Payne, Al and Rome, Ga. Who actually had a 79 Dodge truck with a 225 turbo diesel
I saw the vehicle in 1997 and it ran great and soloing he showed me his fuel book / milage and was getting around 30mpg out of it
The slant six diesel wasn’t even a running proposition in 1979. And certainly not the turbo version. I’ll bet what this guy had was a 1978 Dodge truck with the Mitsubishi diesel that was optional. There might have been a few ’79s built with it too:
My dad, Jose Regueiro, worked for Bill Weertman as Supervisor of diesel combustion development and was hired by Bill in 1981 to get the program back on track (my dad had previously done the same for John Deere on their diesel line-up between ’75-’79). He took the Ricardo comet combustion system and completely redesigned it, changing the shape of the pre-chamber, reversing the position of injector and glow-plug, enlarged and shallowed the piston top “spectacles” to double as valve pockets (which enabled better valve timing events, more overlap, & better exhaust scavenging, while requiring less numerical compression ratio). He also made design changes to the injection pump, repositioned it to reduce line lengths, and increased retraction volume. This gave improved injection performance, with a clean end of injection (no smoke causing fuel dribbling). All of these changes completely transformed the engine, increasing performance and improving cold start-up, while eliminating white smoke at start up and greatly reducing smoke and particulate numbers overall. I remember him driving prototypes home and getting a ride in a pick-up truck with the engine. It was a great engine in the end, but GM had poisoned the well in the US market, and Chrysler canceled the project in ’83.
After dad was forced to retire on a medical disability around ’91, he forged a unique agreement with Chrysler’s patent office, whereby they would fund any inventions of his that they deemed of interest, and he would have 3rd party sales rights. He obtained about 40 engine design patents in this way before he died in 2006. Prior to his death, I think around 2000, he desperately tried to get Chrysler to send him one of the engines from storage, as they were to be scrapped, but they refused. He had designed a 4V/cylinder, central pre-chamber design that was a natural evolution of the work he’d done in ’81. Here is a link to the 4-V design patent:
Here is the link to the design patent on the Chrysler diesel combustion system. You can see how the pre-chamber was redesigned and arranged differently than the Ricardo Comet system (which is shown in the cross-section posted in this article – which was the pre-’81 version of the Chrysler design, provided by Ricardo). Bill Weertman allowed my dad to completely re-design the system. My dad always had the greatest respect and admiration for Bill, and was grateful for the opportunity. The “shelf” at the pre-chamber entrance was eliminated, which reduced HC, particulate and smoke. The injector and glow plug positions were reversed, which promoted faster starting at a lower compression ratio. The piston top “spectacles,” which were a feature of the Ricardo system, were shallowed and expanding to serve a dual purpose as valve pockets. This greatly improved combustion in the main chamber, while allowing for more valve overlap and higher operating speeds (as it also eliminated the high speed recompression spike common with the Ricardo comet system). My recollection, is that the 4 cylinder made a peak 212 or 228 PSI BMEP. They made my dad a plaque with this information when the program ended. If I can find it, I might post a picture. Much of the logic of these changes is spelled out in the patent:
How cool! Thanks for sharing this info, Alejandro!
1978 with Chrysler US electronic lean burn (ELB) added to the Australian Hemi 6 in 245 and 265 ci Chrysler Australia claimed 25% better fuel consumption figures installed in the last Australian Valiants admittingly using leaded fuel (unleaded not available until 1986 Downunder) and no catalytic converter but with US Chrysler resources these issues could’ve been overcome cheaper than converting the slant 225 into a diesel, surely? These engines already had 7 main bearings and a strong lower-end design (Chrysler originally intended this engine family as a truck motor) so this engine family might’ve been a better diesel option. A Hemi6 turbo-diesel would’ve been an amazing engine if the engineering worked out. 245ci at least 115hp nonturbo possibly135-145hp with turbo, but torque would be the optimum outcome and the petrol 245 has 235 lb-ft at 1800 rpm, I’d think that could be maintained or increased with turbocharged option. All wishful and interesting thinking. Image the Aust Hemi6 with crossflow heads (or overhead cam/s) and modern fuel injection, like Ford Australia managed to achieve with the Falcon Six.
Very interesting article
There was no tooling and die in the USA for for the Aussie six.
This article was mistaken. In 1936 Chrysler had a 331 in house truck diesel. Not to be confused with the later 331 Hemi V8.
How is the article mistaken? It didn’t say that it was the first diesel built by Chrysler, did it?
The 331 diesel was first built in 1939, not 1936. Full article here: