Some of the worse designed engines? 2

[enginesrus]

Just a fun thread. Lets talk about some of the worse designed engines not going back past the 40's, and all types, sizes and applications.
Why do they get the vote as one of the worse designed. I decided to do this not so much as to talk bad about a particular manufacture, but to hopefully help them and others improve the design.
In many cases such manufactures have other engines that are just fine or have improved what was a not so good design. Maybe we can do this without mentioning any particular brand if that is frowned on in here.
If this is not so good an idea, then the moderators can just delete this.

 

[GregLocock]

Inept DOHC heads on V8s. Makes the engine too wide for any normal bodyshell.

Diesel conversions of SI engines. BL were obsessed with this in the 80s, we tried diesel conversions of almost every engine. Finally they went to Perkins and got the job done properly. A simple substitution of a new head and longer con rod is not enough.

90 degree V6s. Horrible balance issues.

The iron duke.

Throttle body injectors.

The LandRover diesel and SI engines with a common block. I cut my teeth on them, rebuilding the ones that failed on the dyno. Incredibly inefficient.




Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[enginesrus]

The little 3 cylinder throttle body injected Geo Metro engines are great, TB gives some good atomization, better than direct injection in most cases. And yes DOHC over used.
Many newer designed small riding lawn mower engines have many design faults, causing such failures, like leaking head gaskets, broken compression release systems attached to the cam shaft, balancing system problems, valve guides that won't stay retained, at least the seats seem to stay in, use of PM for gears.
Engines with open decks in boosted applications not a good mix. And back to those DOHC engines with the snaking timing chains and plastic guides that crack and fail.

 

[TugboatEng]

Is balance really an issue? Unbalanced engines are all the rage in motorcycles right now with 70 degree offset parallel twins, triples, and cross-plane inline-4 engines. It's amazing what you can get away with when you have a counterbalance shaft. Heck, Detroit Diesel have been running that way for nearly a century with their cross-plane 2-strokes.

 

[CWB1]

90 degree V6s, Iron Dukes, and many TBI engines are famous for durability and low maintenance stateside while giving decent performance.

JMO but I would suggest any engine needing timing belts or other major recurring work, and certainly much more than LOF at <100k in the last 30 years.

 

[SwinnyGG]

The little 3 cylinder throttle body injected Geo Metro engines are great

That's an open deck block though. Clearly the engineers got it all wrong.

 

[EHudson]

As I understand it, the unbalanced firing in racing motorcycles is done to help the rider feel when the rear tire is slipping during the power pulses and give a brief interval for the tire to regain a bit of traction before the next series of power pulses. This is in contrast to some F1 engines that had some slightly out of synch (a few degrees)engine firing to reduce the contribution of each cylinder's (recip components and gas forces) to torsional vibration with a bit of phase difference.

 

[BrianPetersen]

The Ducati V4 is certainly not among the "worse designed" engines ... it's an excellent design. The 90-degree V4 layout with the crank-pins offset 70 degrees leads to an irregular firing pattern in which all cylinders fire over 380 degrees of crank rotation and then there's 340 degrees of nothing. This is an evolution from the "big bang" (simultaneous-firing) Grand Prix engines followed by the "long bang" (closely spaced adjacent-firing) engines followed by the "irregular firing pattern" engines. A 90-degree V-twin with the correct counterweights on the crankshaft is well balanced ... two of them sitting next to each other with their crank-pins 70 degrees apart remains so, and no balance shaft is needed. It is also a reverse-rotation engine, which has a beneficial gyroscopic effect, and the reaction-force to the inertia to accelerate the engine (crankshaft) tries to pull the front wheel down, as opposed to exacerbate a wheelie.

Ducati have also figured something out with the efficiency of that engine. The Ducati MotoGP bike is visibly faster than the others (any of them), especially last year, although it looks like Yamaha have caught up a fair bit this year.

 

[TugboatEng]

I mentioned the Detroit Diesel design because they opted for an even firing interval which, with the 2-stroke cycle in an inline configuration means the crank cannot be balanced. There is a fore and aft rocking couple which is countered by balance weights on the cam and counterbalance shaft. They are some of the smoothest running engines I have been around.

In other words, I think it's silly when people brag about the perfect balance of their inline-6 engine.

To answer the question about worst engine? That's the Caterpillar C9. It seems like we were spending $3k per year in parts for unplanned maintenance when we operated those. Plus I think they stole my idea to fix the raw water pump shaft failures. Then again, I "re-applied" the idea from my previous employer. For comparison, our John Deere 6081 engines each (8 of them) totalled less than $3k in parts over their entire 15 year life.

 

[dgallup]

The Oldsmobile Diesel certainly has to be in the running as one of the worst gasoline to diesel conversions ever. It single-handedly set back diesel automobile sales in the US for decades. The plant I've worked in for nearly 40 years was built to make the injectors for that engine. Fortunately, the contract had big penalty clauses if GM did not buy sufficient volume which kept the place open long enough to convert to gasoline injectors. That conversion is what got me hired and even though the plant has changed hands 5 or 6 times I'm still here so maybe I owe the designers of that pig a debt of gratitude.

https://en.wikipedia.org/wiki/Oldsmobile_Diesel_engine

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[Lou Scannon]

And they made a V6 version just to make sure to capture the worst of all worlds

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[Hoxton123]

Any British motor cycle engine up to say 1970

 

[PJGD]

In the case of Oldsmobile, they tried really hard to win this award but after a while it became apparent that although even more gutless than the V8, the V6 was somewhat more reliable (it blew head gaskets a little less frequently). So they had a third attempt and designed a 60° V5 engine (details in patent US4480600), and were well along in development with several cars running when the diesel market collapsed so it never reached production. The only redeeming feature of this engine was that it was the first automotive diesel with common rail injection (~1982), way before Fiat or Bosch (1997), and of GM's own concept (details in patent US4360163). These CR injectors used the outward-opening poppet nozzle that Dave was making in the SC factory while I was in the Detroit office supporting the application with Oldsmobile.

 

[PJGD]

Any British motor cycle engine up to say 1970
That would certainly not be true in the case of Vincent HRD, and dubious in the case of Velocette and a few others.

 

[TugboatEng]

There isn't anything inherently wrong with a V5, Honda was quite successful with their RC211V engine.

W engines, on the other hand... Heck, you're probably more likely to come across an Olds 350 diesel than a running Volkswagen with a W engine.

 

[Hoxton123]

PGJD

I will let you have the HRD Vincent, to which I aspired, but not the Velocette, as I had one of those...

I will trade the Velocette for a BMW, though.

 

[CWB1]

I've always been a big fan of vintage BSAs, Nortons, Triumphs, and Matchlesses in particular and never found them particularly troublesome, certainly no worse than the 80s Jap bikes which are known for their reliability. I'm actually looking for another cheap vintage British bike now to build into a commuter bike.

I'd also put an asterisk on discussion of diesel engine market failures stateside. Diesel cars certainly didnt catch on, however diesel pickemups did in the early 80s with the GM/Detroit diesels that are still popular today.

 

[RodRico]

The Napier Deltic, a two-stroke diesel with a triangular arrangement of opposed pistons driving crank shafts at each corner. It was commissioned by the British Admiralty in 1946 with the first delivered in 1950. Per Wikipedia, "While the Deltic engine was successful in marine and rail use and very powerful for its size and weight, it was a highly strung unit, requiring careful maintenance. This led to a policy of unit replacement rather than repair in situ. Deltic engines were easily removed after breakdown, generally being sent back to the manufacturer for repair, although after initial contracts expired both the Royal Navy and British Railways set up their own workshops for overhauls."

 

[Lou Scannon]

Napier seemed to specialize in science projects for engine designs during the twilight era of reciprocating aero engine development: namely the Sabre, and Nomad (with the Deltec into the bargain as a high power density non-aero endeavour). Clever designs all, with some commercial success for the Sabre and Deltec, but none of these concepts caught on as mainstream layouts, as reciprocating engines soldiered on and continued to advance outside of the aero arena.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[Hoxton]

As a design concept the delicious is a star! If you look carefully at the moving diagram, the lower crankshaft rotates in the opposite direction to the other two!

I I think that engines of this era suffered from poor detail design, compared with modern finite element methods etc.