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Some of the worse designed engines?
2

Some of the worse designed engines?

Some of the worse designed engines?

(OP)
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.

RE: Some of the worse designed engines?

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


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RE: Some of the worse designed engines?

(OP)
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.

RE: Some of the worse designed engines?

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.

RE: Some of the worse designed engines?

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.

RE: Some of the worse designed engines?

Quote (enginesrus)

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.

RE: Some of the worse designed engines?

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.

RE: Some of the worse designed engines?

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.

RE: Some of the worse designed engines?

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.

RE: Some of the worse designed engines?

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_en...

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Some of the worse designed engines?

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

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: Some of the worse designed engines?

Any British motor cycle engine up to say 1970

RE: Some of the worse designed engines?

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.

RE: Some of the worse designed engines?

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.

RE: Some of the worse designed engines?

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.

RE: Some of the worse designed engines?

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.

RE: Some of the worse designed engines?

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.

RE: Some of the worse designed engines?

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."


RE: Some of the worse designed engines?

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

RE: Some of the worse designed engines?

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.

RE: Some of the worse designed engines?

The Deltec being a two-stroke, I don't see an inherent reason that any of the cranks has to rotate in a particular direction. The rotational direction of each crank would be an outcome of the detail design. There could be some nuance to the piston phasing so if that drives the need for one crank to rotate opposite the other two I would like to learn the reasoning behind it.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: Some of the worse designed engines?

It has to be that way. In that animation, pay attention to the firing pattern. The combustion events are 60 degrees apart and then there's half a revolution with nothing. To make that work, the phasing of the two pistons on one crank has to be the other way around.

RE: Some of the worse designed engines?

It looks like Fairbanks-Morse outdid the Napier Deltic with the Diamond opposed-piston two-stroke with four cranks.
It was commissioned by the US Navy in 1940 and the prototype was completed in 1942.
Detailed description and history: https://oldmachinepress.com/2019/08/20/fairbanks-m...

RE: Some of the worse designed engines?

Quote (Hoxton)

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

I believe all these opposed piston two-strokes are traceable back to the Junkers Jumo 205 (see http://www.enginehistory.org/Piston/Diesels/CH4.pd... ). There have been many attempts to commercialize the opposed-piston two-stroke diesel (including my own). The leader of the modern effort is Achates Power who is using contemporary simulation tools to address the design's shortcomings. You can see some of their simulation work at https://achatespower.com/cool-idea-for-engine-desi... . If you look at their news page, you'll see a lot of activity including funding from several government agencies as well as collaborative efforts with both Cummins and Ricardo: https://achatespower.com/news-blog/

To the best of my knowledge, the primary drawback of the opposed-piston two-stroke is its tendency to lose oil from the cylinder walls out the exhaust ports. Large marine versions of the opposed-piston two-stroke from Wärtsilä and Mann use high precision metering of oil onto the cylinder walls to mitigate the problem. Per an SAE article (https://www.sae.org/publications/technical-papers/...) Achates "directly addresses these concerns by utilizing intake and exhaust manifolds, a closed crankcase system, and oil control rings which operate outboard of the ports. Previous work has shown the importance of careful consideration of cylinder liner, piston, and ring design in minimizing oil consumption of the OP2S architecture. This work evaluates further refinements in cylinder form, hone texture and oil retention, port sealing ring design, and oil control ring design." My design, a rotating cylinder radial opposed-piston two-stroke, mitigates the problem in two ways: 1) it employs a simple low precision oil metering system and 2) it exploits centrifugal force combined with port features to recover oil exiting the ports.

RE: Some of the worse designed engines?

Been a number of deeply suspect engineering decisions in the engine departments of VAG and BMW in the last 15 years or so.

Insufficient piston ring tension margins giving huge oil consumptions at low mileages. (Also Toyota though)

Ridiculously complex timing-chain arrangements with inadequate tensioning arrangements - sometimes located at the wrong end of the engine, just to make fixing them even worse.

Timing chains in the middle of the engine necessitating the drive sprocket being formed as part of the crank.... what could possibly go wrong?

Oil pump drives tacked on the end of largely unnecessary balancer shafts.

Over-complexity as a general theme.

Recently worked on a friends 2005 Audi A4 V6 2.5 TDI (actually not one of their worst), where the cam lobes had come loose from the hydro-formed shaft and caused general mayhem in the valve-train. A quick count up of the components in just one head got me thinking.... Nearly as many as the whole of my previous gen I5 2.5TDI - which is definitely one of their better efforts.

As for the Olds diesel effort, a different friend though it would be "interesting" to buy a Range Rover which had been converted with one of these engines. I have no idea why he thought that was a good idea, or indeed why the original owner thought it a good idea to convert in the first place. WE learnt pretty quick that it was a big mistake. The only thing that engine if good for is to stop your boat drifting away - and it could hold a pretty big boat.... damn it was heavy!

Nick

RE: Some of the worse designed engines?

Quote (BrianPetersen)

It has to be that way. In that animation, pay attention to the firing pattern. The combustion events are 60 degrees apart and then there's half a revolution with nothing. To make that work, the phasing of the two pistons on one crank has to be the other way around.
Thanks for that. Of course, a triangular arrangement doesn't fit elegantly to a two-stroke cycle; they might have considered a "quadric" instead for a more elegant layout, but then again why bother, what's wrong with a two-crank concept if you're determined to have an opposed layout?

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: Some of the worse designed engines?

I am surprised that no one mentioned the OPOC engine. Or perhaps it doesn't count, as I don't think it ever saw production.

RE: Some of the worse designed engines?

One of the advantages of uniflow 2-stokes whether poppet valves or uniflow is asymmetric port timing. In opposed piston engines the exhaust crank lags behind the primary crank.

RE: Some of the worse designed engines?

I believe Thiokol came up with an 8 piston cross shaped engine with four pairs of parallel pistons (sort of # shaped) but I'm unable to find much about it.
I'd love to know a bit more about it.

"I love deadlines. I love the whooshing noise they make as they go past." Douglas Adams

RE: Some of the worse designed engines?

Quote (RobWard)

I believe Thiokol came up with an 8 piston cross shaped engine

The only reference I could find relating to a piston engine from Thiokol is the "Dyna-Star." You'd have to pay $33 to learn more.


RE: Some of the worse designed engines?

Dedication!
The first link states the model as 1/8 scale, the second link 1/4 scale (unlikely).

je suis charlie

RE: Some of the worse designed engines?

So far, I am failing to see why the name Napier would appear in any thread supposedly about engines of the worst design. Impressive, certainly, but never worst.

As for the Dynastar, these photos are not from the web, but there is plenty of information out there about it, but again the thread seems to have diverged from worst to "interesting" engines.




As an engine that might rank among the worst, consider the 8.2L Leyland 500 fixed head bus engine from 1968. It was designed by the best brains at Leyland at the time and had many good features including timing gears at the rear "nodal" point, and the fixed head was intended to obviate head gasket failures. Most of the time the engine worked quite well, but because the parent bore cylinders were anchored to the cylinder block at the crankcase interface, and necessarily at the top end of the engine also, the problem was that on cold mornings if you drove off immediately after starting up the cylinder would heat up and expand axially faster than the external walls of the block and shear the inlet and exhaust ports hence flooding the cylinders with coolant. So much for no head gasket failure modes.


PJGD

RE: Some of the worse designed engines?

Any cross-flow 2-stroke is the worst engine design. They ran, sure. But that's about it.

RE: Some of the worse designed engines?

Quote (GregLocock)

GregLocock (Automotive)90 degree V6s. Horrible balance issues.

First gen NSX used honda's race winning V8 block design (90*) with two cylinders lopped off then they offset the crank bearing/pins/ whatever you'd like to call them 30*. All if I remember correctly. Not sure what else.

The worst design I ever saw was a two stroke scooter with the oil pump driven off the transmission / rear wheel. It was a chinese mantis scooter. I got it for free, barely running, worked on it periodically and it only got worse until I figured that oil pump situation out. It was such that it only pumped oil when you were actually moving. Made absolutely no sense with a CVT as there was no direct relation between oil flow and engine RPM.

Engineering student. Electrical or mechanical, I can't decide!
Minoring in psychology

RE: Some of the worse designed engines?

Quote (mi8chaelwoodcoc)

it only pumped oil when you were actually moving

WTH were the engineers thinking? Perhaps I presume too much thinking there were engineers involved.

RE: Some of the worse designed engines?

It's a scooter not a stayer.

RE: Some of the worse designed engines?

Quote (3DDave)

It's a scooter not a stayer

LOL! No stoplights allowed, only roundabouts! What's the benefit of only pumping oil when moving?

RE: Some of the worse designed engines?

No wasting fuel idling at lights.

RE: Some of the worse designed engines?

Pretty sure that scooter engine is still "running" when the bike is stopped (no auto stop/start), it's just not getting "lubrication" when stopped. Too long of an idling period means seized engine!

As for the 90-degree V6 engines ... at least those with 30-degree offset crankpins have an even firing pattern, even if they need a balance shaft to run smoothly. GM built loads of rough-running "odd-fire" V6 engines, and then a bunch of "semi-even-fire" V6 engines with 18-degree crankpin offsets. Due to GM not wanting to use different connecting rods from those in the V8 engine and not wanting to change the relationship between the left and right banks, the rods had to be next to each other (as on a V8) even though the journals were offset ... having a smaller crankpin offset allowed more cross-sectional area of the crankshaft at the plane where the two offset journals met.

http://www.britishv8.org/Articles/Odd-Fire-V6-Engi...

The 4.3 litre even-fire 90-degree V6 that replaced the earlier rubbish has different rods from the V8 allowing the crankshaft to be better with an actual separate journal for each rod. Didn't get a balance shaft until later on.

RE: Some of the worse designed engines?

Sigh - WHOOOSH!

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