In-line engines at angle

[kurtiejjj]

We all know BT55-BMW story with its laid down engines. But why are there so many problems when installing an in-line (for example 4 pot) engine at an angle? With V-engines there don't seem to be any problems, so why does an in-line engine does?

[Tom]

Erm, the Porsche 914 has an in-line laid at an angle, we worked on a few, generally it was never too bad for reliability, although I think it was an Audi-Volkeswagon design.

[rjsa]

The A-Class (old model) has the cylinder bank in a weird position, tucked under the dashboard, if I remember right.

[dumrick]

V-engines have the same problem, when the angle between the cylinder banks is larger.

I read once an interview with a top responsible of Renault Sport (I believe it was Jean-Jacques His) where he said that one of the two main reasons (the other being efficient acoustics) for dropping the F1's V10 at 109º (or was it 111º?) was the fact that much power was lost from the inefficient lubrication end the extra power the pump needed to compensate it.

But to put it in perspective, in the sadly notorious BT55 (the car that precipitated the decadence from Brabham as a team and from Gordon Murray as a F1 engineer, besides being the car where the great Elio de Angelis died), the BMW M12/13 engine was placed at 72º from the vertical. This generated problems that would only be encountered by a V-engine with a angle between cylinder banks of 144º!

[modbaraban]

The A-Class (old model) has the cylinder bank in a weird position, tucked under the dashboard, if I remember right.

True. It was designed for safety reasons (in order to dive under the floor in case of frontal impact).

...the BMW M12/13 engine was placed at 72º from the vertical. This generated problems that would only be encountered by a V-engine with a angle between cylinder banks of 144º!

So will it be even worse for Boxer-layout engines?

[dumrick]

So will it be even worse for Boxer-layout engines?

That question has popped to my mind, also, while writing the previous reply. I'm not a lubrication expert, so I can only assume that the lubrication channels layout have a radically different configuration in those cases, probably pumping oil from the lower side of the bank to the upper, rather than from crankshaft to cylinder head.

[bettonracing]

From memory, relating to FSAE applications: Oil puddling, dry sump pretty much required, lackluster oiling in cylinder head as well as hot spots in cylinder head (due to water flow 'interrupted' by gravity).

When designing an engine from scratch: Slightly more friction, "arguably" ~1% to 5% (the args are based on whether the increased friction was due to the test specimen having not been designed to run at steeper angles). Friction started to plateau after about 60deg from vertical.

I would speculate that the advantges with the more compact package (and the extra set of cylinders!) for V engines offsets the lost friction compared to an NatAsp 4 pot being tilted on its side for a better CofG.

That being said there are the obvious manufacturers (OEM & aftermarket) making good power with flat engines as well as few making use of tilted 4 bangers (Toyota Rav 4 & camry comes to mind), not to mentioned a few turbocharged 'import' drag cars with slightly tilted engines.

Note to self: the ones intended for power are all turbocharged...

Regards,
Kurt

[Belatti]

Its all compromises, best CoG, easiest and effective lubrication (low friction loses), and also other details (but important) such as easy access to engine parts (for maintenance), security under crashes, engine vibrations and its transmision to the cassis.

[Tom]

I inspected a Boxer engine that had failed once. It had been taken apart by mechanics at a garage and had been drained of fluids. There were many pieces of piston, con road, cylinder wall and assorted metals to examine. I recall after a few hours we managed to assertain that the edge of the piston had at some point dug into the liner and ripped a chunk off each. The piston was then stuck as it returned to bdc and the big end was torn appart. The guy I was with worked this out from the metal fractures, he was able to show where the big end had been stretched and how the metal had come apart suddenly. The broken con-rod then flailed about in the cylinder for a while, gashing and taking chunks our either side before the driver switched it off or it stopped.
I learned alot that day and although I don't remember the final verdict (what had caused the initial fault) I remember that there was a suggestion that the engine was not getting enough oil and that might cause friction which lead to the piston heating and expanding till it could no longer fit into the cylinder.

Please tell me if I'm boring you.

[Belatti]

No no Tom, "0" boring.

Not getting oil kills a common engine in seconds, getting less than necessary, in days, let me ask you a question:
From what car was that Boxer engine? It maybe or not a design failure.

Was the oil pump OK?
Did the driver saw anything wrong before engine blew up? (I refer to low oil pressure indicator light)
Was Oil in general clean, with adecuate viscosity, or it was black sludge? Was there enough Oil?

Sometimes oil can be almost new but inside engine there is mud you cant see and wont go out in oil changes (caused by very rich mixture, low ring-liner sealing, bad oil quality or selection, low engine breathing and oil overheating in some point because cooling system depositions)

Remember the oil is the blood of your engine, is what the doc analises first when you have a disease!

[Carlos]

I would not disagree with Tom let alone Belatti, but ....

The flat engine configuration is a proven design in both production and race versions with a successful history of over 50 years. In another application, aviation, which tolerates a much smaller failure rate than ground transportation, the VW and Subaru flat 4's are a standard engine choice of light aircraft.

I may be mistaken, but that doesn't happen often

[Tom]

Well to answer Belatti, the car was a Porsche Boxer i think, I don't remember much about the case but it was the most interesting one I saw, I don't remember the exact problem or diagnosis. Chances are the final verdict was a likely state of events but it was impossible to conclusively prove thats what had happened.

I'm quite aware of the importance of oil to an engine, my employer was an engineer and taught me alot about that aspect. I also had first hand experience when I smashed my sump off a rock doing a J-turn in the garden. I 'drove it home as quick as I could' which I know is usually the worst course of action but it was only 100m and it didn't do any permanent damage.

Carlos, there are hundreds of these designs that will soldier on for many years and a handful that won't last a few month. Unfortunetly in many cases its just unfortunate circumstances that lead to the demise of the engine, perhaps originating from a poor design but would have been fine if not variable x had been introduced.

Of course arcraft are designed for even weight as well, I think there is something to do with the way flat engines work cancelling out certain forces which plague in-lines, in an object as sensitive as an aircraft that could be the difference between a solid manouverable plane and a bathtub that starts to dive beyond a certain engine speed.

[SZ]

the science of it is simple: so long as you can fuel it, cool it and lubricate it, you can install an engine upside down for all the metal involved cares (in fact for some obscure aero engines, this has actually been the case.) see what you've got for a system, calculate what you're going to need, engineer solutions where you need. same is true for F1, FSAE, Fwhatever.

engine configuration (vee, straight, radial, whatever) has nothing to do with what angles of rotation you can lay it over. more what it's designers intended it to do vs whatever you role in life you're planning on giving it!

practically, getting a working lubrication system is a big constraint or challenge - there's always a solution, it just depends on how much of an engineering problem you want to bite off.

[riff_raff]

An upside-down, in-line piston engine designed by a couple ex-Cosworth engineers:

http://www.wilksch.com/wam-160.html

[Belatti]

My instinct says that the heaviest part of an engine is block/cranckshaft/flywheel assy and putting all those like that would only raise CoG.
But thats only my instinct as I dont have aluminum or steel blocks/cylhead sizes and weights ratios in my head.