V motor vs Flat motor
Discussion
Physical size would be partly to do with it. A v-8 is relatively compact.
A Flat 8 would be pretty big.
Flat 4's only sound the way they do, because of the exhaust manifolds collect.
When you fit a set of equal length, such as teh WRC SUbarus use...it no longer has that usual flat-4 sound.
Even unequal length tubular manifolds for a Subaru totally transform the engine note
A Flat 8 would be pretty big.
Flat 4's only sound the way they do, because of the exhaust manifolds collect.
When you fit a set of equal length, such as teh WRC SUbarus use...it no longer has that usual flat-4 sound.
Even unequal length tubular manifolds for a Subaru totally transform the engine note
I think much of it stems for the overall size and shape of the vehicle into which it is placed.
Profs Ferdi & Ferry Porsche, believed firmly that the engine should be at the back. Presumably for reasons of static tractability. Remember, Ferdi had alot of practical experience with farm tractors.
Obviously with that sort of solution in mind the shape of their cars developed, and then it would have been pretty difficult to go for anything else.
IMO Porsche was never about outright power, if you go back to the 356 and 550, it was all about having a whizzy, peaky buzzbox that would go round corners well. The idea doesn't do so well when you get to a straight bit of road.
The americans, and brits, knew this and went for a big engine for more absolute power. It might also be because after the war they could, and the Germans couldn't. The best place for a big lump, from a handling and engineering perspective, is in the front.
So to me it was a battle about outright conering ability versus outright power.
To my mind that's what makes me love the Porsche approach so much. Despite the overwhelming practical difficulties, Porsche stuck with it and usually won out. In my opinion, for performance the rear engine approach is better. Admittedly it's more difficult to deal with in every respect.
It seems that nowadays, everything is mid engined.
That's fine for a car that is optimal, but if you're building a car with a view to using a new engine that you don't yet know about in future, mid engine layouts can be limiting, i'd imagine.
I hate to say it though. I'd not buy a bimmer, not if you payed me. It has nothing to do with motorway driving. You just can't buy a rear engined british car. (Except maybe the atom, is that british?)
Profs Ferdi & Ferry Porsche, believed firmly that the engine should be at the back. Presumably for reasons of static tractability. Remember, Ferdi had alot of practical experience with farm tractors.
Obviously with that sort of solution in mind the shape of their cars developed, and then it would have been pretty difficult to go for anything else.
IMO Porsche was never about outright power, if you go back to the 356 and 550, it was all about having a whizzy, peaky buzzbox that would go round corners well. The idea doesn't do so well when you get to a straight bit of road.
The americans, and brits, knew this and went for a big engine for more absolute power. It might also be because after the war they could, and the Germans couldn't. The best place for a big lump, from a handling and engineering perspective, is in the front.
So to me it was a battle about outright conering ability versus outright power.
To my mind that's what makes me love the Porsche approach so much. Despite the overwhelming practical difficulties, Porsche stuck with it and usually won out. In my opinion, for performance the rear engine approach is better. Admittedly it's more difficult to deal with in every respect.
It seems that nowadays, everything is mid engined.
That's fine for a car that is optimal, but if you're building a car with a view to using a new engine that you don't yet know about in future, mid engine layouts can be limiting, i'd imagine.
I hate to say it though. I'd not buy a bimmer, not if you payed me. It has nothing to do with motorway driving. You just can't buy a rear engined british car. (Except maybe the atom, is that british?)
stevieturbo said:
Every flat 4 car ive driven has to qualify as pretty unrefined
In what way ??? Have you ever driven a Subaru ??
IMO they are excellent cars. For every day use, for having a blast, and just plain driving enjoyment.
Nope never driven a subaru, and if you dont know what I mean then its difficult to explain, but the low frequency sound you get when a flat 4 is wound up and the character of the noise they make is something many numpties find ungood because its not the same as their 3 cyl corsa...
Tacoboy said:
Why does Porsche and Subaru use flat motors?
Why do not more cars use the flat motor?
I reckon that manufacturers prefer having their manifolds/etc x1 for cheapness. Also I suppose there are potential issues with space and the crossflow heads. Cheap is the key word, think cams, heads, gaskets.
I assume the pulsey nature of the exhaust note arises from the firing order AA BB AA BB, this is my explanation for the sound being familiar with ports. I can also say that in order not to produce some funny charge robbing effects, it is important to isolate pairs of cylinders from each other. This sods up fuel injection something chronic, requires 2 throttle bodies, etc. (par for the course on decent modern cars). I would have thought that having "double" slugs of exhaust gas is not the best thing for pressure:flow relationships. Obviously, to take full advantage of such a setup requires a dedicated approach in order to reap the benefits.
NB:- I'm assuming that the firing order of a flat 4 is outlined above, if I'm wrong which I could be, it's all rubbish.
I would add to what Dilbert said by saying that Porsche chose the "flat" configuration because a high centre of gravity at the rear end of a rear heavy car is the last thing you need in terms of handling. (ask any 70's Ferrari BB owner!). This is because the higher the centre of gravity the more weight that is transfered during cornering. On the heavy end of the car this will load up the outer tyre immensely during cornering- increasing slip angles and degrading cornering grip. A stiffer anti roll bar at this end will exascerbate things further.
Add to this the that fact that Porsches used swing axle suspension (on early 356 type cars) with very unsatisfactory toe characteristics and semi trailing arms (later)- again with adverse toe-out characteristics on transient lift-off scenarios.
The lower config certainly helped here!
The flat config also helped legendary land mark FWD cars like the Alfa Romeo Alfasud handle the way it did.
Add to this the that fact that Porsches used swing axle suspension (on early 356 type cars) with very unsatisfactory toe characteristics and semi trailing arms (later)- again with adverse toe-out characteristics on transient lift-off scenarios.
The lower config certainly helped here!
The flat config also helped legendary land mark FWD cars like the Alfa Romeo Alfasud handle the way it did.
love machine said:
I assume the pulsey nature of the exhaust note arises from the firing order AA BB AA BB, this is my explanation for the sound being familiar with ports. I can also say that in order not to produce some funny charge robbing effects, it is important to isolate pairs of cylinders from each other. This sods up fuel injection something chronic, requires 2 throttle bodies, etc. (par for the course on decent modern cars). I would have thought that having "double" slugs of exhaust gas is not the best thing for pressure:flow relationships. Obviously, to take full advantage of such a setup requires a dedicated approach in order to reap the benefits.
NB:- I'm assuming that the firing order of a flat 4 is outlined above, if I'm wrong which I could be, it's all rubbish.
From your previous post LM you obviously know your stuff, and I'm no engineer. But surely the reason why the Subaru engine is well regarded is primarily (and pretty much only) because of the Turbo variant i.e. the Impreza Turbo. And slapping turbos into the exhaust / inlet pipework changes the rules re: flow / pulse tuning, does it not?
Confusingly, there's been the usual nonsense back around 2000 or so where a simple backbox could gain 20-30 bhp on the normal Scooby engine, to the Spec C with different length headers which lost the usual Scooby beaty exhaust. This sort of crap indicates either I need to do a shit load more research or leave it to the engineers.
Anyone know whether the N/A Subaru flat four is actually a good engine??
cyberface said:
Confusingly, there's been the usual nonsense back around 2000 or so where a simple backbox could gain 20-30 bhp on the normal Scooby engine, to the Spec C with different length headers which lost the usual Scooby beaty exhaust. This sort of crap indicates either I need to do a shit load more research or leave it to the engineers.
As said above, the normal headers on the Scooby are unequal, and the WRC/spec C/JDM STi have equal length headers and a slightly fettled turbo to take advantage of the smoother exhaust flow.
Evo Magazine said:
IHI advised Subaru that the odd-phased exhaust cycle of the flat-four engine was causing interference as the exhaust gases entered the turbine, harming efficiency. To cure this, IHI came up with a siamesed exhaust running into twin chambers in the turbo housing, resulting in a much faster spin-up speed and thus less turbo lag.
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