Stan's Sportscars Perfomance Center - Extreme Roadster

[Clive George]

So, the BMW engine is rare? Do you drive around with your eyes shut?

Another example from a few years ago - PSA 1.9 16v engine, 1905cc, 160 bhp. So 84 bhp/litre, over 10 years ago. No variable valves, and it was a reliable engine.

True. Those examples are all from > 10 years ago.

Let's look at some more recent stuff. Peugeot 206 - 180hp from 2 litres NA. Renault clio - 200 hp from 2 litres NA.

2001 - Honda civic type R. Rather popular hot hatch, probably because of the 197hp from a 2 litre N/A engine. (the S2000 is 237hp from the same size engine).

Now obviously these are all at the quick end of the market. But they're there, easy to get hold of, and reliable. Which sort of makes your contention that >70 bhp/litre is rare a bit wrong.

clive

[Roger]

The message from Andy Champ contains these words:

75bhp/litre. 11 years on and it had hardly changed - 170 from 2.2 or 77/litre.

Well the Elan Sprint had much the same output as the 2002 320 BMW and that fits the carburettor bill. OTOH it is and was a rare car.

[Roger]

The message from The Natural Philosopher contains these words:

Mine was a bit of a sod to start but that was down to the Webber carbs. There was a technique which I have now forgotten but it didn't include the advice that was current at the time of not using the choke at all. I had to drop that engine into my later Plus 2 after the contents of the petrol tank ended up in the sump (fixed by a cutoff valve that should have been done on recall) and I didn't bother to change the carbs. Dellortos made it much easier to start. It just didn't feel like the same engine.

[Adrian]

Clive George ("Clive George" ) gurgled happily, sounding much like they were saying:

Longer, even, than that - that engine was in the BX 16v in '87.

Indeed. And seriously fun in a car that weighed not much more than a ton...

Panhard were putting out 60bhp from 850cc in the '60s - with two valves per pot, air-cooling, carbs and pushrods.

[The Natural Philosopher]

I couldn't find a Peugot 206 with a 2 liter engine. Anyway thats still not 100bhp /liter.

Renault clio - 200 hp from 2 litres NA.

197bhp on a 16v engine doing 7.25K RPM. So still not 100bhp/liter.

Honda sports cars have what amounts to racing engines in them. Again and exception. 8300 RPM. who really is going to redline at that sort of RPM?

These are all boy racer products competing on specmanship, and probably a LOT less when they are actually put on a rolling road. BIG fast cars knpow that reliability and smooth power deployment comes with bigger engines run with less aggressive port timing.

If you blueprint and balance an engine of course with sufficiently large porting and an RPM limit up around 8300, you can get > 100bhp per liter, till it wears out. with VVT it may even be suitable for road use...;-)

I wonder what it really produces after its been around a few years.

[The Natural Philosopher]

Its easer with little engines, cos the revs acan go higher. Its even easier wit 2-strokes, cos they get two bangs to a 4-strokes one..

I can show you a .36 cu in methanol and nitro engine (about what? 6cc?) that will do over 3bhp...normally aspirated, on a carburettor..at 18K RPM plus..

I've seen an 8 liter drag supercharged racing engine that will do around

5000bhp..well for about 30 seconds..

It doesn't matter how you swing it, you need either forced induction, or >6kRPM to get 100bhp/litre out of a N/A 4 stroke running on petrol.

6K is where you start to run into material and wear problems on anything above 1500cc or so. at 8K you are needing very good porting and valve trains..much over 12K and valve bounce is staring to be a killer, and yu need pneumatic springs to slam the valves shut and keep them there.

Sure, its all possible, but it makes for an expensive fragile engine.

[Clive George]

206 GTI 180.

FSVO "racing engines". They're reliable, built to last, and are happy pootling around - ie perfectly good road engines. And the answer to your question is "the person who wants to go fast" - they're designed to run at that speed.

Oh dear. Those are real numbers, not the made up ones preferred by dodgy "tuners". You're making the mistake of comparing your experience from quite a while ago with what's happening now.

The thing is, the engines we're talking about here _are_ reliable and don't have the lumpy cams you're thinking about. Oh yes - BIG fast cars like the BMW M5? 81 bhp/litre in the late 80s, 89 bhp/litre in the early 90s, and 100 bhp/litre at the moment. The smaller M3 only had 343hp out of a 3.2L engine 7 years ago...

You're behind the times. Yes, VVT is a key part of these engines (though not there on eg the PSA 1.9 16v 84bhp/litre engine). Materials, technology and engineering have all moved on from the engines you're thinking of - more valve area, properly analysed air flow, better tolerances in manufacturing, etc all mean what you consider as racing car stuff are actually available in road cars - and reliable too.

clive

[Clive George]

I think you'll find rather a lot of car makers disproving you there

Yes, and? There's a lot of computer power around these days to get the porting and airflow right.

Honda and BMW aren't noted for making fragile engines (nikasil aside, oops). And TBH the Honda at least isn't that expensive either.

clive

[Adrian]

The Natural Philosopher (The Natural Philosopher ) gurgled happily, sounding much like they were saying:

Umm, that Panhard lump put out peak power at 5,750rpm - and it's a four- stroke. Two-smokes don't tend to have pushrods...

[Andy Champ]

I can't speak for the rest of them, but MR2s are well known for topping

200k miles. Even the turbo versions, which are usually tweaked to 250+.

Unless some boy racer finds out what "snap oversteer" means...

BTW ISTR this started with you saying

... which a bunch of us promptly disagreed with.

Now we have

... which is a different kettle of fish entirely. Did the goalposts move?

That is rare in a NA car engine with current technology. But as has been pointed out, not unknown.

Andy

p.s. It's a litre, not a liter :)

[The Natural Philosopher]

But not run on the redline. Wr goes up as teh square of RPM more or less.

AND in fact has been shown to be true. Its rate to find that. Perhaps 3 models out of 300?

Nope, the original aseertion as that 100nhp /liter was a standard easy to reach benchmark of a N/A performance engine. Its been shown that not only its that EXTREMELY rare, its not that easy to reach.

Depends. I spend too much time talking to septics..