How high HP/Torque can NA engines get to?

[BeEfCaKe]

How high HP/Torque can a NA engine get to? I don't really mean theoretical, but like one that would fit in a reasonable car.. How can it be done?
Also, this is just an example, but ferrari engines(and many exotic cars), are NA right? What is it that makes them put out such high power without FI?(since they are not FI, how do their power/torque curves look like? linear?)

[Psman32@af]

There isnt really much of a limit. on street cars, ive seen 800 hp from a viper. The biggest thing with NA engines in my opinion is a combination of displacement and revs teh engine can make without restricted airflow.

[MattyG]

A lot of the exotic engines are quite hard tuned straight from the factory. E46 BMW M3 isn't that exotic but its a good example engine-wise...330HP out of a 3.2L Straight six....I beleive its achieved through advanced engine breathing gizmos.

[SaabJohan]

The torque curve is in relation with engine efficiency, where torque is highest the effiency will also be highest.

How high the torque will be depends on the meanpressure in the cylinders, the area of the piston crowns and the length of the stroke.

To get maximum power from a NA engine is just the same with all other engines; you must get everything right, and that is the tricky part.

[PWMAN]

Originally posted by BeEfCaKe
How high HP/Torque can a NA engine get to? I don't really mean theoretical, but like one that would fit in a reasonable car.. How can it be done?
Also, this is just an example, but ferrari engines(and many exotic cars), are NA right? What is it that makes them put out such high power without FI?(since they are not FI, how do their power/torque curves look like? linear?)

If you mean for the street, than it's a lot different. For the track though, INDY makes a 655 CID (10.7L) big block MOPAR that cranks out 1140 HP, but you can add up to a 500 HP shot of N20. It also only weighs 485 pounds with oil and water in the block!

[Pringles]

A good way of knowing how efficient (performance-wise) an engine is, is to look at it's torque-per-liter and hp-per-liter. 75lb/ft and 100bhp is a good average for a street car.

[FYRHWK1]

any specific measurement per liter is a poor way of judging an engines ability, the power curve, weight and size of an engine matter more then a peak numer attained at high RPMs. power per liter, unless limited by class size,only means they took a smaller engine and set its redline higher then a larger one making the same power, torque is sacrificed and sometimes powerband as well, but thats changed alot with variable valve timing.

[Pringles]

Good point. I agree with that. But if you look at power/litre & torque/liter you can make certain assumptions initially as to how efficient an engine is and then investigate further (the power curve, weight and size of engine). Honda s2000 engine has probably the highest figures so you can rightly assume it is a very efficient engine performance-wise (efficiency not ability). Then you look at power curves, weight, etc...

[FYRHWK1]

true, and by no means am i saying 100 hp/liter is easy or useless, making a reliable high RPM NA engine is far some simple, the only thing I have to say about it is it's great use of smaller engines, but trying to apply it to other engines is a touchy subject, larger engines can turn less RPM, put out the same torque and rely on taller gear ratios to keep tire speed up whereas a smaller one needs the higher gear reduction of shorter ratios, it needs more input RPM for that.

[flylwsi]

if you want to talk about higher revving bigger motors though, don't forget that it wasn't uncommon for vette 350s, boss 302s, etc. to rev up near 8k...

and still make big torque and hp...

anything per liter is misleading... it's like the s2000 excuse...

it makes 120hp/l, but only a total 175lb/ft of tq.

whereas a viper makes only 50-60hp/l, and similar tq, but it's still badass...

and yeah, the most efficient and well tuned would be an equal hp/l and tq/l... of around 100/l...

[ivymike1031]

and yeah, the most efficient and well tuned would be an equal hp/l and tq/l... of around 100/l...

Did you have some rational basis for making this silly claim, or did it just seem like a cool thing to say at the time?

[flylwsi]

look at the most efficiently tuned factory vehicles...

most are in that range...

i'm talking about cars like ferraris, that are very highly tuned from the factory...
or the s2k, which is pretty well tuned from the factory... or the new m3...

all of which have pretty similar hp/l as well as (at least somewhat close) tq/l #s...

any increase on these cars usually comes from bigger parts, not just the IHE setups that are common, b/c they're fairly efficiently tuned already...

[v10_viper]

The 655 CID Mopar engine I was talking about has a 5 inch stroke and is able to rev to 8200 RPM before doing serious damage, now that is a strong gadamn engine. I can only imagine if they had made that DOHC and possible hemispherical combustion chambers, that'd be a shitload of N/A power. Also has a 4.563 inch bore, that's one big engine. I'd load that engine with Variable valve timing, a damn strong valve train and everthing else, I bet ya could reach 2000 hp with that, but thats because it has some of the biggest displacement of any engine around that works in a car, believe me when I say this is my most favorite engine in the world yet to be seen, 485 lb weight, fits to stock everything!!, put it in a car that weighs 2500 lbs, you have a 3000 lb car with over 1100 hp. wheee!!!!!

[ivymike1031]

Originally posted by flylwsi
look at the most efficiently tuned factory vehicles...

most are in that range...

i'm talking about cars like ferraris, that are very highly tuned from the factory...
or the s2k, which is pretty well tuned from the factory... or the new m3...

all of which have pretty similar hp/l as well as (at least somewhat close) tq/l #s...

any increase on these cars usually comes from bigger parts, not just the IHE setups that are common, b/c they're fairly efficiently tuned already...

So by "efficiently tuned," I take it you mean something other than efficient? Otherwise you're way off base, because turbo-diesel engines are far more efficient than their gasoline counterparts, and are nowhere near the "optimum" you suggest.

Looking at some of the vehicles you mention, I find the following:
pk torque (ft*lbf), pk power (hp)
S2000: 151, 240 http://www.carenthusiast.com/torq_7.htm
M3: 269, 343 http://bmw.hlabs.spb.ru/b3e46.html
2003 ferrari spider: 276, 400
Mercedes SL55: 376, 493

Unless you're saying that 151 is close to 240, or 493 is close to 376, I think I missed the point...

[flylwsi]

i am not in any way saying that the numbers have to be exactly equal by any means...

and fyi, the s2k makes 175 tq at about 7500, not 151...

diesel isn't something i'm even going to look at, b/c they're tq monsters, not hp based vehicles...