How high HP/Torque can NA engines get to?


BeEfCaKe
05-08-2003, 05:19 PM
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
05-08-2003, 08:51 PM
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
05-08-2003, 09:00 PM
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
05-09-2003, 12:12 PM
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
05-09-2003, 02:56 PM
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
05-12-2003, 05:04 AM
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
05-12-2003, 09:46 PM
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
05-13-2003, 03:03 AM
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
05-13-2003, 05:39 PM
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
05-14-2003, 05:44 PM
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
05-14-2003, 06:03 PM
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
05-14-2003, 06:14 PM
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
05-14-2003, 09:23 PM
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!!!!!:D

ivymike1031
05-14-2003, 10:14 PM
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
05-15-2003, 05:32 PM
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...

454Casull
05-25-2003, 03:24 PM
Depends on volumetric efficiency throughout the range of RPMs, maxiumum RPM, displacement, bore/stroke, combustion chamber shape, A/F ratio, fuel atomization, material selection (mainly to increase the efficiency of conversion from heat to pressure), total friction, etc. etc. etc.

454Casull
05-25-2003, 03:25 PM
A question for all you people: what do you think efficiency means?

454Casull
05-25-2003, 03:33 PM
Originally posted by 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...
The 2003 S2000 makes 153 lb-ft at 7500rpm.

And that last comment is flawed. Efficiency is not about the ratio between power and torque.

SaabJohan
05-27-2003, 11:20 AM
One way to measure how "highly tuned" (has nothing to do with thermal efficiency) an engine is, is by measure the brake mean effective pressure (bmep). If an engine has a high bmep value it usually gives a high power output per displacement if the engine can use higher rpms. High rpm engines usually tend to have lower bmep than low rpm engines.

Another way to measure this is by using power/displacement, often hp/litre. Here it's an advantage to use high rpms. In racing it's important to have a high power/displacement ratio, not only because many classas are displacement limited but also because this allows a light and compact engine. Also, if the power is created by high engine speed instead of large volume the torque will be lower and that is actually a good thing. The torque is lower but the power stays the same, this means that the car will have the same performance as a car with the same power but a higher torque; the difference is that a lighter drivetrain can be used since the torque is reduced (power or torque at the wheels accelerates the car, engine torque destroy transmissions).

Some people tend to claim that power/displacement is misleading since larger engines can't rev that high. Yes, larger engines can't rev as high as smaller engines, but engines with few cylinders or long stroke have the same disadvantage. This is no stranger than a larger engine has a lower thermal efficiency as well as a high rpm engine has a lower efficieny than a low revving one. Just basic physics that every engine designer should know. If we want a small, light engine with a high power output the choice is to use a small high revving engine with a short stroke and many cylinders. On the other hand, if we are going to build an engine for maximum thermal efficiency we shall chose a low revving engine with a long stroke and few cylinders and with the smallest displacement possible.

Also note that highly tuned engines have low torque/power at low rpms, this is simply because their camshafts are design to work well att high rpms with higher flow speeds.

If we have two engines both producing the same torque, one of them is larger than the other but also more low revving. The smaller and high revving engine will produce more power since they produce the same torque. If we put both engines in cars the smaller engine will outperform the larger one. If we further increase the rpm but also lower the torque we can still achieve the same power output as before and the larger engine will again be outperformed.

An optimum torque curve for an NA engine is flat. If the torque curve is flat the power increase with rpm and never drops. Engineers are today working to make the torque curve as flat as possible. But to make a flat curve with maxmum power output is difficult.

454Casull
05-27-2003, 09:32 PM
Originally posted by SaabJohan
One way to measure how "highly tuned" (has nothing to do with thermal efficiency) an engine is, is by measure the brake mean effective pressure (bmep). If an engine has a high bmep value it usually gives a high power output per displacement if the engine can use higher rpms. High rpm engines usually tend to have lower bmep than low rpm engines.

Another way to measure this is by using power/displacement, often hp/litre. Here it's an advantage to use high rpms. In racing it's important to have a high power/displacement ratio, not only because many classas are displacement limited but also because this allows a light and compact engine. Also, if the power is created by high engine speed instead of large volume the torque will be lower and that is actually a good thing. The torque is lower but the power stays the same, this means that the car will have the same performance as a car with the same power but a higher torque; the difference is that a lighter drivetrain can be used since the torque is reduced (power or torque at the wheels accelerates the car, engine torque destroy transmissions).

Some people tend to claim that power/displacement is misleading since larger engines can't rev that high. Yes, larger engines can't rev as high as smaller engines, but engines with few cylinders or long stroke have the same disadvantage. This is no stranger than a larger engine has a lower thermal efficiency as well as a high rpm engine has a lower efficieny than a low revving one. Just basic physics that every engine designer should know. If we want a small, light engine with a high power output the choice is to use a small high revving engine with a short stroke and many cylinders. On the other hand, if we are going to build an engine for maximum thermal efficiency we shall chose a low revving engine with a long stroke and few cylinders and with the smallest displacement possible.

Also note that highly tuned engines have low torque/power at low rpms, this is simply because their camshafts are design to work well att high rpms with higher flow speeds.

If we have two engines both producing the same torque, one of them is larger than the other but also more low revving. The smaller and high revving engine will produce more power since they produce the same torque. If we put both engines in cars the smaller engine will outperform the larger one. If we further increase the rpm but also lower the torque we can still achieve the same power output as before and the larger engine will again be outperformed.

An optimum torque curve for an NA engine is flat. If the torque curve is flat the power increase with rpm and never drops. Engineers are today working to make the torque curve as flat as possible. But to make a flat curve with maxmum power output is difficult.
Good post, but there are two things I'm concerned about. 1: Can you explain how a larger engine is less thermally efficient? And 2: variable-timing cams can flatten the torque curve, especially with the fully-variable kind.

FYRHWK1
05-27-2003, 11:40 PM
less thermally efficient would be simply that theres more area for heat to transfer to, and more liquids to take heat away from the combustion chamber. With a larger engine variable valve timing isn't quite as missed, it can have a camshaft profile capable of pulling until redline but still produce enough torque down low to move the car, in fact most do this ion purpose to prolong the life of the engine since high cyl pressures at low rpms are more damaging.

ivymike1031
05-28-2003, 11:26 AM
let's make sure we all mean the same thing by thermal efficiency, before we get into arguing about different quantities.

I propose that the following definition of thermal efficiency be used for this discussion:
Eff.thermal = (Work output per cycle, at flywheel) / (Heat added per cycle),
where (heat output per cycle) is the heat added after any inefficiencies in the combustion process are considered (Q.in = Q.HV * m.fuel * Eff.combustion)

It is not apparent to me that large-displacement engines will necessarily be less thermally efficient than small-displacement engines. A slower-turning, larger-displacement engine can have considerably lower hydrodynamic friction losses than a small, faster rev'ing engine of the same power output.

SaabJohan
05-29-2003, 06:17 PM
Smaller displacement mean lower heatlosses. But if higher engine speed is used the frictionlosses will increase. So if we are going to build a thermal efficient engine we should have a small displacement and a low engine speed.

The most common variable cams are very similar to adjustable cam gears just like this one:
http://www.hksusa.com/images_products/1250.jpg
The difference is that they are controlled by the engine ECU and oilpressure. The simplest ones have one point where the ECU opens a valve that lets the oilpressure to change the cam timing.
If someone have tested an adjustable cam gear like the HKS on an engine in a bench, you will soon find out by changing the timing the low end power and top end power will depend on the setting on the gear.
So what the engine manufacturers do is that they choose two settings; one for low end and one for high end power. Where the power curves match, that's the adjusting point when the ECU will open the valve that lets the oilpressure change the timing.

454Casull
05-29-2003, 08:20 PM
Originally posted by SaabJohan
Smaller displacement mean lower heatlosses. But if higher engine speed is used the frictionlosses will increase. So if we are going to build a thermal efficient engine we should have a small displacement and a low engine speed.

The most common variable cams are very similar to adjustable cam gears just like this one:
http://www.hksusa.com/images_products/1250.jpg
The difference is that they are controlled by the engine ECU and oilpressure. The simplest ones have one point where the ECU opens a valve that lets the oilpressure to change the cam timing.
If someone have tested an adjustable cam gear like the HKS on an engine in a bench, you will soon find out by changing the timing the low end power and top end power will depend on the setting on the gear.
So what the engine manufacturers do is that they choose two settings; one for low end and one for high end power. Where the power curves match, that's the adjusting point when the ECU will open the valve that lets the oilpressure change the timing.
True, engines with smaller displacements lose less heat, but the ratio of heat loss:displacement is higher than a larger engine (assuming same bore/stroke ratio) because, IIRC, as a cylinder "grows" (again keeping bore/stroke ratio) its ratio of volume to surface area increases.

I think I just confused myself.:bloated:

ivymike1031
05-29-2003, 11:21 PM
454, it sounds like you're on the right track to me. The most efficient piston engines that I'm aware of (thermal) are extremely large displacement engines (vs automotive) that run very slowly (~100 rpm).

Typically one has power requirements determined by an application, and cannot simply opt for a small displacement, low speed engine. For a given power output, it seems to be generally true that a large-displacement, slow engine is more efficient than a small-displacement, high speed engine. (talking piston engines only)

Then again, arguing about the relative efficiency of gasoline-fueled engines is a bit like pissing into the wind while discussing whose feet are wetter - best to find another hobby.

Steel
05-30-2003, 12:00 AM
soo... what would be the thermal effeciency of THIS?!
http://performanceunlimited.com/illustrations/mostpowerful-engine.html

ivymike1031
05-30-2003, 08:36 AM
based on the link you provided, "over 50%."

pod
05-30-2003, 12:46 PM
who the hell would need a 3 story engine

454Casull
05-31-2003, 03:49 PM
Cruise ships.

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