The advantages of a NA engine?

[Radiation Joe]

Nice write up Swamp. OP, ignore every other post in this thread.

Can't believe how many clueless people feel the need to chime in on things they know nothing about.

Doctor J, you got it right as well.

[Nautik]

Several people have already mentioned it but a good NA engine will allow for very precise throttle modulation when you are at the track. Having a very smooth power delivery lets you get the absolute most you can out of your car in a turn.

This may change over the next 10 years as turbo technology improves (as everyone seems to be investing in it for fuel efficiency reasons) but as of right now, very few turbo setups can compete with a good NA engine in this category.

Question to ask yourself, if turbo cars were always an upgrade, why is the Porsche GT3 considered a superior track car to the 911 turbo which has gobs more power?

[J08M3]

Swamp pretty much summed it up.

Trottle modulation is the biggest advantage of NA. Technology keeps improving on FI and soon you won't be able to tell the difference

Forget about the comments saying Horsepower and Torque are different, that is BS. Horsepower is a function of torque, you can't have one without the other.

[Kyoshi71]

Originally Posted by UNNATRAL

torque helps with straight line acceleration and only in the low rpm range. the m3 is built to perform on the circuit and therefore it does not need torque.

Coming out of a turn or excellerating on a grade requires torque. More from the M3 would have made it perform better at the track.

Originally Posted by GhostRideTheWhip

Turbo cars generally have loads of torque down low, but then die when you're up high in the rev range.

I'm sure there are a few folks from Stuttgart who are going to disagree with this one

Originally Posted by GhostRideTheWhip

The M3 isn't a track car, but it can be tracked every once in awhile. You want a track car, get a Cayman S.

I'm going to get my popcorn out for this one

Originally Posted by Doctor J

Throttle response/modulation of naturally aspirated motors is also better than forced induction.

False. Superchargers are also forced induction and have the same throttle response as NA setups.

[pbonsalb]

Having owned a naturally aspirated E36 M3 with bolt on mods, then centrifugally supercharged, and now turbocharged, I definitely prefer the turbocharger. The centrifugal supercharger makes approximately the square root of peak boost at half peak rpm. Peak boost occurs only at redline. Thus at low to mid rpm, the supercharger adds very little power. You need to rev the engine to high rpm to make power, just like with a stock engine. With a reasonably sized turbo, you have massive torque in the midrange because peak boost is there and do not need to use as many rpm or as much throttle. For these same reasons, aftermarket turbo systems don't work as well on very high compression naturally aspirated engines like the S65 or the S62. All that boost in the midrange would blow the engine. The centrifugal supercharger, with its delayed response -- call that lag if you want -- is much safer for the high compression since there is so little boost in the midrange where cylinder pressure is highest.

I own an E61 535i with the N54 twin turbo engine. That is an incredible engine. Pulls like a V8 off the line. I find no discernable lag.

I bought an E90 M3 because I wanted a newer car that handled great and was pretty fast that I would not have to mod to enjoy. But it is not a rocketship and the torque is not particularly satisfying. I will certainly be open minded about the next M3.

[BBCar]

For me, throttle response & high rev are the biggest factors. But I look forward to the day that turbo engines can rev >8000rpm

[bruce.augenstein@comcast.]

Originally Posted by swamp2

We have two strikes above.

Torque to the wheels rather than at the crank is what is vastly more important than torque at the crank. As it turns our peak hp is typically a way to account for the large torque multiplication provided by gearing that high revving cars typically have.

"Powerband" and area under the curve are in no way specific to to NA engines.

Agreed on all points.

However, and without rancor, I tend to disagree on a number of your pluses and minuses. I'll post in red.

Originally Posted by swamp2

In short here are some of the basics:

NA

+'s

-Can achieve a very flat and broad torque curve which in turn provides flexible engine that feels very smooth in acceleration.

So can forced induction engines. In fact, turbos in particular typically generate Kansas-flat torque curves, because the manufacturers manage boost at any given rpm to achieve just that. Centrifugal superchargers add torque, more and more at high rpm, so the torque curve stays nice and flat after the peak.

-NA has better throttle response than turbo, the benefits there are feel, performance and ease of modulation of traction (strip or track)

Agreed.

-A more simple engine system compared to turbo or supercharger

Kind of agree, but it isn't necessarily so. On point, is a turbo straight six more or less complicated than a normally aspirated V8? It arguably will have fewer moving parts.

I'll add the plus of simplified packaging for NA motors.

-'s:

-Fuel economy for a high revving/high performance NA engine (like the M3) is typically poor

Don't agree. Proof points are the E46 M3 and the S2000.

In my opinion, the single greatest weakness of a normally aspirated engine is that its torque production is limited. For purposes of discussion, let's cap a modern, smog-legal NA engine at about 90 foot pounds per liter. You can quibble, but certainly not by much.

Thus, for a given engine capacity, if you want to go for big power you have to rev the heck out of it. The practical difference on the street is that the power isn't there unless you're already revving it, so lazy speed is not part of the deal. The M3 folks have attempted to deal with this by resonance tuning of the exhaust for lower engine speeds, and resonance tuning the intake for high rpm. The downside is that peak torque takes a hit in favor of a wide band.

From my perspective, the current M3 powerplant is terrific, but in everyday driving, that low-rpm comparative softness is apparent.


Turbo:

+'s

-Achieves high power for a given displacement
-As a consequence of the typically gets better mpg for the same power level
-Great aftermarket tuning possibilities

Agreed on all points.

-'s

-Throttle response is always slower due to turbo spooling/inertia ("lag" or "tubro lag")

Agreed.

-Complexity of a turbo system

I suppose to some extent, but in reality the turbo is simplicity itself, and the wastegate parts are not a big deal, nor is the plumbing, except for packaging - which in fact is a disadvantage.

-Concentrated thermal loading

Yes

-Current technology limits redline (this is mostly about the racy sound and feel of a high revving NA engine)


Disagree. There are no intrinsic lmits on red line compared to normally aspirated engines. The reason that turbo or supercharged engines typically have lower red lines is that you simply don't need to rev as high to get the desired power output.

-Durability of turbo unit itself (the turbo often doesn't last as long as the engine itself)

Not so much. The hordes of perfectly reliable long term runners from Scandinavia and Japan are proof positive. Of course, the BMW record is poor, but I believe the new M3 will incorporate all the reliable fixes that BMW has learned about during the recent X35 fiasco.

-Complex lubrication systems

I guess, but a couple of oil lines and an oil cooler are hardly complicated, especially since most high-performance naturally aspirated engines also incorporate oil coolers. Of course, the turbo car will need a bigger oil cooler, thus further complicating the packaging.

Supercharging:

+'s

-Great power gains at a given displacement
-Does not contribute to any throttle lag
-Preserves the basic torque/power curves of the base engine (if supercharger is aftermarket)
-Simpler lubrication compared to turbo
-Little to no thermal issues compared to turbo

Agreed, except that a positive-displacement blower will enhance the low end and not as much at the high end, while a centrifugal blower will enhance the high end and not so much at the low end.
-'s

-Poor fuel economy compared to turbo as supercharger is basically always running

May or may not be true, as some systems disconnect the blower at cruise via a clutched arrangement, and reconnect when you bang the throttle.

[pbonsalb]

Originally Posted by BBCar

For me, throttle response & high rev are the biggest factors. But I look forward to the day that turbo engines can rev >8000rpm

Whether an engine has a turbo or not has nothing to do with whether it can rev to 8000 rpm. However, most of the high revving engines rev high because they have to in order to make decent power. Those high revs are unnecessary with a turbo since it makes so much power sooner. Generally, you won't find the two together -- high redline and turbocharger though there have been some examples over the years ( like the Japanese Domestic Market Subaru WRX STI).

[mdosu]

Originally Posted by jackka

Hey there, fellas.



I actually wouldn't mind if the M3 came with either, even at a bit higher price. Mainly because I can't think of what specific advantage I would have by having a naturally aspirated engine besides fuel mileage, if that.

I always wondered why it was that the M division decided to go with a 414/295 engine when they could have easily made it much more. Especially the torque output. Why do you think that is?

Alright guys, I'll take these 2 parts:

Turbo cars actually could get better mileage than NA if comparing 2 cars with similar power. The driver can modulate the amount of boost you use when you accelerate. So turbo gives you the "best of both worlds" more power and better mileage if you have self control over your right foot. The idea is, if E9X M3 wanted 400hp with a turbo, they will go down to a 6 cyclinder turbo, and this could get better gas mileage than a NA V8.

Why 414/295, it's about balance, the C63's power overwhelms the chassis. That's why the C63 can never beat the M3 on a road track. The traction control would have to be programmed properly to enable the best combo of slip and control. Drag racing sure, the C63 is king, but an retarded infant chimp could put his foot down and drive an high powered automatic in a straight line. The speed vs hp output is not linearly related as hp goes up, speed goes up but at a dimishing rate.

[3XTR3M3]

Originally Posted by dimabimmer

+1000 very well explained sir!

You're kidding right? Not sure if you're being sarcastic.

[persian54]

Originally Posted by Budge

Turbo lag sucks... Turbos are the poor man's way to achieve more horsepower. If you want more horsepower, then add a supercharger or get a different car.

I agree with what you said except the part in red....

So a Porsche Turbo is the poor man's way of achieving more power?

How about a GTR?

I don't think either of these are a "poor man's" car..

Also, AMG is going the Turbo route as well (I say as well because, as rumor holds it, the M3 will become a TT I6)

I love NA engines.
and I loved FI engines as well.
I would love to take my S65 and s/c it.... I don't think there's anyone on there that would say no (if cost wasn't an issue)

Originally Posted by Nautik

Question to ask yourself, if turbo cars were always an upgrade, why is the Porsche GT3 considered a superior track car to the 911 turbo which has gobs more power?

GT3 weighs less (no rear seats etc)

and if I remember right, the suspension is also considerably different (sorry but I haven't followed Porsche must in the 997 era)
Along with being RWD.

[James T. Kirk]

This is FI...

[James T. Kirk]

This is NA...

[grimlock]

Originally Posted by James T. Kirk

This is FI...

Originally Posted by James T. Kirk

This is NA...

I'm sorry Sir, that makes no sense!
What's the difference?

[James T. Kirk]

^ Exactly.

The point is that they're both great. They both perform. It's just a matter of taste on which you prefer.

[Serious]

Reading this thread is like watching blindfolded cripple try to run down a flight of stairs.

[scalbert]

It was once stated on a Corvette Listserv (of all places) years ago and it was point on, quoted:

It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*

[Dodge2Dub]

Originally Posted by GhostRideTheWhip

The M3 isn't a track car, but it can be tracked every once in awhile. You want a track car, get a Cayman S.

What? The M3 is designed to do just that, run the track. Luckily, they threw in a few leather seats and power windows to "dress" this track car in civilian clothing for daily livability. To say that it isn't a track car is like calling a Monkey with a suit on a business man....no!....it's still a damn Monkey!

Nurburgring Lap Times:
E92 M3: 8:05
Cayman S: 8:16
http://en.wikipedia.org/wiki/N%C3%BCrburgring_lap_times

[grimlock]

Originally Posted by James T. Kirk

^ Exactly.

The point is that they're both great. They both perform. It's just a matter of taste on which you prefer.

Ah! I see.. Master Kirk, shall I scrub the toilets now?

btw, the 'NA' pic looks a little 'FI' if you know what I mean.. I wonder what PSI she's running on those puppies hehe..

[swamp2]

Originally Posted by MVF4Rrider

He's confusing what most refer to as low-end grunt, calling that torque. Torque is important at all rpms, especially the higher rpms for racing conditions.

I'd like a precise definition of low-end grunt.

Originally Posted by MVF4Rrider

Confusing. "All the torque is in the higher rpm?" What torque curve are you looking at? The S65 has good torque in the upper rev range, but it's diminishing toward redline. Not near as much as a typical BMW turbo, but diminishing nonetheless. Peak is at 3911 rpms. It holds near peak until 7K, then falls off considerably. I'd hardly say all the torque is in the higher rpms.

1. The M3 has one of the widest torque curves on the market.
2. Diminishing torque at high rpm is mitigated by rising rpms which give the M3 an almost perfectly linear hp curve.
3. You can certainly feel a falling hp curve typical in less efficient breathers such as Vettes.

Originally Posted by erhanh

What are you talking about?

details are not important

That must be sarcastic. The vast majority of M3 folks get less or significantly less than 20 mpg on the street.

Originally Posted by Kyoshi71

Coming out of a turn or excellerating on a grade requires torque. More from the M3 would have made it perform better at the track.

Correction: Being a lazy driver, not shifting and coming out of a corner in the wrong gear at the wrong rpm can show benefit to a car which produces large torque to the wheels at low rpm.

In case you haven't noticed the M3 best competitors with more torque and hp on the track.

Originally Posted by pbonsalb

Thus at low to mid rpm, the supercharger adds very little power. You need to rev the engine to high rpm to make power, just like with a stock engine.

Originally Posted by pbonsalb

I own an E61 535i with the N54 twin turbo engine. That is an incredible engine. Pulls like a V8 off the line. I find no discernable lag.

I disagree. SC benefits do increase with rpm but I would not at all characterize them as having only a little additional power at mid rpms. Both turbo and supercharges effects asymptotically go to near zero power benefit at idle. I've seen plenty of M3 turbo dynos that show smaller benefits than a supercharger at low rpm.

If you have a turbo, don't really care which one, and you don't feel any lag at all then I must accuse you of not being perceptive enough.

[persian54]

I would love to drive a lotus around the track

I drove a couple in the canyons... and my god it's sex

M3 is fun on the track but it's not dedicated track car.

[crackberry]

Originally Posted by Dodge2Dub

What? The M3 is designed to do just that, run the track. Luckily, they threw in a few leather seats and power windows to "dress" this track car in civilian clothing for daily livability. To say that it isn't a track car is like calling a Monkey with a suit on a business man....no!....it's still a damn Monkey!

Nurburgring Lap Times:
E92 M3: 8:05
Cayman S: 8:16
http://en.wikipedia.org/wiki/N%C3%BCrburgring_lap_times

lol, did you not see the car DIRECTLY above the m3 lap time? its the cayman s with a time of 8:04.