Blackraven

Yeah, there are rumors that the new M3 will get a straight-six engine with turbochargers.

On the one side, straight six engines have a relatively balanced weight distribution (even without the need for a balancer shaft).

The concern though is mostly with the Force Induction..........and this may not bode well with some BMW enthusiasts.

Anyways, the points mostly discussed here seem to favor more on natural aspiration.

What about from the other side (the forced-induction camp)?

From what I know, one advantage being touted is that it would decrease vehicle weight due to a lighter engine.

One such case is what Audi is touting with its new RS6 Avant. Their claiming something like at least 10% weight reduction compared to the V10 TFSI.

Ford is proclaiming that the upcoming 1.0 liter three-cylinder engine for the Fiesta will have more horsepower per liter than any of the brand's naturally-aspirated vehicles.

Of course, for those into aftermarket tuning, force induction means it's easier to boost performance for those who want it.

And of course, something I've read while browsing the AudiWorld archives:

rominl

iTrader: (4)

high revving engine doesn't have the smoothness imho. my m3 (low displacement and high rev) is just as fast as say the isf (high displacement and lower rev), but i do think the isf drives smoother and quieter

agreed to some extend. low rpm the m3 sounds horrible, but at high rpm close to redline, i personally think it sounds better than the isf. but across the whole band overall, i think isf sounds better.

and i won't say displacement has direct impact on sound. i mean, if i am allowed to go extreme, the 4.8L lfa engine sounds way better than the 5L isf engine (i know, just saying, hehe)

RickL87

I'm also a fan of na so Id also rather have a na v10 or v8 over a turbo 6 etc...

mmarshall

Partially true, Henry, but I don't entirely agree. Simply increasing displacement doesn't guarantee more smoothness, as many larger-displacement in-line fours (like the noisy/unrefined GM Quad-Four and some Dodge/Chrysler powerplants) have proved. Nor does it necessarily guarantee more torque, as a number of factors go into torque-production, like flywheel size/weight, bore-vs- stroke ratio, crankshaft design, and others. With conventional piston engines, in general, all else equal, the more cylinders you have, the more smoothness the engine is likely to run with, though, even there, other factors also come into play, like an odd-vs.-even number of cylinders, balance-shafts, design of the engine-mounts, etc..... But, in general, for smoothness, the total number of cylinders is definitely one of the most important factors, as the Mercedes/BMW/ VW-Phaeton V12s prove if you have ever had a chance to drive one.

Outrage

Forced induction is often used as a compromise solution...

...to allow an engine to fit in to a small space.
...to allow accessory and transmission commonality between a "low" and "high" level engine options.
...to meet fuel economy standards.
...to meet tax rates based on engine displacement.

mmarshall

Yes, all true, but forced-induction also adds complexity, heat, production costs, stress on the engine's internals, the need for more expensive synthetic or Turbo-Approved oils, and (sometimes, but not as much as in the past), extended warm-up/shut-down procedures and idling.

Coconut

The power and smoothness of modern FI engines are at the level or surpassing large NA engines. However I still prefer NA for its simplicity and raw sound. You just can't match the sound of a M6 (V10), C63 or Z06.

My supercharged 3.2L V6 only makes 360hp and 260tq. I have a flat torque curve and the power delivery is smooth but it will never be as smooth as a "small" performance V8. I sure love the supercharger whine though

LexFather

Which is why these twin turbo or supercharged V-8s, V-12s are utterly mind blowing Best of both worlds. I've driven the turbo 4 BMWs that replaced the 6s and I much prefer the 6 even if I lost 2 MPG.

We can include hybrids as well. The GS 450h might have instant torque at any speed but the V-6 still isn't a V-8 and if you know your cars you can feel the difference. Electric power is also being used to substitute cylinders

BNR34

iTrader: (1)

Definitely YES. There is no replacement for displacement, even today 2013 with all these technologies.

Well I take it a little back, the ONLY thing so far that can replace displacement is electric power. But battery technologies are not there yet to support big electric power output for a prolong period.

But if you are solely talking about using boost to compensate displacement, no such thing. Well obviously it is possible, but tons of negatives are created from it.

You can boost a tiny engine to any HP level, but guess what spools up the turbocharger? Displacement! Basically the more HP you want, the bigger the turbo you need, bigger turbo adds lag, and lag sucks. To increase HP without adding lag, increase the displacement to spool the bigger turbo. So see, no replacement for displacement if you care about throttle response.

Same with supercharger, the bigger the blower, the bigger the engine required to spin it.

I learned all of that from modding my previous few turbo cars. Now I prefer big displacement.

That's why performance cars like the EVO and WRX STi are getting obsoleted, there is only so much you can do with 2.0L~2.5L, 300 hp is maxed out. Sure you can crank them up to 1000 hp, but their power delivery is crap.

BNR34

iTrader: (1)

For anyone who don't want to read all of that I typed ^^^^^

Compensating displacement with boost decreases refinement and throttle response.

So no, there is no replacement for displacement, unless all you care is peak power output.

ST430

BS...my old Evo IX had an easily modified 500hp, launched to 60 seconds in under 4 seconds, and could wax with the V8 Vettes, Stangs, and Camaros. They're not maxed out, they're just limited due to what the consumer wants. Mitsu, in their infinite-wisdom, decided to go upmarket to Bimmer territory, where the Evos are not keen into a luxury market. Subby went weird by introducing a funky wagon first, then sedan later. The performance market in general is pretty dead except at the high end. So it isn't because of development (see the FQ Evos), it's because of the demand itself.

ST430

Yes, the next M3 is supposed to replace the V8 with a triple turbo 6 and be faster, take less gas, and still be refined....go figure....

SteVTEC

I do miss the crisp throttle response of nicely tuned NA engines vs. my current turbocharged Bimmers, but they're more than good enough unless you're super picky or tracking the car and demand super precise power delivery and control.

I once started a thread on one of the Bimmer forums lamenting that I missed the nice crisp throttle response of NA engines and most people were in denial and were adamant that you immediately get all 300 lb-ft of torque in the N54/N55 3.0L engines the absolute instant you mat the throttle. Uh, no, and any idiot can figure that out. From a 4th gear slow roll at around 2000rpm coasting for at least 10 seconds (turbo not spooled), it took a good 5 seconds to get to FULL boost and torque. Even an E90 328i loaner sedan with the factory de-tuned 3.0L NA engine had noticeably sharper throttle response than my 335i, which made me kinda miss NA engines which is what that thread was about. Total complete denial by some of those people.

ISFPOWER

iTrader: (20)

+1

ive ridden in a 2.0 mivec engine with 600whp with stock internals. that thing was fast as hell. lag was not bad at all. amazing engines.

2002GGPIS3

I voted neutral, I once had a plate on my eclipse turbo that said " The only replacement for displacement is a turbo". Also I love all types of cars and engines, but usually the more displacement the better.