new saab motor for 9-3 series

At any given TDC, three pistons will be at the top. Two will be on one side, and a half-revolution of the crank later, they'll be on the other side. Vastly oversimplified, but it's a dynamic load on the engine that doesn't exist in a V4, V8, or an I-anything.

I don't have any complaints or concerns about an I6.

Well, not to dis the Alfa, but...

Well, sure, but if you want 6 pistons, arranging them in a V is a poor choice. I don't know of any V6 engine that has the reputation for longevity that, for instance, the Saab I-4 2.0 engine does.

Dave Hinz

Reply to
Dave Hinz
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Well, sure, it's compact, but that's a benefit for the designers and assemblers, not for the owners.

Reply to
Dave Hinz

I2, V2, I4, V4, V8, V6, V10, all they suffer from either first or second degree vibrations that do not exist in I6, V12 nor any boxer engine.

BR:Z

Reply to
Zon

There's good detail on the 3.6 GM Alloytec engine here:

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Reply to
saabyurk

I see what you mean about straight 6 vs. V6, but I thought we were comparing the current four-pot against the new V6. Any six will still be better than a four, and as the power goes up the difference gets more marked. Up at 250BHP, a four is going to be getting decidedly harsh. Saab does play the luxury card, after-all.

You would if you tried to fit it transversely in a 9-3. It might go in a Humvee, but I pray I never see a Saab wide enough for a sideways straight 6!

Now, if the 9-3 were RWD... Hmmm, that would be a nice car...

I'm not going there! Mine worked fine though.

It's a compromise, like everything else, but it's worth it as the power goes up, if you want refinement. Straight sixes just aren't an option in a 9-3, so if you want 6, it has to be a V6.

Cheers,

Colin.

Reply to
Colin Stamp

Agreed...I remember the Oldsmobile I4 powered Aerotech back in the late 80s. Pushed out 750 BHP.

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- tex

Reply to
Tex

yes.

Based on specifically what facts? The worst six in the world is better than the best 4 in the world, is what you're saying.

250BHP out of a 2.3L Saab I-4 isn't unusual at all. Something to consider: Why is it that the aftermarket performance mods are _all_ for the I-4, none for the V-6? I would submit it is because the 4 is more tune-able and robust.

There has been at least one, but it was a special case. Google for "saab monster"

Now, you're just pulling my leg. RWD is anti-everything that Saab is about. If you live in a climate with lots of snow, and you've driven both, you couldn't possibly make a statement like that.

IF the power goes up, putting a less reliable design in, isn't worth it to me. Maybe if you're a 3-years-and-out kind of owner, then that doesn't matter. But, since I can tune an I4 to much more power than the V6 offers, I think it's a null statement. And the dual balance-shaft design of the I4 is very vibration free.

BMW seems to be able to fit an I-6; GM doesn't because they have a handy V6 that they can cram into wherever it mostly fits.

Reply to
Dave Hinz

Actually, I shouldn't have used the word "better". It should have been "smoother". Also, of course, it's assuming a level playing-field. If you find yourself having to trawl the third-world looking for a V6 that's harsher than a high quality four, then I rest my case m'lud.

Nobody's saying that it's unusual, just harsher than the same power from a six.

More likely that it's more common and so that's where all the aftermarket money is. Robustness doesn't come into it. There's some very flimsy engines with thriving aftermarket tuning businesses attached to them.

Nice experiment. It puts me in mind of this :-

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I was thinking from a completely selfish point of view. We only get a few days of snow per year in Milton Keynes, and when we do, driving on the roads is impossible because of all the stationary traffic. In normal conditions, big power and RWD is great fun. The biggest problem my 9-3 has, is traction. My old Nissan 200SX had no-end less power but was much quicker off the mark. I miss that.

Sure, if you're buying to tune, then buy the one you can get all the tuning kit for. That isn't related to cylinder count, just where the tuning companies think the money is.

BMWs all have RWD and hence longitudinal engines. I can see where you're coming from, a straight six is no-doubt *possible*, but they'd never sell enough to make the huge changes to the whole powertrain worthwhile. You can't blame them for not doing something that's bound to lose them shed-loads of money. The smoothness difference between a straight and a V 6 is pretty marginal anyway.

Cheers,

Colin.

Reply to
Colin Stamp

You're the one who made the absolute statement that was a massive oversimplification, so please don't put the burdon of disproof on me for your statement.

Please define "harsher" in engineering (or just real) terms.

Hard to say.

Yes, and Saab engines aren't among them. One would think that those who buy the V6 because it has more pistons, would be _more_ likely to demand performance upgrades - and yet, they're still not out there.

Oh, I am _so_ sorry. The Magic Roundabout is pretty interesting, though.

Well, different technologies for different needs. In my part of the USA, the side roads where I live won't be bare for about 2 months - hard packed snow/ice is the road surface. 2" snowfalls barely make mention in the news, let alone a disasterous traffic situation.

If you say so. Me, I see it as a sign of what's do-able or not. Saab tuning is enough of a niche market in the first place, after all.

Well, the c900's I4 was longitudinal, with the tranny below. Another

2 cylinders wouldn't add any _length_ to the powertrain, compared to the BMW I-6. It could be done.

Can you quantify "smoothness" as used in this context, please? Have you actually _driven_ a dual balance-shaft Saab I4? Or, even a single balance-shaft Saab V4?

Dave Hinz

Reply to
Dave Hinz

Or a SAAB (with a Ford) V6?

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-- MH '72 97 '77 96 '78 95 '79 96 '87 900T8

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Reply to
MH

I've seen a car like that. Nose-heavy beast. Capri V-6 bolted right up, though.

Reply to
Dave Hinz

overheating too...

and Ford Taunus 20M (2 litre displacement)

-- MH '72 97 '77 96 '78 95 '79 96 '87 900T8

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Reply to
MH

Apologies. Feel free not to disprove it ;o)

By harsher, I mean more vibration transferred to the engine mounts.

Every time a cylinder fires, the engine gets pushed upwards with the same force that the piston gets pushed downwards. Also, the engine gets twisted backwards with the same torque that twists the crank forwards. It's not possible to balance either of those forces out. Balance shafts etc. can only compensate for the moving masses of the pistons, rods and whatever. The forces from combustion change dramatically from overrun to maximum torque. The flywheel won't help either. One very effective way of reducing this vibration is to increase the number of cylinders. The pulses are moved closer together so they overlap more and their peak value is reduced for a given average power.

I don't do marketing, but I bet it's lack of demand more than anything else. V6s are seen as a "luxury" engine as opposed to a "sporty" one.

Yep. We're not set up for snow at-all. It's cheaper to just let it completely pole-axe us for a couple of days a year.

Yep. And the Saab V6 is a niche within that niche. It's niched out of existence.

I'm still defining it as the quantity of vibration that gets transferred into the engine mounts.

I've got a 9-3 Aero. It's plenty smooth enough for me, but I'm easily pleased as far as smoothness is concerned. My gut feeling is that the V6 156 did have less vibration on full throttle than the Saab, but on either car at full throttle, you have plenty to take your mind off any vibration :o)

Cheers,

Colin.

Reply to
Colin Stamp

Can you cite evidence for this, specifically in regards to Saab's dual balance shaft I4 design that's been in use for a decade or more?

Yes.

Counter-rotating balance shafts.

How much of the vibration is induced by the combustion vs. the reciprocating mass?

Well, it has some effect, but there's no differentiation there because (as far as I know) all cars have a flywheel of some sort.

Have you driven one of these cars and found vibration to actually be a problem? Theoretical "6 is a bigger number than 4" stuff aside, what are you feeling that apparently others are not? Have you measured the vibration transmitted to the driver in one design vs. another? Have you considered engine mount geometry and dampening characteristics?

There's a lot more to this than "6 is bigger than 4".

If you say so. For whatever reason, nobody offers performance upgrades for the V6, so if you want power, the V6 is the wrong engine to buy.

So, kindly don't destroy the design made for bad weather just because you don't get it. I mean, I haven't gone and said "take off the windscreen wipers because it doesn't rain much here", have I?

I thought you said you preferred it?

But, who cares how much gets _into_ the engine mounts? It's what gets _out_ of them that matters.

Well then.

So, it's a guess based on a preconceived notion, with no actual measurement to back it up. I understand. I think you're worrying about a non-problem.

Reply to
Dave Hinz

So that's how they do it.

I read somewhere many, many years ago that a 6-cylinder engine (in what configuration, I don't recall) is inherently balanced whereas a 4-cylinder engine is one of the worst, if not the worst, in trying to get it to run smoothly. My experience over the years has found this to be at least approximately true in that, other than the Saab, the 4s have been rather rough running while the old Corvair and the 6-cylinder Porsches run quite smoothly.

Reply to
Everett M. Greene

Odd, and I've heard exactly the opposite. Even in a non-balance shafted I4, there are two pistons up, two pistons down, at any given time.

Well, sure, but the Corvair and Porsche engines are flat-6 boxer configuration engines, right? So, any out of balance is in the same plane and cancels itself out. It's having the balance differences on two intersecting planes that make the forces get "interesting".

Dave Hinz

Reply to
Dave Hinz

The four cylinder inline engine is far from the worst. It is much smoother than a flat V2 engine (e.g. like a two cylinder boxer engine but with both pistons moving in the same direction all the time) or that terrible V2, with the wrong cylinder angle, used by Harley Davidson.

Reply to
Goran Larsson

Flat V2? Never heard of that one... seems like the firing order would be uneven too in that case. The standard boxer engine works because the two cylinders reach TDC simultaneously and alternate firing. or is the Flat V2 a 2-stroke thing? That might work...

-Fred W

Reply to
The Malt Hound

Nope. Can you provide evidence to support this :-

"the only people who want a V6, are those who don't know enough to know it's a step backwards."

Completely useless for the combustion forces. They only work for forces which are constant at a given RPM.

My money is on the combustion forces being heavily dominant at full power. You can demonstrate this yourself since they fall to zero with the throttle closed. Just accelerate at full throttle to 6K RPM or so, noting how much vibration you get at the top end, then go straight to overrun and check out how much smoother things are as you coast down. Also, look at the design of I-2 engines. Both pistons move in unison, which is the worst setup for balancing their masses, but the best setup for reducing the combustion-induced vibration. Why is it done like that, I wonder?

Nope, although the most powerful four I've driven my 200ish BHP 9-3.

I haven't felt anything particularly convincing in either direction, nor did I ever claim to. It's just based on the engineering theory, but it's a really easy bit of engineering theory to understand. As a quick plausibility check, I note we're not all driving around in vibration-free, balance-shafted, single-cylinder cars.

No. Have you? You were the fist to imply that a V6 was "unbalanced" compared to a straight 4 after all.

Irrelevant to this argument. We're talking about engines, not mounts.

I never said there wasn't, but a 6 really does have more cylinders than a 4 (honest) and that makes a big difference.

If it's a Saab, and if you want to make upgrades, then yes.

Don't worry. No-one will take any notice of me, so the FWD is safe. How about 4WD? Would I be allowed that?

I don't recall saying I preferred V6s anywhere. I've never even seen a Saab V6, nor do I know anything about it and it's problems. I'm talking about V6s in general, and why they might have their place in the lineup of a brand like Saab.

As I said above. The engine mounts are irrelevant. Whatever they do for a four, they can also do for a six. More vibration in = move vibration out. If you want to compare engines, you have to restrict yourself to engines, otherwise you'll go potty worrying about all the other variables that might change.

My priorities for engines (which probably coincide with yours, incidentally) don't have any bearing on what seems to be the one real bone of contention - that a six, even if it has to be a V6 will cause less vibration that a four for a given power output (and that effect will increase as the power output increases, by the way).

Nope. It's a conclusion, based on sound engineering principles and backed up by some vaguely-relevant personal experience.

Cheers,

Colin.

Reply to
Colin Stamp

Mine is a matter of opinion, yours was a statement of a specific, measurable physical phenomenon.

And what is the proportion of those forces?

Right, which would be where it'd be logical to calibrate the balance shafts. I'd be shocked if they didn't set them up to do the most good, and I'm not sure I know why you think they haven't.

Dunno, never owned an I2.

So, you _have_ driven the I4 with dual balance shafts, and you haven't experienced the problem you seem to be saying exists. I wasn't confused at what your point was before, but now I am.

Big difference between 1 and 4. Displacement and combustion chamber issues to start.

Hardly the first. Think about those dynamic forces that concern you in the I4, now take 2/3rds of them and put them at a 60 or 90 degree angle to the other 1/3rd of them. Alternate that direction 3 times per engine rotation. There's a whole lotta shakin' going on.

You're talking about vibration. If the vibration never gets anywhere, what difference does it make? You won't feel it being 'harsh' or whatever your term is, it's dampened before it gets near you.

If everything is equal, yes. It's not.

We agree on this, but disagree on the reason. Whatever.

4WD is again a case of marketing taking precidence over actual need. But, go ahead and buy the Saaburu if it would bring you joy. Just don't tell me it's a real Saab.

I'm starting to wonder if I'm wasting my time.

Engine vibration in a car involves the engine -and- the mounts. They're a system. Unless you're running the engine bolted to a test bench, it's absolutely relevant.

IF and only IF all things are equal. The existance of the balance shafts indicates that they are not. Unless your hypothetical or real V6 has balance shafts?

Haven't seen any of that yet.

Reply to
Dave Hinz

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