Date: Tue, 15 Feb 2005 23:25:20 +0000 From: Colin Stamp <col.dustbinnospamp.plus.com> Subject: Re: new saab motor for 9-3 series
On 15 Feb 2005 21:08:59 GMT, Dave Hinz <DaveHinznospamcop.net> wrote: >On Tue, 15 Feb 2005 20:53:36 +0000, Colin Stamp <col.dustbinnospamp.plus.com> wrote: >> On 15 Feb 2005 19:45:14 GMT, Dave Hinz <DaveHinznospamcop.net> wrote: >> >>>On Tue, 15 Feb 2005 18:42:38 +0000, Colin Stamp <col.dustbinnospamp.plus.com> wrote: >> >>> >>>> Any six will still >>>> be better than a four, >>> >>>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. >> >> 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. > >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. > Apologies. Feel free not to disprove it ;o) >>>250BHP out of a 2.3L Saab I-4 isn't unusual at all. >> >> Nobody's saying that it's unusual, just harsher than the same power >> from a six. > >Please define "harsher" in engineering (or just real) terms. 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. > >>>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. >> >> More likely that it's more common and so that's where all the >> aftermarket money is. > >Hard to say. > >> Robustness doesn't come into it. There's some >> very flimsy engines with thriving aftermarket tuning businesses >> attached to them. > >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. 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. > >>>> Now, if the 9-3 were RWD... Hmmm, that would be a nice car... >>> >>>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. >>> >> I was thinking from a completely selfish point of view. We only get a >> few days of snow per year in Milton Keynes, > >Oh, I am _so_ sorry. The Magic Roundabout is pretty interesting, though. > >> 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. > >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. > 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. >>>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. > >> 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. > >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. Yep. And the Saab V6 is a niche within that niche. It's niched out of existence. > >>>> 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. > >>>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. > >> 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. > >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. > >> 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. > >Can you quantify "smoothness" as used in this context, please? I'm still defining it as the quantity of vibration that gets transferred into the engine mounts. >Have >you actually _driven_ a dual balance-shaft Saab I4? Or, even a single >balance-shaft Saab V4? 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.
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