EvilBevel

Serious question:

A friend of mine has just bought a Saab Aero 2.3 Turbo. Doesn't look to bad, bit heavy (1800 kg !), 17" wheels, fab interior, limited edition, etc... all for the price of ... UKP 20.300 all in (Belgium). But never mind all that.

When I asked him about torque, he quoted "350 Nm (255 lb/ft) at ... 1800 rpm". I first thought he misread, but when he showed me the flyer, it does indeed state that.

There was also a dyno printout in the flyer, again showing that there is indeed 350+ NM at 1800 rpm. But at 3500 rpm (maybe 4000) torque drops dramatically.

I always thought that as a result of turbo engine design torque would only read it's peak as soon as the turbo is on full song (say 3500 rpm). Peak torque at 1800 rpm with a turbocharged engine seems a contradiction to me.

The other model (2.3 liter non turbocharged) even gives 280 NM (only 10 less than standard UK scoob) at 1800 rpm.

This all seems very contradictory to me. Could anyone shed some light on this as it had me puzzled.

I could understand "small turbo", but still, how can even a small turbo reach peak pressure at 1800 rpm ?

TIA

Theo

Edit crop speling

[This message has been edited by EvilBevel (edited 16 December 2000).]

carl

I don't know the answer, but if you look you'll find that Saab's generally have an absolutely flat torque curve from about 1800 rpm up until about 5500. Supposed to be good for overtaking.

Tim W

iTrader: (1)

Good for overtaking if you can stop the thing from diving for the edge because of the torque steer

Don't for get with the new GM connection Saab and Subaru are going to be technology sharing...4wd Saabs, Subarus with variable compression boxer engines...hmm things could get interesting...

Sparks

Hmm, the GM/Saab link isn't all that great, 93 models are an extended Cavalier chassis, 95 models are an extended Vectra chassis...

Wonder if they've got konis ?

Greg115

They run a high compression ratio with a small turbo. They usually call it a light pressure turbo

EvilBevel

Eh, guys, this question is not about it being a good or bad car.

Don't mean this in a rude way, but I feel we are getting off topic a bit.

It's the technology they used for the engine that interests me, and I would be grateful if someone has some info on that.

Thanks

Theo

Edit: oops posted before I saw your message.

[This message has been edited by EvilBevel (edited 16 December 2000).]

EvilBevel

Greg, is that light pressure turbo comparable to the one I have on my old T5 ? That car still has some turbo lag, so it must be the compression ratio that makes the difference ?

carl

The 2.3 Aero has the 'heavy' pressure turbo. From my recollection it's 2.0 light pressure = 150 bhp, 2.0 proper turbo = 185 bhp, 2.0 turbo with a remap (I think they call it 'high-output turbo') 200 bhp and 2.3 turbo, proper pressure, 225 bhp. The light pressure ones don't have intercoolers, and the normal pressure ones peak at about 0.9 bar I think.

I presume they've got a small turbo that delivers a lot of boost early and from then on the dump valve is always partially open (or do I mean wastegate?). The problem as I see it is if it produces peak boost at 1800rpm, then at 6000rpm it's going to be spinning very quickly. Perhaps they're hardened or something so they can spin faster?

Graham Cowland

If you really want to know about Saabs, give me a call at work (0115 937 7200)and I'll tell you how they do it. (TSL is also a Saab specialist (actually into these before Scoobys) - remember Saab have been turbocharging engines since the 70s!)
For example, on MY 98-00 LPT, we fit a Saab factory upgrade management unit which develops 192 BHP with 300 Nm torque at 3500 rpm....an increase of 42 BHP. Saab use 3D mapping to develop the power (Trionic is the most powerful management system on any production car - around since 1993).

carl

I used to own a Saab (non-turbo, pre-Cavalier shape) before the Scoob, at the same time my father owned an identical looking 900T16S. He's now got an LPT 9-5 with the factory 192bhp chip -- it's not bad but runs out of puff when the charge temperaute gets a bit high (and it's FWD).

With the look of the new Scoob, if they bring out an AWD Saab I might be tempted to return to the fold. But only if it sounds OK -- pre-94 Saabs made a whining noise (chain-driven gearbox) and my Scoob makes a wonderful off-beat throb, but current 9-3s and 9-5s just sound like hairdryers (and the engine's transverse -- a travesty )

dowser

May not be right, but logic suggests;

Small turbo spins up faster/with less exhaust pressure - therefore max boost achieved with very low revs.

Saab always seem to develop their turbo's for driveability - my old shape 900 turbo (Oz spec - well restricted!) had excellent low down torque, but ran out of puff above 5k.

Richard

brickboy

Saab's Trionic engine management is generally reckoned to be the most sophisticated available, and as other posters said, they use a smallish turbo compared to a Scooby or other hottish turbo cars as well as lots of other tricks.

The latest models also have drive-by-wire throttle which helps reduce lag to almost nothing. Apparently when you open the throttle, the ECU opens the throttle butterfly a bit more than you asked it to for a fraction of a second to get the turbo spooled up and kicking, then modulates it accordingly.

I've test driven (just for fun, you understand) a 9-5 Aero, same 230bhp motor. It's amazing. It isn't a sprinter, but you can be in 4th gear, 30mph, stroke the throttle and it just picks up and *flies*. I had to recalibrate my throttle foot!

EvilBevel

OK, thanks for that info. So that Trionic ECU is pretty advanced then...

Next stupid question: is any of that technology applicable to Scoobs ? Or is the hardware too different ?

Graham, would love to give you a call (visited your website BTW), but I'm pretty busy during the day. I asked the question mainly because I have this nightmare where we are all saying to each other "damn, that Scoob is good", and in the mean time, the other manufacturers are coming out with great stuff :eek

The difference between "daily transport cars" and "sporty cars" is getting rather small in some ways (apart from chassis), and I was wondering if we (if Subaru doesn't do it) could benefit from the technology advancements. Imagine having max torque in a modified Scoob at 1800 RPM ... (but of course without running out of puff at 5000 RPM )

sunilp

I drove an ex-mamangers 9.5 estate auto, S Reg, and this was during the time i had my PPP Scooby.

Damn, this thing was quick, as fast as i was accelerating from 20-30, the same rate of needle progression was there from 70-80 and it could stop too (sorry for scaring the bloke at the Zebra crossing)

If i wanted a car in that category i would defienetely look at a 9.5, plus they can be tweaked too

brickboy

Evel, in theory you could do it by getting a Link and remapping everything. You may need to use a turbo with different compressor blade profile, or maybe a smaller turbo that spins up quicker, but it should be easy to rejig the torque curve any way you wanted while still keeping 200+ bhp at the top end.

The other neat trick with turbos is one that VW / Audi have for their diesel turbos. It's "variable geometry turbo" -- basically a movable flap in the exhaust manifold which, at low revs, aims the exhaust gases at the outside of the turbo blades, getting them to spin quicker, then at higher revs it opens fully to let gases go over the whole surface of the blades.

But generally, with turbo tech, Saab are way ahead of just about anyone.