Saabscene Saab Forum - Saab Technical Information Resource banner

1 - 18 of 18 Posts

·
Registered
Joined
·
1,448 Posts
Discussion Starter #1
After conversing in another thread about tire choice it was clear that the 9-3, at least the Viggen, really needed some sorting when it came to traction. Nevermind the rampant torque steer, I can handle that. The handling isn't horrible either, it goes around corners plenty quick, but upon exit it has no traction.

Of course for cornering a limited slip and VRK will solve a lot, but what about straight line traction?

In a straight line, despite 215 tires, and limited boost (12 psi instead of 15) the Viggen can still sometimes lose traction. First gear only allows about 5-6 psi and is still rediculously traction limited. What's the deal??

When comparing to the 9000 I think while both cars are reasonably heavy, the Viggen has less weight in the front. I'm not sure if the 9K's weight distribution, but the 9-3 is around 60-40. My C900 was 70-30, and had far better wet and dry traction.

So if part of it is weight disribution then I'll just have to live with that as little can be done without extensive modification. However I'd like to hear what others have done and get some concrete data on it.

Here's what I have in mind:

Have everyone who can figure out how much g-force their car can accellerate with in gear.

List the gear, and the peak IN GEAR accelleration. (Sometimes additional accelleration may occur between shifts.) And let us know what kind of setup you were using to get that power to the wheels.

If you have your car's weight distribution, or other pertinent data that may be unique to your model list that as well.

If anyone has any existing data in other posts, feel free to add that here. I know Mark E's "Bubbles" has gotten something like .59 g's in 2nd gear. So he could list that as well.

My car:

2002 Viggen, stock with Kumho Excta MX's.
215/45 R17's Y rated
Peak accelleration:

1st: .52 g's (5 psi)
2nd: .42 g's (12 psi)
3rd: .31 g's (15 psi)

Next car?

Dubbya~
 

·
Registered
Joined
·
836 Posts
Why do you think your C900 has 70-30 weight distribution? I seem to remember reading that it was about 55-45 unladen and 50-50 at full load.

Certainly from my experience, my C900T16S had plenty of go, but grim traction, it would spin a wheel in the damp, in 3rd just on the throttle, or as it came up to boost.
I changed it for a 2.0FPT 9000 (same spec engine and same tyres-swapped to the later car) and the traction was no longer a problem. I'd say the 9000 was much more front-heavy than a C900.

I've measured corner weights on my 9-5 and this comes out at 61-39 unladen.
I have experienced traction problems with a 9-3 2.0LPT, on the same road/same hour as which my 9-5 Aero had no shortage of grip/no TCS action.

Is it just something in the 9-3 geometry rather than the weight??
 

·
Registered
Joined
·
1,448 Posts
Discussion Starter #3
My C900 weighed about 2800 lbs (non turbo) and the maximum allowed weight for cargo and passengers was like 960 lbs or so.

So about a 70/30 distribution when empty can work out to nearly a 50/50 (I got 52/48) when most of that weight goes to the rear. Because I also remember reading it was close to 50/50 when fully loaded, and so was the Viggen.

I don't know about the geometry, but what could be different? I can't imagine how fitting a limited slip, or even changing the suspension geometry could affect the traction when both tires are spinning? I can see it helping some in 2nd where generally only one tire gets loose. Or maybe if the tires are not pointing straight because of loose suspension componants ... but seems kind of like there oughtta be some better solutions out there ...

On the note of the 9-5 ... it has the same boost as the LPT in 1st, and weighs more. The LPT also has narrower tires I think, and likely not a sport tread or compound.

Appreciate the input though SJ ... still just trying to make sense of it all.

Dubbya~
 

·
Registered
Joined
·
4,427 Posts
Adrian - one of the things the VRK is supposed to help resolve is poor traction from a chassis widely regarded to be about as stiff as a banana. Combine this with a relatively low first gear and it's a recipe for trouble - even on my old 150bhp LPT.

It's not just about fixing the torque steer, as the two are effects from common causes - maybe you should think about fitting one (or an equivalent set of mods from other suppliers). Just the steering clamp made a world of difference to my Mum's old 225bhp Abbott 9-3 2.0T.

I believe the thinking is that the full VRK (rack clamp, poly bushes, rose joints and cross brace) together dramatically reduce the flex in the chassis under load and keep the front wheels pointing where they should be, rather than slightly off-line. This means that there is less likelihood of the diff shoving torque to one side over t'other and thus more even distribution of the power, less risk of wheelspin.

It's the simplest answer I know of.
 

·
Registered
Joined
·
1,676 Posts
I think your problems have nothing to do with weight distribution - it's pretty close to 60/40 unladen on any Saab; if it were 70/30 turn-in would be, er... interesting... - rather than this it's a function of the mechanical grip afforded by the front suspension set up. Traction on a Viggen should be slightly better than with the 'cooking' models thanks to the thinner anti-roll bar (but the extra traction tends to excarberate the torque-steering tendencies) - but another area to look at would be the bump stops, which the 9-3 seems to hit quite easily. There's one or two folks out there (Dean on TSN for instance) that have shortened the bump stops for this reason. Seems even the 9-3 front set up, which was greatly modified in this respect from the 900 set-up, does not have an excess of suspension travel...

But if your lack of traction is on straight and smooth pavement, I guess this won't be of much help...

A point of note is that with the electronic throttle programmed to overcome turbo lag, throttle response and build up of torque is particularly aggressive on the Viggen which cannot help when trying to transfer the grunt to the ground. That, and it's a 2.3 litre putting out its max torque from 1,800 rpm...
 

·
Registered
Joined
·
1,448 Posts
Discussion Starter #8
Originally posted by Eric van Spelde:
[qb]What tyres (er, tires... sorry about that        ) are you currently running? [/qb][/b]
Currently Kumho Excta MX's in a 215/45 R17 ...

Supposed to be a pretty good tire for the money, certainly WAY better than the stock Pirellis.


And yes the traction trouble is on smooth pavement in a straight line. The idea is that I would like to be able to put down full power at least in 2nd gear. Right now as it stands even 12 psi is pushing it sometimes. Also more than 5 psi in 1st. Not that I expect full power in such a short first gear.

Taking the Viggen to a drag strip is somewhat of a dissapointment as it stands now. From the halfway point on it's faster than nearly any stock car there, but it takes forever to get rolling.

I'm not in desperate need of more speed at the moment for obvious reasons. But there has to be a way to get it to accellerate like other FWD cars can.

And yes that Electronically Controlled Throttle can be bothersome at times. The only positive to it is that at part throttle the car drives like a non turbo. You don't even realize it's turbocharged until you really mash it dow. Then you find yourself waiting just long enough to look confused before getting pinned to the seat.

This is getting interesting though. Still awaiting some concrete numbers though. It'd be nice if I could get the car down (or up in accelleration terms) to more "appropriate" numbers. For the first 100 ft the car may as well be a semi truck, err I mean Lorrie is it?

Dubbya~
 

·
Registered
Joined
·
1,676 Posts
Nowt particularly wong with the MXs that I know of - but for your specific application and desires I would look a notch or two further up the food chain. Only the very best will do.
As you're in SoCal where it hardly ever rains anyways the obvious solution would be going for a set of DOT legal 'competition' tyres (Toyo RA1, Michelin Pilot Sport Cup, Dunlop SP Super Sport, Yoko A048, what have you...). Might turn out to be an expensive habit, mind you, and the kind of grip these rubbers afford will presumably increase the need for better wheel location (steering rack clamp, poly lower wishbone bushings,...) further.
 

·
Registered
Joined
·
1,448 Posts
Discussion Starter #10
That's sort of been my last resort. Competition tires grip insanely well, but it still doesn't solve why the stock 9-3 and even a VRK fitted 9-3 still doesn't likely have the straightline traction of say, a lightly modded (traction wise) 9000 ... or numerous other FWD cars.

Well thanks for all the input thus far. Eventually I may come back with VRK, limited slip, competition tires, and a broken gearbox. If it's not one thing it's another ...

Dubbya~

edit: BTW it's raining right now.
 

·
Registered
Joined
·
8,216 Posts
On my 9K Aero, I can put down all the torque in 2nd gear in a straight line in the dry. And I have no boost limit in 2nd gear! So that's about 330 lbft of torque. And I have a slightly lower than standard final drive, so I'd say traction is pretty good. This is borne out by acceleration times of 0-60mph in 5.1 seconds and 0-100 in 12.

What I have that you might try is sticky tyres (Bridgestone S-03), an LSD and the rear shocks (and the fronts too, but I believe it's the rears that make the difference in this situation) turned up really hard to reduce weight transfer to the rear under acceleration.

Oh, and best straight-line traction was with the standard 16" wheels. I don't get quite such good results with the 17" wheels, although these help with cornering.

For drag racing, you could also try lowering the pressure in the front tyres a bit.
 

·
Registered
Joined
·
8,948 Posts
Well i've probably got both extremes in very similar cars.

My Aero is at 280+ bhp and 300+ ftlb and on Bridgestone S03's - They really stick, even in 2nd and flooring it.

My 2.3 Carly is at 200- 220 bhp and 270 ftlb and on Khumo Exsta 712's - They are diabolical, wheel spin and sliding all over the place. I would say that they are one step away from being Damgerous...
 

·
Registered
Joined
·
1,448 Posts
Discussion Starter #13
Currently the Viggen sits at about 255 hp give or take, and 300 lb ft.

I'll have to try some S03's next time around.

I've also often heard that 16" wheels do better in a straight line. I may buy myself a couple 16" racing wheels and stick competition tires for the track. But for every day driving looks like the VRK and suspension mods.

Hopefully they will do the trick.

Dubbya~
 

·
Registered
Joined
·
229 Posts
I found the traction problems with the Viggen to be far more annoying than the torque steer!

Getting out of wet junctions with even minimal power the standard chassis and tyres produced wheel spin.

First off I got a VRK and Abbott uprated rear anti-roll bar fitted, which not only tamed the vast majority of torque steer, but helped a lot of my traction problems.

Saab decided to fit Dunlop SP Sport 2000's to the Viggen in the UK. After reading the great results /john has had with the 9000's, I have to assume the 2000's bear little resemblance to their bigger brother since I found it was still pretty easy to break traction with them. In the end I swapped over to Bridgestone S-03's - the difference between the two was like night and day. Even when getting out of junctions quickly wheel spin just wasn't an issue, unless you really got excited and made a mess of it . I found after the car was moving it was possible to get my foot flat to the floor in first, without wheel spin!
The same goes for second in the wet

Around a month ago I eventually got round to looking at springs and dampers and eventually went for Koni adjustables and Abbott springs after borrowing a car with this setup. I'm also running the rear of the car a bit firmer to try to help reduce squat under acceleration. The ride quality is actually better than the standard setup too, which is a great bonus!

I now feel this is the car Saab should have released back in '99 and a car that would have actually got them good press.
 

·
Registered
Joined
·
1,448 Posts
Discussion Starter #15
Now that's something I like to hear.


How do the Abbott Springs do with respect to body roll? They sound softer than the factory springs. Or at least of similar hardness. The rear anti-sway bar may help with that though.

The only concern I have with stiff rear sway bars is that it can make braking a little hairy. I found with my C900, while neutral around the corners, and having plenty of traction out of the corners, going in required some fancy footwork or the car would end up sideways.
Very very sideways.


Just want to make sure this isn't a problem with that setup. And now it's time for me to start counting my pennies. Could be a while before I get up that kind of dough.

Dubbya~
 

·
Registered
Joined
·
229 Posts
The car certainly has a lot less body roll than standard. I had a chat with Ed about the stiffness of the springs and he confirmed the fronts are actually slighty softer than standard, for traction. As the dampers are firmer they also keep body roll under control, while I wounldn't say it corners flat, it's not too far off.

The Abbott sway bar is smaller than most of the others I've seen, weighing in at 18mm (iirc 4mm up from stock). I've not had any problems under hard braking, everything stays nice and composed. Backing off mid corner if you've gone it a bit too quick, just results in the front tucking back in to a tighter line. If you've really got it wrong then the tail will step out very slightly, but it hardly needs any correction and certainly nothing that would worry or catch you out.
 

·
Registered
Joined
·
1,448 Posts
Discussion Starter #17
That actually sounds like how it handles (for me anyway) stock ... just ... way better. Definitely have to look into it.

How have the Koni's faired reliability wise? I'd heard some individuals were having trouble with them? Not sure. Appreciate the info.


Dubbya~
 

·
Registered
Joined
·
3,618 Posts
I've heard various reports about Koni failures. Personally I've had Konis on 6 of my last cars (RS2, 9-3, 90002.3T, 900T, 911 3.2S, Impreza Prodrive Turbo) and I've not had one bit of trouble with them (and over pretty big mileages too.. plus lots of track days.) I've had them on the 9-3 since the car was almost new - it's now nearly 4 and they just work - perfectly.

The best think about fitting them to the 9-3 is that they are fully adjustable in the car without removing them - so you can tweek them to your hearts content.

Also note the warranty on them... it's for the life of the damper! Can't say fairer than that


P.S. I've also had the VRK + Eibach springs fitted to my car since near new, and I don't have much trouble straightline dumping my 333NM of torque (at the wheels I may add) from 1500RPM.
 
1 - 18 of 18 Posts
Top