Polar Moment of Intertia: SUBARUS main problem?

[Magnus]

Guess Subarus problems gow right back to the car, and its layout. Actually it has a smaller wheelbase than the C4 and the Ford, at the same time it is the longest. It could be that Subarus main problem, and a problem that is extremely difficult to solve without having a new car, is the polar moment of inertia, which has been discussed here a few years ago.
If the PMI is to big, there is no easy way of solving the probs with the sub. If the PMI is the problem it would also mean that Sub would have better results on fast rallies with not so sharp bends, and a deperate need for using the scandinavian flick on gravel. Another result from having a high PMI is that you wear tires harder, especially on tar.
What do you think?

[Tomi]

This is what Pentti has been saying for years.

[Magnus]

Any figures of the new car?

[Magnus]

This is what Pentti has been saying for years.

Yep, but things evolve, and I was interested in if there are some new actions taken with regard to the problem. besides, I have not heard that this problem was subarus specifically. the discussion we had, whenever it was, was mainly regarding the whale: PMI+diffs.
It would be interesting to know if subaru themselves acknowledge this as their main problem.

[Donney]

The Subarus definitely seemed uncomfortable when having to deal with hairpins in Ireland. I guess it might be due to the PMI rather than to the drivers.

[Corny]

The Subarus definitely seemed uncomfortable when having to deal with hairpins in Ireland. I guess it might be due to the PMI rather than to the drivers.

In Germany, all 6 manu cars looked uncomfortable during a hairpin, they all died at the outcoming.. It was worst with the fords :s

[DonJippo]

Any figures of the new car?

New car will have same issues, the engine placement in it is still bad for PMI as far as I know.

[Tomi]

New car will have same issues, the engine placement in it is still bad for PMI as far as I know.

yes, the weight too much in the front.

[farquar wrc]

PMI,it's more like the useless drivers have PMT

[grugsticles]

I think Subaru WRT are very much aware of this and have asked Subaru (JP) to either make the Impreza out of a chassis that is more suited to WRCar reqiurements, or allow them to use a different car.
I would guess that Subaru (JP) opted for the re-modeling of the Impreza.

Does that hold merit?

[OldF]

I have always thought that Subaru has one of the best PMIs because it has a boxer engine and therefore the point of gravity is lower than it’s competitors. Also the Subaru has the gearbox longitudinally, the fuel tank and the battery are in front of the rear axle. That’s true that the Subaru’s wheelbase is relatively the shortest. Maybe Subaru has nowadays the same problem as the Peugeot 307 where too much weight was behind the rear axle. At least Marcus complained about the turning of the 307 in narrow roads with sharp bends. :confused: :confused:

[Magnus]

The height of centre of gravity is of little interest regarding PMI; the lower your centre of gravity, the better the charachteristics on the road, generally, but the PMI is more about how much energy (inertia) you have to overwin in order to rotate the car, i.e. turn it. To keep weight between the axles lower PMI. It is another issue that it is good to have them placed low aswell.

[bt52b]

All the main Subaru models are built on the same Impreza/Legacy/Tribeca platform. Not sure where they would find a new model, unless they built a saloon version of the Prodrive P2....

[N.O.T]

Is the new car much different in dimensions than in 2001 and 2003 when they where champions ??

[noel157]

Hopefully this will help the ortunes of the rally team:

http://www.crash.net/motorsport/f1/news/157497-0/prodrive_admit_f1_dream_has_hit_skids.html

[OldF]

The height of centre of gravity is of little interest regarding PMI; the lower your centre of gravity, the better the charachteristics on the road, generally, but the PMI is more about how much energy (inertia) you have to overwin in order to rotate the car, i.e. turn it. To keep weight between the axles lower PMI. It is another issue that it is good to have them placed low aswell.

You’re quite right Magnus, the point of gravity doesn’t have anything to do with PMI. It just slipped from me because a lower POG make the handling of a car easier.

But I’m still wonder why the PMI would be the reason for poor performance. They have been using the same model for a long time and Petter has been very competitive with the older versions and I don’t think he’s pace has gone nowhere. Or maybe the other manufacturers have been able to improve their car more. If I remember right, Petter said in an interview that they would change the geometry of the suspension. Could the geometry be the reason for the problems?

[SubaruNorway]

Another problem they are strugeling with is that the roadcar is not wide enaugh so the top strut mounts are to far in making the geometri not very good, but the new one is ;)

[johngordon]

I can confirm that the new impreza (08) has a longer wheelbase than the old impreza, however the overall length of the car is shorter. For the 08 car the wheels have been pushed much further into the corners of the car, so the front and rear overhangs have been reduced.

[leno]

where do you get all those informations about car? i also want to read something about their problems or these are only speculations?

[johngordon]

I work for Subaru selling the road versions. The new impreza has been designed for better handling. The new chassis with the new multilink rear suspension setup has also as I mentioned in my previous post got a longer wheelbase whilst also having shorter front and rear overhangs. The New STI on which the WRC car will be based has a much wider track than the older version also.