Sevenman's TVR (was SAAB) Blog

October 17, 2009

Some fast driving, maybe some clutch slip

Filed under: Saab — Administrator @ 7:57 am

Got the Aero out of the garage yesterday (it only comes out once every ~ 3 weeks for a good blast), and let a mate drive it down to another friends house about 90 mins away. Before we went to The Boot Inn. for a hearty meal.

It was great to be back in the car. The previous day I had driven > 250 miles in the default work hire car. A 1.4 Corsa. This has 90 bhp, weighs 1155 kg, and feels slower than those numbers indicate. Pulling onto a motorway slip road with a slight incline is unpleasant…

What is worse is that we can use our own car for journeys of less that 150 miles, but if it is further, have to use hire car.

So:
Journey of < 150 miles, use 290 bhp Saab that cruises beautifully and eats up the miles. Enjoy the drive. Journey of > 150 miles, use 90 bhp Corsa that is noisy, slow, and tiring. Get to meetings feeling unhappy.

Was great to be back in the Saab. With the Stg3, and running well, it really gains speed quickly regardless of going up steep hills, my mate doing the driving on the way down seemed content with the performance.

Some time in, when he booted it in 3rd gear, I noticed what sounded like a slight rev rise before it caught again and carried on smooth acceleration.

When I drove it back, we had that a few times under full load, but it was only marginal, and it always caught the revs rise 1/2 second later. I then thought that I remembered hearing that before occasionally as full boost kicked in.

Air temps were ~ 7C, car was cruising so interooler was cold, and the boost was as high as I have ever seen it, a lot of space between the end of the red and the needle.

I think the rev rise/slip is something I have seen before. Don’t normally get it on track because then I don’t use the revs where peak Stg3 torque is (stay higher), and it’s normally summer so outside temps are up, and over a few laps the stock intercooler gets warm so boost is normally lower.

From rolling road a few years back (car should be better now as DI isn’t old, plugs are new and fuel is still V-Power) it kicked out a peak torque of 427nm / 314 ft-lb at the wheels. If one plucks a flywheel loss figure of 10-15% out of the air you could be looking at flywheel torque of 350 – 370 ft-lb.

This is a lot. The Stg3 has an aggressive map, with > 1.4 bar boost at peak, but then it tapers as turbo/injectors can’t keep up.

The clutch has been on for 40k miles, and I am an IAM type driver who very rarely holds the car on the clutch, so I don’t think it is wearing out, just can’t quite hold the peak power. Any opinions?

Had a good chat with my mates about what car I should get if I change. It really does come down to:

1) E46 M3
2) Keep the Saab

Can’t afford 1, so the Saab stays :o)

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