3.08s to 4.10s
02-13-2011, 08:35 PM
#1
3.08s to 4.10s There are a lot of opinions on what to do and how to get there. Here's my rationale.
Our car is an '02 B4C (A4) with all stock running gear and a few bolt-ons (26.6" tall rear tires). The big surprise was when I opened the differential and had found 3.08s on an open carrier and not the 3.23 posi it was supposed to have from the factory. I'd always thought the posi was just worn out. Still went 13.2 @ 105mph with the 3.08 peg leg.
We stepped up to 4.10s for a few reasons:
1) We do a lot of mixed driving and this should make the in-town drive more fun and we rarely break 100km/h during the daily commutes;
2) In Ontario anything over 120km/h gets you a ticket; and 50km/h over the posted limit gets you jail time. So that is our peak cruising speed already chosen for us;
3) We auto-x the car more than drag race it. The advantage of a tight stock torque converter and shorter gears will be realized here. But, if we do drag race it the car will be right at the top of the powerband in 3rd according to the calculations; and
4) It is always on street tires so there is a reduced risk of lunching the gear set.
Oh, an Auburn posi unit was added as well.
Take from it what you will...
FYI, 1 km/h = 0.621371192 mph
Our car is an '02 B4C (A4) with all stock running gear and a few bolt-ons (26.6" tall rear tires). The big surprise was when I opened the differential and had found 3.08s on an open carrier and not the 3.23 posi it was supposed to have from the factory. I'd always thought the posi was just worn out. Still went 13.2 @ 105mph with the 3.08 peg leg.
We stepped up to 4.10s for a few reasons:
1) We do a lot of mixed driving and this should make the in-town drive more fun and we rarely break 100km/h during the daily commutes;
2) In Ontario anything over 120km/h gets you a ticket; and 50km/h over the posted limit gets you jail time. So that is our peak cruising speed already chosen for us;
3) We auto-x the car more than drag race it. The advantage of a tight stock torque converter and shorter gears will be realized here. But, if we do drag race it the car will be right at the top of the powerband in 3rd according to the calculations; and
4) It is always on street tires so there is a reduced risk of lunching the gear set.
Oh, an Auburn posi unit was added as well.
Take from it what you will...
FYI, 1 km/h = 0.621371192 mph
02-13-2011, 09:20 PM
#2
you posted your 1/4 results using 3.08s' and tight factory covertor,post up the 1/4 results with the 4.10s' and tight factory convertor after you race it,curious how it ends up.
4.10s' with the tight OEM convertor should be OK for staying in 3rd for the 1/4,I have to get into 4th with the 4.56s' to finish the 1/4.
4.10s' with the tight OEM convertor should be OK for staying in 3rd for the 1/4,I have to get into 4th with the 4.56s' to finish the 1/4.
05-06-2011, 07:02 AM
#4
Haven't made it to the track as of yet because I've been waiting for new axles. However, I have been driving the car on the old ones for a few weeks.
The car has seen:
20mpg combined; and
21+mpg highway (on E10 @ 75mph sustained; add 4% for straight gas).
@ 60mph it revs 2100rpm
@ 75 it revs 2700rpm
Through the stock muffler with cat deletes it is really quite pleasant... the tires make more noise.
The car has seen:
20mpg combined; and
21+mpg highway (on E10 @ 75mph sustained; add 4% for straight gas).
@ 60mph it revs 2100rpm
@ 75 it revs 2700rpm
Through the stock muffler with cat deletes it is really quite pleasant... the tires make more noise.
