Higher Stall Torque Converter & A4 for Auto-X? And street?
03-22-2008, 02:22 PM
#1
Race Director
Thread Starter
Higher Stall Torque Converter & A4 for Auto-X? And street?
OK, so I have a C5 with an A4 tranny that I Auto-X about 24 times per year. The car also gets plenty of street driving, about 8000 miles per year. I was wondering if a higher stall torque converter would help in Auto-X? I know I can use something like the Yank SS3600 and still be happy on the street, but would this be any help in an Auto-X situation? What about if I put a 3.73 or 3.90 rear end in?
Thanks in advance
Thanks in advance
03-22-2008, 07:22 PM
#2
Melting Slicks
As always it depends on the AutoX class and what you are allowed to do under the rules...
That said I am not a big fan of loose converters in autocross. Been there and done that, and it isn't as fast on corner entry.
The problem is that with a loose converter, lifting off the gas doesn't provide much engine braking and it is harder to get the car to turn in by doing a bit of throttle lift as you enter the corner to plant the front and get the car to turn in faster. Some folks then try to compensate with weird setups to get the car to turn in, so then they get steady state oversteer, so then they compensate setting a higher idle and then dragging the brakes until the apex (to keep the back end from passing the front end).... well you get the idea.. I'm not saying that it can't work, but there is a lot of compensation being done and that you will have to learn to "drive around" the issues that a loose converter can create.
The good part is that the car is faster off of the corners, which you really need if you are in an A4 with a stock gear. Since the A4 has an 80 mph second gear you are seriously down on torque compared to the stick shift cars that are in second gear at the same place on the track (you are down like 30% in rear wheel torque, assuming that the converter is locked up) so there is a big advantage to it in powering off of a corner.
So as with anything else there are pluses and minuses..
A shorter final drive gear (class rules allowing it) is a better far better choice, since it gets your engine speed up where throttle control is better and you are faster off the corner as well, that's why an A6 would be a lot better than an A4, the short second gear is very close to that of six speed.....
If you don't want to get a six speed, get the shortest final drive that you can live with on the street and that will be the best deal.
That said I am not a big fan of loose converters in autocross. Been there and done that, and it isn't as fast on corner entry.
The problem is that with a loose converter, lifting off the gas doesn't provide much engine braking and it is harder to get the car to turn in by doing a bit of throttle lift as you enter the corner to plant the front and get the car to turn in faster. Some folks then try to compensate with weird setups to get the car to turn in, so then they get steady state oversteer, so then they compensate setting a higher idle and then dragging the brakes until the apex (to keep the back end from passing the front end).... well you get the idea.. I'm not saying that it can't work, but there is a lot of compensation being done and that you will have to learn to "drive around" the issues that a loose converter can create.
The good part is that the car is faster off of the corners, which you really need if you are in an A4 with a stock gear. Since the A4 has an 80 mph second gear you are seriously down on torque compared to the stick shift cars that are in second gear at the same place on the track (you are down like 30% in rear wheel torque, assuming that the converter is locked up) so there is a big advantage to it in powering off of a corner.
So as with anything else there are pluses and minuses..
A shorter final drive gear (class rules allowing it) is a better far better choice, since it gets your engine speed up where throttle control is better and you are faster off the corner as well, that's why an A6 would be a lot better than an A4, the short second gear is very close to that of six speed.....
If you don't want to get a six speed, get the shortest final drive that you can live with on the street and that will be the best deal.
03-22-2008, 08:15 PM
#3
Race Director
Thread Starter
As always it depends on the AutoX class and what you are allowed to do under the rules...
That said I am not a big fan of loose converters in autocross. Been there and done that, and it isn't as fast on corner entry.
The problem is that with a loose converter, lifting off the gas doesn't provide much engine braking and it is harder to get the car to turn in by doing a bit of throttle lift as you enter the corner to plant the front and get the car to turn in faster. Some folks then try to compensate with weird setups to get the car to turn in, so then they get steady state oversteer, so then they compensate setting a higher idle and then dragging the brakes until the apex (to keep the back end from passing the front end).... well you get the idea.. I'm not saying that it can't work, but there is a lot of compensation being done and that you will have to learn to "drive around" the issues that a loose converter can create.
The good part is that the car is faster off of the corners, which you really need if you are in an A4 with a stock gear. Since the A4 has an 80 mph second gear you are seriously down on torque compared to the stick shift cars that are in second gear at the same place on the track (you are down like 30% in rear wheel torque, assuming that the converter is locked up) so there is a big advantage to it in powering off of a corner.
So as with anything else there are pluses and minuses..
A shorter final drive gear (class rules allowing it) is a better far better choice, since it gets your engine speed up where throttle control is better and you are faster off the corner as well, that's why an A6 would be a lot better than an A4, the short second gear is very close to that of six speed.....
If you don't want to get a six speed, get the shortest final drive that you can live with on the street and that will be the best deal.
That said I am not a big fan of loose converters in autocross. Been there and done that, and it isn't as fast on corner entry.
The problem is that with a loose converter, lifting off the gas doesn't provide much engine braking and it is harder to get the car to turn in by doing a bit of throttle lift as you enter the corner to plant the front and get the car to turn in faster. Some folks then try to compensate with weird setups to get the car to turn in, so then they get steady state oversteer, so then they compensate setting a higher idle and then dragging the brakes until the apex (to keep the back end from passing the front end).... well you get the idea.. I'm not saying that it can't work, but there is a lot of compensation being done and that you will have to learn to "drive around" the issues that a loose converter can create.
The good part is that the car is faster off of the corners, which you really need if you are in an A4 with a stock gear. Since the A4 has an 80 mph second gear you are seriously down on torque compared to the stick shift cars that are in second gear at the same place on the track (you are down like 30% in rear wheel torque, assuming that the converter is locked up) so there is a big advantage to it in powering off of a corner.
So as with anything else there are pluses and minuses..
A shorter final drive gear (class rules allowing it) is a better far better choice, since it gets your engine speed up where throttle control is better and you are faster off the corner as well, that's why an A6 would be a lot better than an A4, the short second gear is very close to that of six speed.....
If you don't want to get a six speed, get the shortest final drive that you can live with on the street and that will be the best deal.
03-22-2008, 11:28 PM
#4
Melting Slicks
So, your advice would be to go to a 3.73 or 3.90 INSTEAD of a higher stall converter? I am looking at this for a "down-the-road project". MY current class will not allow it, however I may jump up in classes next year. Since my wife also drives the car, the option of a 6-speed is out.
You might try to find somebody who has done a converter and try it, and if it fits your style, then do it, but before I did that I would want to see and talk to somebody who is doing it successfully and find out what they did with the suspension to help get the car to turn in and see if that set of mods fits your driving style.
Last edited by Solofast; 03-22-2008 at 11:30 PM.
03-23-2008, 12:33 AM
#5
Race Director
Thread Starter
Yup....
You might try to find somebody who has done a converter and try it, and if it fits your style, then do it, but before I did that I would want to see and talk to somebody who is doing it successfully and find out what they did with the suspension to help get the car to turn in and see if that set of mods fits your driving style.
You might try to find somebody who has done a converter and try it, and if it fits your style, then do it, but before I did that I would want to see and talk to somebody who is doing it successfully and find out what they did with the suspension to help get the car to turn in and see if that set of mods fits your driving style.
03-24-2008, 01:38 PM
#7
An SS3600 will improve your acceleration off the corner, but as mentioned before, not much engine braking. An SS3200 is a better compromise, and would work nicely with a future gear change. One advantage of the converter swao is that the afermarket converters are about 10lbs lighter than stock, that's a lot of rotating mass reduction, which will improve acceleration.
You really need the rear gear for best autox type performance, but your highway cruising rpm will start getting a bit high with 3.90's.. I've run 4.10's with a 2800 rpm stall, and it works very nicely.
You really need the rear gear for best autox type performance, but your highway cruising rpm will start getting a bit high with 3.90's.. I've run 4.10's with a 2800 rpm stall, and it works very nicely.
03-24-2008, 02:59 PM
#8
Melting Slicks
Be careful going to high on your stall. I've AutoXed a friend's FC RX7 with a LS1/4L60E swap and a 4k RPM stall. It is down right impossible to drive smoothly. Exiting a turn it was like you clutch-kicked a manual car every time. It made for some fun, crowd-pleasing drifts but it was not the "fast" way around. Obviously you're not considering a 4k stall, but even a 3600 might be too much. If at all possible I'd try and test-drive another C5 w/ whatever stall you're considering and make sure power delivery is smooth and controllable on corner-exit.
-TJ
-TJ
03-25-2008, 10:39 AM
#10
Burning Brakes
Member Since: Jul 2006
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..is it just that there is now a bigger RPM gap untill
the engine brakes..
03-25-2008, 12:02 PM
#11
it allows a lot more slip, and doens't allow your drivetrain to hook up with the engine speed. I would recommend getting some 3.42 or 3.73 gears, and stay very mild with the tc.
