To keep going with what he said, not only shift extention, but a QUALITY stall is going to save you upwards of 20-25 pounds of rotating weight. That is HUGE. I love my TCI SSF3000, and am considering a vacuum modulated tranny and a 4400 stall.

 

I like the vacuum mod. The Edge I am running runs no hotter than the stock converter I am running a different fluid(or was, totaled the car the other day, DEER are bad) but still for a 2800 to run as cool as a stocker efficiency has to be good. Then even if it were less efficient you have the BIG rotating weight savings that would offset any other losses. My car gets used for towing, road trips, strip duty, 20K+ a year daily driver all weather, several of those things you would think would make a high stall intolerable, but I could not be happer with it. I am looking at replacement cars to drive while I slowly fix the other one, thinking wagon and withing the first week I will put the tranny and TC from the other car in whatever I get next I like it that much.

 

Not only do you save from the rotating weight but since a lot of the converters out there are 9.5" you also have a lot less rotational intertia which also increases drivetrain effeiciency. For example if you had a 9.5" converter that weighed 40lbs and a 12" converter that weighed the same all other things being equal you would make more power with the 9.5". This is not to say that aftermarket converters are more efficient than stock ones however, most people can see a 10hp loss to the wheels running a 2800-3200 more the larger you get. However this power loss is made up off the line and by the better shift extension.

 

Been there, done that with a Vig 2800 on one of my old F-bods...Couldn't agree MORE with this guy...And that converter was nothing compared to some of the bigger ones out there...

Mike

 

And BTW, for those of you guys running such big cams on stock stalls, your cars would run soooooooooooooooo much better at the dragstrip with a good 3000+ stall...Personally, I wouldn't even run any type of aftermarket camshaft without at least a descent torque converter upgrade too...The bigger stall w/ some better tires is the single best mod you could ever do for the A4...

 

if aftermarket stalls were really more efficient, they would dyno more HP to the rear wheels. They result in increased drivetrain losses, but this is compensated for by the motor being closer to its peak power more of the time.

On a 6500-7000 rpm shifting motor with a big cam, a stock stall will go faster from a 30mph roll unless it shifts into second. The reason is simple, both cars will be at their peak torque rpms throughout the entire race, and the stock stall will give less drivetain loss.

In many, or most other situations, the aftermarket stall wil lwin.

 

Buy a honda if your going to preach MISinformation

 

Way to go already forgetting about the shift extensions. I can tell you from experience that your fuzzy logic is wrong. The car wont drop as many rpms and will stay closer to peak power, leaving the stock stalled car in the dust.

-james

 

no need to get emotional guys, we're jsut discussing. Ihave no experience with an aftermarket stall. Im going by physics, i may be missing something obvious.

I did remember shift extension. The higher stall will drop fewer rpms, but not by much. Remember its also shifting at lower speeds. Also, the shift extension wont be of any advantage if the shift points are close to 7000 rpm because even on a stock stall, the car will be at peak torque band after the shift.

If the shift causes a fall to 4000 vs. 5000rpm, and the torque at those two rpms is exactly the same, there is on advantage to dropping to 5000. INfact, yo uwill simply run out of gear quicker.

 

On a stock LT1 the redline is at 5850rpms. So no revving to 7000rpms. My stock stalled A4 used to drop back out of the powerband down to between 2-3krpms after every shift, then slowly climb back up in R's and really start to pull again. It wasn't something that was physically felt, I could just tell that's what was happening in both a few races I was in and just in the way the car increased mph. Of course it pulled alot harder in the upper RPM ranges. After my 3000rpm 9.5 inch Vigilante install that all changed. Under the same WOT condition after each shift the R's dropped back to around 4500rpms. Keeping the R's up at all times like this really really woke the car up out on the highway. The biggest improvement I saw was from a dig yes, but the car performed better at all speeds and all rpms. I never experienced that subtle loss in pull like I used to. Car would hit redline,shift,and keep on pulling. I went out and raced a couple buddies I had run before for reference. Before I'd always experience either a slight lead loss, or a larger losing run during and after each shift. Not anymore, it'd just shift and keep on running. The only change being the converter. On a dyno higher stalls usually do eat up a few more ponies, but as we all know dyno #'s don't equate track times. I dropped almost 4 tenths in the quarter with just that one change. I'm guessing I might have actually seen a lower rwhp # if I dynoed before and after. How do you explain that? Also don't forget the torque multiplication of an efficent converter. That's a whole new story.

 

I wholeheartedly disagree with you. I've had no problems whatsoever taking people off the line, from Cobras to modified LS1's. Now, a truer statement would be that you won't get the full potential from this cam on a stock stall and you are correct that a larger stall, like what you mentioned, would net you the biggest benefit, but I, and other people I know with a stock stalled 306, have no issues off the line.

 

You dont want to fall into peak torque, you want to fall into peak horsepower. If your car's torque peaked at 3000, would you shift at 4000? No.

 

A stall is one of the best mods you'll make, really wakes the car up.

 

Back to the question. I asked Lloyd Elliot the same question , his reply; Stage 1 ported heads and a custom CompCam 221/227 .550 / .560 lift on a 114 LSA. I have been the "over cammmed" route in the past & don't want to go there again.
The 114 LSA keeps up the vacum at idle and makes it much smoother, think Sleeper here. Also the cam will come on much sooner [lower RPM]. So thats what I bought, it's not in yet.

 

I knew somebody would say this. And the comparison is inaccurate.

There are TWO factors, engine torque, and rear wheel torque. the rear wheel torque = engine torque x multiplication factor of transmission and rear gear. And acceleration is proportional to rear wheel torque.

In order to get the greatest rear wheel torque, you want the highest multiplication factor AND engine torque. Even if engine torque falls with higher rpm, the multiplcation factor can MORE than make up for that by delaying the gear shift (low gear = higher multiplcation factor). So you would NOT shift at 4000rpm. As soon as you shift, multiplication factor decreases. Even though you might have more engine torque now, your multiplication factor fell so much that you still have lower rear wheel torque, and lower acceleration.

Now comparing a stock stall with aftermarket stall in the SAME GEAR. If the engine torque is the same at 4000 and 5000 rpm, and the multiplication factor is also the same (same gear, same rear end), the stock stall will make NO difference at 4000rpm. The increased horsepower at 5000rpm is being spent as heat, and you run out of gear quicker.

If you dont believe me, ask injuneer or anyone else who has a solid grasp on the physics of HP and torque. This is why I said if you shift at close to 7000 AND have a flat torque curve above 4000rpm, the higher stall will not help during shifts.