Excellent question and opinions will vary.
Here's mine. If you have a low STR say a 1.86 you get torque multiplication higher into the rpm range. The higher the STR the narrow the band of effectiveness. So you would be getting some benefit and a slight edge.
Now you have to factor in the efficency of the verter. They are a liquid coupling and your looking at any where from 95%-98% effiecent based on the manufacturer. Yank claims to be a very efficent verter then of course so does PI. I have seen the stock unit quoted at 97%-98%.
Next you take into account the stall speed. If you are stalling greater than the stock A4 when it down shifts you have an advantage from both the STR and RPM.
You put it all together and what do you get?
Verter with a 3500 stall and a 1.86 STR would give you an advantage but not much without gears.
You happen to choose a speed where the stock A4 drops right into its torque curve and pulls hard.
If you chose a lower speed that caused the stock A4 to downshift lets say to 3000 rpms the stall would overcome the lower rpm and have the advantage.
The verter keeps you in your power band a greater amount of time so typically it has the advantage even on the highway.
If your looking for narrow band hard hitting for greatly improved 60' go with the higher STR 2.5...2.8 and be prepared to run at least DRs. If you want broad band for the highway and improved 60' go with a lower STR 1.86...you will have a lot more success hooking up on street tires.
I have used both Yank and PI...stalls from 2800-4000 and STR 1.8-2.8 and they all suit a different driving profile.
Give alot of thought to what you want most from your converter,
Matthew
:cheers:

 

If you stay with stock gears go with a 2400-2800 stall max for driveability..

If you go with gears - the go with 3200-3500 stall

:cheers:

BP

 

It's fortunate everyone has an opinion :D I love my PI with 2800 stall and 3.42's. I can consistently turn 1.6 60's at the track, and... at 70mph... you'll have a very tough time catching me if I hit it. :D

I let PI build the TC based on their experience to how I drive the car and that's what they came up with. I'm very happy with it. I suspect if they put a higher stall in it, having nothing in this car to compare it to other than stock, I'd be very happy with it also. That having been said, 1.6 60's on DR's is fast and I can guarantee, slapping it at 70mph is neck snapping.

 

Again, this questions depends on the converter. IMO, if the conveter is small like a PT 2400 or Yank stealth 2600, then the punch will be pretty close from 70 MPH (but the convverter car still coming out ahead a bit).
BUT, if you have a converter like a 3500 or 4000, or 4500 stall, the non-converterd car will be seeing 4 oval taillights very quickly. As someone said, STR also plays a role, the lower the STR, the easier you will launch from a stop, but the more efficient you will be from a roll.
Bottom line, I will take a conevrterd car from 70 MPH every day vs a non converterd car. :smash:

 

Kid, to leran a bit more about converters, go to http://www.converter.cc . There is some good info there, and you can also see what converters Yank makes.
My opinion, go with the 3000 or 3200 if you stick with 3.42s, and you for the Super Yank 3500 if you go 3.42s, or even the ST 3500 if you will be going to the strip lots with DR.

Good luck!

 

Ditto, I went form 2.73 gears, to 3.42 and a SY 3500!!!! Like a new car now! :lol: :lol:

 

What about a 2800 stall with a 1.89 str running 3:15 gears?
Would this be streetable and still have some kick through the power band including the Highway???

By the way, thanks for all the responses. Everyone's opinion's are very appreciated. :D :D

Kid

 

I say 2800 is too low, go at least 3000 IMO.

 

I dont mean to start a converter war or workshop - BUT - Converter stalls are NOT always as advertised. The more HP you have (lets say 400RWHP) will make a 2400 stall to about 3000 before it catches..

They make converters for a C5 (or any other model) and from the factory, they match the stall speed to the FACTORY HP Ratio. Hence, if you are throwing down more than 300RWHP than stock - the stall speed changes..

Which is why I say - go with a lower stall as we ALL KNOW you are going to pimp out your car to be a street demon .. hehe and the stall speed will be higher after you do your heads and cam install .. :cheers:

 

To answer your question (sorry about that) -

IMHO I would go with a 2.0 or higher like 2.5 str IF you are staying close to stock.

Or - if you plan to add about 75+ HP to the car I would stay with the lower 1.86 STR and a lower stall as it is going to be raised anyway by your high tourque output.

I (personaly) didnt enjoy the high stall speed for daily driving - due to the constant high revs of the engine while crusing down the road. Plus, cruising lockup "can" become more inconsistent with higher stalls.

But - hey - I am just one guy with one opinion.

 

I have a 2900 convert in my automatic with a 3.15 gear. I switched to a 3.42. I found myself manually shifting the car from 3 to od in town. The gains on track were worth it.

 

Believe it or not, all of this is fully tuneable through the LS1 Edit software. We've been working hard at managing the TC lockup and shift points for the A4 to get maximum performance on the track, yet still make it very docile when on cruise control or in street driving. It's a handfull to get it right but we're getting real close on mine. Through tuning only, the Vigilante from a bone stock computer (GM stock with the December updates) and managing its lockup and shift points we picked up about 20 rwhp on the dyno. I'm keeping a blow by blow on the work, but I can tell you we put down the best rwhp on my car NA ever so far. Right now we're focusing on getting as much of the parasitic loss out of the A4 drive train as possible, and then will move on to... we'll keep you posted. :D

See you on the 2nd.

 

WOW - :eek: - thats great Bill! Glad to see and hear you finaly getting the kinks worked out on yours as it sounds like you are having a blast! :yesnod:

:cheers:

Keep me posted bro - as I am very curious to hear were you end up!! ;)