Originally Posted By: Ben99GT
Originally Posted By: BuickGN
I discovered two years ago that you can make a non lock convertor much more efficient than a lockup. I'm running a non lockup convertor for the first time in the 15 years I've owned the car and it's awesome. It's only got 2-3% slip at WOT above it's stall rpm. One thing I really like is it allows a turbo car to spool the turbo much easier on the line without torturing the convertor. It doesn't grab much at all under the stall speed and then grabs very efficiently as it approaches the stall speed. It's great for a car like mine that would have trouble building enough boost to get the convertor to it's stall speed. Now those pesky Mustangs can't play the game where they leave me sitting at the line on full boost heating the intercooler up while they take their time to stage.
For the converter clutch to hold that kind of power you need either a multi-disc with high carbon clutches or a setup like this Cobra has, which is basically a 4R100 PSD TCC setup with high carbon clutches. There are 800-900 rwhp cars with this setup going 8s locking up at WOT.
Regarding efficiency, WOT lockup gives you 0% slip, and the ability to run whatever stall speed your combo calls for without much regard for coupling efficiency on the big end. A non lockup converter can never be as efficient as a properly setup lock up converter. We've been down this road, got into numerous debates over this very topic with guys in the local scene. After the doubters have seen this 4R70 with lockup in action, people are wanting to ditch their non lockup TH400s for this setup.
Of course, you will never get the 100% coupling with a non lock convertor. I should've been more clear, the non lock convertors are more efficient with both convertors being unlocked. What I really like about this one is it only has 2-3% slip on the big end.
The convertor I have probably wouldn't be of interest to a large displacement or supercharged car. It's awesome for my setup because with any of the other convertors I ran I would have to sit at the line with the pedal to the floor and slowly get to full boost. That's the problem with a small V6 and a large turbo, getting a convertor that's loose enough to allow the turbo to spool without being too loose up top. The non lock I have feels like it's looser than it really is during street driving when you first let off the brake and touch the gas as it sort of does nothing and then grabs all at once.
What I had been doing for years was running a loose 3,500-3,800 stall lockup but it just wasn't very street friendly and the car is first and foremost a street car. I know this sounds backwards, claiming that a non lockup has better street manners. I now run a tight 2,800 stall partially due to new turbo technology and partially because of the "looseness" under 2,800rpm.
Again, I realize something like this is practically useless to the V8 crowd and a moderate stall with lockup is more practical.
