Torque converter performance

Does anybody know exactly how much a torque converter reduces top speed? I have a go cart, I'm running a clutch directly to a 62 tooth sprocket, and it gives me a decent top speed but not a lot of take off power and acceleration in the low end. I am hesitant to put a torque converter on it because I do not know if it will reduce my top speed (which I want to keep or increase) and installing one will require considerable frame modifications as it is a small cart. If somebody can confirm it will add speed (I already know it will give me all the low end torque I want) I will probably go ahead with it anyway, as well as installing a 42 tooth sprocket.
 
I will make two assumptions, tire size lets say in 12" diameter and you are using #420 chain 10 tooth sprocket going to a 62 rear sprocket. (#41 or #40 chain would all come out to the same speed) which is 35mph based on the governor still in the engine. If you put in a torque converter using the same rear sprocket you would only be going 25mph. Switch to a 42 rear sprocket you would go 36mph but with a 42 rear you have lost your low end quick response so you haven't gain anything accept the ability to drive slow with no damage to the torque converter. Since I make clutches and torque converters for a living you can consider these numbers very accurate.
 
I will make two assumptions, tire size lets say in 12" diameter and you are using #420 chain 10 tooth sprocket going to a 62 rear sprocket. (#41 or #40 chain would all come out to the same speed) which is 35mph based on the governor still in the engine. If you put in a torque converter using the same rear sprocket you would only be going 25mph. Switch to a 42 rear sprocket you would go 36mph but with a 42 rear you have lost your low end quick response so you haven't gain anything accept the ability to drive slow with no damage to the torque converter. Since I make clutches and torque converters for a living you can consider these numbers very accurate.
Heres what I found by just trying stuff. With a clutch (10t) directly to a 62T sprocket on the axle I got a top speed of about 47 mph but had no power when trying to take off. I currently have a torque converter installed, but have not top speed tested it yet. I have all the low end torque I could want now, so I'm happy with how it turned out.
 
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