torque convertor too loose?

[rtviper]

How do you tell if the convertor is too loose? I noticed my datalog indicates I crossed the finish line at 6100 rpm in 3rd gear with a t-400. My mph was only 128 mph. The datalog show a shift at 6500 rpm from 1st to 2nd with a drop of 600 rpm. I cant tell the next shift cause the most I see is a drop in rpm of 200rpm. On 1 run I let off cause the shift light never blinks off after the 1st shift at 6k. I stll run a 10.8 at 115 mph. The convertor is a 4500 stall. The rpms never drop below 5950 rpm after my 1st to 2nd shift untill the end of the run. I have 3.42 rear ratio and 28 inch tires

 

[azgn]

my car with the "N" stall Art Carr shows 6100 at 128 also (however, my et's are 10.4-10.5 at that speed).......if your launches are at least low 1.4x or better, converter is fine.....your shift points could also be raised to 6500-7000 no problem

 

[rtviper]

Thanks AZ. I 60 ft at a best of 1.5 but thats only using 4lbs at launch.I have only made about 5 runs so far.I looked at my datalog again and on the 10.4 run I went to 6500rpm and the shift came down to 5900. That drop was 2.6 seconds into the run. During the next 7.8 sec. the only drop in rpm I see is 250 rpm at 4.7 sec into the run and the rpm never goes over 6250 rpm the rest of the 1/4. Mph went from 103 to 128 from 1/8 to 1/4. The only time the shift light went out was on the 1st to 2nd shift

 

[rtviper]

AZ I have thought about what you said. Shifting at higher rpm might give me a bigger drop at the shift. Also would turning up the boost to get more power have the effect of tighting up the convertor or would it make it looser?? I would like to turn it up to about 24lbs but only if the convertor seems to be working correct Thanks

 

[azgn]

turn it up!

shift it at 6500 min......think you'll like it!

(launch it harder too....I typically leave at 15 lbs.......)

 

[norbs]

Adding more boost will only add rpm to the stall. Sounds like the converter is pretty in-efficient at the topend. Do a tire size and rpm calculation at top end and see the % slip.

 

[rtviper]

Norbs that is what got me started on this issue. Besides the fact my car is at 5950 to 6200 rpm from the time I shift into 2nd gear till the end of the 1/4. I did the calculations and if I did it right they say I should be doing 148.64 mph at 6000 rpm in high gear 1 to 1. The formula is:

Overall Tire Diameter X Achieved Engine RPM (redline)
----------------------------------------------------= mph
differential ratio X top gear ratio X 336

I am at 128 mph? Is that too much loss? Now if I add more boost thus more power will the loss increase?