Effects of converter diameter at same stall rpm

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lefty o
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Re: Effects of converter diameter at same stall rpm

Post by lefty o » Sun Jul 01, 2018 10:20 am

Geoff2 wrote:
Sun Jul 01, 2018 5:04 am
Lefty o,
Just because YOU didn't understand the question doesn't mean somebody else doesn't. So with your answer now, that makes two dopes....

I am WELL aware of how a converter works & probably knew it before you were born......

Here is the question again:

If a smaller c'ter with a higher stall speed [ & no other changes ] produces quicker ETs, is it the reduction in rotating wt, or the higher stall, or a combination of both that produced the better #s?

I raised the original question because there are 'thinkers' [ excluding said two dopes ] on this forum. Has anybody been able to come up with a formula or method of determining what percentage of the improvement was due to the stall increase & what percentage was due to the reduction in RW?
obviously you dont DOPE!

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Re: Effects of converter diameter at same stall rpm

Post by gowest » Fri Jul 13, 2018 11:17 pm

I think most of the gain comes from putting stall speed where the engine wants it. But the original question was if the stall speed was the same on two different diameter converters which would be better.
From what I have seen the smaller diameter should run quicker because it should be a more efficient design. To gain stall from a larger converter the fins have to be bent negative, the stator cut quite severely or both. So my feeling is to use the largest diameter converter , with a good efficient design, that will give the needed stall speed without any surgery or excessive internal clearances. This gives the needed stall and the diameter helps carry it on the big end. Also stall torque ratio goes up with stall speed so another reason to get stall speed without whittling which generally lowers STR.
So like everything else it depends on application and RPM range to be run in.

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Re: Effects of converter diameter at same stall rpm

Post by RDY4WAR » Sat Jul 14, 2018 7:04 pm

We went a different direction with the converter. Instead of a 2800 stall which was in it with the 4L60, we've bumped up to a 9.5" 4000 stall with the TH350. It's been run on M/T ET Streets in 255/50r16 which has been fairly predictable most of the time, but does occasionally spin if the track prep is off. We're ditching them for M/T Pro Bracket Radials in 28x9x15.

Hopefully we can get this car to go rounds. I want to cement her interest in the sport by getting her in victory lane. The competition just makes her want it more. The last time out before the 4L60 took a dump, she made it to the semi-finals, cut a .008 r/t and ran a 13.631 on a 13.620 dial, and lost. She's been bugging me ever since about how we can "tighten it up."

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Re: Effects of converter diameter at same stall rpm

Post by tjz450 » Fri Aug 03, 2018 8:56 am

These discussions should include the K-factor of the converters being compared. The fact is everyone's engine has different torque production. K-factor is a constant, different torques will equal different stall speeds. No manufacturer offers the k factors of their converters. Probably because there so modified, they can't. With GM' s converters, they produced many variations of fin angles, and a few stators which let them create dozens of different stall speeds. The street performance converter, I assume, doesn't require special designed stators, so K-factor could be readily determined and explained to the customer.

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