Choosing a Torque Converter Efficiency Rating

[Begle1]

From what I've read, the different companies sell different rated torque converters; 89%, 91%, 93%. (Or is it only Goerend's that does that?)


So how do you choose what rating? What are the advantages of a lower efficiency rating? I would assume that a lower number would be easier on the rest of the driveline, so it would be ideal for a heavy truck, but I'm sure it's more complicated than that...

[wannadiesel]

Depends on the power and the intended use. If I had an automatic I'd want the 93%, but if this was a tow rig I'd be smarter to put in the 91%. If you were to buy a converter right now you'd want the 89%. The more power you have, the tighter the converter ought to be.

[Begle1]

So what is the disadvantage of running a tighter torque converter without having much power?

The extra slop in the converter gives the engine more time to spool so that it doesn't lug it down as bad?

[wannadiesel]

Too tight a converter will bog the engine down, it'll never get spooled. It's like being in too high a gear with a manual.

[Begle1]

I still don't get it.

If the torque converter stalls at the engine's peak torque RPM, then maximum power will be spinning the converter regardless... A looser torque converter will allow the engine to rev higher, but wouldn't that be past the peak torque?

No, wait... I don't hit maximum boost until above 2000 RPM; the total amount of fuel injected increases with RPM, and so boost builds accordingly. While peak torque occurs lower, max boost can occur higher. Like climbing a hill, I can get over 20 PSI, but that only happens at 2200 RPM.

So a tight converter would keep you from spooling as fast, but you're still at peak torque....

Ahh, okay. You'd be putting more power to the ground with the 93%, but you wouldn't have the horsepower to do it very fast, so you would actually slow down. Like a manual in too high of a gear... Got ya...

Regardless, how bad would the affect of the 93% be on a underpowered truck? It would still probably be world's better than stock, right? What power level is recommended for use with the 93%?

I got the 18cm housing, 9 mm head, vaguely functional gauges and a 3200 RPM governor and piston pump in the wings; I could get enough power through pump tweaks to be content, right? Then it'd only get better as I go to stage two with water injection, a wastegate and POD's...

[BC847]

A torque converter is modified form of a hydrodynamic fluid coupling, and like the fluid coupling, is used to transfer rotating power from a prime mover, such as an internal combustion engine or electric motor, to a rotating driven load. As with the fluid coupling, the torque converter takes the place of a mechanical clutch. Unlike a fluid coupling, however, a torque converter is able to multiply torque when there is a substantial difference between input and output rotational speed, thus providing the equivalent of a reduction gear.

As found here ~ http://en.wikipedia.org/wiki/Torque_converter

A 91% converter will hook-up much sooner and put more horsepower to the ground doing it. This is good for a play/drag truck for example.

An 89% converter will provide more torque in a lugging situation such as a work truck pulling a load out of mud.

Remembering that energy is neither created nor destroyed, the looser converter, it will convert more apparent HP to apparent torque.

In our application, one of the downsides here is, the looser the converter, the greater the amount of energy being converted to heat. MPG also goes down with the additional slip.
With a tighter converter, one could say the increased power to the ground is, in the case of the former, the energy lost to heat.


Again thinking of our application, it comes down to a compromise.

This make sense?

[dpuckett]

The stock VEs in our pickups came with a 12mm head, not 9mm. If you indeed have a 9mm head, you wont ever see 200hp.

That said, I think there is only one company that sells their convertors based on % efficiency. There was a write up in the TDR magazine that pointed out the #s arent totally accurate, as when one sits at a light, there is 0% efficiency, yet when cruising down a mountain grade you may achieve well over 100% appparent efficiency.

Daniel

[Begle1]

The stock VEs in our pickups came with a 12mm head, not 9mm. If you indeed have a 9mm head, you wont ever see 200hp.

I'm talking the engine head, not pump head; the non-intercooled trucks have a 9 mm injector in them, which is good to around 300 horsepower, but the head likes to crack too. The intercooled heads don't have the cracking problems, but they have a 7 mm injector that is only good to around 250 horsepower.

That said, I think there is only one company that sells their convertors based on % efficiency. There was a write up in the TDR magazine that pointed out the #s arent totally accurate, as when one sits at a light, there is 0% efficiency, yet when cruising down a mountain grade you may achieve well over 100% appparent efficiency.

I kind of suspected that Goerend Brothers' was the only company to use the efficiency scale (under which case it's as accurate as they say it is...). As far as I can tell Suncoast, DTT and ATS tell you that they "make them as tight as they can" and that they'll "take as much power as you can make", so who knows how they really relate to Goerend. I think that the GB 91% and 93% are probably a bit more tighter than the other brands, as I've never heard of the other three's converters lugging down the engines...

[Begle1]

Hey, wait a second... It's DTT that sells converters based on efficiency, isn't it?

[charger 69]

When I got my converter from Hughes they told me that you don't want anymore than an 89% for towing which is mostly what my truck does.It did drop the trans.temp.noticeably so it must be working.

[Begle1]

I got a Goerend's installed for $550.

Of course, the first gen model only has a 100,000 mile warranty and nobody stipulated the efficiency rating, so I don't know what I ended up with.

Actually, I sent Goerends an email, and then waited a few days and went ahead and ordered one by phone. And then after the thing was sitting on my table I got a reply email asking what application the converter would be for...

So I REALLY don't know what I got. But it's better than what I had.

[charger 69]

Thats a reasonable price as I had to install mine but i did the rear seal and flexplate at the same time. I know empty that if I even bump the fuel a hundred rpm. it wants to take off.