BD Torque Converter

[Chevy Diesel]

Curious if anyone is running one and if they have seen the performance gains stated by BD?

BD claims "stall speed is reduced significantly, resulting in more positive engagement in drive, enhanced low-speed drivability and better fuel economy"

My gut says its a good product, and could be a worthy investment, but only if the fuel economy can be realized.

Thoughts or personal experience welcome.

Thanks,
Kyle

 

[WarWagon]

Waste of money.

"enhanced low-speed drivability" Bull$hit!!! The 6.5 has no power when held to low RPM's.

With the choke over 2200 RPM factory turbo this would help, except the auto trans will shift you over 2200 RPM anyway.

You can get a trans tune that will lock the converter sooner at a lower MPH.

You can get a bigger and better turbo that will let the 6.5 rev up for power. These engines really don't like to be lugged for many reasons one is they start to smoke with more fuel at low RPM's. The factory turbo setup encourages lugging the engine. Adding a bigger turbo you revise the shifting to shift sooner.

My favorite example is a 45 MPH 10 % grade with a rolling start. Factory shifting wants to keep high gear and belch smoke when shifting down brings on the boost and cleans the exaust up as well as allowing you to maintain speed.

I have considered a looser converter to allow the burb with the 3.73's to get to the sweet RPM spot easier.

If you want MPG's remove the turbo and go dual exaust. (The factory turbo takes you from 20 MPG to 15 MPG.) A compromise is a larger turbo, but, you will need to rev it up for power when it is needed. Ultimate MPG is the econo precups out of delivery vans and NA. Turn the fuel way down with that...

 

[Chevy Diesel]

I am in the process of a complete engine rebuild, with all the aftermarket stuff, and installing a he351cw(04.5-07 cummins) custom turbocharger instead of the stock hair dryer. 62x86 compressor, 70x64 turbine, standard (~9cm2) housing, and the wastegate oversized to ~1". I know, small turbine housing not ideal, but I want to give it a shot, there is a market for these turbochargers with the cummins guys if I don't like it anyway.

The 6.5 makes peak torque around 1800 rpm if IIRC, what RPM is the stock torque converter's stall speed set at?

Thanks,
KV

 

[WarWagon]

Peak torque stock is ~2200 RPM and falls off fast. Why they wound it up to 3600 RPM is only for the useless HP number. I have spent lots of time at 2200 RPM WOT as that is all she had towing for hours.

Depending on your build the converter can match it. If you are building peak torque down low then a low stall converter will work. Your small turbo should qualify. You will run out of turbo and converter in the upper RPM's. But if this is your design goal...

Factory the stall speed is too high as locking the TCC clutch will result in MPH gains at WOT with a load. This is because the turbo is choking the engine so bad that it can't use the stall speed at higher than 2200 RPM. Yet at a stoplight and flooring it the stall speed is too low.

I think the stall speed was chosen more to keep trans heating down than peak TQ on this engine.

 

[THEFERMANATOR]

GM is notorious for using to high of a stall converter. Not sure who BD uses to build there converters, but it is probably just a DAYCO unit. Personally I wouldn't spend the kind of money that the big name companies charge when you can buy the same exact converter for less from the actual builder of them. For a 6.5 I would just buy a premium TRANSTAR unit if it was my money. They make a decent converter for the money, and the 6.5 shouldn't hurt one as they run them behind some healthy big blocks. As far as stall speed, it isn't nearly as important as teh torque multiplication at the stall speed. A good converter upgrade will match your stall speed to your power band, as we+ll as improve bottem end torque multiplication to get the load moving and your turbo lit. I went to a lower stall converter in my DURAMAX, and I was shocked at how much quicker the power came in. Sometimes tightening them up will load the engine and make it spool where the loooser converter wouldn't and would make you think it was to tight.

 

[Jorge6.5]

I'm running a Transtar converter in my truck, it is the billet piston torque converter and it works great. I installed it over a year ago and no issues. IIRC I paid $275 for it.

 

[Chevy Diesel]

Thanks fermanator & jorge,

I called and talked to TRANSTAR and their GM81 (1991-1997 6.5L & 7.4L) & GM88(1998-Up 6.5L & 7.4L) Torque Converters are 1800-2000 Stall (which they told me was stock stall speed). They do offer Billet Clutch Piston upgrades for each, which adds an additional $130.

When a torque converter is spec'd as 1800-2000 Stall, is that 2000 RPM Impeller (engine side) and 1800 RPM Turbine (transmission side), since the turbine never quite synchronizes perfectly, due to the mechanical inefficiences, with the impeller?

 

[Chevy Diesel]

Since my turbo should theoretically light fairly quickly due to its small turbine housing, I should want a lower stall speed torque converter right to take advantage of as much of the power band as possible.

I have contacted TCI as well and they have a towing torque converter for the 4l80e that stalls at 1000-1200, they say that this will increase towing capacity, lower transmission temps, and increase fuel mileage.

My question is, what are the disadvantages of the lower stall of the torque converter, I am assuming there is such a thing as stalling too early? And is 1000-1200 too low? I have read posts from others using them, but they were mostly guys in motorhomes. That is a whole different set of parameters to consider than what I am aiming for: good fuel economy going back and forth to work, the ability to step into it and pass at my leisure, and the ability to tow an 18' boat during the summer and occasionally a backhoe on a trailer.

 

[WarWagon]

Yank Performance converters can answer a lot of your questions and may be worth a call.
http://www.converter.cc/FAQ_s/45.htm

Again, the stall speed depends on your engine and load the vehicle can put on the converter. I disagree with the 1800-2000 stall speed factory. Sounds like a stock LS2 Trailblazer SS gasser stall speed to me. HD gassers and 6.5's have a lower stall converter than regular gas trucks. I disagree with the given stall speed because the turbo's light up on my rigs at 2000 RPM. I have a hard time getting them to 2000 RPM even rolling. I suggest the factory 6.5 stall speed is around 1300 RPM give or take.

Not to be sour grapes but this ultra small turbo you want to use will flat suck for towing. I wouldn't go smaller than an HX40II. You may as well throw a manual transmission in it so you can keep the RPM's down. The automatic is not going to let you keep the RPM's down on any hill without crawling along. After towing with the GM3 the engine falls over after 2200 RPM. The transmission would downshift and literately slow you down at the higher RPM, shift again, slow down more from higher RPM, and finally crawl along in 2nd gear. Locking the converter was worth 1MPH with the GM3. Dropping the huge fing ATT turbo on was worth 22 MPH and 3 MPG. Yeah, going from 33 MPH to 55 MPH. 6 PSI factory boost is 33 MPH, Turbo Master @ 14 PSI is like 43 MPH and ATT is 55 MPH less cooling fan and better MPG.

So with a locked converter you gain 1MPH and no MPG. Stall speed is closer or further from lockup. Turbo selection is worth 22 MPH and 3MPG. So with 1MPH difference to play with I suggest other areas to improve.

I burned up the TCC clutch in 50K using the manual TCC lock at WOT.

I hate to see you frustrated with the results of trying different converters and lugging the 6.5 towing. The 6.5 is NOT a long stroke engine like a Cummins with gobs of torque to benefit from a low stall converter. Rather the 6.5 needs to be wound up and be able to breathe when wound up. With the Big ATT towing heavy is a pleasure as the engine has power in the upper RPM band - like it is supposed to.

Daily driver is day and night over the huge load of a trailer. Small turbo, low stall converter makes a snappy unloaded truck around town where you can't wind up the RPM or MPH. Loaded pulling a mountain grade it makes you want to burn the truck and people behind you are applying the slow moving triangle to your trailer and saluting you without all fingers extended as they go by.:rolleyes5: Been passed by semi's with their flashers on. Motivated me to find solutions to stop that humiliation.

 

[Jorge6.5]

I agree with above mentioned about the turbo. It's way to small for a 6.5, I wouldn't go any smaller than a 14cm2 turbine housing.

My fathers truck has that 9cm2 turbo and its funny how small it is compared to the compressor housing. It works ok on a cummins because they can handle the higher drive pressures.

 

[THEFERMANATOR]

I had NO trouble with my 6.5 stalling the factory converter up to around 1700-1800, so I would say they are pretty close. Personally I would look for the torque multiplication more so than stall speed. GM liked using 1:1-1.5:1 converters and they just are not good for getting a load moving(but they ARE cheap to build).

 

[6.2 turbo]

I had a custom low stall built,it was horrible from a dead stop, but once moving it was awesome.

 

[6.2 turbo]

Just remembered that the tight converter was fine with the 6.5,around 1500 rpm stall. When I swapped to the 6.2,it didn't have enough torque off idle to stall past 1200 rpms. If you want torque down low build a 6.5 with small precups,just don't rev it too high. A 6.2 with small precups,low end is not to bad,but a 6.2 with big cups,low end is gone. Boost will bring it back but still not quite the same.

 

[brownpaden]

so if im reading this all correctly, with me putting this 6.2 flywheel on my 6.5 and bolting it up to the origional gasser tc and 700r4 i should have a decent stall or am i backwards??

 

[WarWagon]

so if im reading this all correctly, with me putting this 6.2 flywheel on my 6.5 and bolting it up to the origional gasser tc and 700r4 i should have a decent stall or am i backwards??

You have about double the torque of a gas engine with a diesel and the same HP. So a gas engine converter used on a diesel will stall higher than it did on a gas engine. As the gas converter does not have brazed elements the diesel will rattle it apart. In HD gas applications the stall speed can be the same as the diesel should be, brazing I am not sure of.