High stall converters with large turbo.

[WarWagon]

It is time to take a new direction in 6.5 performance. Conventional thinking is a diesel has lots of torque in the low end so if you ever do a converter it should be tighter than factory. This would be true if I had the factory turbo spooling up in the bottom end. I already know the factory setup sucks as the auto trans shifts you to high RPM where the small turbo chokes. Conventional thinking does not apply to the underpowered 6.5 vs. other diesels anyway.

On a brake stand I get 1600 RPM with my setup. It is sluggish with the AC on, cooling fan load, and high outside temps. Once the RPM gets up it really takes off. Even the 1993 suffers from this some from a dead stop.

http://www.thetruckstop.us/forum/showthread.php?39789-ATT-videos

So at this point with a trans overhaul needed it is time to let the engine slip up to the higher RPM with a high stall converter. When it gets to the higher RPM locking the TCC at WOT to load the engine is part of the plan usually starting in 2nd or 3rd gear. The TCC lock should keep the MPG in line with the higher stall. It is possible getting up to speed may improve MPG via less smoke. I figure 500-1000 RPM over stock stall should get me in the ballpark.

 

[THEFERMANATOR]

You don't neccesarily need a looser converter so much as you need one with a better torque multiplication to it. Also you need a converter with better coupling once it does engage. I went to a tighter converter on my LB7 when I did my swap, and it spools twice as quick as it did before. A properly designed converter will couple harder once it catches, but can be looser down low to aid in spool up. Also you need to make sure your converter is set-up to load the engine while still allowing it to get up in RPM's. If you don't get enough load, then your turbo won't light off.

 

[sshewins]

So which brands might make the cut? TCI? Art Carr?

 

[WarWagon]

Talking with Yank Performance Converters out of Nevada now. ( www.converter.cc ) They are taking a gas 4L80E core then stalling it ~500 RPM higher and triple disk clutch with billet cover and all the usual goodies they do to one. A smaller diameter converter was ruled out.

 

[THEFERMANATOR]

PRECISION INDUSTRIES out of Tennessee would be highly recommended by me, but then again I'm prejudiced as I have one. they can build one for an ALLISON and make it work in front of the 4L80E as they are similar. For an off the shelf unit the TRANSTAR billet piston model is a good choice.

 

[6.2 turbo]

I ran a junkyard 350 gas converter. It stalled 2500 rpms behind my 6.2. I loved it ,perfect for the 6.2,not so perfect for a 6.5 though. Keep in mind that injection timing makes a huge difference in converter stall. Retard for more stall and low end torque,at the cost of less top end power and higher egt's.

 

[THEFERMANATOR]

I ran a junkyard 350 gas converter. It stalled 2500 rpms behind my 6.2. I loved it ,perfect for the 6.2,not so perfect for a 6.5 though. Keep in mind that injection timing makes a huge difference in converter stall. Retard for more stall and low end torque,at the cost of less top end power and higher egt's.

With a DS4 pump you can have the best of both worlds with a custom tune.

 

[Jorge6.5]

PRECISION INDUSTRIES out of Tennessee would be highly recommended by me, but then again I'm prejudiced as I have one. they can build one for an ALLISON and make it work in front of the 4L80E as they are similar. For an off the shelf unit the TRANSTAR billet piston model is a good choice.

I run the Transtar billet piston torgue conver with stock stall speed and I love it, it performs good

 

[THEFERMANATOR]

I run the Transtar billet piston torgue conver with stock stall speed and I love it, it performs good

TRANSTAR has MUCH better torque multiplication than GM's, and therefore lights the turbo off better. I believe I was one of the ones that talked you into using there converter.

 

[Jorge6.5]

TRANSTAR has MUCH better torque multiplication than GM's, and therefore lights the turbo off better. I believe I was one of the ones that talked you into using there converter.

Yes your right, I'm really glad I took your advice

 

[tanman_2006]

Hmm, I might have to try a precision converter in my 00 dually after it gets its new engine. They sound ok and if ferms burb can twist its chassis and not kill the converter then it cant be all bad. I might wait until Warwagon beats on one for awhile, their 5yr warrenty sounds right up his alley!

 

[dixiepc]

Explain to me why these torque converters are better. I'm very familiar with engines and transmissions but torque converters have always been a mystery to me.

 

[WarWagon]

Not "better" in any way most people would care about. Sure a triple disk clutch and other improvements make it better, but, I am after the higher stall speed to light off the turbo and reduce the sluggishness and reduce amount of smoke on starts. This is specific to this 6.2 engine. My 1993 would also benefit some, but, not as much from a higher stall because the engine and rear end gearing are different.

A torque converter is like a automatic clutch and transmission all in one. If you look at a dyno run I did You can hear the tires scream when I floor it. This is because the factory converter takes the 400 ft lb TQ the engine has and multiplies it giving me over 1000 ft lbs at the rear wheels including gearing in the transmission and rear end. It would be at a lower RPM as the engine is spinning 1800 RPM or so faster than the transmission input shaft. The RPM difference is what multiplies the torque in the torque converter.

When we get up to speed we don't need as much torque so we lock the torque converter clutch up to gain MPG and reduce trans heat. The other benefit of a converter is not having to slip the clutch to get moving like a Manual trans.

The torque multiplication and ability to get 1800 RPM instantly at a stop light when you floor it puts the engine near it's peak torque and a good ways up the HP curve. It also provides a lot of torque like a deep granny gear. But you don't have to row though 12+ gears that the converter is providing. Sure it generates heat and eats some fuel to do this over a manual trans.

In the specific case of my 1995 with the 6.2 small precup engine. I am brake stalling at 1600 RPM and having a hard time getting the rig moving from a stop. When the engine gets near 2000 RPM the turbo's light and it takes off. So a higher stall converter lets the engine stall at a higher RPM where more power is available ideally 2000 RPM stall. Specifically from letting the turbo's light off with enough engine RPM. Outside air temp, cooling fan, and AC compressor are all using power that reduces the stall speed and takes longer to get enough RPM to light off the turbo setup. So if I let the engine "slip" up to the 2000 RPM range I should get a quick launch vs the sluggish 1600 RPM stall I get now. The trick as said above is not to make it too loose where there isn't enough load to light off the turbo.

Link provided to answer question better only.
http://www.converter.cc/FAQ_s/45.htm

 

[dixiepc]

Alright, so help me out here. I've got a 1989 J-code motor out of a 1-ton with an ATS turbo setup on it. The turbo has a .96 A/R turbine housing on it. I'm putting this in a 1984 Chevy 4x4 1/2 ton pickup that is a gasser now. The truck has 4.56 gears with true 35" tires and a 700R4 transmission. Now I know that there are better transmissions but I'm not out for power just economy.

Now my question is should I retain the T/C that's behind the gasser, with it's higher stall, or should I use a diesel T/C? Keep in mind that this turbo was probably designed to be used with a 3 speed transmission, so the rpm's would already be higher than mine with the overdrive transmission.

Or should I try to find a .81 A/R turbine housing?

 

[WarWagon]

Change the precups to the larger 6.5 turbo precups.

 

[dixiepc]

I'm hoping to be making 10 to 12 psi at the very most so I think that the j-code precups will be alright. They are some bigger than the c-code precups that these turbos were made for. Mind you that I'm only after economy, the turbo is only to help in the mountains and to give me a little more power for dealing with traffic.

 

[sshewins]

Where can one obtain a Transtar T/C?

 

[sshewins]

Where can one obtain a Transtar T/C?

Never mind, I just googled them. Appears there is a dealer in Addison, which is fairly close to me.

Jorge, what model did you get? Was is the GM 81 BP? Description of the T/C says it has 1800-2000 stall.

Ferminator, I can't tell from catalog if there is any other difference other than the billet part. Same stall, spline, height, etc.. Is it really worth whatever price diff over stock clutch piston?

 

[WarWagon]

I'm hoping to be making 10 to 12 psi at the very most so I think that the j-code precups will be alright. They are some bigger than the c-code precups that these turbos were made for. Mind you that I'm only after economy, the turbo is only to help in the mountains and to give me a little more power for dealing with traffic.

I didn't give precups a second thought either. The turbos were designed to go on the engines as they came from the factory. Not ideal, but, run. They smoke even with the Banks turbo. The Military 1986 emissions exempt precups I have are bigger than the 6.2 NA precups. They work ok with the small GMx turbo. Go bigger turbo and more fuel and they smoke like hell. I hate them as they hold me back. They are not hard to change while you have the engine out. No one knew this would be an issue at the time as it is a forgotten art. You can get in touch with Dennis/Slim Shady who makes the ATT kits and he can get the precups machined out rather than buying different ones.

The small precups are why I got the BD valve. Now due to the trans coolant issue I am getting a higher stall. If that doesn't work the engine is coming out for bigger precups. It doesn't run that great vs. the 1993 with 6.5 NA precups. The 6.5 NA is as small as you would want to get away with unless you are NA. Maybe it gives me an edge in town as I get 13 MPG on the 1993 and 10 MPG on the Dmax.

Military 6.2 head on the left, 6.5 NA head on the right and 1995 turbo precups sitting on the head.

 

[THEFERMANATOR]

Where can one obtain a Transtar T/C?

Never mind, I just googled them. Appears there is a dealer in Addison, which is fairly close to me.

Jorge, what model did you get? Was is the GM 81 BP? Description of the T/C says it has 1800-2000 stall.

Ferminator, I can't tell from catalog if there is any other difference other than the billet part. Same stall, spline, height, etc.. Is it really worth whatever price diff over stock clutch piston?

I believe it is only a few dollars more for the billet piston VS a stock cast piston. Haven't looked in awhile, but it used to be around $300-350 for the billet piston model VS the $250-300 for a stocker.