stall speed with compound turbos

[scotzilla]

I dont have much time to figure this out. Heres what ive got going on. Just finished a compound turbo 12 valve swap into my 96 ford f350 cclb. 3.55 gears 37 x12.5 tires. I plan on doing gears asap. The turbos are the towing kit from diesel power source. Im still running the ford E40d trans with a precision converter with all the bells and whistles and a 2500 stall. I told them what i was doing and they recommend that stall to get the turbos lit and keep smoke to a minimum before the truck started moving forward.

THe local dodge specialist is saying they usually run a 1100 or so stall for my application. I want to tow a 16k lb trailer and have cool egts and trans temps. THe truck has been together for a few weeks and the converter is heating up and rattling when its locked up. The trans isnt getting hot but the paint is burnt in two spots on the converter. I have a feeling its all coming back apart and I wanted some input on what stall you guys would recommend. My sled pulling friends are saying stick with the 2200-2500 range and the cummins gurus are saying 1100-1500. What do you guys think and why

[mathews8pt]

Holy crap, 2500 stall?? thats just stupid. Stock stall is around 2k rpm.

What size is the secondary in the twins? im assuming its fairly small due to them being towing twins.

When the tc is locked and you are running down the highway at what rpm can you build 10psi by?

[Drothgeb]

If you have the 62/65/12 over a 475 1.32, then you've got the same turbos as me. With 7x12s and 5x16s, the 1800-2000 works really well. Even if you injectors are smaller, I'd probably go the same route. Remember, that's the maximum stall speed and varies a little with your hp.

I recently put in some 5x18s. Due to them needing more air to clean up, and for easier spooling off the line, I'm probably going to switch to a 2000-2200, which is more or less stock. That's about as high as you go for on the street, anything higher is normally for pulling or racing.

[scotzilla]

those are the same turbos and i have the ddp 4s on there. Im still getting all the bugs worked out of the pcs trans controller but the truck pulls twice as hard with the converter locked up in third or fourth than it does unlocked and flashing at 2500. About 70mph 4th gear with the converter locked up there is almost no lag at around 1900 rpm, it smokes for a fraction of a second, black smoke turns to brown as soon as the turbo lights and its out. If i unlock the converter it flashs and makes the boost but doesnt accelorate as fast

[mathews8pt]

I would get a 200 under stock stall if it was my truck.

[86burbguy]

My Goerend triple disk stalls to around 1700 and let's truck get moving quickly by 2000. For towing applications I would think a lower is better. These 12v make rediculus torque at low rpms, seem a shame to blow right past it with a 2500 stall on a engine spends most of time around 2000.

Pulling trucks turn 5000 rpms and run alot of timing to make power at high rpms. They need the high stall to get them strait up to rpms where those trucks make their best power.
Most street/ work trucks will never see 3500 rpms and make peak torque near 2000 rpms.

Make sense to me that you would want a stall as close to peak torque as possible.

[scotzilla]

yea well i can thank precision for there excellent opinion on a converter.

[Drothgeb]

If you run average tires 1800 would be good. If you're going to run 37s, give 2000 some thought.

Just remember... If you get it a touch high, you can always lock it up. If you get it too low, you'll end up swapping it out.

[scotzilla]

talked with precision today- 2500 was a mistake. They are offering to change it out, just sucks i have to pull the trans- but at least they are taking care of me. So im hearing 1700- 2000 as suggestions? Terry at precision recommended 2000 because of the 37's and twins