My Cummins 6BT Story

scottryana

 
 
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Feb 2, 2004
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What’s your plan for a trans? I am about where you are. Around 490ft/lbs on the dyno. Gas ft/lbs not diesel so @3600-3700, and I am very leary about doing much more. I haven’t had any trans issues and everything feels as strong as the day I did the shift kit but we are asking a lot of these little transmissions! Lol
 
Joined
Dec 1, 2004
Messages
159
What’s your plan for a trans? I am about where you are. Around 490ft/lbs on the dyno. Gas ft/lbs not diesel so @3600-3700, and I am very leary about doing much more. I haven’t had any trans issues and everything feels as strong as the day I did the shift kit but we are asking a lot of these little transmissions! Lol
Have quite a few miles on the setup now... On a cool day, the TC Lock can't hold until the trans temps are up a bit. The shifts are always consistent. Trans is pretty fresh on the rebuild. As long as I allow the trans to warm up before feeding it the beans, I haven't really worried about it and probably won't.

I will say that I've been detuning this setup over the last year or two rather than adding power to it. My boost is in that dyno pull is only 28 PSI, which is down from 45 or so at the peak in the past with it. I'm a bit "over it" as it relates to pumping hp into the 80. As it is, I have no issue cruising 80-85 and it even achieves decent fuel economy. The worst I get is 11 and the best I get is 16 or so. For this application, I figure that's Ok. Since I'm always hauling my little guy to the rock crawling park in it, the last thing I need is for it break down due to my heavy foot---further limiting my desires to push the hp/tq values beyond where they are now.

-Phil
 

Mr Cimarron

DRIVE, BREAK, FIX, REPEAT
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45! Is that sustained? I hit 20-25 regularly when passing. I used to drive conservatively and got way better mileage by keeping boost no higher than 16-18 and didn’t rev the motor as much. I shift around 2,800 because I like having it drop back in down at 1,800.
I have been thinking of going back to stock fuel plate to see if I can get some mileage back.
 
Joined
Dec 1, 2004
Messages
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45! Is that sustained? I hit 20-25 regularly when passing. I used to drive conservatively and got way better mileage by keeping boost no higher than 16-18 and didn’t rev the motor as much. I shift around 2,800 because I like having it drop back in down at 1,800.
I have been thinking of going back to stock fuel plate to see if I can get some mileage back.
On the 45psi, I was pretty arrogant with boost for a while. I'd let it run 45psi to get up to highway speed and then let things cool back down. As you imply, that was never a place to just sit there and leave it for too long.

I tend to cruise at 10-12 and then probably average 20psi to "pass"... If I lean into it much, it will go up to the wastegate's 28psi.

The problem with the stock trans and even the 3:54 gears I have, I'm revving a bit too high pretty much all the time since OD isn't all that much overdriven! lol.

If there was some way to get a 12-1400 RPM stall converter for this rig, it would be truly transformative. The loose TC sucks up power like its going out of style. I called a few shops with a "there's no price I won't pay" type of dialogue to get a uber low stall converter built and was basically left talking to myself...

-Phil
 
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483
Have you talked to RoadRunner in, I believe, Arizona? They recommend 1600 or so for the Isuzu’s, but didn’t seem to have a problem going lower for Cummins.
 
Joined
Dec 1, 2004
Messages
159
Have you talked to RoadRunner in, I believe, Arizona? They recommend 1600 or so for the Isuzu’s, but didn’t seem to have a problem going lower for Cummins.
I have not, although I'd bet dollars to dog biscuits they won't touch the toyota TC. I'll send them an email though!

Thanks!
 
Joined
Dec 1, 2004
Messages
159
Definitely do. They’ve done multiple A442 and I assume A343 TC’s.
Well if that's the case, I owe you one! Have not ran into them yet, but I know a certain someone local to me that would be up for a low stall 343 TC as well!
 
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Have quite a few miles on the setup now... On a cool day, the TC Lock can't hold until the trans temps are up a bit. The shifts are always consistent. Trans is pretty fresh on the rebuild. As long as I allow the trans to warm up before feeding it the beans, I haven't really worried about it and probably won't.

I will say that I've been detuning this setup over the last year or two rather than adding power to it. My boost is in that dyno pull is only 28 PSI, which is down from 45 or so at the peak in the past with it. I'm a bit "over it" as it relates to pumping hp into the 80. As it is, I have no issue cruising 80-85 and it even achieves decent fuel economy. The worst I get is 11 and the best I get is 16 or so. For this application, I figure that's Ok. Since I'm always hauling my little guy to the rock crawling park in it, the last thing I need is for it break down due to my heavy foot---further limiting my desires to push the hp/tq values beyond where they are now.

-Phil

I
 
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Hmmmm, I have been getting 19-23 mpg, I think you may have a bad TC, I am using a Microsquirt and it is a been better than the Compushift , I wonder what TC do you have, I am not sure when it was changed to the style I am running now. Mine had a new component where a new backing plate for it, to bolt to a dodge flex plate and is tuned with a lower stall speed than stock by a TC shop

This one was built by Duiser after Joel and before Dustin took it back over so who knows. based on how it drives id say TC has not been opened up.

My conversion has had both. First was lowered by Dacco. Second was stock after my flex plate went it damaged the modified torque converter. Had a used one locally I through in to get it back on the road. Last spring. It does drive different but no change in MPG. 7-80% of the time the TC is locked up where stall has no effect. But for drivability on and off road a lower stall would be ideal. Working with roadrunner now. They claim to have a HD lockup. Which would be nice. We’ve pushed that lock up hard and shutters a hair occasionally.
 
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I get 19-23 in mine, I would look at getting modified TC, you are getting bad mileage, due to a incorrect stall speed send me a PM and I'll ask the shop what and if the could redo yours, I am not sure if they can due to the slug/backing plate we make for them now
“We”. Finally admitting your part of the operation. Now wonder your info doesn’t line up with any one else’s real life experiences.
 
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This one was built by Duiser after Joel and before Dustin took it back over so who knows. based on how it drives id say TC has not been opened up.

My conversion has had both. First was lowered by Dacco. Second was stock after my flex plate went it damaged the modified torque converter. Had a used one locally I through in to get it back on the road. Last spring. It does drive different but no change in MPG. 7-80% of the time the TC is locked up where stall has no effect. But for drivability on and off road a lower stall would be ideal. Working with roadrunner now. They claim to have a HD lockup. Which would be nice. We’ve pushed that lock up hard and shutters a hair occasionally.
I
 
Last edited:
Joined
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I am using a completely different TC and stand alone, I was the first one to get the Micro squirt which seams to work out better than the Compushift, I could ask the guy's who do the torque converters for swaps and let you know, if they could do your's, if they can I will give you the info and let you deal with them, if you would like
Please give info on your torque converter. Just modified or custom new? Please expand.

Turbophil has the compushift I’m running PCS TCM. Gives a lot more detailed adjustment probably like your micro squirt
 
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