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Detroit 12.7 pulling ability?
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ND_farmer
Posted 12/2/2009 23:49 (#947646)
Subject: Detroit 12.7 pulling ability?


SW North Dakota
Ok we bought a 2000 daycab freightliner semi with a 12.7 detroit 430/500hp and 530000 miles. I used alot of your guys input on this site (with the search option) in my decicion to go with the detroit so I know its a good motor. I got a chance to get behind the wheel yesterday with a 80,000lb load. It really doesnt feel like the truck makes the kind of hp the engine tag shows. It slows down from 65 to 55 on long hills and doesnt have much for torque.(which i read is common) This thing is a dog until around 1400 rpm then it just pulls great. I am curious to why it doesnt hold its own on the road though. The rpm is 1500-1600 when at cruising speed so I would think it is right in the powerband. We have two tandem axle trucks. One with a 350hp 3406(610K miles) and the other a 400hp cummins and they only slow down when u let off the gas. Granted they only haul about 60000 fully loaded. This is our first semi with trailer so maybe its completely acceptable. Do most peoples semis pull down climbing longer hills? I was reading on this site that the 430/500 means 430hp on the pedal and 500hp with the cruise set. Is this correct? And can the motor be set up different to pull better? Thanks alot!!
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Ernie
Posted 12/2/2009 23:56 (#947653 - in reply to #947646)
Subject: If it is a series 60



North End I-15
A trip to the shop where they can set the computer will amaze you . Most trucking companies restrict the speed and rpm with the computers .
Neighbor spent a few $ on his . Whole different truck after a trip to the computer.
Also @ those miles it is real cheap insurance to roll out the mains and rod bearings . I think neighbor paid about $2000 for the roll out and computer set up .

Edited by Ernie 12/2/2009 23:58
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kstate90
Posted 12/3/2009 00:00 (#947657 - in reply to #947646)
Subject: Re: Detroit 12.7 pulling ability?



North Central Kansas
What transmission and gear ratio? I have a 2003 daycab Freightliner with the same engine. Fuller 10spd with a 3.90 rear end. Mine has about 700,000 miles on it. Mine will run 65 if you want to. We run on mostly county blacktops and keep it in the 55mph range. The other guy I cut with has a 1998 with a 12.7 but with less hp and 4.10 ratio with a 10 spd. Can't remember what his tag says on it. My turbo really whistles compared to his. As far as pulling the hills they are going to pull down some. Are you downshifting any or trying to make it pull over without shifting?

Edited by kstate90 12/3/2009 00:01
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eddiedry
Posted 12/3/2009 00:08 (#947668 - in reply to #947646)
Subject: Re: Detroit 12.7 pulling ability?



Wheatley, Arkansas
A 2000 FL would I assume have a 1550 torque engine, the 430/500 could be set up several ways in the ECM, from a low of 370 to a high of 500 with various split hp settings. Does this truck have a boost guage? If it does what kind of boost are you getting? Is your engine a 1800 or 2100 RPM engine? If your other trucks don't pull down, even with the lighter loads, this one shouldn't either. I would check the fuel filters, ECM setting and air to air first. We had one with a leak in the intake manifold gasket that took forever to find, it ran fine just wouldn't pull good. It has been my experience that all Detroit 12.7 have a weak assometer but normally pull pretty good. The torque peak on this engine is 1200 RPM, but you should see the boost run up to around 25-28 psi at @1700 RPMs on a hard pull.
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eddiedry
Posted 12/3/2009 00:10 (#947670 - in reply to #947657)
Subject: Re: Detroit 12.7 pulling ability?



Wheatley, Arkansas
On a 12.7 he doesn't need to downshift until @1200 RPM's, that's when they pull their best!
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red raider
Posted 12/3/2009 00:26 (#947683 - in reply to #947668)
Subject: Re: Detroit 12.7 pulling ability?


Victoria TX
I think the torque is limited to the foot pounds that the transmission is rated for. You won't get the torque you experience with an older truck that does not have a computer. I think your transmission might be light like mine so they limit the torque no matter what the hp is set at. 12509 transmission = 1250 torque limit 9 speed , 14509=1450 torque limit 9 speed and so on ( I think)
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Rich
Posted 12/3/2009 00:29 (#947685 - in reply to #947683)
Subject: Re: Detroit 12.7 pulling ability?



Kansas
All 12.7's no matter the age had the DDEEC system on them.

I know of none that arn't computer controlled.
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Orin
Posted 12/3/2009 00:37 (#947697 - in reply to #947685)
Subject: Re: Detroit 12.7 pulling ability?



Nusbaum Farms LLC Bellfountain, OR
Rich - 12/2/2009 21:29

All 12.7's no matter the age had the DDEEC system on them.

I know of none that arn't computer controlled.


You're right, there's no such critter.

-Orin
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red raider
Posted 12/3/2009 01:03 (#947714 - in reply to #947646)
Subject: Re: Detroit 12.7 pulling ability?


Victoria TX
Are you replying to my post? Doesn't the computer limit the torque by the rpm/fuel
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ND_farmer
Posted 12/3/2009 01:27 (#947728 - in reply to #947646)
Subject: RE: Detroit 12.7 pulling ability?


SW North Dakota
The trans is a eaton 10 speed and the rear is 3.90. It tops out at 72 at around 1600 rpm. I dont think it runs up to 2100. It doesnt have a boost guage but I would like to add one.
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hillfarmer
Posted 12/3/2009 03:57 (#947764 - in reply to #947728)
Subject: RE: Detroit 12.7 pulling ability?



I'm thinking peak torque is like 1250 to 1300

so three is not much at 1700

there should be a waste gate on the 500 hp turbo's

maybe it is opening up and dumping boost
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Fla Veggie Farmer
Posted 12/3/2009 07:45 (#947839 - in reply to #947646)
Subject: RE: Detroit 12.7 pulling ability?


Southeast Florida
The computer is limited by the previous owner. I have that same engine in my truck and it will get you a speeding ticket you don't want to see. It tops out at 1900 and it's a bear. Our other truck is identical; mine will walk off and leave it. Now granted it's nothing compared to the 2003 KW T-800, C-16 CAT @ 660 HP I had in FL to haul heavy loads. That truck could carry a 345C L track hoe with the cruise set at 75 mph in rolling hills on I-10 from New Orleans to WPB.
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salexmo
Posted 12/3/2009 08:18 (#947870 - in reply to #947839)
Subject: Re: Detroit 12.7 pulling ability?



northwest missouri
I have a 12.7 that is tagged at 430/500 - detroit shop confirmed that was 430 w/ cruise off and 500 w/ cruise engaged, had it changed to 500 all the time and set governed speed from 64 to 75. Would have to look at truck but I think the torque on mine is set @ 1650.
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kstate90
Posted 12/3/2009 08:23 (#947879 - in reply to #947646)
Subject: Re: Detroit 12.7 pulling ability?



North Central Kansas
If it was a delivery truck most likely the computer is set up to keep the driver from doing something stupid. Mine was set up to shut off after 5 minutes. Had it reprogrammed.
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eddiedry
Posted 12/3/2009 09:40 (#947992 - in reply to #947870)
Subject: Re: Detroit 12.7 pulling ability?



Wheatley, Arkansas
Large car? Most are 1650, most Freight shakers are 1550.
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milofarmer1
Posted 12/3/2009 15:08 (#948334 - in reply to #947646)
Subject: Re: Detroit 12.7 pulling ability?



Farwell, TX/Pleasant Hill, NM
No replacement for displacement. Cummins 14L, 3406 Cat 14.6L, Detroit 12.7L. Even with the same engine specs. it just isn't going to FEEL the same as the bigger engines.
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combine ken
Posted 12/3/2009 16:19 (#948398 - in reply to #947646)
Subject: RE: Detroit 12.7 pulling ability?


southern Alberta
Ive had all 3 makes of engines in trucks at the same time. Pulling identical loads, on the same road, one behind the other they would all run about the same for power. truck #1 has a C 15 Cat, 475hp with 3.90 rears and 18 spd, #2 N 14 Cummins, 500 hp with 3.90 and 18 spd, #3 series 60, 450hp ,but played with, 4.11 rears and a 15 overdrive. The Cat will walk away from a rolling corner better, bigger engine displacement. The Detroit does not get driven under 1450 rpm or it will lose ground quickly. If we run it between 1450 and 1900 RPM it will keep up easily. For us an 18 spd would really help this unit. The seat feel is dead on the Detroit, you would swear it is the dog of the group. But it pulls as well as the others, once up to speed. However it will beat them all at the fuel pump by about 1/2-3/4 of a mpg, so that works for me. As Ernie suggested run it to a Detroit shop and have them plug it in to read your settings. They can do a lot of stuff with that computer. It should have the variable pitch turbo, you can get more boost/power by playing with the spring tension.
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Canfarmer
Posted 12/3/2009 17:20 (#948464 - in reply to #947646)
Subject: RE: Detroit 12.7 pulling ability?


We have a 430/500 in a 2002 ih eagle pulls amazing. 30psi boost is max, 4.11 rears, 13spd, either a 1450 or 1650 touque can't remember, 60mph=1600rpm, biggest load i've hauled is about 160,000 lbs and it would make 60mph with that load but totally maxed out. When accelerating with a load of this side you need to run from 1500-1800 rpm thats where she really pulls and makes the full 30psi boost.

i would say you need to plug the computer in and see how its set up.

Edited by Canfarmer 12/3/2009 17:21
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ihguy
Posted 12/4/2009 13:08 (#949734 - in reply to #948464)
Subject: Re: Detroit 12.7 pulling ability?


The DDEC system can hold up to 4 different hp settings in the ecm which can be selected only with a service tool which a dealer or dist. would have. Second your max torque range is around 1550-1650 rpms, not 1200-1400 rpms. Just like the old 2-strokes keep it wound out for better performance. Boost pressure is going to max out around 32 psi measured at the intake manifold. You need to check to see if you have a 1800 or 2100 rpm engine. Also have the check the droop setting in the ecm, they are set at 150 from the factory. Try moving the droop to 0 as it usually makes a difference. If you do not care about fuel mileage have all the injector calibration codes changed to 75, this will add about 20 rear wheel hp on a healthy motor. I know these engine very well so if you have more questions let me know. Thanks
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eddiedry
Posted 12/4/2009 15:10 (#949840 - in reply to #949734)
Subject: Re: Detroit 12.7 pulling ability?



Wheatley, Arkansas

http://www.detroitdiesel.com/Public/specs/3SA356.pdf

You must be confusing a Detroit with a CDC.

 

Better stick with ihguy and not try to be detroitguy! Maximum torque is at 1200 RPM

A 12.7 will pull better and is more  fuel efficient in the 1200-1400 RPM range! The spec sheets don't lie.

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Canfarmer
Posted 12/4/2009 18:26 (#950047 - in reply to #949840)
Subject: Re: Detroit 12.7 pulling ability?


your tach must be screwed
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eddiedry
Posted 12/4/2009 19:39 (#950161 - in reply to #950047)
Subject: Re: Detroit 12.7 pulling ability?



Wheatley, Arkansas
I guess Detroits spec sheets are screwed too huh? Did you click on the url?
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ihguy
Posted 12/9/2009 18:15 (#957737 - in reply to #950161)
Subject: Re: Detroit 12.7 pulling ability?


eddie i have built probably over 200 series 60 in my time. not trying to argue your point but when your down to 1200 rpm trying to pull a load if you go to shift your done. keep her rapped out.
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eddiedry
Posted 12/18/2009 22:23 (#973923 - in reply to #957737)
Subject: Re: Detroit 12.7 pulling ability?



Wheatley, Arkansas

when your down to 1200 rpm trying to pull a load if you go to shift your done.

Are you refering to downshifting when pulling a grade here? If so I say BS! If you are referring to upshifting, then yes, you would need to be in the 15-1600 RPM range to shift to the next gear.  I've not built ''probably over 200 60 series Detroits, but I have driven probably over 20, and my best fuel economy and pulling performance was running in the 12-1600 RPM range, with flat-land cruise set at @1300 RPM and @ 68 MPH. Go to the online Detroit charts that show the torque curve, torque increases dramatically from 1800 to 1200 RPM where it peaks.

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