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Old 03-25-2019, 08:46 PM   #1
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Join Date: Mar 2019
Posts: 10
1999 T444E, school bus version of the 7.3, Power Increase

I'm converting my 33` flat nose rear engine school bus.

To get to highway cruising of 60mph and 2000 RPM, I'm having my 5.11 rear end changed to a 4.10 (Allison dealer did the calculations).

To make up for some of the loss in gradabilty (pulling hills) I want to see what simple to moderate engine upgrades could be made to give me increased horsepower.

My engine is currently at 230hp, and the MT643 can easily handle 250hp.

Any suggestions are appreciated.

Here are the main differences between the engines:

Both engines feature the same basic specifications; the long blocks are identical between both engines. The 7.3L Power Stroke is a T444E save for the following differences:

The PCM's (Powertrain control module) are different, thus the different power ratings offered between the 2 engines. For example, the T444E was offered in ratings up to 620 lb-ft torque, where as the Power Stroke was only offered with peak torque reaching 525 lb-ft. However, you may also notice that the 275 HP rating of the Power Stroke is much higher than any HP rating of the T444E.

Accessory drive and various engine sensors

Turbocharger design

Water pump design

The T444E block is painted blue

T444E uses a mechanical fuel pump, requiring a different camshaft

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Old 03-27-2019, 04:26 PM   #2
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Join Date: Aug 2017
Location: DeLand, FL
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This site sees little activity about the Power stroke engine. Try this site. More activity.

Rockwood 2604WS
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Old 03-27-2019, 04:54 PM   #3
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Your gradability will stay the same, the transmission will be in a different gear. I would get rid of that 643 and put in a six speed Allison. Those 643 were never popular with the truckers because not enough gears and too big a jump between gears. Also if memory serves me right the 643 doesn't have locking convertor unless they have been changed since I quit selling HD Trucks.
Bill And Jeanne Anglin, Eagle River, Alaska.
1999 Dutch Star 3884, Freightliner, Cat 300, Jeep Liberty Toad.
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Old 04-04-2019, 02:30 PM   #4
Join Date: Apr 2018
Posts: 74
I am very familiar with the PSD. I suppose it comes down to what you want to sped. If that T444E has the same internals as the PSD (Rods mostly) then that is a great year, and has forged rods.

That being said, and beyond what has been mentioned, I would start with intake and tunes. I am sure someone provides tunes for that PCM, if not, DP Tuner, PHP, etc should be able to do custom tunes. Some of those guys will even go on a drive with you to tune to your driving style.

Beyond that, it starts getting expensive. Next would be higher flow injectors and an electric fuel pump. Tune required to utilize the capacity of the injectors. Since you have the manual fuel pump, you may have a regulated return with is good.

I am guessing the exhaust is restriction free, if not you may want to look into that.
2006 22' RVision Trail Cruiser Lite
No truck yet...
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Old 04-10-2019, 12:34 PM   #5
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T444E vs PSD

Hi, and thanks for your input about the tuning. I'm waiting to get the rear end swapped out before I do anything. I want to see how it performs first.

I agree it's best to start simple and expand as necessary.

Per the T444E guts, it's my understanding most of the internals are exactly the same. There are a few externals, like the turbo and such that are different.

I think I'll change the key sensors and possibly add new injectors at the first sign of issues, but until then, waiting for the rear end to get done.

Any input you can provide about the difference in injectors, things to look for, and look out for, would be appreciated.

I know the oil system is a huge part of performance and I plan on checking all of that when I change out the oil. I'm pretty sure I'm going synthetic.

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Old 04-11-2019, 11:31 AM   #6
Join Date: Apr 2018
Posts: 74
I forgot about the HPOP (High Pressure Oil Pump), depending which one you have, after upgrading injectors, should you choose to do so, you may want an upgraded pump. It isnt required, and I think you can do stage 1 injectors just fine, stage 2+ may required an upgraded HPOP. It's been a few years since I've been in the scene.

I would head over to powerstroke.org and read up on injectors. There are places to avoid, and places for safe purchase. IIRC, whenever possible, buy new stage injectors. There is a lot of info over there on those. Im not sure what turbo currently sits in your bus, and what its limits are, just something to research.

You can also do tunes on stock parts, free up some performance as well. That would be a cheap one to try. You can always have it re-tuned, plus a 'stock' setting to get you rolling if you make changes and need to wait on new tune files.

So, you are on the right path starting where you are to see what it will do. What transmission does it have? You'll want to be absolutely sure to keep that fluid temp in check, its the death of the 4R100 and its relatives.

Fuel pump (depending on which you go with)

High flow fuel pump
Transmission upgrades

2006 22' RVision Trail Cruiser Lite
No truck yet...
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1999, power

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