Torque Screw Adjustment
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Cargo Master
Joined: Dec 2010
Posts: 2,123
Likes: 5
From: Fort Worth, TX
Torque Screw Adjustment
Hello all,
I have another thread with my failed IP and injector installation and since I have a specific question, I figured I would ask it separately.
Which direction do I turn the torque screw to REDUCE the fuel at low RPM?
I have a NA 7.3 but my newly purchased U-haul pump has a torque screw. I am getting smoke under light acceleration and any time there is a load put on the engine be it an upshift or O/D. The smoke is not pitch black but more like a brown color.
Timing is set to 9 degrees BTDC using the pulse method.
My fuel screw is turned down 1-1.5 flats. Before it smoked even more. 4 flats was too much and I had no power, so I bumped the screw back up.
The truck never smoked with the old pump, so I am not sure how much is normal with a new pump and new BB codes.
I have another thread with my failed IP and injector installation and since I have a specific question, I figured I would ask it separately.
Which direction do I turn the torque screw to REDUCE the fuel at low RPM?
I have a NA 7.3 but my newly purchased U-haul pump has a torque screw. I am getting smoke under light acceleration and any time there is a load put on the engine be it an upshift or O/D. The smoke is not pitch black but more like a brown color.
Timing is set to 9 degrees BTDC using the pulse method.
My fuel screw is turned down 1-1.5 flats. Before it smoked even more. 4 flats was too much and I had no power, so I bumped the screw back up.
The truck never smoked with the old pump, so I am not sure how much is normal with a new pump and new BB codes.
Thread Starter
|
Cargo Master
Joined: Dec 2010
Posts: 2,123
Likes: 5
From: Fort Worth, TX
There is this video but I don't understand what he is saying.
‪Torque Screw Adjustment‬‏ - YouTube
‪Torque Screw Adjustment‬‏ - YouTube
Fleet Owner
Joined: Jul 2006
Posts: 20,389
Likes: 849
From: Mi'kma'ki
The torque screw was only on the DB2-50XX IP's, 1992.5 and later trucks.
The engines should also run a serpentine belt.
The torque screw limits the amount of fuel delivered to the engine at low RPM's to help clean up the exhaust.
It does nothing to change the max fuel delivered, only the low RPM fuel delivery.
On a non turbo engine, most likely the only result from adjusting it will be increased smoke and higher EGT's.
On a turbo engine, it can help with low RPM turbo spooling and power.
Using both the max fuel screw and the torque screw together on a turbo engine will help with power across the RPM band.
Set the max fuel screw so the engine produces a light black haze at high RPM, in is more fuel.
Once you have that set, you can adjust the torque screw so you have the same light haze at lower RPM's.
On the torque screw out delivers more fuel at lower RPM, in decreases the fuel delivery at low RPM.
As with any IP adjustment, you should have a pyrometer installed before you adjust the fuel, high EGT's can damage the pistons.
Also the torque screw is set at about a 45 degree angle in relation to the IP drive shaft on the rear of the IP.
There is another screw that may have a cap on it, or a seal wire that is parallel with the IP drive shaft.
That screw holds internal IP parts in place and should not be adjusted.
IP damage would be the result.
The engines should also run a serpentine belt.
The torque screw limits the amount of fuel delivered to the engine at low RPM's to help clean up the exhaust.
It does nothing to change the max fuel delivered, only the low RPM fuel delivery.
On a non turbo engine, most likely the only result from adjusting it will be increased smoke and higher EGT's.
On a turbo engine, it can help with low RPM turbo spooling and power.
Using both the max fuel screw and the torque screw together on a turbo engine will help with power across the RPM band.
Set the max fuel screw so the engine produces a light black haze at high RPM, in is more fuel.
Once you have that set, you can adjust the torque screw so you have the same light haze at lower RPM's.
On the torque screw out delivers more fuel at lower RPM, in decreases the fuel delivery at low RPM.
As with any IP adjustment, you should have a pyrometer installed before you adjust the fuel, high EGT's can damage the pistons.
Also the torque screw is set at about a 45 degree angle in relation to the IP drive shaft on the rear of the IP.
There is another screw that may have a cap on it, or a seal wire that is parallel with the IP drive shaft.
That screw holds internal IP parts in place and should not be adjusted.
IP damage would be the result.
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