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7.3L IDI Diesels (Not Power Strokes) Technical discussion of topics related to vehicles powered by the 7.3 Liter In-Direct Injection Navistar engines.

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Old 12-12-2012, 03:14 PM   #16 (permalink)
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Lots of info here. One more question though, if the torque screw limits the max fuel is there any rpm or time that it allows the full fuel flow when the gas pedal is floored?
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Old 12-12-2012, 05:18 PM   #17 (permalink)
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Depends on transfer pump pressure...

If transfer pump pressure is enough to overcome the restriction that the metering valve places on chamber filling, than full fueling will occur... However transfer pump pressure is RPM dependent... So in that situation, higher RPM's must be reached to overcome the TS setting...
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Old 12-12-2012, 05:40 PM   #18 (permalink)
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yea theres no massive gains on these engines without major $ and major work
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Old 12-12-2012, 09:07 PM   #19 (permalink)
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tanbuddy- the torque screw limits metering valve travel. This cuts maximum fuel back at higher rpm's only. At lower rpm's it has no affect on maximum fuel. Sounds strange but it is true. When I calibrate these pumps I first back out the torque screw, set the max fuel via roller to roller adjustment at 2800 rpm, set the guide stud for governor breakaway at 3300 rpm, then at 3150 set the torque screw to just cut the fuel back from the 2800 rpm setting. Then if I go back to 2800 rpm the fuel has not changed from my initial setting. Nor has it changed at 1400 rpm.
So backing out the torque screw will NOT increase the max fuel.
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Old 12-12-2012, 10:32 PM   #20 (permalink)
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tanbuddy- the torque screw limits metering valve travel. This cuts maximum fuel back at higher rpm's only. At lower rpm's it has no affect on maximum fuel. Sounds strange but it is true. When I calibrate these pumps I first back out the torque screw, set the max fuel via roller to roller adjustment at 2800 rpm, set the guide stud for governor breakaway at 3300 rpm, then at 3150 set the torque screw to just cut the fuel back from the 2800 rpm setting. Then if I go back to 2800 rpm the fuel has not changed from my initial setting. Nor has it changed at 1400 rpm.
So backing out the torque screw will NOT increase the max fuel.
Have you tried the same with full Roller to Roller travel? Again at stock fueling rates, its probably as you say, but when you start increasing chamber volume, the TS has more influence by restricting flow. I know that I currently have my pump adjusted to achieve full metering valve travel... Til the housing limits it, and I gained a significant amount of fuel up top... At a certain point, the metering valve becomes a restriction, but at the lower stock fuel rates, I have no doubt that the TS doesnt have an effect, the MV simply flows enough at that setting... Its good to know the exact numbers of what a stock pump does with the TS screwed in though, its even more useless than I thought it was...

My observation is that the TS is just an external adjustment of what adjusting the Gov linkage does, because you can achieve the same effect by increasing the length of the linkage itself... Maybe they did that for ease of calibration on the stand?
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Old 12-12-2012, 10:36 PM   #21 (permalink)
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yea theres no massive gains on these engines without major $ and major work
Good thing the terms "Major $ and major work" are subjective ...
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Old 12-13-2012, 01:29 AM   #22 (permalink)
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Changing the linkage length changes the governor regulation (how quickly or how slowly the governor reacts to load changes) This affects the governor operation at all speeds. The torque screw only affects higher rpm's. If you have greatly overfuelled your pump, then yes, removing the torque screw will affect fuel rates more noticeably at higher rpm's. If you are not turbocharged you then won't have enough air to burn this fuel, resulting in black smoke.
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Old 12-13-2012, 06:46 AM   #23 (permalink)
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yea theres no massive gains on these engines without major $ and major work
have you priced the upgrade parts for powerstrokes?

an IDI turbo kit and nothing else gets you into the low end of early powerstroke country.

a powerstroke can get a small bump from just a chip, but a big bump takes injectors, which cost a lot more than ours do... you can spend more on one PS injector than a full set for the IDI if you're not careful.
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Old 12-13-2012, 08:42 AM   #24 (permalink)
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Simply put the torque screw limits fuel as control by the governor. If flyweight/spring differential calls for full fuel it would limit it only to the point the full plunger adjustment can't be utilize.
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Old 12-13-2012, 10:45 AM   #25 (permalink)
 
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yea theres no massive gains on these engines without major $ and major work

Depends what you mean by massive gain.

Stock turboed truck makes like 130rwhp/300rwtq.

Trucks with the pumps I was doing and injectors have done 220-240rwhp and 430-480tq.

Thats a pretty "massive" gain for less than $1000.
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Old 12-13-2012, 05:53 PM   #26 (permalink)
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Originally Posted by Evel486 View Post
Changing the linkage length changes the governor regulation (how quickly or how slowly the governor reacts to load changes) This affects the governor operation at all speeds. The torque screw only affects higher rpm's. If you have greatly overfuelled your pump, then yes, removing the torque screw will affect fuel rates more noticeably at higher rpm's. If you are not turbocharged you then won't have enough air to burn this fuel, resulting in black smoke.
Again, the TS doesnt just effect high RPM's... Its fuel dependent... For example If Im rocking 180cc's (180mm3/stroke) WOT at 2200RPM, I guarantee you that if I turn my TS in, its going to limit my fuel (And therefore my peak Torque provided I am burning it all, which my turbo does at that RPM)... However, a 5028 pump at 65cc's, with a fully stock TS setting, might not be limited until 3100 as you say... Its all dependent on how much volume your pump is set to move.
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Old 12-13-2012, 07:56 PM   #27 (permalink)
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Depends what you mean by massive gain.

Stock turboed truck makes like 130rwhp/300rwtq.

Trucks with the pumps I was doing and injectors have done 220-240rwhp and 430-480tq.

Thats a pretty "massive" gain for less than $1000.
Really? Id like to check into one of your pumps
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Old 12-14-2012, 12:07 AM   #28 (permalink)
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RacinNdrummin- you are missing the point. 2 posters on here asked what the torque screw was and if removing it would increase power. I answered them. You are throwing in what-if's that that are moot. If you have cranked up your pump you obviously have added a turbo which makes a torque screw unnecessary. If you add a torque screw to a turbo pump then of course you will cut the max fuel back. At what rpm it cuts the fuel back depends on how far you turn the screw in. We seem to be going in circles here not in the real world.ie trying to get 180cc out of a DB2.
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Old 12-14-2012, 12:46 AM   #29 (permalink)
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RacinNdrummin- you are missing the point. 2 posters on here asked what the torque screw was and if removing it would increase power. I answered them. You are throwing in what-if's that that are moot. If you have cranked up your pump you obviously have added a turbo which makes a torque screw unnecessary. If you add a torque screw to a turbo pump then of course you will cut the max fuel back. At what rpm it cuts the fuel back depends on how far you turn the screw in. We seem to be going in circles here not in the real world.ie trying to get 180cc out of a DB2.
No I am not missing the point, The points I am making, and the points you are making are not necessarily incongruous... I am simply saying that your blanket statement about the TS only limiting higher RPM fuel flow is not necessarily correct. It might be the case for a stock fueled pump, but the influence the TS has on fueling increases with how much volume the pumping chamber is set to deliver.

I am not talking about a 180cc DB2, I am talking about my own 180cc DB4 on my truck, and it uses all the DB2 parts for that function of the pump... If I turn my Torque Screw in, at all, it limits the fuel at a far lower RPM than if I was just running a simple stock pump. With the calibration my pump was set at from the shop, with stock metering valve travel, I would clear out all my smoke at 29psi and 2200RPM or so. I tossed a 6.2 spring in it, and I got more RPM, but still would clear out my smoke, which was telling me that my gov wasnt pulling any fuel that early, so it was an issue of the metering valve not open far enough at WOT... Finally, after trying out about 20 different adjustments, I shortened the linkage so I would get full metering valve travel, and it gave me significantly more fuel, I was no longer clearing up all my fuel by 1800-2200 RPM, I actually had a haze... Now, all that says is that the metering valve becomes a restriction somewhere around 150cc's at its stock adjustment...What does that have to do with a guy running a stock pump you say? Nothing, thats not the point I am trying to make... I was actually interested to read the numbers you posted above, because all my experience is with tuning the trucks in real time, and on the dyno. Even though I understand the pumps function I havent had the number directly in front of me on a test stand, just simply based on the results of tuning, which in some cases is a better way of knowing whats going on. I simply have the calibration numbers for my pump that my shop gave me. However, I was simply pointing out, just for informations sake, that the blanket statement that the TS only limits high RPM fuel, isnt correct, because it depends on how much volume the rotor is setup to move, and I was simply using my truck/pump as an example of that. It wasnt saying you were wrong, just making a sweeping generalization, thats all.

For what its worth, even on a Turbo cal pump, I didnt notice any significant difference on the dyno when playing with the Torque screw...
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Old 12-14-2012, 09:51 AM   #30 (permalink)
 
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I was able to get my torque to go +/- 30rwtq by messing with the torque screw on the dyno on a 90cc pump.
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