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Discussion Starter · #1 ·
well i have heard in the past that on a cummins you can do alot of things to the engine for free and get easly 350 hp. for free. can you do any kind of these things you can do to a obs psd. for free?

something like turn up the fuel pump:dunno:
 

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It's a small computer that operates everything. Older 12v's did not, That is why you could manually turn up boost and fuel supply. I am in no means a 7.3L expert, But if everything is manual, Then yes it will be cheap to produce a little more power. If anything this will be a BUMP for the guy's who know these trucks.
 

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Discussion Starter · #5 ·
It's a small computer that operates everything. Older 12v's did not, That is why you could manually turn up boost and fuel supply. I am in no means a 7.3L expert, But if everything is manual, Then yes it will be cheap to produce a little more power. If anything this will be a BUMP for the guy's who know these trucks.
:bump::bump::bump::bump::nod:
bump!!!
 

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Nope, even the OBS Powerstrokes are computer controlled so you cant turn up fuel pump. Only thing i know of thats "free" would be the FPR shim, but that just really smooths out idle and makes sure the engine is getting adequate fuel pressure and as such isn't a "big power" mod.
 

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Nope, even the OBS Powerstrokes are computer controlled so you cant turn up fuel pump. Only thing i know of thats "free" would be the FPR shim, but that just really smooths out idle and makes sure the engine is getting adequate fuel pressure and as such isn't a "big power" mod.
Well here ya go, You found your man.:thumb:
 

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Even with the 12 valve cummins, you can't hit 350 HP by just "turning up the screws"
Turbine housing, injectors, fuel pin, pump adjustments, exhaust and a high-flow air filter will get the old cummins to around 300 HP. Diesel Power magazine "Project Rustbucket" for reference.

As far as the 7.3, the 10K (or 18K?) resistor mod for the IPR, FPR shim (as previously mentioned,) IDM resistor mod, and DIY air intake. These will make only slight improvements to power output. To really get increased power, you will need a tuner, or chip. If you get a tuner/chip, BUY GAUGES!!! since you will need to monitor EGT and prevent cooking your engine, especially when hauling heavy loads.
 

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Even with the 12 valve cummins, you can't hit 350 HP by just "turning up the screws"
Turbine housing, injectors, fuel pin, pump adjustments, exhaust and a high-flow air filter will get the old cummins to around 300 HP. Diesel Power magazine "Project Rustbucket" for reference.

As far as the 7.3, the 10K (or 18K?) resistor mod for the IPR, FPR shim (as previously mentioned,) IDM resistor mod, and DIY air intake. These will make only slight improvements to power output. To really get increased power, you will need a tuner, or chip. If you get a tuner/chip, BUY GAUGES!!! since you will need to monitor EGT and prevent cooking your engine, especially when hauling heavy loads.
I'd have to go back and look at that article but it sounds like it is in reference to a 1st gen Cummins which had the VE pump. The 2nd gen Cummins was still a 12 valve and still machanical but it has a P pump. You can get a lot more with them without spending much money than you can with the VE pump and most likely can get the 350hp or close to it. The fuel plate in itself is quite an improvment and if you know what you are doing you can grind the stock one in such a way that you can get quite a bit more fuel out of the pump.

However as stated the only mods you can really do on the PSDs are the 10K mod which increases the injection control pressure and helps inject more fuel. On the '94-'97 trucks it really doesn't do much. Or the fuel pressure regulator which really doesn't do much. From my experience more fuel pressure makes for a worse idle and many have complained of worse fuel economy from it as well if you shim it up to much.

To really get gains you need more fuel in the way of a programmer. The intake and exhaust mods won't give you any more power either but will help keep your exhaust gas temps down and help the air flow through the engine. Once you get a programmer the bottle neck is the injectors. The 90cc stock injectors just don't flow enough fuel to really make a lot of power but with a chip will be significanly better than stock. The Superdutys have 135cc or 140cc injectors depending on what year. So a chip makes a lot bigger difference and they make stock about what a '94-'97 makes with a chip.
 

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not to hijack but i did the fpr shim and as you said my idle rpms' bounce around by like 75 up and down, not smooth idk if its the mod or somethin else makin it do that
 

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On my truck I was fighting a nasty rolling idle that would a lot of times kill the engine when I'd roll to a stop. I had the pressure set at about 60 psi or so. Once I discovered that when my fuel pressure was lower the idle was as smooth as every I set my FPR so that it runs about 38 psi at idle and used the boost compensating port to raise the pressure to about 60 psi max as the boost comes up. I found that on the dyno if I ran my pressure to 80 psi I actually lost 10 or so hp. I do have a completely new fuel system with an Aeromotive FPR and pump. So you can't run the stock FPR like I have mine set up with the boost. Just giving my experience with the higher fuel pressures.
 

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On the first gen cummins, you are in about the same boat as first gen psd's. You can turn the fuel up on the cummins, but you will probably only see about 200 wheel HP. That's about the same as an OBS PSD with a tuner or chip. Both will need intake and exhaust.
 
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