I have a 98.5 4x4 5 speed that is box stock truck with 200k miles and was wondering what the max boost would be if I put a boost fooler and a boost elbow or just capped of the waste gate line. I am not looking to make goobs of power but wondered if I will see any power increase or if it will hurt my engine in any way . From what I learned many years ago as a owner operator the more air with the same fuel rate would drop the EGTs. I have installed a full set of gauges and will be ordering a Fass DDRP in a week or so. I can get a max of 20 PSI at wot before it defuels or opens the waste gate or both and if there is any more power to be had I would to be able to use it if needed. I don't want to by a comp if I don't need one. I will be going on a trip in Sept with a small trailer and it will be the determining factor. My trip will be at least 3 weeks and cover close to 6k miles so the truck needs to be rock solid reliable

If it is stock I would think you could clamp it off completely and be fine.  I don't think a stock truck could hit 35psi.  You are right about more air lowering EGT's.  I built my own little blowoff for the wastegate so it stays shut until I hit 35 psi and I do think it did a good number on EGT's since I am not fighting a wastegate past 20psi (where it is opening).  

 

The problem might be that you have a computer that will see that boost and throw overboost codes and might defuel or something.  I'm not sure, I'm not a 24V guy, but I think that would be your only issue.  

ISX got it. You going to need a Edge Comp or something to do boost fooling. Other than that the whole idea of changing the wastegate goes out the window. What happens is as the engine sees above 20 PSI its to defuel and shut down by 25 PSI it will/should throw a P0234 code for overboost code. So if you wanting any more boost your going to need a fueling box like a Edge Comp or similar for boost fooling. 

 

As for controlling EGT's is easy drop 1 gear and kick the RPM's up and the EGT's always fall.

You can easily throw a performance box on these trucks without sacrificing any reliability whatsover. I run a Smarty and a mild set of injectors and drive sensibily and get better fuel mileage than I ever did in stock form. What's nice is the power is there when you need it pulling a hill or coming from a stop to get a load moving. These ISB engines are tough platforms they really are a medium duty engine in a light duty pickup.

I just went through this not long ago. With a fooler and the wastegate plugged I see 28-30 psi max and with stock injectors.

Thanks guys. Back when I was a owner operator in the late 70s early 80s we never ran a waste gate but very few Cummins that I knew of would hit 20 pounds of boost. We used to run the 855 CI engines and the were very touchy and you could blow one up if you pulled one outside of the 300 rpm operating range. This truck has been a learning experience and from what I have read and seen they really are almost indestructible compared to what I learned on. The reason that I bought the 24v was so if I decided I needed more power I could just put a box on it but if I don't need one I was not going to put one on because if I had one I know I would be using it even when I didn't need it ( might enjoy it to much and kill my mileage). I bought mine because I had a 95 v10 that I really liked the power and torque but the feds have been messing with the gasoline and I watched my mileage drop from 15 MPG down to 8.5 MPG empty or loaded.

You know what, Nekkedbob, After being out of the big truck scene for about 25 years I still think the little Cummins is a 1500 to 2100 RPM engine just like the 855 series. I have run a 290, 350, and a 400. The NTC400 was a dog in my opinion.

I know I would be using it even when I didn't need it ( might enjoy it to much and kill my mileage).

 

Not true. I've ran a Edge Comp now since 2006 on 5x5 till I upgraded to RV275 injectors and toned down to 5x3. Basically the box is wide open 120 HP with defuel mode of 67% of stock fuel till 10 PSI of boost. But I drive daily on this setting even towing. Empty I'm getting 22-25 MPG easy. Loaded with a trailer 7,000 to 8,500 pounds still manage 11-14 MPG.

 

 

I could just put a box on

 

You should this will give you better power and fuel management than you don't have now.

 

 

This truck has been a learning experience and from what I have read and seen they really are almost indestructible compared to what I learned on.

 

As long as you have gauges and a good fuel system right off then a enhancement box like Edge is just fine and these trucks handle the enhanceent just fine. But like I said you get better fuel and timing management over the stock ECM program which is built around the EPA rules.

You know what, Nekkedbob, After being out of the big truck scene for about 25 years I still think the little Cummins is a 1500 to 2100 RPM engine just like the 855 series. I have run a 290, 350, and a 400. The NTC400 was a dog in my opinion.

 

 

I had 290 ,335 and 380 ( special build by a shop in Fremont Ca. ) and I think I liked the 335 the best. I still  fight the urge to shift at 2100 but with the horrible spacing in the 5 speed I force myself to shift at 2400 ( like driving a Detroit ) so I don't pull it below 1500.

 

Not true. I've ran a Edge Comp now since 2006 on 5x5 till I upgraded to RV275 injectors and toned down to 5x3. Basically the box is wide open 120 HP with defuel mode of 67% of stock fuel till 10 PSI of boost. But I drive daily on this setting even towing. Empty I'm getting 22-25 MPG easy. Loaded with a trailer 7,000 to 8,500 pounds still manage 11-14 MPG.

 

 

You should this will give you better power and fuel management than you don't have now.

 

 

As long as you have gauges and a good fuel system right off then a enhancement box like Edge is just fine and these trucks handle the enhanceent just fine. But like I said you get better fuel and timing management over the stock ECM program which is built around the EPA rules.

 

Your last statement has sold me now for the $$$ . The first thing that I bought and installed was a set of gauges , BHAF and have a Fass  on order. The PO replaced the IP 50k ago ( the stock lift pump went out and he didn't have a FP gauge ) and put a stock lift pump with a cheap fuel pressure gauge in it so now it has an A pillar set by ISSPRO. As it sets now I get as low as 18 and on a 400 mile trip I got 21.4 but I haven't pulled my trailer that is only 2700lbs , that will happen at the end of sept.

I'm always pulling trailers either my RV or the utility trailer but the difference is my two typically weigh in at 7,000 to 8,500 pound in trailer weight given me roughly 16,000 to 17,000 pound gross combined weight.