Hey all!
(90' D250 Auto 727)
Thanks again to NorCalDiesel for hooking me up on a I/C for my truck! I had a friend help install it and fab up a boost tube for the return side to the intake horn.

I installed an OEM intercooler on my 90' Non I/C truck.
Before, I was able to hit 26-29lbs of boost with just the stock cross pipe. (pump turned up just a bit) After the I/C install, I'm only able to get 16-18lbs of boost. I know that my max boost is going to be lower for at least a couple of reasons...

1)My stock turbo has a Helluva lot more volume to make up with the I/C... (makes sense why the OEM I/C trucks came with that massive 21.5cm housing)

2)After replacing my "zip/cable tie" throttle linkage fix with new plastic caps, I'm not quite able to get WOT. (Re-indexing the throttle lever should help)

3) I have not tried turning my pump up further to compensate, (need a buddy to help protect against the dreaded runaway)...

I have almost entirely ruled out a boost leak in the system. Is it just time to throw down for a used HX35?

Thanks again to NorCalDiesel for hooking me up on a I/C for my truck! I had a friend help install it and fab up a boost tube for the return side to the intake horn.

Anybody have any thoughts or suggestions?
Thanks again!
Ryan

 

I wouldn't rule out a boost leak. Losing 10psi from an I/C install menas either something is wrong with the I/C or you have a boost leak...

I'm sure after you get full throttle travel it will help, but it won't make up for 10psi.

 

Volume has nothing to do with it once the turbo spools. It's not uncommon to "lose" a little less than 5 psi when installing an intercooler, but that's because pressure and temperature are interrelated. When you cool pressurized air, the pressure goes down. You still have the same mass of air you had before.

Not being able to get to WOT is the big issue here, I bet.

 

runaway is scary mine did it when i was on my own as long as you dont panic you will be fine! i bet the wot is an issue as well you will gain more boost from more fuel so turn that fuel up

 

If all you did was install the I/C and you have that much loss in boost, it seems logical that there is a leak in the installation. From personal experience I learned that it doesn't take a very big leak to loose 10 pounds of boost. The way I found my leak was by taking a pressure regulator, pressure gage and some plumbing fittings and building a test rig. I hose clamped a rubber bell reducer onto the turbo inlet and bushed it down to fit a 1/4 inch pipe. I then attached the regulator with gauge onto the pipe and gradully pressed the sysem with air to about 15 psi. The leak I had was at the first elbow from the turbo. You may need to bar the engine over a little to get all the valves in sequence to hold air.

 

pressureize the system and spray all of it with soapy water, that way you can see the leaks.

 

What they said, but I used plumbers caps over the intake and exhaust sides of the turbo, with a valve stem in one. I wouldn't play with your throttle unless you changed it while installing your intercooler. Start with what you changed. You might even be able to get more than 30 psi if you do find any leaks!

 

Why is it that I always think of doing something the hard way?????

 

Pull the tubes loose at the turbo and at the intake. Only test the hoses, tubes, and intercooler, don't test the engine or turbo that wasn't the problem. Plug one end of your hump hose by the turbo or at the intake, use your pressurizing plug "have a cutoff valve in the pressurizing end" on the other end, "slowly" bring your pressure up to about 30 psi close the shutoff valve and spray soapy water on all your connections and across your i/c. If you can have a pressure gauge in your pressurizing plug that way you can close the valve and leave it pressurized and watch the gauge over a period of time also. "Clear as mud?" I've done several and it only takes a very small leak to make you think it has a big hole in it. Good luck.

 

Crank that fuel up and then it will fix your boost problem

Before the truck runs away on ya it should start to "hang" when you rev it up...that is come down really slowly. You know you're close then. I can turn mine in another 1/2 turn past where it starts coming down slow and it still won't run away. Makes the truck a pain to drive though.

Also have a clipboard handy in case it does take off.