1993 DB2 6.5, NV4500, HX35 Boost Control

[Loganshaw_6]

Hey guys, just finished installing an hx35 on the old 6.5 this weekend. Previously I had installed an HX40 but didn't pay any mind to the exhaust housing size. 18 cm was a little bit too big with the NV4500 so it made driving the truck almost miserable. Snagged and HX35 from a 12 valve a few weeks ago. My stupid question is has anybody found a way to manage max boost effectively in a manual transmission truck? I have a home made "waste gate controller" (spring, threaded rod, washers and a couple of nuts) but I'm trying to avoid if possible, the highs and lows of boost pressure. I don't necessarily need to cram 12-13 lbs of boost at 70 mph, 2500 rpm while cruising down the highway unloaded. Sure I can loosen tension on my spring and drop those numbers but I'm limiting my max boost. Fixed vane turbos don't work like VGTs I get that, my lmm Duramax takes care of this on it's own. Does stick vs auto make a large difference? It's obviously a DB2 not a DS4 so I'm even more limited but has anybody found a good "smarter" combo to manage boost for my setup? I'm guessing the answer is no.

 

[Twisted Steel Performance]

Well I'm betting your spring is too strong or not strong enough... Home made isn't always better.

Keep running those numbers at a easy cruise and you will have more problems... I'd spend a few dollars and buy a turbo master with the correct spring and the correct geometry to start with... Or you could always use the setup that the turbo was designed with, a boost referenced controller and adjust it to the boost you want and forget about it...

 

[Loganshaw_6]

Well I'm betting your spring is too strong or not strong enough... Home made isn't always better.

Keep running those numbers at a easy cruise and you will have more problems... I'd spend a few dollars and buy a turbo master with the correct spring and the correct geometry to start with... Or you could always use the setup that the turbo was designed with, a boost referenced controller and adjust it to the boost you want and forget about it...

I tested the truck with the original vacuum waste gate along with an adjustable elbow with the Allen set screw in the housing and I couldn't keep boost down. If I'm not mistaken don't the original hx35 waste gate actuators work off boost pressure? I went ahead and swapped over to the setup from the HX40. The spring could possibly be too tight.

 

[Twisted Steel Performance]

Most all real holsets are boost controlled, the 40 is set around 20psi, so the assembly rod has to be adjusted, it's easy to get it close on a bench with a air hose and regulator, then fine tune it in the truck.

The boost pressure way won't move the arm like a spring does, that's why holsets use it...

 

[Twisted Steel Performance]

And it works off pressure not vacume...

 

[Loganshaw_6]

And it works off pressure not vacume...

Assuming mine is functioning properly I think this is probably the solution to my problem. I somehow overlooked it being pressure controlled.

 

[MrMarty51]

Assuming mine is functioning properly I think this is probably the solution to my problem. I somehow overlooked it being pressure controlled.

Please post what it takes to get the boost pressure under control.

 

[Twisted Steel Performance]

To be clear, the holset control is pressure operated, hence the hose connected to the pressure side of the housing...