Thanks for the photos of the Fourtrack. It would be cool to see what kind of things youre doing to it, sounds enticing if youve changed to rear suspension config three times! More on the trooper too.
Here is a link to the catalog site I use:
http://catalogs.marketparts.ru/
It's a Russian site but it's possible to navigate without knowing Russian as all your'e looking at is pictures and part names are in English. Basically click on ISUZU then either search by VIN or "США" (USA), ОБЩИЙ is all other markets. Ask me if you don't understand something.
As for that article: I will PM that to you. Have a read, it will explain exactly what the top screw the diaphragm/cone and starnut control. There is another fuel adjustment screw on the Bosch pumps that adjusts fuel throughout the entire RPM range, but it's very sensitive and you should adjust at 1/8 turn at a time. I wouldn't touch this overall fuelling screw unless you are running lean in all situations. To get the best balance between power and economy a diesel should produce a light smoke at full throttle. Of course if you stomp on the throttle you will always get a puff until the turbo has caught up with the air side of things. Medium smoke is ok but you are throwing a little unburnt fuel out the exhaust so that may be a factor if economy is of concern.
From what I gather what you've done with the boost is change the waste gate position. I don't think you have actually increased intake pressure. I would return the wastegate pushrod adjustment to normal as a slightly open waste gate will cause higher load on the turbine to produce adequate intake pressure as the wastegate will always be relieving pressure. You will run especially hot combustion between 1500 and 2000 RPM, right before the turbo starts to build intake pressure. An adjustment that is too tight will put needless strain on the wastegate actuator components.
What you can do to increase intake pressure in locate the wastegate signal hose and splice in a manual boost controller, which is essentially a valve that uses a ball bearing and spring to regulate how much pressure can pass through the line. You can make this controller from regular air compressor fittings bought at a hardware store. By hooking up an air compressor or a bicycle pump with an pressure gauge to the wastegate signal hose instead of the compressor side of the turbocharger you can check the air pressure that is needed to activate the wastegate and adjust your boost controller to achieve desired pressure. For example if the untouched wastegate opens at 13psi and you want to increase opening pressure to 16psi you must restrict 3psi in the signal hose. Essentially you reduce the pressure in the signal hose by 3psi so the wastegate opens later allowing exhaust pressure to continue to spin the tubine shaft and build pressure longer. Hopefully that makes some sense. Here is a photo of a DIY boost controller.
Here is a photo of what this setup looks like:
Do note that if you increase the intake pressure, you must also adjust the fuelling accordingly. Tricking the wastegate in this way will not only increase peak boost pressure, but also change when and how fast the pressure will rise. Thus you will have to change when "on boost" fuelling begins, how fast the fuel quantity increases and peak fuel quantity. The article gives a decent idea of how to adjust the compensator for these modes. Also note that there may be a safety relieve valve in the intake system, it's ususally on the intake manifold and will open to relieve intake pressure at whatever preset pressure the spring in that valve is compressed. You may have to modify that valve if it is releasing your 16psi of boost that you are working to achieve. Just something to look out for.
As you said the boost controller is a totally different thing than a blow off valve. Even though the name suggests it might not be. A blow off valve is installed on gasoline or other engines that are throttled by air. It is designed to relieve the pressure build up that occurrs between the turbo and the throttle plate when you drop the throttle for changing gears and such. A blow off valve is useless in a diesel engine as a diesel is throttled by fuel and doesn't have a throttle plate.
And finally, $400 odd is steep for a steering box, especially if it's from a wrecker. We have a Trooper in the local "pick n pull" self serve yard, if you want I can take a look at the steering box in it next time I go. I think they want about $70 for a box plus slowest shipping to Chile costs a little more than $100. Let me know if you'd like me to check if the box is any good I might be going either next weekend or the weekend after. Your trooper is LHD right?
Too much writing, time to sleep, but hopefully it helps you somewhat. Please post more updates. I saw in one of your videos that you have a rear bumper on the Trooper! Looks home made!
