After months of putting off the job of removing the tamper proof bolts Merc put on the injector pump to keep people like me out of the injector pump I spent Saturday morning removing the tamper proof bolts on the injector pump. I’d had the two easy to get to off boost base enrichment off for ages with just a ½ turn tweak but there are 4 others at the back of the I.P that are tricky to get to to tamper with them. But, I found with the steering on full lock right and the correct skinny but long flat blade screwdriv, sorry chisel and a small hammer you can get in there and very slowly and gently get them turning with nice little gentle taps.
Once you get them a couple of turns around you can get in there with some pointy nose vice grips and get them the rest of the way out. This allows you to get to the main rack adjustment. The thing Merc didn’t want you to adjust and the thing I was here to adjust.
Now I would 1000% say you shouldn’t play with this stuff without knowing your Exhaust Gas Temp’s and having a reasonable understanding of the consequences of your actions. That is, too much fuel and EGT’s go up and things get melty. You don’t tune for flat road with no load. You tune for big long hills in 8th with your target weight on the back. If you add a bucket load of fuel in the off boost area whilst it might pull really well on flat ground when you are lugging in sand or you fall off boost going up a hill and you are going to end up with a ton of fuel heating things up right where you don’t want to be doing that. Again things you don’t want melted will get melted. So you tread a fine line and tune it for the heavy load area and keep it nice civil. I don’t see the point in rolling coal, a small puff of light brown and you’re golden or golden brown if you will. I have my EGT probe in the exhaust manifold pre turbo. That’s about as close to the action as you can get and its what is really going on. As it happens Porsche did the same thing. If any numpty says something to you like “but what about if the EGT prob fails and it goes through the turbo herr derr” you should look at them with distain, question their knowledge and what they are trying to sell you. I’ve been doing stuff with turbos for over 25yrs on all kinds of things and I’ve never seen or heard of it happening. I have however seen plenty of melted pistons. It was ok though as on those engines the post turbo EGT probe let the owner know it was too hot when melted stuff came past the probe heating things up. EGT not TGT.
Anyway once the covers off the back of the pump it’s pretty simple undo a 10mm lock nut holding the adjuster in place then turn the screw in for more fuel and out for less fuel. You don’t need to make big adjustments anywhere here. In both areas I’ve done a single turn. That’s all it takes. With this done I cleaned the fuel strainer and changed the 2 fuel filters before going on a quick test drive up some big long hills. No weight on the back for this it was simply to check my work and warm up the oil. Everything looked good so I changed the oil and filter then loaded up my ramps for Sunday.
I’d notified service NSW of my intention of travel and sorted out the QR code paperwork. On Sunday I set off on my 600klm round trip knowing I would be going over the great divide empty one way and loaded with about 2tn on the way back. This is pretty much my target weight when I go hunting etc so perfect for testing my tune out. Stock I’d do the climb up at about 20kph in 3rd this would be at max 2,800rpm After the turbo, exhaust and intercooler and just a ½ turn on the off boost I was doing it in 5th or 6th at 45 to 50kph again at 2800. Unloaded on the way there I did it in 8th at 88kph at 2500rpm. Loaded on the way back I did it in 7th at 80kph holding it off WOT as it was sitting perfectly on 23psi of boost and a max 620c EGT with 2400rpm on board. I could of grabbed 8th but the engine was just so happy I let it eat.
I’m over the moon with the result. Over the entire trip the only time I had to shift out of 8th was either stopping or once for the hill on the way back. You can roll along through a town with a 50 zone in 8th then simply put your foot down and will pull like a train right back up to 98kph. I tend to sit on about 92/94 with the hand throttle down and enjoy the ride. A quick tap of the exhaust brake pops it back to idle rpm.
Now I've got a winning combo I'll replicate it on the new truck.