PeachParts Mercedes-Benz Forum - View Single Post - Dawes Boost Controller/Boost Gauge Installed

rwthomas1 · #12 03-07-2003, 01:14 PM

"LEAN mixtures under LOAD at INCREASED BOOST can have a BLOWTORCH effect on PRE-CHAMBER DE-FUSSER BALLS resulting in MELTING PISTONS especially under FULL LOAD . . . "

Not exactly.... There is no such thing as a "lean mixture" in a diesel. This is the most fundamental difference between gassers and oilburners. A diesel on a "lean mixture" is simply not getting enough fuel and won't make rated power. As you increase fueling on a diesel the power continues to increase until bad things happen like melting pistons. There is simply NOTHING wrong with installing a boost controller like a Dawes Device. There are of course some caveats..... The factory overboost control that cuts fueling in overboost conditions must still be hooked up and functioning and the max boost setting must not exceed the overboost control fuel cutoff point of about 1-1.1bar.

"Altering the BOOST CURVE without the FUEL CURVE is DISASTER just waiting to happen ! ! !"

Not exactly.... Altering the boost "curve" or changing the max boost setting without increasing fuel by adjusting the ALDA won't likely change much. Increasing boost without increasingfuel does little to increase power. That said the ADLA is a boost referenced aneroid/mechanisim that adds extra fuel based on how much boost it "sees". Using either a Dawes Device or simply adjusting the factory wastegate setting to increase the maximum boost to just below the overboost fuel cutoff point, about 13.5-14psi will provide the ALDA with the maximum boost signal it can receive and it will respond with the maximum fueling that the factory setting will allow. This is completely safe as the engine will still be operating below the overboost limit and the ALDA is set very conservatively at the factory. Now if you have adjusted the ALDA, all bets are off. Adjusting the ALDA changes the relationship between how much fuel is delivered under boosted conditions and it does so over the entire RPM range and boost range. This is why adjusting the ALDA makes the car seem to respond so much better off-idle and when accelerating. You have increased fueling by "X"% over the entire rpm/boost range. I would strongly recommend installing EGT and Boost gauges if you are going to play with your motor like this. Once you deviate from factory settings on the ALDA you are playing with fire. Granted a 1/2turn ccw on the ALDA won't likely cause any trouble, cranking it out three full turns with or without bumping the boost up may result in an excessive EGT situation, melted pistons or blown headgaskets.

So how do I know all this? Experience. You will notice my truck in my signature. It has no "ALDA" from the factory. The fueling levels in the pump have been turned up enough, combined with a custom wastegate control so that I could easily melt the engine to a lump of slag if I don't pay close attention to the EGT/boost gauges when towing heavy. Why do I choose to do this? Simple, as delivered the truck is very conservatively fueled/boosted. It runs a whole lot better and pulls a whole lot harder with the mods. It has done so for 185K and shows no sign of slowing down. The fact of the matter is as long as you operate below the design thresholds for maximum boost and maximum EGT your engine will be fine and it will deliver all the power it can. Realize of course that you are playing with fire, literally. By adjusting the ALDA you circumvent the factory parameters that act as a "safety net". The only way to truely know if you are doing damage is a quality set of EGT/Boost gauges. Some will say "adjust it until you see light smoke". This is BS. I have seen my EGTs in the truck way up close to the danger zone with NO smoke to speak of!!! And remember I can replace my motor 3 times over for the cost of 1 MB long-block.... Have fun and I hope that someone finds this interesting. RT