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Nate Stanley 03-06-2003 01:47 PM

Here's another baseline for you. I'm considering installing a boost controller as well, and I've had a boost gauge on my car for the last 10 months.

absolute max boost at 70-75 mph under full throttle, 9.5 psi
boost at 65 mph cruise, 8.5 psi

22-23 mpg @ 60-75 mph
269,200 miles

Hope this helps-

mholbrook 03-06-2003 02:31 PM

Dawes Boost Controller/Boost Gauge Installed - Comments
I installed my Dawes Boost Controller yesterday. Boost control gauge went in on Saturday. T-ed it into the line from the banjo fitting. EZ installation and can now spray WD-40 and air down the line by just pulling the hose off the T for quick cleaning. Also, it would seem that if the banjo was plugged up, the boost gauge would not register correctly so it would seem to be an ez way to monitor this.

With the stock wastegate controller from the factory, I was getting 9psi boost at max. Engine is running great and did the banjo fitting clean, changed both fuel filters and did a diesel purge. Ran it for a couple days to get a good baseline.

Installed the Dawes device yesterday and after a couple runs, have it set to max at 13.5 psi boost. Hard as I have run it, it does not seem to go above that. I'll have a good check this afternoon on the way home as I'll take it up a long grade under full load.

With the Dawes installed, the driveability is noticeably improved. The car pulls stronger and spools up quicker. I do notice that at 75 it seems to boost to about 9psi where before it was at about 7.5 or 8 psi. I have not had it on the car long enough to measure any mileage changes or monitor anything else. I have been getting about 22-23.5 mpg running back and forth to work 80% freeway at 75 miles per hour.

I would really like to hear from other listers about what they are running for max boost; what kind of mileage changes; any difference in coolant temps that were noticeable; and any other information that might be interesting.

So far, my impression is that the Dawes boost controller is very much like the difference between a "chipped" car and one that is not chipped. I would not say that my diesel has "neck snapping" accelleration (at least compared to the 240hp BMW I was previously driving) but it is able to get out of its own way and keep up with any traffic. I'm back in the fast lane!

Mike Holbrook
1983 300TD-T

rwthomas1 03-06-2003 04:22 PM

I believe the factory MB safety fuel cutoff is actuated at 1.1bar @15psi so setting above that won't do you any good unless you bypass it and that wouldn't be very smart.... I would say 13.5-14psi is a good stopping point since it is clearly within the MB "safety" envelope. If you were willing to do a custom intercooler ala Ben Ridge then boost could easily be tweaked up to 17-18psi LIKELY without issues. It your engine so experiment at your own financial peril. RT

BOGDAN 03-06-2003 08:09 PM

Please guys can you explain me where to buy a presure regulator Dawes and how to be instaled
did the fuel milage will be hurt or inprove at biger presure?

190DTurbo 03-06-2003 11:16 PM

can I use this on my 87 190D turbo? If so where can I buy it?

speedy300Dturbo 03-06-2003 11:42 PM

You mount it inline with your existing wastegate hose. Some vacuum adapters may be necessary.

speedy300Dturbo 03-07-2003 12:40 AM

The POINT of this boost controller is to bring boost back UP TO FACTORY SPEC. With a boost controller and gauge, it makes it VERY EASY to dial in the proper amount of boost as opposed to adjusting the wastegate screw which is a PITA on Garrett turbochargers.

roberth58 03-07-2003 01:16 AM

You dont even need a real boost dash in the dash. I installed one on my 900 turbo many years ago and used a mityvac to set it to 13psi installed it, had fun and destroyed a perfectly good set of tires :)

vwbuge 03-07-2003 06:03 AM

If any of you guys have pics/intstructions on your install, that would be great!!! I installed a lighted boost guage last year on my SD in anticipation of installing a controller. Pics and instructions on your install and adjustment to the ALDA.....pretty please!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

ck42 03-07-2003 01:00 PM


The normal ALDA adjustment procedures could take care of an increase in boost.

Just like when I've adjusted my ALDA 'down' to the point that faint whisp of smoke are seen on a sunny day at 4k RPM, the same could be done once the DAWES device is installed.

Granted, if I found that my boost was LOWER than *spec*(13.75-14.25@4K RPM) before installing the DAWES device, I'd adjust the ALDA 1-3 turns CW FIRST...then install the device. Then, I'd go thru the regular ALDA adjustment and bring it back down to the faint whisp condition.

At this point, the new boost curve and fuel curve should be kosher.

'85 300SD

ck42 03-07-2003 02:05 PM

"normal adjustment" being the crude DIY'er method of adjusting the ALDA. The correct/precise way being having it done professionally.

Where did I obtain *what* specification? The boost level? If so, I've gotten it from other MB threads from people who are in-the-know. Official Max boost should be ~.95 Bar (~13.75 PSI).

Forgot to mention before.....max boost pressure will NOT be achieved if the ALDA is set too low (not enuf fuel). Insufficient fuel will be delivered which means max possible boost pressures will not be achieved.

Conversely, If the ALDA is adjusted for too much fuel, there will be excessive fuel that can't be burned at full load and speeds above 4K RPM and will end up lowering combustion temps and creating more smoke....BUT max boost pressures *will* have been achieved.

'85 300SD

rwthomas1 03-07-2003 02:14 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

ck42 03-07-2003 02:39 PM

"I've sent pumps to him for PERFORMANCE TWEAKING, which would BURN THE TIRES OFF a 300DT without any BOOST MODIFICATIONS ! ! !"

Would love to know how. Simply sending more fuel to the motor is not sufficient. What do you think all that black smoke coming from the tailpipe is when you've turned your ALDA too high? It's unburnt fuel.

Please elaborate.

BTW....the 'hearsay" you refer to comes from EX- multi-decade experienced MBZ mechanics. Not exactly your run-of-the-mill backyard DIY'ers.

'85 300SD

rwthomas1 03-07-2003 03:25 PM

I agree completely that the only correct way to "tweak" a pump is to have a professional do it on a test bench. The problem is that this is not always cost effective to do and many shops simply won't do anything but set the pump to factory specs for liability reasons. In the case of my truck the local pump shop would only do the "factory spec" settings. So following some instructions from Banks Performance I opened the top of the pump and turned it up myself. When I had the pump done on the Jetta I used a different shop, got friendly with the tech, he agreed to do what I wanted, he redid the pump and the pop pressures on the injectors. Calling it fast wouldn't be right but it'll smoke a stock turbodiesel jetta of the same era. Regarding MB's and adjusting the ALDA and boost. I can't see how adjusting the boost to the upper limit of the factory spec either with a Dawes Device or just tweaking the factory wastegate will cause anything other than the engine to perform as it was intended. Tweaking the ALDA is a questionable yet proven method to improve driveability. Especially off-idle acceleration. I tried a 1/4turn ccw and it helped a bit then another 1/4turn ccw for a total of 1/2turn ccw and the driveability off-idle has gotten much better. I tend to believe that since my car was originally a Kalifornia car the fueling was set very conservatively for emissions reasons. Increasing it a little won't hurt anything. You gotta remember that while there is always the "right" way to do things, and a pump shop will be happy to tweak your pump and lighten your wallet by $500-$1000 for it, there is nothing wrong with a little "backyard engineering" on a old car thats only worth 2-3K. If tweaking the ALDA a 1/2turn gets you what you want then I don't have a problem with it. I do however think you should know what the possible consequenses of your actions might be and adjustments kept conservative and within or at least close to factory settings. RT

rwthomas1 03-07-2003 03:27 PM

Simple answer....
"Alrighty then . . .

EXPLAIN WHY the TAMPER CAP is broken off the Aneroid and the De-fusser Balls are melted as if someone took a torch to em' ? ? ?

Balls in YOUR court . . ."

The tamper cap was removed. The aneroid was adjusted to deliver way too much fuel. There were no gauges to indicate the engine was operating in melt-down mode so the idiot that adjusted it was blissfully unaware as the engine ate itself.

I do not recommend adjusting the boost beyond the factory maximum setting. I also don't recommend anyone mess with the ALDA unless the have the correct instrumentation to make sure nothing bad is happening post adjustment. That said a 1/4-1/2turn ccw on the ALDA is not a huge change but if you go ahead and turn the bloody thing all the way out and run without gauges you are playing with fire. Theres always a risk. I just advocate that you know the risks going in and monitor changes in engine performance with quality instrumentation so that you are very aware of problems long before they occur. The engine would have been fine if the operator had EGT/Boost gauges and heeded their warnings. Things don't just melt for no reason and without warning. RT

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