Boost/guages/MBC questions... - PeachParts Mercedes-Benz Forum

PanzerSD · #1 10-06-2006, 12:22 AM

In reading a similar post, I have some questions....
(yes I need a seperate thread)

1. if I put a finely adjustable valve inline of the wastegate hose, does that act as a MBC? manual boost controller?

2. is there any sort of sound or other indication that my wastegate is infact working?

3. would my boost gauge (when I get it) give more acurate readings tee'd off the wastegate line or driect in the manifold?

I know these maybe stupid questions, but I just don't feel like using the search function right now (for all you smartasses out there! )

Jeremy5848 · #2 10-06-2006, 02:53 AM

I'm just getting used to my boost gauge as it has been installed for only a few days. The line to my gauge is connected to a spare tapped hole in the intake manifold, a couple of inches at most from the spot where the line to the ALDA connects. I decided to use this spot rather than risking breaking the line to the ALDA.

My boost gets up to between 10 and 11 psi and then kicks back to about 8 psi. It's a definite kick, clearly something is happening, which I suppose is the waste gate on the turbo opening. I can't hear anything one way or the other; didn't even know the wastegate was operating until I watched the gauge. It does this, by the way, in third gear, fairly hard acceleration (such as it is

) at about 4000 RPM.

Is the waste gate adjustable? I didn't see anything on it that looked like it might be an adjustment screw. Some posters have reported boost of 13 psi or greater; I don't know if they have an aftermarket boost controller or what.

I don't think you would want to attach your boost gauge to the wastegate line. Most reports that I have seen include discussions of the various merits of attaching to the manifold, as I have done, or to the ALDA line, either before or after the protection switch. It's also possible that all engines don't have the extra tapped hole in the intake manifold so some folks may not have a choice.

I'll be posting info and pix of my 3-gauge panel (replaces the ashtray) when the woodwork is done. One hint: 3 gauges is a tight fit in the ashtray slot but it turned out good. I found a stain that darkens the zebrawood that I bought so it is almost a perfect match for the wood the car came with.

Jeremy

pgringo · #3 10-06-2006, 04:07 AM

1. if I put a finely adjustable valve inline of the wastegate hose, does that act as a MBC? manual boost controller?

no. a mbc opens when a certain amount of pressure is built up behind it. or is it the other way around?

2. is there any sort of sound or other indication that my wastegate is infact working?

no. but if the mbc is set at a high enough amount of boost, you will know when it is working when you get thrown back in your seat. just be sure to put hose clamps on there. the first time i hooked up a mbc, the hose popped off. it's a good thing the car i was driving, volvo 740 turbo, has a computer cutoff at 15psi boost. also, bump your boost up in small increments. you don't want to blow the motor while just messing around. next thing to invest in is a big azz intercooler! i <3 boost.

3. would my boost gauge (when I get it) give more acurate readings tee'd off the wastegate line or driect in the manifold?

go off the manifold.

Shorebilly · #4 10-06-2006, 06:49 AM

Quote:

Originally Posted by Jeremy5848

Is the waste gate adjustable? I didn't see anything on it that looked like it might be an adjustment screw. Some posters have reported boost of 13 psi or greater; I don't know if they have an aftermarket boost controller or what.

I'll be posting info and pix of my 3-gauge panel (replaces the ashtray) when the woodwork is done. One hint: 3 gauges is a tight fit in the ashtray slot but it turned out good. I found a stain that darkens the zebrawood that I bought so it is almost a perfect match for the wood the car came with.

Jeremy

G'mornin' Folks,

I have been searching for info in this area, due to a vacuum leak that I had. I have found that the Boost Dump/Waste Gate...or in MB terminology "Recirc Air Safety Valve, is controlled on '85 300D-T (Federal) and '84 & '85 300D-T (Califunya)...by the EGR Control Unit (supposedly located behind left kick panel).....EGR Control Unit has inputs from Fuel Rack Positioner, Engine Speed, Coolant Temperature Sensor......and outputs to Recirc Air Safety Valve, EGR Vacuum Amplifier, Engine RPM Output [to tachometer page 120/1]
.....and there is (according to schematic) a place to cinnect a "Trimming Plug"......which I have no info on so far.......but may be an adjustment for the whole inter-related shebang.......

I have also had the thought of replacing my ashtray with 3 gages....Boost #, Exhaust Temp, and Vacuum (Pressure at Vacuum Supply Hose to Brake Booster).......what 3 points are you planning to install gages for (besides Boost)......if I may ask, where did you get the Zebrawood......and where did you find small gages????? I am considering a digital display, however I would prefer to find analog gages that look similar to the original MB dash gages.....

Thanx,
SB

WD8CDH · #5 10-06-2006, 08:19 AM

http://www.egauges.com/ has VDO and other gauges.

Stewart Warner has a few 1 1/2" gauges but they are not cheap.

http://www.sw-performance.com/products/products.aspx?productcategoryid=95&ispod=0

Jeremy5848 · #6 10-06-2006, 12:32 PM

Quote:

Originally Posted by Shorebilly

I have also had the thought of replacing my ashtray with 3 gages....Boost #, Exhaust Temp, and Vacuum (Pressure at Vacuum Supply Hose to Brake Booster).......what 3 points are you planning to install gages for (besides Boost)......if I may ask, where did you get the Zebrawood......and where did you find small gages????? I am considering a digital display, however I would prefer to find analog gages that look similar to the original MB dash gages.....Thanx, SB

My 3 gauges are Exhaust Gas Temp, Turbo Boost, and Voltmeter. They are VDO "Vision" series gauges, 2-1/16 inch. They look nice, are similar to the factory gauges, are easy to read and have excellent nighttime illumination, which is great for us old farts and our weak eyes. I got the gauges from egauges.com. They are a tight fit, you have to work carefully but you can get them in. You have to remove the ashtray and its mounting bracket (two Phillips screws). The power line for the ashtray can be 'recycled' to provide power for the voltmeter and the EGT gauge.

I got a piece of zebrawood from a local store called 'Woodcraft.' I know little about wood working and am not very skilled; I can make firewood out of almost anything.

In the attached photo, the zebrawood is not yet stained and finished -- everything is sitting there, held together by gravity. I found a mahogany stain that makes the wood look very much like the factory color. In the meantime, the gauges are in the car on an aluminum panel. When the wood is finished, I'll sandwich the wood and aluminum together for extra strength.

I also have a vacuum gauge, actually a pair of them, so I can monitor the vacuum system but they are not in the cabin. One is in the engine compartment, so I can check on the vacuum system while working on the engine. The other is in the trunk so I can check the vacuum reservoir. Turns out the reservoir sits at about 15 inches and drops a couple every time you lock and unlock the car. Interesting to watch.

Jeremy

bgkast · #7 10-06-2006, 03:20 PM

Nice job! That is going to look great. I have gauges for my veg system mounted in the same place, but I am selling the conversion on ebay currently and am going to keep the gauge pod I made. Mine holds two gauges a switch and a LED for the switch. I al going to go with a boost gauge, pyrometer, and the switch will turn on a fan mounted on my Air/water intercooler radiator.

Shorebilly · #8 10-07-2006, 05:30 AM

G'mornin',

Been to eGauges, have been looking at the ISSPRO EV Auto Red Series....has a nice Exgaust Temp Gage set up for Diesels, and also the Vacuum and Boost gages that I want to install......

Your VDO setup looks very nice, and that Zebrawood will look fine when finished.......I am not the greatest woodworker either, ditto to the firewood comment.....when I was a Cadet Engineer I had to learn to weld and run most machine shop stuff, like milling machines and lathes, shapers, etc.....and luckilly I have a friend who has all of the above mentioned stuff in his shop.....and I have access, when he's not using them for his Harly Restoration Service........

SB

Jeremy5848 · #9 10-07-2006, 01:15 PM

Quote:

Originally Posted by Shorebilly

.....when I was a Cadet Engineer I had to learn to weld and run most machine shop stuff, like milling machines and lathes, shapers, etc.....and luckilly I have a friend who has all of the above mentioned stuff in his shop.....and I have access, when he's not using them for his Harly Restoration Service.......SB

I had machine shop privileges when I was in school and greatly miss them now. There's only so much you can do without a Bridgeport.....