Where's the boost??? - Page 2 - PeachParts Mercedes-Benz Forum

Brewer · #16 09-27-2006, 07:42 AM

thanks for the link. I'll be buying one of those myself.

Jeremy5848 · #17 09-27-2006, 10:54 AM

Quote:

Originally Posted by Carson357

where did you get the egt guage? from same site?

Yes, also from egauges (and the voltmeter, too). Also VDO, my favorite gauge maker, used them on BMW motorcycles for over 20 years. See this site

http://www.egauges.com/vdo_mult.asp?Type=Pyrometer&Series=Vision&Units=E

Pyrometers are expensive: this one was $121.90 including the thermocouple (the part that gets hot). Part number 310-153, includes gauge, thermocouple, and 12 feet of wiring harness. You can also buy the gauge and thermocouple separately. This gauge requires 12 Volts to operate (separate from the illumination voltage). I suppose this is to operate an amplifier inside the gauge. So there are six connections: two for the thermocouple, two for 12 Volts, and two for illumination. The "Vision" series of VDO gauges has really great illumination and the gauge appearance is a good match for the gauges in the W123 dash.

Jeremy5848 · #18 09-27-2006, 11:35 AM

Quote:

Originally Posted by Ara T.

Interesting. Lemme know how much boost you get when you are going 70 mph and you give it 1/2 to 3/4 "throttle."

Ara, as I recall from going up the Cotati Grade, southbound US-101 from Rohnert Park towards Petaluma, the Boost gauge was sitting at about 5 psi going up the hill. More throttle pushed it up to 7 or 8. I would have thought it would have been higher.

gsxr · #19 09-27-2006, 03:12 PM

I got my AutoMeter gauges from eGauges.com also. I'd like to add the matching boost gauge to the right of the pyrometer this winter...

Jeremy5848 · #20 09-27-2006, 08:02 PM

I was surprised that the EGT gauge read so low and decided to run the thing through my calibration laboratory. (See photo) The thermocouple from the EGT gauge was placed in the laboratory oven along with a calibrated thermometer at least as old as the Benz.

I ran the oven to full power and compared the reading on the EGT gauge to the calibrated thermometer. The readings were in error by no more than 50 Fahrenheit degrees.

To calibrate the high end of the EGT gauge, I plan to use a Mapp gas torch, as soon as I find out how hot they get. As a cross-check, I'll be using a surface thermometer (range 50C to 400C) that I bought for our wood stove about 20 years ago. It attaches magnetically so I can stick it on the turbo or the exhaust manifold, wherever it will fit.

More scientific results as they become available.

Professor Jeremy

Jeremy5848 · #21 09-27-2006, 09:41 PM

This test used a Mapp gas torch to heat the thermocouple. First, I tried sticking the end of the thermocouple in the torch. When the meter got up to about 1000F, the end of the probe started to glow red. I thought that was a good place to stop, before I melted something.

Next, I clamped the thermocouple to an old piece of sheet iron. On top I placed the surface thermometer (50C to 400C) from our wood stove. This assembly was then heated with the torch (see picture). I read both gauges as the temperature rose. The paint on the sheet iron burned, smoking up the garage. The door to the house was open, so I stunk up the kitchen. My wife did not appreciate that.

The two gauges agreed best at the high end, where the surface thermometer's 400C is the same as the EGT gauge's 750F. At the low end, where we don't care so much, the gauges are off by 50 Fahrenheit degrees.

Based on these crude tests, the EGT gauge does seem to be accurate up to 750 degrees, perhaps 850. I'd like to test the gauge at higher temperatures but don't have a way to make a comparison.

This still doesn't explain why my M-B exhaust manifold runs so cool. Maybe it was just a cool day. When I get the gauge permanently installed, I'll take an opportunity to go for a longer ride on a warmer day.

networkboy · #22 10-09-2006, 06:43 PM

Quote:

Originally Posted by biobenz617

Has anyone ever thought of that pesky EGR port on the manifold for a place to put the thermocouple? I'm not sure if there are thermocouples out there that are long enough to reach to the exhaust stream though. Just a thought.

I'm sure there are

In fact I have a K type thermo couple on a 1 foot solid stem that I use for process monitoring, check out http://www.omega.com/ppt/pptsc.asp?ref=TJ36CAXL_NNXL&Nav=tema06
They've got tons of stuff.
-nB

Update:
This looks perfect: (K type is only $34)
http://www.omega.com/ppt/pptsc.asp?ref=TC-NPT&Nav=tema09
and an intro to thermocouples:
http://www.omega.com/thermocouples.html

biobenz617 · #23 10-09-2006, 06:44 PM

Quote:

Originally Posted by Jeremy5848

Now I can build them into the dash. Stay tuned!

Here is my suggestion for a home for gauges in a W123... http://www.peachparts.com/shopforu...d.php?t=147729 Splice into the radio connections for switched power and illumination.

Jeremy5848 · #24 10-09-2006, 08:25 PM

Quote:

Originally Posted by biobenz617

Here is my suggestion for a home for gauges in a W123... http://www.peachparts.com/shopforu...d.php?t=147729 Splice into the radio connections for switched power and illumination.

I got a "not found" error for your link. The radio connections indeed would work for power and illumination although the illumination on my radio doesn't dim with the gauges -- does yours? Instead, I used the cigar lighter wiring for power (after removing the ashtray the plug was ready for a new "job" anyway) and tapped into the ACC wiring for illumination.

My zebrawood panel now has three coats of Varathane over the stain but I am having trouble with tiny bubbles. I suspect operator error, I am probably holding the brush with the wrong hand or something.

Jeremy

bgkast · #25 10-09-2006, 08:34 PM

When I put my gauges in the ash tray location I used the power for the now missing cigar lighter to power them. I wired them to be constantly illuminated. Using the radio for the illumination is a good idea. Any idea what color the illumination wire is?

Jeremy5848 · #26 10-09-2006, 10:16 PM

Quote:

Originally Posted by bgkast

Using the radio for the illumination is a good idea. Any idea what color the illumination wire is?

The diagram in Braingears says green/violet.

biobenz617 · #27 10-09-2006, 10:39 PM

Search for "wood gauge pod for W123".

From the FSM, the illumination to the radio is black/red (and gray/violet?). I actually spliced into my HVAC illumination wires (gray/violet if I remember), since I was in there checking the light bulbs, but the radio is probably better, especially if you already have some wire work for an aftermarket unit. Good idea on the cigar lighter power, since this is also switched with the engine.

#28 10-09-2006, 10:51 PM

I just used the marker light wire on the headlight switch.

bgkast · #29 10-09-2006, 11:42 PM

Quote:

Originally Posted by Jeremy5848

The diagram in Braingears says green/violet.

I just pulled out my radio (it wasn't working) and discovered that I don't have many wires running to it (hence why it doesn't work, see "radio what the heck?")

Looks like it's time for plan B

Rudolphrocks · #30 10-11-2006, 09:07 AM

Quote:

Originally Posted by Jeremy5848

I got a "not found" error for your link. The radio connections indeed would work for power and illumination although the illumination on my radio doesn't dim with the gauges -- does yours? Instead, I used the cigar lighter wiring for power (after removing the ashtray the plug was ready for a new "job" anyway) and tapped into the ACC wiring for illumination.

My zebrawood panel now has three coats of Varathane over the stain but I am having trouble with tiny bubbles. I suspect operator error, I am probably holding the brush with the wrong hand or something.

Jeremy

Stain doesn't have dispersants like paint so if it gets shaken you need to put it thru a fine filter to remove the bubbles