Lotus Elan

A question of balance

PostPost by: type26owner » Sat Jul 30, 2005 2:48 pm

My father had a precision Hg manometer filled with at least 10 pounds of the stuff in his study when he accidently broke the glass tube a few years ago. It was a huge toxic mess that took a couple of man-weeks to cleanup. I was able to borrow a mercury sniffer from the EH&S department at the lab where I work to use in finding every last trace. To shorten a long story up the last place we found it was it had coated the metal in the electrical sockets that were 18 inched off the floor. The wave of mercury had sploshed up that high against the walls of the room. The thing that really saved us was the floor was really dusty and the mercury was covered with it immediately so the toxic fumes were minimal. After having had that experience I want nothing more to do mercury manometers.

Though the only reason a Hg manometer works at all on a pulsating vacuum signal is it's density is so high that there is not enough time for it to move in the column quickly. Of course, that's ideal.

The thought of adding a port to attach a MAS sensor had crossed my mind though. I still have to port the air supplied to the bleed screws from upstream of the butterflies inorder to use the synschrometer. Either I drill throught the carb body or the trumpets for the port to attach the hose.
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PostPost by: mark030358 » Sat Jul 30, 2005 3:14 pm

Looked at your pictures on the Ferrari web site and the manometer certainly looks the business. Anyway, I noticed that the scale was of the manometer is in centimetres. Therefore if the average is say 25cm, then this equates to approximatley 10" hg, which is equivalent to the readings I have taken using my gauges.

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PostPost by: bill308 » Sun Jul 31, 2005 2:18 pm


You have a good eye and are absolutely correct. The scale is indeed in cm. The line divisions are every 2 cm.


Wow, 21 lbs of mercury?

The Motion Pro Deluxe Carb Tuner I use needs maybe a couple of ounces HG. You can see the little bottle it's shipped with here:


A non-mercury alternative, the Morgan Carbtune II, which I haven't tried, uses stainless columns and can be seen here:


While density does have an important effect in minimizing column motion in response to a pulsating signal, simple line restrictors, in the form of an of an oriface, can be even more effective in controlling this motion. The more restrictive the orifice, the less the column motion and the slower the column response. Pulsation magnitude with my current system is about +/- 1 cm in height. To my eye, it's pretty easy to compare the the 4-levels for the twin cam application and when 2-systems are placed adjacet each other, 8-levels are also easy to judge as for the 308 application. In practice, one doesn't even look at the numbers, only the relative column heights.

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