1994-2002 [Subscribe to Daily Digest] |
I installed my blowoff valve to be used as a pop off valve.
A popoff valve is used to blow off boost over pressures and can act as a safetly limit and also can be used to eat tranient pressure overshoots. I am doing this to be able to get closer to the fuel cut pressure than overshoots will allow. I currently have the MBC connected at the TB, a connection that can have very troublesome pressure overshoots. But they are not bad with hot weather and are quite reduced with the Viggen IC. So thios is all really a proof of concept thing and the results cannot be considred final until we get cold weather where overhoots can be very much a problem.
I used the 'manifold' that I made this weekend. It fits between the idle air control valve and side of the throttle body, on the top side of the throttle plate. This has a 3/4" branch for the popoff valve and a 1/4" brass hose barb to presurize the MBC. I put all 6 washers that came with the valve into it as spring shims and added 3 nickels with cost me exactly $0.15! I had to extend the longer downstream hose from the IAC valve back to the TB by 90mm. Everything fits quite well.
Went for a test drive, mo major pressure spikes, so all that I know now is that the popoff valve is not venting anything early. It is hot and extremely humid. Not the best conditions to go looking for pressure overshoots. I will increase the boost a little bit then start unloading the popoff valve spring until I find that I have a boost leak limiting full boost then see what I can do from there.
The metal work was quite difficult and time consumming. But it is a prototype. If this experiment is a success, then refined methods can be worked out. I will never bother to braze things like this again. With copper, the silver/tin lead free plumbing solder will do a much better job. I used that to make the extension piece tonight. It is 3/4" pipe with short rings solderd on cut from couplings whicj act as retension beads so things are blowoff proof.
It is nice to be doing some metal work, something that I have missed over the years.
posted by 65.68.100...
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