Hose Diagram for D-Jet Decel Valve is Wrong

[pbanders]

See my posting here:

http://www.914world.com/bbs2/index.php?showtopic=67150

Sorry for redirecting to another board, but with 3+ boards on 914's these days, it's kind of a mess. I just wanted to make sure people saw this.

[Dave at Pelican Parts]

Brad, thanks for being meticulous and actually testing these things out!!

--DD

[pbanders]

Originally posted by Dave at Pelican Parts
Brad, thanks for being meticulous and actually testing these things out!!

Thanks! I encourage you to try it out yourself, as always, I could be wrong about this - but I don't think so.

I don't know if you saw the discussion that I started on the decel valve on 914club before the group was shut down and then split, but I kept asking - given how the valve is hooked up, how can it do what it's supposed to do? I got a lot of theories, such as "delayed pressure waves" and such, but nothing that explained how it actually could limit vacuum if connected as shown. One person did suggest to connect it the correct way, but I was stupid and didn't try it, because I couldn't believe all the diagrams could be wrong.

What I'd like to find now is a 914 decel valve that's working and hasn't ever been "adjusted". I'd like to know what the correct setpoint is for opening, so I could include this information into my D-Jet parts page. I it's something like 17 inHg, based on what I've seen with cold and warm idle intake manifold vacuum levels on my freshly-rebuilt motor, but it would be nice to know what the spec level is.

[Bleyseng]

I'll send you one along with the MPS's for testing Brad.

Thank God I didn't do those wrong diagrams! Leading all those guys down the wrong path for years DD.

[pbanders]

Geoff, thanks! Hey, DD has good company, even the factory manual shows it that way.

Now that my decel valve is working - for the FIRST time in my 24 YEARS of owing this 'freakin' car, it's obvious, the engine speed drops quite slowly to idle. It's not hard to see why many people removed it, as depending on the setting, it can significantly decrease engine braking. For me, I prefer it, as it helps contribute to less idle variation.

[pbanders]

DD - while I have no doubt that this is the right way to connect the valve, I'd like to have a few more owners verify it before the drawing is updated. Can you try it with your car?

[Dave at Pelican Parts]

I don't know when I'll be able to try it out. I am very reluctant to do anything to it right now, as my other car is down (waiting on parts). I have to get that back together so I can still get to my real job, and then we'll see about messing with the blue car...

--DD

[Bleyseng]

Brad, you have all the correct hoses and connectors on your engine? Including the pictured rubber elbow?

Post some pics of your engine!

I removed the decel as I started AXing and it hurt my driving due to the lack of engine braking....so off it came.

[pbanders]

Originally posted by Bleyseng
Brad, you have all the correct hoses and connectors on your engine? Including the pictured rubber elbow?

Post some pics of your engine!

I removed the decel as I started AXing and it hurt my driving due to the lack of engine braking....so off it came.

I'll post some more pics soon, there are some up on my web page towards the bottom of the pictures section.

I've got a stacked vacuum elbow - but I've got an issue. Some time ago, I realized I have the wrong plenum in the car. It's identical to the right one, except for one feature - instead of having a 12mm fitting for the stacked vacuum elbow, and a 9 mm fitting for the decel valve, I have a 9 mm fitting and a 5 mm fitting - it's probably an early 1.7 plenum. Otherwise, it's identical. Because it lacks the 12 mm fitting, I can't use the vacuum elbow. Instead, I've concocted my own setup - I run the 5 mm to the decel valve, use a short 9 mm hose to connect to a tee which splits off two 12 mm hoses to the decel valve and the PCV valve. Ugly, but functional.

When I got my motor rebuilt, I completely forgot that I had bought the "correct" plenum and had it in my parts bin - so, next time I rip it all apart, I'll update it and use the elbow that's been sitting in my parts bin along with the plenum.