tt9714

Well I managed to crack off one of the hose fittings on my cycling valve ('86 951) last night. I was trying to remove the hose that goes to the wastegate, and apparently the plastic was very brittle from the repeated thermal cycles.

Has anyone bought one of these recently? If so, what is the dealer list price? I would want to buy a new one since any used/recycled part would have gone through the same thermal cycling as my old one.

Before you get too excited, I know that many of you would suggest replacing it with a manual boost controller and dual port wastegate. This is in the long term plan, but I really don't want to spend the extra $500 on the parts at this time. Besides, I want to update my headgasket to the Widefire design before adjusting boost levels.

Steve Cooper

In a pinch, I repaired a broken fitting on my cycling valvle with a copper tube. I drilled out the broken off fitting end slightly undersized to match the copper tube, then, with a bit of interference fit, pushed the copper tube into the drilled hole. Finished off with plastic expoxy, and voila, a hacked together but functional cycling valve.

It worked as long as it took for a new cycling valve to arrive, get returned for being faulty, and for a new replacement to arrive.

Still have that tribute to shade tree mechanics somewhere...

Cheers,

Rob

[quote] Has anyone bought one of these recently? If so, what is the dealer list price? <hr></blockquote>

I don't know dealer price, but they are about $80.00 from most places (zims, paragon)

[quote] I know that many of you would suggest replacing it with a manual boost controller and dual port wastegate<hr></blockquote>

Since you intend to go this way, why not just get a MBC and use it with your existing wastegate. Just set it for stock boost levels since you don't have chips to supply the fuel needed for more boost. These run from 50 to 100.

Rob

tt9714

Rob,
I like your idea:

[quote]Since you intend to go this way, why not just get a MBC and use it with your existing wastegate.<hr></blockquote>

I didn't realize this was an option. I thought that most MBC were just pressure regulators (i.e. no timing/cycling action). Would I just connect the MBC in line from the banjo bolt to the wastegate? What purpose do those 2 other vacuum lines to the cycling valve serve?

Rob

[quote] I thought that most MBC were just pressure regulators (i.e. no timing/cycling action). <hr></blockquote>

That's what they are.

[quote] Would I just connect the MBC in line from the banjo bolt to the wastegate? <hr></blockquote>

Yes, This way by adjusting the MBC, you set when the wastegate will open. IIRC, a non shimmed waste gate will start to open with as litte as 3-5 psi applied.

[quote] What purpose do those 2 other vacuum lines to the cycling valve serve? <hr></blockquote>

The cycling valve has 3 ports on it (essentially a 3 way valve) one port is hooked to the banjo bolt, the second to your wastegate, the third to your intake boot. when the cycling valve is open, boost pressure is applied to the wastegate, when the valve is closed the pressure in the line from the wastegate gets vented back into the intake boot. With an MBC, this will end up bleeding back through the controller.

If you add a set of chips, you can safely run this setup with boost pressure to 15lbs on the stock head gasket. Also, many have noted that their factory boost gauge is inaccurate. so if you start increasing boost beyond stock, you should get an aftermarket boost gauge.

Rob

tt9714

Rob,
Thanks for the excellent suggestion and explanation. That has taken the mystery out of the cycling valve operation.

I will be looking into MBC options soon.
-MDW