Darien

Well, I've switched the vacuum sourse to the EZK and I've connected the pigtail. No change Although, I was looking around the SC snout support bracket and it was loaded with belt dust. The belt was feeling a bit loose, so I tightened it and cleaned off the belt dust. In the initial inspection, I was looking for belt dust due to belt slip all around the top of the engine.

Would belt slip cause the power leveling off?

Bill Ball

Yes. There should not be any belt dust. Too bad the dyno was not recording boost.

Tony

There was dust? I dont recall seeing any at the dyno?...that would be the OBVIOUS problem right there if there was?
After a 2" pulley on mine, i have seen my share of belt dust, i still have it all over my garage floor
hmmmmm..
tighten that SOB down some more and lets go again

I dont think i have ever seen dust from your belt Darien..in all the thrashing done?
You need a good quick responding analog boost gauge
next time on the dyno we will piggy back mine in again and i will watch it as you drive.

Darien

I remember you talking about all the dust everywhere under your hood, that's why I didn't think I had a problem But there was a thick layer of it just on the inside of the belt covering the bracket and mount bolts. Sure will be nice if that's all it was (fingers crossed)

I know, I need a good analog gauge

When's your filter kit due in?

Bill Ball

Yeah, I would have thought Tony would have noticed that as well. Hope that's it, but I would think the slipping would have to be pretty awful for a dyno curve like that. What I recall from when we progressively tightened the belt on George Suennen's setup, the boost and HP went up, but in the lower tension runs we didn't have a curve that fell on its face. There was just less boost and less power.

Darien

Just wishful thinking Bill I'm also going to change the coils with what Jim H is sending. They are the only part of my ignition that I haven't changed. I've still got other ideas from folks ready to try

MarkRobinson

Just Ohm-out the coils, that's all the manuals suggest.

Darien, any dust is probably an indication of slipping somewhere. In the past, I had belts that slipped & made dust, & others that didn't. Certainly tighten it some & try again.

Cam timing wouldn't allow "good power" in one gear & not another. Of course, even if all 3 ticks line up on the sprockets, that does not indicate that the intake cams are properly chained to the exhaust cams (as my last car wasn't). I'd bet money, that if Porsche did not do the top-end rebuild, this is probably the case since the ticks are very vague, as well, the cams were probably not dialed in correctly as well (dial-caliper) for each bank.

Brian G: the check-valve does nothing but prevent boost from entering the map: something the Map sensor would't see anyway.

Mark.