Dyno results - more torque, less boost (now with charts)

[edh]

Took the car to Weltmeister today to get the Vitesse MAF checked out - am away from home so will scan the graphs in at the weekend

Interesting results....good and bad

The good - boost is coming in earlier, by about 200 rpm, and there's consequently more power until 4500 rpm. Peak torque is up to 320lb ft at 4250 rpm, (was 315 @ 4600). AFR's also much better as the turbo spools up.

The bad - boost peaks at below 1.1 bar @ 3800 & then falls away (was 1.2 bar@ 4100). Peak power now 270 @ 4600 (was 285 @ 5250)

That might explain why I though the car was a bit flat at Silverstone in the summer & didn't really pull down Hangar Straight.

Time to play hunt the boost leak! - Chris's suggestion is the dump valve. IIRC this can be replaced by a 993 part no - is that correct?

 

[edh]

Here are the charts - blue lines are the new run. AFR goes rich at the top end, suggesting maybe metered air is leaking out.

I had a look at the car this afternoon - the diverter valve looks like an aftermarket metal one & seemed OK. I could open the valve by sucking on the top port, couldn't blow through the inlet or outlet

I found a couple of clips that tightened up a little, and one vac line that had come loose - off the 4-way connector on the inlet manifold. May get a chance to do some testing tomorrow & have got a second boost gauge fitted (might need a passenger to read it though). Vac at idle is OK