Tim wrote…

I have a major increase in air flow , pressure(relieved by relief valve), and noise when I select cabin heat or defrost air.  Should this air be reduced by venturis in warm-side pressure hoses from the intecooler?

 

Tim, the IV-P is supposed to have sonic nozzles mounted where the air is ducted from the turbo-to-intercooler pipe. The early models mounted this nozzle in the pressurization feed lines, with SCEET tubing on either side of the nozzle. I followed the lead of later airplanes and welded the sonic nozzles directly to the side-mounted intercoolers and ran the SCEET tubing from the nozzle to the mixer box. If you don’t have these sonic nozzles installed, I doubt you’d be able to generate the 38.5 PSI of boost needed to get full power from the engine, so it’s likely they are there; perhaps not where you’d expect to find them?

 

It is normal for the cabin to receive more air and heat when the proportioning valve (the gold coffee-can distribution box on the upper engine side of the firewall) is switched by the heat knob to send only the air coming directly off the turbos into the cabin. The “cool” side of the distribution can takes air that has passed through the side and front-mounted intercoolers, thereby reducing both the temperature and the pressure. You should definitely be able to tell the difference.

 

Hope this helps!

Bob