Engine and Transmission Tech

Those are really meant for open exhaust applications, as in drag cars.

True, the drag racers use that system but it's been around much longer than that.
The OEM's have been using it off and on since the 50's.
Even on a restricted exhaust system there is still a pretty healthy pressure differential there.
On an open collector the check valve serves as a flame trap to prevent crankcase fires.
On a muffled system it is needed for that as well as to filter out the unwanted positive pressure waves.
Hook one up with a vacuum gauge some time and you will be surprised at the vacuum level.
The more I think about it though the more I like the idea of electronic control.
The MSQ can easily be configured to run a valve into the blower hat. Something like the Ford ISC valve. A simple RPM switch would get it done.
Or if you really want to get all fancy a PWM output would give you full control. All you need to do is anticipate the crankcase pressure.
All the needed sensors are already in place.

Cheers
Fred

It's an intriguing thought. But I do already feel somewhat overburdened with electronic controls and I'm not sure of the advantages.

OTOH, currently a low vacuum signal opens the valve. This indicates that it will function somewhat like the old vacuum dashpot in that if the engine dies at idle it will let more air in. Whether that will keep it alive then depends on the fuel map but it can be set to go rich at base idle speed if the manifold pressure goes up (vacuum goes down). If that is done successfully this represents a positive result.

At WOT the valve is open. Inlet pressure is high, (The valve diaphragm really should be plumbed to the blower inlet, not manifold pressure, but perhaps light positive pressure will not hurt it. Certainly it will drive the valve open more quickly under boost.) and full flow is achieved for blowby. The amount of additional fresh air ingested will be determined by the inlet breather restriction. The crankcase will not be placed under significant vacuum as the vacuum signal applied across the system will be equal to the K&N filter element restriction and throttle body restriction so fresh air flow will not be a large factor.

At some value of manifold pressure the valve will crack and then progressively open wider as manifold pressure increases (vacuum drops towards zero). I do not currently know what that value is, but idle vacuum is 20", so that number will represent significant acceleration, power output, and therefore blowby. The fuel map can be tuned to account for this easily using the O2 sensor, the only remaining question I see is this: Will there be any point in the operating curve where blowby builds up before the valve begins to open? Worst case scenario, build up of blowby at high speed cruise in top gear, possibly on an incline. I believe the restricted bypass line can be sized to account for that, with the inlet restriction sized to relieve any additional pressure. Or it may not be a factor.

The restricted bypass line will handle fresh air circulation through the engine under vaccuum conditions, much like the traditional PCV valve does now.

It may sound complicated but it really isn't, since separation of the bypass line makes orifice sizing easier.

So what did I miss?

Incidentally, the heater valve is made of fiber reinforced plastic and should not see temperatures any higher than in its intended application. Considering it draws from the blower inlet it should in fact run noticeably cooler.

Jim



Edited 1 time(s). Last edit at 08/01/2014 03:31PM by BlownMGB-V8.

I Don't think that you missed anything Jim.
Your system is clever and thoughtful.
I do agree part throttle will be an issue. But you're going to need some seat time for that
So put on your rubber party pants and take her for a spin!

Cheers
Fred

Rubber pants, blown 340 LBC, and the "Dragon", kinda ...flow together ? Enjoy, roverman.