what doe's the bypass valve on the SC do?? - LotusTalk

carl · 04-11-2008, 03:21 PM

i need to better understand it. thanks carl

ChrisB · 04-11-2008, 05:34 PM

The bypass valve bleeds the boost off to the intake side of the SC. This is typically manifold vacuum controlled. It is there to reduce parasitic loss when boost isn't needed. It doesn't have anything to do with power.

carl · 04-11-2008, 05:55 PM

Quote:

Originally Posted by ChrisB

The bypass valve bleeds the boost off to the intake side of the SC. This is typically manifold vacuum controlled. It is there to reduce parasitic loss when boost isn't needed. It doesn't have anything to do with power.

Doe's it cause any increase in the pressure in the crankcase? carl

wildwhl · 04-11-2008, 08:48 PM

carl -

It would seem, to me, that when the engine is under boost, there would be greater crank case pressure. But what do I know, lol.

WW

2-Y-CHROMOSOMES · 04-11-2008, 08:55 PM

When enough intake passes thru ie;air it closes the valve and boost is on.
This why you can cruise with a supercharger it is not on boost ....but when you gun it the intake close the valve and it is boost on.

ChrisB · 04-13-2008, 01:10 PM

Quote:

Originally Posted by carl

Doe's it cause any increase in the pressure in the crankcase? carl

I don't see why it would. When the valve is open, the SC rotors are, basically, just freewheeling so the entire intake tract is the equivalent of an NA one. When the valve is closed, the SC is providing whatever boost it normally would at any given throttle opening, as though there was no bypass valve.

wildwhl · 04-13-2008, 02:38 PM

Just my humble opinion, but I believe increased cylinder pressure = increased crankcase pressure.

I know that on a previous vehicle of mine, the blowby went way up with the addition of an MP112, and dropped way down once it was removed (aka catch can is necessary and helpful in FI applications).

WW

ChrisB · 04-14-2008, 11:45 AM

Quote:

Originally Posted by wildwhl

Just my humble opinion, but I believe increased cylinder pressure = increased crankcase pressure.

I know that on a previous vehicle of mine, the blowby went way up with the addition of an MP112, and dropped way down once it was removed (aka catch can is necessary and helpful in FI applications).

WW

Agreed. My answer was to his question about whether the bypass valve causes increased crankcase pressure. Clearly any FI could.

wildwhl · 04-14-2008, 11:52 AM

Quote:

Originally Posted by ChrisB

I don't see why it would.

Sorry, ChrisB, I read this to mean that you didn't feel crankcase pressure would increase...my bad...

WW

04-11-2008, 03:21 PM	#1 (permalink)
carl Registered User Join Date: Oct 2005 Posts: 1,081	what doe's the bypass valve on the SC do?? i need to better understand it. thanks carl __________________ User formerly known as 4carl

04-11-2008, 05:34 PM	#2 (permalink)
ChrisB I'm Lovin' It! Join Date: Oct 2003 Location: Newport Beach, CA Posts: 3,970 Images: 1	The bypass valve bleeds the boost off to the intake side of the SC. This is typically manifold vacuum controlled. It is there to reduce parasitic loss when boost isn't needed. It doesn't have anything to do with power. __________________ '05 AR Mods: Stebel Nautilus horn; tesprit's rearview mirror; Custom Interior Pictures; PPF full front clam wrap

04-11-2008, 08:48 PM	#4 (permalink)
wildwhl You bought a Locust? Join Date: Nov 2006 Location: Reno, NV Posts: 782	carl - It would seem, to me, that when the engine is under boost, there would be greater crank case pressure. But what do I know, lol. WW __________________ ...................... She's gone.

04-11-2008, 08:55 PM	#5 (permalink)
2-Y-CHROMOSOMES Registered User Join Date: Jun 2006 Location: Silicon Valley Posts: 1,044	When enough intake passes thru ie;air it closes the valve and boost is on. This why you can cruise with a supercharger it is not on boost ....but when you gun it the intake close the valve and it is boost on. __________________ 2005 Elise 250 whp \| Forcedfed Custom Intercooled Supercharger \| EFI \| Forcedfed Street Header \| Fujita CAI \| TB Bypass \| Toda flywheel \| ACT HD Clutch \| Forcedfed Prototype Exhaust \| Micromirror \| Forcedfed Half Carbon Splitter \| Greddy Catch Can \| ForcedFed Engine Damper

04-13-2008, 02:38 PM	#7 (permalink)
wildwhl You bought a Locust? Join Date: Nov 2006 Location: Reno, NV Posts: 782	Just my humble opinion, but I believe increased cylinder pressure = increased crankcase pressure. I know that on a previous vehicle of mine, the blowby went way up with the addition of an MP112, and dropped way down once it was removed (aka catch can is necessary and helpful in FI applications). WW __________________ ...................... She's gone.

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