build boost early and not change the tune? - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

bilydean · 06-07-2013, 12:33 AM

Most of the roots blowers out there have a vacuum pot that opens a valve under high vacuum conditions to equalize pressure and kill any boost. When you stomp on it and lose vacuum the valve shuts and you build boost. So here is the question.

What if you put a restriction in the vacuum line to the vacuum pot OR increased the spring tension to resist opening the valve, would boost build quicker and if so, would the tune that you have handle the boost coming on quicker (at lower RPMs)?

Dean

2SS45th · 06-07-2013, 02:13 AM

Most likely no, roots blowers rely on engine speed to drive the rotors, and this compresses the air. If anything you'd run the risk of blowing your motor by building boost when you are off throttle. Toyota blew many of their 4.6 v8s when they supercharged them because they built boost under vacuum.

Alvin@PCMofNC · 06-07-2013, 07:44 AM

It would slow down how the boost comes on. Magnacharger actually puts a little brass restricter in the bypass valve nipple. Removing it makes boost come on a bit quicker.

bilydean · 06-07-2013, 09:49 AM

Quote:

Originally Posted by 2SS45th

Most likely no, roots blowers rely on engine speed to drive the rotors, and this compresses the air. If anything you'd run the risk of blowing your motor by building boost when you are off throttle. Toyota blew many of their 4.6 v8s when they supercharged them because they built boost under vacuum.

If you are off the throttle, that creates a high vacuum condition so still no boost. What I am asking is if you are spinning 2000 RPM, you are making some kind of boost (not much), but the vacuum pot is keeping the valve open so the engine never feels the boost. The idea is to restrict the vacuum so the valve stays closed longer which allows boost quicker.

Dean

bilydean · 06-07-2013, 09:53 AM

Quote:

Originally Posted by Alvin@PCMofNC

It would slow down how the boost comes on. Magnacharger actually puts a little brass restricter in the bypass valve nipple. Removing it makes boost come on a bit quicker.

Maybe my understanding is backwards. Doesn't vacuum hold the bypass valve open? If so, how does removing the restricter, which I assume would allow more vacuum, allow boost to come on quicker? Your last statement is what I am after though. Not more boost, just to come on quicker.

Iam Broke · 06-07-2013, 09:57 AM

Removing the restrictor allows the vac to drop to the diaphragm faster upon WOT when the mani vac decreases (or in other words when absolute pressure rises), then it closes the bypass sooner. It will open quicker as well when vac increases.

SC2150 · 06-07-2013, 10:23 AM

Also whats not being discussed here is that bypass valve is critical to relieving pressure that can damage the gaskets/seals and or rotor bearings and shafts from the longitudinal stresses fighting the internals if not relieved. That's what bot a wastegate and BOV do with a turbo or centri blower.

Iam Broke · 06-07-2013, 11:30 AM

I wasn't proposing it was a good idea to do that mod, just how it changed the response of the bypass. Slamming stuff around is never a good thing.

06-07-2013, 12:33 AM	#1
bilydean Drives: One of the rare ABM camaros Join Date: Apr 2009 Location: Auburn, CA Posts: 455 View My Garage	build boost early and not change the tune? Most of the roots blowers out there have a vacuum pot that opens a valve under high vacuum conditions to equalize pressure and kill any boost. When you stomp on it and lose vacuum the valve shuts and you build boost. So here is the question. What if you put a restriction in the vacuum line to the vacuum pot OR increased the spring tension to resist opening the valve, would boost build quicker and if so, would the tune that you have handle the boost coming on quicker (at lower RPMs)? Dean __________________ 1100 4/28 2000 5/23 3000 5/27 3400 6/20 TPW of 6/29 3800 7/3 4D00 7/8 interned at QC 4B00 7/16 Released from QC 4200 7/20 8/5 We picked up the car

06-07-2013, 02:13 AM	#2
2SS45th Drives: 11 Seconds or Faster Join Date: May 2012 Location: Arvada, Colorado Posts: 2,797 View My Garage	Most likely no, roots blowers rely on engine speed to drive the rotors, and this compresses the air. If anything you'd run the risk of blowing your motor by building boost when you are off throttle. Toyota blew many of their 4.6 v8s when they supercharged them because they built boost under vacuum. __________________ I Ain't About That Stock Life.

06-07-2013, 09:57 AM	#6
Iam Broke PHAT B33 Drives: 2012 TF3 Camaro 2SS/RS M6 Join Date: Jun 2012 Location: Dark of the Moon Posts: 1,460 View My Garage	Removing the restrictor allows the vac to drop to the diaphragm faster upon WOT when the mani vac decreases (or in other words when absolute pressure rises), then it closes the bypass sooner. It will open quicker as well when vac increases. __________________ Another 1 of 371 '12 T3 LS3 M6's built.

06-07-2013, 11:30 AM	#8
Iam Broke PHAT B33 Drives: 2012 TF3 Camaro 2SS/RS M6 Join Date: Jun 2012 Location: Dark of the Moon Posts: 1,460 View My Garage	I wasn't proposing it was a good idea to do that mod, just how it changed the response of the bypass. Slamming stuff around is never a good thing. __________________ Another 1 of 371 '12 T3 LS3 M6's built.

06-07-2013, 07:44 AM	#3
Alvin@PCMofNC Drives: 2010 IOM RSS Join Date: May 2009 Location: Mooresville Posts: 363	It would slow down how the boost comes on. Magnacharger actually puts a little brass restricter in the bypass valve nipple. Removing it makes boost come on a bit quicker.

06-07-2013, 10:23 AM	#7
SC2150 Account Suspended Drives: 2012 Camaro RS, RX supercharged Join Date: Dec 2009 Location: Bradenton, FL Posts: 6,063	Also whats not being discussed here is that bypass valve is critical to relieving pressure that can damage the gaskets/seals and or rotor bearings and shafts from the longitudinal stresses fighting the internals if not relieved. That's what bot a wastegate and BOV do with a turbo or centri blower.