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Discussion Starter · #1 ·
Anyone here done this it does not look that hard. I was thinking of using a bosch style bypass with 1 inch heater hose. The tricky part is taping into the intake.
 

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Discussion Starter · #2 ·
No one has tried this.
 

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Well normally,there isn't a need to on the 1.5,but since you're currently overspinning it,it couldn't hurt.Tapping into the manifolds is cake,welding is a different story.Take the manifolds off of the compressor,buy two 3/4" pipe thread fittings,and drill bit.The best place to tap into are on the side of the vac taps inlet side,and in place of the top vac tap on the discharge,this will leave you with only two vac fittings on the discharge,but you normally only need two anyway.Once you have the pipe thread fittings installed,and manifolds cleaned,bolt them back on,and reinstall the blower.Then install the bypass with the heater hose,or chrome plumbing pipe with reducers,and tee into your vac line.It should only take you a few hours to do,and you'll shed about 20* of heat soak at idle,........but that all depends on what boost level you are running.
 

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'87 Cougah 428W - ⚡Cougar7.0⚡
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92rohcp said:
Anyone here done this it does not look that hard. I was thinking of using a bosch style bypass with 1 inch heater hose. The tricky part is taping into the intake.
Well, you can't use a Bosch style bypass valve - when open there is no pressure to hold the valve open. You have to use the one sold by Eaton.

Here is a picture I made of my custom bypass on my 1500:




Here is the change in 50 MPH cruising temp. - same day, same stretch of road, one time with the valve disabled, second time with the vacuum line re-attached. The blower was only pullied for 6 psi at the time!:



Here is a rudimentarty Bill of Materials and instuctions for building a custom bypass:



Hope this helps :D
 

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Discussion Starter · #5 ·
Thanks for the great info. You did a very nice job. I am not clear though on why a standard bypass valve won't work. The bosch style uses vacuum to open it and hold it open, when the vac is gone and boost is present it closes. I tested mine on my vortech system. It should be the same principle.
 

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92rohcp said:
Thanks for the great info. You did a very nice job. I am not clear though on why a standard bypass valve won't work. The bosch style uses vacuum to open it and hold it open, when the vac is gone and boost is present it closes. I tested mine on my vortech system. It should be the same principle.
Well, I thought the same thing and even bought a nice billet one. I even tried to hook it up even after I realized that it wouldn't work! Here's why it won't work:

A standard bypass/blowoff you might see in a centrifugal/turbo system goes on the high side of the blower. If it's a blowoff it vents to atmosphere, if it's a bypass it vents back to the inlet. Anyway, the piston in the valve is held closed with a spring when there is no vacuum on the vacuum control line. Where the valve is there is never a vacuum, atmospheric pressure is as low as it sees because it's before the throttle body.

So in a Vortec or turbo system, when there is boost, the valve is closed and may even be held closed tighter by the boost pressure on the vacuum line. When you let off the gas, the engine vacuum after the TB opens the bypass/popoff through the vacuum control line.

In a KB setup, the bypass goes from the high side of the compressor to the low side, BUT the low side is after the throttle body. When you let off the throttle in a KB system, you see a vacuum on both sides of the compressor. The Bosch style bypass is just a piston with one side referenced to the vacuum control line, and the other referenced to the bypass air, but the bypass air is a vacuum as well. So, no pressure across the piston, therefore it never opens, the internal spring making sure it stays closed.

The Magnuson valve which was designed for PD blowers (and is/was used by KB for their bypasses) looks like a mini-throttle body. It has a vacuum control diaphram unit that pulls a mechanical linkage that opens and closes the throttle plate within the valve. This is the type of valve you need with a positive displacement blower. I didn't want to believe it was true so I experimented quite a bit with the Bosch style valve, then I sold it on Ebay and got the Magnuson valve. :D
 

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Discussion Starter · #7 ·
Wow you are good!. I thought I could stump you LOL... How about this I'm really thinking now! What if I was to vent the bypass before the throttle body instead of tapping into the KB inlet manifold I would vent into the inlet tube between the TB and MAF.
 

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92rohcp said:
Wow you are good!. I thought I could stump you LOL... How about this I'm really thinking now! What if I was to vent the bypass before the throttle body instead of tapping into the KB inlet manifold I would vent into the inlet tube between the TB and MAF.
Hehe - I thought of that for a minute too - but when the valve opened, a ton of air would rush past the throttle body into the engine. It would rev up, lean out and blow up! Well, probably not blow up, but you can see it would be a bad situation. :D
 

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Discussion Starter · #9 · (Edited)
You got me again man. I think the problem would be with that is when the TB is clsoed vac opens the bypass valve and air rushes into the inlet pipe the air will have to go somewhere and with the TB closed it will rush out the MAF causing problems there.

I checked that site for the bypass and can't seem to find a dealer from there list who sells them. Can you help me out there.
 

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Discussion Starter · #10 ·
Man I'm getting confused now how can the KB have vac on both side when you let off the gas. If this is true than why would you need a valve at all to bypass if there is no boost on the compressor side on decell. No need to devert right or wrong.
 

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there's always boost present if the compressor is spinning,it stores it in the case,which causes blower and engine heatsoak,along with severe heat transfer upon evacuation.
 

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92rohcp said:
Man I'm getting confused now how can the KB have vac on both side when you let off the gas. If this is true than why would you need a valve at all to bypass if there is no boost on the compressor side on decell. No need to devert right or wrong.
Yep, compressor is always compressing, even when no boost shows due to throttle body is not supplying enough air. Would you rather pull the air through the compressor or through a bypass valve? You did see the 17 degree reduction I saw at a cruising speed of 50 MPH (vacuum in intake) with bypass connected/disconnected. I had all the same thoughts as you when I was fabricating my bypass :D It's a normal process, you will see the light eventually :joy: Even the compressor maker (Opcon) gives you a sheet with a diagram of where to install the bypass - KB followed the directions correctly :lol:
 

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Discussion Starter · #13 ·
Wow this has been a lesson. This is half the reason I'm changing from a Vortec to the KB I want something different and the KB set up is. I also don't race and drive very short distances with my car around town so again the KB should be more fun.
 

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Discussion Starter · #14 ·
Cougar5.0 ever thought of bypassing that air through a small intercooler. I wonder if there would be benefit there. Maybe if the bypass system was a full inch it could have some benefit. I don't know just a thought bypass and intercool all in one.
 

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92rohcp said:
Cougar5.0 ever thought of bypassing that air through a small intercooler. I wonder if there would be benefit there. Maybe if the bypass system was a full inch it could have some benefit. I don't know just a thought bypass and intercool all in one.
I have thought of that actually. I noticed that the bypass pipe was blazing hot even tough it is insulated from the hot metal by the hoses. I was going to cut in an old heater core and measure the results by doing back-to-back runs with and without bypass and I could compare delta T to back-to-back runs without the added cooling. Unfortunately I don't have infinite time to do these things :lol:. I did make a custom H2O/Methanol/Ethanol injection set-up - it really staves off the detonation and I think it even adds power when I use a 30%-35%-35% mix of Water-Methanol-Ethanol due to the added oxygenated fuel - though don't quote me on that, I'm still learning. :D
 

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Discussion Starter · #16 ·
How do you control the water/meth at what boost and does it very or all at once.

On the bypass intercooler I found a small intercooler on ebay for $99 and I am thinking of using greddy type 1 1/2 in flange on the flat part of the discharge. I think black 1 1/2 inch heater hose would work to route to the intercooler mounted in the front bumper. I'm not sure it matters ether how long the hose. What do you think.
 

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92rohcp said:
How do you control the water/meth at what boost and does it very or all at once.

On the bypass intercooler I found a small intercooler on ebay for $99 and I am thinking of using greddy type 1 1/2 in flange on the flat part of the discharge. I think black 1 1/2 inch heater hose would work to route to the intercooler mounted in the front bumper. I'm not sure it matters ether how long the hose. What do you think.
I think you're going overboard! The heat from the engine and from the compressor making boost will still heat things up a lot - all the bypass cooling would do is lower the temps while cruising - this may help some under boost, but it may not be as much as you would think.
 

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Discussion Starter · #18 ·
Cougar5.O said:
I think you're going overboard! The heat from the engine and from the compressor making boost will still heat things up a lot - all the bypass cooling would do is lower the temps while cruising - this may help some under boost, but it may not be as much as you would think.
Yes I agree that it won't work like intercooling the boosted air. It has to have some positive effects though, just how much is the question. I think its worth a try as its only $120 shipped for the intercooler. Bypassing superheated air back into the compressor is not a good thing, I'm sure we all agree with that.

:confused: It seems though the only time the bypass system can work is when the throttle plate is open, but only like when crusing. When the thottle plate is closed, and decelerating from a hard blast wouldn't both sides of the blower be in vac thus defeating the bypass system. In other words no circulation through the byspass. I see the KB system like this. When throttle plate is closed its like taking a shop vacuum and putting your hand over the suction end. The entire system becomes starved of air and both sides would be in vacuum right. This is much different than a blower like Vortech. Where the bypass system is before the TB, which will bypass air regardless of throttle plate position. I know this is as clear as mud. Help me out here. Am I getting this, or am I digging my hole deeper.

I do see now that the KB is unlike the centrifugal and does not have the same needs for a bypass. Because the KB when decelerating and throttle plate is closed still has the engine pulling air from the discharge side.

O.K enough! I'm posting this crap my brain hurts.
 

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Discussion Starter · #20 ·
Thanks I'll keep that in mind.
 
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