Polo 4.2 V8 Transplant

Started by Lee, April 22, 2009, 08:33:11 PM

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Lee

#200
And if you thought the last engine was tight --this is very frustrating.
And there is so many things to go wrong. It's like 3 steps forward and 5 back
However a granny car it will be


spooln

Wow exhaust. 4+4 into 2 into 1. :o
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dubstar

Holy Tap Dancing Christ, thats awesome
"I am so clever that sometimes I don't understand a single word of what I am saying."

RS ZWEI

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BB

Talks softly but carry's a big gun.
The end is nigh, but the end of what is the question?

DubMan


Lee

Small update.

It runs----------------

Still a lot of work to do yet-- but I'm getting there.

Small technical problem I would appreciate some opinion on--

As you are aware the intake system is --throttle body--supercharger--intercooler--intake to engine

I have also installed a Forge type vacuum operated bypass valve after the throttle body with a 25mm pipe to the main manifold.

In theory-- at idle or cruise the bypass should be open and air should be bypassing the blower.

So the problem--

The motor starts and idles at 3k rpm but when the vacuum line is pulled from the bypass valve the revs drop.the vacuum line is sucking air.

When I block and unblock the pipe the revs rise and fall just like operating the throttle-- I have checked for air leaks but have found none.

Any thoughts as to what is happening??




80 Vert

Bypass valve should be before throttlebody
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2003 Jetta Coupe soon to be R36TT
1991 Golf GTI 2.0 TSI swapped
1963 Type 34 Karmann Ghia, turbo 2.0
1990 Porsche 964 911 Carrera 4
1980 1303 Beetle vert, under restoration

Lee

The throttle controls the amount of air introduced into the engine---as I understand it you cannot bypass in or out before the throttle body.




80 Vert

All turbo and S/C cars have bypass valve before throttle body not after.
2019 Jetta GLI (USA)
2003 Jetta Coupe soon to be R36TT
1991 Golf GTI 2.0 TSI swapped
1963 Type 34 Karmann Ghia, turbo 2.0
1990 Porsche 964 911 Carrera 4
1980 1303 Beetle vert, under restoration

ritmo

Are you sure Vert? Bypass by its very
Nature is suppose to let air in when TB is closed. So has to be plenum side.

00quattro00

When you close the throttle it dumps the air between the throttle body and engine back infront of the throttle body
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80 Vert

#212
We are talking about a bypass valve as in blow off valve yes?
If so then when the throttle snaps shut vacuum is created which opens the valve to bypass air back to the inlet side of the turbo or S/C.
This valve is always before the throttle body, have never seen it any other way.

Edit, just seen your set up is different........
2019 Jetta GLI (USA)
2003 Jetta Coupe soon to be R36TT
1991 Golf GTI 2.0 TSI swapped
1963 Type 34 Karmann Ghia, turbo 2.0
1990 Porsche 964 911 Carrera 4
1980 1303 Beetle vert, under restoration

ritmo

Ok bit of confusion here... I was thinking idle control valve as opposed to blow off valve. Which bypasses TB.

mark2 golf

Johns right it should be in front of the TB. It will be very hard to get idle control with it there. Are you running a Air flow meter?
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Lee

The Link computer uses data from throttle position and air mass from within the manifold --

so no there is nothing before the throttle body other than the air cleaner.

5-pot

The bypass valve should be introducing an air circuit from the TB straight to the intake, removing the blower and intercooler from the circuit.

The TB still has to meter the air going to the valve/intake so, the bypass needs to be after the TB right? 

So, it should kinda sound like Throttle body - bypass intake - blower - intercooler - bypass outlet - intake manifold.

That's my 2c's worth
?The bravest are surely those who have the clearest vision of what is before them, glory and danger alike, and yet notwithstanding, go out to meet it.? - Thucydides (Ancient Greek historian and author, 460-404bc)

- 1990 Coupe quattro - R.I.P.
- 1988 90 quattro project... Sold
- 2005 Golf 2.0 TDI

ranton-inc



This is the way i kinda understood it....

5-pot

I don't think we're talking about a blow-off-valve here.

He wants to bypass the blower at idle/cruise, not dump excess boost pressure in the intake tract.

Unless I'm thinking about this the wrong way.
?The bravest are surely those who have the clearest vision of what is before them, glory and danger alike, and yet notwithstanding, go out to meet it.? - Thucydides (Ancient Greek historian and author, 460-404bc)

- 1990 Coupe quattro - R.I.P.
- 1988 90 quattro project... Sold
- 2005 Golf 2.0 TDI