Supercharge a 4BD1?

**Dougal** · 22nd February 2011, 11:53 AM

Originally Posted by isuzurover

Has anyone yet mentioned that the mass flow out the exhaust is always higher than the mass flow through the intake.

I don't think it's a big enough difference to matter.
At 20:1 AFR yes you gain another 5% mass from fuel, but we lose several percent in blowby which doesn't make it to the exhaust.

Is there anyone here with a spare boost gauge who would like to take some EMP measurements?

**85 county** · 22nd February 2011, 04:36 PM

Dougal--- OPS

You are quite correct, i read of his info incorrectly

However, his chart shows a dip in turbine pressure to a point equivalent to his compressor pressure. this chart is not applicable to us. firstly because it is a waste gate equipped turbo that is controlled by and ECU. The dip in turbine pressure is due to the waste gate dumping gas and then being rained in by the ECU

**Dougal** · 22nd February 2011, 04:52 PM

Originally Posted by 85 county

Dougal--- OPS

You are quite correct, i read of his info incorrectly

However, his chart shows a dip in turbine pressure to a point equivalent to his compressor pressure. this chart is not applicable to us. firstly because it is a waste gate equipped turbo that is controlled by and ECU. The dip in turbine pressure is due to the waste gate dumping gas and then being rained in by the ECU

I haven't read through the finer details of his setup, but those VW's normally come with a variable vane turbo which is ECU controlled. It's the computer moving the vanes that you're seeing on the graph as backpressure dropping quickly.

So yes quite different to the average 3.9 landrover setup and consequently his results look very different to mine. For example on an acceleration run like the one he has mapped out I couldn't get boost above backpressure, I can only get over 1:1 under steady high load (i.e hill climbing) at low rpm.

The more efficient your turbo setup, the bigger that sweet-spot becomes. With a poor performing turbo you might not get there at all.

**85 county** · 22nd February 2011, 05:32 PM

Originally Posted by Dougal

I haven't read through the finer details of his setup, but those VW's normally come with a variable vane turbo which is ECU controlled. It's the computer moving the vanes that you're seeing on the graph as backpressure dropping quickly.

.

Logical but not quite. the waste gate dumping pressure the variable vane seems only to be used when in cruse mode. Sort of coarsens the pitch to increase back pressure in an attempt to cut down on N emissions, works in conjunction with the EGR.

I down loaded a couple of maps. interesting as it was not what i expected. I defiantly expected the VV to have a larger effect than it appears to have in this instance

**Dougal** · 22nd February 2011, 06:30 PM

Originally Posted by 85 county

Logical but not quite. the waste gate dumping pressure the variable vane seems only to be used when in cruse mode. Sort of coarsens the pitch to increase back pressure in an attempt to cut down on N emissions, works in conjunction with the EGR.

I down loaded a couple of maps. interesting as it was not what i expected. I defiantly expected the VV to have a larger effect than it appears to have in this instance

Variable vane turbos have no wastegate and that's not how they work.

The vanes are used to regulate boost by changing the angle of the stream into the exhaust turbine. It's the same result as a variable A/R exhaust housing.

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