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The mkiv Supra Owners Club

Differential Pressure Measurement


Dragonball

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OK Guys / Gurus

 

That very nice man Mr Kindell has fitted my DEFI's for me - and lovely they are too!

 

However there is a section on the meter that allows me to measure differential pressure between the fuel and boost - that shows on the fuel pressure gauge

 

Not a scooby how this works / what it measures etc - something about 300kPs?

 

Any info gratefully received

 

Cheers

 

Paul

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Guest Martin F

The difference between boost pressure and the fuel pressure should equal the static rail pressure as long as you are using the normal 1:1 fuel pressure regulator.

 

I can't remember the static fuel rail pressure at the mo, but i think it's close to 40psi.

 

It's a good way to monitor whether your fuel system can support the level of boost you are running.

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Remember that at idle the engine is pulling a vacuum which will mena you're running lower the base fuel pressure. Pull the vac hose off the fuel pressure regulator and see what the gauge says then, that's your BFP (I think that bits right anyway!). Fuel pressure should rise directly in proprtion to boost pressure, ie at 0psi boost you have 40psi FP, at 18psi you should have 58psi. If your fuel pressure starts dropping off at high boost you need a better pump!

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The DEFI system actually shows the variance between the two automatically

 

I can either have it as fuel pressure standard - or set it so that it shows the correlation between the two (boost and fuel pressure)

 

The instructions show this as being 3.0 ideally (ie 3x100 should be the gap between the two)

 

At idle i am hitting 2.8 - and this has risen to 3.2 at peak

 

This should remain at 3.0 and the variance indicates that the fuel pressure falls behind at higher boost

 

Together with a EGT temp peaked at 1000 at 1.2 BAR (normal running 850/900 I am now going to do the following damn quick

 

1. Fit the UK fuel pump

2. Fit the new FMIC

 

Cheers

 

Paul

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Guest Martin F
Originally posted by Paul E

 

The instructions show this as being 3.0 ideally (ie 3x100 should be the gap between the two)

 

 

Do you know what units of measurement that is in ?

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