How does it know ???

[toyroom]

How does the car know what gear it is using ???? There is no gearbox sensor and yet there is no boost at standstill in neutral and reduced boost in the first three gears when driving. Full boost comes in with fourth and fifth, but not if the clutch is pressed. It is as if the engine knows when it is required to produce power and acts accordingly. I need to know this fact before I upgrade the engine as my gearbox now has dramatically different ratios to stock. ('97 V8 by the way)

[Le TVR]

IIRC theres a sensor VSS that gives the speed to the ECU and there's the revs.

Oh and a little maths..

Still negotiating on a V8, but learning all the time.

[toyroom]

Still don't understand how it knows you have your foot on the clutch at fifty in third !

[hast2]

Not enough exhaust gas pressure to overcome the turbo lag, in the short space of time that it takes to red line in neutral!

[toyroom]

OK, so I hold the gas pedal so that the rev counter sits at the correct speed for the road, don't know the exact figures but say fourth gear is equivalent to 3,000 revs at 60mph. So if I hold the gas so that the rev counter sits at 3,000 revs whilst the car is doing 60mph but with my foot on the clutch so that the drive is disconnected. The boost guage reads zero but let the clutch out and press the gas so that the rev counter reads 3,000 and the speedo 60mph, the boost guage will show .25 bar. The same is true at standstill. Press the gas pedal and hold the engine at 6,000 revs....no boost. Could the MAP sensor data be used to tell the ECM that the ....oh dear, I'm getting out of my depth, please help !

[hilly]

To get the engine to rev to 3000 RPM with no load (cluch peadel pressed) you will only need to just crack open the throttle plates. Shifting the car allong at 60 MPH requires a fair bit of energy so the throttles will be open a fair bit, therefore a large amount of air is moving through the engine.

With your foot on the clutch the engine just isn't pumping enough air to spin up the turbo, hence no boost.

Hilly

[toyroom]

HOOORRAY ! .......I understand !!!! Thanks ! Please now see " Will it work with the new gearbox"