Hi just fitted a mechanical boost gauge to a classic and as i havent seen one working before am confussed to what im seeing, At tickover its negative which i understand, when i put my foot down it goes up to 1 bar which i know is ok but when i stay at a speed even though the revs are high ie staying at 70+ it goes back to a negative reading. Can someone say if this is normal, thanks for looking,

 

perfectly normal, means you've not got the turbo boosting

good to keep an eye on if your on a motorway, makes your fuel last a wee bit longer

 

just i thought if you were going at 70 + it should be positive

 

Not if you cruising on light throttle, negative tells you have a vacuum in the inlet manifold, a positive reading is when the turbo is producing positive pressure.

Try cruising at 70 on light throttle opening, and then plant your foot to the floor as the engine load increases positive pressure will be produced in the inlet manifold.

Hope this explains it.

 

I find the negative reading has 3 uses.

1) Lets you know you're not using any boost

2) Helps you drive a little bit more economically... if that's possible in a Scoob?

3) Helps you drive the car 'off boost' until the engine has warmed up.

J.

 

i'm about to have some defi turbo/oil temp and pressure guages fitted on the weekend. What sort of readings should i be getting (and looking out for!) with my oil temp. and pressure?