ECU boost control question

[decker2]

I gather from reading around that boost is limited in 1st and 2nd gear to ~7 psi and if the ECU is happy it will operate the TVSV in higher gears which will bleed off ~3 psi before the waste gate actuator giving boost of ~ 10 psi. (MK2 REV2)
My question is, how does the ECU know what gear is selected? no sensor / no related ECU pin? is it perhaps in fact based on the road speed?

Thank you in advance

[tsango]

Never heard this before.

I know boost is limited when the car is cold (standard setup).

[markstevieandmads]

I've got a basic manual boost controller set at 0.8 bar when warm.
I find when its cold it only boosts to.about 0.2.

Is this right or.do I need to disconnect anything?

[jon]

The ECU estimates which gear it's in by taking the engine RPM and dividing it by the road speed. The result is inversely proportional to the gear selected.

[Peter Gidden]

I've got a basic manual boost controller set at 0.8 bar when warm.
I find when its cold it only boosts to.about 0.2.

0.2 bar = 2.9 psi. You have a problem somewhere.

[markstevieandmads]

I've got a basic manual boost controller set at 0.8 bar when warm.
I find when its cold it only boosts to.about 0.2.

0.2 bar = 2.9 psi. You have a problem somewhere.

Its prob more like.0.5 bar but it is limited until it warms up. Maybe a good thing so I can't thrash it when its cold.

[Peter Gidden]

I've got a basic manual boost controller set at 0.8 bar when warm.
I find when its cold it only boosts to.about 0.2.

0.2 bar = 2.9 psi. You have a problem somewhere.

Its prob more like.0.5 bar but it is limited until it warms up. Maybe a good thing so I can't thrash it when its cold.

The Rev1/2 ECU limits boost from 10psi to 7psi until warmed up.

I'm interested to know how your MBC limits boost when cold.

[Peter Gidden]

Its prob more like.0.5 bar but it is limited until it warms up.

Well that is 7psi. Which is normal.

So 0.2 was just a red herring.....

[markstevieandmads]

So all normal then? Good.

[ashley]

Why would you try to drive on boost with a cold engine?

[markstevieandmads]

Why would you try to drive on boost with a cold engine?

I don't usually, however the one time I did I noticed the lack of higher boost - hence why I wasn't too sure on the reading.