Im just wondering at what point the turbo kicks in so im not driving on and off it. I have the TDI Vrs which I amazing by the way.

You can feel the surge when it really starts to spin but I find it's kind of disguised to a degree by the DSG box, get her to kick down and you know it!

As to your question, don't really know but I'm sure someone can answer for you, doesn't it spin all the time?

Being an 'oiler' it will be very low down when it starts to make its presence felt.

I believe it's at 1750rpm same as the 150ps engine

An easy way to discover when it spools up is to trundle around on tickover in 3rd or 4th and then plant your right foot. The car will initially start to pick up speed very slowly, but as the turbo starts to spool up acceleration will noticeably pick up until you feel that full shove in your back.

I reckon full boost arrives 1850rpm (+-150rpm) and begins from as low as 1300rpm'ish. Normal relaxed daily driving sees me change gear at between 1600 & 2000rpm as that keeps the engine singing nicely. There is a tiny bit of boost drop off at the lower end of that scale but not enough to bother me.

Thanks. Im trying to find the best speed to drive at on the motorway so im not constantly on the turbo. Bit of eco driving. Even though I shouldnt.

Thanks. Im trying to find the best speed to drive at on the motorway so im not constantly on the turbo. Bit of eco driving. Even though I shouldnt.

 

Fuel economy on the motorway is influenced more by having a constant pedal position (thus constant torque request).

A diesel requires the turbo at all times for good combustion & fuel quantity is limited when at very low RPM (low turbo speed) to prevent excessive smoke.

Modern engines have variable geometry turbos which control the required boost pressure so you don't need to worry about "being on the turbo" like you would in a old petrol engine.

 

I see a very good fuel economy driving around 60mpg (>55mpg) with only a small decrease at 75mph (~52mpg).

You will find many other people with fuel economy in the mid 40s so it is very dependant on your driving style.

Managed 60mph on cruise control in sixth, 71mpg.... M25 J6-10 so few gentle hills.  Was amazed with that - never seen that high before.  Just hit 11k miles.

Fuel economy on the motorway is influenced more by having a constant pedal position (thus constant torque request).

This means having cruise control on uses more fuel?

Boost is not just about revs but revs and throttle position. The turbo will be spinning but the management system( waste gate on a petrol turbo car but not 100% sure it the same on a diesel) will be dumping available pressure as the engine is not needing it.

Steve

Boost is not just about revs but revs and throttle position. The turbo will be spinning but the management system( waste gate on a petrol turbo car but not 100% sure it the same on a diesel) will be dumping available pressure as the engine is not needing it.

Steve

So in turn your telling me I can get that chavvy ppppppst on my diesel vrs ?

Just stick your maxidot display on instant fuel consumption and find a speed/consumption compromise that suits you.

On cruise-control it will use more up hill and less down hill so it pretty well evens out overall.

I would not even worry about when the turbo is cutting in it will still be very efficient.

Edited 22 October, 201411 yr by Gerrycan

So in turn your telling me I can get that chavvy ppppppst on my diesel vrs ?

No I don't think so, that is made by the dump valve or blow off valve opening to prevent compressor surge as the throttle is closed, it's different to the waste gate valve. Since a diesel has no throttle valve, I doubt their turbos have a dump valve.