Random boost levels, and poor MPG

[freddie2020]

Second post tonight, Golf MK6 GT TDI 140 Manual 107k

I find the amount of low down boost is very random, sometimes very punchy other times just nothing. Had the vacuum checked and all OK.

Just comparing to MK5 GT TDI, which was always punchy, and did 55 MPG average. The MK6 had random levels of boost, random average MPG and also idle's abouve 1000 rpm most of the time.

The previous owner of my car had the Diesel Gate remap done? Is this all related?

[annodomini2]

Mk5 is PD, Mk6 is CR.

Very different engines.

PD uses overfuelling to compensate for an off spool turbo, but at the sake of emissions. (As far as I understand, please correct me if I am wrong)

PD can raise fuel pressure higher and faster than a CR engine, so it feels more punchy.

Mk5 is Euro4
Mk6 is Euro5, so would have to meeting different emission standards.

Additionally the EA189 engine was the focus of the emissions scandal, so it may have had the 'fixes'.

[Drive Blind]

have you driven any other VW group CR's to compare?

The PD's do drive differently to the CR's and the PD torque spike at about 1700rpm would be one of the major differences.

[freddie2020]

Hi,

Only CR I have driven is mine, I have been a friends 2.0 TDI CR 140, asked to accelerate fully in second, and was way more punchy than mine.

I understand the PD's are more punchy than the CR's but the differance is so great, it make me think something is wrong with my engine

I guess a quick REVO might solve? Get rid of the rubbish VW emissions fix software, and with the map might be even more punchy than the standard PD

But if mine feels so weak already, could it be the turbo? Cannot see why, only 107k, done oil every 10k and try not to rev of 2k till warm.

Thanks

Edited by freddie2020 on Saturday 15th February 18:48

Edited by freddie2020 on Saturday 15th February 18:51

[annodomini2]

Have you had a fault code read?

Not all faults illuminate warning lights

[AJB88]

Idline above 1,000rpm suggests DPF is cleaning itself a lot, lots of short journeys?

As said though one is a PD which was known to be very punchy, the other is a CR which are smoother.

[freddie2020]

Yep, no fault codes, had it checked by my local VAG specialist.

It is a bit random, sometimes OK, sometimes so bad you think there is a vacuum fault and the accuator not moving. But the car was in anyway last December for a vacuum leak, so that should be fine anyway.

[freddie2020]

AJB88 said:

Idline above 1,000rpm suggests DPF is cleaning itself a lot, lots of short journeys?

As said though one is a PD which was known to be very punchy, the other is a CR which are smoother.

Main journey are 22 miles to work and back. With long runs on the weekend.

I used to think the boost issue happened at the same time as a DPF regen, but not correlated

[freddie2020]

Could it be linked to the brake servo?

VAG specialist thinks the servo is on the way out, as the brakes are a bit hard, compared to when newer.

Just blue sky thinking, but as the servo and accutor use the same vacume system, might this be linked in any way?

[AJB88]

Do some boost logs, get OBD Eleven (it works on Android, think iOS as well now) its about £50.

[Tame Technician]

Put a vac gauge on the main vacuum supply from the tandem pump. Should be 100mb absolute or 900mb of vacuum.

Then check it at the turbo when the N75 is activated should be very close to the same maybe 700mb vac. Any less you have a vacuum leak.