Air Flow Readings

[Red LCR TDI]

Hi there, having some airflow problems!

just run the car through diagnostics, and my airflow readings were 400 at idle and 340 at 5500rpm, but this should be somewhere like 800 at full throttle no?, but does this automatically point to the MAF or could it be a broken vacuum hose.

I've seen all the warnings about K&N induction kits, but unfortunately after i fitted it. obviously K&N are saying its not their fault and i cannot prove otherwise, but am worried about when i replace the MAF that it will happen again. K&N say i should stick with their kit,and insist i was just unlucky and i dont really want to sell it for half the price seein as i only fitted it 1 week ago and it does sound good.

anyone know how i can preserve the MAF but keep the kit? maybe try moving it away from the sensor?

 

[prc]

MAFs come and go even on cars running stock paper filters. Yes the K&N uses a bit more oil making it more prone to causing problems, but most problems come from over oiling any of the washable filters.
BTw you don't measure the MAF reading at 5500rpm, that's well within the 4750 redline. It should read about 360g/sec at idle (this value rises if you leave it idling too long). If your logging the car it should read around 1050g/sec (anything over about 900g/sec is OK) when the rpms pass 3000.

 

[Red LCR TDI]

thanks paulo,

was the guy in the shop revving the nuts out my car, not me. so when its fixed should be looking at 900 to 1000.

also, the K&N guide says you should unplug the battery for 15mins to allow the ecu to adjust to the new kit when you plug it back in, surely the MAF would read the extra air anyway? as the guy in the diagnostics centre said you shouldn't unplug the battery as it has a CAN bus?

its going to the garage tomo to get a new MAF (fingers crossed) under warranty,

should i bother unplugging the battery or is doing that pointless/damaging to the electrics on the car?

 

[prc]

your not going to damage the car, but personally don't think it's worth it. It's very difficult to read just reving the car stopped at the local garage. With VAG COM logging a running (not chipped) car: flat out in 4th your actual reading should be around 1000@3000.

 

[Red LCR TDI]

need to find someone with vag com and a laptop near portsmouth then as i dont think the garages big ass computer will fit.

also, know anyone near portsmouth to get a decent custom exhaust, the standard tdi one doesnt look anywhere near right hidden away underneath the cupra r kit!

 

[sssstew]

thanks paulo,

was the guy in the shop revving the nuts out my car, not me. so when its fixed should be looking at 900 to 1000.

also, the K&N guide says you should unplug the battery for 15mins to allow the ecu to adjust to the new kit when you plug it back in, surely the MAF would read the extra air anyway? as the guy in the diagnostics centre said you shouldn't unplug the battery as it has a CAN bus?

its going to the garage tomo to get a new MAF (fingers crossed) under warranty,

should i bother unplugging the battery or is doing that pointless/damaging to the electrics on the car?

i would say no, dont bother. As far as im aware its an adaptive ecu so will take into account the extra air straight away.

And as paulo has said i wouldnt do maf logging revving the nuts at standstill i would do them under load foot flat down in 4th on an open road, compare requested vs actual and see whats up.

 

[Red LCR TDI]

Have finally had the MAF sensor changed under warranty, and the car is running loads better!

the car seems to be fueling alot better and will now pull away and get to speed quicker, but its taking 16 seconds to get to 60!

and there is still no pull from the turbo, and it wont wheelspin, even in the wet.

the turbo is working, but it does provide any power until about 3500rpm, whereas it normally started spinning up just over 1000.

the MAF was dodgy as it has made a huge difference, but could something else be ary, such as the EGR or broken vacuum pipe or something. i do regularly give it a good hard run, but always wait for the temperature to be up and always let the turbo cool for a few minutes before i shut it down.

 

[sssstew]

yep, could be a dodgy vacuum hose or faulty egr/boost control valve. You will need to get boost pressure logged using vag com (requested vs actual) and see what the results are to start with to confirm it is the turbo thats being problematic.

 

[prc]

I would think that if it's that bad, you would be logging faults on the ECU. Check the simple stuff as Stew mentions.

 

[Red LCR TDI]

cheers, will post what the warranty garage says tomo, but they only have a handheld faultcode reader and not vag com.

just worried theyre gonna spend hours taking the car apart to find out whats wrong only to tell me it wont be covered and that i have to pay them to put the car back together

 

[Red LCR TDI]

just got the car back from the garage, they said they spent hours driving with the laptop plugged in, added another 60miles to the clock,

apparently everything was pointing to the MAF despite the new one being fitted, but it was a leaking boost control valve, (is that the N18/N75 valves)

anyway, the car is much better than it was before, but now have a new question - the car is secondhand, and it was quick before but must've always had a slight prob since i bought iot as there is such a huge increase in speed now.

should a bog standard 110 wheelspin in second from a rolling 10-15mph start or do you reckon it has been remapped? my housemate has a 130 diesel megane and he cant keep up. is this just because vag cars inherently have more power than labelled or has ir been tweaked already, guess ill have to take it to a RR.

 

[sssstew]

probably the pipes to the boost control valve were not sealing thus causing the N75 valve to not function right. N75s do go wrong, i wonder if they replaced yours.

Anyway glad youve got it all sorted now. The only way to tell for sure is to get it rolling road tested, but generally VAG TDIs do put out a little more than they say on the tin, so about 130 in your 110 wouldnt be unheard of.

 

[Red LCR TDI]

garage didnt charge me for any parts, only labour. they said they just cleaned the valve and reconnected the pipes. main cost was them trying to find out what was wrong, probably only took 20-30mins once they found it. but at least its fixed

will get it rolling road tested once i have a new exhaust, then think about what to do next.