Thread: All I want for Xmas is a MAF

withdrawn... not helpful!

The 4000rpm number under a quick throttle stab should be around 550 to 600. 50 at idle is OK, just. 57 to 61 is great.
The ambient pressure and manifold pressures at idle should be almost the same, they are measured in absolute. Usually I get 100Kpa in the manifold and 101Kpa ambient at idle.

JC

Try giving the MAF a quick clean. Not usually a long term solution but worth a try if you're stuck and desperate. I've had a couple that I've managed to stretch a bit more life out of with a good clean but they all go the same way in the end.

In my experience much cheaper bought from abroad, quite light and smallish means the postage is reasonable. When sourced in Aus. some of the prices I've been quoted have been daft. Don't buy the really cheap ones though - rubbish.

Ian.

What modifications have you got? With my D2a, when I increased the standard turbo charger boost pressure to 18psi, I had to use a modified MAF sensor (purchased from Alive Tuning/TD5 Alive in the UK) as the standard OEM MAF could not handle that much air flowing through it, it would exceed it's sensor range.

Another alternative is to use a by pass hose. Basically, a hose, around 19mm is commonly used, that bypasses the MAF, this allows the standard sensor to still be used as the excess air flows through the hose.

The third option is to use a dual channel turbo boost box such as that offered by IRB Developments in the UK, this tricks both the MAP sensor (like all turbo boost boxes) but also does the MAF sensor too.

Originally Posted by wardy1

Anyway, it does appear that my MAF may be stuffed and thus the lack of power when overtaking etc as I'm told by Blknight that when the engine over boosts, it restricts fuel feed.

If its over-boosting enough to trigger fuel cut-out you'll get massive surging from about 2500 rpm with full throttle, not lack of power. Boost should be limited to around 22 psi at the turbo and a few psi less at the MAP sensor although initially up to at least 25 psi at the turbo until the ecm prunes it back because the MAP sensor reading is too high, by operating the boost modulator to allow the wastegate to start to open. I'd check that the boost modulator is working properly, that the wastegate actuator isn't siezed and I/C hoses haven't started to delaminate.

Thanks Justinc for the info on the readings.

Mools I did give the MAF a clean yesterday with contact cleaner to no avail.

At the end of the day, I can drive it back to Melbourne as it is, just have to arrange for a postcard to any trucks I want to get past LOL.

Originally Posted by Graeme

If its over-boosting enough to trigger fuel cut-out you'll get massive surging from about 2500 rpm with full throttle, not lack of power. Boost should be limited to around 22 psi at the turbo and a few psi less at the MAP sensor although initially up to at least 25 psi at the turbo until the ecm prunes it back because the MAP sensor reading is too high, by operating the boost modulator to allow the wastegate to start to open. I'd check that the boost modulator is working properly, that the wastegate actuator isn't siezed and I/C hoses haven't started to delaminate.

I have checked that the wastegate actuator is working. I have been experiencing some (not massive) surging from about 2700rpm with full throttle. The I/C hoses were replaced earlier this year.

Just curious, you mention a boost modulator AND the wastegate actuator. Where is the boost modulator? (D2a)

OK. Well just disconnect the MAF. It'll default fuelling (air and fuel) to some saved values that make the vehicle quite drivable but a little stunted - but nowhere near like a crapped MAF does and quite safe to do so. Connect it up when you get a replacement.

Chances are the economy may take a bit of a bite but if it's mainly highway cruising speed may not be too bad. Either way I doubt you'll waste as much fuel as the cost of a MAF in a hurry.

Have a happy christmas and safe travels.

Ian.