RodSTI

Can someone explain what it's for and how it works.

I can't get my head round why one is used on a turbo car. Surely it can't measure the air flow properly when it's been sucked in, compressed then either used by the engine or wasted back past the Maf when the throttle is closed. Have I got it all wrong?

JamieMiller

The ecu needs to know the exact amount or volume of air that is entering the engine so that it can match the fuel and give the ideal air fuel ratio. When the MAF starts to go wrong this is when the fuelling is messed up and potential problems occur. It doesn't matter what the turbo is doing to the air.

swisstonihasher

This will "blow" your mind...

I've always wondered a little about the MAFs also, but yes they do read air flow and ecu injects fuel in relation to that reading.

I'm heading for 500 bhp still with oe ecu but now I'm changing over to a blow through setup, ie maf in the boost tube - what I didn't realise is that the air flow amount is still the same be it on the induction pipe or on the boost tube, the only difference is that the IC pipes are under pressure, ie forcing into the engine.

Bob R's going to be setting my motor up early next year but I've already had her running with maf in blow through setup and its looking good for my slightly lumpy idle and fluffy running below 2,500 (due to cams) to be removed!

MAFs just need a clean every now and again, with electrical cleaner, especially if you have a CAIK setup with oil based filter.

RodSTI

Does the ecu only use the maf sensor output when the throttle is open? cos when the throttle is shut, say when changing gear, all that pressurised air rushes back down the pipe passed the maf and out through the filter. That sounds a tasty motor you have there swisstonihasher. Do you have a front mount? and what have you done to the ecu?

SSCJAY

If you keep a recirc BOV then the air circulates within the system in front of the Maf, air does not pass back passed the Maf and out of the filter (although you can here the noise of the air moving within the system through the filter).

swisstonihasher

I'm no expert on the ins and outs of the MAF setup as that's mapper territory but I do know that if you have a VTA instead of standard, the boost goes out the "window" but the MAF still reads air flow which it thinks goes into the engine but the butterfly is shut - hence the running rich/lean/rich on gear change as ECU and MAF dont agree on mix. So say my blow through setup allows the MAF to read the flow properly as it goes into the engine, it also stops the fluffing of wild cams - not that I understand it totally as I would of thought there's a cross over with cam timing (my setup used the oe cam pulley sets so no vernier timing).
Oh yeh, sure do have FMIC, with intercooler water spray, water injection, manifold cooling system, and manual rad spray when needed - 4 tanks in the boot = madness!