MAF with boost.

[barryogen]

Can anyone explain to me how engines with MAF, not MAP, work when boost is added?

I'm guessing that you need to somehow make the engine aware that it has a lot more air going through the engine, as otherwise it would run rather lean.

Now, from what I understand, if you run the MAF before turbo, assuming that the MAF doesn't go outside it's limits, will see a heap of air going into the engine. Running afterwards it wont see as much as it will be pressurised air.

So I guess it has to go Filter, MAF, Turbo, IC, TB, engine...

I know that changing to MAP would be the ideal answer, but I just wondered how MAF'd ones work.

[postfach]

yes thats how you do it

[barryogen]

cool, good to know that I'm getting my head around this stuff...

and I assume that if you have a BOV you need to have a re-circ one as otherwise it will do weird things with Air/Fuel ratio seeing as it has already "counted" the air that should have gone into the engine?

[postfach]

also correct, people that have vented BOV's on cars with MAF will find that when they change gear they might get a backfire or the engine may stall because the mixture will go quite rich.

[barryogen]

thanks for that... handy to know for future reference

[method]

Yup thats all correct.

The car should be ok even with the BOV venting all thought when you do change gears and put the clutch in ( say a quick 3 point turn, first to reverse or vice versa) the engine could stall. But when driving normally and shifting up gears it should be fine.

Some ecu's are more sensitive than others with that.

You can get kits that buffer the singnals from your maf meter.
http://www.hksusa.com/products/?id=2175

[pureadrenalin]

Can anyone explain to me how engines with MAF, not MAP, work when boost is added?

Works bloody fantastic, actually better than MAP in a lot of cases (explained below).

I'm guessing that you need to somehow make the engine aware that it has a lot more air going through the engine, as otherwise it would run rather lean.

The engine is aware because the MAF meter is metering more air!

Now, from what I understand, if you run the MAF before turbo, assuming that the MAF doesn't go outside it's limits, will see a heap of air going into the engine. Running afterwards it wont see as much as it will be pressurised air.

Key sentence there “doesn’t go outside it’s limits”
Side note. They can be run after the turbo, but they aren’t generally designed to do this. (can go into this further if you wish)

So I guess it has to go Filter, MAF, Turbo, IC, TB, engine...

Yep, that’s the way to go.

I know that changing to MAP would be the ideal answer, but I just wondered how MAF'd ones work.

Changing to MAP, (which means changing to an aftermaket ECU), means re-tuning every time you change the VE of the engine, other wise you run leaner/richer. (generally leaner, because I don’t know anyone trying to lower their VE).

^^ key point there so I’m going to repeat it ^^

MAF can be god send if you don’t go outside its “range”.

You can modify to your hearts content and not worry about running to lean, because the flow meter takes every improvement in VE in its stride, adding fuel as needed as your engine flow improves.

MAP on the other hand, when you improve the VE, the ECU sees exactly the same parameters (it dosen't know you've improved the VE), but the engine will be flowing more, therefore running leaner.


What a mouth full

[barryogen]

They can be run after the turbo, but they aren’t generally designed to do this. (can go into this further if you wish)

I would assume to keep them inside their limits of flow?
Wouldn't it also help the engine know the temp of the air that is coming into it as well?

I know that changing to MAP would be the ideal answer, but I just wondered how MAF'd ones work.

Changing to MAP, (which means changing to an aftermaket ECU), means re-tuning every time you change the VE of the engine, other wise you run leaner/richer. (generally leaner, because I don’t know anyone trying to lower their VE).

^^ key point there so I’m going to repeat it ^^

MAF can be god send if you don’t go outside its “range”.

I'm going to have to go after market ECU anyway, just looking at different ways to do it... see this thread.
http://forums.toyspeed.org.nz/viewtopic.php?p=590471#590471

[pureadrenalin]

I'm going to have to go after market ECU anyway, just looking at different ways to do it... see this thread.
http://forums.toyspeed.org.nz/viewtopic.php?p=590471#590471

In that case, my pick would be the G3 running MAP. Just realise that you will be retuning if you do significant VE changes. Which is fine if your not adding pats to the car monthly. Just get the turbo, intercooler, exhaust, etc that you intend on using before you go and tune.

[barryogen]

much abliged... thanks.