Inlet Air Temperature Sensor

[enigma]

Is this located in the MAF? If so how does the ECU know the ACTUAL inlet temp after the air has been squished through the turbos? :inquisiti

[bradc]

I would beleive so, there are quite a few cables running from the MAF to the ECU, and I can't see any sensors anywhere after the intercooler. I guess you'd like to know this because you just changed your intercooler?

[enigma]

Correct..........ish

I removed the air filter as well as it was in the way and now I am dragging stupid hot air in............I figure that the ECU is seeing this high inlet temp and pulling the timing - despite the fact the intercooler is super chilling the charge. What a dumb place to monitor the temp /grr

[Dan_G]

Is this located in the MAF? If so how does the ECU know the ACTUAL inlet temp after the air has been squished through the turbos? :inquisiti

To calculate the mass of air actually entering the MAF, it needs to know the incoming air temp(density) and incoming air flow.

[Kenneth]

To calculate the mass of air actually entering the MAF, it needs to know the incoming air temp(density) and incoming air flow.

Check out this (http://www.efunda.com/designstandards/sensors/flowmeters/flowmeter_vtx.cfm) link.

The MAF we use are Vortex based.

EDIT: my facts suck... take someone elses:
"Since the frequency 'f' of a vortex generated is linearly proportional to the flow velocity 'V' within a wide range of Reynolds numbers without being affected by temperature, pressure etc.
The flow amount can be measured by counting the number of vortices."


If the car uses a temp sensor as well somewhere, I have no idea.

According to what I know of fluid dynamics, this will be enough for the ecu to determine the fuel required to keep the AFR appropriate.
If the intercooler makes the air more dense, the air speed at the intercooler outlet will essentially reduce, requiring more air through the MAF to keep up with the air demand from the engine.

Temperature increases will still increase chances / frequency of detonation, but the ECU is designed to compensate for this as you are essenially working with a lower octane rated fuel.

[Nick Mann]

Surely the engine only needs to know air flow? That is the amount of air going in, so the amount of fuel can be calculated correctly. I can see that the temperature of the air will have an effect on the flow, but does the car care what the air temperature is?

[Dan_G]

The way I always thought of it was like this:

flow x density = mass related to time

e.g.

[mm^3/second]x[kg/mm^3]=kg/second

and a simple way to find out air density is its temperature...

and from my knowlege of fluids, I also agree that if you cool the air after the intake(i.e intercooler) the density reduces and if you where to maintain the same mass of air throughout the intake system.....it meens the flow of air going into the MAF must increase.

Thats how I think of it anyway. :inquisiti

So really they could put the MAF meter right before the intake manifold after the turbos and intercooler.... that would probably sort out any problems anyone has with BOV's venting to much and over fueling the engine......

and another thing:

Fuel cut is a pain.......... bloody determined by the MAF... paa..... :rolleyes4

[paulmc]

They are normally situated in the inlet manifold. Not sure in the vr4 though I have not looked yet.

[enigma]

In true BDA style I have constructed a heat shield................results to follow! :thumbsup:

[enigma]

In true BDA style I have constructed a heat shield................results to follow! :thumbsup:

No change...........and a hose blew off grrrrrrrrrrr................oh well I will sort it out soon! I hadn't planned on running this weekend anyway!

[ako]

It monitors total air volume: if its hotter at the inlet, if just sees less volume (airs less dense when hotter.. physics 101) - hence people with a pod filter in an open engine bay will think they can run more boost due to the fuel cut coming in later... Truth is, despite a bigger psi number, they'll be making less power than the guy with 1psi less but a proper cold air setup. Trust me, I've watched it on the logger, and proved it on the strip.

What it DOES do once inside your intake/cylinders is monitor knock.. Just gives as much advance as it can before it starts picking up detonation. If youve got hot intake temps, then it pulls timing earlier. Simple. The temperature once inside there doesn't really matter if its watching out for a/f ratios and knocking.


Case in point: My 7G, stock apart from an exhaust, would get to around 23-24psi before fuel cut came in. Once I put in a cold air box and upgraded the intercooler, it dropped to about 19psi due to the increased air volume. (p.s - these figures were obtained for academic usage only :p - normal boost for me is 16-17psi.)