Tuner@Swift

iTrader: (1)

Explain how the MAF, a device for metering airflow, is affected by noises?

It's the knock sensor picking up the metallic transient frequencies from slamming the hood or from loud engine noises close by that is retarding timing severely.

Speedlimit

The MAF uses a Karman Vortex generator which delivers a frequency proportional to flow velocity at the intake. A frequency sensor is sensitive to outside sources (including harmonics) from slamming the hood or a loud Harley.

Speedlimit...

Tuner@Swift

iTrader: (1)

I understand how a KV MAF works, and your explanation is incorrect. The sensor used to measure the occurrence of a karmann vortex is an LED and a phototransistor. The signal generated is a 5v square wave based on the frequency of detected karmann vortices. If the sensor was highly susceptible to vibrations, such as those produced by sound, then it would serve poorly as an airflow meter in a platform that is always vibrating at various frequencies.

Now, explain to me why when I shut my hood, I get the exact same stumble when I do not have the stock karmann vortex MAF? Or why it would happen when I had no MAF at all?

19psi

iTrader: (6)

hmm...I get the same thing when I close the hood.
I thought I had a boost vacum leak somewhere and I checked every clamp
possible and pressure tested all the hoses but it's the same.

The MAF sensor idea does make sense though.
BTW, my 03 did the same.

Speedlimit

Good discussion. I'm not convinced that the MAF (as a system) is immune to all frequency spikes from outside sources. We have had this discussion before (I think I loose it all the time ) but remain unconvinced that the knock sensor is the sole trigger. At least from my professional experienced I have met few frequency converting gizmo's that were not susceptible to a specific bandwidth of high amplitude harmonic pulses. And if my glasses are vibrating sitting next to a Harley, the air intake might be dancing around.


Speedlimit...

Rich EVO MR SE

It's normal.

idriveanevo

iTrader: (30)

mine started doing this after the installation of my k&N intake because it was very flimsy. im sure it the maf(at least on mine) because if i slighty hit the top of the maf or the filter it does the same thing....

hotrod2448

Could it be a sudden change in pressure around the MAF from closing the hood? Maybe combined with the knock sensor. If you think about it it's just like closing a door or a big sub woofer, it is definitely going to move some air.

Bonestock!

iTrader: (3)

I have experienced this many times on various Skylines. I have always suspected the MAF sensor(s) are well. I found it happened more regularly on ones fitted with induction kits.

Smike

iTrader: (8)

Ok few things here...its idriveanevo

And the k/n typhoon is a crappy intake. Do read and search about that. Id go back the the OE MAF to turbo inlet pipe.

But your "testing" sounds right for the MAF being a big part of the prbs described. When I am at the dragway I experience the same thing when I am at idle next to some unholy loud doorslammer. The sound vibrations can be felt by the car and by me inside the car. Im sure the knock sensor is feeling some of that, but I think the MAF is vibrating more than normal.

Just dont slam the hood with the car on or be nicer when closing the hood - problem solved (if you can truely call this a problem).

urslo4n8

iTrader: (5)

DEF MAF sensor........everyone i know has that same problem......and EVEN more so now since the install of the HKS suction intake, So there ya go

idriveanevo

iTrader: (30)

i know it shound be AN thanx, and its not a typhoon intake. its only the filter and adapter.

DevilsEvo666

The reason why the engine wants to quit is because the hood momentarily disrupts the air that goes into intake duct that goes into the airbox when you slam the hood it pushes out any air around the air duct and the engine doesnt have any air to breathe. its like slamming a door in your room and feeling all the air brush past you, the same thing happens to the airbox where the air gets pushed away from it and it doesnt have any air to breathe... It took me a while to figure out but thats what happens... hope that clears it up for you guys..

gsrboi80

iTrader: (38)

Its the maf. Try tapping on it when the car is running it does the same thing

evodrivesme

iTrader: (7)

is your battery to high haha