MAF/ MAS cleaning

CRZ_MSL · 12-06-2000, 01:38 AM

Picture of the MAS after removal from airbox. Notice the sooty stuff on the wire mesh. This is after 120,000 miles of using a K&N panel filter.

Removal was quite easy- a flathead screwdriver and a 10mm socket wrench is all that is needed. Look closely and you'll see soot on the actual sensor

Half of the mesh has been cleaned off, revealing the original silver color.

The mesh is not designed to be removed. But I removed it anyway. I slightly damaged the housing in the process, but looking at the picture I'll bet you cannot tell where I gently forced it out with a very thin flathead screwdriver. After pulling the mesh out I cleaned both sides, and was able to get at the leading edges of the airflow measurement sensors.

Steady hands and several Q-tips later the internal sensors are clean. I did not pay much attention to the brown projection. Much effort was spent getting the parts inside it free of soot.

A cleaner sensor should give me more accurate airflow readings.

The MAS had it's own serial number. It looked like an off the shelf part, likely used on other vehicles. When I get the chance I'll take a look at the airflow sensor for the older Infiniti Q45 and Nissan 300ZX. There is a good chance that it will be dimensionally identical.

I can't vouch for compatability with the unit on the Skyline.

On the outside of the MAS, inside the upper half of the airbox, is a metal velocity stack. This part appears to be of suboptimal design. Further testing should be done to determine the effect of removing the mesh from in front of the airflow sensor, and of improving the velocity stack to ensure laminar flow across the sensor.

P.S.: I put the mesh back in before remounting the apparatus in my SVX.

[This message has been edited by CRZ_MSL (edited December 06, 2000).]

Never2phat · 12-06-2000, 07:35 AM

Eek, One more project to add to the list

Just curious.....Could someone please tell me how this(dirty vs. clean) affects the car and how it runs. Thanx in advance

B.C.

P.S. CRZ MSL, Thanks for the pics.....Great job

CRZ_MSL · 12-06-2000, 08:07 AM

I'll know in a few minutes when I get my lazy behind into the SVX and on the way to the gravel pits.

Pski · 12-06-2000, 09:12 AM

Greetings,

What benefit would a Nissan/Infiniti MAF sensor afford? Are they capable of handling high airflow such as in a forced induction setup?

Pski

CRZ_MSL · 12-06-2000, 09:50 AM

It would be interesting to see if this apparently off the shelf part is available from the Nissan parts bin at a cheaper price.

If this part is identical to the Nissan/Infiniti part, but the one for the Q45 is $50 cheaper than ours, someone has a bit of explaining to do.

If the part is indeed identical, that opens up the world of Nissan aftermarket intakes to us. And possibly the Impreza crowd.

I am hard pressed to think of any other device on the car that is assigned a unique serial number, it's as if they went to the MAS store in East Kyoto and picked up 24,000 of them to install on the SVX production run.

svxxx-26 · 12-06-2000, 10:03 AM

Just a little anecdotal info about those sensors:
In the process of trying to fix an idle problem, I had replaced my sensor with one from a Legacy. The part # was different, the tag the part # was on was a different color (Legacy=green, SVX=blue) and it had a decreased opening (like a slight bottlenck).
But it bolted right up and worked just the same.

Scottie · 12-06-2000, 12:22 PM

The screen(wire mesh), at the opening of a hot wire(shown above) or hot film mass air flow sensor, is there for a reason. Removing it will likely cause errors in reading the mass flow rate.

As one can see from the above pictures, the hot wire is relatively small in relation to the overall cross-sectional area. In other words, its only sensing a portion of the air flowing through the outer housing. Thus its important that the flow velocity be relatively equal across the cross-section, so that the portion of flow over the hot wire is representitive of the average flow through MAF.

The velocity profile of laminar flow through a tube tends to be somewhat bullet shaped. Like this > , just a little bit rounder instead of a sharp point. (Sorry, I don't have a good means of scanning in a sketch and posting here). Fully developed Turbulent flow is more bottle cap shaped. Somewhat like this ]. The velocity is relatively even across most of the cross-section. With a bottle cap like velocity profile, the flow across the hot wire will be closer to the average across the cross-section and thus provide a better indication of the mass flow rate.

The screen is there to help assure fully developed turbulent flow through the MAF. The only good think that I could say about removing the screen is that it would most likely result in an error to the high side. Meaning it would likely indicate a higher mass flow rate than what is actually flowing into the engine. This would result in more fuel than is needed(i.e. it will run Rich). This would be better than the error to the low side that occurs with the Hot film MAF on MY99 2.5L RS engines with certain aftermarket intakes. Such an error results in running lean.

rosss · 12-06-2000, 02:50 PM

As a '99 RS owner, I'd be *very* interested to hear of your findings about alternat MAF units from Nissan. I'd expect that many of us would be interested...

Thanks for the good documentation so far too,

Sean

CRZ_MSL · 12-07-2000, 01:26 AM

Thanks for your explanation, I can see it clearly in my head. I understand what you are saying completely, and agree with your reasoning that pure laminar flow before the wire is a bad thing.

What are your thoughts regarding relocation of the sensor? Am I correct in saying placing the sensor farther downstream from the IRIS will result in more error when reading changing airflow rates (there is a large resoivoir of air upstream to munge the readings) and that placing the sensor fuarther upstream (really close to the IRIS chamber) will result in even more accurate readings of changinf airflow rates (there is no accumulated mass of air between the sensor and the engine.

I think it would not matter either way for steady state volumetric flow rate, but what about transitory spikes/troughs in pressure caused by suden acceleration / upshifting?

Or am I needlessly worrying about the inertia of the air in my intake?

STiShawn · 12-07-2000, 08:48 AM

Please keep us up do date, as another 99RS owner, any help is better than none.

Shawn

CRZ_MSL · 12-07-2000, 09:27 AM

I have made arrangements with the owner of a 300Z... I'll keep y'all posted.

Pski · 12-07-2000, 09:39 AM

Greetings,

With all of the discussion regarding Subaru/Nissan compatibility I did some research. Most have heard that the Nissan Motorsports 555cc Fuel Injectors will bolt up to the SVX...

Any guesses as to price?

How about $225 EACH! Ouch...more discouraging news can be found below.
http://www.courtesyparts.com/secondtier_z32_cnm.html

Better be nice to Santa...

Pski

12-06-2000, 01:38 AM	#1
CRZ_MSL Scooby Newbie Member#: 1610 Join Date: Jun 2000	MAF/ MAS cleaning Picture of the MAS after removal from airbox. Notice the sooty stuff on the wire mesh. This is after 120,000 miles of using a K&N panel filter. Removal was quite easy- a flathead screwdriver and a 10mm socket wrench is all that is needed. Look closely and you'll see soot on the actual sensor Half of the mesh has been cleaned off, revealing the original silver color. The mesh is not designed to be removed. But I removed it anyway. I slightly damaged the housing in the process, but looking at the picture I'll bet you cannot tell where I gently forced it out with a very thin flathead screwdriver. After pulling the mesh out I cleaned both sides, and was able to get at the leading edges of the airflow measurement sensors. Steady hands and several Q-tips later the internal sensors are clean. I did not pay much attention to the brown projection. Much effort was spent getting the parts inside it free of soot. A cleaner sensor should give me more accurate airflow readings. The MAS had it's own serial number. It looked like an off the shelf part, likely used on other vehicles. When I get the chance I'll take a look at the airflow sensor for the older Infiniti Q45 and Nissan 300ZX. There is a good chance that it will be dimensionally identical. I can't vouch for compatability with the unit on the Skyline. On the outside of the MAS, inside the upper half of the airbox, is a metal velocity stack. This part appears to be of suboptimal design. Further testing should be done to determine the effect of removing the mesh from in front of the airflow sensor, and of improving the velocity stack to ensure laminar flow across the sensor. P.S.: I put the mesh back in before remounting the apparatus in my SVX. [This message has been edited by CRZ_MSL (edited December 06, 2000).]

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12-06-2000, 07:35 AM	#2
Never2phat Scooby Newbie Member#: 1683 Join Date: Jun 2000 Location: Carlisle, Pa, USA	Eek, One more project to add to the list Just curious.....Could someone please tell me how this(dirty vs. clean) affects the car and how it runs. Thanx in advance B.C. P.S. CRZ MSL, Thanks for the pics.....Great job

12-06-2000, 08:07 AM	#3
CRZ_MSL Scooby Newbie Member#: 1610 Join Date: Jun 2000	I'll know in a few minutes when I get my lazy behind into the SVX and on the way to the gravel pits.

12-06-2000, 09:12 AM	#4
Pski Scooby Newbie Member#: 1696 Join Date: Jun 2000 Location: Grand Forks, ND, USA	Greetings, What benefit would a Nissan/Infiniti MAF sensor afford? Are they capable of handling high airflow such as in a forced induction setup? Pski

12-06-2000, 09:50 AM	#5
CRZ_MSL Scooby Newbie Member#: 1610 Join Date: Jun 2000	It would be interesting to see if this apparently off the shelf part is available from the Nissan parts bin at a cheaper price. If this part is identical to the Nissan/Infiniti part, but the one for the Q45 is $50 cheaper than ours, someone has a bit of explaining to do. If the part is indeed identical, that opens up the world of Nissan aftermarket intakes to us. And possibly the Impreza crowd. I am hard pressed to think of any other device on the car that is assigned a unique serial number, it's as if they went to the MAS store in East Kyoto and picked up 24,000 of them to install on the SVX production run.

12-06-2000, 10:03 AM	#6
svxxx-26 Scooby Newbie Member#: 1645 Join Date: Jun 2000 Location: Sissonville, WV, USA	Just a little anecdotal info about those sensors: In the process of trying to fix an idle problem, I had replaced my sensor with one from a Legacy. The part # was different, the tag the part # was on was a different color (Legacy=green, SVX=blue) and it had a decreased opening (like a slight bottlenck). But it bolted right up and worked just the same.

12-06-2000, 12:22 PM	#7
Scottie Scooby Specialist Member#: 2080 Join Date: Aug 2000 Location: CT Vehicle: 02 WRX Sport Wagon Silver	The screen(wire mesh), at the opening of a hot wire(shown above) or hot film mass air flow sensor, is there for a reason. Removing it will likely cause errors in reading the mass flow rate. As one can see from the above pictures, the hot wire is relatively small in relation to the overall cross-sectional area. In other words, its only sensing a portion of the air flowing through the outer housing. Thus its important that the flow velocity be relatively equal across the cross-section, so that the portion of flow over the hot wire is representitive of the average flow through MAF. The velocity profile of laminar flow through a tube tends to be somewhat bullet shaped. Like this > , just a little bit rounder instead of a sharp point. (Sorry, I don't have a good means of scanning in a sketch and posting here). Fully developed Turbulent flow is more bottle cap shaped. Somewhat like this ]. The velocity is relatively even across most of the cross-section. With a bottle cap like velocity profile, the flow across the hot wire will be closer to the average across the cross-section and thus provide a better indication of the mass flow rate. The screen is there to help assure fully developed turbulent flow through the MAF. The only good think that I could say about removing the screen is that it would most likely result in an error to the high side. Meaning it would likely indicate a higher mass flow rate than what is actually flowing into the engine. This would result in more fuel than is needed(i.e. it will run Rich). This would be better than the error to the low side that occurs with the Hot film MAF on MY99 2.5L RS engines with certain aftermarket intakes. Such an error results in running lean.

12-06-2000, 02:50 PM	#8
rosss Scooby Newbie Member#: 1841 Join Date: Jul 2000 Chapter/Region: NWIC Location: Corvallis, Oregon, USA Vehicle: 1999 Impreza RS Silver	As a '99 RS owner, I'd be very interested to hear of your findings about alternat MAF units from Nissan. I'd expect that many of us would be interested... Thanks for the good documentation so far too, Sean

12-07-2000, 01:26 AM	#9
CRZ_MSL Scooby Newbie Member#: 1610 Join Date: Jun 2000	Thanks for your explanation, I can see it clearly in my head. I understand what you are saying completely, and agree with your reasoning that pure laminar flow before the wire is a bad thing. What are your thoughts regarding relocation of the sensor? Am I correct in saying placing the sensor farther downstream from the IRIS will result in more error when reading changing airflow rates (there is a large resoivoir of air upstream to munge the readings) and that placing the sensor fuarther upstream (really close to the IRIS chamber) will result in even more accurate readings of changinf airflow rates (there is no accumulated mass of air between the sensor and the engine. I think it would not matter either way for steady state volumetric flow rate, but what about transitory spikes/troughs in pressure caused by suden acceleration / upshifting? Or am I needlessly worrying about the inertia of the air in my intake?

12-07-2000, 08:48 AM	#10
STiShawn Scooby Specialist Member#: 2348 Join Date: Sep 2000 Chapter/Region: MWSOC Location: St.Louis Vehicle: 2006 WRX TR Steel Grey Metallic	Please keep us up do date, as another 99RS owner, any help is better than none. Shawn

12-07-2000, 09:27 AM	#11
CRZ_MSL Scooby Newbie Member#: 1610 Join Date: Jun 2000	I have made arrangements with the owner of a 300Z... I'll keep y'all posted.

12-07-2000, 09:39 AM	#12
Pski Scooby Newbie Member#: 1696 Join Date: Jun 2000 Location: Grand Forks, ND, USA	Greetings, With all of the discussion regarding Subaru/Nissan compatibility I did some research. Most have heard that the Nissan Motorsports 555cc Fuel Injectors will bolt up to the SVX... Any guesses as to price? How about $225 EACH! Ouch...more discouraging news can be found below. http://www.courtesyparts.com/secondtier_z32_cnm.html Better be nice to Santa... Pski