Tech quesion about MAF air flow level's and effect on?
 

I was wondering. If the oem 6mt MAF sensor is housed in a tube that measure's let's say 2.8" on the inside. What happens when it's housed in a tube that measure's 3" on the inside and and it see's less airflow at any given RPM level since the volocity will be lower? What changes would it order up at say 5500rpms when for the sake of arguement it gives off a voltage of 4.3 volts with the oem sized MAF housing and say 3.9 volts at the same RPM level with a 3" housing? If it effects air/fuel, is that the only thing thing the voltage drop means?

Good question, I would like to know more as well!

-t3k

Thinking out loud: If the same air goes through a bigger tube it would give a lower voltage I suppose as slower or less air will be going past the sensor and less voltage will be needed to heat the filament. It may be tricky to not consider whether the engine will draw more air than before so -- since the engine may take in more air (I dont really know) the above point may be moot. Where is DaveO?

Jim,

Here's my thoughts. I believe the engine would run lean (and hot) due to the extra, essentually unmetered, air entering the engine. The O2 sensor(s) would probably allow the ECM to "see" the lean condition and it would try to add fuel. However, if the air or air/fuel ratio is off the ECM map the engine may go into the limp mode. As you know, this has been a problem for some of the FI guys.

Thanks to Gurgen's input I was able to determine there are several different MAF Sensor wiring schemes ahead of the MAF Sensor. All MAF Sensors have three wire connections, except for the Type 1 (03 AT Sedans) which have four. Type 1 and Type 2 (03 Coupes and 03.5 Sedans) MAF Sensors are designed with a screen, the later cars don't have the screen. Also the operating voltage range is slightly different between the 03, 03.5 cars and the 04, 04.5 and 05 cars.

Did you record the maximum MAF Sensor voltage when you did your intake system temperature tests with the TecTom? I've measured mine at just under 5.0 volts at sea level with my current mods. While my car has never predetonated on the road, it has done so everytime it's been dynoed at sea level. I'm thinking of changing to one step colder plugs. Your thoughts?

DaveO do unmodded cars tend to stay well shy of the 5.0 volts you and I get so near?

I found the data it had written down about peak MAF sensor voltage, 4.79 volts. That was with the oem MAF housing and Z-tube and the rest of my reworked 350Z Typhoon. When I switched to the insulated K&N tube I did not record the number, but I'm positive that it was 4.31 volts. I did notice that the K&N setup had much better punch from 5k to redline.

this is actually a trick used on DSMs and 240's, its called a hacked MAFS setup

I used it on my oldturbo 240 as a quick fix to a fuel management issue. i forget the precise science to it, but it somehow tricks the ecu into reading a higher voltage and therefore giving the engine more fuel

whoa, this is something i'm really interested in...i believe i'm running a little lean w/headers, y-pipe, k&n drop in filter, z-tube and resonator removed.......how was it done on the dsms and your 240? details please!! thanks.

So you combined the Z-tube and the Typhoon CAI? Sounds like it did better than the K&N CAI anyway but you still recommend the stock air box in your signature! Care to expound?

We need a stock techtom AirFlow reading.

Also what did you think of the Injen - I thought it was pretty good at upper rpm (that's what I had on it when I raced) but it was crappy down low to me and it was a little thrashy for me in thos higher rpm's. Resonance of the income air was AFU or something.

its a pretty risky maneuver and i dont know if you would want to try it.

what i had to do was take my MAFS and cut all the plastic tube around it off so it was just the square box pn top with the MAFS element remaining. i drilled a hole in a 3 inch exhuast pipe and inserted it into the pipe.

the idea is that, the cross sectional area of the inside diameter of the 3 inch exhaust pipe was 38% larger than the area of the stock plastic tube, allowing my 270cc injectors to function like 370cc injectors

270 x 1.38 ~ 372

but doing this also raises the injector duty cycle, so proceed with caution.

i thought it would be modding the maf sensor wires via resistor or something like that to trick the ecu to compesate more fuel with the extra air coming in.........cutting out the maf unit entirely is kinda beyond my ability......glad to see it worked for though.......thanks.

Dave, if it doesn't go into any limp mode with bolt ons ..headers, y-pipe, intake, etcc......is ecm allowing more fuel to the extent of the bolt ons for n/aspirated?

We've tested a couple of stock G35s and 350Zs. If my memory serves me correctly the numbers ran in the 4.2 to 4.4 range. The highest value I've captured on my car was 4.93 volts. Remember, the scale is expediential.

I did a WOT run today and recorded a 4.96 Volts. Dam. I guess my intake setup rocks. I wish we had all intake setups max voltage in a matrix. Outside temps must play a factor in that reading and it was cold today so I'll try again in summer and see what happens.

intake temps do make a difference, since colder air is denser, then there will be more air

also since the mafs is a hot wire type, then it'll read higher when the air is colder