Considering that OEM maf can handle up to 650-700hp and that a properly tuned k24/18g car with injectors can burn them from time to time...i realized a way to make it handle more hp...
MAF pipe internal diameter is 85mm...that gives as 56,7 square cm of cross sectional area...i managed to modify the OEM airbox and to install a pipe with 120mm internal diameter...which occurs to 113 square cm of cross sectional area...The maf is burned because the air needed for 700hp when passing from an 85mm pipe has a speed that overrides the 5volt signal it can handles...But when we install a pipe of 120mm same air(for 700hp)has much slower speed resulting in a signal voltage of 3 volts...so we do not burn the maf...Of course we need to readjust the DME so to understand new setpoints of MAF...the project is still under construction...but stay tuned...Next days i will have results...

 

That is an interesting idea but I wonder if you will not need a software adjustment to get accurate measurements from the MAF after the change...

 

This is very true- at it's heart the MAF is a VELOCITY SENSOR, not a volume sensor. Increase the cross section at at a given velocity, the flow is increased.

A few comments:

1. MAFs burn up due to turbulence and non-linear flow at the limit- not simple overvoltage. They have protective circuits when the velocity goes high the output is clamped at 5V. What kills them is when you have hot and cold spots within the center of the element the silicon substrate itself gets over-stressed.

2. Increasing the cross section will ncrease the overall maximum volume, but your are still dividing a 5V signal across that entire range. Resolution goes down.

3. Linear and 'well behaved' flow is essential. This cannot be overstated. The maf is measuring flow at a single point and extrapolitng a voulmetric number from this. If, as your ramp up the flow in your new pipe, the flow pattern changes dramatically, you will not be sensing real air volume.

4. Finally, with really large cross sections, low flow is very hard to measure... your idle and low throttle air numbers will be whacky.

All IMHO.

(I would not have double the cross section, but rather more of an incremental change based on where your motor needs to be...)

As you stated, and MBailey points out, your lookup table for A/F in the DME needs recalibration.

GL

A

 

Be careful with this unless you have the tuning to support it.

 

Thank you guys for your answers...I was about to install pipe with 100mm internal diameter but i couldnt find any...the next size from 85mm was 90mm and then 120mm...Tomorrow hopefully i ll give it a try to see what is going on...And if i blow a maf again...i will go for proto style intake...Ford maf in the Y hose...lets see...

 

bUt how do you read the information if the stock maf cannot read understand those values outside it's raange? If one is just trying to stocp the maf from blowing thats fine.... but how do you calibrate a maf beyond its limits if it has a limit of 600 ho lets say?

 

With ECU recalibration I've been running 95mm ID successfully for over 2 years. No MAF problems.

 

So there is another guy done that...tell us more...

 

Mark,

I believe it was a DME recalibration that was done for me and not the MAF. I don't think the MAF can be calibrated.

 

Good Job.

The ford guys have been switching "sampling tubes" within mafs to calibrate them to specific injectors without any tuning.

However I'd be very carefull messing with switching the diameter and flow characteristics of the maf without changing the values in the DME and putting the car on a wideband.

 

Guys...dont worry about WOT...the car takes under consideration set point of lamda...At the dyno i blown my maf on the first measurement...(on the street boost was 1,37-1,39 but on the mustang it reached 1,42 so the maf was overvoltaged and burned...)However the car was fine tuned with a blown maf...and believe or not...AFR was 12,0...all the way at WOT with maf off...On the other hand if a maf is blown the car losses its accuracy while driving in half throttle and in fast shifting...and idling of course...
Now in order to analyze further the operation of the Maf...each unit is designed for specific pipe diameter...so at 700hp OEM maf sees a certain density and speed of air in his sensor at OEM pipe...When we enlarge the pipe,same air has to pass through greater diameter and is spread so the speed and the density are lower...so the maf sensor reads smaller value...That way,we manage to avoid burning...Of course the DME sees maf value which might correspond to 500hp instead of 700...and that is where adjustment (of DME)is needed...

 

This has been done on many a car with a MAF sensor. There are a coupke of way this can be approached. In essence, the MAF is a sensor in a tube. If one has a 100mm diameter tube and “650hp worth” of air travels through it—this air cools the sensor…the amount of voltage required to maintain the sensors temp is what the ECU see’s. Yes a 100mm tube “could” support 1900hp. But that would increase the voltage required to cool the sensor to a value that is very high—and out of range. If you can imagine increasing the diameter of the tube to 120mm---now- all of a sudden—the same 650hp worth of air goes through the tube at a much lower speed. Lower speed means less cooling on the sensor—thus a lower sensor output. With the larger 120mm tube---the 650hp worth of air that once maxed out the sensor---now only registers 4Volts’s…which means you can flow another 20% more air before the sensor is maxed out. This all sounds amazing until the car tries to idle. This is because the ECU has an internal chart that it looks at…1.2volts =X amount of air…..Now when the car idles the sensor in the 120mm tube registers 0.6V in stead of the usual 0.8V…..the ECU now believes that the engine is flowing much less air than it really is….Thus the ECU injects much less GAS. The result is a much leaner A/F mixture.

There are several ways around this. The best is to get Tony to adjust your map. But for the budget minded there are “other ways”….

1)One good way is to proportionally increase the size of the injector to the size of the new MAF. For example---to go from 45lbs injectors to 54lbs injectors(20% increase) then you can increase the area of the tube by 20%. The net should be pretty close. You don’t even need a bigger tube. A bypass tube works just as well.

2)If you want to keep your stock injectors….a product like MAFterburner can be used. This takes the MAF signal and adjusts it to the owners wishes. So in the upper flow areas---you leave it the same—but in the lower part throttle areas, you can adjust it up. The benefit here is the whole curve can be manipulated with the help of a wideband.

That said---these items are like $500 ---A Custom tune is a much better solution. These are only useful if there is no ECU specific solution for you.

 

What a post...imagine that this is your first post...welcome to 6speed...i will retune the DME for new values...also in the future i plan to switch to proto style intake...But i want first to find a solution to OEM maf problem...

 

Cannotnot attest to the validity of your first post, its above my level of knowledge, but man, nice first post, did you join just to answer this question, I like the enthusiasm keep it up, rep for you.