When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
You guys can laugh all you want, diffusers in front of MAF's are commonplace in the automotive industry.
Originally Posted by GT6ixer
These devices are "marketed" to increase fuel mileage by creating a "tornado" of air to help with air fuel mixing. Snake oil. First off, in its position, it is so far upstream of where the fuel gets added that any "spinning" air it creates will not remain spinning as it travels through throttle body, into the plenum chamber then through the individual intakes. One of the goals with ram air intakes is to minimize the loss of dynamic pressure. This device, one, adds blockage via added material in the intake flow path, and two, by attempting to "spin" the airflow it removes energy (i.e. pressure) from the flow. Bad all the way around. Your call, but I'd toss it in the round file if I found one on my car.
Again, read my post.
Any benefit from these devices is to even out the air flow over the sensor wire, not increase any kind of air flow, just allow for a more consistent flow of air over the sensor.
Often though, as in the case of the Murf928 cars, this difference is during cruise, idle, etc... not top end.
Every modern car I can think of I took apart already had some kind of diffuser directly in front of the MAF, so yes in most modern cars adding another device will offer zero benefits.
Our best guess as to why a stock 928 sees no benefit from such a device is the air filter placement, shape of the airbox, and the direct flow path through and out of the MAF....imagine that, Porsche knew what they were doing.
When Mike Schmidt (Z) brought these to our attention we laughed our collective asses off (me, Tim Murphy, Turbo Todd...) but as usual Mike go the last laugh.
Then we started to take apart every car we had at the house that day (BMW, couple of GMC's, SAAB, some generic Chevy sedan) all had a MAF diffuser........
This is what the "honeycomb" looks like we install in the MURF928 "elbow" before the MAF.
Here are various OEM applications of similar devices from BMW, Porsche, Jaguar, GMC, and SAAB......
I installed the honey comb in my MAF while we were dynoing a few months back. There was zero difference between having it in and not. We were just goofing around to see what, if any, difference there would be since I've got the elbow right on top of the MAF.
You guys can laugh all you want, diffusers in front of MAF's are commonplace in the automotive industry.
Again, read my post.
Any benefit from these devices is to even out the air flow over the sensor wire, not increase any kind of air flow, just allow for a more consistent flow of air over the sensor.
Right. All of those even out the air flow. Smooth or straighten it, if you will.
Smooth, even, consistent airflow across a MAF gives better readings.
How much benefit is dependent on a lot of things, mainly how turbulent the airflow is without the diffuser.
As was noted, the stock airbox flows pretty smoothly.
But that "Tornado" piece of crap does the opposite. It creates turbulence, where you least want it.
Maybe the claims of 'increased fuel economy' are because it screws up the airflow enough that the MAF misreads and runs the engine way lean (less fuel). Not the best thing for the engine, though.
And I have to ask - What weight snake oil is best? Does Amzoil make any?
The only one that has me scratching my head is the Jaguar one above. The first time I removed the MAF from our XK8 I stood there for a while staring at it and it made me think of the "tornado" device I saw on a 3AM infomercial.
If I'm not mistaken in my knowkedge, the 928 MAF makes its mixture corrections by the incoming air cooling a wire, which is located inside a venturi in the very center of the MAF.
The device in question here, has the vanes all coming together in the very center. Seems like this particular device would block flow through the center of the MAF, resulting in the MAF measuring less airflow than what is actually taking place.
Hacker's pictures of a honeycomb diffuser would not block the center of the MAF. However, the "straightening" of the airflow could affect the airflow through the center portion of a MAF.
My guess would be that anything that is added to change the airflow through a stock MAF, would require recalibration of that MAF.
To me the honeycomb devices are there not so much to straighten the flow but to act as a flow dampener to reduce turbulent flow directly over the MAF cooling wire (temp sensor). The process of forcing the air through each of the honeycomb "tunnels" (or screen mesh) breaks up large scale turbulence which could lead to airflow separation over the sensor resulting in underestimation of the actual airflow. After being forced through the tunnels the flow turbulence is on a much smaller scale which doesn't lead to separation over the sensor. Now these small scale eddies will eventually grow into larger eddies (see picture below), which is why these devices are placed directly in front of the sensor. If they were moved upstream even a few inches they would be much less to non-effective in their purpose.
The dampening effect they have, I believe, is mainly to account for sudden changes of airflow due to acceleration and deceleration in normal driving. These changes cause pulses in the airflow which exacerbate the turbulence through the intake ducts. The honeycomb screen in effect dampens or smooths out these abrupt mass flow changes so that the MAF sensor can more effectively evaluate the instantaneous mass flow. If a car operated at constant speed and constant rpm the flow through the intake will come to a relative equilibrium with respect to its turbulence level. In this case if you suddenly removed the honeycomb screen, the change the MAF sensor would see would be minimal with most of the change being due to removal of blockage and less due to any decrease in flow straightening over the sensor. This I believe is what Sean experienced during the dyno testing where he did not see a change with the screen installed. During a dyno pull the rpm changes are very gradual and don't lead to pulse induced turbulence. However in regular stop and go driving, these pulses are often and having a screen likely pays dividends in fuel efficiency.
My guess would be that anything that is added to change the airflow through a stock MAF, would require recalibration of that MAF.
You don't need to guess. I have Kevin's calibration offset numbers. As I wrote, according to Kevin's numbers throwing that thing in puts the calibration wildly out-of-spec.
The device in question here, has the vanes all coming together in the very center. Seems like this particular device would block flow through the center of the MAF, resulting in the MAF measuring less airflow than what is actually taking place.
I'm not even sure it's that 'good.' I took a picture, below, as close to down the center as I could. The hot-wire section of the MAF isn't actually in the center of the housing. So, with this Tornadobulator installed, the center of the 'vortex' isn't even close to the center of the hot-wire section.
What you don't see clearly is that the vanes of this Frankenpeller are up against the hot-wire section housing. Air's pretty-much getting deflected away from about half the wire. There's no way you'll get uniform cooling across the wire.
You don't need to guess. I have Kevin's calibration offset numbers. As I wrote, according to Kevin's numbers throwing that thing in puts the calibration wildly out-of-spec.
What you don't see clearly is that the vanes of this Frankenpeller are up against the hot-wire section housing. Air's pretty-much getting deflected away from about have the wire. There's no way you'll get uniform cooling across the wire.
The best thing you can do with Herr Frankenpeller is to send him to an impoverished proctologist to help him improve his vistas!
04-03-2018, 09:42 AM
