[Shotimes] Re: 76mm MAF with 19# injector calibration?

[John Weidenbenner]

On the stock SHO V6 MAFS, here's some comments Jim Kempf sent me recently on
intake restrictions :

I do not have such a plot of restriction or voltage, but know that the
restriction through this should be ~ 3-4" H20 at the rated flow of the
engine.

Restriction Test:
Connect the MAFS to a flow stand with some good ol' fashion duct tape,
fashion an 'ideal entry' or 'bellmouth' at the side normally facing the
filter housing to avoid unrealistic 'entrance losses', pull air through the
housing up to the rated flow of the engine (~330 scfm or whatever you think
this is), measure the pressure drop (drop in pressure in the air compared to
atmospheric pressure).  Measurement location should be immediately
downstream of the MAFS body.    Some flow stands use pressure taps, others
use LFE (laminar or linear -- I forget -- flow elements).  Either way, this
is the only correct way to evaluate restriction in an air induction.

It is fairly well known in the industry that for naturally aspirated engines
(not turbocharged) for every 3-4" H20, the engine looses ~ 1% power.  So a
stock 220 hp SHO engine, would have 224.2 hp if it didn't need a MAFS
(neglecting frictional losses which are only a very, very small portion of
restriction).

For a larger sized Pro-M sensor to work (a bunch of guys who used to work at
our company), they must significantly recalibrate/tune the MAFS output
(voltage) to mass flow rate (kg/hr) to match the original 55 mm MAFS.  The
only exception....sometimes Pro-M, adjusts the curve slightly at the top end
to lean/richen the A/F slightly, if they know where the stock A/F ratio is
relative to 12.5:1 (typically the A/F ratio that is the best compromise that
delivers peak power).

----- Original Message -----
From: "Alan Fanning" <Awfanning@earthlink.net>


> I don't want to make this sound like I'm harassing you, or dissing C&L,
> because that's not my objective. What I'm trying to say is that the reason
> one upgrades a MAF is (usually) to free up some of the horsepower lost due

> to pressure drop thru a stock intake. Achieving proper A/F ratio with the
> replacement MAF is necessary, but not sufficient, to achieving this end.
You
> still have to have lower pressure drop through the MAF for it to be an
> improvement over the stock setup.
>
> Now, I have no doubt that a C&L 76mm MAF will flow better than a Ford 55mm
> MAF, but the comparison to a Pro-M MAF, for example, is not obvious.
Since
> I, and others, are trying to build a database of info on aftermarket
MAF's,
> it would be handy to have comparable flow data rather than hp claims. As
an
> example of the latter, I was on the phone with Scott in the tech support
> group at Pro-M yesterday. When he told me swapping out the stock 55mm MAF
> for one of their 75mm Bullet's with cone filter would add 22 hp to a stock
> SHO I just about fell out of my chair. We should be so lucky!
>
> It's hard for me to imagine that anyone developing a new MAF sensor would
> not test it on the flow bench at some point. This is standard procedure
for
> intake systems - hell, the 1-barrel carb on my F150 was flow tested before
> and after it's recent rebuild.  If they haven't done this it's a little
> puzzling as to why not.
>
> By the way, without individual calibration of the MAF, there is also a
> question as to how close the OEM electronics were set at the factory (or
> whether it has changed by, say, the sensor being dropped on the floor).
>
>     Alan
>
> PS What's the retail/street price on a new C&L 76mm MAF?
>
> > Lee seems to know his physics and his MAFs, so you might call it a crap
> > shoot, but the only variable should be the consistency of the stock MAF
> > sensor.  I, for one, am very happy with the setup, however I will still
do
> > my own air/fuel tests on the wideband O2 sensor as soon as I can, and
post
> > the results.
> >
> > Gary