I am looking for anyone who has a correlation between the max MAF 11,250hz & 350gm/s and rwhp.


I have done a search on both websites.... but only found one post:
Harlan mentioned 100Hz ~ 130fwhp... anyone have any comments?

Thanks

 

100 g/s on an unmolested (ie accurately reading MAF) = ~130 FWHP

The frequency that equals that is a function of the MAF itself, nothing more.

 

ahh ok..... thanks man

 

There are at least two 85mm GM MAFs out there.

The truck MAF in its natural state runs a lot richer than
the stock F-body MAF (i.e. its output frequency is higher
for a given airflow than F-body). This MAF is the base
unit SLP uses, by adding a resistor across the bridge the
frequency can be decreased and the mixture made more
lean in F-body applications.

The Z06 MAF (as I understand it) will make an F-body
run lean (low output frequency per airflow).

If you are up against the PCM frequency table or
compute limits, you would want a MAF that outputs
less frequency per airflow, thus representing more
airflow at its frequency limit. The Z06 would probably
be a better unit than the truck MAF in this respect,
I reckon. If that weren't enough flow range you could
do the resistor trick on top of that (but you would have
to be figuring out your own cal table on your own).

The MAF frequency/flow curve is not linear at all. It
looks more parabolic. There was a post on here a while
back that linked to some 'Vette board that had the
freq/flow curves for three different MAFs in a write-up.
There was I believe a regressed function for each of
them as well as a graphical comparison.

Do a search in this forum and you should turn it up.

 

Thanks for the reply...

Yes i am running MIGHTYMOUSE's old 85mm maf.. uncalibrated.
I copied the exp. maf curve from one of his files he sent me. It ends right at 349g/s at 11,250Hz. Before i put the new curve in, the car was running pig rich.

I am gonna check the vette boards though.

 

Is there a nice writeup somewhere about this resistor trick? I have a 98 Z28 with Holley Power Shot, SLP lid, and SLP MAFS. 12 Bolt Moser 3.73 rearend, but otherwise Stock.

 

I have gotten Z06 and truck MAF tables from people
that are nearly identical and if you are Editing you
could just substitute them (cropped for the appropriate
PCM) and forget the resistor.

If you want to use the big MAF on a stock F-body program
then you just have to solder a 2.7Kohm resistor as shown
here:

http://community.webshots.com/album/95429402bLraTX

A '98 might prefer a little leaner, but the next commonly
available step downward is 2.2Kohms which might be a
little severe, a less-common 2.4K (carbon) or 2.499K
(metal film precision) might be better for you. Just have
to cut-and-try, watch LTFTs once-settled with some sort
of scanner / logger and when your 1/2 to 3/4 throttle,
high RPM LTFT starts staying about -1 to -2, you're good.
The slide show shows how I made a pigtail and work-box
to keep from soldering inside all the time, if it looks like
a lot of attempts then you might go that way (or not).

 

By the way, I'm still looking for someone to give me a
key on, engine off MAF frequency reading from a
virgin Delphi 85mm... just for science' sake, I need to
compare to a used unit I picked up that seems a bit
"large" at zero airflow.

 

The dip switches are a good idea. I was thinking of using an external potentiometer in the same manner. Do you think that I will be able to guess a good resistor value? I don't have any scanning tools and don't want to buy one. Without the scanning tools, I think I will limit my resistor values and nix the pot idea.

I think I'll put 2.2k, 2.4k, and 2.7k as selections...maybe with some intermediate values as well - it helps to be an electrical engineer!

 

I eventually got rid of the DIP switches (after
first discarding the potentiometer) because
they really offer little benefit; the "settling
time" of LTFTs is hours or days, and the time
to pull and resolder is minutes. But I kept the
little "doghouse" just to keep from being inside
the throat all the time (less to go wrong, no
solder ***** to be sucked up later, etc.).

2.7K is what SLP uses. If you took and made
a chain from 2.2K, up by 100 ohm increments,
and used the 8 DIP switches to short 100
ohmers individually that would give you a really
good range and, perhaps importantly, be fairly
benign if one switch opened up or had a
vibration sensitivity (only a 100-ohm delta).
Such a chain would let you go 500 below
(leaner) to 800 above (richer) the SLP '01-'02
fairly-neutral setting, which is about ideal.

Knowing they don't allow either one (pots
or mechanical DIP switches) on launch grade
hardware, I kept just the robust stuff in the
end.

 

For clarification sake... is the Z06 MAF the same as a truck MAF but without the screen?

jimmyblue,
I went out and checked my truck's MAF Hz for you. It reads 0 Hz with key on and engine off. It's a stock, unmodified Delphi MAF on 2003 truck.

 

Thanks! The Delphi (also a truck MAF) I got off eBay
and it sits there squealing along at 3kHz (more or less).
I thought that was way off the map.

Truck MAF (5.3L, not the older one for the 6.0L) and
Z06 ('01) MAF tables appear almost identical, they are
apart a little all the way up, but not by much (and
probably due to screened / descreened). Nothing like
the difference between small truck and F-body.

I have been collecting MAF tables here and there. This is
what I have so far. Note that some of them look pretty
bogus in the low end; where I put 0.0 there was no data
and some where there is data, the data "doesn't look right".
Like huge discontinuity between 1450 and 1500Hz values.
So caveat emptor and all that.


MAF Type 6.0L truck 5.3L truck Truck ZL1 02 01 Z06 98 Fbody 99-00 Fbody 02 Fbody

freq Hz flow gm/s flow gm/s flow gm/s flow gm/s flow gm/s flow gm/s flow gm/s
750 0 0.14 0.2 0.39 0 0 0.39
800 0 0.2 0.27 0.41 0 0 0.41
850 0 0.27 0.34 0.44 0 0 0.44
900 0 0.34 0.41 0.46 0 0 0.46
950 0 0.41 0.49 0.48 0 0 0.48
1000 0 0.49 0.58 0.5 0 0 0.5
1050 0 0.58 0.66 0.52 0 0 0.52
1100 0 0.66 0.73 0.54 0 0 0.54
1150 0 0.73 0.81 0.56 0 0 0.56
1200 0 0.81 0.89 0.58 0 0 0.58
1250 0 0.89 0.97 0.6 0 0 0.6
1300 0 0.97 1.05 0.62 0 0 0.62
1350 0 1.05 1.13 0.64 0 0 0.64
1400 0 1.13 1.21 0.66 0 0 0.66
1450 0 1.21 1.29 0.68 0 0 0.68
1500 1.59 1.29 1.59 1.48 2.32 2.32 2.32
1625 1.88 1.59 1.88 1.8 2.7 2.7 2.7
1750 2.2 1.88 2.2 2.13 3.15 3.15 3.15
1875 2.58 2.2 2.58 2.49 3.65 3.65 3.65
2000 2.99 2.58 2.99 2.89 4.16 4.16 4.16
2125 3.45 2.99 3.45 3.33 4.73 4.73 4.73
2250 3.95 3.45 3.95 3.8 5.36 5.36 5.36
2375 4.5 3.95 4.5 4.34 6.05 6.05 6.05
2500 5.1 4.5 5.1 4.91 6.8 6.8 6.8
2625 5.76 5.1 5.76 5.54 7.64 7.64 7.64
2750 6.46 5.76 6.46 6.22 8.53 8.53 8.53
2875 7.23 6.46 7.23 6.95 9.47 9.47 9.47
3000 8.06 7.23 8.06 7.73 10.43 10.43 10.43
3125 8.95 8.06 8.95 8.56 11.45 11.45 11.45
3250 9.9 8.95 9.9 9.45 12.56 12.56 12.56
3375 10.9 9.9 10.91 10.38 13.78 13.78 13.78
3500 12 10.91 11.98 11.38 15.09 15.09 15.09
3625 13.1 11.98 13.14 12.45 16.49 16.49 16.49
3750 14.4 13.14 14.39 13.6 17.98 17.98 17.98
3875 15.7 14.39 15.74 14.85 19.58 19.58 19.58
4000 17.2 15.74 17.19 16.21 21.26 21.26 21.26
4125 18.7 17.19 18.74 17.7 23.03 23.03 23.03
4250 20.4 18.74 20.39 19.32 24.91 24.91 24.91
4375 22.1 20.39 22.14 21.02 26.88 26.88 26.88
4500 24 22.14 23.99 22.77 28.95 28.95 28.95
4625 26 23.99 25.95 24.54 31.13 31.13 31.13
4750 28 25.95 27.99 26.43 33.4 33.4 33.4
4875 30.1 27.99 30.14 28.41 35.78 35.78 35.78
5000 32.4 30.14 32.38 30.49 38.28 38.28 38.28
5125 34.7 32.38 34.71 32.66 40.93 40.93 40.93
5250 37.2 34.71 37.16 34.95 43.73 43.73 43.73
5375 39.7 37.16 39.73 37.36 46.69 46.69 46.69
5500 42.5 39.73 42.5 39.9 49.8 49.8 49.8
5625 45.4 42.5 45.41 42.62 53.07 53.07 53.07
5750 48.5 45.41 48.47 45.48 56.51 56.51 56.51
5875 51.7 48.47 51.67 48.5 60.11 60.11 60.11
6000 55 51.67 55.02 51.66 63.88 63.88 63.88
6125 58.5 55.02 58.48 54.98 67.8 67.8 67.8
6250 62.1 58.48 62.1 58.44 71.9 71.9 71.9
6375 65.9 62.1 65.86 62.05 76.16 76.16 76.16
6500 69.8 65.86 69.77 65.82 80.58 80.58 80.58
6625 73.8 69.77 73.82 69.73 85.16 85.16 85.16
6750 78.06 73.82 78.06 73.8 89.91 89.91 89.91
6875 82.48 78.06 82.48 78.03 94.83 94.83 94.83
7000 87.07 82.48 87.07 82.4 99.93 99.93 99.93
7125 91.82 87.07 91.82 86.94 105.2 105.2 105.2
7250 96.74 91.82 96.74 91.63 110.65 110.65 110.65
7375 101.8 96.74 101.82 96.49 116.28 116.28 116.28
7500 107.1 101.82 107.08 101.51 122.12 122.12 122.12
7625 112.5 107.08 112.48 106.71 128.15 128.15 128.15
7750 118.1 112.48 118.07 112.09 134.38 134.38 134.38
7875 123.8 118.07 123.83 117.63 140.87 140.87 140.87
8000 129.8 123.83 129.76 123.35 147.59 147.59 147.59
8125 135.9 129.76 135.87 129.24 154.53 154.53 154.53
8250 142 135.87 142.17 135.3 161.72 161.72 161.72
8375 148.6 142.17 148.61 141.53 169.15 169.15 169.15
8500 155.3 148.61 155.26 147.87 176.82 176.82 176.82
8625 162.1 155.26 162.11 154.41 184.73 184.73 184.73
8750 169.2 162.11 169.17 161.15 192.82 192.82 192.82
8875 176.4 169.17 176.44 168.08 201.15 201.15 201.15
9000 183.9 176.44 183.94 175.22 209.74 209.74 209.74
9125 191.7 183.94 191.72 182.58 218.61 218.61 218.61
9250 199.8 191.72 199.8 190.23 227.77 227.77 227.77
9375 208.1 199.8 208.06 198.21 237.26 237.26 237.26
9500 216.6 208.06 216.62 206.34 247.08 247.08 247.08
9625 225.4 216.62 225.44 214.8 257.27 257.27 257.27
9750 234.5 225.44 234.52 223.52 267.86 267.86 267.86
9875 243.9 234.52 243.89 232.52 278.88 278.88 278.88
10000 253.5 243.89 253.45 241.83 290.34 290.34 290.34
10125 263.2 253.45 263.21 251.34 302.31 302.31 302.31
10250 273.2 263.21 273.23 261.13 314.81 314.81 314.81
10375 283.6 273.23 283.55 271.19 327.88 327.88 327.88
10500 294.2 283.55 294.15 281.53 341.56 341.56 341.56
10625 305.1 294.15 305.06 292.15 355.91 355.91 355.91
10750 316.3 305.06 316.32 303.05 370.95 370.95 370.95
10875 327.9 316.32 327.93 314.25 386.76 386.76 386.76
11000 339.9 327.93 339.92 325.73 403.36 403.36 403.36
11125 352.32 339.92 352.32 337.51 420.83 420.83 420.83
11250 365.16 352.32 365.16 349.59 439.2 439.2 439.2
11375 378.47 365.16 378.47 361.96 439.2 439.2 439.2
11500 392.3 378.47 392.3 374.64 439.2 439.2 439.2
11625 406.7 392.3 406.7 387.63 439.2 439.2 439.2
11750 421.7 406.7 421.7 400.92 439.2 439.2 439.2
11875 437.34 421.7 437.34 414.53 439.2 439.2 439.2
12000 453.69 437.34 453.69 428.46 439.2 439.2 439.2

 

I just took apart my SLP MAFS and it's got a 1.4k resistor in there, not the 2.7k like in the picture here http://community.webshots.com/photo/...95432725rDoEwQ

I'm still going to add the 2.2k - 2.9k dip switch ladder and see what happens. Any idea why the MAFS for my 1998 had such a low resistor value?

 

They wanted to lean it out more, just like the GMAF
and others, from back in the day when the ghetto
tune was the only tune you could do and LS-1s
were all factory over-rich at WOT.

Thanks for the info, I always wondered what was in
the '98-'99 version to make the different P/N needed.

 

im suprised the difference in values for the 98-00 maf as well.

I knew they were a lot leaner than the 01-02 versions, but that is a large % difference.

Since we are on the maf topics, anybody know if you could put say, a 500 ohm resistor on the maf, in that location, and get the unit flowtested/readout?

Im trying to find a good solution for about 550 hp in my 98 car, with the 11250 hz maximum. I will have hptuners/edit/new programmer coming out soon , so programming the computer won't be a problem. It was just an idea i was thinking about yesterday, after finding some old data on mafs and pressure drops.

Ryan.

 

www.ls1howto.com has the tables for the screened and unscreened 85 mm MAF sensors. Look under the Maf conversion writeup for vettes and the Fbody

 

I've been collecting the hardware to do a poor man's
flow bench, one thing I want to be able to do is MAF
flow/freq calibration testing. But getting to accurate
will be challenging, I expect I will use a stock 75mm
MAF as my "golden unit". I got an 85mm for that but
it seems to be messed up at the low end (what do
you expect off eBay?).

Decreasing resistor value makes more lean. However
you can also make more lean by light porting of the
housing, and if you are going to bother with a high
quality calibration after the fact you should take all
possible advantage of this - descreen, port to the
sensible (robustness) limit and then skinny it down
to keep the frequency below 11250Hz at whatever
you think your max mass airflow will be, by the
resistor value.

It would be spiffy to find a place that was really high
accuracy and could pull a +/-1% flow / frequency
table "on the numbers" for frequency. But 1% flow
accuracy I believe is hard to come by instrument-
wise. I'd pay to have it done once, anyway, for my
flow bench "embedded" MAF. Anybody know a good
"flow shop" that would fit the bill?

 

Who knows, maybe my color reading skills were off. I'm going to read it with a meter tonight, the '98 resistor may be different. But I can't imagine I read it that differently.

Assuming it is actually 1.4k, I can parallel the dip switch thingy in my car to bring it into 1k - 1.4k range and see what that does.

SES lights suck.

 

1.4K is an unusual color code. In fact I've never
seen one.

brown/red/red/gold is 1.2K 5%, common.
brown/green/red/gold is 1.5K 5%, common.
brown/gray/red/gold is 1.8K 5%, common.
red/black/red/gold is 2.0K 5%, common.
red/red/red/gold is 2.2K 5%, common
red/yellow/red/gold is 2.4K 5%, less common but only
a bit off from the 2.7K (red/violet/red/gold) used on the
later model.

The resistor can get somewhat discolored over time,
in that environment, so measuring may be the only way
to tell (say) brown from red reliably....

 

jimmyblue, I don't know of a flow shop, but these guys might be able to help you with setting up a flow bench... erdco