MAF tuning on a dyno

[Dale McPeters]

Lee,

One thing that I forgot to mention is that I would suggest setting the WOT fuel multipliers to 1 while dialing in the MAF curve on the dyno. Also datalog your load to make sure the MAF does not get to far out of hand.
Make your AFR match what is in the base open loop fuel table if possible. That way you do not have to mess with the maf again...

Below is a quote that I had saved from one of David Posea's post from a while back....in 2001 or so I think...maybe this will help you out a little...

Taken from one of David Posea's great posts !!
*********************************************
OK, there are three stages to this, and you'll need a wide-band and
some means to log MAF voltage or A/D counts.

First we'll tackle the idle. Enter your transfer function, and crank
the car. Turn off the adaptive fuel control. When the car idles, look
at the MAF voltage. If you can datalog look at short term fuel trim.
If not, look at the wideband. Now adjust the MAF function so the fuel
trim is 0% (as close as you can get anyway), or the wideband is
14.64:1 . You'll want to adjust the transer function right at the MAF
voltage you logged. Now set the idle speed a few hundred rpms higher,
and do the same thing. Smooth out the points in between your target
points for a smooth curve. Increase the idle rpm again (with the
tuner, not your foot) and repeat. You can get up to about 2000 rpms
that way.

Now we do the same thing except we go to part throttle. A dyno would
be really helpful here!!! Hold the rpms steady to get the data, then
adjust the transfer function. Notice we are working from the bottom
up, so the upper calibration isn't important (yet!!!). Once you get
short term trim near 0 at part throttle it's time to tackle WOT.

For WOT you can either look at the commanded A/F ratio (lambda) on a
datalog, or set all of the WOT adders to 0 and the multipliers to 1.
You want the EEC to use the A/F ratio set by the stabilized open loop
table. Set those values to what you want the A/F ratio to be.

Now make a dyno pull and log the actual A/F ratio. You'll also need
to know the MAF voltage at various rpms.

Look at your A/F chart and write down the MAF voltage every 1000
rpms. Above that write the commanded A/F ratio. Divide the commanded
ratio by the actual ratio and adjust the MAF function at that voltage
point by the result. If we commanded 12:1 and got 10:1 we have to
adjust the transfer function by 12/10, or 12%. Smooth the points in
between the ones you calculate. It shouldn't take more than 3 or 4
pulls to get the transfer function dialed in.

BTW, set the global spark adder to -10 or so to be safe until the A/F
ratio is dialed in.


I watched this done about 12 times over the weekend, and it yielded
nearly flat A/F curves on all of the cars And they idled pretty
good too.

David

[QWKSNKE]

Dale,
My WOT fuel multiplier vs RPM should already be set to 1.

In regards to the load comment in your email, I will have to double check but I believe it is real close to being correct. The D-1 does make boost fairly early

[Dale McPeters]

It must make a lot more boost than what I thought around 2000 rpm as it looked like a KB or turbo curve.....

[QWKSNKE]

Originally Posted by David Posea

First we'll tackle the idle. Enter your transfer function, and crank
the car. Turn off the adaptive fuel control. When the car idles, look
at the MAF voltage. If you can datalog look at short term fuel trim.
If not, look at the wideband. Now adjust the MAF function so the fuel
trim is 0% (as close as you can get anyway), or the wideband is
14.64:1 . You'll want to adjust the transer function right at the MAF
voltage you logged. Now set the idle speed a few hundred rpms higher,
and do the same thing. Smooth out the points in between your target
points for a smooth curve. Increase the idle rpm again (with the
tuner, not your foot) and repeat. You can get up to about 2000 rpms
that way.

Dale,
Do I have to have a wide band to perform this part or will using the kamrf's get me in the ball park?

[Dale McPeters]

Originally Posted by QWKSNKE

Dale,
Do I have to have a wide band to perform this part or will using the kamrf's get me in the ball park?

You can use the kamrf's to get in the ball park for the idle part. But do not do this until I/we get through with the injector stuff as this will effect the idle AFR etc.

[fireguy50]

Originally Posted by QWKSNKE

Dale,
Do I have to have a wide band to perform this part or will using the kamrf's get me in the ball park?

without a WBO2 I would write down the KAMRF #'s and changes you want to make.
Then clear KAMRF and let it relearn, to see if it's correcting the same potential issues.

But like Dale said; you want injector, CID, and load scaling nailed down before you start scewing MAF numbers

[QWKSNKE]

Originally Posted by Dale McPeters

You can use the kamrf's to get in the ball park for the idle part. But do not do this until I/we get through with the injector stuff as this will effect the idle AFR etc.