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Re: MAF and 89 Vet stuff
Mark,
Thanks so much for the reply and explanation. I am still a little fuzzy
on the MAF tables and what they represent. In each of the tables 1-6 there
is a scaler. Then there is a table with values listed on the left as
counts. What are counts? The data on the right can be manipulated but what
does it affect? Also I understand the various cell numbers and how they
relate to load or RPM. What if in say cell 10 my BLM was 110. How would I
subtract fuel from that cell?
As to Andrew and his post about the ported MAF, Ed Wright my chip burner
told me the same thing. I swapped in a stock MAF with no difference. My
solution to the lean condition was to enable PE at 45% throttle. Still at
light cruise in 4th and in cell 15, my BLM is 118-120. As I apply more
throttle pressure and engine load increases, my INT jumps to 150-160 with FP
at 43 psi. At 50 psi (line off) the INT goes to 140-145'sh and then PE hits
and IPW jumps way up and everything is great. Now at 50 psi it seems
tolerable with knock retard about 3.5-4.0 degrees.
Back to understanding more about the various tables and what they represent.
Mark, you say you don't fool with the MAF tables but you do fool with the PE
vs RPM tables. Looking at this table, it lists a %change of PE in relation
to various RPM points. This is a percent change from what? This is a
little confusing to me right now.
I see in the software where the injector size can be entered in pounds per
hour like you told me. So from what I gather, this is the single most
important item for a 383 running 30lb injectors. Enter this value and the
ECM recalcs fuel used for open loop operation. Of course I assume that
during closed loop, the O2 sniffer will do the rest.
Ok now to ask a really big question. Some of you tell me you burn 100+
chips to get the prom just right. My assumption of the perfect chip is
shoot for BLM's that are right on 128 or so in all cells, WOT O2 volts
around 880mv and very little if any knock retard that results to a perfect
spark advance map. Am I correct?
I still have lots of questions and I dearly appreciate the long responses I
have received. Also Mark I have the 6 speed with factory 3.33 rears. What
cam are you running and what size injectors?
Question recap:
1. MAF tables do what? Calculate the amount of air based upon a certain
voltage from the MAF? If so what function does the scaler have? What is
meant by counts? If I am right about the calculation of airflow, then you
really never do know the exact amount of air in gms/sec unless the entire
intake system MAF and forward is stock?
2. What is adjusted to increase/decrease fuel in a certain cell?
3. PE vs RPM table. Percentage change from what? What is the base value
if any?
4. Perfect chip assumptions.
5. What cam and size injectors do you have?
6. One last question that I just thought of now. My MAF pegs out at 254
gms/sec. at about 4200 RPM Certainly my 383 will move more air at a lower
RPM. Since actual/calculated airflow is no longer measured by the MAF, what
controls the fuel flow above this?
I hope I'm not overloading the questions. Thanks
Jason Norris
89 vette Super Ram
----- Original Message -----
From: "Romans, Mark" <romans@starstream.net>
To: <jwn@sgi.net>
Cc: <gmecm@diy-efi.org>
Sent: Saturday, August 12, 2000 1:12 PM
Subject: MAF and 89 Vet stuff
> Hi Jason: I may be able to help you. I had saved your messages intending
> to respond, just a time thing you know.
> I will try to go through each of your messages and respond to each
question.
>
> Question 1.
> Questions on MAF equipped 89 Vette. Using Diacom for some time now and
have
> some questions about the different cell numbers used for fuel trims. What
> tables dictate the amount of fuel used in open loop mode? I understand
that
> in closed loop the MAF, O2, etc. determine the proper amount of fuel to
> deliver and adjust the short and long term fuel trims. What is modified
to
> control the fuel delivered in open loop and PE? I assume its the MAF
tables
> but I need educated on what the values represent.
>
> Response. The BL is a group of cells numbered 1-15 in the following order
> (As I consult my hand drawn chart)
> Starting on the bottom left, left to right and each successive row goes on
> top of the prev one. I put the zero's in front of the
> single digit numbers to preserve the spacing.
>
> 12-13-14-15 L F
> 08-09-10-11 O L
> 04-05-06-07 A or O
> 00-01-02-03 D W
> RPM
>
> The rpm boundary numbers stock (These go on the lines between the boxes)
> 1000,1200,2000.
> The flow boundary numbers stock, 14 grm/sec, 22,34.
> These are the block learn memory cells.
> The fuel settings are "Initial fuel*(BLM/128) = adjusted fuel. This is as
> BL takes fuel out (Lower number) or adds
> fuel (Higher number)
>
> I would not really suggest messing with the maf calibration tables much if
> you can avoid it. I have done some small adjustments
> in the first table to add about 10% (Below 30 grams/sec) to compensate for
> the ported maf in my car. Other than that I have the
> injector constant set stock and run about 50 lbs fuel pressure(With vacuum
> line off) at idle. This seems to keep the BL and INT
> close to 128 at all areas.
> At all times the maf is used to calculate the correct amount of fuel, this
> is closed loop and open loop. There are tables to add fuel in open loop
> I have never messed with these. The only fuel table I mess with is PE vs
> RPM. This allows me to command a richer afr when in pe and the 02 sensor
is
> ignored. Diacom says I am commanding about 12.0 to one at WOT, I know
it's
> not really that rich, but then I am maxing out the MAF (255 grms/sec) at
> about 4700 rpm's.
>
>
>
> Question 2.
> I just bought GMEPro and it looks really cool. I understand the basics
but
> need to gain more knowledge. I had posted a question about block learn
> cells 0-15 and what in GMEPro controls the amount of fuel the ECM starts
out
> with. I also want to know how to control open loop idle so when I build
the
> Superrammed 383 with 30 pound injectors I can make the car idle.
>
> Response to question 2.
> See response to question 1. Reset the injector constant, I would set both
> the single fire and double fire to whatever size injector you are using).
>
> Question 3.
> For instance: I have the GMEPro software. There are 6 MAF tables and a
> scalar for each table. What do these affect? It seems by changing the
> scalar you can affect the entire table. The constants are listed as
counts.
> Counts? What is meant by counts?
>
> Second, Say when I build my 383 and install 30 lb injectors. My closed
open
> loop idle will be way rich. How do I reduce BPW at idle with the bigger
> injectors?
>
> Response to question 3. See response to question 1 & 2. If you reset the
> injector constant to 309 lb/hr injectors. The ecm will
> calculate the correct injector pw at idle.
>
> BTW what trans are you using? I have done hundreds of proms getting my
355
> cu in, superram/ 6sp vet dialed in.
> I may be able to help more.
>
>
>
>
> Mark Romans
>
> ICQ#66838770
>
> Chicks dig scars.
> Pain is temporary.
> Glory is Forever.
>
>
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