vristang

Again, the A9P does not have a significant advantage...
Here is a more thorough discussion from my site...
http://www.freewebs.com/vristang/eecivfaqs.htm


A 3-way Comparison of Ford EEC-IV Computers: A9L, A9P, X3Z

WOT Spark Advance vs. RPM – FN131
A9L
RPM_____0____0____1,000___1,800___2,150___2,600___ 3,500___5,000___16,384
Degrees___8____8_____8______18.5____21.5____22.5__ ___22______25_____25
A9P
RPM______0____0____0______1,600___2,250____2,600__ _3,500___5,000___16,384
Degrees___18____18____18_____18______22______23___ ___22______26______26
X3Z
RPM_____0____0____1,000___1,800___2,150___2,600___ 3,500___5,000___16,384
Degrees___8____8_____8______18.5____21.5____22.5__ ___22______25_____25

In FN131 (WOT vs. RPM), notice that the A9P does add 10* of advance at lower WOT rpm's. If proper gearing is being selected by the driver, then a manual t5 Mustang should not see WOT below 1,600 rpm. For this reason using an A9P in a t5 Mustang will provide minimal performance gain due to ignition timing advance.

Most likely Ford used the extra 10* of advance in the A9P to help ‘off the line’ performance in the automatic Mustang. Using an A9L in an automatic equipped Mustang would sacrifice this added timing. This is why an A9L is not recommended for AOD equipped Mustangs.

Below are a couple more WOT Ignition Timing tables. The influence of these tables will be less significant than FN131, as the following tables are ‘Adders’ to Total Ignition Timing.
As ‘Adders’ the following values are added to the WOT table, to arrive at Total Ignition Timing. For example, in an A9L at WOT, ECT at 246F, and 5,000rpm the total timing will be (25* - 4*) 21*.
Also, it should be noted that the computer assumes the distributor is always set at the stock 10* ignition advance setting. For example, advancing the distributor from the factory 10* of advance to 14* will add an additional 4* to the total timing.
Using the same example from above, this will return the total timing to 25* (making up for the 4* of retard from FN134 at an ECT of 246F).

WOT Spark Advance vs. ECT – FN134
A9L
ECT_____-256____86____120___200___236___246___254
Degrees____3_____3______0_____0____-2_____-4____-4
A9P
ECT_____-256____86____120___200___236___246___254
Degrees____3_____3______0_____0____-2_____-4____-4
X3Z
ECT_____-256____86____120___210___236___244___254
Degrees____3_____3______2_____0____-2_____-4____-4

WOT Spark Advance vs. ACT – FN135
A9L
ACT_____-256____-256____-256___-256___150___240___254
Degrees____0______0_______0______0_____0_____-6____-6
A9P
ACT_____-256____-256____-256___-256___150___240___254
Degrees____0______0_______0______0_____0_____-6____-6
X3Z
ACT_____-256____-256____-256___-256___160___240___254
Degrees____0______0_______0______0_____0_____-6____-6

WOT Spark Advance vs. BP – FN133
A9L
BP_______0____23.5____26.5___27.75___31.875
Degrees__12_____4_______4______0______0
A9P
BP_______0____23.5____26.5___27.75___31.875
Degrees__12_____4_______4______0______0
X3Z
BP_______0____23.5____26.5___27.75___31.875
Degrees__12_____6_______5______0______0


Now some of the Part Throttle Ignition Timing Tables

Spark Table Base – FN901
The computer always assumes the base ignition timing to be set at 10* of advance.
Thus, this Table includes the factory 10* of the base timing set at the distributor. For example, an A9L with 14* set at the distributor will see 25* at 75% load and 4,000rpm (21* in the table, plus 4* over the initial of 10* = 25*). Likewise, an A9L with 10* set at the distributor will see 21* at the same load/rpm.








Part Throttle Spark Adder – FN1133

mcginnt

thanks a lot for the responses, i have no intention of converting to SD, i just think that i may have gotten a SD computer.

would sticking a SD computer in a MAF car make it run rich becuase its not reading any correct info from the bap or mas? because my car has been running really really rich and i cant find any other reason besides maybe a incorrect computer.
i'd hate to spend $100+ on a computer that wont fix my issue. i might have found one for 70 shipped which isnt so bad... still...

vristang

Did the rich problem start with the computer change?
Have you pulled the codes from the ecu?
Why did you replace the computer? MAF upgrade?

jason

mcginnt

long story short...

i was driving and stopped at a light, made a right and car turned off. no idea why. towed it back and checked the usual... a buddy of mine suggested the computer as he saw that happen before... so me, being ignorant at the time, got a new one from kragen. didnt fix it. ended up being a broken wire off my starter selnoid... fixed it and car ran really rough. idled up and down and blew black smoke...
replaced different things (fuel filter, fuel pump, sparkplugs, wires, dist cap and rotor...) nothing.
i found out that my mass air sensor was literally broke (one of the two wires that goes into the intake was broke) so i got a new one and fixed nothing. ive also put new bbk headers, bbk xpipe, hiflow cats and flowmasters...

i have my BAP unplugged and the cars runs okay, not 100% but ok, if i plug it in, it starts to run really rough again with black smoke (rich) coming out the back. i know there is something wrong, and ive replaced some older parts but the EEC thats in there has no writing on the lables to help me identify what kind of computer it is. which is why i assume its the wrong one.

ok that didnt seem too short, but it could have been longer.

moral to the story... i still dont know whats wrong with it. its killing me because its my daily driver.


as per the codes, i ran them and got...
KOEO - BAP plugged in (81 82 81 82 - 1 - 22 22)
KOER - BAP plugged in (no codes - car ran to rough and couldnt hold a steady idle)

KOEO - BAP not plugged in (22 81 82 - 22 81 82)
KOER - BAP not plugged in (98 22 - 98 22)

i went to re run my codes the other day but i wasnt getting any and it was getting late so i stopped.


overall, it basically started when my computer was switched out (amoung other things), and i did not convert this car to mass air.
its a 1988 GT vert 5spd. from what ive heard that year was half SD and half MAF. maybe i got a wrong computer sent to me?

offtopic (when you turn your key backwards, its acc mode right? mine wont go backwards.)

Chitown racer

Well in 1988 only Mustangs built for sale in California came with a MAF setup the rest of the US was SD for one more year. Chances are if you went to the parts store and just told them you had an 88 Mustang then they assumed it was an SD car and you got an SD computer. I'd take it out and take it back to them and tell them they screwed up and you need a computer for a MAF equipped car.

vristang

It does sound like they sold you the wrong computer...

If you explain to them that only CA cars had MAF, and that your car was MAF, then they may take your current ecu on exchange for the right MAF ecu.
I kinda doubt it though... You may have to buy a new one...

Let us know how it works out...

Best of luck to you,
jason

mcginnt

ok, so i just got a A9L computer and it fixed my rich running condition

i need to adjust the timing now, i believe its stock at 10*, should i bump it up or retard it a little?? differences?

5.0stanger

I would bump it to 14* and call it a day.....but you will have to run premium fuel.

vristang

Glad to hear you sorted it out!

Every car is different with timing. Advance it a little until you hear detonation, then back it off 1-2 degrees. Set the timingwhile burningthe fuel you will ALWAYS use.


jason

mcginnt

i know this is kinda a noob question, but what is the difference if i make it run at 12* compared to 8*?