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| | | |-+ Ignition Timing in A9L vs. A9P vs. X3Z - VRISTANG
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Author Topic: Ignition Timing in A9L vs. A9P vs. X3Z - VRISTANG  (Read 18172 times)
mighty mouse
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« on: March 14, 2007, 03:41:19 pm »

An awesome post by VRISTANG . . . the actual thread

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
 

 


 
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« Reply #1 on: December 05, 2015, 09:43:28 am »

i used the a9p in my maf conversion on my 351 4x4 and anything past 2/3 throttle, no matter what fuel will ping like a case of coke bottles under the hood.

thats with 76mm maf call'd to 24's along with a bunch of other stuff............there may be a problem with my fuel system, not sure. fuel pressure is good maybe my fpr is bad, havent tested that yet.
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