What AFR/Timing

[Joker Z28]

My car is going to start seeing spray again.
Untill I install the Mallory 685 and microedge controller I am limited to what I can do.
My tune puts my AFR at 12.7-13.0 at WOT what should it be "safe" on a 75 wet shot at WOT?
Also in my tune the timing has been advanced, I am not sure by how much. Now the rule of them is retard the timing 1 degree for every 25 hp or 2 degrees for every 50. So with my advanced timing does the same rule apply or do I need to retard the timing 3 degress (75 shot) plus what was advanced?
Also does anyone have experience hooking up the 685 with a microedge controller?

Thanks in advance

[gregrob]

First off why are you even bothering with a 75 shot? That feels like a strong tailwind...

I would do 100 shot minimum, and I gaurantee you would be upping that to 125-150 after the first bottle.

Anyway, my suggestion is run around 34deg TOTAL timing if you're really gonna only spray a 75 shot. That means if your tune is 36 at wot, pull 3, if it's 38 at wot pull 5.

This should be very safe.

Second I would shoot for 11.5 AFR on the spray. You need much more than your N/A tune. Depending on what kit you have it will already be jetted pretty rich. You can go as rich as 11:1 and lean as 11.7:1 IMO without any problems...

On a mail order / dyno NA tune I like to pull 4 for 100 shot, 6 for 150 shot.

Currently pulling 6 on my 150 with the mallory and it feels great. Plugs look pretty close too for not having it on a dyno yet.

I've installed the Mallory, what do you need to know?

You basically get the MSD harness, and plug it in. The wire colors are different than MSD though. I can find the cross reference for you.

You need PN 8876 if you have a dual connector coil, and 8877 if you have the single...

The window switch is the Violet wire and actually completes and breaks the GROUND to your nitrous at the set RPM

[gregrob]

(MSD) Red = (MALLORY) Red
(MSD) Black = (MALLORY) Black
(MSD) White = (MALLORY) Green
(MSD)Orange = (MALLORY) Yellow

[gregrob]

Mallory HYFIRE

® VI 685 CD Ignition System

The Mallory HYFIRE


® VI 685 ignition system has a number of features that are set up by using

the top panel display and switches. Here is a list of the different features (or modes):
Mode 1 . This is the normal engine protection RPM limit. It is active if no other RPM limit is
selected. The range of this limiter is 1000 to 12800 in steps of 100 RPM.
Mode 2 . This is the auxiliary RPM limiter, and it is activated when 12 volts is applied to the
ORANGE wire coming out of the end panel. The range is the same as the Mode 1 RPM
limiter. This RPML will over-ride the Mode 1 RPML when it is active.
Mode 3 . This is a selectable high-speed timing retard. It is selected when the YELLOW
wire coming out of the end panel has 12 volts applied. The range is 1 to 15 degrees in .1
degree steps.
Mode 4 . Start retard value. This amount of retard is applied whenever the engine RPM is
below 500. The range is .1 to 10 degrees in .1 degree steps.
Modes 5 and 6 . These two control the built-in RPM activated .window. switch. Mode 5
sets the RPM where the switch activates, and mode 6 sets the RPM where the switch deactivates.
This is useful if, for example, you want to have your nitrous system only work
within a certain RPM range. The output wire for the RPM switch is the VIOLET wire
coming out of the end panel. It is connected to ground when the switch is active, and has
a maximum current rating of 10 amps. NOTE: The RPM range for this switch is 1000 to
12, 8000 and the


off RPM (mode 6) must be at least 100 RPM higher than the on RPM

(mode 5).
Mode 7 . Tach test. This feature allows you to check the accuracy of your tachometer and
any accessories connected to the tach output terminal. It also will activate the built-in
RPM switch in the Hyfire. To use the tach test feature, turn the ignition switch on without
starting the engine. Select mode 7. Turn the ignition switch off briefly, then back on again.
The HYFIRE


® will be generating a signal at the tach output terminal at the RPM displayed

on the top panel. You can use the UP and DOWN arrow keys to change the RPM to the
desired value.
To return to normal operation, select mode 1. Turn the ignition switch off. The next time the
ignition switch is turned on, the HYFIRE


® will be out of the tach test mode.

Mode 8 . Boost timing retard degrees per PSI of boost. If you have an optional MAP sensor
connected, the HYFIRE


® 685 will retard the timing as the boost pressure increases. Mode 8

tells the system how many degrees to retard the timing for each pound of boost. The MAP
sensor plugs into the 3 wire connector that comes out of the front panel. If you don.t have a
MAP sensor installed, this function has no effect.
Mode 9 . Cylinder number select. Set this to however many cylinders your engine has. The
range is 3 to 12,


even-fire ONLY!

Mode A . MAP sensor select. There are two MAP sensors available that are compatible
with the HYFIRE


® 685. One is a 2 Bar sensor (Accel P/N 74776), which is good for about

15 PSI of boost, and the other is a 3 Bar sensor (Accel P/N 74777), good for about 30 PSI
of boost. Use mode A to tell the HYFIRE


® 685 which sensor you are using. If you don.t

have a MAP sensor installed, this function has no effect.
To use the boost retard feature, you must use the Mallory P/N 29785 harness and
appropriate MAP sensor, as referenced above. Both the harness and the MAP sensors are
available separately.

[Joker Z28]

^thanks man I appreciate the advice.

I have the jetting for 75-125 and I want to start off with the 75 just to get use to it, plus I do not have anything else installed so I just want to have some fun with it for now. I plan on getting up to 125 till I get my forged 383 built then I can up the spray dramatically.
So is the stock timing suppose to be set at 37 degrees?

[gregrob]

Stock timing will run 36-37, yes. The tune commands 33 deg at WOT / high rpm and the PCM adds another 3-4deg

[jakesz28]

I would think that what ever afr the motor makes the most power at N/A is what the motor would want on the bottle.

There is no set afr to shoot for. But tune for best et or power and check the plugs.


I've always pulled more timing then I thought I needed to and added it back slowly.