wfbal

Does any one knows how the FM Link ECU IGNITION TRIM (IGN TRIM) feature works?

My car is generating some fairly high EGT numbers (up to 1750 deg F in the manifold) and I have a track event coming up where I can get some 94 octan fuel (my car is tuned for 91).

I want tu use this feature to advance the all ignition map when I will be using 94 (which should help keep EGT under control).

How should I do this?

Currently my IGN TRIM (Z21) value is set at the FM default value (20) which FM recommand for my set up (97 turbo, 550 injectors).

The tuning guide doesn't say how to change the z21 value to advance timing!

Help any one?

Walter
97 Miata
BEGI S5 Turbo kit with "disco potato"
6spd
Build engine
FM link ECU

Ken Hill

Using the keypad go to the IGN TRIM screen. Here you can use the Adjust Keys to add or subtract up to 5 degrees of timing.

The default value should be 0 not 20.

wfbal

Thanks Ken,

I got the 20 value (Z21)from the default maps FM provides on there web site!

So if I understand correctly, 0 would be no timing advance or retard, what would the impact (in term of timing advance or retard) for the 20 value I currently use?
I need to know that, because my timing MAP may be all wrong then!

What would be the correct Z21 value for an additional 2 degrees of timing advance?

Also, is there a general rule which would help determine how much more advance timing I could run with 3 more octane?

Ken Hill

My mistake, 20 is the correct default value for IGN Trim.

Timing values in the Link are stored in 1/4 degree increments. A value of 4 in the ignition table equals 1 degree, a value of 40 equals 10 degrees, a value of 82 equals 20.5 degrees, etc.

IGN Trim has a range of ±5 degrees. To the Link 5 degrees equals 20 quater degrees. However, the ECU does not calculate with negative numbers so 20 equals zero degrees of trim, 0 equals -5 degrees of trim. and 40 equals +5 degrees of trim. You do not need to retune you ECU, you set it up with the trim at zero. Sorry for the scare. If you use your Key Pad this is easy to see because it shows you the offset in the IGN Trim screen in whole degrees.

There is no general rule on how much timing to reduce the table when using fuels of different octane because fuel quality varies widely within a given octane rating.

wfbal

Great,

thanks.

Walter