"Tuning" FCD on a 1J

**Mr DOHC** · 25-05-2007, 04:32 PM

i have a HKS FCD on my 1J, what is the best setting to have it at, it spikes to 17 and settles to about 15, i have it set on 3, but ribfeast has his set on 8, both work, whats the difference, if i change it, will it lean out a bit more and go a bit better

**JZA70 R** · 26-05-2007, 01:55 PM

Yes. Make sure you check your AFR's either on a dyno or with a wideband after playing with the FCD to make sure its not running lean. AFAIK the more you increase the FCD the leaner it will run at full boost.

**Mr DOHC** · 26-05-2007, 05:17 PM

so if i change it from a 3 to an 8 it will run leaner

**JZA70 R** · 27-05-2007, 12:59 AM

Apparently yes. Lowering the voltage clamp. So at say 1 bar it its only putting in enough fuel for 10 psi. turn the FCD up more and it will only put fuel in for 8 psi.

Thats just an example.

**chris davey** · 27-05-2007, 09:10 PM

I don't know what settings relate to what voltage but the above is correct. Definitely do it on a dyno. But it is basically set and forget unless air temps change drastically.

Chuck it on a dyno so you can get a before and after anyway. Probably take about 5 minutes to "tune" it

**-==L=a=N=c=E==-** · 28-05-2007, 02:16 PM

find someone with a wideband, and an empty back road?

**Ribfeast** · 28-05-2007, 03:34 PM

Even one of those AFR gauges is better than nothing, make sure you have a few bars in the green on full boost.
Mine is on setting 8, clamps at approx 4.05V. Still enough fuel for 18psi boost, on stock injectors, Walbro 255lph fuel pump wired directly to battery (via relay), stock FPR. Fuel pressure unknown.