5 Liter Eater

Part one here: https://honda-tech.com/zerothread?id=166033

Setup is JRSC'ed GSR @ 9 PSI
DSM 450's @ 34/42 vac/static (stock would have been 42/52)
VAFC -40 hack, narrow @ 40% wide @ 80% throttle
No FMU

I wired in an on/off switch in between the O2 and the ECU. The A/F meter's signal wire is on the O2 side so it still reads the O2's output. So now I can flip a switch and force open loop operation! It works pretty darn well if I do say so myself. Doesn't even throw a CEL (which I don't understand).

So I did an ECU reset, flipped into open loop and at idle I had the AFC at -32 (@ 1000 RPM). The O2 showed way lean at this setting so I bumped it up one percent at a time, there was no change until -28% where it slowly went to the rich side. Going back down to -29% made the A/F slowly go back to the lean side. So between -28% and -29% is where the 450's should be at idle at the given fuel pressures.
For those if you who are still using FMU's and slightly larger injectors (310's, 270's, etc.) and wondering where your vacuum fuel pressure should be, I'd imaging you could do the same thing except changing the fuel pressure rather than AFC settings.
The rest of the narrow throttle I had at -36%. I raised the RPM's to 1500 according to VAFC, not tach, and the A/F showed lean again. It began to go into the rich range at -19% and back lean at -20% which seems really rich so I'm not sure of the validity. I had to alter the setting at 2000 RPM because since I had so drastically changed the 1500 point the 2000 @ -36 was interfereing with the 1500 at -20. I did the same thing for 2000, 2500, and 3000. I don't remember the exact numbers but they weren't a flat line. THey all varies between -20 and -25. Given this I had some major correcting to do on the high VTEC but since I didn't want to sit there and rev to 5000 in my garage with no load I just set the whole upper RPM range for narrow throttle to -25%. Figure I really don't go above 4000 in narrow throttle much anyway.

Wide throttle is still at -40 pretty much across the board and only a dyno will tell what the best settings will be. Keep in mind that I have to take a lot out because of the JR IAT relay tricking the ECU into thinking it's 0 degrees outside and fattening up the mixture wheneve I'm in boost. I am debating disabling this and see how it runs.

So to conclude, I'm not 100% sure that setting the A/F to stoich at different RPM's at -20"Hg is the most accurate but I'm going to try it for a while. I would say that it's a good way to figure out a good idle setting and I'm betting that's where a lot of the LTFT comes from.

Comments and questions are welcome.


[Modified by 5 Liter Eater, 11:02 AM 4/23/2002]

DSF

Just one concern. Aren't engine loads going to change in an actual driving/accelerating situation?

5 Liter Eater

Yes, but the FPR will add fuel 1:1 as manifold pressure (load) increases and the default fuel map should also account for the extra load.

5 Liter Eater

Well, on the way home last night I threw a code. I thought it was going to be a rich/lean code but it was a MAP code from boosting at part throttle where my trims aren't so low. I raised my pressure back to stock, or close to it (42/50 vac/static) and repeated the calibration process and got these #'s for the narrow throttle:

1000 -31
1500 -26
2000 -28
2500 -24
3000 -27
3500 -30
4000+ -34

Wide throttle is pretty much -40 across the board and I will tune that on Saturday on the dyno.

So my thinking is that if I know what the settings should be at full vac and after the dyno I know what they should be at full boost then I will set my narrow to like 10% throttle and my wide to 90% and let the VAFC interpolate throughout the vac/boost range.

I think a lot of guys could benefit from my toggle switch idea to force open loop!