Programmable EFI tuning for economy?

[E4ODnut]

Anyone interested in sharing tips and ideas for tuning programmable EFI for economy?

[some_other_dave]

Lean it out until it blows up, then richen it up just a touch!



-soD

[E4ODnut]

Sounds logical. Might be a bit drastic though.

[tjts1]

Set it up to go into closed loop operation as soon as possible even after a cold start (i'm down to 15 sec using same afr as hot)
Stay in closed loop up to 90kpa,
Be very aggressive with over run fuel cut (i'm down to 1200rpm after 0.5 sec of throttle close)
Don't waste your time trying to lean out the mixture beyond about 15afr on an otherwise stock engine
Make the intake and exhaust as free flowing as possible
Reduce idle speed as low as possible when HOT in with closed loop WBO2 operation,
Use MegaLogViewer to record how the engine reacts to extreme load changes (on/off throttle, gear shifts etc). Try to reduce the amount of time that your AFR shoots off to extremes during these load changes.
Make sure you have a very stable voltage, RPM, CLT and MAT and TPS signals. Noise in any of these signals will cause unstable AFR and hence increased fuel consumptions along with other tuning problems. Again MLV is your friend here.

Sounds like you already have plenty of experience with MS1 so none of this is new to you. I have 2 Mercedes running MS1 and MS2.

[E4ODnut]

I'm not a great fan of closed loop control. First of all, it can be used as excuse for sloppy tuning. The other thing is that you are now depending on absolute accurate feed back from the wide band and I'm not convinced that this is realistic, at least not from my experience.

I use decel fuel cut a lot but I've modified the code and hardware so that I can do it manually. I've tried to lean out the mix during over run, but it seems to create more problems than it solves so I just use the fuel cut.

With the 4.9 I've found that I can run as lean as about 19:1 indicated before I get any lean surge but I keep it around 17:1 indicated up to about 80 KPA where I ramp up to about 12.5:1 at 100KPA. I've experimented with timing at these lean mixtures but haven't been able to really determine optimum. I'm not sure if there is a point of diminishing returns for lean mix. I just tune on the road, which is a bit limiting.

I am a great fan of MegaLogViewer. VE Analyze is nice, but I've found that even though it will get you into the ball park quickly I still end up studying the data logs and tweaking things manually. 1 or 2% in the VE table is sometimes all the tolerance you have.

I've built in a read out for fuel burn and found that economy is better for the same speed and load in a higher gear with higher manifold pressure, even if you end up with a richer mix. I think my read out is accurate to about 3% of actual, but even if it isn't the trends are what is most important.

Any idea what kind of accuracy the MPGuino can attain?

[tjts1]

I have the opposite opinion. I think closed loop is the most accurate tool for controlling fuel consumption. Your MPG read out needs to take into account the fact that your FPR is referenced to manifold pressure. Thats why you can find situations where the injectors are actually running shorter pulse widths at higher loads.

[E4ODnut]

What is FPR?

[tjts1]

Fuel Pressure Regulator uses a vacuum hose from the manifold to maintain a constant pressure differential between the manifold and fuel.

[dcb]

Originally Posted by E4ODnut

...
Any idea what kind of accuracy the MPGuino can attain?

On my saturn, with good refill technique, it was consistently within 1%, saturated injectors.

[E4ODnut]

DCB,
That's very good! Care to compare code?

TJ,
I'm confused. The regulator is, as you say, a mechanical device designed to keep the pressure drop across the injector nozzles constant with varying manifold pressure so the pulse widths don't have to compensate for this. I have an accurate fuel pressure transducer on the system in my boat, so I can log pressure and compare it with manifold pressure. My logs show the difference as being relatively constant right cross the range of manifold pressures. At no point do any of my pulse widths decrease with load, but that's a function of my fuel maps.