Squeezing extra MPG out of P&G (EOC WHILE KEEPING THE CAR ON??)

[Occasionally6]

Some pertinent questions (I think):

Is the Sub direct or port injection?

If it is port, the fuel cut may be to avoid a spike in exhaust HCs as the airflow alters faster than the fuel empties from the inlet manifold.

What is happening on the other side i.e. how much additional fuel - if any - is being added as the throttle is opened? (Analogous to the accelerator pump in a carb.)

[kennybobby]

That really shows how the DFCO subroutine is triggered when the throttle position sensor hits the idle switch. The closed-loop idle circuit has huge control authority to regulate air and fuel to keep the motor running, and will use whatever fuel it needs to keep the speed within idle range.

By blipping or lifting the throttle off of the idle switch you have taken it out of closed-loop idle mode into POT mode.

On the old Bosch DME system the controller used countdown timers on interrupts to control the length of DFCO and also used them to create an 'accelerator pump' action to ramp up the fuel on WOT.

You could really see some gains if you could change the DFCO timer to a longer value--has anybody reversed that ECU yet?

[jedi_sol]

Originally Posted by bestclimb

Ohh idea for another test. Monitor engine RPM, spoof the throttle position sensor and see if the ecu reports injector cut off.

not trying to criticize as I am really hoping this effect is workable.

No worries on criticisms. I need everybody's input to help validate (or invalidate) my findings.

What do you mean by "monitor engine rpm, spoof throttle position sensor?" Can you be a little more specific? I want to make sure we're on the same page

[jedi_sol]

Originally Posted by oldtamiyaphile

Unfortunately, the technique only works when rolling. Although UFI has stop-start, the engine off means no A/C. It would have been awesome if I could sit stationary and keep the A/C on with a 70% fuel saving.

Yes I noticed the same thing, it only works while moving.

Originally Posted by oldtamiyaphile

This really needs to be verified via MPGuino, then automated via Arduino

I found my old MPGuino to test and bought some new wire splices. However, the Speed sensor for my car is up in the front wheel wells, which means taking off my tire....which means more labor . But i'll get around to testing very soon!

[jedi_sol]

Originally Posted by Occasionally6

Is the Sub direct or port injection?

If it is port, the fuel cut may be to avoid a spike in exhaust HCs as the airflow alters faster than the fuel empties from the inlet manifold.

What is happening on the other side i.e. how much additional fuel - if any - is being added as the throttle is opened? (Analogous to the accelerator pump in a carb.)

It's port injected. Only the new BRZ and 2015 WRX are direct injection

How should I test if any additional fuel is being used when the throttle is opened? (I have the TORQUE APP and MPGuino)

[jedi_sol]

Originally Posted by kennybobby

You could really see some gains if you could change the DFCO timer to a longer value--has anybody reversed that ECU yet?

It MIGHT be possible to tune the ecu/throttle position. User Evergreen tuned the throttle on his 2009 Impreza to give him more control over his throttle (auto tranny) use and gained 3mpg city driving

http://ecomodder.com/forum/showthrea...ore-27518.html

[bestclimb]

Originally Posted by jedi_sol

No worries on criticisms. I need everybody's input to help validate (or invalidate) my findings.

What do you mean by "monitor engine rpm, spoof throttle position sensor?" Can you be a little more specific? I want to make sure we're on the same page

Throttle position sends a voltage (typicaly 0-5v) to the ecu. voltage from the TPS monitored during throttle blips. Then matching voltage sent on TPS signal wire to the ECU. See if the ECU responds by closing injectors. If the effect is throttle position related (rather than RPM) the rpm should fluctuate with open/closeloop switch. (this is most likely a silly idea as I was mostly just thinking of ideas without filtering them much)

Re mpguino. If you are using it for injector testing purposes there is no need to get VSS signal.

[jedi_sol]

Hooked up my voltage meter to an injector. Setting a baseline

Idle: 14.25v

Accelerating: voltage drops (11v-13v)

DFCO in gear: 14.36v (steady)

14.36v is my assumption that injectors are not spitting fuel because we all agree that DFCO-in-gear shuts off the fuel injectors

If I do my neutral-throttle-blip while coasting: voltage fluctuates between 13.5v, 14.36v, and 14.25v. Pretty much all voltage values show (as measured above). Therefore, my assumption is that while im on the throttle (13.5v), I step off throttle to shift to neutral (14.36v injectors shut off), rpms drop to idle (14.25v). Then as I continue to throttle blip, voltages fluctuate between 13.5v and 14.25v…then every once in a while 14.36v will flash up.

I’m sure my voltage reader refresh rate is too slow. Therefore, I slowed down my throttle blip. I drove up to 40mph, shifted into neutral, started coasting, then I rose revs up to 2000rpm and held the throttle so that the volts read a steady 13.25v. Then I released the throttle, meter shows 14.36v, then down to 14.25v (idle).

I did it again…initiated the coast….held the throttle at 2000rpm…meter shows 13.25v steady…then I step off throttle, meter shows 14.36v, then down to 14.25v (idle)

Thoughts? Comments? Suggestions?

I’m getting ready to hook up the mpguino soon. Just gotta find a 12v source….or buy extra wire to reach the car batter 

[bestclimb]

14.36v flow off
13.50v higher fuel flow
14.25 low fuel flow

My assumption is that the injectors are supplied with ~14.4 or system voltage (could confirm by checking and comparing voltage at injector to battery voltage with engine running (so charged by alternator) and off)

You are seeing an average voltage (PWM injector signal)
so calling for lots of fuel injector is open (therefore drawing more current) so voltage drops.

calling no fuel injectors off so you see supply voltage.

So... from 13.5 to 14.35 then 14.25 you are seeing call for lots of fuel, then no fuel then a little fuel.

At least that's how I read it.

[jedi_sol]

Bad news

Trying to install the mpguino to finish up the experiment.

I am able to tap into the 12v wire of the injector because it leads back into the main harness, however, looking back at the mpguino wiki, it says to tap into the wire that has 0v.

The problem is that means I have to locate the actual fuel injector.since the Subaru is boxer engine, the injector is buried under the intake manifold, which means removing it.



Furthermore, all 4 injector grounds merge together and do converge at the main harness, but when I hook up the mpguino, I do not get any data at all.

Does the mpguino need to tap into a single injector wire?

For now, Im confident in saying that this theory is 65% confirmed (until I can get the mpguino properly installed). I'll continue tracking mpg on a tank by tank basis.

Bestclimb, you mentioned I don't need vss signal to track fuel usage on mpguino. Without vss, what screen should I use on mpguino?