EOC and restarting enrichment. Is there a workaround? - Fuel Economy, Hypermiling, EcoModding News and Forum

orange4boy · 03-25-2011, 05:24 PM

When restarting after an EOC most cars enrich the mixture for several seconds at least, correct? So if you have a kill switch and wire in a separate starter button does the ECU still detect the restart and enrich or does it fool the ECU?

I'm trying to optimize my P&G but I think the automatic enrichment may be hindering my results.

SentraSE-R · 03-25-2011, 05:32 PM

I don't believe that's the case. My 2002 Nissan dropped into (rich) open loop for 4 minutes after being EOCed. My 2006 Scion restarts in (lean) closed loop after EOC.

orange4boy · 03-25-2011, 05:58 PM

So it's vehicle dependent. Now I'm wondering how I can check that on my pre OBDII 1993 Previa van.

I see evidence of the enrichment on my tailpipe...

I know the idle goes up after restart.

Nice numbers, BTW.

orange4boy · 03-25-2011, 06:03 PM

If I hook up my multimeter to my oxy sensor would that show up?

Daox · 03-25-2011, 06:06 PM

Yeah that would probably work.

I know my 97 Paseo sends a signal to the ECU when the engine is being started. I can only assume its for fuel enrichment. However, it does go into closed loop pretty fast, but it does have a heated O2 sensor.

Glad to see you back on the board orange4boy.

roflwaffle · 03-25-2011, 06:56 PM

If it's in open loop I think you can put a voltage divider (pot plus resistor) on the AFM input to cut the amount of fuel injected, or just lean out the AFM via the pot/cog, but if you can't adjust the idle manually then it will bounce around like a pogo stick once it warms up if you go w/ the cog. To check if it's in open loop you can read the voltage across one of the diagnostic port pairs, but I can't remember which one atm, although I remember checking it and if the car is fully warmed up it switches to closed loop almost instantaneously.

roflwaffle · 03-25-2011, 07:31 PM

Here it is, on page 13. As long as it stays at 5V when you're driving it's in open loop. If it starts bouncing around it's in closed loop. I think an analog multi-meter would be the easiest to use in this situation.

orange4boy · 03-25-2011, 08:07 PM

Thanks roflwaffle. That's perfect. BTW, What's the waffle in roflwaffle?

Quote:

Originally Posted by Daox

I know my 97 Paseo sends a signal to the ECU when the engine is being started.

I wonder... if you start the engine with a switch direct to the starter solenoid does that still cause the signal to be sent?

Quote:

Glad to see you back on the board orange4boy.

Thanks for the welcome back. I managed to crawl out from under my rock.

roflwaffle · 03-26-2011, 04:53 AM

Just waffle cuz it rhymes. Here's some more stuff on toyota FI. This indicates that the start-up enrichment is based on the key being in the start/run/whatever position so you might be able to get by that through a separate switch for the starter solenoid. Try it and post up your results!

orange4boy · 03-26-2011, 05:48 PM

I thought it might be like ROFLYSST

ROFLYSST

Thanks for those links. I wish I had those 2 years ago. Very interesting that the EFI adjusts for voltage. So running alternatorless on 12V batteries is just fine. No need to boost the voltage.

What is the best to use for a kill switch? You don't want to kill the EFI or lose the memory so do you have to kill all the injectors at once?