How to: reduce the rich condition of a cold start.

[saand]

C3H8, great post.
I have seen in other threads people doing the same thing, i think this mod should be put into the 65+ mods. If you end up doing some before and after efficiency tests please post them, might be able to get the mod into the list

For readers that dont have a nice new modern car like myself i have found that the idle speed control at warm up is achieved mechanically on my 91 mazda 626. Air is bypassed by the throttle control with an idle air control valve (IAC) which has a bimetal device which expands when it gets warm so closes off air bypass at temperature. I shall be trying to defeat the high idle at cold by putting something to block air flow through the air bypass which will then make the car rely on the electronicaly controlled air bypass which will hopefully stop the car from stalling in the cold.

[daring4]

In a related question can you apply resistors to the air intake temp sensor to decrease fuel use in normal driving? Sorta like lean burn for OBD1?

[mwebb]

you claim to be operating with 15% diesel ?
i tried 4oz of Shell Rotella diesel fuel additive to 10 gallons of fuel in a 10G Geo metro
lost about 10% FE that tank and

the additive did NOT combust in the engine so when it got to the exhaust
the 02 sensor
saw lots of combustibles so it thought " Rich condition - subtract fuel " not good , not a good idea at all
documented with scan data and scope waveforms

as you know
the 02 sensor does not see 02 , it sees combustibles in the exhaust stream .

15% , a gallon and a half in 10 gallons --- would be catastrophic in my car
so
kindly elaborate on this .......
===================================
then we get to No EGR ?
when you wish to improve FE , you have removed the EGR
that does not click either .

as it is well known that EGR improves FE by reducing relative engine size AND decreasing suction throttling loss .

so , to IMPROVE your FE and reduce NOX production
reconnect your EGR system ,
yesterday -
it is likely the ECM will respond to your tampering by retarding ignition timing
as it knows the EGR is NON functional , which will further reduce FE over just lacking the EGR .

so you are taking what is bad and your ECM is making it worse .

[mwebb]

Originally Posted by daring4

In a related question can you apply resistors to the air intake temp sensor to decrease fuel use in normal driving? Sorta like lean burn for OBD1?

NO
if you DECREASE voltage by DECREASING resistance the ECM will repond by
RETARDING ignition timing

which will REDUCE FE and INCREASE emissions.

these are negative temperature coefficient sensors
High resistance and high voltage = cold
low resistance and low voltage = hot

[mwebb]

culled from this waveform set

we have this , a zoomed in view


overlayed in there is a few 720 degrees running compression waveform so the eyes can see where the exhaust valve opens
so it can be seen that cylinder 2 is exhausting a very rich puff
this is a TBI engine .

the spark waveforms all show , LEAN Condition - and
LONG TERM FUEL TRIM is SUBTRACTING fuel

do not use diesel in your gas - it will NOT enhance anything .

[jamesqf]

Originally Posted by RobertSmalls

The Insight loves the heat, and I'd like to know why. You can get into lean burn much sooner in 90°F weather than 70°F, and I see an improvement in FE that air density alone can't explain.

Rather than trying to lie about conditions, have you tried the warm air intake mod? You just need a piece of flex tubing (I used some leftover SCAT duct from when we re-did the Cherokee's ducting) that goes from close to the cat to the air filter box.

If you have a ScanGauge, mine seems to like 110-130F best, but is not happy if it gets to 140. You probably won't see that, though. I only get that high when climbing long mountain grades on really hot days.

[RobertSmalls]

Yes, the WAI is in place and provides 30°F above ambient year-round once the cat is hot.

[ShadeTreeMech]

Originally Posted by daring4

I'm gonna guess you didnt mean "absolute zero"! Mine dont go negative, but it is late and had nothing better to do than respond...

Absolute Zero???!??! You mean −459.67°F??!! That's friggin COLD!

[C3H8]

what does running shell rotella diesel fuel additive, which is a diesel additive, not actual diesel fuel, have to do with me running actual diesel? not much. you are trying to compare a diesel fuel additive, to actual diesel fuel. thats an apples and oranges comparison. they are 2 different things. i dont know how a diesel fuel additive effects youre engine but i do know that i can get away with 15% diesel in my engine without pinging or any effect on fuel economy. i simply run a bit of diesel because its about 60 cents cheaper per gallon at the place i get it. it doesnt really help economy any, but it doesnt hurt either.

egr is an easy system to bypass without the computer knowing. i simply measured the resistance of the egr solenoid when in cruise with the egr valve open, (which was about 40 ohms btw) and duplicated that with a resistor soldered in place of said solenoid. this allowed me to remove the egr system and not have any check engine light or retarded ignition timing. and yes i did check ign timing before and after with a scan tool. running without egr resulted in increased ign timing because as you said, the throttle will be closed more. computer reads the throttle as being a few degrees extra closed (compared to egr on) and advances the timing a bit. (again compared to egr on)

i dont even believe there is ANY pumping losses with egr disabled and removed. yes it is true that egr increases the throttle opening. but did you stop to think why it does that? it's because the egr dilutes the incoming air with inert used up air that has no combustive value. the egr air simply takes up space in the intake manifold and combustion chamber that would normally have been filled with fresh clean air. in other words, you need X amount of air and X amount of fuel to maintain X amount of speed. with egr on or off you are still using the same amount of air and fuel to go the same speed. the only difference is that some of the air is diluted and the throttle is held open a bit more resulting in less timing. this doesnt magically reduce the combustion chamber volume. it simply renders some of the air that is mixed in, un combustable. and as such it lowers combustion chamber temps. lower cc temps? that doesn't sound good for FE to me. and it isnt. so yes with egr working the throttle is held open more, but you are getting less clean air. the 2 cancel each other out. in the end the same amount of clean air enters the engine, with egr on or off, it doesnt matter. only difference is, ignition timing is being retarded a bit with egr on from the throttle being held open.

i get better mileage with the egr removed and my resistor in place, then with the egr properly functioning. and i havent had a check engine light in a few thousand miles that was egr related. and my scan gauge does show increased ign timing during the same drive with i have egr disabled. and my mpg display shows increased mpg's.
i would hazard a guess that egr is nothing more then an emissions control device. it actually increases fuel consumption on my engine. not a good thing for an ecomodder.


keep in mind also that i don't have a little metro engine. maybe things work differently on small vs larger engines.

[ShadeTreeMech]

Originally Posted by mwebb

do not use diesel in your gas - it will NOT enhance anything .

I suppose it depends on the engine design. Some cars will do well with diesel added, especially the older, more rudimentary engines. I had a 96 spectrum with a 1.5 that could run diesel when mixed with a bit of gas---mind you I didn't log the fuel consumption with the tenacity which my esteemed collegue mwebb has so intricately done; it was simply a matter of being able to get cheap off-road diesel for free in a time of financial hardship.

I honestly don't think diesel is a good additive for the modern gas engine, but it helps a bit on the older ones by helping to burn off some of the gunk of years of hard work.