MPG and short trips

[Jim 5]

Originally Posted By: meep
Using a syn gear lube will make a difference, or at least it has in my cars. Same with T-case if you have it. Less difference in engine - in some cars I've noticed small (
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I notice this is significant in very cold temperatures. I'm talking about -20C and below. In pulling out of my parking spot at these temperatures, it feels like I am pulling a 2000lb trailer. Moving diff/transfer case lubes at these temperatures can really be felt until the car has a good amount of miles at full operating temp and the fluids in engine/diffs/transfer cases have warmed up through friction/internal combustion.

 

[Tornado Red]

Originally Posted By: Mamala Bay
Car sits over night the metal is cold. If you heat the metal takes time to cool off...a heated metal runs better period...I would think it gives better mpg over a cold metal.

This may be true, but in my car's case the engine computer retards timing until the engine reaches normal operating temp.

So the colder the outside air temp, the longer it takes before the engine starts operating efficiently. And the shorter the trip, the more time and distance is spent while the engine is operating inefficiently.

Ergo, if I only make trips of 5 miles, then the engine cools off, my fuel mileage will be noticeably less than if my trips are 25 miles or further.

 

[MarginCalled]

just put a resistor there in place of your coolant temperature sensor to make the ECU think the car is always warm. Bam, you get warm fuel economy on a cold car. Not as good for emissions but if it's your bottom line, who cares?

 

[OVERKILL]

Originally Posted By: MarginCalled
just put a resistor there in place of your coolant temperature sensor to make the ECU think the car is always warm. Bam, you get warm fuel economy on a cold car. Not as good for emissions but if it's your bottom line, who cares?


Yeah, and who cares about improper fuel trim and potentially epic detonation (on non-knock sensor equipped cars) either right?

EFI is a FEEDBACK SYSTEM. In order to get the correct OUTPUT, the INPUT values must be accurate. FOOLING the ECM by providing it with incorrect input values can have a devastating effect on what the output will be.

 

[ekpolk]

Overk1ll:

Easy solution to the feedback problem -- drive your cold car at WOT so it's in open loop mode. Then it's not a feedback system any more! No worries.

Seriously though, I do agree. The internet is full of descriptions of people messing with the input provided their ECUs via sensor modification, substitutions, and so forth. Many times people get away with it, but you're at risk of having the ECU inadvertently order the destruction of part or all of the engine. IMO, such experiments should be performed only with the greatest caution...

 

[OVERKILL]

I prefer "one should not tamper with something they do not fully understand the workings of"

 

[brianl703]

Originally Posted By: ekpolk

Easy solution to the feedback problem -- drive your cold car at WOT so it's in open loop mode. Then it's not a feedback system any more! No worries.

It still is a feedback system. It's still using the air/fuel tables that it built when you weren't driving it at WOT..it just doesn't update them at WOT.

 

[OVERKILL]

Yessir, and it uses the sensors attached to the system as well to determine what values it's using from that table.

 

[brianl703]

The only sensor it doesn't use at WOT is the oxygen sensor, and that's because it's output is meaningless at WOT.

 

[rationull]

Originally Posted By: MarginCalled
just put a resistor there in place of your coolant temperature sensor to make the ECU think the car is always warm. Bam, you get warm fuel economy on a cold car. Not as good for emissions but if it's your bottom line, who cares?


Don't coolant temp sensors usually output high resistance when cold, not when warm? I thought the inline resistor was a cheap "power mod", not an FE one.

I'm not advocating the idea at all. Just seems backwards to me.

 

[OVERKILL]

Originally Posted By: brianl703
The only sensor it doesn't use at WOT is the oxygen sensor, and that's because it's output is meaningless at WOT.


You are correct sir

 

[kaboom10]

Originally Posted By: ekpolk
Overk1ll:

Easy solution to the feedback problem -- drive your cold car at WOT so it's in open loop mode. Then it's not a feedback system any more! No worries.

Seriously though, I do agree. The internet is full of descriptions of people messing with the input provided their ECUs via sensor modification, substitutions, and so forth. Many times people get away with it, but you're at risk of having the ECU inadvertently order the destruction of part or all of the engine. IMO, such experiments should be performed only with the greatest caution...

What I've done is bought the software program which allows me to change ANY operating parameter in the ECU. I can chamge to open loop operation all the time if I want. I don't but a have modified closed loop program that it comes in @ 145*F. I have a F/A meter I monitor and datalog record with to analyze changes I've made. It's amazing the power that can be unlocked with some tuning.

 

[OVERKILL]

Which device do you have? SCT XCAL?

 

[kaboom10]

It's the SCT LiveWire so I could monitor in real time as I drive and the Pro Racer Package is the tuning software.

 

[OVERKILL]

Originally Posted By: kaboom10
It's the SCT LiveWire so I could monitor in real time as I drive and the Pro Racer Package is the tuning software.


Nice piece of equipment. Those of us with the older EEC-IV vehicles get either the PMS or the twEECer....