Improving idle consumption / testing
 

I have been wanting to test out theories on how to improve the fuel efficiency of my motor at idle. Obviously with most aeromods you test while driving. My mods to try are listed here:

Idle reduced from 850 RPM down to 650 if it will still idle consistently
powersteering bypass belt
4 amp electric water pump instead of belt driven
no belt at all which means no PS, AC, or Alternator being driven.

The thing I want feedback on is the testing. This is my thought.

Let the car come up to full temperature with the low speed fan on (180 F)
Set the high speed fan to come on at (210), (it wont reach this ever)
Radio on, lights off
Use my ultragauge and measure gallons per hour.
Record the high reading, and low reading over the course of one minute with the ultragauge.

Do my modifications and try again.

My car fluctuates about .10 gallons per hour. I figure recording the high and low and then averaging should tell me whether it improved at all.

Any thoughts?

Reasoning behinds these mods is that they are already being used on my car or awaiting installation. Now i just want to see whether they actually helped at idle. a-b-a testing can happen later. If they help at idle, it is likely they will help even more driving.

Your testing plan sounds good to me. My only question is why you'd want to spend any time idling? Is your truck an automatic? You don't turn it off at red lights?

Regardless, it's commendable that you are trying to reduce your idling fuel consumption, and I hope you'll keep us informed about your testing results.

Just for my own education, have you measured what your car consumes at a cold idle without mods?

I am curious because from what I see on my car it really cuts total fuel consumption to let the car run a few minutes to warm up without a load. I know that the fuel burnt at idle is total waste, but I believe, from what my display shows me, that it is more than offset by the increase in efficiency when under load.

I don't have a aftermarket OBD2 display, just the factory display that only shows the instantaneous MPG to be zero. I would like to know what engine you have and what the consumption rate per hour is while you are idling cold.

Aim a camera at the ultragauge, and count the seconds it spends at whatever value, then time-average these values.

The mods you plan to do have previously been done by others, and they have reduced their fuel consumption by doing so.

Taking accessory loads away from the engine, improves FE.

I highly doubt you make up the fuel wasted idling your engine after starting it cold. Putting a load on it immediately will help it warm up faster, making the engine more fuel efficient sooner.

Obviously this is my opinion. I would change it based on data showing the contrary, however my commute out of my neighborhood happens at very light engine loads, and idling my diesel will not warm it appreciably before loading it anyway.

The reason I am trying to improve idle is that it isn't always feasible to stop the engine. Many of the lights by me are really short. The longer ones I turn the car off at and it has helped alot.

I am testing this on my car though which is a v8 1996 thunderbird with an automatic. I need to add it to my garage but first i have to fix the odometer in order to get good MPG readings.

Testing at idle is my first goal. Next is to do a-b-a testing but I just don't have the time and wllingness to sacrifice a tank of gas to do testing. Idle tests I can do in my driveway.

My xB consumes about .33 gph at cold idle without mods. That drops to less than half (.14 gph) when it's warmed up, and 1/3 (.11 gph) when it's fully warmed up.

You're far better off, IMHO, to use your engine to propel the car while it's warming up. If the engine's running, it should be doing useful work. By the time my engine coolant reaches 134 degrees F, I'm four miles down the road, and I'm up to a 50 mpg avg for that distance. You sure aren't going to match that with your car parked in the driveway warming up.

Well I finally managed to get started on this today. I took euromodders advice and took a one minute video for each mod. Hopefully tonight I can watch them and record all the numbers.

I still have to test the electric water pump as it was giving me problems most of the day and it was dark and cold by the time I finished. Hopefully tomorrow afternoon I can do some testing and then everyone will have some numbers to look at.

The one thing I did notice about the pump was that it keeps the engine around 8 degrees cooler. Later on I am going to change the low speed fan settings so that it comes on much later. I may actually get away with no fan and a complete grill block when it is 58 degrees out. Time will tell though.

Well here are the numbers.

Average Gallons per hour

.433 with the stock powersteering connected, belt driven water pump

.417 with P/S bypassed, belt driven water pump

.407 with P/S bypassed, electric water pump

the stock water pump already had an underdrive pulley so that might explain why the electric water pump didn't help as much as I thought.

I am going to do a quick test today with the low speed fan set to come on at 200 Degrees instead of 180 and see what happens.

All of the readings were taken at 180 degree water temp except the electric water pump which started at 180 degrees but had dropped to 174 by the end of the test.