What caused my random spike in MPG today? from ~45mpg to 52-55mpg at 45mph??

[ps2fixer]

Very good read, I like learning a bit more of the actual programming on the ECU and other engine related computers (programmer by hobby, IT Tech by career).

Anyway, on the offical site for scangauge I either can't get the values to work in X-Gauge, or the sensors are not listed.

BLM/LTFT - Has bank 5-8, but is called LF1 - LF4, I tried bank 5 and it never populates
KR - I see no where to monitor this on their page or default gauges
EGR duty cycle - Same as KR, with 230k miles, the EGR is probably partly blocked off.

If for some reason your EGR wasn't functioning, or was clogged, then you may be getting knock retard under certain driving conditions when the EGR becomes active.

Knock retard can also be caused by any number of mechanical rattles on the car, which can occur under certain driving conditions.

If the EGR is messing it, it could actually increase FE? I always thought it was the opposite, big time if I'm getting spark knock.

As for engine rattles, there are some and different RPMs. At low speed just starting off really easy, the engine sounds almost like a bad wheel bearing (last owner said it needed one, all are good).

At some point in time, I plan to hit the car with seafoam to clear out the carbon, and check the EGR ports, idle control valve, etc. I would just hate to loose FE by "fixing" the engine lol.

Back to more info on this "mode", even in warmer weather (60s-70s now) it is almost exactly the same setup except the car can move easier though the wind I guess. Instead of fighting about 6.6-6.8 MAP values to stay in the mode (under 7), I was going 45mph with as low as 5.8-6.2 most of the flat land travel. Instant mpg was reading between 60-65mpg, a few spikes to 70mpg but I was probably slowing down ever so slightly. At first I kepted hitting 50mph with my normal MAP readings, I was going WTF for a few miles lol. Trip average hit a new high as well, 49.9 and about 6 miles shorter (stopped at gas station), so it could have been at least 50.2 by the time I got home.This is from the same tank of gas I hit my last 2 high figures, 45.3 and 47 and my last aero mods. Can't wait for summer gas (if it isn't here yet).

With out this "mode" I rarely hit over 40mpg average on a trip.

[Olympiadis]

Originally Posted by ps2fixer

BLM/LTFT - Has bank 5-8, but is called LF1 - LF4, I tried bank 5 and it never populates
KR - I see no where to monitor this on their page or default gauges
EGR duty cycle - Same as KR, with 230k miles, the EGR is probably partly blocked off.

I would call the tech guy at Scangauge about getting the parameters right for reading those values on your car. He has been very helpful to me in the past.
I have seen EGR passages clog with only 50,xxx miles, so yeah that's a good possibility.

Originally Posted by ps2fixer

If the EGR is messing it, it could actually increase FE? I always thought it was the opposite, big time if I'm getting spark knock.

When dealing with tuning parameters like that there is never any hard rule where you can say x-change has x-effect, because it always depends on the specific tuning conditions you are starting from, and the particulars of how the engine is being loaded at the time you are examining.

It does often happen that MPG goes up when the EGR flow is blocked.

The MPG going up when spark knock triggers knock retard is not as common, but just as possible. It all depends on what the engine needs at that particular time. With certain loading conditions, less spark advance requires significantly less fuel in order to maintain stoich operation.

Originally Posted by ps2fixer

As for engine rattles, there are some and different RPMs. At low speed just starting off really easy, the engine sounds almost like a bad wheel bearing (last owner said it needed one, all are good).

Maybe one of the belt-driven accessories is going bad. It's usually a quick and easy test to remove the belt and start up the engine for a few seconds as a test.

Originally Posted by ps2fixer

At some point in time, I plan to hit the car with seafoam to clear out the carbon, and check the EGR ports, idle control valve, etc. I would just hate to loose FE by "fixing" the engine lol.

Seafoaming doesn't always work out for the best, especially on very high mileage engines. If you do it, be sure to change your engine oil not long after the cleaning is done.

EGR passages can usually be easily cleaned out with some Acetone, Mineral Spirits, or a combination of both, and some compressed air at around 100 PSI.

Originally Posted by ps2fixer

Back to more info on this "mode", even in warmer weather (60s-70s now) it is almost exactly the same setup except the car can move easier though the wind I guess. Instead of fighting about 6.6-6.8 MAP values to stay in the mode (under 7), I was going 45mph with as low as 5.8-6.2 most of the flat land travel. Instant mpg was reading between 60-65mpg, a few spikes to 70mpg but I was probably slowing down ever so slightly. At first I kepted hitting 50mph with my normal MAP readings, I was going WTF for a few miles lol. Trip average hit a new high as well, 49.9 and about 6 miles shorter (stopped at gas station), so it could have been at least 50.2 by the time I got home.This is from the same tank of gas I hit my last 2 high figures, 45.3 and 47 and my last aero mods. Can't wait for summer gas (if it isn't here yet).
With out this "mode" I rarely hit over 40mpg average on a trip.

Yeah our Focus gains around 10 MPG during warm weather, and I've traced most of this gain (ours) to warmer engine oil. I'm going to address this issue more before next winter comes. There are multiple factors involved with fuel usage vs outside temp though.

As for the precise adjustment of the throttle position it seems you could really use an increase in throttle resolution to make it easier to get your high mileage. The range of TPS is extremely narrow between the point of acceleration and deceleration. Take a look at your throttle cable interface with the throttle lever on your throttle-body and you may be able to do a small modification to make it easier to drive in this narrow range of operation. Increasing throttle resolution means that it requires more gas pedal movement to translate into the same movement at the throttle.

On our Focus there is a cam-shaped throttle cable guide on the throttle lever, and it was easy to increase resolution by changing the inner shape of the cam-groove with a piece of aluminum foil as a quick mod. Be careful not to bind the cable or it could break, - unlikely if you don't go WOT, and also be careful that the cable will not come out of the groove during operation.

http://i702.photobucket.com/albums/w...cablephoto.jpg

[ps2fixer]

I just put in seafoam in my gas tank, it is due for an oil change any time, so planning to hit it with seafoam via vacuum system too. Change oil, plugs, wires, and check cap/router.

For the noises, it is really weird, just barely moving like in a parking lot the engine makes some noises similar to a bad wheel bearing, any more gas, or less it don't do it. I suspect it is something with the ignition system not up to par. My dad is an ASE tech, so I could have him look into it some time when he has the time.

For the EGR system, I'm sure it will be carboned up, but if it kills my FE some, I would want to find out why, and be able to adjust the engine to be more efficient at cruise. Either way it needs to be cleaned. My Camry needs it too probably with 303k miles.

[ps2fixer]

Updates...


Yesterday I did the much needed oil change after a seafoam treatment and added a bottle of system 48 to the oil (oil treatment, reduces friction etc). Instantly I noticed my MPG is a bit higher when driving 55 (while performing the system 48 treatment run). Drove it to work and ran it 55 most of the way, averaged 47mpg which I could only touch if I went 45mph the whole distance before. The trip home I hit a new record for my self at 51.5 mpg with temps around 55. On that trip, the first 1/3 I could bearly hit the high MPG mode, so I had an average of around 42 at my turn north. From then on I was in the high MPG mode and was seeing instant MPG of 55-62 and was much easier to keep it in the high MPG mode than normal. I also added the 2nd half of my lower block for the trip home so that had a factor as well (last record was with it in at warmer temps).

The High MPG mode seems to be the same condictions, map sensor reading of under 7.0 and trans in 4th w\ lockup.

The last couple of times turning off the car when parking I noticed the idle is higher than before, probably from such a huge change the ECU needs to relearn the idle (which I am never doing except for coasting). I still don't know why the car gets better mpg when in this mode, either it is running lean, or maybe the EGR is being activated or stuck open.

Again, the only differences from "normal" mode and the higher mpg mode is the timing. To get into the mode I have to go 45mph, let off the gas to about map reading of 5, and re apply to about 6.0-6.6 to maintain speed. Timing reads around 23-25. In "Normal" mode, at map readings of 6.0-6.6 it is about 20% lower MPG at a given speed (which is normaly slowing down) and timing says 38 to 40

Just a side note on the sea foam treatment (my dad did it for me), he said he smoked out the area, and when he took it for a drive, it stopped smoking in about 4-5 miles.

With some aero mods I hope to hit the top 10 list for % over epa and highest mpg cars (60mpg = 130.8% over epa)