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

[SentraSE-R]

OP, you have an interesting situation. I don't think higher octane fuel will help, since its only benefit is knock reduction. Still, it's worth the price of a tank to test if it helps.

Your timing should advance under lighter loads. I don't know why your Corolla behaves differently. The normal timing advance occurs under decreased load because of ECU mapping to avoid knocking. So, tossing higher octane into the picture may allow more operating time with less advanced timing. It's worth a try.

[Olympiadis]

Here's some visuals of a spark table, a PE spark adder table, and an EGR spark adder table. They are not for your vehicle, but may help with understanding the functionality of what I mentioned earlier.
Newer vehicles have a fairly complex adaptive spark logic with several other extra spark tables that include things like "low-octane spark", and "high octane spark".

Here, the bottom 2-Dimension table is the spark adder for EGR, or "Spark added vs %EGR". The top table is the VE compensation table.
http://i702.photobucket.com/albums/w...EGRscreen1.jpg


Next is another 3-dimensional main spark table (from a different vehicle) and a smaller 2-dimensional PE (Power Enrichment) spark adder table. It shows spark added when increased load is triggering Power-Enrichment mode of operation for added fuel delivery.

http://carphotos.cardomain.com/ride_...0082_large.jpg


There is some further explanation of EGR operation here in this thread on Ecomodder: http://ecomodder.com/forum/showthrea...e-7358-17.html

[ps2fixer]

Very interesting details, I'm pretty sure my car is more on the simple side of things since the mid 90s Toyota seem to have that factor, and the corolla is more of a base model type of a car. So I'm pretty sure when I feel/see the lockup, it is on fully or off fully.

The EGR related effects could be what is going on, the car does have 230k miles and similar models have EGR clogging issues at lower miles (97-2001 camry) which I have seen first hand in 2 of 3 cars, 3rd being only 126k miles (no issues), other two are around 180k (rise and lower of idle rpm, one throws the EGR code).

I'm not sure how soon I can investigate this further since I'm still on shift at work and I just had a large load of computers/printers come in (recycle them as a hobby/ side income). With an estimated 500 pound load (3 servers, 6 desktops, and a few printers/printer parts) with the trunk open I averaged 38mpg @ ~45mph .

I think I'm going to need to learn about the x-gauge feature a bit more for my car, the egr details would be interesting to see.

For the smart phone app thing, I don't own a smart phone, I use a $20/3 months prepaid since I never use it. I did look into running similar software on a laptop though.

For a few more IGN readings...

Idel when cold - 22
Idle when fully warmed up - 11-12

While under a larger load than normal it dropped in the 33-36 range on hills, and steady speed it kept around 37 more with 39s here and there.

I found I can stay in the higher mpg "mode" when my MAP sensor is at 7 or lower, to maintain 45mph it needs to run at around 6.6-6.9 which is hard to keep in that range, but once there I can basically freeze my foot there and be good to go till hills/stops. Normal 45mph the MAP sensor is 8-8.3, HPR goes to about 14hp when saving gas, 18 when it seems to waste it.

[SentraSE-R]

I think you're treading new ground for AT Corolla owners. Looking forward to seeing more of your results.

[ps2fixer]

Originally Posted by SentraSE-R

I think you're treading new ground for AT Corolla owners. Looking forward to seeing more of your results.

Thanks for the support!

I'm not doing any extreme hypermileing either, just coasting in drive, upper grill block, 55psi tires, 45mph instead of 55. Funny thing is, I'm not even sure if the car is in tip top running shape, the last owner did NOTHING on the car and he owned it for a year with burnt out lights (can't seed speed at night b4), nearly no brakes, headlights about falling out, HUGE alignment problem, worn out tires, and struts blown out.


One thing I should point out, this car has the more desirable engine/trans setup since the 1.6L gets worse mileage for an average (automatic based on EPA). Besides what I think is the better engine (max torq at 2800rpm vs 5600rpm), it has the 4 speed with lockup vs the 1.6L normaly having a 3 speed no lockup.



I have noticed while still warming up I can get about the same MPG figures as when the engine is fully warmed up going at a given speed. Since I travel 45mph, I get into lockup at about 140F (130 for overdrive) and MPG reads around 30 for a while. Once it is around 170F It runs close to 40MPG, and around 185-195ish I can get 45mpg. Once I hit around 198-202 (my normal temp) it advances the timing and kills my mpg...

One thing to note.... I have a 192F thermostat in it under the idea a warmer engine should have better MPG (thinner oil, warmer air, etc), and factory it came with a 180F one.

I'm thinking about changing plugs and wires, and have not changed the oil yet (looked fine when I bought the car ~1500 miles ago), since the money the car has saved me in gas costs will pay for it (1 month of driving).




Yesterday was the first time I had any kind of a negitive reaction from other drivers with my 45mph standard besides their normal stomp on it and pass reaction. I had two people at different times pass me on a section of road with a left turn lane in the middle. I had a large 250 pound printer in the trunk, I figured people would have been better "understanding" for the speed I traveled at since I had a load. Anyway, the only other time I have seen a similar reaction was close to the same stretch of road but infront of a school. Car infront of me was going ~40mph and the car behind me wasn't happy about it. They did their pass, and the car behind them followed them around... after they got past the van, the blue and red lights came on ^.^

Sorry for the long post, I guess I'm in story mode today or something.

[Ladogaboy]

Just the other day, I had a guy flashing headlights at me as I was coasting to a stop at a red light. Apparently, he wanted to make sure to get into the occupied left-turn lane. As it were, I was able to continue through (the light turned green while I was still rolling), and he had to come to a complete stop and wait because there were still three cars stopped ahead of him in the left-turn lane. I guess he wanted me to hurry up and slam on my brakes too.

[Olympiadis]

Have you played with the xgauge yet?
It would be interesting to see some more information that might help you figure out what's going on. You may be able to watch your Long-Term-Fuel-Trims. Our Focus displays that and it can be very useful.

[ps2fixer]

Ok added 4 xgauges. Two of them don't work which are Air to Fuel Mix (tried bank 1 - sensor 1, and Bank General). The two that do work are O11 and SF1.

I just noticed down further it has Long Trim Fuel Trim >,<, got to add that yet.

Anyway, O2 sensor reads mainly in the 70s-80s most of the time and dips to 30s-40s at times which should mean it is working right, but beyond that I don't know.

The SF1 reading was jumping around from -4 to 3. When I dropped my speed to around 30-35mph SF1 read a little lower averaged out than at higher speeds.

For my 45mph test, I couldn't see any large difference from IGN running at 39 (normal) and when i'm doing the trick to make it run 24. When I get a chance to test out LF1, I'll update this post.

[ps2fixer]

Oops, forgot to update, LF1 does not work for some reason .

Good news... today's trip home averaged 44mpg with wind working aginst me for 1/3rd the trip, and the rest it was helping and was able to stick in the 24 IGN 95% of the time not counting take offs. Did a couple small aero mods in hopes of hitting 24 IGN more often and easier.

[Olympiadis]

Watching O2 output is almost useless, and watching STFT is completely useless, so don't even bother with those.

The LTFT is something you definitely want to watch. Keep in mind you change to different load cells with different stored LTFT values as you drive.

Block Learn Multiplier and Integrator

BLM (block learn multiplier) is the older original term for LTFT - long term fuel trim.

Being that you have a drop in SA (spark advance) going on, you want to keep an eye on KR - knock-retard if at all possible.
You should also try to monitor your EGR duty cycle.

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.