Open Loop Fuel Economy Results

[oztracktuning]

Today on a country drive - on a course that i have over a few years compared my cars fuel economy i set a new best.

At an average of about 90kph (56mph) the car did 8.6L/100km over about a 20km trip on a relatively flat road. This is about 33 mpg. The car has 3.73 gears so was revving at about 2000rpm.

Edited 10 March - Found that the offset table made this value optimistic. Its now done the same course about 6 times in an average of about 9.3L/100km - its not flat though and i think on flat smooth tar it will do under 9L/100km and probably is capable of 8.6L/100km 33MPG.

My best on the exact same course at the same speed was 10.0L/100km (28mpg) and was done pre-ported heads and before i got EFIlive and was done in closed loop.

[ringram]

Hmm not an ideal comparison as you have raised your compression which increased efficiency as does the head porting..

Perhaps you can do the same and run closed loop and report back?

Plus you really have the same tune in there too.

[oztracktuning]

Thats the point the heads with raised comp have helped it alot and even more now with a better economy tune.

Its not the same tune - as i have totally redone the VE table and changed the timing. Plus i have a desired afr of 15.3 something i would have needed lean cruise for before. It wasnt setup.

I dont mind how i get it - as long as its safe on the engine - but it would be awesome to get 35mpg over a decent stretch of flat road at any speed. That is our terms is 8.1L/100km another 6%. The road surface was coarse large grain tar probably not the best to test fuel on. Ambient temp was about 30 deg C.

The wideband said 15.3 for about 3/4 of the run and 14.3 for the last 1/4. So can get that a little better.

[ChucksZ06]

Thanks for the post. I want to do the same thing to a couple of my ls1s. Did you 0 out the maf and tune the VE? Chuck.

[oztracktuning]

Yes - its mafless - i have tuned the VE and tweaked the timing in cruise cells. It has 36 deg at 2000 rpm in the cruise cells and 39 at 2400rpm.
It might take more ! AFR target is 15.3 but looking at the log again it shows that i can lean it out a bit more as it was probably at 15.0 afr a lot of the time.

[ChucksZ06]

Thank you. Just a thought for your application. I would be curious if less timing and a leaner mixture might further help in the light load area of the cells.

[oztracktuning]

May have to try a few other combinations. What do people thing is the best direction to go. I was thinking of trying a little leaner and more timing?
How can i tell if it is too much when tuning at light load? Will it still show KR?

[ringram]

If you are commanding 15.3 and you are getting 15.0 then your ve might not be right in that area. Check your BEN's there.

MBT (min best timing) is usually a way off from knock point. Timing is best found on a dyno.

If you can get some dyno time, perhaps you can use the bidirectional controls to adjust afr and timing to suit.

I read that best idle is the point of max vacuum and leanest afr. I run 15.4:1

[GMPX]

Today on a country drive - on a course that i have over a few years compared my cars fuel economy i set a new best.

At an average of about 90kph (56mph) the car did 8.6L/100km over about a 20km trip on a relatively flat road. This is about 33 mpg. The car has 3.73 gears so was revving at about 2000rpm.

My best on the exact same course at the same speed was 10.0L/100km (28mpg) and was done pre-ported heads and before i got EFIlive and was done in closed loop.

Wow!, mine never got that STOCK! with 3.07 gears.
Well done.

Cheers,
Ross

[TAQuickness]

With the V3 OS, I've managed to get my mpg up from and average of 13 mpg to 19 mpg. Timing tables are still pretty agressive so I know there's room for improvement still.