Experiments with Weber's and 30mpg.

[240260280z]

Yup.... got 30mpg (Imperial Gallons) cruising at ~ 3,000 to 3,500 rpm on a 240z.

Idle jets significantly impact cruise fuel efficiency.

I was experimenting and used two sets of idle jets:

1) 55F11

2) 55F9 with air drilled from original 1.0mm to 1.5mm (picked up some metric bits in Lisbon)

I installed bolts in place of the spill jets to rule out accelerator pump leaks clouding the results...btw it is not so bad driving w/o acc. circuit.

The 30mpg was attained with 18.5 a/f at idle and 14.7 to 15.5 at 3,000 rpm over flat road. The idle was rough and difficult to maintain at ~ 800rpm and 2 turns out on the mixture screws.

I drove ~ 300km and eventually developed some methods for quickly collecting data:

1. Capture Idle A/F

2. Capture flat road at 3,000 rpm in 4th

3. I found that the mains came in on a gentle hill at 3500 rpm. I found that the cruise A/F down a gentle hill at 3,500 rpm was similar to the flat road A/F @ 3000 rpm (mains not in)

I can now plot idle against cruise for various turns on the mixture screws to see where A/F and idle and cruise are optimized. It was interesting to note there were inversions where idle was richer than cruise then idle was leaner than cruise when plotted.

It was also interesting to plot flat road 3,000 rpm in 2nd, 3rd and 4th. For one lean 55F11 @ 1.75 turns out test I got:

3000 in 2nd: 16.5

3000 in 3rd: 15.5

3000 in 4th 14.5

btw mains are 120 fuel with 170air and F11 Etube....nice A/F of 12 to 13 from 3500 to 6500rpm.

Edited August 3, 2013 by Blue

[siteunseen]

Wow! Maybe I'll put these on my Camry.