Driving around in my automobile, The 3.2 giving me about 32 mpg. Flipped HB Options

[worn]

I been driving my 914 this summer. Closing in on 5 Kim so far this year. When I go, I get the highest octane that I can find; 91 or 92 with no EtOH where I live, trending towards more ethanol as we get west. So, I have been old guy writing down the numbers and have consistently hit 31 -32 mpg. This decreases if I leave my gas cap off just before a drive with the RRC 2024 folks.
The interstates let you drive at around 80 mph, and that adds up to a light throttle 3,000 rpm with my gears. The car must be pretty good with airflow.

[technicalninja]

Here is some really well presented data you might find helpful.

https://www.kitplanes.com/adding-direct-air...tio-monitoring/


Id suspect you are correct in that most if not all are running rich. Almost every car I have retuned for people has been rich, many VARY rich.

Rich is just the easy answer, far easier to get things to run without to many noticeable issues just by dumping a bunch of fuel in. Without vacuum advance you can usually be anywhere pretty much from 14.7 to 9.5:1 on the rich side of stoich and have an engine that runs without bucking or popping. On the lean side of 14.7 you can get to maybe 15.5 but you are already loosing power pretty quickly, so yeah, quick tuning by ear or feel its almost always going rich.


When you get near 16:1 you need to add advance to get a complete burn in time, but throw in the necessary advance and it cruises along just fine at 16 and leaner.

I don't generally talk about lean tuning because so many people don't have a good understanding of what they are doing and are more likely to create problems and/or damage something if they attempt it without a solid understanding of EFI, because as I said, rich is easy. Easier to explain to someone they can just setup their entire tune in the 12.1-13.5 range and everything just works VS explaining where in their map they can go lean, how lean they need to be, and how to setup the transitions from lean to rich in their fuel and timing maps to have a smooth experience and no hot spots etc.

That second link (kit planes) is EXCELLENT!!!
It gets pretty deep quickly but was damn interesting to read.
I've always wondered about widebands and 100LL!
One of the vehicles I service is the fuel truck for the Pecan Plantation airfield.
I can have 100LL delivered!

NTK sensors are the way to go.
The Japanese kick ass again!

@JamesM thank you for the link.
With what you know don't you absolutely hate it when you cannot adjust fuel/timing at will, with the stroke of a few keys?
Having to resort to mechanical advance with vacuum operated advance/retard just seems "Retarded" in my book.
It's a wonder it worked as well as it did! (IMG:style_emoticons/default/beerchug.gif)

[JamesM]

With what you know don't you absolutely hate it when you cannot adjust fuel/timing at will, with the stroke of a few keys?
Having to resort to mechanical advance with vacuum operated advance/retard just seems "Retarded" in my book.
It's a wonder it worked as well as it did! (IMG:style_emoticons/default/beerchug.gif)

I would say I absolutely prefer to be able to adjust fuel and timing with the stroke of a few keys but don't mind the old way either (though not a huge fan of carbs). If anything working with fully programable EFI has been incredibly educational in understanding the relationship between fuel, air, and timing and helped greatly when diagnosing and tuning non-programable systems, after all 3 of my 914s are still running D-jet. My favorite part about modern programable EFI is that you can setup a tune in ways that just is not possible with mechanical distributors and older injection or carbs as well as the precision you can gain from using 3 dimensional maps vs analog curves. You are not going to get a d-jet car running smoothly and safely at 16+:1 at cruise while still hitting 12.5:1 under load and maintaining a perfect idle, just as a limitation of the technology.