2056 Ljet, MPG? Options

[Geezer914]

Running a 2056 with Ljet, 9550 cam, 50mm TB, and 9:1 CR. Getting just over 15 mpg. Plugs look good, slight tan. Thoughts?

[technicalninja]

An aftermarket fuel pressure regulator does not have the vacuum connection to adjust the fuel pressure upwards at high vacuum conditions. That would account for the running lean at idle.

Use the stock pressure regulator, but bigger injectors.


Clay

Got this bass-ackward...
All of the vacuum referenced fuel P regulators I've messed with (an absolute shit-load, everything from Mercedes to GM) REDUCE pressure under vacuum.
So, the usual symptom is rich at idle with a fixed rate regulator.

Many aftermarket regulators are vacuum referenced. Some are what we call "rising rate" regulators which increase fuel pressure under boost. This was the first real "turbo" mod available to semi-accurately increase fuel delivery under boost. My mentor, Corky Bell engineered the first one 40+ years ago.
It was good for 7-10 psi, not more.

Digital programmable FI has negated the need for fancy pants regulators and is "the way" now but in decades past we didn't have cool HI-PO parts/injectors available and had to use stock type parts.

Geezer; Your choice of who to believe surprises me. Clay has multiple years of swap and try under his belt, specifically on 914s...
I don't even have that!
I'd believe Clay over almost anyone regarding 914 performance.

I'm betting 280Z injectors (which I have plenty of) will flow more than 914 injectors due to Clay's testing alone.

Specs and engineering data is important but actually trying this stuff is how you "prove" the data is correct.

Actual "I did this crap on the same day with the same WB" drives a stake through the heart of the question...

The AFR numbers are confusing to me and mine are from the water-cooled world.
I cannot believe changing the cooling medium would cause a significant change in AFR needs of the engines.

I see 10:1 as stupid rich, 3bar turbo-system rich.
11.0-11.5 Mild turbo system rich. below 2 bar
12.5:1 good power, safe. A bit "dirty". NA engines, Turbo below boost threshold.
14.7:1 Stoich "perfect for emissions" cruise only-no load.
16:1 getting lean-lean burn programming, great caution, knock sensors on KILL.
20:1 BANG GOES THE DYNAMITE! Death, melted parts, massive heat. Desolation...

If I actually saw 35!!!
That's so lean I wouldn't believe it but I would not run the engine again until I figured out what was going on with my wideband