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

Seems way low, John...unless you're driving that thing like a Ricer...I'm getting 27-28 high end with the D-Jet induction on Microsquirt,a dn I was doing mid-20s or better with the stock D-Jet before that.

Sure you're not leaking/losing fuel somewhere? Does it sit a lot and you lose vapors...?

@Saigon71 ?

You should be getting at least 25mpg. I suspect you are way rich.

Reading plugs only tells you what the plugs were doing at idle right before the engine turned off. You need to test with an O2 meter.

Zach

Any other issues that could cause this? Really bad alignment, brakes grabbing, bad bearings, etc....? And to Greg's point, what kind of driving are you doing?

I agree that an overly rich mixture is the most straightforward answer, but other things can contribute.

Ave 20ish; got 25 yesterday driving to Idyllwild

I'll hook up the O2 meter and see where I am at. I know 14.2 is optimum, but is 13.7 better for performance?

Can't trust the O2 in that way. Particularly with a type 4. It's more like "where does it tend to be and is it rich enough"

I got 8 mpg last tank in my Mustang because of bad behavior. Kind of proud my CFI 302 could actually use that fuel.

If you were having a ton of fun, 15 should be a good number for that motor. If you were trying to be a fuel miser, yeah, something is up.

i got a stock unmolested 1.8 L jet.
best i get at cruise on highway at a steady 65mph is 28mpg. (converting to your US measures of gallons). thats cruising. no gassing. no curvy hilly twisty roads.

i reckon its double that around town.
i wouldn't say my right foot is made of concrete but you know, i do press it down every now and then. but not ridiculous.

15mpg around town would be pretty close i believe to what i get in the horrible urban glue i am forced to negotiate.

This is only relevant in terms of energy needed to move the car. I was getting about 30 mpg last summer with my 3.2 six. Driving for thousands of miles at about 70-80 mph. These little cars are so great!

Back when I was doing deep learning of all the ways to mess with djet, I got 48 mpg in my 1.7
Tires, brakes, bearings all matter.

That said, you should be able to get 20-25 with carbs

Taking Clay's advice and reset the the large wheel in the AFM back to the original setting. Tank is full, so I'll see what happens. Thanks for the reply's

Those numbers are not good for an air cooled motor
Stoich is 14.7:1
And you will cook your motor quickly with that ratio

Do some research
At redline you want around 12.5:1 AFR

I routinely get 32 mpg in my 2.0/djet

2.0 with Elgin cam, dells, Mahle Euro P/C set, Bosch 050, and over the last four years I'm averaging 18.8 mpg on mostly country two-lane roads. Seldom into 4th gear, let alone 5th. Probably driving 5/10ths to 7/10ths.

If I'm just cruising around using 4th and 5th gears I get 24mpg or better.

Hope this helps.

With an AFR gauge hooked up, what AFR reading should I be shooting for cruising at 3000 rpm?

If it is telling you the truth, 14 would be fine. A modern car would even be around stoich at that point. In a type 4 I would feel safe anywhere between 13 and 14. I would verify with a plug check though.

AFM set back to normal, hooked up the AFR meter and took it out for a spin. At 3k in 5th gear the AFR was 12.3! Came back to the garage and lowered the fuel pressure from 34lbs. to 30lbs. Take it out again and now the AFR reads between 13.7 and 13.8. at 3k in 5th gear. So I think I'm good to go, just have to check the MPG. Thoughts???

i am at 13.5 , WOT 12.7, (d-jet, 2.1)

perfect

Are you using 1.8 injectors or 2.0?

2.0 will likely flow more per squirt which would cause richness.

1.8 injectors. AFR at idle is around 15.9, normal?

Late to the party.

15 does seem low.

My 2056 D-Jet with FAT 440MP cam runs 22-29 MPG depending on driving conditions...but this is D-jet.

Tweaking the fuel pressure and got the AFR to read 35 cruising at 3k. The car seemed to come alive with the AFR at 35. At idle the AFR reads 15.9. Is that normal?
My mistake, AFR is at 13.5-13.6, not 35. I don't know what I was thinking.

L-Jet injectors are not compatible with D-Jet injectors. The are electrically different.

The stock L-Jet injectors were right at the limit on a stock 1.8L engine. Use the injectors from a 912E (same injectors were used on a 1980 Nissan 280ZX)

Standard Motor Products Fuel Injector
Part Number: 6639-05181321
Brand: Standard Motor Products


They flow more than the stock 1.8L injectors, and will correct for the cam and additional displacement of the modified engine.

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

@ClayPerrine

how do those 912E injectors go on a standard 1.8?
out of interest.

They are a 100% bolt on solution. The 912E used L-Jet injection, and the injectors are are, other than the flow rate, identical to the 914 1.8L injectors. I have a set on the engine from Betty's car.

I called Standard Motor Products and they said the flow rate for the FJ6 and FJ707 injectors is the same.

thanks mate.
because you know why i asked.

Riddle me this Batman....

Why would they have two part numbers and two separate stock items for what is essentially the same part?

Could it be a call center person who is just trying to get you off the phone?

Just a thought.

My experience shows on the same car with the same system the 912E injectors run richer than the stock 914 1.8L injectors. The testing was done with an LM-1 on the same day with the same car.

They said the tips and the cone are different, but the flow rate is the same.

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

Thank you for that vote of confidence, but I am not perfect. I have been known to be wrong in the past.

I have all the respect for Clay. Just quoting the tech guy from SMP. I have an adjustable fuel pressure regulator and was able to adjust the fp to 31 1/2 lbs. which gave me an AFR of 13.5 - 13.6. I am using SMP F6 injectors. Idle is lean with an AFR of 15.9, but I am not at idle too often!

If anyone has flow rates for the 912 injectors vs 914 injectors please post them.

@Geezer914

Click to view attachment

Just checked the Z injectors. 185cc for non-turbo 265 for turbo.

Clay, it looks like you might be wrong... (all of us are wrong at some point)

The whole "swapped in one day and saw a difference in the WB" states they must have been different but if Woki's list is correct (and it looks like it is) there is no way ANYONE could see the difference between a 187 and a 185...

Maybe your 914 injectors were restricted? Be way weird to have all 4 with the same restriction level.

Geezer, back in the Z car world we used a air bypass in the AFM to set idle fuel enrichment. My 75 914 AFM has this adjustment in it as well.

16 at idle is too lean for my tastes. Normally idle was .5-1.0 richer than cruise which helped smooth idle out. After you get base AFR set with the adjustable pressure regulator (it sounds like you are close) mess with the air bypass at the nose of the AFM to richen it up a bit.

I'd want my average cruise AFR to be 13.5-14.5 and my idle to be .5 richer.

Does it idle high and hunt now?
I would expect it too.

Here's a list of a bunch of injectors. some information is missing (like the 914 cc data) but it is a fairly complete list.
http://www.atlanticz.ca/zclub/techtips/inj...s/injectors.pdf

I will be the first to admit I could be wrong on this.

And maybe the injectors I got were for the 280ZX turbo.

All I have is the evidence of what I see with the LM1.

That being said, there are lots of L-Jet compatible injectors out there. It was used on millions of German and Japanese cars for years. Nippondenso had a license to build it so it was installed on 80s models Nissan and Toyota vehicles.

Do your research, and you should find an injector that will bolt on to a L-Jet 914 and flow more fuel.

Don't trust that afr too much. Keep an eye on the plugs as well.

It is all taken apart at present, but I found the motor gave more power as I approached stoichiometry, but wanted to burn to an inedible crisp. Hate to waste fuel, but there are limits. I got 25 to 30 mpg with a 2056, but that varied with my willingness to gamble.

Email from Standard Motor Products Click to view attachment

super accurate tuning, at least on these cars, was to use Tangerine Racings exhaust temp sensor pieces....one for each cylinder.
It tell you how each cylinder is doing.

For an O2...its one reading across all four cylinders...not accurate.

Curious on the post above.
What are the same flow rates lbs/hr for the OEM injectors from Bosch?