Ok, so I finally got some time on my 75 L-Jet 1911cc motor (8.2CR, 66x96, 1.8 heads opened 2.0 valves) and I did the following;

1. Welded a bung plug right after the collector on my Bursch Exhaust (backdated to 70-74 SSI heat exchangers)
2. Installed a Wide Band AFR O2 Sensor and gage (Innovate LM-2)
3. Followed the calibration sequence
4. Drove the car.

What I was finding was the following, and it was pretty consistent;
Idle and closed throttle 20 to 1
Mid range 11-14 to 1
Full throttle (full enrichment) 7-8 to 1.

This was pretty much no matter what RPM.

So, what should I make of that?

What I would say is that the full throttle is too rich and the idle is too lean, but perhaps I am ignorant of what really should be happening. I have the Bosch book but this is contrary to what I expected from the gage.

Any help would be appreciated.

I am having the following problems with my L-Jet;
1. If I blip the throttle at idle, it has a hard time recovering as it is descending and often dies.
2. The car was running hot (oil temps) until I recently added an external oil cooler
3. I get pinging sometimes at full throttle.

Oh, and the timing is set to stock, on a Mallory unilite dist.
Click to view attachment

Don't mind the stupid water hoses for the vacuum hoses, or at least let me know where to get the right ones.

Bump

If it's rich and still pinging at full throttle, your timing is off. Start there IMO

http://bowlsby.net/914/Classic/zTN_Man08.pdf

7-8 is so incredibly rich that is disgusting and you are going to SMELL it. WOT ideally you should be around 12.5-12.8/13.0 ish depending on how your motor likes it.

That idle and closed throttle 20 is super lean.

You are going to blow something up, either wash a ring out and dilute your oil with the 7-8 or melt something coming off idle/decel hard.


This is beyond small adjustments, those values are pretty wrong. Your WOT ratio is 2x what it should be.

Play with your l-jet flapper, pull the top off and move the arm around while it idles to see if you can straighten out your AFR after you get your timing/idle set.

Definitely check timing and idle.

What do you plugs look like? If it is pinging, pull them and inspect them for detonation/misfire damage with a magnifying glass.

You will see bits of junk embedded in the insulator.

I would not be driving it until this is straightened out.

How gassy does your oil smell? If it smells very gassy, change it to avoid engine damage while you attempt to tune and fix this issue. It does not take much gas to thin out the oil enough to do damage and the last thing you want while misfiring/potentially detonating is gas tainted oil.

If you are sure fuel pressure, head temp sensor, timing, vacuum leaks, valve adjustment, etc... are all correct then making adjustment to the Air Flow Meter (flapper box) may help. It was not uncommon for people to loosen the spring tension on a AFM to correct for a lean condition or poor throttle response. Usually there were vacuum leaks or other tuning issues but the AFM got tweaked anyway. I have had limited success messing around the the AFM but I think that is what I would try if it were mine.
It seems like the spring tension is to light for the flap, it moves too far too fast making it too rich. Again make sure the rest of your engine is set up correctly before adjusting the AFM.
If you pop the cover off the AFM you can increase the spring tension on the flapper using a flat screw drive against the plastic teeth on the black spring retainer. Make sure you turn it so the tension increases and count the number of teeth you move, start off with 4 or 5 teeth. Turn the idle mixture screw in all the way and see it it is rich enough to idle. If it is too lean to idle you will need to adjust the position of the wiper arm. It is locked down with a Philips screw (usually has paint on it) and again there is a set of teeth you can use to move the arm. Only loosen the screw just enough that you can get the wiper to move and move it only slightly in the direction the flap moves and tighten the screw again.
You can place the cover on loosely while you test drive.
The trick it to find a balance between enough spring tension to lean it out some and mid and full load and move the wiper arm enough to richin it up at idle.
I make notes on the adjustment I make so after a road test I can make an educated guess on the next adjustment to make.

Good Luck
Jim

This is great info, and the funny thing is that the values seems almost impossible.

If the WOT truly is 7-8 to one, you are right ghuff, that is incredibly rich and would not run as well as it does.

I never smell gas, which is very surprising.

I'll pull the plugs and see what they look like, pull the flapper box cover and see what it looks like and do the normal L-jet checking, which I've done before.

Is it possible that my AFR gage is providing the wrong readings? I suppose anything is possible, but seems unlikely as it is all centererd around the right range.

Next trip up north I'll dive in farther and see what I find. I'll check the timing and do a compression test and go from there.

Thanks again!

One possible clue to this yet to be solved mystery is that the whole system appears to run relatively well, even at these ratios and that they are VERY tied to the TPS.

Where closed is 20 to 1
Middle is 12-14 to 1
and WOT (Full enrichement) is 8 to 1.

It is not dependant on RPM at all. Heck, if I WOT at 1k, it stays at 8 to 1 all the way through to redline. No stumbles, no nothing, just like FT.

This is not what I'd expect from 8 to 1 AFR.

I am starting to think it might be the Innovate system, so I'll look into that next.

To be honest, I would take it to a local dyno and get a dyno run or two/three with AFR ratios.

THis way you can see on paper what happens if it is missing/detonating, you should see a dyno plot that looks like Michael J Fox scribbled it out on a bad day.


Like this:




Vs this:






You can then have them plot your AFR against your dyno curve and you can correltate your AFR change points or changes on the dyno against the power it is making and what you heard/the operator felt as it was happening.



You will validate your innovative sensor, and get more data all at once. Should cost about 50$ ish?


Also waht do you mean tied to the TPS? The TPS on l-jet is just an idle on/off thing I thought?

The air flapper box controls fueling, it's like a giant variable resistor iirc.

Definitely give your oil a sniff. If it smells gassy, change it for sure.

You could be running that rich and have strong enough ignition to where it does not smell too bad......

Also misfires can lead to half burnt mixtures and rich signals......

Innovative stuff is usually spot on it uses a Bosch wideband sensor that is super reliable, and the hardware it uses was once open source for DIY wideband to it has been well tested.

Yes, thanks, the suggestion to do a dyno run is a great idea. Not only can I really control the curcumstance, but I can validate everything.

Also, i agree about the Innovate, and after doing more reading on it last night, it appears that it is not the problem as I performed the calibration correctly, and it reads 20.6 when the engine is off. It is hereby exonerated until further information is gleaned.

So, looks like I'll plan to eek out some dyno time next spring after the winter storage, as the rest of this year is booked, unless I can find a shop with a dyno in upstate NY and have my dad take it in.

As for the TPS, pin 17 is for idle, 12 is common and 9 is for WOT, so it appears that the 1.8 TPS has "switching" for both idle and WOT. I might be wrong, but that is what the Bosche book says.

Also to note, the AFC flapper box is only intended to control mixture up until about 3400 rpm, according to the Bosch book, and after that it goes by an analog map for the high RPM. This is somewhat contradictory to what I seem to find, but Robert Bosch NEVER makes mistakes, LOL.

Nice Power plots, BTW, mine probably peaks around 70hp on a chassis dyno!

I'll update with more as soon as I have it.

Unless I'm around.

Yeah, at least there is always an audible warning!

Check the 02 sensor with a volt meter.
four wire... two white wires are heaters.

You are looking for the wire that produces 0-1 volts...that is the range...so use a digital volt meter.

What 02 sensor do you have?
What is the history of the sensor and reading device? (new or used)

Second...how are you checking the rising rate fuel pressure?
Get a perminant gauge hooked up so you can see the fuel pressure at different driving conditions...
NOTE
Keep fuel out of the cabin...get a remote fuel pressure gauge so the inline portion is in the engine bay and it sends an electrical signal to the gauge in the cabin...

Rich

He has a wideband, so it is 0-5v sweep, and innovative allows you to calibrate the signal out to your ECU how you want.

Since his is standalone though that does not matter 1 bit.

He is probably using a serial port to a laptop to log.

I'll have to learn me some more l-jet analog to tear into my car. I'm deciding/weighign wasting my time with it or moving to megasquirt.

If 0-5 volts is the sweep then you need to use a digital meter to watch for the changes and make sure the o2 sensor is OK...

I get this with my newer volvos alot...they use "special" o2 sensors that are really sensitive to rich conditions and once they get dirty...forget it.

I just found this point which will make it a bit more of a challenge to diagnose the O2 sensor.

Another difference is that the WRAF (wide range or wide band) sensor's voltage output is converted by its internal circuitry into a variable current signal that can travel in one of two directions (positive or negative). The signal gradually increases in the positive direction when the air/fuel mixture becomes leaner. At the "stoichiometric" point when the air/fuel mixture is perfectly balanced (14.7 to 1), the current flow stops and there is no current flow in either direction. And when the air/fuel ratio becomes progressively richer, the current reverses course and flows in the negative direction.

When I was dealing with this in one of my Volvos I found that there are hundred of O2 sensors and they all have different electronic ranges...that is the key.
Get the part number off the O2 sensor and go google the manufacturer....I found the ranges for my specific O2 sensor and wiring diagram.


Rich

Yeah it's 0 to a literal 5v sweep. You need all the resolution to be able to accurately get judge the AFR.

The bosch 5 wire widebands get clogged up easily, and before that happens they start responding slow from being in too rich of an environment.

I change them yearly on my 01 GTi because it runs 11:1 under wide open throttle.

I edited my typo

His is a run of the mill bosch 5 wire generic. Same thing a 4th Gen VW uses or anythign with a motronic ECU.

Not trying to be a pedantic dick, I just have a bunch of experience with these units and sensors.


The bosch 5 wire sensors are mostly the same, the difference being the connector and wiring length which makes the price go from 50$ to sometimes 400$

Im sure he will figure it out, and I am sure you have alot of experience with the sensors...no doubt.

I ended up on the phone with the O2 engineer dude fromm Walker and he taught me alot about the voltage ranges of the sensors...they are all different.

Rich

Why dont you try hooking up the wideband on one of your other cars and drive it to see if the readings are close to the ones on your 914?

The problem is without feedback to an ECU, any misfires or anything will show up as weird AFR readings.

Unless the car is running 100% rock solid and just the AFR's are off, you will have oddities in your data.

That is why a wideband is nice on an ECU that can scale fuel/timing appropriate and uses it at WOT, you end up with a stable reading.

In instances like this, on older stuff you need the rest of the car 100% tuned to be able to get solid readings for to use.

Can't polish a turd. Can't tune a turd either. Garbage in, garbage out

Pretty much guaranteed to be an ok setup. There are a ton of these out there on all sorts of vehicles.

He would if the bloody O2 bung plug wasn't stuck in place! I'm about to ground the som-biatch off.

Hey, what about the Model A?

yeah, the model A...

I think we'd have better luck putting it on the law tractor!

All this advice is good and I will plan another trip up to the old 914 barn to see what I can do.

In general I recently set the timing on the optical mallory dist, so that should be pretty solid.

the fuel pressure is correct as well, and the car runs without any stumbling or misfires.

Thanks again,