Air fuel ratio Ljet Options

[914werke]

So thanks to all who chimed in.
Sometime you get too close to something & start 2nd guessing yourself.
I just had to step away & think less about it so I could come back ..with fresh eyes.
As I had commented I solved my only vacuum leak. Timing was an effect not a cause.
I had to solve that ...One of the couple thing different on this install was the TB, on which is mounted the TPS.
That (is a) switch on L-jet only affects idle & WOT ... Bingo.
I had to make a plate which to mount the TPS & it needed a bit of tweaking
Reinstalled & walla ..idle & adjustment
Got it timed
Now trying to tune it in, was wildly lean getting closer.
I need a beer~

[wonkipop]

good stuff.

(IMG:style_emoticons/default/beerchug.gif)

good looking throttle body.
whats that from?

[Van B]

Ah yeah that’ll do it. When you said TB was good, I just assumed it was OE.
I wish those were dual vac, I’d have one then.

@wonkipop he’s customized a gowesty throttle
https://gowesty.com/products/gowesty-throttle-valve-housing

[914werke]

UGH. Im back.
Well I thought I have this dicked by now but it seems to have me running in circles.
Once rich'end up I was able to road test & it ran pretty good cept it would hit a hard stumble when feeding partial throttle around 3K in any gear.
Looking at the LM-1 of course it was going lean, so I ve been going back & forth
Back to square one

[wonkipop]

i'm probably not much help - i have an entirely stock set up thats reasonably low miles and hasn't given me too much trouble - apart from cold start issues to do with AAV same as @Van B .

all i can offer is that at idle and at WOT the throttle valve switch lets the ECU know what the mixture should be (and at idle the screw adjustment on the AFM). in between its down to the AFM flapper and the signal it sends to the ECU.

that is assuming everything else is set up right. valve adjustment, timing etc.
and there is no reason to doubt you don't have all that set up right.

so i would probably try and get it right for mixture at mid range - and i guess the only way to do that is fiddle with the flapper and AFM.
someone like @Van B or @clayperrine would know exactly how to counsel advice on that. i've never had either the nerve or the need to go into the AFM. but it is all discussed in that article Van B linked to.

if the idle gives you a problem after that you take care of it with the screw adjustment on the flapper and the idle screw on the t/b. entirely separate matter.
thats how i have always understood the L jet.

good luck and hopefully the other guys chime in to assist.

[ClayPerrine]

I don't ever recommend changing the settings on the internals of the AFM. It is setup at the factory with a certain spring tension and requires a special Bosch tool and manual to reset it correctly. Changing it can change the fuel curve dramatically and cause crappy running.

If your AFM has been opened, I suggest you get one that has not been touched and try it. You may find the majority of your problems go away after that.

Clay

[914werke]

I don't ever recommend changing the settings on the internals of the AFM.

(IMG:style_emoticons/default/rolleyes.gif) Well, perhaps that is useful advice if you are working with a stock (1.8L) motor & the stock induction for which it was tuned in the 1970's (IMG:style_emoticons/default/sunglasses.gif)
not to mention the differences in gas formulation from then to now
or the likelihood of finding an unmolested AFM for a system that hasent been installed new in a car for over 30 years. (IMG:style_emoticons/default/happy11.gif)
But if you've spent a chunk of change on a motor and dont want to run the risk of frying that investment due to less than optimal air fuel ratio (IE overly LEAN) the only way I know to do that is with the use of a wide band 02 meter and judicious adjustments of those elements, fuel pressure, adjusted timing, ect.
With a system that is as sensitive to vacuum as L-Jet is, the addition of a non stock camshaft can add to the challenges. In my case Its ALL of that. (IMG:style_emoticons/default/headbang.gif)

[Geezer914]

Look up Internet Air Cooled Air Flow Meter. There is a complete article on how to adjust the AFM.

[Van B]

I don't ever recommend changing the settings on the internals of the AFM. It is setup at the factory with a certain spring tension and requires a special Bosch tool and manual to reset it correctly. Changing it can change the fuel curve dramatically and cause crappy running.

If your AFM has been opened, I suggest you get one that has not been touched and try it. You may find the majority of your problems go away after that.

Clay

Love ya Brother! Which is why I don’t mind telling you that every time you give this warning, I smile and immediately ignore it (IMG:style_emoticons/default/bootyshake.gif)

That said, your words are wise.

[ClayPerrine]

I don't ever recommend changing the settings on the internals of the AFM.

(IMG:style_emoticons/default/rolleyes.gif) Well, perhaps that is useful advice if you are working with a stock (1.8L) motor & the stock induction for which it was tuned in the 1970's (IMG:style_emoticons/default/sunglasses.gif)
not to mention the differences in gas formulation from then to now
or the likelihood of finding an unmolested AFM for a system that hasent been installed new in a car for over 30 years. (IMG:style_emoticons/default/happy11.gif)
But if you've spent a chunk of change on a motor and dont want to run the risk of frying that investment due to less than optimal air fuel ratio (IE overly LEAN) the only way I know to do that is with the use of a wide band 02 meter and judicious adjustments of those elements, fuel pressure, adjusted timing, ect.
With a system that is as sensitive to vacuum as L-Jet is, the addition of a non stock camshaft can add to the challenges. In my case Its ALL of that. (IMG:style_emoticons/default/headbang.gif)

Just an FYI.. I had factory training on L-Jet back in the 80s. I understand the system. And I found out the hard way that the engineers at Bosch who designed this know way more about it than I do.

The air flow meter is designed to make the mixture richer with more airflow. When you change the spring settings in it, it changes the mixture curve. Rather than f**k with the insides of it, you can do things like increase injector size, or increase the fuel pressure to compensate for more displacement. And the difference between the 1.8 and a 2056 is not enough to cause an overly lean condition.

I have been running L-Jet on various 914 engines for 36 years. Never have I had an "overly lean" condition cause damage to the engine. And I have multiple air flow meters that have never been opened.

You can change things on your car at a your pleasure. And you can deal with the drivability issues that come with the reduction in spring pressure. I have already been down that road, and I was hoping to save you the trip.

Good luck.

Clay

[914werke]

Just an FYI.. I had factory training on L-Jet back in the 80s. I understand the system. And I found out the hard way that the engineers at Bosch who designed this know way more about it than I do.

The air flow meter is designed to make the mixture richer with more airflow. When you change the spring settings in it, it changes the mixture curve. Rather than f**k with the insides of it, you can do things like increase injector size, or increase the fuel pressure to compensate for more displacement. And the difference between the 1.8 and a 2056 is not enough to cause an overly lean condition.

I have been running L-Jet on various 914 engines for 36 years. Never have I had an "overly lean" condition cause damage to the engine. And I have multiple air flow meters that have never been opened.

You can change things on your car at a your pleasure. And you can deal with the drivability issues that come with the reduction in spring pressure. I have already been down that road, and I was hoping to save you the trip.

Good luck.

Clay

Well great Clay, I appreciate any insight and advice you can provide. (IMG:style_emoticons/default/aktion035.gif) But admonishing me & suggesting I start from Zero isnt that helpful.
Clearly the reason for the post is to solve my EXISTING problems using a mixture of stock elements that may or may not have been messed with, & parts that would effectively mimic those installed on a 912E. The biggest departure from from stock is the cam installed, that while not over the top, apparently has enough overlap to impact the vacuum & simple start idle run.
As to overly lean, using the LM-1 it was easy to identity a VERY lean condition that was causing driveability (throttle load bucking) & could not be left as is.
So given that, where do you suggest I start, or questions youd ask?
Based on your stated "resume" this should be a slam dunk & benefit others who may find themselves down this path, but if you'd rather not troubleshoot in an open forum PM or call me
Thanks again (IMG:style_emoticons/default/beerchug.gif)

[wonkipop]

Just an FYI.. I had factory training on L-Jet back in the 80s. I understand the system. And I found out the hard way that the engineers at Bosch who designed this know way more about it than I do.

The air flow meter is designed to make the mixture richer with more airflow. When you change the spring settings in it, it changes the mixture curve. Rather than f**k with the insides of it, you can do things like increase injector size, or increase the fuel pressure to compensate for more displacement. And the difference between the 1.8 and a 2056 is not enough to cause an overly lean condition.

I have been running L-Jet on various 914 engines for 36 years. Never have I had an "overly lean" condition cause damage to the engine. And I have multiple air flow meters that have never been opened.

You can change things on your car at a your pleasure. And you can deal with the drivability issues that come with the reduction in spring pressure. I have already been down that road, and I was hoping to save you the trip.

Good luck.

Clay

Well great Clay, I appreciate any insight and advice you can provide. (IMG:style_emoticons/default/aktion035.gif) But admonishing me & suggesting I start from Zero isnt that helpful.
Clearly the reason for the post is to solve my EXISTING problems using a mixture of stock elements that may or may not have been messed with, & parts that would effectively mimic those installed on a 912E. The biggest departure from from stock is the cam installed, that while not over the top, apparently has enough overlap to impact the vacuum & simple start idle run.
As to overly lean, using the LM-1 it was easy to identity a VERY lean condition that was causing driveability (throttle load bucking) & could not be left as is.
So given that, where do you suggest I start, or questions youd ask?
Based on your stated "resume" this should be a slam dunk & benefit others who may find themselves down this path, but if you'd rather not troubleshoot in an open forum PM or call me
Thanks again (IMG:style_emoticons/default/beerchug.gif)

what clay says makes sense to me re airflow.
i myself would be very reluctant to mess with the AFM.
if i ever had to do anything with it there is a guy here in aus who rebuilds and tunes them and is trained to do it. we recently sent off an AFM for a 964 to have it rebuilt.
those kind of guys know exactly what they are doing setting one up.

re - the 912E did run slightly different injectors than the 914 1.8s.
they had slightly more flow. it is a 2 L engine so maybe porsche-vw had to do that.

you can google around and you will find some old shop talk forums that go into this.
i just did a quick google and turned one up.
had some of the blokes who are still active on thesamba discussing it.
L jet going on to bigger capacity 2L + engines with hotter cams.

what injectors do you have on it?

[ClayPerrine]

Just an FYI.. I had factory training on L-Jet back in the 80s. I understand the system. And I found out the hard way that the engineers at Bosch who designed this know way more about it than I do.

The air flow meter is designed to make the mixture richer with more airflow. When you change the spring settings in it, it changes the mixture curve. Rather than f**k with the insides of it, you can do things like increase injector size, or increase the fuel pressure to compensate for more displacement. And the difference between the 1.8 and a 2056 is not enough to cause an overly lean condition.

I have been running L-Jet on various 914 engines for 36 years. Never have I had an "overly lean" condition cause damage to the engine. And I have multiple air flow meters that have never been opened.

You can change things on your car at a your pleasure. And you can deal with the drivability issues that come with the reduction in spring pressure. I have already been down that road, and I was hoping to save you the trip.

Good luck.

Clay

Well great Clay, I appreciate any insight and advice you can provide. (IMG:style_emoticons/default/aktion035.gif) But admonishing me & suggesting I start from Zero isnt that helpful.
Clearly the reason for the post is to solve my EXISTING problems using a mixture of stock elements that may or may not have been messed with, & parts that would effectively mimic those installed on a 912E. The biggest departure from from stock is the cam installed, that while not over the top, apparently has enough overlap to impact the vacuum & simple start idle run.
As to overly lean, using the LM-1 it was easy to identity a VERY lean condition that was causing driveability (throttle load bucking) & could not be left as is.
So given that, where do you suggest I start, or questions youd ask?
Based on your stated "resume" this should be a slam dunk & benefit others who may find themselves down this path, but if you'd rather not troubleshoot in an open forum PM or call me
Thanks again (IMG:style_emoticons/default/beerchug.gif)

Rich,
I apologize if I came across as admonishing you. My suggestion is not to start from Zero, but to eliminate a variable in your troubleshooting. Using a known good AFM would eliminate that from the items you need to check.

Do you have someone close to you with a running L-Jet car you could borrow the AFM from for troubleshooting purposes?

Clay

[914werke]

Rich, I apologize if I came across as admonishing you. My suggestion is not to start from Zero, but to eliminate a variable in your troubleshooting. Using a known good AFM would eliminate that from the items you need to check. Do you have someone close to you with a running L-Jet car you could borrow the AFM from for troubleshooting purposes?
Clay

No worries. (IMG:style_emoticons/default/grouphug.gif) I have several but all have been opened.
As it happens our old friend Troy @Messix dropped by out the blue the other day & while he's been spending all of his free automotive time on his Jeep, he still has his 914 that may be pressed into this effort. Not sure when the last time he ran it, but assures me it does (IMG:style_emoticons/default/biggrin.gif)
But hold on ... it just so happens I have a complete 912E motor I got from Ralph Meaney's shop after he passed. & it has a AFM on it that looks like its never been touched.
More to come..

[ClayPerrine]

Rich, I apologize if I came across as admonishing you. My suggestion is not to start from Zero, but to eliminate a variable in your troubleshooting. Using a known good AFM would eliminate that from the items you need to check. Do you have someone close to you with a running L-Jet car you could borrow the AFM from for troubleshooting purposes?
Clay

No worries. (IMG:style_emoticons/default/grouphug.gif) I have several but all have been opened.
As it happens our old friend Troy @Messix dropped by out the blue the other day & while he's been spending all of his free automotive time on his Jeep, he still has his 914 that may be pressed into this effort. Not sure when the last time he ran it, but assures me it does (IMG:style_emoticons/default/biggrin.gif)
But hold on ... it just so happens I have a complete 912E motor I got from Ralph Meaney's shop after he passed. & it has a AFM on it that looks like its never been touched.
More to come..

There were two different air flow meters. 74s used a 6 pin meter, and 75 used a 7pin. I think the 912E used a 7 pin but I am not sure. So make sure the pin count is the same.

Clay

[914werke]

here's what Im working with:

[wonkipop]

thats a 75 1.8 AFM.

i believe it pairs with a 75 1.8 ECU.
porsche vw part # 474 906 301 bosch part # 0 280 000 111

interesting the way it has a blank space below the bosch part # where the VW-Audi part # is usually stamped.

[wonkipop]

part #s / details for the L Jet components on a 912E engine.





link to a 912E L jet EFI manual if you are interested.

https://www.912bbs.org/forum/downloads/912E...ical_Manual.pdf

clay is right. the 912 has a 7 pin plug like 75 1.8s.

[ClayPerrine]

thats a 75 1.8 AFM.

i believe it pairs with a 75 1.8 ECU.
porsche vw part # 474 906 301 bosch part # 0 280 000 111

interesting the way it has a blank space below the bosch part # where the VW-Audi part # is usually stamped.

This does bring up a good point. The ECU And the AFM are matched. Check your ECU and make sure it is for a 75 and not a 74.

Clay

[wonkipop]

@914werke

some one who might be able to help with this is @nihil44
he lives up in brisbane in australia and he dropped in to see me a couple of months ago when he visited melbourne. we stood around in the freezing cold and took a good look over my car and he was telling me all about his second 914 that was nearing completion.

i believe he used a 73 two litre engine (which would have been originally D-Jet) and he has installed L Jet on it. i don't know all the details but he has put it together out of bits and pieces he has been able to locate around the place. I think he has got it working.
he has just been battling away quietly with it along with his mechanic up there in brisbane.

i'm surprised he hasn't come on here but maybe he hasn't been visiting the site lately.
if he gets this notification he might come on with some suggestions.