GregBBRD

So, your NOX are the result of the engine being uber lean...just as the .01 CO readings indicate. You need to get the poor thing richer when the throttle is barely cracked...like on the 15 and 25 mph test. Without a "feedback loop" from an O2 sensor you basically have three methods of doing this...Sharktune it, cheat the temperature sender, or raise the fuel pressure until the CO gets to a reasonable place.

You might pull and plug the vacuum source to the fuel pressure regulator and go drive it...that will raise the fuel pressure dramatically, when the engine is pulling high vacuum. If that does it...cool. If too rich, it gives you a target of where you need to be with an adjustable fuel pressure regulator. If still too lean...you can always buy an adjustable regulator...but I'd be looking around the engine a bit more to find out what is really wrong.

dr bob

Greg--

the cars beenstored a while. I'm thinking that injectors are less than perfect due to old fuel/varnish etc. With the cat on there the tailpipe CO reading is not worth much, but the wideband reading from the front should be valid. No matter, lean is still the immedaite problem.

Good call on pulling the FPR vac line to temporarily add fuel. Thanks!

neilh

greg, Dr B -
great feedback, thanks - i'll try pulling the FPR vacuum line-- thats an easy test.
Drove the car today and got the water temp up to mid range and it was pulling much better - can get wheel spin of the line so there is some good power there - in paint shop now - will retest when i get it back.

GregBBRD

Bob:

Yes, have run into that before, as you know. The low HC made me think "systemic" issues, instead of individual cylinder issues. Guess all the injectors could be lame by approximately the same percentage.

Those off idle mixture numbers are really, really lean...you could easily be correct.

Bill51sdr

Not quite. The higher octane takes longer to ignite, thus raising pre-ignition pressure and heat. It can also result in an incomplete burn resulting in higher HC as well.

dr bob

Reinforcing Bill's point on fuel quality--- Remember that the 'rolling' tests are at very low load and low engine speed. Combustion dynamics are way different at those conditions.

Many moons ago I spent some time at Standard Oil of California, working with carmakers on getting the correct gear and adjustments on the car and a fuel blend that would get the cars to pass the "stricter" Cali tailpipe standards. We broke down all the test protocols to find ways to get the cars to pass them all with one fuel and the various mechanisms available for carburated fuel management. Those who remember driving Cali-spec US cars in the early 1970's know that the performance was very non-linear, as fuel, low mechanical comprression and partial cylinder filling (think "low-lift, short-duration cams), ignition centrifugal and compound-vacuum "maps", EGR operation and A.I.R. were tailored to pass the tests without serious regard for driveability.

"Modern" EFI and computerized ignition systems make childs' play out of what we used to have to do to get cars to pass those much looser standards.

GregBBRD

Bill:

Seems that if the higher octane takes longer to ignite, the piston would be farther through its cycle before the cylinder pressure builds, which would reduce pre-ignition pressure and thus the heat?

You need to explain this slower, for me to get it.

neilh

I'm loving this thread, I am at the point where i can try any suggestions gas wise - so keep the ideas coming, and i'll publish the results!

BC

I don't know the answer to this petrol question, but I would assume to figure it out we need to separate combustion temps and exhaust temps. Exhaust temps would be higher possibly with a slower ignition because it would still be burning longer into the exhaust stroke, making the exhaust and the cat see more heat.

The other side of this, technically speaking (I do not have facts right now) - is that it seems as though if you have a higher octane, and higher octane will burn Slightly slower, it will still ignite at the proper time, according to the spark on the spark plug. At 10 degrees timing, 87 octane and 109 octane will ignite at the same time. Each will burn at their own respective pace - and pre-ignition must be separated as we are talking about a properly running engine, but it may be running lean. It IS running lean. Which to me - means more air is entering the cylinders than the engine knows about - causing a lean burn. Its not doing it on purpose like a modern car.

The Euro Neil has has been sitting for a LONG time. It runs well, but it simply is running lean. A lean burn will increase certain traces in the test. I think unplugging the FPR and running a small amount of ethanol for the test will make it pass. THEN we can take stuff apart and figure out the issue.

BC

I temper my ethanol comment with that fact that its a GREAT fuel system cleaner. Sometimes too good. Use at one's own risk, but I am pretty sure it will work.

BC

Obviously, the car is running lean. The ethanol will make it run leaner, so you will still want to richen it up manually with unplugging the FPR or installing an adjustable one.

http://forums.audiworld.com/archive/...t-2130652.html

BC

Some good reading on smog test/octane:

http://forums.audiworld.com/archive/...t-2130652.html

neilh

I tried clamping off the fuel pressure regulator vacuum line as suggested - made no perceivable difference. So, I recalled the 'brain' has a link that is not normally connected that is used in areas of bad ( low octane) fuel to alter the map in some way - I'm assuming the link retards the timing for low octane fuel on the high CR engine to prevent pinging, I plugged them together on 89 gas. after a run the A/f at idle went down to 14 .1, from the previous rock solid 14.7 - at 1500 - 2500 there is not as good an improvement, and its still lean - 15 .5, down from the fail ratio of 16.5 - -

Am I making the right assumptions, any more suggestions -
Thanks
Neil

Rich9928p

Your EURO S engine requires premium fuel - no way should a Euro engine be run on regular grade. The EZF spark module has no knock detect (the "K" in EZK) capability, so lower octane fuel is dangerous. You should check that the vacuum line to the EZF is connected and is accurately provide the "load" information to the EZF module.

There is no spark timing adjustment on EZFs and EZK modules. The "low octane" plug will retard the spark timing (how much I don't know).

US spec 1980 - 1984 L-Jetronic-baed 928s were low compression engines and can safely be run on regular - and the spark timing can be easily adjusted.

neilh

There is vacuum at the EZF, but i have no table to go by to tell me what it should see at what rpm/load - I can hook the Innovate logger to it and record ( it has a vacuum monitoring port) but not sure how i will know if its good or not.