engine and drivetrain Adventures in 73 Tii throttle/afr tuning

[gliding_serpent2]

4 hours ago, cda951 said:

 

You should repeat the smoke test with the engine at operating temperature and the warmup regulator piston fully extended to 10MM.

 

If there is still a leak from the bottom, a mirror should be used to verify whether the leak is coming from the WUR itself or from the attached hoses. When I first bought my tii a few years ago, the bottom of the WUR was epoxied. Not sure if it was to seal in air or coolant, but neither leaked from it so I left it alone at first!

 

When I rebuilt my engine, I sent the KF pump to Gus at Pacific Fuel Injection. He went through the WUR at the same time as the pump rebuild, and said that he got it to function as well as it could, because mine was faulty and replacement thermostatic elements are no longer available. It now functions pretty well, but when the temp gauge is reading about 1/3, there is a lean spot in the WUR and the idle is slightly rough. But, cold start is easy and it runs great stone cold and at operating temp, so I don't worry about it too much.

 

Because your issue seems inconsistent, have you tried pumping the brakes numerous times while observing idle speed/mixture? Leaky brake boosters and/or hoses are fairly common on these old cars and are the cause of many an odd idle issue . . . . .

 

Chris

 

I will try this also.  My brake booster was leaking, and rebuilt 4 years ago.  Would not be surprised if this was again a problem.  Would a smoke machine help diagnose this?  I am not a pro and don't know where the systems link.... Oh i remember now.  I will check this today.

Edited June 22, 2016 by gliding_serpent2

[gliding_serpent2]

You guys are great.  My brake booster was rebuilt 4 years ago... For leaking.  Pumping the brakes at idle, i can lean my engine out 3-4 points.  

 

So the break booster likely goes.  No smoke from those hoses, so is it safe to assume the brake booster leak is internal?  

 

The warmup regulator is still under investigation.  

[cda951]

After re-reading the entire thread, it sounds like you have repaired some obvious issues and have it pretty well dialed in. You may still have some vacuum leaks and other issues to chase on your engine, but in terms of lean running during part throttle, what you have been seeing is . . . . . . completely normal based on my experience tuning these engines.

 

The most important thing to remember with any mechanical injection system of this era is that the system has no means of determining engine load. There is a fixed relationship between throttle position and engine RPM, and that is it. In other words, there is no input to determine the difference between cruising on the freeway at 3000 RPM with 25% throttle (light load), or if the car is being driven up a steep hill at the same RPM/throttle position. Even a carbureted engine has a crude means of determining load by using the venturi effect, with the addition of accelerator pumps for fuel enrichment during throttle tip-in. While it is very precise when everything is correct, the KF system on the 2002tii has neither of these capabilities. EFI systems are able to determine load by measuring airflow and/or engine vacuum in relation to engine speed/throttle position, engine and air intake temps and more.

 

Furthermore, the tii KF system was calibrated in the 1970s, with 1970s technology and 1970s gasoline formulations, using brand-new engines that were likely blueprinted to more exacting tolerances than the average M10 engine that came off the assembly line. Throttle linkages and ignition distributors were also brand new and perfect. Given the linear relationship between engine RPM and throttle position, BMW engineers had to settle for a compromise between exhaust emissions/fuel economy and protection from detonation, and did so without the benefit of fast-reacting modern A/F ratio sensors. Therefore, any KF system I have ever seen does run a bit lean during part throttle, which is how most cars are driven most of the time.  The whole notion of a stoichiometric 14.7:1 A/F ratio being perfect is that it is the best A/F ratio for the lowest average emission of harmful pollutants from the exhaust, which ensures optimal function of a 3-way catalytic converter. It is perfectly safe for a gasoline engine to run in the 15-16+ range during light cruising, and many factory EFI systems are tuned to run such ratios during these conditions. At higher engine RPM/throttle openings, the 2002tii's A/F mixture does richen up to stave off detonation during these conditions. If the system were calibrated to run in the high 12/low 13 A/F ratio at all times,fuel economy would suffer drastically, and the spark plugs would "load up."

 

Of course, detonation is most likely to occur during a sudden application of throttle at lower engine RPM, which is where fuel enrichment would come in handy. Because the KF system cannot provide this, detonation control is achieved by a mechanically advanced distributor with a carefully designed advance curve, and when everything is right, a 2002tii engine runs very well and gets great fuel economy without pinging.

 

When modern oxygenated gasoline, engine wear and/or higher compression ratios and ignition system variability are all factored in, the lean-running effect at part-throttle may be magnified. Any kind of performance camshaft will make things even worse. You could spend the rest of your life messing with idle mixture and throttle/pump correlation adjustments, but you are only moving the A/F discrepancy up and down the overall curve. To make the thing run more rich at lower RPM, more fuel volume is need, which means that the pump itself needs to be modified by changing the space cam and/or plungers, which is beyond the capabilities and budgets of most of us. Gus @ Pacific Fuel Injection has all of the original blueprints and specs for the various MFI pumps, but unless told otherwise, he rebuilds them to BMW's exacting original specifications.

 

As a compromise, you can make your lower-RPM A/F ratio safer by enriching the overall mixture via the main pump adjustment (or "verboten") screw. Of course, this will make the engine run a bit too rich at higher RPM, but this is not such a bad thing in the case of my tii, which has a decked block , skimmed head,  IE 90MM pistons, and a calculated 9.8:1 compression ratio and runs on CA 91-octane gas. During the recent Targa California road rally, we were charging around mountainous backroads at ~4500 feet elevation, and on a few occasions the ignition did momentarily break up near redline because the engine was running so rich (the 2002tii KF system lacks the barometric pressure adjustment of the Bosch MFI systems as used in Porsche 911s and Mercedes of the era). I currently have an MSD Blaster coil and Pertronix, so my band-aid solution will be a full MSD 6AL-2 ignition system, which is currently sitting on the shelf awaiting installation.

 

If I were you, I'd fix your obvious issues and get it dialed in as close as you can, and if it runs well and pulls hard without pinging, leave it be and enjoy it as is. I do hear that Wes Ingram offers a special linkage that manipulates the arm that the WUR acts upon to achieve better part-throttle enrichment. I may look into this for my car. The ultimate solution (besides going EFI) would be to mimic the 2002 Turbo's boost enrichment setup by implementing a similar device that responds to engine engine vacuum . . . . . but that's a project for another day, and for someone much smarter than I am!

 

Chris

Edited June 23, 2016 by cda951

[gliding_serpent2]

3 hours ago, cda951 said:

After re-reading the entire thread, it sounds like you have repaired some obvious issues and have it pretty well dialed in. You may still have some vacuum leaks and other issues to chase on your engine, but in terms of lean running during part throttle, The whole notion of a stoichiometric 14.7:1 A/F ratio being perfect is this is the best A/F ratio for the lowest average emission of harmful pollutants from the exhaust, which ensures optimal function of a 3-way catalytic converter. It is perfectly safe for a gasoline engine to run in the 15-16+ range during light cruising, and many factory EFI are tuned to run such ratios during these conditions, what you have been seeing is . . . . . . completely normal based on my experience tuning these engines.

 

Chris

 

Thank you for the thoughtful reply.  My issue is that things get leanest at 90%throttle... Then the are fine at wot.  Light throttle very rich to lean at near full throttle, back to the middle with WOT.  The spread currently is about 4 points on the afr gauge.  It used to be 12-16, now it is more 10-14.  I would prefer to adjust it again to 11-15.  It isninteresting if this kind of spread is normal.  I know most don't have wide band gauges.  But i seem to be running off of old expectations that you can get things more precise.  

 

Also, given that minimal pedal travel can richen my mixture out 2 or more points, and then lean it way out as you get close to wot, it just makes me think that the verticle butterfly shaft (name?) may be out of round and the pump lever and throttle butterfly are just not synched.  

 

And when warm, my car hates to idle... If you are not light on the gas, it will stall.  Does not seem overly rich... Which is off.  Cold idle is fine.  

 

Fuel pump is next, even if it is not part of the issue, it is loud... So time to go.  

 

I think the key is to just keep at it.  

 

Edited June 23, 2016 by gliding_serpent2

[gliding_serpent2]

Can someone comment on the brake booster leak concept.  I am having a hard time thinking it is playing a big role.  Shouldn't one expect pumping the brakes to lean out the mixture?  Aren't booster intake leaks often loud?  

[gliding_serpent2]

Some data from other posts:. I need to take note of checking timing again

 

"

.......all that, above, plus

(i'm blue in the face) 

-correct valve adjustment

--good even compression readings

---FUEL PRESSURE TEST READINGS

----igniton timing set at 2500 rpm

-----NEW gas in the tank

------clean , not gas deluted motor oil

everyone will contribute to your running problems"

 

"Before you take apart the regulator -- take the regulator off and check to see if the coolant passages are clear. Put the regulator in boiling water and see if it does rise to 10mm.

But, before you do that -- so some more checks:

1. When the engine is warm does the eccentric screw bottom out? If it does not, it would indicate there is continuing fuel enrichment. Loosen the nut over the cone on the regulator to make sure the screw bottoms out when hot. This takes the fuel enrichment out. Do you still have the issue?

2. Again, when engine is warm, clamp off air hose that connects the warmup regulator to the bottom of the throttle body. This takes the warm up circuit out of play. Any change?

I think the regulator can be taken apart, but start with the above."

 

i need to find that hose to the warmup regulator, and plug it off when things are warm.  That will tell me if the regulator is part of the issue.  

Edited June 23, 2016 by gliding_serpent2

[cda951]

OK, if your electric fuel pump is suddenly noisier than before, and your idle quality has also changed, you should certainly hunt that down before making any more adjustments!

 

But, I do stand by my long-winded statement above: even after sorting out all extraneous factors like mechanical issues, ignition, and fuel delivery issues, the KF system is not perfect, and you will probably never achieve a "perfect" A/F curve across the board.

 

As for your potential vacuum leak issues, it is very easy to eliminate the brake booster as a factor (though I don't believe it would cause much much besides an inconsistent idle during periods of frequent braking such as city driving). Simply unplug the brake booster hose (large hose that attaches to the intake manifold between the cylinder #3 and 4 intake runners) and plug off the port on the manifold. The brake booster doesn't do much for an 02 in the best of cases, so it is safe to go for a drive for testing purposes. You might have to push slightly harder on the brake pedal to stop, but it shouldn't be nearly as drastic as it would be on a modern car with unassisted brakes!

 

As for the WUR, it is certainly more difficult to disconnect and plug off the air hose. But, it is not too difficult to identify the air outlet hose from the WUR to the intake manifold; it is the larger diameter hose that attaches to the underside of the plenum; the two coolant hoses are much smaller in diameter. Your best bet is to remove the airbox and then attempt to disconnect the end of the air hose that attaches to the WUR and plug it off from that end.

 

Good luck.

 

Chris

 

[gliding_serpent2]

On May 8, 2016 at 8:08 AM, MatthewCervi said:

If you suspect something is wrong with your fuel pump--and from your description it sounds like there could be--then I wouldn't do any more adjustments on the fuel system or ignition until you get that resolved.  You'll be going around in circles if the fuel pressure and volume isn't consistent.

 

Well, fuel pump replaced, and fuel filer changed... And we still have the same noise issue with the pump.  If anything... The new pump might be louder.  

 

Here it is on before starting the engine.  Maybe this is normal?  Seems louder to me.  Sadly i have no real baseline to compare to.  I do have the expansion chamber.  

 

Thoughts?  Pull the hose off the top of the pump and measure fuel delivery rate?  

 

 

in the meantime, I reasdjusted my idle speed up slightly so the car would not stall out on idle when warm.  

[gliding_serpent2]

I should also add the the warmup regularor does open to the full position, and it does not respond to a spray of carb cleaner when sprayed in various locations.  I wonder how useful that technique is for smaller leaks.  

 

I will try the carb cleaner again in the am when the regulator is cold.  Just to verify that the technique actually makes a detectable change in idle.  

[gliding_serpent2]

Another question, what does an fuel pickup unit issue usually present as?

 

This is next in line given fuel pump issues?  (what I presume to be an issue, Or maybe a loud, occasionally sputtering fuel pump is normal??)

 

edit: page 140 of the restoration guide mentions that a loud pump is often due to a partly clogged fuel supply line to the pump.  So i need to check the mesh from the fuel pickup unit... And the hose to the pump.  

 

Also, In 30 seconds of running the pump only, when measuring from the disconnected fuel return line, i should also get 850-1000cc of fuel.  

Edited June 28, 2016 by gliding_serpent2

[kaptanoglu]

On 6/22/2016 at 9:53 PM, gliding_serpent2 said:

Some data from other posts:. I need to take note of checking timing again

".......all that, above, plus

(i'm blue in the face) 

-correct valve adjustment

--good even compression readings

---FUEL PRESSURE TEST READINGS

----igniton timing set at 2500 rpm

-----NEW gas in the tank

------clean , not gas deluted motor oil

everyone will contribute to your running problems"

 

 

Serpent -

 

I have been there, my friend:

A couple of notes based on what I have read on this thread:

• Timing matters a lot, and should be considered hand in hand when working on fuel mix issues (see attached if you want a kindergarten-level discussion on the topic).  Given the age of most of our distributors, I am much more comfortable setting my advance at a higher RPM so that I catch the full advance of the distributor.  Depending on your dizzy, the full advance (at, say, 3500 RPM) may be way out of whack vs. what the stock curve would show.  Alternatively, you can plug in some sexy electronics (search the forum for 123 and you will get more than you are willing to read)
• If you can hit close to 12.7 at WOT, and are a bit lean at part throttle (say 14 - 15) that is as good as it gets.  You can also alter the AFR at idle with the screw inside the tuna can (last step in the process)
• Ingram sells a setup for fuel enrichment at WOT, but it does not appear to be too precise.  I opted against it.
• Per your comment, correct valve adjustment is also pretty critical, and was transformative for Sputter when I finally got around to it.

Good luck

 

123ignition discussion MidAm.pdf

[gliding_serpent2]

Kapt, your thread is excellent.  

 

Your link to the hack mechanics thread is one that set me on this trail:  this sounds like my car:

 

"Played with this a bit more. Now have the AFM reading about 13.5 at WOT for a variety of conditions.

But now that I have it dialed in better at WOT, I can watch it at partial throttle conditions, and what I'm seeing is that, at steady throttle (say, 65 on the highway), it's reading between 13 and 14, but the moment I crack the throttle, even a little, like to keep up with traffic, it still swings lean, like 15 to 16, whereas if I punch it (WOT), it goes to about 13.5. Then it does a similar thing on backing off the throttle -- it swings rich, like 10.5 to 11, until you lift all the way off the throttle, where it swings very lean, like 16, which has been explained as the cylinders continuing to suck in air.

This is unchanged whether I have the small vacuum hose on the throttle body hooked up to the breather hose from the valve cover, or whether I have the small vacuum hose plugged.

In a prior post, Jimk in Denver wrote:

"With the use of an A/F gauge, a vacuum leak will appear under idle or low load conditons. If the A/F is ok on WOT and also low loads, the problem is not fuel. If ok on WOT but not ok under low load, continue looking for leaks. If not ok on WOT but ok under light load, fuel adjustments are needed. An A/F gauge will also show lean condition if there is misfiring due to electrical causes (i.e., O2 in the exhaust)."

Am I correct in assuming that, even though I have it dialed in better at WOT, this still smells like a vacuum leak?"

 

And this is what got me thinking I could do better: (curse you bill williams)

 

"I took the yellow car out and tried to keep one bad eye on the road and one bad eye on the AFR gauge.

At start up and at idle during warm-up, the meter read about 13.2 after a run, the idle reading dropped to about 13.0

I ran the car, on the throttle, cruising and off the throttle. While on the throttle and cruising, the gauge read, with some small variation, around 13.2 to 13.8. Off throttle and it would pop between 14s and low 15s

I had the car around 140 kph (87 - 90 mph) and it still was averaging around 13.2 while getting to that speed and cruising briefly at that speed.

And to be expected, there were the occasional blips of higher and lower reading but just blips"

 

 

 

Edited June 29, 2016 by gliding_serpent2

[gliding_serpent2]

My plan of attack

 

1. pretty sure the fuel pickup fro the tank +/- the line to the electric pump is gummed up... causing a loud fuel pump given a new pump did not solve the noise.  

2. Clean out the tank while at it. 

3. the test fuel flow on fuel return line with 30 seconds ignition (target 850-1000cc).  No wot or high rpm issues, so I think it will be ok. 

4. test afr's with vac line from warmup regulator clamped to be sue this is not an issue as far as leaks

5. Recheck timing at 2500rpm

6. Check valves

[cda951]

One more data point to add to this thread:

 

Last week I was looking at Mike Macartney's book for the first time in a while, and I glanced at the KF section. Anyone who owns a tii needs to own this book----the KF chapter answers about 90% of the questions that come up on this forum. Macartney lays out a very logical procedure for systematically testing the entire system.

 

https://www.amazon.com/BMW-02-Restoration-Guide-guides/dp/1855204517/ref=sr_1_1?ie=UTF8&qid=1467167329&sr=8-1&keywords=bmw+2002+restoration

 

Of course, almost 20 more years of age, modern fuels, and readily available wideband A/F sensor setups have muddied the waters somewhat, but the fundamentals are the same: make sure your engine is locked in mechanically ( good compression/leakdown/valves adjusted properly) and ignition-wise before going after the fuel system!!!

 

Chris

[gliding_serpent2]

agreed... cracked it again this evening and came up with a few gems noted above.