engine and drivetrain Dialing in a '72 tii

[mvliotta]

I purchased a '72 tii a few months back (2761485) and have been working on her (Liesl) ever since. On the first drive home she had a severe bucking issue after warmed up and was generally low on power.

 

After much reading on this forum, and with lots of help from contributors here, I have resolved 90% of the issues by:

 

-replacing plugs, wires (1 was bad), cap and rotor (and converting points to HotSpark) and coil (proven to be weak)

-replacing main fuel filter (all others are clean)

-increasing fuel pressure from 14 to 28 psi via pressure regulator adjustment

 

Then timed her with advance light (decent enough advance curve).

 

All of the above eliminated about 50% of the bucking.

 

I then sealed up significant air leaks associated with the plastic intake runners, adjusted the throttle body cam and screws according to the KFish manual (was off), and adjusted the accelerator pedal linkage (was only getting 70% of WOT when pedal on the floor).

 

No more bucking, pulls nicely, FUN to drive. I'm very very happy with the results so far... BUT one remaining issue...

 

At WOT when driving in any gear, the RPM zings up for a bit (starting at about 2700-3000) before the power kicks in. Thinking it could be one of the following...

 

- injectors fouled a bit? (have not checked these yet)

- need new linkages? (a little bit of slop, but don't know if it's too much)

- throttle body still misaligned? (Don't have a CO meter or AFR)

 

Thoughts on where I should focus??

 

Thanks again 

Vince (Dummy who did not know how to change a spark plug a few months ago)

 

 

 

 

 

 

 

 

 

 

 

[OriginalOwner]

as a longtime  '74tii driver, and having been counseled many times on this Forum:  tii power "zing" is different from a carburetor.  Here's some wise wisdom from those who understand the concept much more than I do ........

  http://www.bmw2002faq.com/topic/163227-my-recent-learning-experience-on-mods-versus-value/

 

Cheers,

 

Carl

Edited November 12, 2015 by OriginalOwner

[ray_]

Do you mean the rpms increase while the car does not accelerate?

 

If so, clutch slippage?

[markmac]

- injectors fouled a bit? (have not checked these yet)

- need new linkages? (a little bit of slop, but don't know if it's too much)

- throttle body still misaligned? (Don't have a CO meter or AFR)

 

All of the above (and maybe more I am afraid to say).  Tii Kugelfischer systems are absolutely unforgiving.  A "little" slop won't work out on these.  On the injectors, it is really hard to say just on how they look.  You need to send them to someone and have them checked (Gus at PFI, but who knows how backlogged he is).  The TB thing sounds sketchy (misaligned?) not good.  Very few have actually driven a tii that is completely dialed in ( ignition, fuel system, etc., etc.,), this being a little off, that being a little off is cumulative and up with a car that performs more like a standard 02.  Healthy Tii's that are set up and dialed in go like stink (lots of fun).  Seems like you have a few things to sort out.  Good luck.

 

www.alpinabmw2002.com

 

Edited November 12, 2015 by markmac

[mvliotta]

Thanks for the quick responses thus far! 

 

Clarifying the zing.. yes, RPMs go up without the corresponding power only when I punch the gas pedal. If i keep it at 60-70% full throttle, it pulls strong and steady. 

 

Oh and BTW, when I press the pedal down steadily an quickly in neutral, it feels like the RPMs don't go up as linearly as I would expect around the same RPM band where the power loss seems to be. Don't know if this is a coincidence and hard to be objective.

[JsnPpp]

Sounds like you are having fun!  That is the main thing.

 

I agree that it can take a bit of time to get these cars (Tii or not) running well, but it's worth it.

 

My vote on this is linkages.  Get rid of the slop (just buy new ball/cups) and then you have a place to start from.

 

~Jason

[thehackmechanic]

I agree with Ray that the RPMs "zinging up" without the car correspondingly pulling forward sounds like the clutch is slipping.

 

Regarding the injectors, you can pull them out and send them in for cleaning and testing. A search on this forum will reveal the shops who do this. I've been using Diesel's Injection Service in Bow NH. They're very reasonable, about $20 to clean and test each injector, sometimes less. Be aware that they don't rebuild them, just clean and test, so if one or more of the injectors tests out as leaky, you've got a problem.

 

You can test easily enough for slop in the linkage by, from under the hood, moving the linkage as it comes up from the gas pedal and visually observing where there's play. Typically, on an unsorted car, there's play EVERYWHERE in the linkage. It's not unusual to have to place the three linkage rods, the intermediate throttle linkage shaft, and the ball linkages on the pivoting shaft mounted to the block in order to get most of it out.

 

Regarding the throttle body being "misaligned," it sounds like you've read through the procedure in the KFish pump manual to adjust the length of the linkage rods, "pin the pump," and rotate the cam in the tuna can to the edge of or over over the little hole. Many tii owners have experienced mid-RPM bucking and had it go away by rotating the cam further over the hole to richen up the mixture. No sense in doing this until after the linkage is tightened up.

 

Another thing you can do is install an air/fuel gauge so you can know if you're running even in the ball park in terms of mixture. Lots of threads on this.

 

--Rob

[wegweiser]

All the stuff others have stated (esp clutch slipping)

 

Graph your ignition timing advance curve and compare it to the factory manual graph. Having my distributor professionally rebuilt and re-curved by Advanced Distributors in MN (ask for Jeff) was the best $200 I've spent on my tii. Mark down the timing at 1200 rpm, 1800 rpm, 2200 rpm, etc... then compare to factory specifications. The original pre 74 tii distributor ends in Bosch nr "008". The Bosch substitute for this unit ends in "002" and is CLOSE to perfect...but not quite. You can have either one properly curved to 1972 "008" perfection, through the above company/service.

 

Should max out at 32 deg BTDC at any rpm above 2800-3000.

 

Generally speaking: Maximum advance setting (32 BTDC at 3000 rpm+) and presence of a correct curve is FAR MORE important than actual/absolute idle engine speed ignition timing. The idle timing will end up wherever it ends up. Focus on curve and the full advance numbers.

 

32.5, 33....are "ok" but mine is happiest at a dead nuts 32. I mark the front pulley and use an adjustable timing light using a known TDC #1 mark. See if the advance is linear, from initial (idle) advance to 3000 rpm or so. Make sure the kugelfischer gear (belt driven pump gear) is properly timed to the TDC mark on the crankshaft. Make sure the lower crank pulley isn't installed backwards (it will alter the indicated location of the timing mark and rub the plastic lower cover slightly, if so..... don't ask. *doh!*)

 

From my experience, 72 tii power is quite linear, a little beefier around 4400rpm+ as you'd expect, I suppose,  but smooth as silk.

Edited November 12, 2015 by wegweiser

[mvliotta]

Thanks all! Yes, I am having a blast now, although was a bit overwhelmed at first.

 

Sounds like I should get new linkages regardless and realign cam and screws on TB. I'll keep an eye on clutch as well.

 

FWIW, here is my advance curve after finding TDC. Looks like springs are a little loose? Is being out of spec at low RPM that big a deal? I have an -008 distributor.

 

LieslAdvance.pdf

 

Vince

 

 

[thehackmechanic]

Vince, after nearly 45 years, I can almost guarantee you that, unless the dizzy has recently been rebuilt, the advance will be sloppy as all hell. IMHO, the best you can do is:

 

--VERIFY THAT THE DIZZY IS ADVANCING AT ALL! You'd be surprised how many people time vintage cars without checking that the timing actually changes with RPM. Shine the light on a timing mark, any timing mark, and verify that it moves when you rev the engine up from idle and back down. If it doesn't, the dizzy needs to be rebuilt or replaced.

 

--Time it to spec (ball visible through the window at 2400 RPM).

 

--Do what Paul says and verify that the total advance is about 32 degrees. 

 

--If the above two don't roughly agree, the advance mechanism of the dizzy is probably sticking, and the dizzy probably needs to be rebuilt.

 

 

If you need to rebuild the three main options are:

 

1) Jeff at Advanced Distributors

2) A replacement dizzy from Ireland Engineering (about $180, comes with a Pertronix-like electronic triggering unit)\

3) The 1-2-3 distributor that has electronic rather than manual advance. Lots of recent threads about this.

 

Be aware, though, that after doing this, the car many not accelerate much differently. Some tiis just seem to have "it," whatever "it" is, and some (like my '72), no matter how much time and money and linkages and rebuilt Kugelfischer pumps and distributors I throw at it, never seems to get to the point where I think a '72tii "should" be. I'm not the only one who has had this observation.

 

--Rob

[wegweiser]

Your advance curve looks decent. See if you can eek out 32 or 33 degrees at the top end. The graph shows it being a little shy. Be sure to run high octane (at least 91 but preferably 93 octane) fuel. If neither is available, I'd be tempted to stick to your current timing numbers. 

 

Rob is right.... some cars "have it". I got lucky with my current one. I've been less than lucky with other 2002s in my past (carbed and injected).

[lilmo]

 

 

Rob is right.... some cars "have it". I got lucky with my current one. I've been less than lucky with other 2002s in my past (carbed and injected).

Interesting.  Then did some have it and others not have it from the factory?  I've got 150K+ in the seat of my tii over 20+ years, and sometimes it had it, sometimes not.  In my experience, the more it's driven, the better it runs.

[jgerock]

Interesting.  Then did some have it and others not have it from the factory?  I've got 150K+ in the seat of my tii over 20+ years, and sometimes it had it, sometimes not.  In my experience, the more it's driven, the better it runs.

It's nice to know these cars aren't all the same.  Multiple owners and various parts swapped between them all attribute to a certain "feel" when driven.   I must say that a thorough cleaning of the injectors along with proper linkage/valve clearance adjustments, good spark plugs/wires and a well sorted out distributor makes these cars fantastic to own.