engine and drivetrain Which Tii Throttle Body Is Early And Which Is Late?

[thehackmechanic]

Byas, no, I did not lengthen the rod as I moved the cam over the hole.

 

Thanks for the offer on the loaner TB.

 

I'll try more things tonight.

[BillWilliams]

Ok, what about timing? Did you use the conventional timing method or the "The Keith Kreeger Special Sauce" method?

[thehackmechanic]

Bill, I'd previously timed it by the book, using the timing ball at 2500 rpm. I changed to timing it at 32 degrees total advance, which shows the timing ball at about 2100 rpm, and is therefore cranking in more advance. I am not hearing any pinging, even under load, even with this lean condition, so I'm assuming I don't have it too far advanced.

[jgerock]

Bill, I'd previously timed it by the book, using the timing ball at 2500 rpm. I changed to timing it at 32 degrees total advance, which shows the timing ball at about 2100 rpm, and is therefore cranking in more advance. I am not hearing any pinging, even under load, even with this lean condition, so I'm assuming I don't have it too far advanced.

 

I'll ask again (maybe it disappeared):   Since you got Jeff S. at Advanced to rebuild your distributor, it should have been in a ziplock bag with the recommended timing (possibly 10 degrees BTDC at idle) written on the bag (mine was).  If the unit was recurved, then the stock and any other timing methods should be used with caution.

 

Before the distributor rebuild, I ran the KK 8 degrees on the front timing mark at idle with success.

Edited April 30, 2013 by jgerock

[bnam]

Bill, I'd previously timed it by the book, using the timing ball at 2500 rpm. I changed to timing it at 32 degrees total advance, which shows the timing ball at about 2100 rpm, and is therefore cranking in more advance. I am not hearing any pinging, even under load, even with this lean condition, so I'm assuming I don't have it too far advanced.

 

25-26deg (the ball mark) at 2100 rpm is outside the spec for the Tii per the bluebook, but not sure that is an issue -- your max is still within the range.

 

 

 idle

 

At what rpm do you have idle set at?  Apparently the pump is really sensitive to being less than 1000 ... see this thread about 6 posts down.

 

http://www.bmw2002faq.com/topic/21339-kitty-kitty-kitty-at-what-point-is-af-mix-too-lean/?hl=redzsus#entry803894

[thehackmechanic]

Jim, thanks for reminding me about Advanced's recommended settings. I may have to call them. I am, however, very leery of any setting at idle, as "idle" is pretty subjective.

 

Similar response to Byas. I've been paying zero attention to idle. I make a change, get the car warmed up, screw in the idle screw on the side of the tuna can enough so it doesn't stall, that's "idle" for me.

 

Interestingly, if I drive the car while it's in warmup and nail it, the AFM gauge reading at WOT can fall into the desired 13.5 to 14 range since the warm-up regular hasn't come off the hat yet so the verboten screw isn't down on the stop yet. This is further evidence (to me, at least) that I don't have a fuel delivery problem.

[bnam]

<<The Blue BMW fuel injection manual shows both on page 8 and but does not have notes indicating which one is which!>>

 

Yup, so you see why I want a definitive answer from the cognoscenti. Redszus and posts here on the FAQ say that the TB is curved to the pump -- early pump needs early TB. Andrew Wilson says Vern, built March '73, has the one on the right, so he agrees with you, but you two don't agree with the previous two posters.

 

This was probably answered in a round about way.  But for future reference, while the injection manual does not state explicitly which is which, all instruction pics on show the early one in an early car with plastic tubes.  So, the other must be the late one (and that's the one on the right in the above pics).

 

Rob,

Did you get the not getting to WOT issue resolved.  After reading your issue, I decided to double check on mine and i was not getting to WOT either with pedal fully down.

 

In my case, it turns out there is a bit of play in the system that I needed to take out.  After confirming that pump was correctly synched at idle and WOT with the throttle, I disconnected the safety clip at the firewall bell crank and removed the pin to decouple the vertial linkage from the crank.  I then pressed down lightly on the crank to take up the play (throttle nor pump crank should move), screwed the pin down a few turns to fit into easily into the pressed down bell crank.  This took the play out of the system and now I have WOT with pedal fully pressed down.

 

ANd, one more question -- you started the thread with the issue of not getting to WOT.  So, when you say you are only getting to 15.x AFR at WOT is it truly at WOT or at pedal fully down (but not quite WOT)?

 

Byas

 

[thehackmechanic]

<<Rob, Did you get the not getting to WOT issue resolved.  After reading your issue, I decided to double check on mine and i was not getting to WOT either with pedal fully down.>>

 

Yes I did, by using Matt Cervi's recipe. But it made no difference.

 

<<ANd, one more question -- you started the thread with the issue of not getting to WOT.  So, when you say you are only getting to 15.x AFR at WOT is it truly at WOT or at pedal fully down (but not quite WOT)?>>

 

Yes that's correct. Last night I played with three linkage rod lengths:

1) Longer than the Fahuna rod, using Matt's method of making sure that both the pump and the throttle move their full range of motion.

2) The brand-new Jack Fahuna rod (which is slightly longer than my Asvander 85mm jig).

3) A rod that I comically shortened much shorter than 85mm (so the throttle body could NEVER go wide open) to see what would happen.

 

With each of them, I set the injection up to spec, pinning the pump and the cam in the tuna can, then progressively moved the cam further over the hole. With each of them, the car went progressively richer as I moved the cam in until the car was running at the left end of the AFM gauge (10) at a range of RPMs. But, with each of them, it had virtually no effect on the AFM reading at wide open throttle -- it stayed stubbornly around 15.

 

Which tells me that my problem is not a synchronization problem.

 

On the other hand, the fact that the pump was just rebuilt by Hans Utke strongly implies that it is set up correctly (I will call him and sanity-check all this).

 

And the fact that, if I put a shim under the verboten screw, I DO get below 14 at WOT tells me it's not a fuel delivery problem.

 

Can't... sleep... can't... work... can't... think... about... much... else...

 

Will try the other throttle body when it arrives and see what happens.

[saaron]

I have been following this and am by no means an expert.  Here are a few ideas fwiw.

 

-Could it be a measurement problem somehow - measurement of the AFM (not linkages)?

 

-Could there be an exhaust leak that only manifests at WOT/higher rpm?  Never heard of that, but we're kind of in "have to look outside of the typical situation" mode.

 

-I have never heard this being a problem, but could the fuel lines coming out of the pump going to the injectors be slightly gummed up so they flow fine at less throttle, but not perfectly at WOT?

 

Again fwiw.  

[BillWilliams]

Rob, please send me an e-mail billwill72tii     at     verizon     dot      net

[MatthewCervi]

If the problem is made better by shimming the "verboten" screw, could you just adjust the screw to fix the WOT problem and then use the screw in the tuna can and some linkage adjustments to lean out the rest of the range?

 

I know people avoid adjusting that screw (and are generally wise to do so), but there's a reason BMW made it adjustable and not fixed.

[thehackmechanic]

Matt, I agree, and if I don't come up with any ideas, I may well do this, but jeez louise I hate to turn that screw after having paid nearly a thousand bucks to have one of the experts rebuild the pump.

 

Scott, the fuel lines are new, but I've thought of your other two points. I have no reason to suspect the AFM itself since in general the readings make sense. An exhaust leak is certainly possible. Also, as I've posted, this car has somewhat uneven compression (130-160) and HORRIBLE leakdown numbers (nearly 40%), both presumably from stuck rings from having sat for nearly 10 years. Leakdown is usually air getting from the combustion chambers past the rings down into the crankcase. I've never gotten an answer to the question of whether extra air can get into the cylinders by going the other way and lean things out.

[MatthewCervi]

I had forgotten about the compression numbers on your engine.  I guess that could be a factor...definitely beyond my knowledge of engines.  But that leads me to another thought:  the money you spent getting the pump rebuilt isn't wasted--you now have a known good pump set up for an ideal (meaning perfectly to spec) engine.  But you don't have that engine.  Tweaking the settings on the pump to fit your particular engine isn't unreasonable.  Just make note of what you change so that if you get the engine rebuilt someday, you can go back to spec and tune from there.

 

One more thought:  maybe you're suffering from too much data here.  You've said you're not seeing any symptoms of being overlean (i.e. no pinging) other than the numbers on the AFM gauge.  The Germans didn't have access to that kind of reading in the 1970s so they couldn't tune the engines perfectly either.  Maybe after taking a few steps to make sure the engine isn't too, too lean at WOT you should just enjoy driving the car and not try to chase perfection.

[thehackmechanic]

Yeah, I know; I need to take a stress pill. But when you see that gauge swing lean, what are you supposed to do, keep standing on it?

[MatthewCervi]

Yeah, I know; I need to take a stress pill. But when you see that gauge swing lean, what are you supposed to do, keep standing on it?

Duct tape over the gauge...it's the answer to everything!  No, that's bacon, never mind.