Tii throttle body: matched set with engine? Or pump?

[dlacey]

All,

Just an observation... In the tuna can/TB of the Tii we have the 4mm stop/hole that is used as part of the basic calibration/setup for the fueling.

That 4mm hole is eccentric in a part that's adjustable and locked/sealed underneath the tuna can:

 

I took a look at 4 throttle bodies, the position of the eccentric varies quite a bit...in addition there are some numbers stamped on the outside of the body:

 

 

Got me wondering what was the factory calibrating with this eccentric?  Was it variation in TB assemblies, or variation in the whole mechanical assembly between TB and the kugel?

If it's the latter, then that would mean the TB is matched with the kugel and/or the engine...and that if we swap out one part we may unintentionally destroy this calibration....

Anybody got info on this??

[jgerock]

I have wondered the same thing.  Per BMW, the throttle body should match up with the pump.   

[ray_]

I'd wager the locked adjustment standardizes proper calibration when inserting the pin and setting that tolerance,

 

Cheers,

[adawil2002]

Ray's correct. The pump lock tool & eccentric pin allow the pump to calibrate to the throttle body. Mechanical fuel injection parts are interchangeable and not coded to each other or the engine.

 

Now when you get to D-Jet systems on the CS coupes, the ECU and MAP (Mass Atmospheric Pressure) Sensor are coded to each other. So a Red dot will not sync to a Yellow dot MAP Sensor. 

Edited November 24, 2018 by adawil2002

[dlacey]

6 hours ago, ray_ said:

I'd wager the locked adjustment standardizes proper calibration when inserting the pin and setting that tolerance,

 

Cheers,

Sure yes, but given the differences in the 4 pics then if I change the TB I will get a different setting...so the TB must have been matched to the engine/linkage or kugel somehow

[wegweiser]

Alright….don't everybody freak out!

 

That hole is just for INITIAL setting, to get the car running. Actual tuning of fuel mixture, idle mixture, and synchronization requires allowing the D shaped cam to overlap that hole a little bit, so the drill bit / pin tool isn't even in play, once you're getting in to the deep end of tuning the thing. You'd be surprised by how much improvement you can gain by fiddling with the verboten screw, synchronization adjustment on the vertical throttle rod, and ignition timing.

 

I suppose, if you're really anal retentive, you could loosen the jam nut under that eccentric pin hole fixture and rotate it so that it's just right, AFTER you establish really nice fuel mixtures and synchronization….THEN using the pin tool would yield you reliable, repeatable results in setting the D shaped cam. Since most tiis have probably had their throttle bodies replaced or fiddled with (or just have normal 45 year old WEAR), that eccentric is never to be trusted, IMHO.

 

Having a wide band Oxygen sensor / AFR gauge will show you the results so you're not just guessing all the time. I generally loathe bolting modern stuff on my old car, but the AFR gauge was affordable, easily removable, and really helped me get the most from my tii, while reassuring me that I wasn't melting 10:1 pistons on street fuel at high rpms. 14.7 may be the "perfect" mixture - but the power happens at around 12.9! 
 

Also - Fuels today are very different from 1972 fuels. A mixture setting that worked great in the 1970s may not be the best mixture for 2018. Related to this, is the fact that in many parts of the country, the "winter blend" fuels will really mess with your mixtures. I discovered this a few weeks ago. My cruising AFR went from about 12.9-13.9 to 16.0+ (!) I backed off the timing on a road trip I was on, because (at the time)  it was the easiest way to richen up fuel mixtures at high rpm, without pulling an intake runner off, and messing with the verboten screw, etc. 

 

So… with that said, get an AFR gauge and tweak things til it screams the way a tii should! 

 

 

Edited November 24, 2018 by wegweiser

[adawil2002]

I use an exhaust gas analyzer for tuning, ideal CO is 2%.

[wegweiser]

3 minutes ago, adawil2002 said:

I use an exhaust gas analyzer for tuning, ideal CO is 2%.

2% is ideal perhaps to get you through 1970s USA emissions (pffft!), but most of the cars I've tuned are MUCH MUCH happier with fatter fuel mixtures.

 

[Einspritz]

19 minutes ago, wegweiser said:

2% is ideal perhaps to get you through 1970s USA emissions (pffft!), but most of the cars I've tuned are MUCH MUCH happier with fatter fuel mixtures.

 

 

1.5% should get you to pass California emissions as I did, and that is fine for a setting at idle or partial throttle.  But if you keep 2% at WOT and full load, you are going to run lean and thus hotter, then the likelihood of burning a valve is high.

 

Depending on fuel, the WOT CO should be at or around 3.0-3.5% +/-, maybe nudging toward 4%, but certainly not at 2%.

 

I agree that a Lambda sensor is best for tuning. Extra credit for a knock sensor.

 

 

[adawil2002]

23 hours ago, adawil2002 said:

I use an exhaust gas analyzer for tuning, ideal CO is 2%.

 

Checked with VSR, we are running between 3-3.5% CO.

[jgerock]

On 11/24/2018 at 8:34 AM, wegweiser said:

Alright….don't everybody freak out!

 

That hole is just for INITIAL setting, to get the car running. Actual tuning of fuel mixture, idle mixture, and synchronization requires allowing the D shaped cam to overlap that hole a little bit, so the drill bit / pin tool isn't even in play, once you're getting in to the deep end of tuning the thing. You'd be surprised by how much improvement you can gain by fiddling with the verboten screw, synchronization adjustment on the vertical throttle rod, and ignition timing.

 

I suppose, if you're really anal retentive, you could loosen the jam nut under that eccentric pin hole fixture and rotate it so that it's just right, AFTER you establish really nice fuel mixtures and synchronization….THEN using the pin tool would yield you reliable, repeatable results in setting the D shaped cam. Since most tiis have probably had their throttle bodies replaced or fiddled with (or just have normal 45 year old WEAR), that eccentric is never to be trusted, IMHO.

 

Having a wide band Oxygen sensor / AFR gauge will show you the results so you're not just guessing all the time. I generally loathe bolting modern stuff on my old car, but the AFR gauge was affordable, easily removable, and really helped me get the most from my tii, while reassuring me that I wasn't melting 10:1 pistons on street fuel at high rpms. 14.7 may be the "perfect" mixture - but the power happens at around 12.9! 
 

Also - Fuels today are very different from 1972 fuels. A mixture setting that worked great in the 1970s may not be the best mixture for 2018. Related to this, is the fact that in many parts of the country, the "winter blend" fuels will really mess with your mixtures. I discovered this a few weeks ago. My cruising AFR went from about 12.9-13.9 to 16.0+ (!) I backed off the timing on a road trip I was on, because (at the time)  it was the easiest way to richen up fuel mixtures at high rpm, without pulling an intake runner off, and messing with the verboten screw, etc. 

 

So… with that said, get an AFR gauge and tweak things til it screams the way a tii should! 

 

 

Yup!  also the distributor condition and advance curve plays a major part in how these run. BMW Engineers earned an A+ for developing the tii. Most nonBMW owners will give me puzzled looks when I tell them my car doesn't have any emissions controls other than vapor recovery.

[ray_]

Timed direct injection is good for efficiency and emissions, as you know. ?

 

Cheers,