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1973 2002Tii passed from father to son.

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Over the next little while I will be using this thread to document my tuning progress/experiences. This will be a bit long winded,but lets start with some background...

In 2012/13 my tii was fully (mechanically) rebuilt by non (2002/Tii) experts, and then tuned by someone who knew more than the first guys (a benz guy). My car has a stock engine but with the canadian/euro spec 9.5:1 pistons. Aside from finding the timing chain master e clips in the oil, and having a passengers side engine mount bracket break (because another bracket that stops the forward movement of the mount was not installed...), the car has done well. Aside from adjusting the idle speed a touch, i have left things alone.

Gus Pfister rebuilt my pump/warmup regulator to spec, and my tuner had to make new throttle linkages. I had no point of reference, but the car ran well. The car usually started first or second try cold, and immediately when warm. Idle was around 800rpm.

Last year i had to bump up the idle speed as it was becoming low and going up and down a bit. in the last year, cold starts have become slowly and progressively worse, but the engine cranks over "ok". I think my battery is weak, and this would make sense given the progressivly worse cold start issues. Plus, the batter was charged post winter and it started on 1st try. It does start better after it has run recently. 2-3 tries if driven in the last few days vs maybe 3-6 after prolonged rest.

Afr's are measured by an aem gauge. cold starts are very rich as expected. When the car is warm, afr's are in the 11-13 range on light throttle, with a sudden jump to 15 with maybe 60-95 percent throttle. WOT is in the 13.5 range, closer to 14 when the engine is hot and if uphill. Air filters still look pretty good. My goal is a richer wot and near full throttle, and maybe lean out the light throttle (ie try to get everything near 13, maybe a little leaner on light throtttle).

I have the factory kugelfischer manual (gave it to the tuner, learnign now that he probably did not use it). I am no expert, but I opted to start running through the factory setup starting with removing the throttle linkage on the KF pump. "Adjusting the pump throttle/linkage" section. Rough measurements had it near a cm longer than the 85mm factory spec. So I began to shorten it to find out that it it's shortest, it was still 87-88mm.

So my first thought is to get it shortened, and press on through the factory setup. Now, i am a non expert (but smart enough to know i do not know enough). A trusted mechanic (who should be doing this work... But i want to learn) has a saying that goes something like "you need to know the difference between scratching your a$$ and tearing out your a$$hole". This situation of whether or not I should leave well enough alone makes me thing of his words.

So question number one is do i leave this longer than OEM spec linkage alone? or do i plow through until everything is oem spec (and get it shortened)... So that i will have a better point of reference for the future? My personal goal is to get everything OEM, otherwise future tuning will be a bit haphazard. .

Notes to ponder.

- Ensure sufficient fuel pump pressure to kf pump (fuel filter?) re issue of near full throttle being so lean.

- verify clean air filters (should be fine as things not going rich)

- clean fuel injectors?

- verify battery is fine re poor cold starts (it is less than 80% according to my battery tender, and that is one day after a 1.5hr run).

- given the cars starts better after recient use, I assume my alternator is fine.

- I assume warmup regulator is fine as Gus rebuilt it to spec recently. .


Thanks for any help/words of wisdom along the way.

Source: Adventures in 73 Tii throttle/afr tuning



This is my 1973 BMW 2002Tii. It was ordered new from the factory by my dad in 1973 and has been his until he gave it to me in the Fall of 2012. Most notably, it was oversprayed in the late 80's after a freak summer hailstorm accident, and in the mid/late 90's the KF mechanical fuel injection was swapped for dual weber 40 DCOE's due to lack of local ability to fix it (pre-internet).

When I took ownership of the car in 2012 it had just suffered a piston ring failure. I began my first dive into the world of managing a car restoration with what would eventually become a top and bottom engine rebuild, KF rebuild and re-instillation, full suspension upgrade, and a series of smaller updates and fixes. After 10 months this all culminated in a glorious 2 day BMW high performance driving school with my Tii.








Note, I have an old blog here, but I will slowly be updating it in this new format.

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