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Help please with tuning 2002 BMW factory turbo, Byron Tom et al.


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Tom, Byron, and Sean; Gents, please help me with your advice and expertise. The BMW 2002 turbo OEM crate motor, with rebuilt mechanical fuel injection from Hans in New York, rebuilt turbo, properly set up ignition and timing, Properly set valve timing, is not pulling cleanly above 4000 RPM. It will run out/rev gradually with part throttle above 4000 RPM, however, if you open the throttle fully/further it stumbles, and missfires Above 4000 RPMs.  The turbo boost gauge demonstrates boost, it never pulls fully into the green section of the boost gauge. The car feels strong, and is tractable under 4000 RPMs. I realize that 4000 RPMs is when  the car should start to make power and really take off. After pulling the plugs,  they are  somewhat sooty however I understand the Tii  and turbos usually run Rich. I am unsure what to check next, is it possible , that the throttle linkage, which has been set up according to TII specifications along with the idle, may be a factor.  Please help with recommendations for things to check. Thanks again, for all your kindness.  sincerely Peter


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Are you running points, Pertronix or Crane?


What's the timing set to?

I was having a misfire stumble ant 3500rpm. Turned out my distributor was worn and wobbling. I replaced it aith the IE unit, 32° @3500rpm


Is the K-fisch pump synched with the trottle body?

Do you have the tools to do that?


What plugs are you running?

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Thanks andrew, the Car is running stock new points and condenser. Timing is set to factory turbo specs, I did synchronize the kugleFisher with the throttle body, with my friend Sam Mcnutt's help, he had the  specific tools. The car is running plugs that are one heat range above stock, Bosch eight I believe. The distributor has approximately 60,000 miles on it, and ignition purity and correctness is one of the questions. I.e. whether the distributor, or coil could be a factor. We're trying to eliminate all ignition issues first.  I had a similar problem to yours years ago with my 1972 Porsche 911, which had an evil Italian Marielli distributor, which miss behaved in the mid range. I ended up switching to a Bosch distributor and that was cured. This miss fire and stumble appears and feels much more profound, as the car  bogs down completely and will not pull above this range at all.  Thanks for your help,  sincerely Peter

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I would get a wideband on it to see if its running rich or lean when the stumble occurs. In addition, it's very likely a worn distributor. 60,000 miles can destroy a distributor cam if it hasn't been lubricated or maintained ever.


On a factory turbo engine I wouldn't risk any kind of stumble or hesitation. leaning out could kill the engine. having your distributor fire off at random times could cause detonation. 


Get the distributor sent off for testing and adjustment. 

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Did you try to set the idle speed and mixture the way you would a tii?  Speed with the screw outside of the tuna can, mixture with the screw inside?  If so, that could very likely be your problem, or a large contributor.  The factory manual supplement or the turbo supplement on Richard Stern's UK 2002 site lists the proper method of setting the idle and mixture on the turbo.  


Basically, sync the linkage like you would the tii and set the outside tuna can stop screw so that the D cam rests on the sync pin.  Now leave that screw alone and use the small inside screw to set idle speed.  Idle mixture is set using the air bleed inside the altitude compensator.


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I will preface my post by stating that I have no direct experience with tuning or working on a 2002 Turbo, but I have a decent amount of tii and a lot of Porsche turbo experience.

After checking distributor function as mentioned, I would check for vacuum/boost leaks. In turbocharged cars they sometimes only show up under heavy load.

These engines have a turbo boost-dependent fuel enrichment function. You should be able to check its basic function by applying regulated air pressure to the port on the injection pump and checking for a change in CO and A/F ratio. If you don't have a wideband O2 sensor or gas analyzer, you will likely be able to detect a change in mixture by observing the idle RPM. If nothing happens then you have a problem.

If it works, check again for boost leaks and fine tune from there. A wideband O2 sensor and/or a professional dyno session would be wise, you do NOT want this engine to run lean!

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are you sure you have the "altitude compensator" hooked up correctly and adjusted? The Turbo enrichment under

boost is controlled by the "AT" The reason there is a filter on it is because under vacuum the engine is drawing

some air through the "AT" but under boost it is pushing air OUT of the "AT" There is a V shaped slot inside that

allows air to pass through under deceleration or light throttle. By opening up that slot you lean the mixture, at

the same time you make a small change under boost towards richer. The bellows inside the "AT" is designed to move

plate over that slot based on altitude. Under boost this plate is designed to BLOW up off that slot because the

plate is held down with a small spring. If this spring does not allow the plate to move under boost the mixture

will be way off.

Setting the basic settings are just like a Tii, you need the tools to align the throttle plate and the pump. You

need to check the length of the rod between the pump and the bellcrank. After that the adjustments are nothing like a Tii. Send me your email address and I will send you a copy of the Turbo injection instructions. There is a

good chance you will need to adjust the "Verboten Screw" The guys that set up the pumps don't have a lot of

knowledge about Turbos and I have found they are usually way too lean right out of the shop.

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"further it stumbles, and misfires Above 4000 RPMs" Sounds like an ignition problem-think like a rev limiter.


Does it "pop" and backfire or just seem to stall and stop accelerating?


At that rpm you should be boosting which could make it lean out if no enrichment obviously.


Do you see black/brown smoke pumping out the back when this happens? Might be too rich but unlikely.


A wide band o2 sensor will help you determine what is going on under these fuel related conditions. I just installed a $110 plug and play unit from www.wide-band.com and it is a nice little package.


Boost control:  I plumbed a hose directly from the spools out pipe (instead of from the intake manifold) into the boost aneroid with a vacuum valve to close it under normal operation. It helped a lot with my car, but I am running rich and any air leak causes the idle to go up.


The AT will help you with your idle but sounds like that is ok.


I too have a similar issue but only at the low end below 3500 rpm. So I am going the crank trigger wheel and Megajolt controlled dist-less system. Your dist may not be doing its job. The turbo's had their very own dist and curve. If you are using another type like a tii, it might explain a few things.


If I had to guess it sounds like your ignition is the bigger problem.  You could.

Check your dist for proper function and curve.

Check your coil. should be running a Bosch RED unit.

Install an optical or magnetic ign sysytem Ala Pertronix

Get a spark controller like Crane XR 700 or other






Byron: what can you tell us all about the function and setting of the enrichment aneroid? Will a lighter spring inside cause an earlier enrichment action. What is the desired pressure to move the inner piston? Is there any fine adjustments you know of to make the enrichment more or less that is not the linkages or forbidden screw?


These turbos are such mysterious creatures.

Good luck, we need a specific forum with a guru for turbos, no?

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The real hiccup with this system is it relies on a certain amount of air leaking around the piston in the enrichment aneroid.  If you just block off the "AT" the pressure across the piston balances out and the piston returns to the middle position (too rich at idle and too lean on boost)  The more of that air that is allowed to flow out/in through the "AT" the more the piston moves.  It is counter-intuitive but it is the way it works.  The trick to changing spring tension is you need to balance it on both sides of the piston.  At 0 vac/boost the piston should be in the center of the housing (there is a mark on the gear and pump body to line things up)


  I have wondered if you could offset the piston so it had more travel towards the boost side so you could run more boost and get the fuel enrichment to match.  I just have not taken the time to try it.  If I was really thinking about making serious HP with a M10 Turbo I would not use the Kugelfisher pump.  Modern EFI and turbos are so much better.  I did build an engine for a customer using a modern T3 turbo with integral waste gate,  I set it to the original 7.5psi boost and used the factory injection pump. It makes 5psi of boost at 2500 rpm and 170 lb/ft of torque by 3000 rpm,  it makes the same peak torque and HP as the factory KKK turbo but comes on 1500 rpm earlier!   

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Just for conversation purposes:


My current set up with dist still in place. Plan to remove the dist entirely and run EDIS with a spark map to advance when off boost and retard when on boost.


The hoses in the picture are I believe properly connected to their respective counterparts.


The Alt comp is connected to the base of the boost aneroid while the enrichment is at the top of the aneroid. The brake booster benefits from a dedicated port.


I added in the vacuum valve to open under boost when the manifold pressure increases thus pushing more air into the mani and the aneroid. Might explain why it tends to lean out ( according to the wideband) under full boost.




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I have zero experience with the factory 2002 turbo but know there are some specs and info on the turbo models  published in the MaCartney restoration book along with the 2002tii fuel injection manual.


As with any older vehicle (specifically with mechanical fuel injection), use the factory settings as a baseline, then tweak from there.  The relationship between the KF pump and throttle body (vertical linkage/coupling) is very important even after ensuring the horizontal linkage pieces are correct. You may have to alter the factory-specs to get the car running properly.  Also make sure you don't set the accelerator pedal linkage too tight or else the idle speed will be too high and you will fight more gremlins.  BTDT.


Lots of good folks here with a plethora of information - it just takes some time to work it out.


ps: tii mantra - check out the ignition components before messing with the fuel injection system :) .



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