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  1. #1
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    Twin Turbo Update...

    Go here for full thread --> http://bimmer.roadfly.org/bmw/forums/e31/5358686-1.html
    .
    Was able to repair the oil leak on the twin turbo today. Pretty simple fix that involved pulling the lower oil pan and welding in the steel bulkhead fittings. Here\'s a pic...
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    .
    While under the car, I took the opportunity to make sure that everything was buttoned up nice and tight. Everything looked good so I started her up and let her idle for 15 minutes so that the engine would come up to operating temperature. Checked for leaks and found everything to be dry so decided to take her around the block. Put about 3 trouble-free miles on her. :-)

    Upon returning, I let her idle again for 15 minutes without any signs of oil leakage. Unfortunaely, a small amount of coolant overflowed upon shut-down but that is likely the result of the new overflow tank I recently installed(will make a separate post about that shortly).

    All in all, I\'m really pleased with how things have progressed. I have to admit, though, that I\'m really anxious to turn up the boost (currently at 3 PSI). However, I must first get the O2 bungs welded in so I can monitor the air/fuel ratios. Would be foolish to melt a piston (or worse) after coming so far.

    The next step is to get some baseline numbers. These will come from three separate sources: 1) Split Second Controller; 2) Wideband O2 Controller; and 3) G-Tech Pro Competition.

    I\'ll spend the next few days working out ways to synchronize the data from each of these three units so that it will be more meaningful. I may need some help from Stuartyp and others who are more experienced with using the G-Tech as I\'m not very familiar with its operation.

    Before signing off, I wanted to again say \"Thanks\" to those of you who helped to make this happen. Projects like this are never the result of just one person and for your help I am thankful.

    Stay tuned.... Next stop..... 5 PSI.....
    - John

    BMWCCA #288391
    '92 850iA
    '00 R1100RT

  2. #2
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    Great to hear! I'm hosting another dyno war...

    towards the end of July/early August. I'll keep you posted.

    Thanks-
    John

  3. #3
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    Count me in, Rev...

    Would be great to see you again. Hope all\'s well w/you and the 5er beast. Rgds...
    - John

    BMWCCA #288391
    '92 850iA
    '00 R1100RT

  4. #4
    Jim Derrig 93 750
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    Re: Twin Turbo Update...

    Quite a project! I'm curious, did you make any significant modifications to the heads or bottom end (seems like they might not be necessary), or does the installation focus only on the turbos themselves and the corresponding engine management issues?

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    Not really much you can do w/the M70 motor...

    ...To begin, the motor comes with forged crank and rods from the factory. The stock hypereutectic pistons are quite good (for cast pieces) and should safely handle the 12 lbs of boost that is my goal. Forged pistons would be better, I know. However, in order to go to forged, you must sleeve the block - - which is something I am considering to do on a future project.

    As for the heads, I must tell you that there\'s not much that can be done with them. If you\'re familiar with the M70 head, you know that it is one of *poorest* head designs ever to come from BMW. To be fair, it does have great intake runners. However, the exhaust ports do a hard 90 degree turn to exit. Any attempts at re-shaping of the ports will cause you to break through into the water jacket. I\'ll see if I can dig up some cross section pics of the head itself and post later.

    One possibility for the future may be to install a 4 valve head. However, this will require lots of time and $$$. Right now I\'m just satisfied to have finished the project and to be dialing things in.

    Currently running 3 lbs of boost without incident. Hooked up my wideband O2 controller yesterday and things are spot on. I\'m really looking forward to turning up the boost. Rgds...
    - John

    BMWCCA #288391
    '92 850iA
    '00 R1100RT

  6. #6
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    Cutaway pics of M70 head...

    These are compliments of Ed Raether...
    .
    Intake
    Notice the smooth path on the intake side...
    .

    .
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    Exhaust
    Notice the abrupt 90 degree angle path on the exhaust port...
    .

    .
    Rgds...
    - John

    BMWCCA #288391
    '92 850iA
    '00 R1100RT

  7. #7
    Jim Derrig 93 750
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    yep . . .

    I've personally pulled the heads on my engine, and your great pics only confirm my overall belief that the M70 is a V12, but otherwise is not a great performance motor, or at least is not a great candidate for naturally aspirated "hot rodding."

    Personally, I think the engineers where mainly concerned with cost, weight saving, and packaging as far as the heads were concerned. The bottom is solid, however, so its not surprising that the McLaren boys chose it, as they probably would have afixed their own heads to whatever engine they chose.

    Hey, look at it this way: since the exhaust ports are constricted anyway, clogging the flow with a couple of turbos doesn't muck things up much! Combined with the decent intake flow, turbos seem the most logical performance approach.

  8. #8
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    Couldn\'t agree more, Jim ....

    It\'s almost as if BMW intended for me to turbocharge this car. Stock fuel pumps will flow (at pressure) enough fuel to make 400 HP each. Engine bottom end should be good to at least 1000 HP. No vacuum-controlled accessories on the entire car. Oh, and it\'s OBD-I so it\'s easier to handle fuel management issues.

    I could go on and on but suffice it to say that this car *NEEDS* forced induction. If not to overcome it\'s heavy weight, then to overcome those crappy exhaust ports. He he.

    Rgds...
    - John

    BMWCCA #288391
    '92 850iA
    '00 R1100RT

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