Announcement

Collapse
No announcement yet.

VGT Turbo M20 Sleeper ('87 325 Sedan)

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    #91
    I'm in the same boat, though - I think my timing map is pretty conservative at the moment, except for maybe at peak torque at a little over 5000rpm where I can hear the slightest knock if I add any more timing. I'm looking at getting some dyno time in the near future, turns out these guys are not too far from me and have more old BMW experience than any other shops around here, and seem laid back about letting me do the tuning myself. Also seem quite confident that they've developed good timing maps for turbo M20s specifically. Mine might be a little more limited than most due to eta pistons with 885 head.

    Comment


      #92
      Z3 rack swap started, about 30min and close to pulling the rack out. Just need to loosen motor/trans mounts, lift the engine an inch or two, and then should be able to pull it. Garagistic swap kit should finally arrive tomorrow. They were backlogged on delrin steering couplers, with they delay they offered to swap me for aluminum and they discounted me without me asking or without them even mentioning it. Such a great supplier!!

      Hey Future Self: this last part of pulling the old rack probably didn’t end up being as easy as you thought!

      Comment


        #93
        Biggest pain on removal: splines didn’t want to let go on the rack end of things, but not too terrible. The rack is totally free now, and almost has enough room to escape its confines behind the oil pan, but not quite. Don’t want to bend the tabs, so next I just need to jack the engine an inch or so, but wife and baby are asleep above the garage some I’m not going to make a huge racket rolling the floor jack around tonight.

        Comment


          #94
          Rack came out without a fight this morning, lifted the engine about 1-1.5" and there was plenty of room (not too hard, undo downpipe-to-midpipe v-band, pop air filter off turbo, loosen intercooler supports, and lift). Had to do a little persuading to get the knuckle assembly off the steering column. Ready for modification/rebuild, Garagistic kit out for delivery. We'll see how well the splines go back on...

          Comment


            #95
            Z3 rack (“031”) install finished, also swapped the solid aluminum transmission mounts for 95a Garagistic poly and replaced the steering flex disc with aluminum. Quick and rough home garage alignment and a 5min drive, whoa, what a difference! Partially from the quicker rate, yes, but also the lack of slop now. Huge improvement!

            Comment


              #96
              Originally posted by mikey.antonakakis View Post
              Z3 rack (“031”) install finished, also swapped the solid aluminum transmission mounts for 95a Garagistic poly and replaced the steering flex disc with aluminum. Quick and rough home garage alignment and a 5min drive, whoa, what a difference! Partially from the quicker rate, yes, but also the lack of slop now. Huge improvement!
              I have the Z3 rack on my E30 as well. Makes a huge difference coupled with a slightly smaller steering wheel. (370mm vs 385mm)
              Difference between feeling like driving a bus, and a sporty car.

              Definitely go for an alignment. I basically toasted a set of front tires driving around with my garage alignment for a few months.
              My Build Threads:
              '87 BMW E30 325is Turbo
              '86 BMW E28 535i
              '98 BMW E36 328i
              '90 Mazda NA Miata Turbo
              '04 Jeep TJ
              '05 Yamaha R6

              Comment


                #97
                Okay, time for some fun stuff, more data! The big updates are that the car now has EGT and exhaust manifold pressure measured at the turbine inlet. It's also running the turbo control system (wastegate dome pressure control and VGT control) on the new PCBs I designed.
                So now with EMAP I can calculate drive pressure ratio and see the effect of the VGT. I can even do something like alter my VGT algorithm to seek a target drive pressure ratio (say, 2:1) during spool-up, rather than having an open-loop setup.

                Quick sample datalog below, 1st through 3rd gear up to ~30-105mph in about 10s, not flatshifting. Note that the bottom plot is recording wastegate dome pressure, turbo speed, VGT vane position (calculated as nozzle size), EMAP (exhaust manifold pressure), EGT, and drive pressure ratio.

                I think I can get more aggressive with the VGT actuation, drive pressure ratio starts to drop immediately as boost builds, peaks around 1.4:1 near redline with vanes (almost) fully open. Dome pressure control is working great, within 0-5kPa of boost target, and it's in a sort-of open-loop mode (not trying to directly control MAP). Note also that wastegate dome pressure is kept high during spool-up to ensure the wastegate stays closed.

                Click image for larger version  Name:	image.png Views:	0 Size:	116.0 KB ID:	10069915
                Last edited by mikey.antonakakis; 09-28-2022, 01:55 PM.

                Comment

                Working...
                X