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    #46
    Why would the m20b25 have significantly higher revs than an m30b35 ? Aren't they basically the same engine design?
    Never argue with stupid people, they will drag you down to their level and beat you with experience. -Mark Twain

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      #47
      Rama is developing a m30 itb kit which should help. It's still much harder to get lift though as it's a lower rocker ratio than the m20 so you need quite alot of duration which is not a good thing. The L/D for m20 is better

      The m30 has much bigger cylinders than the m20 1.4 x yet the valves are only 5mm bigger iirc. It's the same reason why a m20 stroker doesn't rev as high as the smaller engines with same development the big cylinders use the available airflow at lower rpm

      The m20 and m30 are vastly different, they both have 6 cylinders though
      Last edited by digger; 02-27-2018, 02:48 PM.
      89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

      new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

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        #48
        i'm guessing the intake manifold.
        maybe the port & head design?

        it's basically the same, but not really. Should it rev as high as the m20? idk.
        i try but it's not having it even with a "big" 294/273 cam

        Comment


          #49
          Originally posted by Bearmw View Post
          Why would the m20b25 have significantly higher revs than an m30b35 ? Aren't they basically the same engine design?


          WAT???

          No, the M30 is an M10 with 2 more cylinders. It's a 1960's engine, with
          huge diameter and width bearings, 100mm bore centers, a massive block, and a pretty advanced head-
          for 1962.
          The displacement was originally something like 2600, but it bored and
          stroked out to 3500 by the end.
          Different heads, too.

          The M20 was the 'lightweight' economy engine. Smaller bearings all
          around, narrower bore center, oil return external to the block (bitch tube)
          and other economies. Like the dinky little cam oiler tube, unsupported in
          the middle.

          t
          'respect your elders'
          now, sometimes I just mess with people. It's more entertaining that way. george graves

          Comment


            #50
            Originally posted by LowR3V'in View Post
            i'm guessing the intake manifold.
            maybe the port & head design?

            it's basically the same, but not really. Should it rev as high as the m20? idk.
            i try but it's not having it even with a "big" 294/273 cam
            No, Digger has it right. It has huge bores with big combustion chambers which are not efficient, not to mention issues with having a high enough VE to actually fill up that volume with air at high RPM.

            There's a reason basically all modern BMWs target a 500cc cylinder volume. Notice basically all BMW engines now are multiples of 500cc - 1.5l for 3 cylinders, 2.0 liters for the 4 cylinders (or less), 3l for 6 cylinders, 4l for 8 cylinders (S65), and 5l for 10 cylinders (S85). Where they go bigger the efficiency goes down.

            Sorry to the M30 lovers but something like an M54 or an N52 makes more power and more torque, weighs less, and is more fuel efficient too. The M30 is just cool because it's old-school technology and you basically can't break it.
            Build thread

            Bimmerlabs

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              #51
              Also the m30 was a hit as it was the most powerful non-M engine for a long time. It was offered in many larger cars that were being thrown away. Just like modern times, the junkyards are filled with m54's.
              john@m20guru.com
              Links:
              Transaction feedback: Here, here and here. Thanks :D

              Comment


                #52
                Originally posted by nando View Post
                Sorry to the M30 lovers but something like an M54 or an N52 makes more power and more torque, weighs less, and is more fuel efficient too. The M30 is just cool because it's old-school technology and you basically can't break it.
                stock yes, but a mild M30 build would be a different story
                89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

                Comment


                  #53
                  as would a mild M54 or N52 build. I mean, a basic tune on a stock N52B30OL is 265bhp. You're not getting there with a mild M30.. and not at the weight of an M42. :p
                  Build thread

                  Bimmerlabs

                  Comment


                    #54
                    i agree the stock 8:00:1 M30 is a boat anchor mild spec (10.1:1 CR, cam, exhaust) m30 were circa 260bhp and 240lbft in the 80's on motronic. a bit more a rub here and there youd be able to beat that.

                    on the more extreme end i wanna see someone do a 4.0L m30 with RHD ITB, one of his roller rocker and cam combo
                    89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                    new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

                    Comment


                      #55
                      How is the M30 crank for harmonics? The M10 cranks are fine,
                      but they're 2 pots short.

                      Given that a 150 hp m10 is pretty mild, 225 bhp on a b30 seems pretty realistic.
                      And quite a bit more torque for a b35.

                      They also take more cam- 300 is still streetable, and the 314 in the racecar still idles
                      and pulls (albeit less impressively) from 2k.

                      t
                      who's still on an M54B30 kick
                      now, sometimes I just mess with people. It's more entertaining that way. george graves

                      Comment


                        #56
                        Originally posted by TobyB View Post
                        How is the M30 crank for harmonics? The M10 cranks are fine,
                        but they're 2 pots short.

                        Given that a 150 hp m10 is pretty mild, 225 bhp on a b30 seems pretty realistic.
                        And quite a bit more torque for a b35.

                        They also take more cam- 300 is still streetable, and the 314 in the racecar still idles
                        and pulls (albeit less impressively) from 2k.

                        t
                        who's still on an M54B30 kick
                        my guess itd be no good for high rpm, its a very loooong crank.

                        it has bigger rod bearings so there is a little more overlap in the journals but i think the length is a net downside

                        a 4V engine done properly always makes more topend but for a hot street engine that needs midrange torque the m30 would be pretty good

                        build on strengths i.e. dont go chasing peak hp with the m30
                        89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                        new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

                        Comment


                          #57
                          Originally posted by digger View Post
                          i agree the stock 8:00:1 M30 is a boat anchor mild spec (10.1:1 CR, cam, exhaust) m30 were circa 260bhp and 240lbft in the 80's on motronic. a bit more a rub here and there youd be able to beat that.

                          on the more extreme end i wanna see someone do a 4.0L m30 with RHD ITB, one of his roller rocker and cam combo

                          RHD is doing a roller cam and rockers for M30 now ?
                          Lorin


                          Originally posted by slammin.e28
                          The M30 is God's engine.

                          Comment


                            #58
                            Idk but would not be hard to adapt cam profiles
                            89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                            new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

                            Comment

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