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M20 stroker which cam / fuel pump / ratio

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    M20 stroker which cam / fuel pump / ratio

    Hi

    At this moment I am building an M20 stroker with following setup:

    bottom:
    - original m20b25 housing
    - crank M52B28
    - forged 135mm H beam rods
    - forged mahle pistons bore 85mm with CR 10 to 1
    - RHD flywheel 3,3kg

    this is fully balanced

    top:
    - lightweight Schrick race valves, standard size
    - catcams stronger and shotpeened rocker arms
    - catcams double valve springs
    - catcams lightweight spring seats
    - new ported 885 head
    - camshaft: catcams 285 or schrick 288 (not decided yet)

    inlet: RHD ITB setup 40mm
    exhaust: Hartge headers / Hartge middle muffler without catalyst / Eisenmann race end muffler
    software: full KMS setup incl all sensors, wires, 2 lambda controllers, 300cc injectors, 4 bar fuel pressure regulator etc etc (you can compare it with Link ecu)
    gear box: rebuilt but original getrag 260
    differential: 60% LSD ratio 4.10 (which is to short, I will pas to 3.91 or 3.73, ratio will be decided when engine is running and engine character is known)

    I am having 3 questions:
    - Initally, my car was an M20B20. Will this fuel pump will be efficient enough, knowing I will have a 4 bar fuel pressure regulator?
    I thought M20B25 cars and M3's have 2 fuel pumps, one in the fuel tank and one external. As mine was a B20, I only have a fuel pump in my fuel tank.
    - I have a Catcams 285 camshaft in my possession which drove +- 20k miles. Or I will use this or I will use a new Schrick 288. Any guys who have experience with this? Car will be used for weekend, fun drives and occasional track. I d rather stay save and set my limiter at 7000rpm.
    - Running and LSD with ratio 4.10. I will use this to break in my engine and got familiar with the motor character, as I have no idea which power figure and band I will have. However when I drove the 4.10 with the initial B25 engine, I already decided it was to short. What do you guys think, 3.91, maybe a 3.73.. I do not often use the highway. I use the car for mountain driving and occasionally Nordschleife rounds. (I live in Belgium)

    Want to upload some pictures but it doesn't work.

    Regards,

    #2
    there's a 3.91 med case diff out there if you find the 3.73 too tall. i'm not up on what other 188mm gear sets are available. i'm sure there's several outside of the e30 family.

    Comment


      #3
      You don't say what your rev limit is. For the E30 race cars, a 4.10 gets us to the aero wall with a 7k limit on a '180 hp' motor.
      We use a 4.2x for tracks where you don't get going quite that fast, altho with the stock 'box, ratio matching matters more.

      I come from the M10 world, where a 288 is a street cam. With a 10:1 engine, personally I'd run something with more duration
      (300+) and significant lift (10+mm at the valve) but for street, keep the overlap down. If you're tracking it heavily,
      then let it overlap more. EFI will help it idle ok, and the overlap really gives you a nice boost after 4500, depending
      on how your exhaust scavenges.

      Digger and John will chime in with better advice, of course.

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

      Comment


        #4
        Originally posted by _lestat_ View Post
        Hi

        At this moment I am building an M20 stroker with following setup:

        bottom:
        - original m20b25 housing
        - crank M52B28
        - forged 135mm H beam rods
        - forged mahle pistons bore 85mm with CR 10 to 1
        - RHD flywheel 3,3kg

        this is fully balanced

        top:
        - lightweight Schrick race valves, standard size
        - catcams stronger and shotpeened rocker arms
        - catcams double valve springs
        - catcams lightweight spring seats
        - new ported 885 head
        - camshaft: catcams 285 or schrick 288 (not decided yet)

        inlet: RHD ITB setup 40mm
        exhaust: Hartge headers / Hartge middle muffler without catalyst / Eisenmann race end muffler
        software: full KMS setup incl all sensors, wires, 2 lambda controllers, 300cc injectors, 4 bar fuel pressure regulator etc etc (you can compare it with Link ecu)
        gear box: rebuilt but original getrag 260
        differential: 60% LSD ratio 4.10 (which is to short, I will pas to 3.91 or 3.73, ratio will be decided when engine is running and engine character is known)

        I am having 3 questions:
        - Initally, my car was an M20B20. Will this fuel pump will be efficient enough, knowing I will have a 4 bar fuel pressure regulator?
        I thought M20B25 cars and M3's have 2 fuel pumps, one in the fuel tank and one external. As mine was a B20, I only have a fuel pump in my fuel tank.
        - I have a Catcams 285 camshaft in my possession which drove +- 20k miles. Or I will use this or I will use a new Schrick 288. Any guys who have experience with this? Car will be used for weekend, fun drives and occasional track. I d rather stay save and set my limiter at 7000rpm.
        - Running and LSD with ratio 4.10. I will use this to break in my engine and got familiar with the motor character, as I have no idea which power figure and band I will have. However when I drove the 4.10 with the initial B25 engine, I already decided it was to short. What do you guys think, 3.91, maybe a 3.73.. I do not often use the highway. I use the car for mountain driving and occasionally Nordschleife rounds. (I live in Belgium)

        Want to upload some pictures but it doesn't work.

        Regards,
        - schrick 288 cam as a minimum, perhaps 296 cam. why get catcams uber $$$ rockers and limit to 7000rpm. 7500+ will be fine with correct valve springs
        - single in tank pump is fine, late 320i pump p/n is same P/N as 325i pump
        - 3.73 or 3.91 ratio with standard G260 as the low gears are too short for 4.11. 3.91 ratio with 0.81 5th is fine on highway but may be a bit too much in 1st with a good engine in front
        - host pics on IMGUR
        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


          #5
          Hi Digger

          Is there a large difference between a Schrick 288 or Catcams 285?
          Glad to hear the single tank pump will be sufficient enough. I hope getting the car running again with the new engine around February. Once I feel the engine's character I will decide to go for the 3.73 or 3.91.
          Here some pics before we started the stroker rebuild.
          Discover the magic of the internet at Imgur, a community powered entertainment destination. Lift your spirits with funny jokes, trending memes, entertaining gifs, inspiring stories, viral videos, and so much more.

          Comment


            #6
            Discover the magic of the internet at Imgur, a community powered entertainment destination. Lift your spirits with funny jokes, trending memes, entertaining gifs, inspiring stories, viral videos, and so much more.

            Comment


              #7
              Originally posted by _lestat_ View Post
              Hi Digger

              Is there a large difference between a Schrick 288 or Catcams 285?
              Glad to hear the single tank pump will be sufficient enough. I hope getting the car running again with the new engine around February. Once I feel the engine's character I will decide to go for the 3.73 or 3.91.
              Here some pics before we started the stroker rebuild.
              catcams no longer seem to list 285 on their Belgium website but it is a fair bit smaller than 288. Its been replaced by 291 cam which is fundamentally the same cam as 285 but it is still alot smaller than 288

              at 1mm lift the schrick 288 is like 248 degrees and the catcam285 is 239. At TDC the 288 is like 2.7mm lift and catcams 2.05mm

              need to be careful when comparing catcams to schrick advertised duration mean nothing.

              The catcams 285 use valve lash 0.15mm (updated version 291 changed back to 0.25) and thats probably confuses the situation. As about a decade ago they had a 273 cam that was exactly same lift, same duration at 1mm and lift at TDC as the whats now called a 285 or 291 recent update.

              catcams cams seem to be quite lazy in lowend and midrange response i think it is the slow ramps and lobe center seems to be wider than stated, i would use schrick
              Last edited by digger; 12-19-2021, 03:00 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

              Comment


                #8
                Very clear information, now my latest question concerning this topic and probably hard to tell. Given above setup, at which rpm range should a 288 peak power?

                Comment


                  #9
                  about 7000rpm peak but power will hold on fairly well past that, depends somewhat on some other things e.g. inlet runner length, exhaust primary length, and probably a bit on the head itself as cammed strokers seem to tax the head pretty hard
                  Last edited by digger; 12-19-2021, 04:48 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

                  Comment


                    #10
                    Originally posted by digger View Post

                    - schrick 288 cam as a minimum, perhaps 296 cam. why get catcams uber $$$ rockers and limit to 7000rpm. 7500+ will be fine with correct valve springs
                    Why exactly do you see the 288 cam as the minimum for OPs application?

                    I'm in the process organising a very similar M20 build, with the notable deviations from OP's build-list being 42mm ITBs, IE HD rockers, and new OEM double-springs. Std valves & no head porting planned, partially due to budget. Targeting a 7.2K rev limit. The rest of my parts list is almost identical to OPs. Motor will go into an E30 320i coupe intended for weekend runs, the odd show and shine, maybe some AutoX.

                    I had initially eyed off the 288 Schrick cam for my build, but there wasn't a great level of thought behind that decision besides 'lumpy cam make car go brrrup brrup brrup', and since trying to educate myself a bit more on camshaft spec'ing, I felt the 284/272 Schrick cam would be a better fit for a motor of this spec, where the intended use is ~90% street / ~10% track, as it seems to keep the powerband at a more usable, street-friendly range.

                    However, I've been around long enough to know that your knowledge on this topic far exceeds mine, hence I would love to hear your reasoning on the above comment.

                    Comment


                      #11
                      He didn’t seem to want it for normal street driving duties and with the parts list you’d want to have engine peaking at 7000rpm as it’s easily capable and it better matched to the pulse tuning of the ITB kit with its shorter runners.

                      284/272 and 272 will also work well for much more street based build but it will plateau at the topend more so. A 2.9 with ported head peaks around 6000rpm with 272 but will still make ~230rwhp if the head is done decently well
                      Last edited by digger; 01-20-2022, 02:45 AM.
                      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


                        #12
                        I would like to clarify that if you are using a stock intake manifold it probably does not make sense to use more than a 272 or perhaps a 284/272 on the street especially if you building a 2.9 or smaller engine
                        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


                          #13
                          Cheers for the answer & clarification.

                          Do you have any recommendations for shops around Aus that know how to port a 885 head?
                          Part of the reason I didn't see the point in porting my cyl head is a lack of faith in the very limited number of head shops here in WA, as I fear that money spent may not be worth the end-result (for a predominantly street driven car)....

                          Comment


                            #14
                            Rama is in Sydney
                            Tony from knight engines in Adelaide

                            it’s not cheap to full port a head but depends if you retain standard valves etc
                            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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