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    Bi-Turbo M20 Questions

    So recently I have been looking into doing a turbo setup for my 89 325i with a stock m20b25, as many people do and whilst browsing turbochargers I came across a pair of TD03-08g turbos on cragslist from a Volvo S80 t6 engine, and was wondering if doing a twin turbo setup on a stock m20 is a good idea.

    The engine that they came from is 2.8 liter 6 cylinder engine. My initial thought is that 2 smaller turbos will spool faster, but I assume that also means that they reach full boost at a lower rpm.

    I am fairly new to the world of turbocharging still so I was wondering what your thoughts on this where. What sort of issues do you think I would have with running 2 turbos versus one? Also would I be able to take a y-pipe and join the compressor feeds, or would that put too much strain on the turbos?

    Thanks for your time guys!
    5
    You are out of your mind and should quit now...
    40.00%
    2
    This is a feasible idea... In theory....
    20.00%
    1
    Go for it! It would totally work!
    40.00%
    2

    The poll is expired.


    #2
    Anything works with enough welding rod.

    Cons:
    -Packaging... twice as many turbos to fit
    -Condition of Craigslist turbos... probably wore ass out

    Pros:
    -Lower spool RPM = wider powerband, as the M20 is limited by head flow on the top end
    -Cool factor
    -Increased "I built it myself" satisfaction

    Comment


      #3
      If you want big power (I assume so since you're going turbo) two small turbos is NOT the way to go. Just in terms of efficiency, assuming effective sizes are the same, a single turbo will ALWAYS make more power compared to two small turbos. Have you ever wondered why the Supra guys always do a single conversion?

      Those volvo turbos are probably undersized, even for a 2.5L. I think chipped those S80s made just about 300bhp. In the grand scheme of things, that's not much for a 2.8 twin turbo engine maxing out turbos. You might argue it could be a soft limit because of the GM transmission issues those cars had. In any case, the TD03/TD04HL volvo turbos usually have proprietary manifold flanges, causing a whole 'nother issue with these turbos. You'll be happier with a real T3/T4 flange. Want torque? go supercharged. If you want power, go single.

      Contrary to what the above poster mentions, those watercooled turbos last quite a while without needing to be rebuilt.


      I think that you should begin your reading with something like Corky Bell's Maximum Boost. No offense, but you seem to be missing some fundamentals that you will need if you plan to have a usable turbo setup.
      '84 318i M10B18 147- Safari Beige
      NA: 93whp/90ftlbs, MS2E w/ LC, 2-Step
      Turbo: 221whp/214ftlbs, MS3x flex @ 17psi

      Comment


        #4
        I am not sure about big power, but I am looking for a bit more, but I am on a pretty tight budget, hence why I am looking to see what I can get for as little as possible. (Not a remarkably good idea as far as reliability goes, however I assumed it would be best to buy a used turbo as opposed to the Chinese turbos on ebay) And no I hadn't.... But I haven't really looked at any Supras...

        And agreed the manifold was on the top of my list of concerns. So I guess single turbo is the way I will go. I would like to find a few cars with turbos big enough so I can go to my local Pick-n-Pull and pull it.

        I would like to say I am at least a little above fundamentals level, but that probably means that I am so basic I cant even...

        Comment


          #5
          Tight budget and turbo project don't really go well together just a heads up.

          With that being said hx-35s are the "budget" turbo that people on this forum seem to go with. From what i've read they are a bit laggy but make decent power.
          2.7i Stroker Turbo Build Thread

          90 325i | 95 Miata

          Comment


            #6
            You can do this on a tight budget but you need to have a wise budget. In other words, no twin turbo craziness, be it efficient or not.

            For budget, get an eBay manifold with the wastegate provision, eBay wastegate and bov/intercooler kit, craigslist turbo, just search compressor maps and find one that flows 1.5cfm for every 1 HP you want at the flywheel.

            That should all run you less than 800bucks.
            For another 650, buy a PNP Megasquirt from whodwho on the boards. This is..required. Just do it. Don't do rrfpr please
            You're up to 1400. Get some junkyard 36-42 lb fuel injectors<100bucks
            Buy some used arps or find an eBay deal<200. Metric blues if you have to.
            EBay clutch or something used on the forum <250

            Find some scrap aluminized steel and weld up a 3" downpipe, just let it go to atmo, turbos are good mufflers

            Another 300 for random crap like oil feed and drain, vband connectors, tapping your oil pan, boost temp and oil pressure gauges. Random fittings
            You're looking at around 2g's for a pile of used parts that should stay together since you have standalone management. Should make decent power too. Hopefully you already have an LSD, and suspension, maybe brakes and a rebuilt shifter? Probably some wider tires

            Not to spamm but you could also buy my 400whp m20. Turbo/twinscroll Mani/injectors/oringedblock/arps/42lbers/clutch/intercooler/charge pipes,
            Everything plumbed to fit, bolt in boost. Just still need to hit up keith for the megasquirt.

            m20b27 Turbo. Hx35. Twinscroll Mani. MS1. 42lbers
            http://www.r3vlimited.com/board/showthread.php?t=338818

            Comment


              #7
              Originally posted by dtaivpp View Post
              I am not sure about big power, but I am looking for a bit more, but I am on a pretty tight budget, hence why I am looking to see what I can get for as little as possible.
              Well don't let me deter you, but I think kistler's estimate of ~$2500 is probably about right in terms of a 'bare bones' turbo build that is worth anything. If you want cheap power, NO2 is the best you can get for hp/dollar.
              '84 318i M10B18 147- Safari Beige
              NA: 93whp/90ftlbs, MS2E w/ LC, 2-Step
              Turbo: 221whp/214ftlbs, MS3x flex @ 17psi

              Comment


                #8
                Also I'd like to add that 2500 is pretty cheap for 300-400 HP all said and done. And a pile of used parts isn't really a bad thing as long as you don't buy junk
                Last edited by kistler#7; 12-06-2014, 07:04 PM.

                m20b27 Turbo. Hx35. Twinscroll Mani. MS1. 42lbers
                http://www.r3vlimited.com/board/showthread.php?t=338818

                Comment


                  #9
                  Originally posted by Jaxx_ View Post
                  If you want cheap power, NO2 is the best you can get for hp/dollar.
                  I guess more then cheap power I kind of want sustainable power. True nNO2 is pretty cheap, but I would rather have something I don't have to refill, not to mention I would likely blow up my engine....

                  Originally posted by kistler#7 View Post
                  Also I'd like to add that 2500 is pretty cheap for 300-400 HP all said and done. And a pile of used parts isn't really a bad thing as long as you don't buy junk
                  Curious about the 300-400 hp.... Can the stock headgasket and piston rods even take that much beating? To be honest I was only really planning on getting 210-250 out of this project not that I wouldn't be happy with 300 that is. I will post a projected parts list I guess and see if maybe I can get a more specific estimate. I wish I could just sell my computer to be honest. Then I would have at least 3200 to throw around, which would sure make things a lot easier...

                  Comment


                    #10
                    The headgasket is will hold whatever the bottom end can with studs and an mls or orings. Maybe 300hp with metric blues. The bottom has been proven to 400whp reliably and near 500..unreliably.
                    I leave yourself room to grow on this, boost is addicting and even 250whp will get old quick.
                    if you go with a Megasquirt, ARP studs and a clutch, you almost double what the rest of the package can take, assuming the turbo and injectors are sized right

                    m20b27 Turbo. Hx35. Twinscroll Mani. MS1. 42lbers
                    http://www.r3vlimited.com/board/showthread.php?t=338818

                    Comment

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