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Thread: Ultra Light 2.2L m10 Turbo Build

  1. #51
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    Well I can see where this build is headed....much cutting edge M10 knowledge to be explored, subscribed. Thank you for sharing!
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  2. #52
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    Still waiting to hear back from a few cam grinders. TEP recommends their standard turbo cam which is 274 intake/278 exhaust with 10mm lift on both, with 110 lobe center. I also asked about their SS valves and dual spring combo. Update pricing is $233 for the combo which is very good. I'm considering this over the oe replacement intervalves brand valves and my old "HD" springs.

    Since I don't have enough good info to make a decision on cam yet, I'll move on to my turbo debacle. I had a Garrett journal bearing T25 from an s13 Nissan Silvia SR20det (very similar to the GT2554 in size/spec), freshly rebuilt. I was pushing this turbo to the limit and it's too small for the 2.2L, so I planned to upgrade to a journal bearing T28 from an S14 SR20 (basically the same as the GT2560). I bought a "good used" turbo for $250 off of Zilvia.net. It had a bent blade on the compressor so I was going to have it re-balanced anyway, so figured why not rebuild it while I had it apart.





    When I went to remove the turbine shaft, I couldn't get it out. Figured it was seized so I pressed it out with a 3 jaw pulley and ... ball bearings scattered on the table. This means I actually had a GT2560, so I just ruined an otherwise good (tight and free spinning) ball bearing turbo that I could have just had balanced and ran.

    http://forums.bimmerforums.com/forum...light=cxracing

    I found that only a few shops sell rebuild kits for ball bearing turbos for around $295. Origins of their replacement cartridge is unknown, but likely knockoff.

    Pure Turbos

    The problem is that when you press the shaft out of a BB turbo, the inner bearing race stays pressed on to the shaft, and the cartridge is not easily pressed out of the housing. The exhaust side hole is a smaller diameter than the cartridge, so both jobs require special tools. In light of this, I emailed pure turbos they will rebuild the CHRA for $450.
















    I also called ATPturbo.com and asked about the Garrett core exchange for the CHRA (including wheels). For $457, I can have a completely NEW and balanced CHRA with new wheels, and just slap my freshly bead blasted housings on and go. I have part number 466541-3001 which doesn't exist according to Garrett's system, but I think that the 466541-5001 GT2860 CHRA is the same thing and will work. This makes the aftermarket rebuilt a moot point.

    So for my "new" garret ball bearing turbo will cost a total of $700. At that price point, I begin to question the turbo selection. The great thing about the journal bearing T28 for my build was that it was supposed to be a cheap and rebuildable, with the trade-off beign the exhaust housing is restrictive and will ultimately limit horse power potential. It is now neither cheap nor rebuildable, so why compromise on selection?

    A new GT2860 or GT2871 would be ideal for this build, with the 2871 offering room for any future upgrades I would care to throw at this motor, but spending that kind of money for a genuine is out of the budget, so I'm considering a chinacharger in lue of rebuilding my junked gt2560.

    I'm surprised at the lack of chinachargers on ebay. I can get a "Godspeed" GT2871 for $300 shipped, not seeing much else out there. Surprisingly, I can't find a classic GT2860 knockoff on ebay. Perhaps my ebay is broken?

    Jeff Ciesielski, I'm curious to see your input on this one.
    Last edited by jrcook320; 03-21-2013 at 08:05 AM.

    '81 320i turbo | t25, 931 CIS, 240hp, 13.92@100mph | 2.2L m10 Turbo Build | My E21 Videos |

  3. #53
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    I think your assessment is correct, for a 2.2, something closer to a 2860 or 2871 would be a bit better suited. Also, yes, they are a bit harder to find on ebay for some strange reason. I've found the best way to weed them out is to just search "gt28" and sorting them out by wheel and housing size. Looks like there are some on ebay right now closer to the $200 range.

    If you decide to go that route, just make sure you use a restrictor in the oil feed. Its a bit counterintuitive, but for whatever reason the chinese journal bearings just dont like full oil pressure and they tend to end up smoking. Alternatively, you could go with something like the godspeed gt3076 http://www.ebay.com/itm/NEW-GODSPEED...c05595&vxp=mtr.

    IIRC, it falls somewhere in between a 'real' gt2871 and a gt3071. I'm not sure how much power you're trying to make, but either of those would comfortably make ~350whp, with the 3076 giving you enough headroom to get closer to 400-450whp.

  4. #54
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    For now I'm staying with CIS. The engine build has scope creeped far past any planned budget. This means that I'm building a bottom end and head that will take whatever upgrades I throw at it for the next 20 years, but my turbo selection now needs to be appropriate for fuel system capability.

    I'm likely to still be limited to around 250 hp (perhaps 12-13 psi) unless I find a few more k-jet tricks to try out. Regardless of fuel system, I want strong midrange torque by 3000 rpm pulling hard all the way to 7k. So, I'll be running lower boost than before and really this power level is a perfect match for the GT2560, offering good response and low threshold.

    I'm not remotely interested in a journal bearing churbo. What's the point? I can buy a genuine t28 gtir/s14 hydbid for slightly more and have a journal bearing turbo that will flow more than the gt2860. I'm currently leaning away from a chinese turbo when I can have genuine garrett BB for a few hundred more. I just don't trust the quality yet.

    '81 320i turbo | t25, 931 CIS, 240hp, 13.92@100mph | 2.2L m10 Turbo Build | My E21 Videos |

  5. #55
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    Quote Originally Posted by jrcook320 View Post
    The rings are 1x1.2x2.8 mm. This is a REALLY thin ring set to run on the street, particularly for boost. The thinner ring causes less drag and helps the top ring seal better at high rpm, however it also makes the ring weaker. From what I've read, rings this thin on a boost application are ideally made from steel rather than ductile iron for strength.

    While the idea of not needing to run larger ring gaps for the boost with a gapless top ring is appealing on a boosted motor, the T3583XX is a gapless 2nd ring set. This theory doesn't make sense to me. I think it would make the potential for pressure buildup between 1st and 2ng ring high, particularly on a turbo motor. This pressure buildup can cause top ring flutter and ring unseating at high RPM.

    I'd rather run a gapless top ring and standard second ring since the top ring typically does a majority of the sealing and current ring theory suggests that 80-90% of what the second ring does is oil control. Many engine builders and some ring manufacturers including Speed Pro now recommend running larger second ring gaps to prevent pressure buildup between the top and 2nd rings. This theory suggests a total seal top and standard 2nd ring is ideal, however I have concern about a ductile iron ring this thin for boost. I'd have to contact Total seal directly as I can't find this part number (M3583XX) available for sale anywhere currently.

    So, I'm currently leaning toward the JE, it's cheaper and made of higher quality, stronger materials and seems it will hold up to higher boost levels better.
    Wow Josh you sure have done alot of homework.

    These are the same rings (Total Seal) I have in my M20 1.0 1.2 2.8. The second ring is the "gapless" ring.
    I also question this but never followed through with a call to Total seal's tech line, But I belive it is becouse the 2 peice gapless ring needs more than the 1 mm.

    I think this is a Cosworth ring pack.
    I have 60K on this engine now and 3% leakage.

    These are thin rings and they are file to fit.

    Looks like fun in Josh's garage!!

    Jeff
    Last edited by JDB; 03-21-2013 at 09:51 AM.

  6. #56
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    I was so focused on growing my mullet out I forgot about this thread. So now I'm going to sprinkle my $.02 on everything at once...

    Quote Originally Posted by jrcook320 View Post
    I'm currently leaning away from a chinese turbo when I can have genuine garrett BB for a few hundred more. I just don't trust the quality yet.
    With all this effort and political capital (and money) invested, I would not even consider a chinacharger. I'd spend the bux and put the best turbo on it you can. If this thing takes a dump it can ruin the engine, not anything I'd ever take a chance on. I know you know this, just hoping to give you a "boost" here. haha see what I did there....

    Quote Originally Posted by jrcook320 View Post
    I've never seen bearing failure quite like this. It was almost like delamination of the babbit material from the substrate. Not sure why or when it happened, it was only on 2 rod bearings. There was no rod knock and the crank was perfect. cell phone pics:
    I'd guess that happened on the over-rev. Think of the vacuum pulled at 9krpm with the throttle blade closed. Also according to many close to top fuel drag race engines, they commonly blow up the same way. Here is what I'm told. For durability they run a heavy piston and ring package, so heavy that the aluminum connecting rods they use aren't strong enough to hold them at 8krpm. The only reason they ever stay together is because the blower is pushing air/fuel in so hard that it's pushing the pistons down so the rods are always in compression. If the throttle closes quickly/blower belt flies off/etc the engine will scatter most times. May sound far fetched, but this explanation comes from a source VERY close to this type of racing.

    Quote Originally Posted by jrcook320 View Post

    The rings are 1x1.2x2.8 mm. This is a REALLY thin ring set to run on the street, particularly for boost. The thinner ring causes less drag and helps the top ring seal better at high rpm, however it also makes the ring weaker. From what I've read, rings this thin on a boost application are ideally made from steel rather than ductile iron for strength.

    While the idea of not needing to run larger ring gaps for the boost with a gapless top ring is appealing on a boosted motor, the T3583XX is a gapless 2nd ring set. This theory doesn't make sense to me. I think it would make the potential for pressure buildup between 1st and 2ng ring high, particularly on a turbo motor. This pressure buildup can cause top ring flutter and ring unseating at high RPM.

    So, I'm currently leaning toward the JE, it's cheaper and made of higher quality, stronger materials and seems it will hold up to higher boost levels better.
    Thin rings are a sexy thing in engine building these days. Heck even I climbed out of the stone age on both my 383s with Mahle pistons and 1.5/1.5/3mm ring packages. I know thin rings are worth power, I'd look into the rings the OEMs are using on turbo apps. I'd look at the twin turbo BMW 6s and Fords Ecoboost V6 which appears at this point to be bulletproof. You are also right to steer clear of a gapless 2nd ring. It WILL unseat the top ring. Many drag engines don't even use 2nd rings anymore, I know Ron doesn't. I'm not advocating that for your app, but simply pointing as proof to not run a gapless 2nd ring.

    Quote Originally Posted by jrcook320 View Post
    And, of course I'll clean up the port job. It's OK, but I'd like a better short side radius and smoother bowls.
    Be gentle on short side radius. Without seeing the heads or putting them on a flow bench I only offer this as a tip for the intake ports. Smoothing the radius is probably OK but don't lower the floor or cut into the bowl too far. You probably already know this so it's just a tip. You should load it up and come over here when you're done and we'll put it on the flowbench. Bring a stock head with you and we can compare...

    Quote Originally Posted by jrcook320 View Post
    What engine was the straight 6? It sounds like this was due to harmonics more than balancing. Did he run a harmonic balancer? Was it a wild build that pushed it outside of stock limitations (weight, revs, etc that would change the harmonics or make it run through a natural frequency that it otherwise wouldn't have)? Did he balance with the balancer bolted on? A forged crank 4 cylinder will have very different harmonics than a long cranked straight 6 and usually doesn't need a harmonic balancer. The m10/s14 doesn't.

    Also, keep in mind these cranks (and stock rods) are forged and are extremely robust in stock form. A stock 2.0 m10 bottom end (rods and crank) is said to hold ~500hp before there are any issues.
    I'm well aware that you're dealing with good parts, especially compared to the junk that comes in the stuff I play with. Ron had the crank bending issues with the inline 6, but remember this is one of the new 4.2L GM inlines I think they have 7 main bearings and the main caps are 6 bolt mains(cross bolted), and this was a custom crank. We're talking about 600+ NA hp. I'm not saying you'll have the same issue at all, just a caution about balance. I certainly don't know everything about balancing, I promise I'll talk to Ron tomorrow. I keep forgetting to ask him about balancing when I see him then remember when I'm home. As I said I'll report what he says. This guy has made his own cranks, he even balances his cams....
    Last edited by TKO383; 03-21-2013 at 10:13 PM. Reason: typos
    '86 IROC-Z Camaro 383/TKO600/C4 IRS

  7. #57
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    Quote Originally Posted by TKO383 View Post
    the blower is pushing air/fuel in so hard that it's pushing the pistons down so the rods are always in tension.
    can you explain this. it would seem to me that the rods would be in compression.
    Tom D

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  8. #58
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    Quote Originally Posted by TKO383 View Post
    With all this effort and political capital (and money) invested, I would not even consider a chinacharger. I'd spend the bux and put the best turbo on it you can. If this thing takes a dump it can ruin the engine, not anything I'd ever take a chance on. I know you know this, just hoping to give you a "boost" here. haha see what I did there....
    Many many tens (if not hundreds) of thousands of miles logged on chinachargers by turbo miata guys, no issues as long as you follow the rules . I've personally seen more garrett CHRAs fail outright than I have chinese turbos, but it takes time to convince people I suppose .

    (Note that for the record, I'm not in any way arguing that a modern BW/Holset/GTX isn't superior, but the idea that a chinese turbo is going to randomly explode and kill your engine is absurd)

  9. #59
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    based on the crap toys, tools, hardware, steel, etc. that I see coming out of china what makes the turbos so different?
    Tom D

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  10. #60
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    Quote Originally Posted by Tom D View Post
    based on the crap toys, tools, hardware, steel, etc. that I see coming out of china what makes the turbos so different?
    That's a large blanket statement and I personally know people running eBay turbos with great success. I would just say if you get one, make sure it's balanced properly.
    -Christo-
    >1983 320i, K-Jet turbo, Eurometric poly, Ground control coil overs, Koni yellows, rear sway, full camber/toe adjustment, Ireland Engineering, LSD. 15x7 OZ Alpina reps, 205/50/r15 Kumho Ecsta XS
    >1986 325es, RB20det, Poly rear everything, e46 front control arms, rear camber/toe adjustment, 17x9 STR, BC Coils, 250whp 2300lbs w/o driver

  11. #61
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    Quote Originally Posted by Tom D View Post
    can you explain this. it would seem to me that the rods would be in compression.
    Just a plain typo on my part. Thanks for catching it. I fixed it in my post.

    Quote Originally Posted by JeffCiesielski View Post
    Many many tens (if not hundreds) of thousands of miles logged on chinachargers by turbo miata guys, no issues as long as you follow the rules . I've personally seen more garrett CHRAs fail outright than I have chinese turbos, but it takes time to convince people I suppose .

    (Note that for the record, I'm not in any way arguing that a modern BW/Holset/GTX isn't superior, but the idea that a chinese turbo is going to randomly explode and kill your engine is absurd)
    Well it certainly sounds like you have seen more of them in action than I have. The last time I looked into them with any seriousness people were still finding them with plain bushings, out of balance and incorrect clearances out of the box. Understand however thats from the domestic hotrod side of the fence. These guys I'm referring to are buying 78mm turbos and larger. In that world if it's not Garrett, Turbonetics, Precision Turbo, etc. you aint chit. The smaller copies may be much better, I never run into them. However we all know a turbo is a precision device, not something I'd normally be willing to trust to an offshore manufacturer. Can we split the difference and go with a Master Power?
    '86 IROC-Z Camaro 383/TKO600/C4 IRS

  12. #62
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    http://www.ebay.com/itm/Garrett-GT28...f80575&vxp=mtr

    might wanna watch this see what you can pick it up for!

  13. #63
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    Quote Originally Posted by Christo19 View Post
    That's a large blanket statement and I personally know people running eBay turbos with great success. I would just say if you get one, make sure it's balanced properly.
    I've personally use a Harbor Freight hammer with great success. Then other times the head just flies off. A friend of mine bought a "garret" turbo on ebay. After a short while it crapped out so he took it in for a rebuild. Come to find out, garret parts don't actually fit it, despite having "garret" cast into the housing.

    If I were trying to blow up a stock motor with boost, sure I'd use a chinese turbo. Josh has a big investment into this thing though, and I agree it's not the time to save a few bucks.

  14. #64
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    Quote Originally Posted by jrcook320 View Post
    For now I'm staying with CIS. The engine build has scope creeped far past any planned budget. This means that I'm building a bottom end and head that will take whatever upgrades I throw at it for the next 20 years, but my turbo selection now needs to be appropriate for fuel system capability.

    I'm likely to still be limited to around 250 hp (perhaps 12-13 psi) unless I find a few more k-jet tricks to try out. Regardless of fuel system, I want strong midrange torque by 3000 rpm pulling hard all the way to 7k. So, I'll be running lower boost than before and really this power level is a perfect match for the GT2560, offering good response and low threshold.

    I'm not remotely interested in a journal bearing churbo. What's the point? I can buy a genuine t28 gtir/s14 hydbid for slightly more and have a journal bearing turbo that will flow more than the gt2860. I'm currently leaning away from a chinese turbo when I can have genuine garrett BB for a few hundred more. I just don't trust the quality yet.
    More K-Jet tricks?
    Ever ponder on a 8 port distributor and two injectors per cylinder with a mix of 2.0 and 1.8 head and intake parts? I don't know it it would fit, but if it did you could be open to more tricks
    Tbd

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    Quote Originally Posted by epmedia View Post
    More K-Jet tricks?
    Ever ponder on a 8 port distributor and two injectors per cylinder with a mix of 2.0 and 1.8 head and intake parts? I don't know it it would fit, but if it did you could be open to more tricks
    That would be hard to control at idle I bet. Need a progressive setup where only one injector works at idle/cruise and the second kicks in when more fuel is needed.

  16. #66
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    Quote Originally Posted by Layne View Post
    That would be hard to control at idle I bet. Need a progressive setup where only one injector works at idle/cruise and the second kicks in when more fuel is needed.
    Yes it would be tricky and is probably a silly idea.
    Maybe better use of second injector set for water/meth injection system?
    And again, I don't even know if two sets of injectors would fit, could be a cool experiment though
    Tbd

  17. #67
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    Quote Originally Posted by epmedia View Post
    More K-Jet tricks?
    Ever ponder on a 8 port distributor and two injectors per cylinder with a mix of 2.0 and 1.8 head and intake parts? I don't know it it would fit, but if it did you could be open to more tricks
    It's been done, though that's not the type of modification I was referring to. I'm thinking higher system pressure, and higher control pressures to limit sensor plate travel (thus prevent max travel), richer mixture setting to help compensate for higher control pressure (along with the higher system pressure), and altering the .1 psi pressure differential between top and bottom FD chambers to further increase FD flow capacity.

    Quote Originally Posted by Layne View Post
    That would be hard to control at idle I bet. Need a progressive setup where only one injector works at idle/cruise and the second kicks in when more fuel is needed.
    This could be accomplished by using injectors with different pop-off pressures. Stock injectors in one set and the MB injectors in the other. There would still be a point where fuel flow nearly doubles. I don't think it would be necessary, the injectors would simply barely squirt at idle. It would be the equivalent of a 4.0L v8 idling at 400 rpm vs. 800 in terms of fuel/air flow. Less air flow means lower sensor plate lift and subsequently less fuel. The injectors are still able to spray the correctly metered amount of fuel.
    Last edited by jrcook320; 03-22-2013 at 08:15 PM.

    '81 320i turbo | t25, 931 CIS, 240hp, 13.92@100mph | 2.2L m10 Turbo Build | My E21 Videos |

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    ...so back on the balance issue.

    any inline crank with rod journals 180* apart will balance the same wether it has bobweights on it or not. This goes for 4cyl, 6cyl, anything inline. This is not new news, I'm simply clearing up something I cast doubt on earlier.

    Here is the problem however. The counterweights on the crank need to somewhat closely match the weight of the rod and piston assembly. If they don't, that is where the bending moments on the crank start causing a problem. In other words, the rotating assembly can be balanced, because all the rods and pistons weigh the same, heck you could have a crank balanced with no counterweights at all. But if the crank doesnt have a counterweight near the same weight as the rod and piston, it can't counteract the acceleration and deceleration of the rod and piston. At high rpm a rod and piston can exert in the neighborhood of 12000lbs on the crank(obviously rpm and rod/piston weight dependent). If the crank doesnt have a counter weight to counteract this, the crank can deflect and break, or a harmful harmonic resonance can break the crank.

    So Josh, in this application, you're probably fine, I doubt your counterweights have been cut own to the point that they are tons lighter than the rods and pistons. If you feel like lots of measuring you could model your counterweights in CAD and estimate their weight. I'd say given your rpm and power level you're probably fine with the crank you plan to use.


    The final piece of info I'll share is that a lighter weight rotating assembly may or may not translate into a faster car. I debated this back and fourth today with the wizard and it became the classic debate of engineering/physics vs real world testing don't always shake hands. Basically the only way to make a car quicker is by reducing the rotating weight of the heaviest component radically(wheels, flywheel,etc) or reduce the weight of something that must dramatically accelerate to very high rpm (drum/sun shell in an automatic trans). The wizard cited me some great examples of a Super Stock '70 Cutlass that he works on. The thing has a 10ft long driveshaft and he spent big dollars on an aluminum one. The guy swapped 'shafts back and fourth multiple times at multiple tracks in different weather and didnt even realize .01sec. It essentially made no difference in the car at all. On the other hand, when they rebuilt the TH400 trans for the same car, Ron made a bunch of aluminum drums and such for the trans. One of the drums in question must go from dead stop in 1st gear to 6krpm at the 1-2 upshift, then the same drum has to completely change directions on the 2-3 upshift(6krpm ccw to 6krpm cw). After the trans overhaul with light parts the ET dropped .3sec. He also cited another instance where one of the guys that dominates Comp Eliminator with a 4cyl runs a crank that weights nearly 60 lbs. Apparently he's found that the added weight helps the car pull up off a gear change in a drag race and it's actually faster with the increased weight than it is with a fully lightened setup. I pointed out that this car could be a turd coming off a corner and the wizard agreed, but the point was that getting a car to pull up off a gear change could be accomplished 2 ways.

    Moral of the story is, lightening a crank really only makes the car rev fast and sound cool. It isn't likely to help the car pull up off of a gear change or off a corner because the crank is a low percentage of total rotating weight and it realy isn't accelerating that quickly. You'd be much better off to drop a couple pounds off each wheel and brake assembly. Now obviously if you add up all the weight reduction of rotating assembly, clutch, driveshaft, wheels, brakes etc, you'd probably get a substantial gain, but again, it's all about reducing the TOTAL rotating weight of the whole drivetrain by a significant percentage. In the world we live in, the crank alone doesn't constitute a significant percentage of TOTAL rotating weight.

    I don't think I made any major revelations to the educated among us here, but hopefully this has been a worthwhile addition to making this build thread well rounded.
    '86 IROC-Z Camaro 383/TKO600/C4 IRS

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    You'd be much better off to drop a couple pounds off each wheel and brake assembly. Now obviously if you add up all the weight reduction of rotating assembly, clutch, driveshaft, wheels, brakes etc, you'd probably get a substantial gain, but again, it's all about reducing the TOTAL rotating weight of the whole drivetrain by a significant percentage. In the world we live in, the crank alone doesn't constitute a significant percentage of TOTAL rotating weight.
    Another thing to consider is that crankshafts and driveshafts are a smaller diameter than flywheels and tires. Smaller diameter = less moment of inertia. So let's say an M10 crankshaft is 30lbs and the flywheel is 20lbs (just guessing on these numbers)... the flywheel is lighter than the crankshaft but it probably still takes more energy to spin up than the crankshaft does. I=mr^2 and all that.

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    Super Stock guys can sure drop a ton of money for a .3 second gain. But winning ain't cheap. Nice write up.

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    Thanks for the input Jeremy. We'll see how this thing balances out. I still have 2 counterweights per piston, and I'll be dropping .8 lbs off per piston/rod assembly.

    As already stated, it's not about reduced mass, but about the moment of inertia. I know you know this. Each object will have a different equation to estimate moment of inertia (I) based on its shape and axis of rotation (flat disc, solid shaft, annular cylinder). A 30 lb crank will have a much lower moment of inertia than a 30 lb flywheel. A 30 lb driveshaft would have an even lower moment of inertia. As such, any reduction in mass due to material change would yield a relatively small change in MOI.

    The rate of acceleration change for a given input torque is directly related to moment of inertia, however:

    T=I*a

    Where "a" = angular acceleration, I = moment of inertia, and T= Torque

    A crank's MOI would be most accurately estimated if modeled in solidworks. No "off the shelf" equation will come close. Nevertheless, this topic is beyond the scope of this discussion to get real answers. There are many other factors, including the weight of the vehicle, gear ratios, tire diameters, etc that would affect the rate of acceleration of a crank shaft or driveshaft. The greater the rate of acceleration or MOI of any drivetrain component, the more energy it takes to accelerate it. Likewise, the greater the velocity, the more kinetic energy is stored. Thus, the greatest equivalent HP gain would be realized in first gear with reduced MOI of total engine rotating assembly. The flywheel is the single largest source of stored energy due to MOI, so changes here would be most readily observed. Crankshaft and reciprocating mass of the engine would be secondary to this. A change in MOI of the driveshaft would be negligible. The rate of acceleration would 1/3 to 1/5 that of the crank/flywheel (what's your first gear ratio again?), so changes in MOI would be least observable in real world performance. Change one variable, such as vehicle weight, final drive, wheel diameter, etc, the net effect of all the others will be change since the rate of acceleration will change of each component also changes.

    I enjoy these mind expanding discussions, it keeps me on my toes. They make doctors for this type of thing. I haven't studied this stuff since school...

    Anyway, I agree that the crank in itself will not offer a significant increase in acceleration due to a reduced moment of inertia, particularly when compared to the effect of flywheel MOI, or the MOI of the wheels. I think with the hp level I'm seeing and the lightweight nature of this chassis compared to, say, a '68 impala, reduction in MOI of the crank will be much more effective than it would be on a larger car.

    I also think there will be a greater gain due to the lighter pistons/rods than the crank itself. Perhaps we'll never know.

    '81 320i turbo | t25, 931 CIS, 240hp, 13.92@100mph | 2.2L m10 Turbo Build | My E21 Videos |

  22. #72
    Join Date
    Oct 2004
    Location
    Ohio
    Posts
    6,763
    My Cars
    E21 320i, e39 540i/6
    A quick photo update:







    Gearing up to have the crank ground and the block machined.

    Next is the head. I have some port clean up to do and a few parts to buy. I'm planning to run TEP's SS valves and dual spring combo.

    I still need to select a cam grind. I"m not satisfied with TEP's logic or supporting data (ie: none) for their turbo grind. I've yet to see any other "turbo" cam with a split duration to "help spool the turbo". I'll likely go with a standard 278 or 284, whatever I can find with the most lift. I'm debating whether I take the head to a well respected local shop or a BMW specialty shop. Memphis Motorworks comes highly recommended by Brett at Koala Motorsports.

    I'm also still on the lookout for a turbo - either a GT2560, GT2860, or a Nissan Gtir journal bearing t28 (slightly larger than a GT2860).

    '81 320i turbo | t25, 931 CIS, 240hp, 13.92@100mph | 2.2L m10 Turbo Build | My E21 Videos |

  23. #73
    Join Date
    Apr 2004
    Location
    Boston
    Posts
    7,444
    My Cars
    1979 323i BMW. 2003 GTI 20 V Turbo
    Josh I got a real Garret 2871R for my 20V turbo engine that I am building for my GTI. I am stroking a 1.8t to 2.1 liters. Not sure if that is too big for you, but it cost me a lot more than $300. I have got a hybrid turbo off ebay K04-001 for the GTI in the meantime, but I have no faith in the Chinese built turbos. I would recommend for you the Garrett disco potato 2860 which is very popular in the Vw world. I believe the 2871R or the T3/T4 combo and Holset turbo off the turbo diesel truck are just plain too big for what you are building. The forced induction section of the vortex has the 2860 and other turbos for sale....

    Very informative build, as usual. I enjoy your threads. I will running my new 3.0 engine soon in the 323i, but someday I will build either an S50 turbo, or M20 turbo for my 323i. We need to perfect the e30 center chop into the e21 subframe! Thats so you can push over 300 hp to the wheels with you mad turboed M10 engine. I am inviting out to the Bav Auto show where out cars can shine together!
    Last edited by jjgbmw323; 05-24-2013 at 05:41 AM.
    "..Horsepower is a measure of work done over time, or the rate at which work is done."




    http://www.cardomain.com/ride/579694/1


  24. #74
    Join Date
    Oct 2004
    Location
    Ohio
    Posts
    6,763
    My Cars
    E21 320i, e39 540i/6
    I haven't touched this thing in months. I'm getting ready to take the block and rotating assembly to the machine shop this weekend. I did a little clean up on the block> I removed some un-used bosses, as well as cleaned up some rough edges in the crank case to improve oil shedding (or.. do nothing at all):





    and started working on cleaning the ports up again. I still have some light finish work to do before the final polish.







    I'm also getting ready to make a final decision on a cam. I'm leaning toward the Elgin 284 because it seems to have the highest lift for the duration at 8.23 mm cam lift (10.69mm valve lift).
    Last edited by jrcook320; 07-04-2013 at 10:53 PM.

    '81 320i turbo | t25, 931 CIS, 240hp, 13.92@100mph | 2.2L m10 Turbo Build | My E21 Videos |

  25. #75
    Join Date
    Nov 2005
    Location
    Mills River, NC
    Posts
    3,958
    My Cars
    '82 E21 320i
    Quick question: Why dual valve springs for this build?
    Thanks!
    Eric P.

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