04-20-2016, 02:00 AM | #351 | |
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Per this thread, apparently most aftermarket forged rods will not fit the stock pistons unless they're machined down. Since the motor is already opened, seems like most people just upgrade to forged pistons as well. I believe you can custom order forged pistons and retain the stock 12.5 compression ratio. |
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04-20-2016, 07:12 AM | #352 |
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Give JE a call, they have a 13.5:1 I'm sure they can grind down to 12.5:1 for you.
JE also has a 10.5:1 that looks tasty.
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04-20-2016, 09:39 AM | #353 |
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i just finished mating some bc rods to the stock pistons. light machine work needs to be done. top of the rod needs to be tapered down at a slight angle on each side and an oil shoot on the bottom end of the rod also on each side. cost me about $100... saved me $700 so i added a more efficient intercooler and tranny/shifter parts with the budgeted money. i wont be over 450 hp... maybe 400 to the wheels. i also lowered compression a bit with a thicker head gasket. money well spent? o should i have made new pistons with a 12.5:1 cr?
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04-20-2016, 10:37 PM | #354 | |
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Hint, one of these is on pump gas, the other on e70. Both with the same exact car, same turbo, same everything other than built motor dropping 3 points of compression. This allows not only 5 psi more boost, but also allows more aggressive cam and ignition timings. AFR is the same. Those are turbo journal bearing results. A roots/twin screw can benefit from the higher CR on 93 or alcohol. But on pump most blowers out there right now can be spun down enough to generate more hp/heat then the high compression knock ceiling. So still a good idea to drop a couple points. EDIT for clarity, red lines are LOW compression. Blue lines are stock pistons. Last edited by Xero-Limit; 04-20-2016 at 11:14 PM. |
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04-21-2016, 02:00 AM | #355 |
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04-21-2016, 02:45 AM | #356 | |
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Sent from my SM-G925T using Tapatalk
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04-21-2016, 10:46 AM | #357 | |
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04-21-2016, 01:59 PM | #358 | |
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It was my understanding...
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Jaden |
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04-21-2016, 02:11 PM | #359 | |
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I think it's different for me since I've been sent to the ref previously. I think it's more stringent from here on out, lol.
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The Following User Says Thank You to SPCorBUST For This Useful Post: | CSG Mike (04-21-2016) |
04-21-2016, 02:15 PM | #360 | |
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I had to go to a ref also but not for that...
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So now I carry around the the ref cert with me so if any cops question it I just show them the cert. Jaden |
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04-21-2016, 02:25 PM | #361 | |
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Sent from my SM-G925T using Tapatalk
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04-21-2016, 04:46 PM | #362 |
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@moto-mike or anyone else: I was always under the impression to keep the stock 12.5:1 compression when it came to the Rotrex kits, c30/38. I think I remember reading it some where in the JRSC thread. But if lowering the compression a couple of points for safety has no big detrimental effects on off boost drivability, then it's the way to go it seems like. I'm trying to completely understand the pros and cons.
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04-21-2016, 08:09 PM | #363 | |
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Compression is just one piece of a highly complex system, which results in the horsepower you want. I would recommend you chat with your engine builder and tuner to determine your goal, and then choose the path you want to take to reach that goal. |
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03-26-2018, 01:02 PM | #364 |
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INSANE necro thread revival. I wonder how much our understanding of this has improved? My ostentatious logic says that a large contributor to this is from load on the rods. Turbo tends to pile on low end load quickly, as torque comes in much harder and faster than on most supercharger types people are running on this platform. Also, people who put load on at low RPM (lugging the engine WOT at 2,000RPM) are going to stress the rods a lot more than those who are softer with their input.
Just wanted to open this up for discussion again, as after reading this thread, I feel more success and more failure has been had. Any good experiment's data has a large test pool, right? Too bad we have no control.. |
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kill brain cells, not facts |
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