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Old 01-30-2013, 12:12 AM   #1
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Default Crankshaft question

Just testing the waters here, but I'm friends with a few people that race with the bp05 engine. I was just informed that some use the BP01 (90-94 protege 1.8l sohc) crankshaft because its lighter and stronger (still have yet to verify). Does anyone know anything about this? I'm trying to piece together a major build and found a place i could pick up a used crank for around $100, but i want more info than just work of mouth.

Or is my 97 crank better?
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Old 01-30-2013, 12:26 AM   #2
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I doubt you will find any laboratory-grade data on whether the crankshaft from a Protege is stronger or weaker than the crankshaft from a '94-'05 Miata. I can, however, offer one empirical datapoint: the stock Miata crank is not a typical failure point. Rods frequently bend, pistons occasionally split, but even among the folks running 400+ HP, crankshaft failures in the Miata engine (other than damage to the crank nose owing to improper pulley installation) occur about as frequently as potluck dinners jointly hosted by Greenpeace and the Nuclear Regulatory Commission.
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Old 01-30-2013, 01:12 AM   #3
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Protege sohc crank is indeed lighter( cast rather than forged) however, I doubt it's stronger that being said, I tried to find examples of it breaking and have yet to see an instance. So I'd trust it for your average turbo build.

I actually have one that I am planning to add a light weight flywheel too with some beefy rods, not sure if I want to do the pistons. I feel the lighter rotating mass could make a very free revving motor, assuming it can still idle.
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Old 01-30-2013, 01:16 AM   #4
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If Savington can run 350whp or more through a stock crank for a season on track, you will be just fine.
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Old 01-30-2013, 01:17 AM   #5
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thank you both for the info. so i guess it would be a bad idea for my 400-500 long term build. Iantboyd, please let me know via the BG group how it runs, i am really curious how the bp motor runs with super light rotating mass.
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Old 01-30-2013, 01:18 AM   #6
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im not worried about the stock crank at all really. I just heard that the BP01 is lighter, which pegged my curiousity
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Old 01-30-2013, 01:27 AM   #7
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Quote:
Originally Posted by Jemiata View Post
thank you both for the info. so i guess it would be a bad idea for my 400-500 long term build. Iantboyd, please let me know via the BG group how it runs, i am really curious how the bp motor runs with super light rotating mass.
Will do. Probably won't happen for awhile though. Currently installing a Gtr motor in my protege 4wd and building a motor that can max out a hx-35 (~62lbs/min).

I'd like to pick up a cheap mx3 or miata to put the cast crank motor into, run something small (if mx3 probably stock ihi stuff)
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