Originally Posted by Chilicharger665
How much power are you two aiming to make? The engines can easily be built to take the power, but I am worried about the transmissions and rear ends. Who has pushed those limits in NC's and how high have they gone?
I'm aiming for 350whp+ on the stock 2.0L, 6spd and factory LSD.
There are a significant number of boosted NC's over on M.Net. Essentially all of them (outside of some REALLY high end fab work) are kits, rather than the DIY'ers we find here on MT.
The NC1 (2006-2008) engines use powder cast / sintered rods which are, at least technically, inferior to the "powder forged" parts in the NC2 and later (2009++). While there's no specific proof of this, the NC1's did have a reasonably well documented problem with rod knock issues, even when left completely stock. I'm not sure if Mazda ever fully fessed up to that challenge, but the internals changed in 2009 and those problems seemed to go away. Part of the parts change was in relation to the raised redline in the NC2 and later models; Mazda's own marketing crapola in 2009 specifically talked about "the engine was fortified with a new forged steel crankshaft, forged steel connecting rods with floating wrist pins, revised pistons with stronger wrist pin bosses, stiffer valve springs, and an oil cooler"
Take that for whatever you think it's worth
Both motors are easily good to 300whp; there are a number of NC2 turbo folks running beyond 350whp for multiple tens of thousands of miles, including cars that are raced regularly at both HPDE and various autox events. The general consensus seems to be 350tq is about where you want to stop, the highest HP number I've seen reported over a LONG duration (thirty thousand miles) on stock internals is ~380whp as reported from a dynojet.
Also keep in mind the OEM computer on the NC's is soft, fine putty in the hands of a proper tuner. I'm not aware of ANYONE who is running aftermarket ECU, including a 211whp N/A 2.0L custom uber-compression, uber-cam, ITB and E85 build, nor the "big HP" fully built lower compression boosted 2.0L and 2.5L swaps. Strap on a 3bar MAP sensor and a set of 1000cc injectors and you can do insane things on the stock computer equipment. Hell, there's a guy over there running a >300WHP roots blower on E85 on the stock ECU
Originally Posted by sixshooter
I heard the NC 5speeds are stronger than the 6speeds. Any truth to that?
Nope. The 5spd are the weaker transmissions of the two. Further, the NC1 version of the 6spd had problems with bending the 3/4 shift fork (rectified in the NC2) and also a challenge with >300TQ applied in 6th resulting in shearing the teeth from the gear.
The NC2 Asin transmission is absolutely stronger in the shift fork area, and is purportedly (not necessarily proven) stronger across the various gears to include 6th. A (small) number of owners with failed NC1 6spd transmissions swap up to the NC2 and, again purportedly, have good luck there.
Finally, I'm not aware of anyone shredding the stock rear end, even when swapping for a taller ratio (3.7:1 is the tallest ring and pinion set I've seen.) The factory LSD in the NC is a clutched type, so eventually I assume they will burn up. Still haven't actually seen it yet. If/when it happens, there's plenty of aftermarket options, with Quaife being one of the more popular.