Quote:
Originally Posted by Mit_Boost
They're clearly tuning to keep TQ down to avoid over stressing the factory rods. And traction is an entirely separate conversation from the engine performance (see a properly set up suspension, tires, etc. etc.).
And I would be concerned about the rods -- We're talking about an NA, high revving motor that was not designed for boost. By adding twin turbos, we're adding lots of low-end TQ that continues across the entire RPM range. Not a direct comparison, but the Porsche 997.1 Turbo (higher strength Mezger motor) stock tunes around 400 WHP/400 WTQ (TQ is what kills rods, so ignore that HP numbers for now). After upgrading everything, you can get into the 900 WHP area, but you cannot go above 700 WTQ safely. So the breaking point on a high performance, high quality, racing derived factory boosted motor is double the WTQ.
The E9x M3 M3 stock dynos around 350 WHP/300 WTQ, but like I said when I started, this motor was never intended/designed to be boosted, and I've be very conscious of going above 500 WTQ on stock rods (if not for my conscious, then in fear of the costs and headaches associated with sourcing a new block when something breaks).
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Agreed, unlike earlier BMW motors that had stronger components in them this high RPM motor has some very light rods that are not that strong, I have seen them bend from poorly tuned supercharger kits. The pistons eventually size and the rods snap in half and people probably assume some of these bent rod failures are rod bearing failures. I have an engine right now that bent 5 out of 8 rods.