Quote:
Originally Posted by Lotus7
Regarding the transmission, the US spec. X3 35i uses a ZF GA8HP45Z transmission rated for 331.9 lb./ft. maximum torque. That means a 11% increase in engine torque will exceed its maximum rating. That's why the European X3 35D uses a different transmission, the ZF GA8HP70Z (rated at 516.3 lb/ft of torque) which can tolerate the 464 lbs./ft output of the 35D. The transfer cases and forward drive-shaft clutches are also upgraded for the additional torque (ratings not published). That doesn't mean it will instantly explode if you exceed 331 lbs./ft., but it certainly means you will be driving it harder than it was ever designed to be driven resulting in probable shortened life and more wear.
Let us know how it works, but don't expect any sympathy here (or from BMW) if something breaks.
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Exactly.
Some cars can handle the additional power, some not. A good, modern example is the Mitsubishi Evo X MR with the dual clutch transmission. The "max" torque is easy to beat with simple bolt-ons and some tuning.
Now, if you only use 200 lbs/ft of torque everyday, there would be no problem, but usually, when you mod your car to 400+ lbs/ft, you use all of them daily
The older Evo IX (or the manual transmission one) transmission was able to handle more torque...
There is a reason why BMW delivers the 35i this way :
Beefed up tranny ? More $$$.
Tuning the A/F ratios on the ECU, or raising the boost for more power ? You reduce engine life, possibly less emission compliance.
Then do the same, but put forget internals from the factory so the engine doesn't blow up ? More $$$.
Less restrictive exhaust ? More cabin noise for 95% of buyers.
Bigger brakes ? More $$$.
Modify your car, but understand what you are doing to the whole balance. And then assume if it breaks
