Quote:
Originally Posted by img
8600 is really pushing the limits on stock internals. Rods,Valve Springs,Bearings can not take it !
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Quote:
Originally Posted by img
Im just talking from experience of the amount of M3s that ive seen at the dealer with broken valve springs at etc...
Hope all is well  |
Pushing the limits? Most likely not. Is it putting additional stress on everything? definitely! I wish BMW would list the maximum continuous engine speed allowed for the S65 like they used to in the olden days of the S50
Izzy, 200RPM is only a 2% increase in engine speed over the stock redline. I would agree that 8.8k or 9K may be pushing it, but if an engine broke a valve spring from 200RPM over factory redline the design would not have an acceptable safety factor built in to it.
I'd say any broken valve spring, stretched rod or main/rod bearing that has failed on an N/A S65 is most likely from a defective part, substandard machining, the engine has the rev limit excessively raised to say 8.8K or higher, or, the owner overspeeded the engine severely with a mis-shift. I don't think any OEM would risk making anything for series production without at least a 5% (and most likely more like 10%) safety factor engineered into it, especially an engine that can rev to 8.4k out of the box. I wish BMW would
The reason the factory set the redline at 8.4K is because the engine won't make much power above redline on stock cams. turning the engine to 8.6k or 8.8K on stock cams would be a waste of time IMO. I don't think more duration from vanos timing is the answer in making power up high, I think the engine needs higher lift (Maybe porting and larger valves would help a bit too if there is room for improvement there) to shine up top......... Valvesprings would be nice for an added safety factor too!