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      03-28-2008, 09:39 AM   #17
Suzie's Dad
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Quote:
Originally Posted by Mr.Marvelous View Post
baaah, nothing will happen to the engine with a single chip...
You have more confidence in a young, self-taught computer whiz than I do.

Get ahold of SAE paper 2007-01-1560. It is written by two BMW engineers who were involved in the design of the 35i engine. They talk about the incredible complexity of the software and how software is used to control a large number of engine parameters that have never been controlled before (turbo 'bumping', catalyst 'lighting', and so on). The 50i engine has even more complex software than the 35i.

It used to be that 'chipping' an engine just meant altering the software maps that govern fuel quantity for given throttle, air mass, and speed conditions. Quite a simple thing to do. With turbo engines, it also meant fooling the ECU into allowing a little more boost. There is generally no harm in that, provided the knock sensing is left unaffected. But the BMW TT engines run with a compression ratio in excess of 10:1 and rely on special spark plugs to detect ionization, which is an indicator of ignition. They send a signal to the ECU, which takes appropriate action to avoid engine meltdown.

Many newer 'chip' systems do not alter the OEM software maps, but intercept signals between the ECU and the software bus. They then modify those signals to fool the ECU into doing or allowing things that it would otherwise have restricted. All they are doing is pushing a little more into the safety envelope that the manufacturer builds into his engines so that he doesn't get overwhelmed with warranty claims. The makers claim that the devices can be easily removed (the implication being that you would need to do so for some reason; hmmm...) and that the vehicle manufacturer cannot tell that the device was ever fitted. Personally, I don't think BMW is that stupid.

If you look through somebody like Vishnu's website, you will note that some early customers had 'less than satisfactory' performance gains (I wonder what that means?) and so the Vishnu device was modified. In other words: We would like to thank all those beta testers out there who allowed us to perform long-term reliability testing at their risk rather than ours.

If you are comfortable with the idea of software this complex being modified and bypassed in the name of a few extra horsepower, then be my guest and go ahead and get it done. I'm guessing a replacement 50i engine will run in the $10,000 to $15,000 range. I would far rather you experiment than me! When you have proven the reliability of the modifications (ie: when version 2 starts to become available) I may consider buying one myself.

BTW, some of my comments apply much less to diesels. They already run very high CRs and are less likely to suffer chip-related damage. BMW's diesels do not use turbo bumping, but have one small turbo (for low-speed torque) and one larger one (for high-end power) that operate in series. And guess what, they don't use fancy spark plugs to detect pre-ignition (doh!). The software is proportionately less complex.
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