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I admire the description and writing style, and most of what this article says is accurate. However, I'd like to try to clarify a couple of points. My source for these clarifications is a technical article published in Sport Compact Car magazine in 1999, and also one in Turbo Magazine in 1998 (before it folded). Both articles were written by a Nissan engineer. The statement: "From the factory, the ECU is mapped in an unsafe manner for running boost levels above 12psi or so. It primarily has to do with the ignition timing being too far advanced. " is not accurate. The use of the term 'unsafe manner' is misleading. Ignition timing is not the primary issue here: it's fuel maps, and this is implied in a couple of paragraphs farther down in the article. If one reads this statement out of context, they might think that all they really have to do is change the ignition timing. And one of the 'tricks' that some people recommend is to change the initial engine timing about two degrees to get more power. The point is that the ECU needs retuning in more than one aspect. And the system components have a design point to consider, which I discuss below. The discussion of the knock sensor in more than one paragraph is inaccurate: a very important point is left out. The engine is very noisy above a certain RPM, and the ECU stops listening to the knock sensor at 3,500 RPM due to this noise. Most of the 'lean' conditions that we're discussing here are present at higher RPM, approaching WOT, so the knock sensor isn't working when we may need it most. I'm not sure there's any knock sensor we could install which will protect you at WOT because it's so hard to differentiate the noises the engine makes at that level fast enough to do something about it. The statement: "Safety boost is when the turbochargers will limit manifold pressure to 7psi (down from 9.5psi or whatever your boost jets were making it run). " is misleading, because it ties safety boost to the turbos themselves and to the use of boost jets. The turbos don't limit boost at all - their control mechanisms do. The ECU manages the stock control mechanisms. The ECU 'thinks' of boost in stock terms, while boost jets fool the ECU into thinking the manifold pressure is lower than it really is. This statement should discuss the ECU's management of safety boost in a stock configuration first, then qualify it with the use of boost jets separately, so that it states the situation clearly. The statement: "While remapping of the primary maps is necessary to allow a daily driver to run 16psi of boost safely, the secondary maps must also be addressed properly." assumes you can do this on a daily basis. The stock units simply are not built to handle that level of boost. As said often on this Forum, the stock turbos max out on thermal efficiency around 14 lbs of boost, and the turbo's components aren't built to last at higher levels. If someone runs them at 16 routinely they're not operating in the equipment's safe range, and could damage the turbos and/or the engine. That's a primary reason why Nissan engineers limited boost to the ranges that they did: they knew the limits of their components. Tom Bell
IZCC 2802
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22:00:25 11/12/03
