Thinking about sequential options

bencb44 · \r\n \r\n \r\n 03-03-2009, 05:14 AM\r\n \r\n \r\n

I have always wanted to redo the sequential system. You know, the idea of eliminating the lag/spool effect of a single turbo is a good one. Anyone who has driven a well-tuned sequential FD knows how nice it is to be able to have linear power that seems to get stronger as the rpm rise. Its a thing of beauty and I have never driven a single turbo car that approached this.

Mazda tried to eliminate the rubber band effect by running 2 different size turbos and spooling the second up to be ready to come on line smoothly. However, its a fairly simple mechanical vacuum-based system. Porsche is doing it by using variable vanes in the turbo. Both systems exhibit the effect of "coming on the cam" when the shift or transition occurs, but they do it very well. But is this the best way to do it? Could it be better? I think so.

I would propose that a system that goes from one turbo (or supercharger) to two (or supercharger and turbo) could be built that could be designed to operate in a variety of ways from linear power to increasing power or whatever curve you wanted.

I would convert the vacuum mechanical system to an electro-mechanical system controlled by one of the aftermarket engine management systems, like Haltech or Motec or Pectel, that offer a lot broader input and out put controls. This would monitor conditions such as TPS, MAP, boost and RPM and certain programmed conditions would control the coming on or going off line of the secondary turbo. It would also control the pre-spool on the second turbo through a variable butterfly style valve connected with the second turbo. This type of system offers several benefits.

Transitions could be made much less abrupt and could occur at different times and under different conditions. You could set the secondary to come on as soon as it was sufficiently spooled up and overlap the two longer in terms of rpm. You could prevent the second turbo from coming on in a corner at all, if you wanted, by reading the side loading in a corner via a sensor. As long as the outside of the car was loaded at least "so much" (defined), the secondary turbo wouldn't come on or would be on but not as pre-spooled, so as to be ready for full throttle on exit, which would over-ride the rule. You could control the primary well, especially if it were a supercharger/turbo hybrid, during cornering, and still have the full thrust available on the straights.

Anyway, I thought I'd stick this out there and see what people think or may have done with this.

Gordon

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