RPM related changes and HP implications

08-31-2003, 11:58 PM

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Edge

Murphy was an optimist!

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RPM related changes and HP implications

If you've dug into your books, you can see a lot of stuff happens at various RPM ranges. Figured I'd collect it in one place:

Code:

RPM     SYSTEM              WHAT
3750    Fuel Injectors    #2 primary  and secondary injector start
                                      controlled by ECU fuel maps
                                      (All in use during WOT!?!)

3750    SDAIS                #2 primary intake ports open
5500    SDAIS                VFAD may open (Yamaguchi p 115)
6250    SDAIS                Auxilary intake ports open
7250    SDAIS                Primary intake ports interconnnect
                                     adds a second shorter path
7250    SDAIS                VFAD opens on WOT

NOTE: all of the SDAIS changes presume WOT, don't know what happens if it's not WOT. I'd guess the ECU makes the decision.

Please add things I've missed

Now, what does the above imply, how does it compare to driving experience, and how does it relate to observed hp and torque curves. I'm not highly educated on this stuff, so please step in and correct my errors or stupidity.

If you're not WOT, some or all of the above may not happen. I'm not used to just hammering the pedal to the floor, I'm used to putting it down to the point I interpret as max accel for a given RPM. Since this is fly by wire, not putting the pedal to the floor does not tell the computer exactly what I want: max speed now! Kind of like the change from standard brakes to ABS.

I was experiencing stutter/power loss above 6K. My car is now over 3K miles and combined with a new attitude on the throttle, that hesitation is gone. Accel levels off a little around 7K, then picks up again past 7.5K. (all on butt dyno here)

What about the dynos? My observed (butt dyno again) driving experience has some implications for this. Assuming the current dynos are fairly quick pulls, I can see where there will be a fall off above 7K. At about 7250 the VFAD opens (might happen earlier too, but it for sure happens here) and an interconnect between the primaries also opens. I think I observe this as a leveling off around 7000-7500 RPM. After 7500 RPM (or a couple second count), the car seems to get a second wind and pull harder. My guess is it takes a little while for the changes to settle down and actually have good impact. So what?

If a dyno run doesn't allow the engine to settle in above 7500, it may never get the real power from the VFAD and extra cross-connect because it's over too fast. Things happen incredibly fast between 6250 and 9000 in second and third. It'd be interesting to compare runs from third through sixth to see if longer time at high RPMs results in a better curve.

Last edited by Edge; 09-01-2003 at 12:01 AM.

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