secondarries - ZR-1 Net Registry Forums

XfireZ51 · 04-05-2013

Hib,

I wonder how much of the "stock motor needs secondaries" conventional wisdom is a result of removal but not addressing the tuning properly. Anecdotally, the problem should be exacerbated by top end porting of an otherwise stock motor.
More air by increasing volume should negatively affect flow velocity on the low end. And that should demonstrate itself as a loss of low end torque.
Perhaps the addition of freer flowing exhaust (re: headers) which tend to accompany other mods, may mitigate the effect of greater volume. How much of the "loss of low end" is SOTP instead of data driven? My own personal experience has been that porting the top end, and having secondaries come on just after idle has increased torque throughout the rpm range and I could post dyno sheets showing that. Most tuners will tune for WOT, but the process of tuning for part throttle is much more time consuming and involved than WOT.
Which is why it's not done. Having looked at calibrations from other tuners, I can tell you that the stock calibration is hardly modified if at all. And in fact, it needs to be modified quite a bit.
So my point is that we can't be sure how much of the low end loss is due to improper tune rather than strictly a result of removing secondaries. Maybe we'll never know.

04-05-2013	#21
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,686	Re: secondarries Hib, I wonder how much of the "stock motor needs secondaries" conventional wisdom is a result of removal but not addressing the tuning properly. Anecdotally, the problem should be exacerbated by top end porting of an otherwise stock motor. More air by increasing volume should negatively affect flow velocity on the low end. And that should demonstrate itself as a loss of low end torque. Perhaps the addition of freer flowing exhaust (re: headers) which tend to accompany other mods, may mitigate the effect of greater volume. How much of the "loss of low end" is SOTP instead of data driven? My own personal experience has been that porting the top end, and having secondaries come on just after idle has increased torque throughout the rpm range and I could post dyno sheets showing that. Most tuners will tune for WOT, but the process of tuning for part throttle is much more time consuming and involved than WOT. Which is why it's not done. Having looked at calibrations from other tuners, I can tell you that the stock calibration is hardly modified if at all. And in fact, it needs to be modified quite a bit. So my point is that we can't be sure how much of the low end loss is due to improper tune rather than strictly a result of removing secondaries. Maybe we'll never know.