When to shift/set shift light?

[Paul Workman]

Experimenting a bit, I discovered that my shift light might be set a little high (or maybe my reaction time is waning...NAH!). I got better times shifting closer to 6800 rpm than at 7200 (shift-light setting).

Short story: I came across an article discussing this very topic. Open for discussion: (what the hey...its below zero in my garage and there's snow and salt on the roads! I'm going crazy!)
Anywayz... author - a physics guru - recommended shifting up at the point where the descending engine power in the lower gear is equal to the ascending power in the next higher gear, i.e., maintaining MAX AVERAGE ENGINE POWER** was the drift.

**except in one case where wheel torque after the upshift would result in a reduction of wheel torque in spite of engine torque being higher (due to overdrive gearing, in this case).

The "test mule" in this case is not a ZR-1, but the concepts are transferable, no?

Have a look. (And, in fact I MAYBE do have my shift light set too high...AND NO WISE CRACKS ABOUT OLD AGE AND REACTION TIME!!:censored:)

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[WARP TEN]

I for one would not be one to make cracks about old age or reaction time, although I might say something about low flying pilots... But on the subject, as I recall Marc H always recommended shifting no higher than about 6,500 rpm as that is about where the LT5 engines normally make their peak power. Little advantage to going higher. Maybe he can chime in. --Bob

[32valvesftw]

I don't have a shift light but 6800 seems be about right for me

[Paul Workman]

I for one would not be one to make cracks about old age or reaction time, although I might say something about low flying pilots... But on the subject, as I recall Marc H always recommended shifting no higher than about 6,500 rpm as that is about where the LT5 engines normally make their peak power. Little advantage to going higher. Maybe he can chime in. --Bob

Yours and my "FBI" LT5s peak more closely to 6800...for what it's worth.:)

[Flyman 27]

I drive a Heibeck 500. In a recent email exchange, Mark recommended that I set my shift light at 6700 because of normal/average reaction time. He sets his engines "red line" at 7300. He also said that the stock system "red lines" at 7100.
For what it is worth.

[DRM500RUBYZR-1]

I drive a Heibeck 500. In a recent email exchange, Mark recommended that I set my shift light at 6700 because of normal/average reaction time. He sets his engines "red line" at 7300. He also said that the stock system "red lines" at 7100.
For what it is worth.





Sounds about right, except do not forget to make the RPM adjustments required by the Society of Physiological Ergonomically Triumphant Life Experienced Pragmatic Realistic Racers Of America.


Their theorem, repeatedly proven and loosely stated, suggests subtracting 21.7823869 RPM for every year of attained age beyond 50 years old, excepting for leap years, when you must make an additional deduction 0f 0.0000004357612.


I have found this theorem to work quite well.
Marty

[XfireZ51]

Sounds about right, except do not forget to make the RPM adjustments required by the Society of Physiological Ergonomically Triumphant Life Experienced Pragmatic Realistic Racers Of America.


Their theorem, repeatedly proven and loosely stated, suggests subtracting 21.7823869 RPM for every year of attained age beyond 50 years old, excepting for leap years, when you must make an additional deduction 0f 0.0000004357612.


I have found this theorem to work quite well.
Marty

Marty,

I believe there is a “Hurst shifter” multiplier to take into account. However, in the case of an “older” driver, the shorter shift length is effectively negated by the diminished muscle mass of the elderly.

[DRM500RUBYZR-1]

Marty,

I believe there is a “Hurst shifter” multiplier to take into account. However, in the case of an “older” driver, the shorter shift length is effectively negated by the diminished muscle mass of the elderly.



Indeed! I almost switched back to the longer shifter to gain back the added leverage to compensate.


As a young drag racer, I began to leave upon seeing the last yellow, rather than waiting for green.
As the years have passed, I have moved up a light or two.
Lately, I have been thinking that at the rate things are going, I may soon leave upon the illumination of the "Staged" light.
Marty

[We Gone]

Question??

Did Marc happen to say what he sets the shift light at on his 500 set-up, or does he let it stay stock... If so what is the stock shift light set at?

[Paul Workman]

Question??

Did Marc happen to say what he sets the shift light at on his 500 set-up, or does he let it stay stock... If so what is the stock shift light set at?

Good point: NOT all LT5s are set up the same: stock, vs. top-end porting, vs. FULL porting with and w/o headers, etc., etc.

So, it stands to reason, that part of the puzzle includes the individual dyno graph(s) specific to the particular LT5.

I imagine your dyno graph for Marc's 500 package is similar to my curves (508 hp "FBI package"). HP for my motor is essentially flat from 6500 to 7000.

So, for you and I, we need to consider the gearing/differentials and go from there, no?

I don't recall where the factory "UPSHIFT" is set, but the factory cut-off is (IIRC) 7100ish (for a 90). I had to have Marc change my cut-off rpm to 7600 after I finished the "500" project, b/c I was hitting the RPM cut-off before crossing the finish line in a 1/4 mi drag race.

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[tf95ZR1]

https://www.corvetteforum.com/forums/c4-zr-1-discussion/614357-what-shift-points-for-max-excelleration.html

Thoughts from 2003

[efnfast]

I would think you want to shift a couple hundred after max hp, so you land a couple hundred below. Making your average......max hp.

[Paul Workman]

I would think you want to shift a couple hundred after max hp, so you land a couple hundred below. Making your average......max hp.

The graph is a little "busy", but it bears you out. Essentially, what the graph shows is the "ideal" shift point is where waning engine power before the shift is equal to the ascending engine power after the up shift. Thus the average engine POWER is highest.

My shift light is set at 7100, but no doubt my actual shitfs occur prolly closer to 7300+ by the time I can watch the road and react. So, in order to up-shift closer to 7100, as others have said too, I prolly need to reset the light for 65-68 hundred RPM to allow for reaction time - especially in 1st gear; where things get pretty busy pretty quick!

[efnfast]

Wow, my peak power was about 6700 rpm, so shift at 7, drop to 64 or 65

[We Gone]

Mine is right at 7000rpms also