[somethincreativ]

2LT Z51 7MT.

How quickly are you guys shifting at redline, under full throttle? After playing around with shift speed, and timing, I hit it the other day, wondering how quickly (not hard) I could move my feet and switch gear. The car responded really well, and now I'm wondering what the opinions are of my fellow Stingray enthusiasts. After I move to Nevada in February, I plan on attending the Ron Fellows course. It was something I planned on doing, and the feedback from alumnus on this forum really sealed the deal.

Thanks!

 

[mjw930]

The only time I shift at redline is when I miss the proper shift point. To keep the car in the power band shift a little short of redline, as the torque curve is dropping off. Drag racers have no lift shift but for road racing (track time) keeping the car in the meat of its power band is the key to fast laps.

 

[FormulaRedline]

The only time I shift at redline is when I miss the proper shift point. To keep the car in the power band shift a little short of redline, as the torque curve is dropping off. Drag racers have no lift shift but for road racing (track time) keeping the car in the meat of its power band is the key to fast laps.

Sorry, Mark. I'm going to have to disagree with you here. While what you are saying could be true for certain engine and gearing configurations, that does not appear to be the case for a stock Z51. Take a look at the dyno and gearing map:

According to the dyno graph, the RWHP drops off to about 390 at redline. This is about the same power the car is making at 5k rpm. For your suggestion to make sense, an upshift would need to result in revs higher than 5k. However, look at the blue lines representing the Z51 gearing in the second graph.

Every shift 1st through 5th (and you won't be using 6th or 7th on the track) drops you below 5k rpm, even at redline. If you shift early, you'll be giving away horsepower.

That said, unfortunately banging out laps at redline in this car seems to overheat the engine, so some strategic short-shifting isn't a bad idea for longer sessions.


OP, here's one of my videos from Ron Fellows to illustrate the gear changes. I don't bang them super fast, I try to be a little smoother than I would in my S2000 for example, given the torque that could upset the rear wheels.

 

[mjw930]

I read those charts differently. Assuming shifts just above 6000 but a couple hundred below red line and for all but the 1st to 2nd shift you never fall below 4K which is where the torque drops off. Pulling all the way to 6500 just isn't needed unless you are drag racing and even then it's arguable.

 

[thrilled]

I would have liked to have seen the tach with those shifts.It didn't seem like you were winding it up.Maybe it's just me

 

[somethincreativ]

Thanks Formula. I think we can go ahead and seal up this can of worms.

 

[FormulaRedline]

I read those charts differently. Assuming shifts just above 6000 but a couple hundred below red line and for all but the 1st to 2nd shift you never fall below 4K which is where the torque drops off.

The problem is that you are looking at the torque, which is irrelevant. You need to compare the power output, which is the product of the torque and the engine speed. This is significantly lower at ~4k than ~4.5k.

I would have liked to have seen the tach with those shifts.It didn't seem like you were winding it up.Maybe it's just me

You are correct. I was short shifting a bit to try and keep the engine cool during that session. You can actually hear one of the instructors over the radio in that video asking us to do it.

Here is a session earlier in the day where I was wringing it out. The blue car in front is NASCAR truck driver Erik Jones:

 

[mjw930]

Formula,

To be clear, I was never saying short shift at or below 6000 RPM, I was saying that shifting at say 6300 will net you roughly equivalent lap times vs. 6500 assuming you never bounced the car off the rev limiter. If you bounce the car of the limiter you instantly lose acceleration, which will never happen if you shift just before (or at least initiate the shift as the needle passes 6300).

I will however disagree with you about torque being irrelevant. Torque is actually the only relevant measured force value in this equation. Torque can be measured by the ability to accelerate a known mass. Given an identical torque multiplier (engineering speak for the gear ratios) the car will accelerate at the same rate whether the shift point is 4100 RPM or 4500 RPM since the measured torque the engine is supplying is virtually identical at either RPM. The car's rate of acceleration is the slope of the HP curve, which again, is virtually identical from 4000 to 5000 RPM hence the term "The meat of the power band". BUT, and this is a big but, if you short shift you rob the car of the acceleration rate it can achieve get when using the much higher torque multiplier of the lower gear. If you shift below 6000 RPM the odds are you will fall below 4000 RPM at which point you have hit the flat spot in the LT1's torque curve and have robbed yourself of both the acceleration of the lower gear and the torque needed to accelerate after you shift.

The LT1's rate of torque fall off above 6000 is gradual enough to mean you are probably accelerating harder in the lower gear from 6000 - 6500 RPM than you would in the next higher gear at 4000 - 4500 RPM so your assertion that it's best to get as close to redline as possible is a very solid argument. I only suggest a 6300 RPM shift to make sure you never hit the rev limiter. Not because I'm worried about doing damage but because I wouldn't want the car to pull power when I'm trying to wring every ounce of acceleration out of it.

After all that I think we are both in agreement, run the car out in each gear as much as you can without hitting the rev limiter is one of the tricks to lower lap times.

 

[Snorman]

2LT Z51 7MT.

How quickly are you guys shifting at redline, under full throttle? After playing around with shift speed, and timing, I hit it the other day, wondering how quickly (not hard) I could move my feet and switch gear. The car responded really well, and now I'm wondering what the opinions are of my fellow Stingray enthusiasts. After I move to Nevada in February, I plan on attending the Ron Fellows course. It was something I planned on doing, and the feedback from alumnus on this forum really sealed the deal.

Thanks!

I'm not sure what your track experience is, but you'll find that you don't really need to worry about lightning quick shifts or powershifting the car on a road course. In fact, you'll often find out smooth is faster and you can go just as fast in the next higher gear because you won't be so worried about throttle control. The broad torque curve of the LT1 gives lots of flexibility. Furthermore, you'll find that balancing the car with brake and throttle is VERY important.
Enjoy Spring Mountain! I'd like to fit it in before the 1-year expiration, but my track schedule is very full for the remainder of the year and not sure I can get out there before March.
S.

 

[mjw930]

I'm not sure what your track experience is, but you'll find that you don't really need to worry about lightning quick shifts or powershifting the car on a road course. In fact, you'll often find out smooth is faster and you can go just as fast in the next higher gear because you won't be so worried about throttle control. The broad torque curve of the LT1 gives lots of flexibility. Furthermore, you'll find that balancing the car with brake and throttle is VERY important.
Enjoy Spring Mountain! I'd like to fit it in before the 1-year expiration, but my track schedule is very full for the remainder of the year and not sure I can get out there before March.
S.

That's kind of what I was trying to say but you said it far more eloquently