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I am entering my 3rd year of doing DEs.
My car is a 2003 996 3.6L NA, 6 speed MT
I have watched my videos, and my shift points are frequently at too low of rpm, generally around 5200 rpm
My dyno sheet shows torques being level from 4200 rpm to 6200 rpm, then small drop from 6200 rpm to 7000 rpm.
Am I even correct in assuming shift points should be relevant to torque or do you want MPH as quickly as possible?
I am entering my 3rd year of doing DEs.
My car is a 2003 996 3.6L NA, 6 speed MT
I have watched my videos, and my shift points are frequently at too low of rpm, generally around 5200 rpm
My dyno sheet shows torques being level from 4200 rpm to 6200 rpm, then small drop from 6200 rpm to 7000 rpm.
Am I even correct in assuming shift points should be relevant to torque or do you want MPH as quickly as possible?
I don't know where your red-line is but I don't see why you would not be shifting at about 7200. Power is power. At 5200 you are not even getting to peak power. Yes, easier on the motor, but slower overall.
Am I even correct in assuming shift points should be relevant to torque or do you want MPH as quickly as possible?
You are not.
More power is more power and looking at the first chart, you can see that it's gaining power right up to redline.
So you shift right before the limiter. Two things happen here.
Firstly, you're using all the power available. Secondly, when you shift, you're landing higher in the RPM range in the next gear so you're at a higher level of power there as well.
Torque numbers are important only in as much as they contribute to the power numbers. There are engines where the torque drops off at higher RPM's enough for the power number to drop as well. In that case, there might be an argument for shifting earlier, but that comes down to what RPM the shift lands you at in the next gear and what power is being made there.
More power is more power and looking at the first chart, you can see that it's gaining power right up to redline.
So you shift right before the limiter. Two things happen here.
Firstly, you're using all the power available. Secondly, when you shift, you're landing higher in the RPM range in the next gear so you're at a higher level of power there as well.
Torque numbers are important only in as much as they contribute to the power numbers. There are engines where the torque drops off at higher RPM's enough for the power number to drop as well. In that case, there might be an argument for shifting earlier, but that comes down to what RPM the shift lands you at in the next gear and what power is being made there.
That's not the case here. Shift at redline.
+1
Good post!
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More power is more power and looking at the first chart, you can see that it's gaining power right up to redline.
So you shift right before the limiter. Two things happen here.
Firstly, you're using all the power available. Secondly, when you shift, you're landing higher in the RPM range in the next gear so you're at a higher level of power there as well.
Torque numbers are important only in as much as they contribute to the power numbers. There are engines where the torque drops off at higher RPM's enough for the power number to drop as well. In that case, there might be an argument for shifting earlier, but that comes down to what RPM the shift lands you at in the next gear and what power is being made there.
That's not the case here. Shift at redline.
That makes a lot of sense
So that could be one reason why my shifts sound so horrible on video, I can hear the drop in RPM lost, and it sounds like Grandma is shifting.
Each time I go back and read your post about the torque and horsepower drop referring to the moment the next gear is engaged, is because the RPMs are not high enough in the power band, I think, is that what you are saying?
All the responses have been pretty right on, with one that needs a little clarificaiton.
Originally Posted by Wild Weasel
You are not.
More power is more power and looking at the first chart, you can see that it's gaining power right up to redline.
So you shift right before the limiter. Two things happen here.
Firstly, you're using all the power available. Secondly, when you shift, you're landing higher in the RPM range in the next gear so you're at a higher level of power there as well.
Torque numbers are important only in as much as they contribute to the power numbers. There are engines where the torque drops off at higher RPM's enough for the power number to drop as well. In that case, there might be an argument for shifting earlier, but that comes down to what RPM the shift lands you at in the next gear and what power is being made there.
That's not the case here. Shift at redline.
Yes, you want to use as much of the available power as possible. one fine tuning point of what you said, is that most HP curves fall off... that is never a reason for wanting to shift before that happens, ONLY if the post shift RPM point is as high or higher, which usually is not the case. redline is the most optimal point in most cases, especiallly with higher RPM cars. (redline above 6800RPM)
Originally Posted by Thundermoose
Not much to add to what has been said, but gear box is torque multiplier so almost always get more acceleration by running it out to redline.
True, it is, but for this discussion and those like it, think of the gear box as a HP optimizer. if it was just only "a torque multiplyer" then the OP would be correct in shifting where ever he wanted on the "flat torque" curve, which clearly is not the case. So it is both.. it multplies torque, and it alows for optimization of HP
Originally Posted by NYoutftr
That makes a lot of sense
So that could be one reason why my shifts sound so horrible on video, I can hear the drop in RPM lost, and it sounds like Grandma is shifting.
Each time I go back and read your post about the torque and horsepower drop referring to the moment the next gear is engaged, is because the RPMs are not high enough in the power band, I think, is that what you are saying?
yes, the more average HP you have , the more HP you can apply to accelerating the car. the "flat hp curve" is really meaningless. you want a flat HP curve if anything.
All the responses have been pretty right on, with one that needs a little clarificaiton.Yes, you want to use as much of the available power as possible. one fine tuning point of what you said, is that most HP curves fall off... that is never a reason for wanting to shift before that happens, ONLY if the post shift RPM point is as high or higher, which usually is not the case. redline is the most optimal point in most cases, especiallly with higher RPM cars. (redline above 6800RPM)True, it is, but for this discussion and those like it, think of the gear box as a HP optimizer. if it was just only "a torque multiplyer" then the OP would be correct in shifting where ever he wanted on the "flat torque" curve, which clearly is not the case. So it is both.. it multplies torque, and it alows for optimization of HPyes, the more average HP you have , the more HP you can apply to accelerating the car. the "flat hp curve" is really meaningless. you want a flat HP curve if anything.
You and I are aligned on hp vs torque, but to keep it simple applied torque (especially with flat torque curve) is always higher in lower gear so you still want to be in lowest gear as long as possible I.e to redline .
As others have said, to get the most out of the engine and the absolute lowest laptimes, yes shift at redline every-time you can.
... But ...
To get the most life out of the engine, shift below redline. And there is a pretty good compromise here for DE. Shifting 2-300 RPM lower than redline can add substantial life to the engine (so I'm told), while really not impacting laptime too much (proven).
Each time I go back and read your post about the torque and horsepower drop referring to the moment the next gear is engaged, is because the RPMs are not high enough in the power band, I think, is that what you are saying?
Power is torque multiplied by RPM. You want power. You get it from torque, but rpm is just as important. So it's not that rpm's are "in the power band". They define the power band. But being at low RPM's means you're lower in the power band and as you can see from your chart, power is rising right until the redline. So in this case, lower rpm = less power.
Originally Posted by mark kibort
All the responses have been pretty right on, with one that needs a little clarificaiton.
Yes, you want to use as much of the available power as possible. one fine tuning point of what you said, is that most HP curves fall off... that is never a reason for wanting to shift before that happens, ONLY if the post shift RPM point is as high or higher, which usually is not the case. redline is the most optimal point in most cases, especiallly with higher RPM cars. (redline above 6800RPM)
I just want to note that I didn't mean that you'd want to shift if the power started to fall off. I just meant that you'd have some analysis to do, as you mentioned. Basically, in this case there's nothing further to look at but in other cases there may be but you're right... you generally still hold it to redline. Forced induction can make this a more valid discussion though as they can really fall flat on the high end but make gobs of power in the mid-range. That's a discussion for another day and another dyno graph though.
You and I are aligned on hp vs torque, but to keep it simple applied torque (especially with flat torque curve) is always higher in lower gear so you still want to be in lowest gear as long as possible I.e to redline .
yes we are. the flatter the torque curve, the more you NEED to shift higher in the RPM where it is falling off. flatter torque curve means rising HP curve .
Originally Posted by jscott82
As others have said, to get the most out of the engine and the absolute lowest laptimes, yes shift at redline every-time you can.
... But ...
To get the most life out of the engine, shift below redline. And there is a pretty good compromise here for DE. Shifting 2-300 RPM lower than redline can add substantial life to the engine (so I'm told), while really not impacting laptime too much (proven).
yep, thats also somewhat correct. Most cases, a couple of hundred rpm can make the engine last a bit longer as the forces and stresses go up with engine speed, but generally, and personally, i havent seen that to be a problem (redline vs 300rpm short shifting)
Originally Posted by Wild Weasel
Power is torque multiplied by RPM. You want power. You get it from torque, but rpm is just as important. So it's not that rpm's are "in the power band". They define the power band. But being at low RPM's means you're lower in the power band and as you can see from your chart, power is rising right until the redline. So in this case, lower rpm = less power.
I just want to note that I didn't mean that you'd want to shift if the power started to fall off. I just meant that you'd have some analysis to do, as you mentioned. Basically, in this case there's nothing further to look at but in other cases there may be but you're right... you generally still hold it to redline. Forced induction can make this a more valid discussion though as they can really fall flat on the high end but make gobs of power in the mid-range. That's a discussion for another day and another dyno graph though.
yes, even forced induction, to a greater extent, has more power up top. even though they can fill in the low spots in the mid RPM ranges, PEAK hp is still up top in the RPM range. the ONLY time you would want to short shift , is when the post shift RPM HP level is greater than the redline level. (And some averaging of HP can be done to really get an accurate shift point )
Here is an example of when a short shift is warranted.
Last edited by mark kibort; 01-19-2018 at 07:26 PM.
As others have said, to get the most out of the engine and the absolute lowest laptimes, yes shift at redline every-time you can.
... But ...
To get the most life out of the engine, shift below redline. And there is a pretty good compromise here for DE. Shifting 2-300 RPM lower than redline can add substantial life to the engine (so I'm told), while really not impacting laptime too much (proven).
Yeah... there's definitely something to be said for being nice to your car. It's not a race. It probably doesn't make much difference... but you want to maintain a good relationship with your car. She'll treat you better for it.
Originally Posted by mark kibort
yes, even forced induction, to a greater extent, has more power up top. even though they can fill in the low spots in the mid RPM ranges, PEAK hp is still up top in the RPM range. the ONLY time you would want to short shift , is when the post shift RPM HP level is greater than the redline level.
Those dyno graphs with rpm drop indicators, are they calculated or actual from a data logger?
This rpm data from shifting, I can see is a great tool, once a driver has figured out to get everything out of an entire car, ie., the ability to drive 10/10.
That for me is too far away to even contemplate, but was really interested in how racers and pros determine their shift points. Santa brought an Ecliptech sequential shift light for me, so know I just need to figure out what to program it to tell me
Good info on shift points one simple thing I would like to add is do you have a shift light inside your car? It has helped a number of my DE students who worry about over reveing the street car engine. With multiple pills or adjustments built in you can set light at revs you want as a shift point adds confidence to not over reving and no need to look at tach or hit rev limiter.
Rich
01-18-2018, 01:41 PM
What are correct shift points ?
