6 speed and auto guys....How to determine shift points
09-26-2006, 08:56 AM
#2
I set my shift points to have the RPMs (after the shift) land where peak torque occurs. This gives the best results for drag racing. If that is not possible, then I set the shift point to be 200-300 rpms above peak horsepower.
09-26-2006, 11:18 AM
#3
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Originally Posted by 12secSS
I set my shift points to have the RPMs (after the shift) land where peak torque occurs. This gives the best results for drag racing. If that is not possible, then I set the shift point to be 200-300 rpms above peak horsepower.
peace
09-26-2006, 02:20 PM
#4
heres just a theory of mine....but what you'd like to have is the best average horsepower during a run. what i mean is you take the dyno graph and a handy dandy rpm/gear ratio/mph calculator and set your shift points to yield the best average horsepower for each shift.
shifting right at the hp peak will generate less average hp used than if you shift after the hp peak. im sure none of this makes sense at all...but think about it this way...shifting sooner will put you lower in the rpm band on the next shift where there is less hp being produced. shifting after the hp peak will make the rpms fall back nearer the hp peak and ideally in an area equal to what power was being produced after the hp peak.
you need to have a dyno graph if you intend to try any of this and a way to average a certain rpm window (exel can work)...otherwise please disregard.
shifting right at the hp peak will generate less average hp used than if you shift after the hp peak. im sure none of this makes sense at all...but think about it this way...shifting sooner will put you lower in the rpm band on the next shift where there is less hp being produced. shifting after the hp peak will make the rpms fall back nearer the hp peak and ideally in an area equal to what power was being produced after the hp peak.
you need to have a dyno graph if you intend to try any of this and a way to average a certain rpm window (exel can work)...otherwise please disregard.
09-26-2006, 04:25 PM
#6
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I think that you need to look at the TQ not the HP.
Each time your tranny makes a gear change your final TQ ratio changes and you lose find drive TQ, that is what moves the car.
You need to multiply the engine TQ against each tranny gear ratio, and then build a spread with a column for each gear.
The idea is to shift at point that will make the smallest reduction in TQ between gear changes.
There was a web site calculator that I use to use.
You would enter you engine TQ for many different RPM’s and the tranny gear ratios and it would calculate the best shift point for you.
Sorry I can’t fine it.
Bob
Each time your tranny makes a gear change your final TQ ratio changes and you lose find drive TQ, that is what moves the car.
You need to multiply the engine TQ against each tranny gear ratio, and then build a spread with a column for each gear.
The idea is to shift at point that will make the smallest reduction in TQ between gear changes.
There was a web site calculator that I use to use.
You would enter you engine TQ for many different RPM’s and the tranny gear ratios and it would calculate the best shift point for you.
Sorry I can’t fine it.
Bob
09-26-2006, 04:58 PM
#7
Originally Posted by 99ssleeper
heres just a theory of mine....but what you'd like to have is the best average horsepower during a run. what i mean is you take the dyno graph and a handy dandy rpm/gear ratio/mph calculator and set your shift points to yield the best average horsepower for each shift.
shifting right at the hp peak will generate less average hp used than if you shift after the hp peak. im sure none of this makes sense at all...but think about it this way...shifting sooner will put you lower in the rpm band on the next shift where there is less hp being produced. shifting after the hp peak will make the rpms fall back nearer the hp peak and ideally in an area equal to what power was being produced after the hp peak.
you need to have a dyno graph if you intend to try any of this and a way to average a certain rpm window (exel can work)...otherwise please disregard.
shifting right at the hp peak will generate less average hp used than if you shift after the hp peak. im sure none of this makes sense at all...but think about it this way...shifting sooner will put you lower in the rpm band on the next shift where there is less hp being produced. shifting after the hp peak will make the rpms fall back nearer the hp peak and ideally in an area equal to what power was being produced after the hp peak.
you need to have a dyno graph if you intend to try any of this and a way to average a certain rpm window (exel can work)...otherwise please disregard.
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09-27-2006, 08:35 AM
#9
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Well my car peaked torque at 5000 and if I shift low enough to let it fall back that low my car doesn't run very good. I picked up 1.5 mph and a pretty good bit on my e.t. just by going from 6500 to 6800. :truestory:
