What Shift Points?

[Boost231]

Just wondering how you determin what RPM the motor should be shifted at. Lets say its a

109
.30 over
212/212 cam
max ported irons
Turbo around a 6152
billet caps
arp bolts throughout
ptc converter

was thinking around 5500-5800

but how does one come to this #? also whats the max safe RPM

 

[Boost231]

o also, stock rockers with HD shafts

 

[stagemonster]

On a dyno you could see where the car starts to lose power and then you would know when to shift the car. I would think that is the best way.

 

[brian]

Just wondering how you determin what RPM the motor should be shifted at. Lets say its a

109
.30 over
212/212 cam
max ported irons
Turbo around a 6152
billet caps
arp bolts throughout
ptc converter

was thinking around 5500-5800

but how does one come to this #? also whats the max safe RPM

I would keep it around 5600 myself.

 

[bison]

The best way to check for the optimum shift point is by data logging g-force and analyzing the average g-force near your projected shift point. The shift point will change with the power thrown into the converter and the engines ability to make power at higher rpm with high boost. So id estimate with 20-22 psi 5300-5400. Around 25 about 5500 and about 5800-5900 @30psi. This is assuming you have supporting parts like enough valve spring and the backpressure wasnt getting to high. You will need a converter re-stall if you decide to go from 20 psi to 25+. If not you are leaving a lot on the table.

 

[HOT ROD-GN]

o also, stock rockers with HD shafts

Ijust dyno my son car this past weekend and we made 600hr at 58rpm-605 at59rpm! stock block stock rocker!

 

[HOT ROD-GN]

Just wondering how you determin what RPM the motor should be shifted at. Lets say its a

109
.30 over
212/212 cam
max ported irons
Turbo around a 6152
billet caps
arp bolts throughout
ptc converter

was thinking around 5500-5800

but how does one come to this #? also whats the max safe RPM

your combo i'll say betwin 56-58rpm depend on your v-spring to?

 

[87GN_70GS]

The answer is in the attached graph - it's for a 5-speed but same principle. The plot is of driveshaft torque vs. driveshaft rpm (or speed) for every gear. Ds torque is just engine torque (measured from a dyno) times gear ratio. Ds rpm is engine rpm divided by gear ratio. When the ds torque of the previous gear falls below that of the next highest gear, a shift at that point will result in the maximum torque being transmitted for the run. In other words, shift where they cross. When they don't cross, shift at the safe rpm limit for the engine. Might want to allow some for torque convertor slipppage.