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Working out the ideal cam switching rpm

Practical Dyno Tuning

Discussion and questions related to the course Practical Dyno Tuning

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I have a sr20vet that has the option to hydraulicly changed to a 2nd cam profile on both the intake and exhaust cam.

Would you do a base run with both off, then one with the intake on and use the rpm where the torque lines cross. Then another run with just the exhaust on to find the exhaust cross over point. Or would you do the exhaust test with the intake cam switching to the 2nd profile.

If you have two states for two variables, you should test all 4 combinations, and look at the graphs all overlaid to determine the combination that produces the best torque at each RPM.

This will work best if you can run closed loop lambda so the mixture stays the same, otherwise you might want to plot Lambda/AFR as well and pay attention to where it goes lean as this would indicate improved VE and could perhaps make even more torque with proper fuel.

Thanks David ill Try that next dyno day.

What vehicle is this and what transmission?

Keep in mind that you could be affecting the boost control as you change. Turbo adds extra complexity.

Gtir pulsar, 5 speed manual. Yes it is turbo i have them both switching at 5000rpm as a starting point until i get on the dyno.

Well... the best way but the most time consuming is to tune all for 4 engines, tune the engine with the 4 cams possibilities and then put the 4 dynosheet and see the best combo of all 4 engines and then tune that one. Is the best way but it take more time ( a lot more). Vtec is easier cause there is just 2 engines to tune. If you tune every engine (4 cams possibilities) then you wil have the best result, if you can take the time and extract as much power as you can for every possible engine and then choose the best combo...