Thread: Dutch SR20VE dyno'ed - your opinions

yeh i mean the smoother curve is the obvious benefit, but WOW i didn't realiseit could affect peak power...

how's that you any ideas? was that done on same day/dyno run with no other changes just cam switch points? If so thats very interesting stuff

The switching point does not change the peak power.

If you are seeing a change then it was because of other changes and or due to variation between runs.

You can see a 3-5hp difference between a cold and warm engine run.

^ yeh i agree, didn't think so. there's no conceivable reason why it could. must just have been usual inconsistencies between runs

It would occur to me that simply the engine has more pull (inertia?) coming from below with more and faster climbing power.


But that is so BS I cannot believe myself...

I didn't think it would either until we did 2 runs with the same power, twiddled the knob to adjust the switch point and bingo, 3kw gain, which was repated on the next pull.



2 runs, back to back within 15 seconds of each other. No changes other than a twiddle of a knob to change the shift point.



3kw on a 250kw car, sure, and usually power will go DOWN on successive pulls due to heat soak and other things (especially turbo, but of course we're talking n/a), but 3kw on a 106kw car, that's a pretty big inconsistency and a pretty big co-incidence.



I guess that's pretty much how i see it. The momentum of the engine wasn't interrupted by a dip (or a hook because it falls off pretty bad) in the power curve. If i wasn't there, wasn't watching the dyno, the operator etc i wouldn't have beleived it myself.


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If someone else can explain it, then please do.

I repeat, nothing was changed between runs, ONLY the VVL point.

On a day to day basis with a lot of the race engines we build, i see that under hard ramping conditions on the dyno, fatter midrange of torque alwaysd affects top end power. Its especially visable on heaivly boosted engines - such as RB26,Rb28,Rb30 and Rb32 units.



Roatational inertia. For every revolution a certain amount of jules is needed to accelerate the rotating assembly. Ultimately, the more energy you store into the rotating assembly earlier (inertia) the more will be transferred across the crank later on. The best way to describe it is a saturation point of energy needed for each revolution to increase ahead of the other, once the assembly reaches that point, any extra energy is what you will see as your horsepower gain.



Correct, you have the right idea!!

right, ok.

but isn't that a similar effect to having a lighter flywheel etc?

it's not 'actual' power but shows up as it?

or am i being dumb lol....

A flywheel is actuall power.

Any reduction in rotational weight is actual power.

Ennergy is transferred in a simplifed version like this.

Cylinder Combustion(chemical) > Pistons (kinetic) > Rods (kinetic) > Crankshaft (kinetic) > Flywheel (kinetic) > clutch (heat - into friction - end result is kinetic) rest of drivetrain.

At any point where energy is used as kinetic energy, you want the mass to be the lightest possible. Lighter mass means the energy isnt stored as long[we still want to store as much energy as possbile!] ( there are volume mass to energy laws) and the energy can then be trasnferred on to the next part of the chain quicker and easier with minimal time loses.

Our engines work off pulses of energy, so the quicker you can convert the energy from fuel and air into mechanical energy, with the least time of absorbtion inside the rotating mass of the engine - means the more energy actually gets to the wheels.

Interesting stuff here.

Different question. Currently VVL is activated through the VE ECU.
When connecting an MSD 8969, does it intercept signals from the solenoid-wires or do you have to cut them from the VE ECU and hook it up at for example the tacho and ignition from the dash?

Cut the wires that goto the ECU for the VVL.