hybridmoments

why are you running in CP? gutted interior? lexan windows?

can't believe you need more power with the K20a2. i hate you! HAHA

i think my friend locally makes 230whp with his mild k20 eg hatch. and he is fastest 95% of the time here in DC.
i know he found some speed by running a power steering setup, and a 5 speed trans with Clutch type Lsd instead of the 6 spd.
he said he could not keep up with the steering in tight slaloms. car was too fast with too much grip.

i think there is just going to be a point where the extra power isn't going to help you. especially on tight courses.
then you'll be worrying about engine and IAT's after each run in grid and maybe distracting you from thinking about what to do on your next run.

WRXRacer111

He has a point. You can do the engineering calculations to figure out your natural frequencies, which is great... I encourage you to learn as much as possible and try to figure out what works and why it does. However, tuning for a target natural frequency might better be left for comparing notes between pure racecars of the same type. A typical passenger-based racecar has many more compromises to be fought. ie fighting off bushing deflection, poor suspension geometry not fixable within a ruleset, street car ride etc.

Natural frequencies between say, an STX Subaru and an ST Civic will be totally, totally different. Both cars working "well" for an autocross application on the same type of tire, say a Falken Azenis 615, the STX Subaru will have much higher natural frequencies. You'll end up with way too much spring on the Civic if you try to hit the same natural frequency. So... my point is, use your engineering knowledge to test and set the car up to make it work... but don't get caught up if "what works" doesn't jibe with your equation. Your equation needs to be a lot more complex than one line to capture all of your real-world variables.



That said, I don't think natural frequencies have anything to do with turbo or supercharger selection... but a friend who autocrosses and does rather well at national-level events and is a Garrett turbocharger engineer tends to develop the engine/turbo combination to generate a long, smooth powerband that doesn't spike at any point, and has a significant amount of overrev to reduce the number of gearshifts during a run.

Fabrik8

I know a few racecar vehicle dynamicists who would argue against engineering calculations being worthless. I guarantee that they'd get exponentially closer with much less time and effort than someone who just did trial and error. Of course, they'd probably also say that a street car chassis has way too much compliance and no where near enough torsional rigidity to really behave like it should. Then they'd tell you that the stock suspension geometry is far too compromised to work well for racing too.. So it's all relative.

The engineering calculations you're talking about are very broad calculations, and are not the same calculations that a race engineer would actually do. A car that you can race on multiple tracks, etc., without actually changing anything is not a very well developed race car. If you make some calculations, then do some trial and error, and then keep that setup for more than track, you haven't really optimized or tuned anything.

I forgot where I was actually going with that..

Fabrik8

You're saying that the car was way above his driving ability. That's a refreshing thing to say, and not often heard.

Silverbullet86

equations out of a car dynamics text book seem so impractical to me IMO. A real world car that is driving is just so dynamic. It seems like a headache accommodating for rolling, pitching, weight xfer/tire load changes, suspension geometry changes, yaw changes so on and so on all at the same time.

Fabrik8

So lets ignore them all and pretend they don't matter...?