Quote:
Originally Posted by GT500R
Very odd that your traction is an issue on stock power. Running the stage 1 tune with 36 / 39 psi yesterday on the streets yielded a small hop and then take off with a very acceptable 1.6x 60’
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Actually, it seems quite understandable to me - not sure why it seems ‘very odd’ to you?
Even with just stock power the X3MC has a very good Wt/hp ratio, and on a smooth surface and with DSC off, it makes sense that tires may not grab at higher psi under different road/track conditions. I think I had mentioned in my GNV Raceway thread that it felt just like a belt sander at take-off with little grab back in Nov’19, and in fact, in the pre-lanes while waiting, a number of other Drivers were noticing the same thing with their launch control (even some with slicks), so they were lowering their psi and brake releasing rather than using launch control to improve traction.
When I lowered the psi from 33/38 to 32/35 on my next series of runs in Feb, the 0-60 foot times improved significantly (2.010 sec vs 1.824 sec on average – see attached image), despite a much lower DA and cooler temps (which one would expect to actually hamper traction rather than help it). Nothing else was different, other than a few gal less fuel in Feb (which would’ve made the car lighter if anything). So at least here at GNV Raceway, for my X3MC, it clearly seems to perform better with lower psi settings. I’ll test that hypothesis further the next time out, as I’ll run at 30F/32R then. No doubt there will be a sweet spot for all of us at our various tracks and roads, so what works here may not be applicable to you on your roads. For those interested, here are some links which discuss Coeff friction and track/tire interactions.
“Coefficients of Friction of Various Roadway Surfaces” :
https://marules.com/wp-content/uploa...aySurfaces.pdf
https://www.onallcylinders.com/2016/...icks-traction/
https://www.autoweek.com/racing/nhra...r-a-drag-race/