Technical > Spud Miller's Cave

Reducing boost - reduce fuel?

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Dunc the Funk:
Currently we run our blower just 3% over, 33 teeth on the crank & 32 on the blower. This gives us about 15psi of boost. I want to reduce the power for a newbie driver (me) and I have a 26 tooth pulley. If I put that on the crank & the 33 on the blower that's 20% underdriven. I will also put the timing to 30 or even 28 degrees & add more wing angle. Should I take a guess at taking some fuel out of it or leave the tune alone then lean it if I have to?

wideopen231:
3% equals .010 in fuel was rule of thumb Gorr told me and never seemed to fail me.

Paul New:
I have taken a ton of HP from my car just by changing the timing from 30 to 24

Dunc the Funk:
Belated thanks for responses, I'm getting round to tweaking it today ready for next week. I've paid my RWYB entry so I'm committed now!

The '7.5' tune I have now calculates to total jet area = 0.0242in2 & the bypass is 0.0177in2 (150 pill). This is burning the plug ground strap plating but no more.

Looking at those figures I don't understand the .010 per 3%?

wideopen231:
 3% on blower od was same as changing main .010. More blower was same as changine main to bigger jet by .010. Now this was on a 13 gpm to motor system running 14-71 at 5- to 60% OD.

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