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Carb mod

 
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mppalmer(at)aol.com
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PostPosted: Thu Jun 08, 2017 12:19 pm    Post subject: Carb mod Reply with quote

I had a chance meeting with a Formula 1 racer. He races in a class where you can only make simple mods to a production engine.

One of the mods he suggested that I try was to 1) smooth the vanes on the venturi in the carb and 2) twist the vanes in the venturi to "swirl" the air.

I couldn't twist our vanes, because we have a one piece venturi. (But you might be able to do it if you kept the 2 piece (Despite the AD.))

But I could smooth out the blunt edge of the vanes. And I smoothed them out asymmetrically, in the hope that I could impart a swirl to the air flow.

So I did.

postimg.org/image/4y84e4csd/

It seemed to me that rounding the leading edge of the vanes on the venturi was a no brainer, in the sense that air in the venturi is probably running at about 100 mph, and those blunt edges had to be making drag, turbulence and a large wake.

I couldn't tell a night/day performance difference after doing the mod. But then, I don't turn the engine at 4000 rpm, like my new-found racer buddy.

Maybe I picked up a half inch of MP. Can't really say.

But I notice that the EGT distributions are more even now and I can lean further than I used to. I can now get down to 6.5 GPH (WOT) at altitude. Whereas before, 7.2. (This is with one mag replaced by an Electron ignition, with advanced timing.) Speed is the same at LOP, which is why I think I might have picked up a half inch MP. (The increase in MP offset the leaner mixture.)

Anyway, it's an easy enough mod to make when you have the carb apart. I can't see a downside. Only an upside.

Mike Palmer <><


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