Would port matching my Skunk2 to FlatTop lose power? - Page 5 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 03-05-2016, 10:44 PM   #81
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Oh, so the very top end was killed by the "step" of a non portmatched IM.

I didn't realize it was that big of a difference. That's huge.
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Old 03-05-2016, 10:58 PM   #82
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VD?
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Old 03-05-2016, 11:03 PM   #83
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Old 03-05-2016, 11:16 PM   #84
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With barometric stability velocity attraction correction dynamics.
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Old 03-06-2016, 02:43 AM   #85
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Ok, there is no way that's the correct plot... I was looking back at the pre and post skunk 2 plots back on page 3, and neither one of them take a nose dive... something must have been wrong with that pull?

The only reason I care is SCIENCE
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Old 03-06-2016, 02:57 AM   #86
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I dunno, you made it, so...
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Old 03-06-2016, 01:58 PM   #87
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Nice gains, but looking at the throat of the square top, I thought it would be a smoother transition. I'd love to see a comparo between flat top and a 99 with the throat cutout and re-welded
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Old 03-06-2016, 10:48 PM   #88
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There isn't enough wall thickness to take much material out of the "throat" It's hard to see from the pictures.

I purposely stayed "shallow" with the portmatching, because I wanted to minimize potential ill effects.
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Old 03-07-2016, 02:55 AM   #89
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Similar to a 3 angle cut on a valve, or a rear diffuser, the air can flow over around a 15 degree change in angle smoothly, but any more and it separates and start to form a turbulent zone. As long as there is a smooth transition that's not super radical you'll pick up 90% of the airflow gains from removing the step. You could port is better to get that last 10% but it's hardly worth it for a stock motor.

So step vs no step was a 2-5hp difference? Not bad actually considering the engine isn't limited by the throttle body and it's such a simple job to do. The same mod on an engine that needs more air, like a stroker or a ported head with big valve and the difference would be double that.
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Old 03-07-2016, 06:11 AM   #90
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You've still got plenty of meat to take off - here's my efforts for comparison:



I wasn't game enough to take any more off between 12 and 2 but everywhere else I've still got plenty of material left.
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Old 03-07-2016, 10:19 AM   #91
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/\ that looks super smooth, good job.

I think ours turned out even better than the pictures show, somehow the pictures make it look more rough than it actually was. Overall it was a time consuming and messy job, but not hard at all.

and yeah he made sure to make the transition smooth. I was holding the thing down, OP was grinding
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Old 03-07-2016, 11:49 AM   #92
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Quote:
Originally Posted by 18psi View Post
this is corrected with temp/baro
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Old 03-07-2016, 09:49 PM   #93
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Inspired by this we're going to include a same day A/B test between the matched squaretop and Skunk TB tomorrow while we're dynoing some prototype Supermiata cams. The ported IM was on Deviate when we made 300whp with the Rotrex.
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Old 03-07-2016, 10:30 PM   #94
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Old 03-07-2016, 11:57 PM   #95
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Yay! I was going to do this myself, but the engine is a few weeks away from being completed.
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