Thread: gas hog
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Old 04-15-2011, 11:26 AM   #27 (permalink)
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Join Date: Apr 2011
Location: CA & OR
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Hexd - '93 Honda DX Hatchback
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Originally Posted by bestclimb View Post
you likely know about the 20/22r head swap. I forget which way does what but one is a nice little compression bump. I think if you have the 20 block and 22r head.
In spite of the 22's oversized intake ports they actually flow LESS than the 20's~ due to to early and not-so-effective swirl-port design attempts. The 22's more desirable bathtub chambers and the fact most are fittind w/EFI are their only redeeming qualities. The downside to the 20's are an open (round) chamber design, which creates less combustion chamber swirl resulting in reduced fuel atomization. On the definite upside is their smaller ports, which increase atomization due to the air moving faster. The fix(es)? Extensive welding/reshaping on the 22 head's ports; on the 20's you're looking at a mild port job to clean up, match gaskets, and improve bowl shape just under the valve head, then modifying the intake side to accept the EFI manifold. The head swap you're referring to opens a whole new can of worms in the area of deck height (the distance between crankshaft centerline & haed surface); the 20 has a shorter deck than the 22~ so now we have an additional hurdle to get the timing chain the right length. I believe someone out there is now making the changeover timing set~ bit it's to put the lower compression 20 head onto the 22's block. A lot of work going in the wrong direction! That's why we're all here~ to MINIMIZE fuel consumption. It's a matter of physics~ it takes a given amount of fuel to feed a given size chamber (bore/stroke), to move a given weight object (car), overcoming aerodynamic forces in the process. So I'm opting for the SMALLEST motor practicable to get the job done. That's what makes turbos so attractive; they're load and altitude compensating~ and have little negative impact on economy. In fact they can indeed sometimes IMPROVE fuel mileage....

So to make a short story long~ I'm hoping to find a 20r motor for now...
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