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Old 03-01-2013, 04:26 AM   #81 (permalink)
Gasoline Fumes
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CRXFi - '88 Honda CRX XFi

Insight 256 - '00 Honda Insight
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Gen-1 Insights

Insight 5342 (no IMA) - '00 Honda Insight
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Quote:
Originally Posted by NeilBlanchard View Post
It would seem to be difficult to rework the way a combustion chamber is designed to work. They engineered it for a particular swirl and a certain flame spread, etc, and to change this after the fact would seem problematic. If you disable one intake valve or the other, and one exhaust valve or the other, you have a profound effect on the mixing and flow. In other words, the valve sizes and their placement and the shape of the chamber and the placement of the spark plug, that would have been better if it was designed for a 2 valve or a 3 valve to begin with, are very hard to get from a 4 valve design.

Also, the fuel metering and the intake and exhaust tracts are all designed for the flow through the 4 valves. It's hard to change any design, unless you can change all the things that are involved.

I see you've come to basically this same conclusion - it makes sense to me.
The 8-valve CRX HF combustion chamber is the same as the 16-valve chamber. Or at least very similar. My valvetrain is virtually identical to the HF. But you're right, the ports, manifolds and throttle body are no longer optimum.


Quote:
Originally Posted by renault_megane_dci View Post
Usually, cam lobes are made to lift the valve a quarter of its diameter.
I assume the 8V variant from Honda has bigger valves so the lobes are taller.
The valves are the same size and have the same part number. Only the springs are different. I can fully compress the 8-valve springs with my thumb.

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2000 Honda Insight
2000 Honda Insight
2000 Honda Insight
2006 Honda Insight (parts car)
1988 Honda CRXFi
1994 Geo Metro

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