Tuning Port polishing the 1.1

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Tuning Port polishing the 1.1

Zian

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Apr 6, 2020
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Hi, how much extra power can I expect if I port polish my 1.1 uno's head. If anyone knows can you please tell me the power figures that I can gain.
Thanks!
 
what 1.1 is it? go for piper 270-285 try and get bigger inlet valves and seats cut for more power, ports unless there way to small won,t make much difference unless you are reving the nuts out of it lol
 
I thought the reccomdned way was to remove excess material againt the inlet manifold and remove any steps/ large imperfections but not totally polish w.g leave it in a semi rough finish to encourage fuel air mixture by providing a little turbulence in the cylinder
 
I thought the reccomdned way was to remove excess material againt the inlet manifold and remove any steps/ large imperfections but not totally polish w.g leave it in a semi rough finish to encourage fuel air mixture by providing a little turbulence in the cylinder

:yeahthat:

Matching the ports to the manifold is the first step. Otherwise do not polish the ports at all.
We need the fuel to be mixed with the air as a fine mist, the rough surface causes some turbulence which helps the fuel remain suspended in the air. A smooth polished surface will actually promote condensation, where the fuel drops out of the air and forms droplets in the manifold. The air then has to pick it up again as it re-evaporates, but it will arrive in the cylinder as larger droplets, which burn less efficiently, or not at all, so you use more fuel for less power. Generally liquids do not burn, vapour does, so we need the fuel to stay vapourised.

If I remember correctly, the FIRE engine has quite large valves, they just don't open very far, which makes it a safe engine. To get more air in, the valves need to open further, or be open for longer. This is what the later 1.2 with variable valve timing does, which is why valves and pistons can meet if the belt breaks.

The 1.1 is a more revvy engine than the 1.2. Rev the wotsits off it, with a big grin. Lots of fun, without much risk of breaking laws. The joy of a small engine.
 
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