I'm trying to lower compression in my engine

[humfrz]

Originally Posted by 86kahl

By loosening my spark plugs a couple of turns, how many do u guys usually go? I did two last night and my car sounded mean, like a chopper😁

If you want to lower the compression on your engine, simply remove the piston rings.





humfrz

[themadscientist]

F this, I'm raising my compression. I'ma gonna smear some JB weld through the plug holes onto the piston tops and spin the engine by hand before the stuff dries to form domes. Science, bitch!

[JD001]

Originally Posted by themadscientist

F this, I'm raising my compression. I'ma gonna smear some JB weld through the plug holes onto the piston tops and spin the engine by hand before the stuff dries to form domes. Science, bitch!

Spinning the engine by hand is a great idea as the newly shaped piston heads will softly kiss the valves to get them to match the curvature.

[Tcoat]

Originally Posted by themadscientist

F this, I'm raising my compression. I'ma gonna smear some JB weld through the plug holes onto the piston tops and spin the engine by hand before the stuff dries to form domes. Science, bitch!

Just inject some water. Since water will not compress then it reduces the air space and increases the air compression without creating a hard surface that could get hit.


#bettersciencebitch!

[themadscientist]

Actually, all kidding aside, I'm looking at water/meth injection for the R to stave off detonation.

[Tcoat]

Originally Posted by themadscientist

Actually, all kidding aside, I'm looking at water/meth injection for the R to stave off detonation.

Yep. War Emergency Power has been around a long time.

[themadscientist]

If I recall, that's where they first started injecting nitrousoxide too.

[Tcoat]

Originally Posted by themadscientist

If I recall, that's where they first started injecting nitrousoxide too.

Yes. That was the way the Germans got emergency power in their aircraft. Not sure if the US used it then though.

[HunterGreene]

Originally Posted by Tcoat

Yep. War Emergency Power has been around a long time.

Ok, possibly dumb question, but what is the purpose of the scoop on the bottom of that plane? First answer is engine cooling, but placing it that far back seems unnecessarily complex.

[xmadror]

at least with the frs you'll only replace tires and not the hood !

[Tcoat]

Originally Posted by HunterGreene

Ok, possibly dumb question, but what is the purpose of the scoop on the bottom of that plane? First answer is engine cooling, but placing it that far back seems unnecessarily complex.

It is cooling. It is back there for aerodynamic reasons. Simple case of the less on the front of the plane the better.

[JD001]

Originally Posted by Tcoat

It is cooling. It is back there for aerodynamic reasons. Simple case of the less on the front of the plane the better.

And I was thinking that you were going to say that the scoop lowered compression.

[Tcoat]

Originally Posted by JD001

And I was thinking that you were going to say that the scoop lowered compression.

Well technically that is exactly what it does. Just on the outside of the plane instead of in the engine.

[Dadhawk]

Originally Posted by HunterGreene

Ok, possibly dumb question, but what is the purpose of the scoop on the bottom of that plane? First answer is engine cooling, but placing it that far back seems unnecessarily complex.

Originally Posted by Tcoat

It is cooling. It is back there for aerodynamic reasons. Simple case of the less on the front of the plane the better.

Yep, the P51 was water-cooled, so the radiator had to be somewhere besides "in front" (most WWII era prop driven airplanes were air-cooled hence the big front ends on them)

Here's the airflow. This actually contributed to the P51s superior speed, and really wasn't that complex, it was just a good place to pick up air without adding drag.