Camshaft and compression November 15, 2020 12:40PM
Was looking for some info.

I'm a bit confused..maybe

Does a camshaft effect the compression ratio on an Diesel engine . I suspect yes.
Here is why I'm confused. My dt466 pistons are cut 12:1 ..tractor starts right up with minimal either. Hypercam. I suspect the intake valve, and exhaust valves are fully closed on compression stroke . I decompressed, but it didn't help with the heat as much as I wanted it too.

I've heard other engines start with 13.1 13.5 to 1 and start hard . I suspect they are scavenging on intake or exhaust. Cracking the valve, valves on compression stroke ?

Am I wrong. Or ? Not sure any info appreciated

Thanks
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Re: Camshaft and compression November 15, 2020 01:11PM
Your cam timing will change your cranking compression but not your compression ratio Depends a lot on where your degreed in at
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Re: Camshaft and compression November 15, 2020 01:14PM
1st off your compression ratio is what it is. Be it 6:1 or 16:1. A camshaft has no bearing on compression ratio. However different cam grinds can affect how much actual cranking compression as in pressure that builds as the piston compresses the air drawn into the engine from the intake stroke. As for valves being open on compression stroke, especially on top half of stroke, this should not be happening. Some cams may allow some boosted intake air to continue into the cylinder at bottom end of compression stroke however should close quickly before piston travels too high up the cylinder. As for starting harder or easier can be related to injection timing. Don't get me wrong a cam designed for larger turbo and higher rpm would be an good example of one that might cause lower cranking compression but under full load and boost would perform better that a cam design for smaller turbo and rpm.
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Re: Camshaft and compression November 15, 2020 01:45PM
Ok . Somewhat makes sense .
Hyper cam is 00 degree at 99..per there instructions.

So when I bought the Pistons they were 13.1 I sent them back and they cut them to 12.1 .
I assume there is more to compression ratio than the Pistons obviously. So in theory the cam grind or profile wouldn't change the compression ratio in the engine?

So if I was timed at injection timing at say 40 deg btdc in should crank harder , as the fuel air mixture has to squeeze the fuel , vs if I was at
32 deg BTDC ?
I'm trying to figure out if roller cam is better than flat tappet. I have a flat right now. Most say roller is better . Some things seem conflicting, as far as information.
It seems the flat cam I have you cant adjust the cam timing at all. It makes it worse
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Re: Camshaft and compression November 16, 2020 05:28AM
Google "valve lift vs crank angle" and you will see graphs that explain what folks are talking about. You should get someone to make one for your setup and it will tell you a lot.
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Re: Camshaft and compression November 16, 2020 11:26AM
YOU NEED A ADJUSTABLE CAM GEAR OR MAKE OFF SET KEYS ON A ROLLER OR FLAT TAPPET
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Re: Camshaft and compression November 17, 2020 09:48AM
Not to be rude but I am confused as to what you are asking? Little hard to follow.
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