Head gasket
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Head gasket
Hey anyone ever thought about using double head gaskets to bring the compresion doun on there engine? That way you could run more boost preasure with the turbo!
It's not the most effective way to lower comp but it is effective!
I know that some guys that used three head gaskets on a ford focus so the could run the boost presure up higher!
It's not the most effective way to lower comp but it is effective!
I know that some guys that used three head gaskets on a ford focus so the could run the boost presure up higher!
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Of course people have thought of it, but there are serious ramifications to doing such a thing. Think about it...
If you start stacking head gaskets, you create many more places to "blow out". Also by using a "spacer" or multiple head gaskets, you reduce the quench clearance between the cylinder head and the piston tops. Less quench means less fuel atomization, which leads to fuel pooling, hot spots and eventually holes in pistons or severe detonation.
It is a very bad idea to lower compression on a motor by just "adding space" between the pistons and the head. Yes, it does lower compression, but detonation doesn't happen because of compression, it happens due to heat. That heat comes from bad tuning or bad design; making extra layers of head gaskets to lower your compression falls under the "bad design" category.
As a counter-point, higher compression motors will make more power under boost, will spool faster and will have better throttle response than an equivalent motor with low compression. Lower compression only makes it "easier" to turn up the boost, but you HAVE to turn it up in order to match what someone else with higher compression could attain.
-Red-
If you start stacking head gaskets, you create many more places to "blow out". Also by using a "spacer" or multiple head gaskets, you reduce the quench clearance between the cylinder head and the piston tops. Less quench means less fuel atomization, which leads to fuel pooling, hot spots and eventually holes in pistons or severe detonation.
It is a very bad idea to lower compression on a motor by just "adding space" between the pistons and the head. Yes, it does lower compression, but detonation doesn't happen because of compression, it happens due to heat. That heat comes from bad tuning or bad design; making extra layers of head gaskets to lower your compression falls under the "bad design" category.
As a counter-point, higher compression motors will make more power under boost, will spool faster and will have better throttle response than an equivalent motor with low compression. Lower compression only makes it "easier" to turn up the boost, but you HAVE to turn it up in order to match what someone else with higher compression could attain.
-Red-
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ERRR in most cases I would say not to double stack gaskets but yes it has been done. I myself would not but would try and source a thick gasket rather than stack them but yes, it has been done, and sucessfully at that.
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red what kind of comp are you running in your engine under presure? running presure with 10 to 1 or more comp is ruff on the cyl
I don't think that an engine with high comp 10+ with boost around 6 to 12 psi will ever make as much power as an engine with 8 to 8 and 1 half with 20 plus ponds of boost!
Running 20 psi on an engine with 10 to 1 is very hard thing to do!
Of course you don't need as much boost to make good power with a higher comp engine!
I don't think that an engine with high comp 10+ with boost around 6 to 12 psi will ever make as much power as an engine with 8 to 8 and 1 half with 20 plus ponds of boost!
Running 20 psi on an engine with 10 to 1 is very hard thing to do!
Of course you don't need as much boost to make good power with a higher comp engine!
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The new motor is still sitting in Joel's garage, but the static compression we calculated to be at 9.36:1 -- almost precisely what I wanted. I ordered 9:1 compression pistons, but then milled both the block deck AND the cylinder head to bring quench area to exactly what I wanted.
When the motor is dead-cold and the piston is at the very top of it's stroke, it is only 0.037" (at MOST) from touching the cylinder head -- that's a smaller gap than your sparkplug. When the motor is hot and running at full crank, we expect that gap to close to around 0.015" or less; about the thickness of a "small" paperclip.
You ask how much boost? I intend to use the full range of the 3-bar map sensor, which means 29+ psi from a special T3/T4E hybrid that I've ordered. At 700+ CFM and 30psi, this turbo is capable of sustaining 450+ horsepower to the tires.
Here is what you're missing
More boost on the boost gauge doesn't mean more power. It doesn't "hurt" your motor to run boost on a high compression motor, that simply is not true. The stress you refer to is because of MORE POWER; if you ran the same amount of horsepower on your 8.5:1 compression motor, you would have the same stress. The high compression simply means you need less positive manifold pressure to make the same amount of power.
The problem is that everyone associates high compression with STOCK parts, and low compression with AFTERMARKET parts. Aftermarket pistons are stronger than stock for obvious reasons, but nobody seems to catch that.
None of that really matters for this question. This question is about spacers or extra head gaskets.
The only way you should EVER lower your static compression is by ordering pistons. Any other method (spacers, head gaskets, machining stock pistons) is only asking for severe amounts of problems.
Please make note of this: Detonation (pinging) is NOT caused by high compression, it is caused by bad gas, heat or too much spark advance. Heat comes from bad fuel atomization, too little fuel or simply too much pressure from a turbo that's out of it's efficiency range. Spark advance is simple to fix, and so is bad gas.
No, it's not as easy as I try to make it sound, but it's certainly not any harder than a lot of people could handle.
-Red-
When the motor is dead-cold and the piston is at the very top of it's stroke, it is only 0.037" (at MOST) from touching the cylinder head -- that's a smaller gap than your sparkplug. When the motor is hot and running at full crank, we expect that gap to close to around 0.015" or less; about the thickness of a "small" paperclip.
You ask how much boost? I intend to use the full range of the 3-bar map sensor, which means 29+ psi from a special T3/T4E hybrid that I've ordered. At 700+ CFM and 30psi, this turbo is capable of sustaining 450+ horsepower to the tires.
Here is what you're missing
More boost on the boost gauge doesn't mean more power. It doesn't "hurt" your motor to run boost on a high compression motor, that simply is not true. The stress you refer to is because of MORE POWER; if you ran the same amount of horsepower on your 8.5:1 compression motor, you would have the same stress. The high compression simply means you need less positive manifold pressure to make the same amount of power.
The problem is that everyone associates high compression with STOCK parts, and low compression with AFTERMARKET parts. Aftermarket pistons are stronger than stock for obvious reasons, but nobody seems to catch that.
None of that really matters for this question. This question is about spacers or extra head gaskets.
The only way you should EVER lower your static compression is by ordering pistons. Any other method (spacers, head gaskets, machining stock pistons) is only asking for severe amounts of problems.
Please make note of this: Detonation (pinging) is NOT caused by high compression, it is caused by bad gas, heat or too much spark advance. Heat comes from bad fuel atomization, too little fuel or simply too much pressure from a turbo that's out of it's efficiency range. Spark advance is simple to fix, and so is bad gas.
No, it's not as easy as I try to make it sound, but it's certainly not any harder than a lot of people could handle.
-Red-
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Techno -- funny you should ask, if you're interested I can get you a set of 450WHP-guaranteed axles for $600... I happen to be dealing with a guy who does these 
Accent -- nope, becuase quench cleance is different than valve clearance. What might seem odd is, valve clearance can be run much TIGHTER than quench clearance -- 0.015" is still considered safe. My valve reliefs in the pistons are still leaving me with about 0.065" actually, so I still have lots of room. With the new cams, that number is going to come a lot closer to the 0.020 mark instead.
-Red-
Accent -- nope, becuase quench cleance is different than valve clearance. What might seem odd is, valve clearance can be run much TIGHTER than quench clearance -- 0.015" is still considered safe. My valve reliefs in the pistons are still leaving me with about 0.065" actually, so I still have lots of room. With the new cams, that number is going to come a lot closer to the 0.020 mark instead.
-Red-
