i'm thinking, since the SR also has casted pistons but they are running lower CR, it makes them alot friendlier to boost.
now i can't afford a entire engine rebuild esp since my engine still has perfect compression. now i want to run 20 psi and i know that if they make some kind of spacer for the head, it would be the cheapest and most effective way for me to up my boost reliablity.
anyone chime in on this?
do they make spacers for the head to reduce CR?
There's an area around the outer edge of the piston that comes closest to the edges of the combustion chamber on the head. This area is called the "quench" zone. It's sole purpose is to squish the intake charge toward the center of the combustion chamber, isolating it from the cylinder wall and ring area.
When you increase the distance between the piston and the head (via thicker headgasket, as you're considering), this quench area is adversely affected.
By opening the quench area, gases are allowed to hang around the rings, which creates hotspots in the combustion area. Hotspots are an advocate of detonation/pre-ignition.
Consequently, opening the quench area will create a knock-limited engine, meaning that MBT is not reached before knocking occurs. You might be successful in lowering the static CR, but you won't be able to achieve maximum torque before knocking.
In short, there's no better way to lower the static CR than either forged low compression pistons, or modifying the combustion chamber on the head, the latter being a second choice over the first.
Hope this information helps.
When you increase the distance between the piston and the head (via thicker headgasket, as you're considering), this quench area is adversely affected.
By opening the quench area, gases are allowed to hang around the rings, which creates hotspots in the combustion area. Hotspots are an advocate of detonation/pre-ignition.
Consequently, opening the quench area will create a knock-limited engine, meaning that MBT is not reached before knocking occurs. You might be successful in lowering the static CR, but you won't be able to achieve maximum torque before knocking.
In short, there's no better way to lower the static CR than either forged low compression pistons, or modifying the combustion chamber on the head, the latter being a second choice over the first.
Hope this information helps.
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epokh
- Posts: 292
- Joined: Thu Jun 02, 2005 9:37 pm
- Car: 92 240 HB
92 240 Coupe
02 Sentra - Location: SW Mo.
Re: (S14tat)
No, it's not the same, because correctly designed pistons retain proper quench...the compression is lowered by "dishing" the center of the piston, without disturbing the outer quench area.
Re: (epokh)
Correct, sir!epokh wrote:No, it's not the same, because correctly designed pistons retain proper quench...the compression is lowered by "dishing" the center of the piston, without disturbing the outer quench area.
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sil80drifter
- Posts: 1313
- Joined: Sun Aug 18, 2002 5:53 am
- Car: 1990 240SX Hatch
Re: (sil80drifter)
Uh...that's what we've been discussing the entire time. Silly drifter!sil80drifter wrote:Am I not getting this right, or has nobody ever heard of a thicker headgasket?
sil80