Gas porting pistons
01-20-2009, 10:24 PM
#2
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Location: Seattle, WA
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Just to clarify, this is for a race engine right? One that will be torn down every season or so?
I only ask because it was my impression that porting was somewhat "temporary". Don't the ports clog with carbon after long term use (especially at idle or low temps/rpms)? Maybe that's not the case anymore, but I've seen a few pics showing carbon "plugs" in the ports.
I'd think a vaccum pump would be a better option for ring seal. Not as elegant obviously, but adjustable during use.
Good question though.
I only ask because it was my impression that porting was somewhat "temporary". Don't the ports clog with carbon after long term use (especially at idle or low temps/rpms)? Maybe that's not the case anymore, but I've seen a few pics showing carbon "plugs" in the ports.
I'd think a vaccum pump would be a better option for ring seal. Not as elegant obviously, but adjustable during use.
Good question though.
01-21-2009, 11:55 AM
#5
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Location: Richmond B.C.
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http://www.rehermorrison.com/techTalk/22.htm
read this article, some good points in there. id say you will see an increase in power, how much depends on the overall power but its not an expensive or elaborate mod so id say its worth it. i don't know how they work with big hit power adders like nitrous etc. though im sure it would be fine to a point.
read this article, some good points in there. id say you will see an increase in power, how much depends on the overall power but its not an expensive or elaborate mod so id say its worth it. i don't know how they work with big hit power adders like nitrous etc. though im sure it would be fine to a point.
02-10-2009, 06:51 PM
#9
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From CarCraft Magazine:
http://www.carcraft.com/techarticles...ogy/index.html
So there you have it... porting works, IF you have a narrower ring groove in the piston, run high rpms to ensure it's actually working, use thin low tension rings, and expect ring wear to increase due to the high pressures.
Definitely not a street set up.
The ultimate in ring seal is drilling the pistons for gas ports. Compression rings normally need about 0.002-0.004-inch (vertical) ring-to-groove side clearance to allow cylinder pressure to get behind the ring and force it to seal against the groove and cylinder wall. Gas ports apply combustion pressure directly to the back of the ring, allowing the virtual elimination of side clearance. Since the ring is restrained by the groove itself, there’s less opportunity for high-rpm ring flutter. Very thin, narrow, and lightweight 0.043-inch–thick rings are needed to reap gas-porting’s full benefits. Gas ports work best with short piston-compression heights (under 1.200 inches) on engines running 7,000 rpm or higher. The major drawback is that all this positive pressure greatly shortens ring life, so it’s not recommended for street use.
So there you have it... porting works, IF you have a narrower ring groove in the piston, run high rpms to ensure it's actually working, use thin low tension rings, and expect ring wear to increase due to the high pressures.
Definitely not a street set up.
02-11-2009, 02:45 PM
#12
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Absolutely.
I considered this in my 396, but that nagging voice in my head kept trying to hold me back on a durability concerns for a street/strip car. I'm all for efficiency, but the need for low tension rings on a street car make me hesitate.
That said, even if I was to go low tension on the rebuild, and I made this a race-only vehicle (high rpms), I'd probably STILL avoid the gas ports and opt for a vaccum pump instead. An external pump would be easier for me to repair than tearing down the engine for some clogged gas ports if a plug drops its spark during tuning. This just seems like a more delicate system to pressurize rings than I'd be comfortable with after seeing first hand how long it can take to truely fine tune a max-effort engine (or any other non-cookie-cutter set up).
I love the simplicity of the concept, but have to realistic with tuning a new engine. Unless the set up was exactly the same as several previous engines (and I know the tune and my assembly technique is right on every time), I imagine I'd be "scoping" the damn thing every race session to check the piston tops.
I'm curious if SeaFoam or other solvents sprayed through the spark plug hole would clear a clogged port? Granted, you're still pulling plugs and scoping each hole just to make sure, but after your sure its clean and the plugs aren't oil soaked I imagine you'd only check it 2 or 3 times a season.
Obviously supercharged or nitrous guys wouldn't run these due to the wear issues mentioned, but I'm curious if going too high an RPM is a problem here as well. The article above, and others, all mention the need for higher (6500+) rpms to get the proper pressures... implying there's a somewhat standardized hole size (i.e. pressure/force target). Anyone heard of using larger port diameters for the same ring seal but with lower RPMs? In a 396 LT1 with GM PCM the redline's pretty much 7000... but if the holes could be made larger to shoot for a 5000+ target and reduce the odds of clogging in the process, this may be an LT1 option.
Without an aftermarket PCM system this is a no go for LT1s.
I considered this in my 396, but that nagging voice in my head kept trying to hold me back on a durability concerns for a street/strip car. I'm all for efficiency, but the need for low tension rings on a street car make me hesitate.
That said, even if I was to go low tension on the rebuild, and I made this a race-only vehicle (high rpms), I'd probably STILL avoid the gas ports and opt for a vaccum pump instead. An external pump would be easier for me to repair than tearing down the engine for some clogged gas ports if a plug drops its spark during tuning. This just seems like a more delicate system to pressurize rings than I'd be comfortable with after seeing first hand how long it can take to truely fine tune a max-effort engine (or any other non-cookie-cutter set up).
I love the simplicity of the concept, but have to realistic with tuning a new engine. Unless the set up was exactly the same as several previous engines (and I know the tune and my assembly technique is right on every time), I imagine I'd be "scoping" the damn thing every race session to check the piston tops.
I'm curious if SeaFoam or other solvents sprayed through the spark plug hole would clear a clogged port? Granted, you're still pulling plugs and scoping each hole just to make sure, but after your sure its clean and the plugs aren't oil soaked I imagine you'd only check it 2 or 3 times a season.
Obviously supercharged or nitrous guys wouldn't run these due to the wear issues mentioned, but I'm curious if going too high an RPM is a problem here as well. The article above, and others, all mention the need for higher (6500+) rpms to get the proper pressures... implying there's a somewhat standardized hole size (i.e. pressure/force target). Anyone heard of using larger port diameters for the same ring seal but with lower RPMs? In a 396 LT1 with GM PCM the redline's pretty much 7000... but if the holes could be made larger to shoot for a 5000+ target and reduce the odds of clogging in the process, this may be an LT1 option.
Without an aftermarket PCM system this is a no go for LT1s.
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