Quench area with boosted engines.
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Quench area with boosted engines. I'm rebuiling a stock displacement LSA engine to have 12~ psi of boost via a ZL1 S/C, I'm about buy a set of new forged pistons, and since I came from a N/A territory where everybody is seeking a nice and tight quench area (.040 to as little as .035), I'm sure its totally different with boosted applications!, so whats the optimum quench that I can set to with a street driven 12-14 psi LSA engine?, I kept hearing different openions about it, what do you guys set your quench to with FI engines?
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Joined: Feb 2013
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10.2 to 1 real compression not just a guess off of what the piston manufacturer says. Always makes me laugh when some one says its 10.5 to 1 cause it has 10.5 to 1 pistons. 16 pounds of boost. Props for measuring **** most don't even think about. I build engines for a living so I measure everything.
Very relevant question.
The general consensus is (in a power adder world) a larger quench opens up the tuning window. Or maybe a better way to say it is....gives you some "cushion" on hitting the tune up. See many top builders say 0.075" to 0.100" for big power combos. (My boosted short block will have only 0.079").
So piston compression height will need to be designed in. And given the piston in the hole as well as the gasket, careful consideration for desired SRC will need to be calc'ed.
It's a topic not discussed here much but info can be found on YB or speedtalk.
I'm always suprised to see these guys zero decking or even pushing the piston out of the hole with big boosted combos. Often wonder what the approach was when designing their short block.
Good luck on the combo...
The general consensus is (in a power adder world) a larger quench opens up the tuning window. Or maybe a better way to say it is....gives you some "cushion" on hitting the tune up. See many top builders say 0.075" to 0.100" for big power combos. (My boosted short block will have only 0.079").
So piston compression height will need to be designed in. And given the piston in the hole as well as the gasket, careful consideration for desired SRC will need to be calc'ed.
It's a topic not discussed here much but info can be found on YB or speedtalk.
I'm always suprised to see these guys zero decking or even pushing the piston out of the hole with big boosted combos. Often wonder what the approach was when designing their short block.
Good luck on the combo...
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Thread Starter
On The Tree
Joined: Feb 2013
Posts: 184
Likes: 2
Very relevant question.
The general consensus is (in a power adder world) a larger quench opens up the tuning window. Or maybe a better way to say it is....gives you some "cushion" on hitting the tune up. See many top builders say 0.075" to 0.100" for big power combos. (My boosted short block will have only 0.079").
So piston compression height will need to be designed in. And given the piston in the hole as well as the gasket, careful consideration for desired SRC will need to be calc'ed.
It's a topic not discussed here much but info can be found on YB or speedtalk.
I'm always suprised to see these guys zero decking or even pushing the piston out of the hole with big boosted combos. Often wonder what the approach was when designing their short block.
Good luck on the combo...
The general consensus is (in a power adder world) a larger quench opens up the tuning window. Or maybe a better way to say it is....gives you some "cushion" on hitting the tune up. See many top builders say 0.075" to 0.100" for big power combos. (My boosted short block will have only 0.079").
So piston compression height will need to be designed in. And given the piston in the hole as well as the gasket, careful consideration for desired SRC will need to be calc'ed.
It's a topic not discussed here much but info can be found on YB or speedtalk.
I'm always suprised to see these guys zero decking or even pushing the piston out of the hole with big boosted combos. Often wonder what the approach was when designing their short block.
Good luck on the combo...
How do a large quench affect the performance of a boosted engine? will it be more prone to detonation? will it have any flame propogation issue? And when you said it will give me more "window" to tune, do you mean that I can reach a leaner mixture and/or rise the timing more comfortably?
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Squish with SC engines Hi Kamaro, I AGREE with YOUR Tech !
I would use a Felpro 1041 HG AND a "proud" piston deck of .007" depending on MAX RPM AND block material AL/Iron ?
I would fit MY stud kit.
I am doing the same (LSA) order for a RaceTec Forged Piston.
My "tech" is to reduce the Dish Bore Diameter AND add depth for the correct Squish, the correct CR.
The LSA AL block will expand (grow) more than an Iron block.
The lower CR of a SC engine LOVES Squish as this feature produces Swirl with results in MUCH better Throttled Performance.
Would you like a RaceTec Forged Piston ?
Lance
I would use a Felpro 1041 HG AND a "proud" piston deck of .007" depending on MAX RPM AND block material AL/Iron ?
I would fit MY stud kit.
I am doing the same (LSA) order for a RaceTec Forged Piston.
My "tech" is to reduce the Dish Bore Diameter AND add depth for the correct Squish, the correct CR.
The LSA AL block will expand (grow) more than an Iron block.
The lower CR of a SC engine LOVES Squish as this feature produces Swirl with results in MUCH better Throttled Performance.
Would you like a RaceTec Forged Piston ?
Lance
Thanks for your input, and as I said earlier, I came from N/A engine building, where I always keep an eye on the quench in every build I do.
How do a large quench affect the performance of a boosted engine? will it be more prone to detonation? will it have any flame propogation issue? And when you said it will give me more "window" to tune, do you mean that I can reach a leaner mixture and/or rise the timing more comfortably?
How do a large quench affect the performance of a boosted engine? will it be more prone to detonation? will it have any flame propogation issue? And when you said it will give me more "window" to tune, do you mean that I can reach a leaner mixture and/or rise the timing more comfortably?
Tight quench speeds up the cumbustion process...which is what you want for a n/a combo. The quicker the flame front the less ingintion advance you need. Less ignition advance means less BTDC struggle which = more hp
But..in a power adder world, your trying to slow down the burn rate, in an attempt to control the chaos. And by reducing the quench it slows the burn rate (because the mixture is spread out in the chamber, tight quench forces the mixture away from the edges and towards the center of the chamber, thus speeding up the burn)...because your effectively killing the efficiency of the chamber...or at least hurt it.
Same thing as softening the chambers...its an attempt at killing the efficient chamber.
To answer some of your questions....
The performance gain will come in the form of a well controlled burn at any boost level.
typically the tighter the quench the greater risk of detonation (because your speeding up the burn).
Flame propagation will be somewhat compromised by nature of the beast.
More window....as in you won't melt your combo to the ground if the tune up is a tad off...or the da swings 500'. The AFR should be targeted regardless of quench.
Thanks...just my simple understanding
....EDIT......but I have learned over the years...people can tear up anything. So all of this is to be taken with a grain of salt.
.
Last edited by LSOHOLIC; Sep 18, 2017 at 11:40 AM.