Hi all,
Anybody out there supplying high compression pistons (11:1) for the ecotec L61?
Thanks,
Stephen
Power Curve
1) contact piston company
2) give them specs
3) pay for custom pistons
there's no off-the-shelf high compression pistons for the ecotec
Factory pistons from a Honda K20A have the same bore and wrist pin diameter. Compression height is about 3mm taller.
I've been poking around with this online in my free time, but I dont have parts to actually verify anything. Just throwing it out there if youre mechanically inclined and dont want to go the custom route or just like a challenge.
DFF- Breaking The Boundary wrote:I can get you some CP custom made.
OK Thanks! Where? Have they made a set before? Do they have ideas on the top profile for good burn? Price? What about rings and pins?
I contacted Wiseco but nobody got back to me.
Power Curve
Brian wrote:Factory pistons from a Honda K20A have the same bore and wrist pin diameter. Compression height is about 3mm taller.
I've been poking around with this online in my free time, but I dont have parts to actually verify anything. Just throwing it out there if youre mechanically inclined and dont want to go the custom route or just like a challenge.
Interesting. Wonder how both engine head profiles match up (dome, squish).
Power Curve
Brian wrote:Factory pistons from a Honda K20A have the same bore and wrist pin diameter. Compression height is about 3mm taller.
I've been poking around with this online in my free time, but I dont have parts to actually verify anything. Just throwing it out there if youre mechanically inclined and dont want to go the custom route or just like a challenge.
so instead of custom pistons, you'll need custom rods to compensate for the 3mm difference.
DaFlyinSkwirl (Pj) wrote:Brian wrote:Factory pistons from a Honda K20A have the same bore and wrist pin diameter. Compression height is about 3mm taller.
I've been poking around with this online in my free time, but I dont have parts to actually verify anything. Just throwing it out there if youre mechanically inclined and dont want to go the custom route or just like a challenge.
so instead of custom pistons, you'll need custom rods to compensate for the 3mm difference.
OK.
What is the maximum compression ratio I can run on 97 octane fuel?
Power Curve
DaFlyinSkwirl (Pj) wrote:so instead of custom pistons, you'll need custom rods to compensate for the 3mm difference.
Not exactly. A thicker head gasket would keep the same quench height and what not. An extra .110" would keep the stock head placement relative to the piston. Like I said though, its just something I've been playing with and I dont have parts to set anything in stone.
Just trying to think outside of the box.
Speedster wrote:What is the maximum compression ratio I can run on 97 octane fuel?
The max compression ratio you can run with pump gas is related to your dynamic compression ratio which is determined by the duration and intake centerline of your cams. Higher static compression requires longer duration cams. Most of the stuff I've read suggests a DCR of 8.5:1 for pump gas but honestly there's a lot more that goes into it than just that.
So to answer your question. I cant answer your question
Brian wrote:DaFlyinSkwirl (Pj) wrote:so instead of custom pistons, you'll need custom rods to compensate for the 3mm difference.
Not exactly. A thicker head gasket would keep the same quench height and what not. An extra .110" would keep the stock head placement relative to the piston. Like I said though, its just something I've been playing with and I dont have parts to set anything in stone.
Just trying to think outside of the box.
clearance to the head is not your only concern....
L61
rods 146.5mm
stroke 94.6mm
compression height = 26.75mm
wrist pin diameter = 20mm
R/S ratio = 1.54
total height = 220.55
to my best guestimate, the ecotec deck height is 221mm
add 3mm to the piston compression height, and they'll be exiting the deck
aka
it won't work.
know the size of the box before trying to think outside it
The extra head gasket thickness effectively increases the deck height.
Unless I'm missing something here.
The thicker head gasket increases the clearance from the squish area on the piston to the squish area on the head and makes up for the distance the piston sits proud of the deck. Its the same principle as increasing the deck height of an engine by using a deck plate. Its been done on a few Honda race engines to push a 1.8L B18 block to almost 2.4L before the K series came out. Also its the same principle as using a thicker head gasket to lower compression with stock pistons.
If you have your deck height at 221mm, your total height at 220.55mm and your HG is .040", your deck clearance with the HG is
1.47mm. If you add 3mm compression height your total height is 223.5mm, your deck height is 221mm and your head gasket becomes .158", your deck clearance with the head gasket is
1.51mm. Give or take a little for my rounding the numbers are exactly the same and the head is clear of the piston.
The head clearance is really all you care about with the extra compression height. Too little and you get piston to head contact or a super tight squish area and detonation. Too much and you get lazy swirl and meh combustion.
Past the extra compression height, there's the issue of P2V contact since the valves sit in the head at different angles in the Eco's and K's and the valve reliefs wouldn't be cut right in the piston. But if this is feasible it opens the door to TONS of aftermarket piston options.
Not trying to argue or anything. I like constructive discussion and I just thought I had a decent handle on all of this. Haha.
I going to have to eat my words here.
Apparently I got some wrong info somewhere or fat fingered it in my notes. Stock K20 wrist pin is 22mm (0.866"). This does however make them a perfect fit for an LSJ (which is actually what I wanted to use for an N/A build). Same compression height and bore. Just a 1mm overbore on the wrist pin bore to accept the LSJs 23mm pin and this should allow them to work perfectly on LSJ rods.
where do I start....
the deck height is a measurement of the bottom end only. your headgasket does NOT increase the deck height.
the deck height dictates your maximum bottom end size, PERIOD.
a deck plate is not the same thing as a thicker headgasket. the deck plate adds more height, yes but you also use LONGER SLEEVES to give the piston somewhere to seal on.
a thicker headgasket doesn't give your piston somewhere to go... if the top ring land pops out of the deck, your engine won't work.
your consuming yourself with the head... that isn't your problem. you can't have a piston sticking out of the block... a big DOMED piston is not the same as having the piston try to exit the bottom end.
I think I may have worded my argument a little strange (I think a little strange
). I know the deck height doesn't include the thickness of the head gasket but for the purpose of what I was trying to explain it made more sense to just use it together.
I do agree that you cant have the compression ring popping out of the deck. But we're kind of just assuming that the ring land sits less than 2.5mm from the top of the piston in that situation. It sucks that nobody ever measures that for anything haha.
I'm really not trying to use the extra compression height to make more compression, if thats what it seems like. The whole thing I'm going for right now is getting a factory piston to fit in the block. Once that's done you could use a big domed piston to raise compression.
Guess its time to break my K20a.org account out of retirement.
Speedster wrote:What is the maximum compression ratio I can run on 97 octane fuel?
The max compression ratio you can run with pump gas is related to your dynamic compression ratio which is determined by the duration and intake centerline of your cams. Higher static compression requires longer duration cams. Most of the stuff I've read suggests a DCR of 8.5:1 for pump gas but honestly there's a lot more that goes into it than just that.
So to answer your question. I cant answer your question
My Dynamic Compression Ratio is approx 14:1 and i am running on 93 octane...
i have 10.5:1 comp 20 over pistons. .020 head shave ... .430 lift .222 dur cams ... 1 mm over sized stainless valves.
Mystic02VA (GME Chat) wrote:Speedster wrote:What is the maximum compression ratio I can run on 97 octane fuel?
The max compression ratio you can run with pump gas is related to your dynamic compression ratio which is determined by the duration and intake centerline of your cams. Higher static compression requires longer duration cams. Most of the stuff I've read suggests a DCR of 8.5:1 for pump gas but honestly there's a lot more that goes into it than just that.
So to answer your question. I cant answer your question
My Dynamic Compression Ratio is approx 14:1 and i am running on 93 octane...
i have 10.5:1 comp 20 over pistons. .020 head shave ... .430 lift .222 dur cams ... 1 mm over sized stainless valves.
uh... dynamic compression is always lower than static, so I highly doubt you're running 14:1
I can't edit, the quote got f'd. sue me.
Derp. Better recheck that math Kyle.
I'll have to see where i got the number 14:1 from...
plugging the data in to a dynamic comp calculator, i get this
Static compression ratio of 10.5:1.
Effective stroke is 3.70 inches.
Your dynamic compression ratio is 10.90:1 .
Your dynamic cranking pressure is 236.06 PSI.
Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 10.90 :1.
V/P (Volume to Pressure Index) is 105
however, when running a compression test... i get this
so im running about 22 PSI higher than the calculator states... also the calculator has no place to input the .020 head shave, or the 1mm oversized valves, and only asked for the valve inlet close ABDC ... so that doesn't factor much the cams in... (.430 lift .222 dur twin cam)
Edited 1 time(s). Last edited Sunday, July 07, 2013 1:24 PM
Something is wrong with that calculator. Your DCR should never be higher than your SCR. If it is your basically saying that the engine is going over 100% VE which it really won't unless youre running boost.
I've been wanting to try my calculator with an engine that rotates the opposite direction of a Honda engine because I dont think it should matter. I'll shoot you a PM with all of the specs I need once I get back from dinner if youre interested.
Brian: maybe i have static and dynamic backwards... i always figured static was the comp ratio of the pistons... ... but that doesn't take in to account for the head shave... the head shave does not affect stroke. but it does raise overall compression...
also the piston comp ratio doesn't take in to account for the extra air being allowed in from the bigger valves mixed with the larger cams with longer duration...
so perhaps i'm wrong in thinking my static comp ratio is 10.5:1
The static ratio that manufacturers rate pistons for is based upon using them in a stock engine so as soon as you start mixing different heads, different head gaskets and decking and milling stuff it starts to change.
SCR=(Volume at BDC)/(Volume at TDC)
DCR=(Volume at intake valve closing)/(Volume at TDC)
It all assumes 100% VE so your valves and stuff dont really matter unless youre using flat face valves that reduce the volume of the combustion chamber.
All in all, none of this is perfect but its just another way to evaluate your engine and to help you pick parts that work well together.
