Dynamic compression..
Dynamic compression.. I'm doing some research about dynamic compression and in my searches it seems a dynamic compression of 9.1:1 or lower is needed for pump gas (93). According to the calculator I'm using it seems an F13 with 5.3 heads will yield too high a dynamic compression, yet I see combinations very comparable to this a lot on this board. Tell me if I'm doing or inputting something wrong.
http://www.kb-silvolite.com/calc.php?action=comp
Here are my input values:
Cyl. head cc: 61.15 (stock 5.3?)
piston head cc: 0 (flat top)
gasket: .053 (Fel-Pro MLS per jegs.com)
gask. bore: 3.945 (Fel-Pro MLS per jegs.com)
Cyl. bore: 3.898
Deck Clear.: -.008
Stroke: 3.622
Rod Length: 6.098
IC ABDC: 58 (43 for F13 + 15 per instructions on calculator)
Results: Static Comp. 11.092 Dynamic Comp. 9.267
Let me know what you guys think. Thanks.
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http://www.kb-silvolite.com/calc.php?action=comp
Here are my input values:
Cyl. head cc: 61.15 (stock 5.3?)
piston head cc: 0 (flat top)
gasket: .053 (Fel-Pro MLS per jegs.com)
gask. bore: 3.945 (Fel-Pro MLS per jegs.com)
Cyl. bore: 3.898
Deck Clear.: -.008
Stroke: 3.622
Rod Length: 6.098
IC ABDC: 58 (43 for F13 + 15 per instructions on calculator)
Results: Static Comp. 11.092 Dynamic Comp. 9.267
Let me know what you guys think. Thanks.
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For a double post, a double reply...: https://ls1tech.com/forums/generation-iii-internal-engine/409577-dynamic-compression-question.html
Originally Posted by MadBill
For a double post, a double reply...: https://ls1tech.com/forums/showthread.php?t=409577
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The calculator came out exactly the same as my full-scale geometry diagram of an engine, so that part is correct. I think the part of the concept people have trouble with is the fact that detonation is mostly a low speed phenomenon, so that at high RPM, when the cam comes into tune and the V.E./B.M.E.P shoots up, the now higher-than-'mechanical' CR still isn't a problem. With aluminum fast burn chambers and good knock sensors, LSx engines should be far better off than the average iron head SBC for which the 9:1 DCR limit is suggested.
I've been working on specs for a 7 litre engine for a road race Z06, and with the cam Dynomation 'wants', it needs over 14:1 to reach 9:1 DCR!
I've been working on specs for a 7 litre engine for a road race Z06, and with the cam Dynomation 'wants', it needs over 14:1 to reach 9:1 DCR!
Originally Posted by MadBill
The calculator came out exactly the same as my full-scale geometry diagram of an engine, so that part is correct. I think the part of the concept people have trouble with is the fact that detonation is mostly a low speed phenomenon, so that at high RPM, when the cam comes into tune and the V.E./B.M.E.P shoots up, the now higher-than-'mechanical' CR still isn't a problem. With aluminum fast burn chambers and good knock sensors, LSx engines should be far better off than the average iron head SBC for which the 9:1 DCR limit is suggested.
I've been working on specs for a 7 litre engine for a road race Z06, and with the cam Dynomation 'wants', it needs over 14:1 to reach 9:1 DCR!
I've been working on specs for a 7 litre engine for a road race Z06, and with the cam Dynomation 'wants', it needs over 14:1 to reach 9:1 DCR!
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BMEP is always the issue when ion, detonation, air flow or power are in question
BMEP is actually what will cause detonation. you can have 19:1 dcr but if your bmep is low- you wont knock. Its the pressure and heat etc that cause detonation- not the ratio between initial and final volume of the cylinder.
If you look up some charts- to find max spark timing they will use a constant MEP, not compression ratio.
BMEP is actually what will cause detonation. you can have 19:1 dcr but if your bmep is low- you wont knock. Its the pressure and heat etc that cause detonation- not the ratio between initial and final volume of the cylinder.
If you look up some charts- to find max spark timing they will use a constant MEP, not compression ratio.
Originally Posted by treyZ28
BMEP is always the issue when ion, detonation, air flow or power are in question
BMEP is actually what will cause detonation. you can have 19:1 dcr but if your bmep is low- you wont knock. Its the pressure and heat etc that cause detonation- not the ratio between initial and final volume of the cylinder.
If you look up some charts- to find max spark timing they will use a constant MEP, not compression ratio.
BMEP is actually what will cause detonation. you can have 19:1 dcr but if your bmep is low- you wont knock. Its the pressure and heat etc that cause detonation- not the ratio between initial and final volume of the cylinder.
If you look up some charts- to find max spark timing they will use a constant MEP, not compression ratio.
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Originally Posted by DAPSUPRSLO
Thanks. Man, this stuff is getting confusing, ha ha. So in general a motor which fills the cylinder much more effectively (i.e. a sb2 headed monster) will produce more MEP and hence be more susceptible to knock at wot. Since these motors do not run very well at lower rpms at cruz, or in other words don't generate high MEP values at lower rpms at cruz, then they should have no issues with nock at lower rpms at cruz, this all in theory ofcourse.
why do you think you can have a motor drive find and knock under WOT.
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Originally Posted by treyZ28
sure. why do you think supercharged cars will knock
why do you think you can have a motor drive find and knock under WOT.
why do you think you can have a motor drive find and knock under WOT.
Originally Posted by treyZ28
it will gradually become more intuitive. and then more complicated stuff will confuse you and some arrogant jerk will tell you it will be intuitive
How funny, i've run into that time and time again. Not everyone can be born and immediately know all the answers to everything (important to remember this when on the side of the teacher and as the student). It's part of the fun in finding this stuff out though, lol.
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The saving grace is the 'ignition delay' (think of it as cooking time) between achieving the conditions of heat and compression needed to detonate the remaining mixture and the occurance of the actual explosion. At high RPM, this interval is generally great enough that the normal flame front comes through first.
Originally Posted by MadBill
The saving grace is the 'ignition delay' (think of it as cooking time) between achieving the conditions of heat and compression needed to detonate the remaining mixture and the occurance of the actual explosion. At high RPM, this interval is generally great enough that the normal flame front comes through first.
Originally Posted by MadBill
The calculator came out exactly the same as my full-scale geometry diagram of an engine, so that part is correct. I think the part of the concept people have trouble with is the fact that detonation is mostly a low speed phenomenon, so that at high RPM, when the cam comes into tune and the V.E./B.M.E.P shoots up, the now higher-than-'mechanical' CR still isn't a problem. With aluminum fast burn chambers and good knock sensors, LSx engines should be far better off than the average iron head SBC for which the 9:1 DCR limit is suggested.
I've been working on specs for a 7 litre engine for a road race Z06, and with the cam Dynomation 'wants', it needs over 14:1 to reach 9:1 DCR!
I've been working on specs for a 7 litre engine for a road race Z06, and with the cam Dynomation 'wants', it needs over 14:1 to reach 9:1 DCR!
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Originally Posted by TAQuickness
I'm trying my best to follow along, it's been a while since i've slept, VE = Valve Events or Volumetric Effeciency? & BMEP = ?
