Compression doesn't make sense
04-14-2008, 01:09 AM
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Compression doesn't make sense
Why is a smaller bore more compression? U'd figured the more space taken up in the block the more compression? Maybe some can shed some light because i'm tryna build a n/a d series motor
04-14-2008, 04:29 AM
#3
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Re: Compression doesn't make sense (97CWITR)
A smaller bore doesn't always net you higher compression.
I have a 500 CID engine with 12:1 CR, it has a bore of 110.5mm that's a large bore but I still have high compression. It's more about getting the proper combination of parts. The piston cc's, rod length and crank stroke play a major roll in compression ratio. And and you can't forget about the size of the combustion chamber in the head as well.
I have a 500 CID engine with 12:1 CR, it has a bore of 110.5mm that's a large bore but I still have high compression. It's more about getting the proper combination of parts. The piston cc's, rod length and crank stroke play a major roll in compression ratio. And and you can't forget about the size of the combustion chamber in the head as well.
04-14-2008, 02:28 PM
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Re: Compression doesn't make sense (ddd4114)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ddd4114 »</TD></TR><TR><TD CLASS="quote">Boring the engine will increase compression (assuming everything else is the same).</TD></TR></TABLE>
Correct. You get a little bump in compression going from stock pistons to over-sized ones. Check out this linnk, very useful!!
http://www.c-speedracing.com/h...c.php
Correct. You get a little bump in compression going from stock pistons to over-sized ones. Check out this linnk, very useful!!
http://www.c-speedracing.com/h...c.php
04-14-2008, 06:36 PM
#7
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Re: Compression doesn't make sense (emotionisdead)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by emotionisdead »</TD></TR><TR><TD CLASS="quote">
Correct. You get a little bump in compression going from stock pistons to over-sized ones. Check out this linnk, very useful!!
http://www.c-speedracing.com/h...c.php</TD></TR></TABLE>
so by increasing the volume, you increase compression?
that is *** backwards.
Correct. You get a little bump in compression going from stock pistons to over-sized ones. Check out this linnk, very useful!!
http://www.c-speedracing.com/h...c.php</TD></TR></TABLE>
so by increasing the volume, you increase compression?
that is *** backwards.
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04-14-2008, 06:43 PM
#8
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Re: Compression doesn't make sense (98vtec)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 98vtec »</TD></TR><TR><TD CLASS="quote">
so by increasing the volume, you increase compression?
that is *** backwards.
</TD></TR></TABLE>
Not necessarily. If you make the bore bigger, with the same CH/CC dome, and dont touch the chamber, compression will increase. You're compressing more volume into the same small chamber.
so by increasing the volume, you increase compression?
that is *** backwards.
</TD></TR></TABLE>
Not necessarily. If you make the bore bigger, with the same CH/CC dome, and dont touch the chamber, compression will increase. You're compressing more volume into the same small chamber.
04-14-2008, 06:51 PM
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Re: Compression doesn't make sense (98vtec)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 98vtec »</TD></TR><TR><TD CLASS="quote">so by increasing the volume, you increase compression?</TD></TR></TABLE>
You are compressing more air.
A simplified formula to determine compression ratio is:
(π*(b/2)^2*s+Vc)/Vc
Let's say you have an engine with a 75mm bore, 90mm stroke and 35cc combustion chambers.
(π*(.075/2)^2*(.090)+(35E-6))/(35E-6) = 12.4
If you increase the bore to 78mm (and use pistons of a similar design):
(π*(.078/2)^2*(.090)+(35E-6))/(35E-6) = 13.3
There are other variables, but you get the idea.
You are compressing more air.
A simplified formula to determine compression ratio is:
(π*(b/2)^2*s+Vc)/Vc
Let's say you have an engine with a 75mm bore, 90mm stroke and 35cc combustion chambers.
(π*(.075/2)^2*(.090)+(35E-6))/(35E-6) = 12.4
If you increase the bore to 78mm (and use pistons of a similar design):
(π*(.078/2)^2*(.090)+(35E-6))/(35E-6) = 13.3
There are other variables, but you get the idea.
04-14-2008, 06:57 PM
#11
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Re: Compression doesn't make sense (98vtec)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 98vtec »</TD></TR><TR><TD CLASS="quote">ah ok, thanks for the simplified explanation. Was thinking differently. </TD></TR></TABLE>
Crowler.
Crowler.
04-14-2008, 07:52 PM
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Re: Compression doesn't make sense (yrpin5th)
well i'm tryna go all motor but use oem parts in a lil d series motor... so sleeving a d16y8 to 74.98 bore with a 2001 ex crank, 2001 ex pistons, and ls rods... would be a super high compressioned d series????
04-14-2008, 07:56 PM
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Re: Compression doesn't make sense (yrpin5th)
the formula was a big help but it still doesn't prove that bigger bore is more compression if u break it down into kilo meter decimals
04-14-2008, 09:23 PM
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Re: Compression doesn't make sense (yrpin5th)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by yrpin5th »</TD></TR><TR><TD CLASS="quote">well i'm tryna go all motor</TD></TR></TABLE>
How do you TRY and go all motor? either you do or you dont.
Compression increases if you increase bore size but keep everything the same.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by yrpin5th »</TD></TR><TR><TD CLASS="quote">the formula was a big help but it still doesn't prove that bigger bore is more compression if u break it down into kilo meter decimals</TD></TR></TABLE>
wat
How do you TRY and go all motor? either you do or you dont.
Compression increases if you increase bore size but keep everything the same.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by yrpin5th »</TD></TR><TR><TD CLASS="quote">the formula was a big help but it still doesn't prove that bigger bore is more compression if u break it down into kilo meter decimals</TD></TR></TABLE>
wat
04-14-2008, 11:28 PM
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Re: Compression doesn't make sense (yrpin5th)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by yrpin5th »</TD></TR><TR><TD CLASS="quote">the formula was a big help but it still doesn't prove that bigger bore is more compression if u break it down into kilo meter decimals</TD></TR></TABLE>
Yes, the formula does prove this. What do you mean by "break it down into kilometer decimals"? Everything should be in base units, or it will not work.
If you want to get a good idea of your static compression ratio, use this:
http://www.zealautowerks.com/dseries.html
Yes, the formula does prove this. What do you mean by "break it down into kilometer decimals"? Everything should be in base units, or it will not work.
If you want to get a good idea of your static compression ratio, use this:
http://www.zealautowerks.com/dseries.html
04-15-2008, 06:20 AM
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Re: Compression doesn't make sense (ddd4114)
This picture was made in ms paint.
It is a 2d engine.
This picture assumes the all the area at TDC is located in the head.
I didn't use inch size for everything nor did I use squared.
I am not liable if you bore your engine 1"
I condensed the picture because I realized it was too big the first time.
04-15-2008, 08:00 AM
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Re: Compression doesn't make sense (Combustion Contraption)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Combustion Contraption »</TD></TR><TR><TD CLASS="quote">
How do you TRY and go all motor? either you do or you dont.
Compression increases if you increase bore size but keep everything the same.
wat</TD></TR></TABLE>
I just laughed out loud for a good 20 seconds.. thx.
How do you TRY and go all motor? either you do or you dont.
Compression increases if you increase bore size but keep everything the same.
wat</TD></TR></TABLE>
I just laughed out loud for a good 20 seconds.. thx.
04-15-2008, 10:05 AM
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Re: Compression doesn't make sense (yrpin5th)
I say try because i might have to try, try again if my setup blows a piston, ring, or a rod
04-16-2008, 11:50 AM
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Re: Compression doesn't make sense (NegativeXero)
its not a waste of money... good on gas... and fun to play wit durin inner-city drivin'... i think 200 hp is keepin' up wit gsr... wit my ek9
04-16-2008, 12:08 PM
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Re: Compression doesn't make sense (yrpin5th)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by yrpin5th »</TD></TR><TR><TD CLASS="quote">its not a waste of money... good on gas... and fun to play wit durin inner-city drivin'... i think 200 hp is keepin' up wit gsr... wit my ek9</TD></TR></TABLE>
You're saying that you plan to get 200hp from a d-series?
You're saying that you plan to get 200hp from a d-series?
04-18-2008, 12:35 PM
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Re: Compression doesn't make sense (yrpin5th)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by yrpin5th »</TD></TR><TR><TD CLASS="quote">you damn right i'm gettin 200 hp</TD></TR></TABLE>
04-18-2008, 12:57 PM
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Re: Compression doesn't make sense (yrpin5th)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by yrpin5th »</TD></TR><TR><TD CLASS="quote">you damn right i'm gettin 200 hp</TD></TR></TABLE>
LMAO! I havent had a laugh like this in a while!
LMAO! I havent had a laugh like this in a while!