Compression for boost?

bandity2k00 · January 17th, 2010, 10:14 PM

Whats a good compression range for about 18-22lbs of boost, I found a guy selling a forged shortblock with 8:9:1 compression.

Dolbs4082 · January 17th, 2010, 10:22 PM

Thats about right i think. what kind of power adder? because with a centri they usually say 9.6 and lower. so you should be right in line i think

bandity2k00 · January 17th, 2010, 10:29 PM

Procharger! Sounds good!

bandity2k00 · January 17th, 2010, 10:36 PM

Whats cheapest way for him to ship it to me you think guys?

sharkbait · January 17th, 2010, 10:39 PM

8.9 should be about right for your aplicatio

UPS ground. Probobly will be fairly expensive but can be done im pretty sure they do that stuff all the time

Im right around the corner from you. Have you seen my stang around?

bandity2k00 · January 17th, 2010, 10:50 PM

Na not yet we should meet up one night and go prowlin tho!

sharkbait · January 17th, 2010, 10:56 PM

Will do once I get my her fixed hopefully tommarow. Do you ever go cruising in the glen burnie area? Richie highway. Its so fun to mess with the ricers down there.

I-97 can be fun to cruise on aswell

mustang_gtr_99 · January 17th, 2010, 11:01 PM

I am at 9.5:1

bandity2k00 · January 17th, 2010, 11:11 PM

Ya ive been on richie, im only 19 and have a point on my license and have to make it till june so i cant get no tickets or i lose my license and job for 6 months so i gotta watch it but ill still run it lol. Ill have to come up to richie hwy sometime soon when you go and meet you some where and chill, ill bring my chick and we can race some people and eat or something and chill!

BakerFX4 · January 17th, 2010, 11:13 PM

i hope this isnt the one with the big ass gouge in the cylinder?

sharkbait · January 17th, 2010, 11:16 PM

Well im 17 and havnt been caught yet but I know where your coming from bro.

Hell yea im up for that though. I normally run a radar detector and have my gf on cop watch haha. Theres tons of food places down there aswell.

dcook_14 · January 17th, 2010, 11:20 PM

I think around 9-9.5 is good for centri and 8.5 is good for roots/turbo.

What is the best way to lower a compression ratio without changing rods/pistons? Say if I wanted to lower the CR on an engine from 10.5 to 9.5. The two headgasket thing isn't going to make that much of a difference, so forget about that. Can material be safely removed from the combustion chamber on our PI heads?

Is there an easy way to check the compression ratio of an engine? Or do you have to do the thing where you use a graduated burret to check volume at bottom dead center, at top dead center, and the volume of the combustion chamber of the head and then do BDC+CC divided by TDC+CC?

dcook_14 · January 18th, 2010, 12:03 AM

Also I've heard that cam profiles play a part in the dynamic compression ratio... any truth to that? If I had a wicked cam could I swap it out for a milder one and be able to run more boost?

y2k02 · January 18th, 2010, 12:11 AM

My c/r is about 9.5. Yes cams can change the dynamic compression.

dcook_14 · January 18th, 2010, 12:48 AM

Originally Posted by dcook_14

What is the best way to lower a compression ratio without changing rods/pistons? Say if I wanted to lower the CR on an engine from 10.5 to 9.5. The two headgasket thing isn't going to make that much of a difference, so forget about that. Can material be safely removed from the combustion chamber on our PI heads?

Is there an easy way to check the compression ratio of an engine? Or do you have to do the thing where you use a graduated burret to check volume at bottom dead center, at top dead center, and the volume of the combustion chamber of the head and then do BDC+CC divided by TDC+CC?

Anyone know about these two questions?

dcook_14 · January 18th, 2010, 12:49 AM

Originally Posted by y2k02

My c/r is about 9.5. Yes cams can change the dynamic compression.

Do you know how? EG does less lift and duration mean lower dynamic compression? Does lobe separation have anything to do with it?

y2k02 · January 18th, 2010, 01:09 AM

Kennedys DynoTune- Dynamic Compression Ratio Explained

dcook_14 · January 18th, 2010, 01:16 AM

damn you y2k, i was hoping to get cliffnotes on this stuff not links to full articles!

haha, i'm so lazy... time to read up I guess

EDIT: That link is great. I'm really glad I read through it. Basically it says that the more intake duration your cam has, the higher your static CR can be... It makes sense because compression doesn't really start until the intake valve is closed, and that is not at bottom dead center (which is how static CR is measured)

dcook_14 · January 18th, 2010, 06:24 PM

Originally Posted by dcook_14

What is the best way to lower a compression ratio without changing rods/pistons? Say if I wanted to lower the CR on an engine from 10.5 to 9.5. The two headgasket thing isn't going to make that much of a difference, so forget about that. Can material be safely removed from the combustion chamber on our PI heads?

Still looking for an answer on this question

BakerFX4 · January 18th, 2010, 07:16 PM

well cook... thats a tough question cause you are eliminating everything that decides compression. lol... Ported heads lower it i think.

January 17th, 2010, 10:14 PM	#1
bandity2k00 Baker Jr. 2002 Mustang GT Coming after build!! Join Date: Mar 2008 Location: Gambrills,MD Posts: 2,913 iTrader: 3 reviews	Compression for boost? Whats a good compression range for about 18-22lbs of boost, I found a guy selling a forged shortblock with 8:9:1 compression. __________________ MMR-Modular Mustang Racing Phils Machining-For your ABS Module Delete Manifold! American Muscle-www.Americanmuscle.com HorsePower By Hermonn-TUNER THANKS TO ALL SPONSORS,READY FOR THIS 2012 RACING SEASON!

January 17th, 2010, 10:22 PM	#2
Dolbs4082 I Blumpkin Entirely Way Too Much 2005 Mustang GT Join Date: Dec 2008 Location: kansas Posts: 5,958 iTrader: 0 reviews	Thats about right i think. what kind of power adder? because with a centri they usually say 9.6 and lower. so you should be right in line i think __________________ MM + Cleavage member #22

January 17th, 2010, 10:29 PM	#3
bandity2k00 Baker Jr. 2002 Mustang GT Coming after build!! Join Date: Mar 2008 Location: Gambrills,MD Posts: 2,913 iTrader: 3 reviews	Procharger! Sounds good! __________________ MMR-Modular Mustang Racing Phils Machining-For your ABS Module Delete Manifold! American Muscle-www.Americanmuscle.com HorsePower By Hermonn-TUNER THANKS TO ALL SPONSORS,READY FOR THIS 2012 RACING SEASON!

January 17th, 2010, 10:36 PM	#4
bandity2k00 Baker Jr. 2002 Mustang GT Coming after build!! Join Date: Mar 2008 Location: Gambrills,MD Posts: 2,913 iTrader: 3 reviews	Whats cheapest way for him to ship it to me you think guys? __________________ MMR-Modular Mustang Racing Phils Machining-For your ABS Module Delete Manifold! American Muscle-www.Americanmuscle.com HorsePower By Hermonn-TUNER THANKS TO ALL SPONSORS,READY FOR THIS 2012 RACING SEASON!

January 17th, 2010, 10:39 PM	#5
sharkbait Hooo Ha Ha 1997 Mustang GT 11.65 @ 115 Join Date: Apr 2009 Location: Pasadena MD Posts: 9,743 iTrader: 10 reviews	8.9 should be about right for your aplicatio UPS ground. Probobly will be fairly expensive but can be done im pretty sure they do that stuff all the time Im right around the corner from you. Have you seen my stang around? __________________ 410rwhp 520rwtq @ 12.9 psi

January 17th, 2010, 10:50 PM	#6
bandity2k00 Baker Jr. 2002 Mustang GT Coming after build!! Join Date: Mar 2008 Location: Gambrills,MD Posts: 2,913 iTrader: 3 reviews	Na not yet we should meet up one night and go prowlin tho! __________________ MMR-Modular Mustang Racing Phils Machining-For your ABS Module Delete Manifold! American Muscle-www.Americanmuscle.com HorsePower By Hermonn-TUNER THANKS TO ALL SPONSORS,READY FOR THIS 2012 RACING SEASON!

January 17th, 2010, 10:56 PM	#7
sharkbait Hooo Ha Ha 1997 Mustang GT 11.65 @ 115 Join Date: Apr 2009 Location: Pasadena MD Posts: 9,743 iTrader: 10 reviews	Will do once I get my her fixed hopefully tommarow. Do you ever go cruising in the glen burnie area? Richie highway. Its so fun to mess with the ricers down there. I-97 can be fun to cruise on aswell __________________ 410rwhp 520rwtq @ 12.9 psi

January 17th, 2010, 11:01 PM	#8
mustang_gtr_99 Hardcore Enthusiast 1999 3V GT/2007 GT D/D corner carver Join Date: Feb 2009 Location: Eugene, Oregon Posts: 2,730 iTrader: 2 reviews	I am at 9.5:1 __________________ OS2 (SW) USN REAR SEAT DELETE FABRICATOR "RSD pics in garage" 99 3V GT/2007 GT DD

January 17th, 2010, 11:11 PM	#9
bandity2k00 Baker Jr. 2002 Mustang GT Coming after build!! Join Date: Mar 2008 Location: Gambrills,MD Posts: 2,913 iTrader: 3 reviews	Ya ive been on richie, im only 19 and have a point on my license and have to make it till june so i cant get no tickets or i lose my license and job for 6 months so i gotta watch it but ill still run it lol. Ill have to come up to richie hwy sometime soon when you go and meet you some where and chill, ill bring my chick and we can race some people and eat or something and chill! __________________ MMR-Modular Mustang Racing Phils Machining-For your ABS Module Delete Manifold! American Muscle-www.Americanmuscle.com HorsePower By Hermonn-TUNER THANKS TO ALL SPONSORS,READY FOR THIS 2012 RACING SEASON!

January 17th, 2010, 11:13 PM	#10
BakerFX4 I Post Entirely Way Too Much Join Date: Dec 2007 Location: Louisiana Posts: 16,251 iTrader: 14 reviews	i hope this isnt the one with the big ass gouge in the cylinder? __________________ 4.75 MMR 900se Livernois ported heads HP 292s blower cams Procharger D1sc at 20+ psi IW 15% OD pulley (and more bolt ons) E85 Tune/numbers coming shortly!!

January 17th, 2010, 11:16 PM	#11
sharkbait Hooo Ha Ha 1997 Mustang GT 11.65 @ 115 Join Date: Apr 2009 Location: Pasadena MD Posts: 9,743 iTrader: 10 reviews	Well im 17 and havnt been caught yet but I know where your coming from bro. Hell yea im up for that though. I normally run a radar detector and have my gf on cop watch haha. Theres tons of food places down there aswell. __________________ 410rwhp 520rwtq @ 12.9 psi

January 17th, 2010, 11:20 PM	#12
dcook_14 Banned 2004 Mustang GT 12.35@114.08 w/ 1.88 60' Join Date: Feb 2009 Location: Waterloo, IA Posts: 7,015 Blog Entries: 2 iTrader: 7 reviews	I think around 9-9.5 is good for centri and 8.5 is good for roots/turbo. What is the best way to lower a compression ratio without changing rods/pistons? Say if I wanted to lower the CR on an engine from 10.5 to 9.5. The two headgasket thing isn't going to make that much of a difference, so forget about that. Can material be safely removed from the combustion chamber on our PI heads? Is there an easy way to check the compression ratio of an engine? Or do you have to do the thing where you use a graduated burret to check volume at bottom dead center, at top dead center, and the volume of the combustion chamber of the head and then do BDC+CC divided by TDC+CC? __________________ Do the Right Thing, Cook. ~Zip.

January 18th, 2010, 12:03 AM	#13
dcook_14 Banned 2004 Mustang GT 12.35@114.08 w/ 1.88 60' Join Date: Feb 2009 Location: Waterloo, IA Posts: 7,015 Blog Entries: 2 iTrader: 7 reviews	Also I've heard that cam profiles play a part in the dynamic compression ratio... any truth to that? If I had a wicked cam could I swap it out for a milder one and be able to run more boost? __________________ Do the Right Thing, Cook. ~Zip.

January 18th, 2010, 12:11 AM	#14
y2k02 Hardcore Enthusiast 02 Mustang GT 9.91@133 Join Date: Mar 2009 Location: Ohio Posts: 1,307 iTrader: 1 reviews	My c/r is about 9.5. Yes cams can change the dynamic compression. __________________ 2002 GT PI heads Twin 60mm turbos Th400 6.34@114 1/8 9.99@137 1/4 http://i160.photobucket.com/albums/t...t/DSCF5654.jpg http://i160.photobucket.com/albums/t...2gt/IMG060.jpg

January 18th, 2010, 01:09 AM	#17
y2k02 Hardcore Enthusiast 02 Mustang GT 9.91@133 Join Date: Mar 2009 Location: Ohio Posts: 1,307 iTrader: 1 reviews	Kennedys DynoTune- Dynamic Compression Ratio Explained __________________ 2002 GT PI heads Twin 60mm turbos Th400 6.34@114 1/8 9.99@137 1/4 http://i160.photobucket.com/albums/t...t/DSCF5654.jpg http://i160.photobucket.com/albums/t...2gt/IMG060.jpg

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January 18th, 2010, 01:16 AM	#18
dcook_14 Banned 2004 Mustang GT 12.35@114.08 w/ 1.88 60' Join Date: Feb 2009 Location: Waterloo, IA Posts: 7,015 Blog Entries: 2 iTrader: 7 reviews	damn you y2k, i was hoping to get cliffnotes on this stuff not links to full articles! haha, i'm so lazy... time to read up I guess EDIT: That link is great. I'm really glad I read through it. Basically it says that the more intake duration your cam has, the higher your static CR can be... It makes sense because compression doesn't really start until the intake valve is closed, and that is not at bottom dead center (which is how static CR is measured) __________________ Do the Right Thing, Cook. ~Zip. Last edited by dcook_14; January 18th, 2010 at 01:31 AM.

January 18th, 2010, 07:16 PM	#20
BakerFX4 I Post Entirely Way Too Much Join Date: Dec 2007 Location: Louisiana Posts: 16,251 iTrader: 14 reviews	well cook... thats a tough question cause you are eliminating everything that decides compression. lol... Ported heads lower it i think. __________________ 4.75 MMR 900se Livernois ported heads HP 292s blower cams Procharger D1sc at 20+ psi IW 15% OD pulley (and more bolt ons) E85 Tune/numbers coming shortly!!

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