Lowering compression for turbo..

Hunt_chevs · September 16th, 2009, 12:53 AM

im in the process of purchasing another fox, with intentions of a turbo set up.. my question is what's a safe compression ratio for a mild/moderate turbo set up. Mods on this vehicle is as follows: The motor is fully built and its out of a 95 cobra so it could be legal in the car. it hascp pistons that are 12:1 compression manielt conecting rods. the heads are gt40x racing heads that have been CNC ported with a e3o3 cam 1:70 ration roller rocker arm. cobra manifolds.. hooked to a word classs t5 transmission and the rear end has a alburn locker with 33 spline axles.. Now obviously there are a couple things i would do differently, such as the manifolds.. but my goal is to have a nice turbo, maybe twins on it.. The car used to have a 5.8l power plant in it but my boy has recently changed it to the 95 cobra from what i understand...

CAMN89GT · September 16th, 2009, 04:46 AM

8:1, 8.5:1, 9:1

M L Struck · September 16th, 2009, 07:20 AM

you are going to have to get that compression down to 9:1 or lower and single turbo can be way more then what your block wants, and that T5 will not last long in stock form behind a turbo. The big question is what is your power goal?

What manifolds?

nolife · September 16th, 2009, 09:03 AM

There are three ways to make power with boost.

Low static compression / high boost
High static compression / low boost
Medium static compression / medium boost

There are advantages and disadvantages to each setup. 9.0 is probably a good starting point and you will have some flexibility with adjustments and changes with boost, timing, fuel type and fuel amount from there.

e3sean · September 16th, 2009, 11:32 AM

Originally Posted by Hunt_chevs

Mods on this vehicle is as follows: The motor is fully built gt40x racing heads that have been CNC ported with a e3o3 cam 1:70 ration roller rocker arm. cobra manifolds.. hooked to a word classs t5 transmission...

i would take the work fully built out of that and maby add in a somewhat or mildly

just messin with ya.

but really i would start with another motor you can try to baindaid those pistons with thick copper head gaskets but i wouldnt.. if its a high compression motor then put in some good gas and a bottle of squeeze and have at it..

nolife · September 16th, 2009, 12:42 PM

I'm not defending them at all but I make decent power with unported GT40X heads and boost. Not ideal but enough to worry about the block.

ryans88gt · September 16th, 2009, 01:03 PM

depends on what type of gas you are using and how much timing you are willing to pull.

I made an easy 15 PSI on pump gas at 9:1 compression on my blue fox with about 20 degrees of timing

Currently the cobra is pushing 23 PSI with a stock shortblock and pump gas plus meth/water

bretts95gt · September 16th, 2009, 01:04 PM

youd def. have to switch out the pistons for some dish tops

but shoot for 8:1 to 9:1 like everyone else said an she should be right

Hunt_chevs · September 16th, 2009, 03:50 PM

Originally Posted by M L Struck

you are going to have to get that compression down to 9:1 or lower and single turbo can be way more then what your block wants, and that T5 will not last long in stock form behind a turbo. The big question is what is your power goal?

What manifolds?

motor is fully built cobra r capable of withstanding 1000hp.. however i am aware of the tranny issue,.. but i was only considering getting to 500-600hp.. as for manifolds,.. probably a systemax setup

Hunt_chevs · September 16th, 2009, 04:02 PM

Originally Posted by nolife

There are three ways to make power with boost.

Low static compression / high boost
High static compression / low boost
Medium static compression / medium boost

There are advantages and disadvantages to each setup. 9.0 is probably a good starting point and you will have some flexibility with adjustments and changes with boost, timing, fuel type and fuel amount from there.

so is 12:1 to high of compression to run even low boost?

Hunt_chevs · September 16th, 2009, 04:04 PM

Originally Posted by e3sean

i would take the work fully built out of that and maby add in a somewhat or mildly

just messin with ya.

but really i would start with another motor you can try to baindaid those pistons with thick copper head gaskets but i wouldnt.. if its a high compression motor then put in some good gas and a bottle of squeeze and have at it..

i might just end up doing that,. being as i dont really want to start undoing the work on the 1500mile motor just yet..

e3sean · September 16th, 2009, 04:41 PM

just be careful on how big of a shot you put in it cause depending on how it was set up and the ring gap

Hunt_chevs · September 16th, 2009, 04:58 PM

i was thinkin along the lines of a 150.. maybe,..maybe a 200 what do you think?

Iownastang · September 16th, 2009, 10:05 PM

What kind of block is it since its capable of withstanding 1000 hp?

Hunt_chevs · September 18th, 2009, 02:11 PM

i'll get at him and find out exactly..

all i know as of now is its a built 351 out of a 95 cobra r

September 16th, 2009, 12:53 AM	#1
Hunt_chevs Hardcore Enthusiast 2002 Gt Not Slow Join Date: Aug 2007 Location: SJ-CA, 50-ft elev. Posts: 1,649 iTrader: 1 reviews	Lowering compression for turbo.. im in the process of purchasing another fox, with intentions of a turbo set up.. my question is what's a safe compression ratio for a mild/moderate turbo set up. Mods on this vehicle is as follows: The motor is fully built and its out of a 95 cobra so it could be legal in the car. it hascp pistons that are 12:1 compression manielt conecting rods. the heads are gt40x racing heads that have been CNC ported with a e3o3 cam 1:70 ration roller rocker arm. cobra manifolds.. hooked to a word classs t5 transmission and the rear end has a alburn locker with 33 spline axles.. Now obviously there are a couple things i would do differently, such as the manifolds.. but my goal is to have a nice turbo, maybe twins on it.. The car used to have a 5.8l power plant in it but my boy has recently changed it to the 95 cobra from what i understand... __________________ 2k2 Gt Eibach pro kit, bbk cold air, exhaust, 4.10s, 6k hid's

September 16th, 2009, 04:46 AM	#2
CAMN89GT Banned 1988 Mustang Notch it's a bad bitch..i promise Join Date: Dec 2006 Location: Chicago Posts: 980 iTrader: 0 reviews	8:1, 8.5:1, 9:1 __________________ '88 Notch ~ T-70 & Faceplated GForce! Tuned by [B][I][U]Kurgan Motorsports[/U][/I][/B]

September 16th, 2009, 07:20 AM	#3
M L Struck Hardcore Enthusiast 85 GT/86 SVO/2010 GT500 Join Date: Oct 2008 Location: Rossville IN Posts: 1,183 iTrader: 0 reviews	you are going to have to get that compression down to 9:1 or lower and single turbo can be way more then what your block wants, and that T5 will not last long in stock form behind a turbo. The big question is what is your power goal? What manifolds? __________________ "Having a 9 second neon is like coming out of the closet, everyone is shocked at first, but in the end you're still gay." 5.4 Shelby Crew member #1

September 16th, 2009, 09:03 AM	#4
nolife MM Fanatic 91GT, 88GT, 02GT Join Date: Dec 2006 Posts: 3,057 Blog Entries: 3 iTrader: 0 reviews	There are three ways to make power with boost. Low static compression / high boost High static compression / low boost Medium static compression / medium boost There are advantages and disadvantages to each setup. 9.0 is probably a good starting point and you will have some flexibility with adjustments and changes with boost, timing, fuel type and fuel amount from there. __________________ Last edited by nolife; September 16th, 2009 at 09:11 AM.

September 16th, 2009, 12:42 PM	#6
nolife MM Fanatic 91GT, 88GT, 02GT Join Date: Dec 2006 Posts: 3,057 Blog Entries: 3 iTrader: 0 reviews	I'm not defending them at all but I make decent power with unported GT40X heads and boost. Not ideal but enough to worry about the block. __________________ Last edited by nolife; September 16th, 2009 at 12:45 PM.

September 16th, 2009, 01:03 PM	#7
ryans88gt MM Fanatic Join Date: May 2007 Location: Bloomington, IL Posts: 4,737 iTrader: 0 reviews	depends on what type of gas you are using and how much timing you are willing to pull. I made an easy 15 PSI on pump gas at 9:1 compression on my blue fox with about 20 degrees of timing Currently the cobra is pushing 23 PSI with a stock shortblock and pump gas plus meth/water __________________ 88 GT CHI headed 351w 10.8 @ 125 - still figuring it out. 03 Cobra 2.3 whipple 10.7 @ 129 - sold it 04 Mach 1 12.7 @ 109 mostly stock - sold it 89 LX procharged 302 515 hp 497 ftlbs 10.7 @130 mph - sold it

September 16th, 2009, 01:04 PM	#8
bretts95gt Regular 95 mustang gt Join Date: Sep 2008 Location: lexington,sc Posts: 291 iTrader: 0 reviews	youd def. have to switch out the pistons for some dish tops but shoot for 8:1 to 9:1 like everyone else said an she should be right __________________ 95 gt vert-custom fenders 03 cobra front end,twin garret turbos,ported trickflow trackheat heads, hks blowoff valve,spyder efi intake, underdrives,built c4, 4000 stall converter,reverse manual valvebody,4.10 gears Last edited by bretts95gt; September 16th, 2009 at 01:07 PM.

September 16th, 2009, 04:41 PM	#12
e3sean I Post Entirely Way Too Much 1988 lx 9.68@142 Join Date: Nov 2007 Location: goldsboro NC Posts: 5,609 iTrader: 0 reviews	just be careful on how big of a shot you put in it cause depending on how it was set up and the ring gap __________________

September 16th, 2009, 04:58 PM	#13
Hunt_chevs Hardcore Enthusiast 2002 Gt Not Slow Join Date: Aug 2007 Location: SJ-CA, 50-ft elev. Posts: 1,649 iTrader: 1 reviews	i was thinkin along the lines of a 150.. maybe,..maybe a 200 what do you think? __________________ 2k2 Gt Eibach pro kit, bbk cold air, exhaust, 4.10s, 6k hid's

September 16th, 2009, 10:05 PM	#14
Iownastang I Post Entirely Way Too Much 1987 ford mustang gt well see when shes done Join Date: May 2007 Location: mascot, tn Posts: 5,020 iTrader: 0 reviews	What kind of block is it since its capable of withstanding 1000 hp? __________________ 2004 tahoe z71 Daily 2004 BBM Gto ls1 6 speed 57,000 miles 1987 mustang hatch,347,world heads,systemax, kooks lts,nitrous, 6 point cage, team z front and rear suspension,8.8, 4.10s, 31 splines strange axles,wilwood brakes, tko600

September 18th, 2009, 02:11 PM	#15
Hunt_chevs Hardcore Enthusiast 2002 Gt Not Slow Join Date: Aug 2007 Location: SJ-CA, 50-ft elev. Posts: 1,649 iTrader: 1 reviews	i'll get at him and find out exactly.. all i know as of now is its a built 351 out of a 95 cobra r __________________ 2k2 Gt Eibach pro kit, bbk cold air, exhaust, 4.10s, 6k hid's

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