is 10.5:1 compression too high for a supercharger?

87StangLX · November 4th, 2007, 09:35 AM

prolly jus as long as i dont go to far over 400hp though. dont want a cracked block :wink

RandoGT · November 4th, 2007, 11:20 AM

well how do you lower the compression after a full PI swap on a 98 GT?
i've been wanting to know this forever but no one has ever answered it

00vabchgt · November 4th, 2007, 11:32 AM

after a PI swap with the stock pistons, you should be looking at about a 10.5:1 compression ratio, assuming your bore is still stock. going to a larger size piston dish will lower your compression ratio, as will having the heads worked to include a larger size combustion chamber.

RandoGT · November 4th, 2007, 03:36 PM

so a more cc, so to say, piston? like 18cc, 19cc, etc. get what i'm saying? and working the heads? porting?

00vabchgt · November 4th, 2007, 06:57 PM

yeah, the non PI stangs had 11cc pistons with a 51cc combustion chamber that made for a 9.3:1 compression ratio. with the PI heads, you have a 42cc combustion chamber which, when combined with the 11cc dish pistons yield a compression ratio of 10.52:1, assuming a standard bore of 3.551 inches. if you went to a 17cc dish piston like stock on the PI stangs, you'd be looking at about a 9.7:1 compression ratio...

RandoGT · November 5th, 2007, 01:04 AM

ah marvelous. after 20 times of asking that question it's finally answered. and would that be a good CR for goin blown? also, if i decide that i wanna go nitrous, would any more compression blow my engine? cause i heard nitrous loves compression

00vabchgt · November 5th, 2007, 09:24 AM

i talked to the guys at Sean Hyland Motorsport about 2 weeks ago. i told the guy my plans for the build included a centri blower going on the car, but not for about another year or so. i told him i was looking to make about 500rwhp. he recommended going 17cc on the pistons, which is actually the same size dish on the stock PI motor pistons. it really depends on th amount of boost you plan on running. as for the nitrous, i'm not really sure. i don't plan on messing around with spray on a daily driver...
i'll see what i can find out for you...

pimpdout98gt · April 1st, 2008, 09:59 PM

well after calculation my car supposedly has 10:7.1 compression cause i install flattop pistons. i only get detonation when im really pulling hard. btu i have a paxton supercharger and this car really pulls hard. i was able to pull 427 ft. lbs. of torque at 3900 rpm and 6 p.s.i.

suprajay79 · April 17th, 2008, 01:49 PM

Real quick and easy way to lower your compression a few points is to install a thicker head gasket... not sure of all the options though.

Goblin · April 18th, 2008, 01:48 AM

Originally Posted by suprajay79

Real quick and easy way to lower your compression a few points is to install a thicker head gasket... not sure of all the options though.

A few points? Uhh, NO. Besides, you dont run thicker head gaskets to drop your compression anyways, thats a no-no.

pimpdout98gt · April 18th, 2008, 06:01 AM

anyone know what my compression ratio would be after i installed flattop pistons into my 1998 ford mustang gt with stock heads? i got mls head gaskets and xe268h-14 comp cams with springs.

RandoGT · April 18th, 2008, 12:35 PM

while everyone's on compression, what's a Mach 1's stock compression?

banned · April 21st, 2008, 03:05 AM

Originally Posted by Darrell

If you pay $10 a gallon for 100 octane I have a bridge to sell you....

I pay that for C16. 110 out of the pump goes for $3.50 to $4.00 every where I've seen it.

yeah i just bought c-16 for 7

Goblin · May 5th, 2008, 08:05 PM

Originally Posted by RandoGT

while everyone's on compression, what's a Mach 1's stock compression?

10:1

November 4th, 2007, 11:32 AM	#23
00vabchgt MM Fanatic 2000 Mustang GT Join Date: Nov 2006 Location: Virginia Beach, VA Posts: 3,875	after a PI swap with the stock pistons, you should be looking at about a 10.5:1 compression ratio, assuming your bore is still stock. going to a larger size piston dish will lower your compression ratio, as will having the heads worked to include a larger size combustion chamber. __________________ Submariners Do It Deeper

November 4th, 2007, 06:57 PM	#25
00vabchgt MM Fanatic 2000 Mustang GT Join Date: Nov 2006 Location: Virginia Beach, VA Posts: 3,875	yeah, the non PI stangs had 11cc pistons with a 51cc combustion chamber that made for a 9.3:1 compression ratio. with the PI heads, you have a 42cc combustion chamber which, when combined with the 11cc dish pistons yield a compression ratio of 10.52:1, assuming a standard bore of 3.551 inches. if you went to a 17cc dish piston like stock on the PI stangs, you'd be looking at about a 9.7:1 compression ratio... __________________ Submariners Do It Deeper

November 5th, 2007, 09:24 AM	#27
00vabchgt MM Fanatic 2000 Mustang GT Join Date: Nov 2006 Location: Virginia Beach, VA Posts: 3,875	i talked to the guys at Sean Hyland Motorsport about 2 weeks ago. i told the guy my plans for the build included a centri blower going on the car, but not for about another year or so. i told him i was looking to make about 500rwhp. he recommended going 17cc on the pistons, which is actually the same size dish on the stock PI motor pistons. it really depends on th amount of boost you plan on running. as for the nitrous, i'm not really sure. i don't plan on messing around with spray on a daily driver... i'll see what i can find out for you... __________________ Submariners Do It Deeper

April 17th, 2008, 01:49 PM	#29
suprajay79 Regular 2001 Mustang GT 13.9 @ 100.7 Join Date: Jan 2008 Location: Mountain Home, Idaho Posts: 189	Real quick and easy way to lower your compression a few points is to install a thicker head gasket... not sure of all the options though. __________________ 2001 Mustang GT 5-Speed, Oxford White; Chrome FR500s (17x10.5 in back), Chin spoiler, 20/5% tint Mods: K&N FIPK Flowmaster Catback BBK Underdrive pulleys 3.73 Gears (not installed) Eibach Pro-Kit BBK Plenum & 70mm TB SCT Livewire 91 oct. tune

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November 4th, 2007, 09:35 AM	#21
87StangLX Regular Join Date: Jul 2007 Posts: 200	prolly jus as long as i dont go to far over 400hp though. dont want a cracked block :wink

November 4th, 2007, 11:20 AM	#22
RandoGT Enthusiast 1998 Mustang GT Need to hit the track Join Date: May 2007 Location: Katy, TX Posts: 813	well how do you lower the compression after a full PI swap on a 98 GT? i've been wanting to know this forever but no one has ever answered it

November 4th, 2007, 03:36 PM	#24
RandoGT Enthusiast 1998 Mustang GT Need to hit the track Join Date: May 2007 Location: Katy, TX Posts: 813	so a more cc, so to say, piston? like 18cc, 19cc, etc. get what i'm saying? and working the heads? porting?

November 5th, 2007, 01:04 AM	#26
RandoGT Enthusiast 1998 Mustang GT Need to hit the track Join Date: May 2007 Location: Katy, TX Posts: 813	ah marvelous. after 20 times of asking that question it's finally answered. and would that be a good CR for goin blown? also, if i decide that i wanna go nitrous, would any more compression blow my engine? cause i heard nitrous loves compression

April 1st, 2008, 09:59 PM	#28
pimpdout98gt Regular 1998 Ford Mustang GT Join Date: Apr 2008 Location: Clarksville, TN. Posts: 50	well after calculation my car supposedly has 10:7.1 compression cause i install flattop pistons. i only get detonation when im really pulling hard. btu i have a paxton supercharger and this car really pulls hard. i was able to pull 427 ft. lbs. of torque at 3900 rpm and 6 p.s.i.

April 18th, 2008, 06:01 AM	#31
pimpdout98gt Regular 1998 Ford Mustang GT Join Date: Apr 2008 Location: Clarksville, TN. Posts: 50	anyone know what my compression ratio would be after i installed flattop pistons into my 1998 ford mustang gt with stock heads? i got mls head gaskets and xe268h-14 comp cams with springs.

April 18th, 2008, 12:35 PM	#32
RandoGT Enthusiast 1998 Mustang GT Need to hit the track Join Date: May 2007 Location: Katy, TX Posts: 813	while everyone's on compression, what's a Mach 1's stock compression?

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