So, I've been thinking...

Chris951 · September 2nd, 2009, 02:07 AM

I remember a couple months ago I did a compression test on my car and all of my cylinders were at 150-160psi. Now, that seemed a little high to me for a car with more than 150k miles on it. I've always ran 87 octane in my car and it's always felt like it was lacking some power, even with the 4.10's. And it used to backfire through the intake but it hasn't since I did a tune up. But it always would backfire when I would shift from 2nd to 3rd on WOT runs. I know I need to check my timing, but last week I decided to run 91 in my car and it doesn't backfire at all now on WOT runs and the exhaust smells "cleaner" if that makes sense. But back to the compression... I've been reading up on compression ratio's. And at roughly just over 1000ft sea level atmospheric pressure would be about 14.2psi. So my compression of 155psi divided by the atmospheric pressure would come out to a ratio of 10.915 rounded to 10.92 or 10.9:1. Does that sound about right? Stock ratio is 9.5:1 correct? This comes from a theoretical thermodynamic equation. Psi readings from a compression gauge are related to compression ratio so this has to be fairly close.

So, with all that, does my gas issue sound like it solves my problem because I have raised compression? Maybe its not a timing issue at all?

What do you guys usually get in psi a stock engine using the compression tester? What do you guys get in psi that know your compression ratio?

93mustank · September 2nd, 2009, 11:39 AM

Your issue is you dont know enough and are trying to figure out shit by throwing random numbers around....

now on WOT runs and the exhaust smells "cleaner" if that makes sense

Are you hanging off of the back of the bumper with your nose in the exhaust pipe while a buddy hits it WOT ????????????????????

So, I've been thinking...

You should do this less often

I know I need to check my timing

Get off your lazy ricer ass and get a Timing light...if you dont own one do not drive a 5.0

MustangMatt96GT · September 2nd, 2009, 11:58 AM

YOu cannot use the compression testing numbers to calculate a compression ratio...

my engine, has 11.5:1 compression and a nitrous cam in it with nitrous rings... what does my engine that has maybe 50-60 passes on it(brand new as of two months ago) read? well it read 140-145 about a month ago... and i can tell you that the motor is strong and the rings are nice in there...

Overlap of the cam causes alot of issues...

baine21225 · September 2nd, 2009, 12:13 PM

decent gas does wonders

grnstang · September 2nd, 2009, 01:16 PM

Originally Posted by baine21225

decent gas does wonders

makes ppl think their car is faster

Chris951 · September 2nd, 2009, 01:59 PM

Originally Posted by 93mustank

Your issue is you dont know enough and are trying to figure out shit by throwing random numbers around....

Are you hanging off of the back of the bumper with your nose in the exhaust pipe while a buddy hits it WOT ????????????????????

I just thought it would be related in a way and was asking a question.

I have dumps and it's really loud and is accompanied by a big cloud of black smoke in my rear-view mirror

Chris951 · September 2nd, 2009, 02:00 PM

Originally Posted by grnstang

makes ppl think their car is faster

Not faster, running better

baine21225 · September 2nd, 2009, 02:06 PM

you need to check your timing, if its advanced and your running 87 then that could be your problem.....that you need to be running 92-93

Chris951 · September 2nd, 2009, 03:24 PM

Originally Posted by baine21225

you need to check your timing, if its advanced and your running 87 then that could be your problem.....that you need to be running 92-93

Yeah I know. I just dont have any money to do that right now. My checks are being AR'd from the cost of my oil pump and everything I had done so they're almost being cut in half...

93hatch · September 2nd, 2009, 03:39 PM

cant check compression like that dude, you have to fill the cylinder with water then put a compression tester gauge in the spark plug hole and test it

TheBrat · September 2nd, 2009, 03:41 PM

[QUOTE=93mustank;2281673]Your issue is you dont know enough and are trying to figure out shit by throwing random numbers around....

Are you hanging off of the back of the bumper with your nose in the exhaust pipe while a buddy hits it WOT ????????????????????

You should do this less often

Get off your lazy ricer ass and get a Timing light...if you dont own one do not drive a 5.0

jamilla · September 2nd, 2009, 10:53 PM

Originally Posted by 93hatch

cant check compression like that dude, you have to fill the cylinder with water then put a compression tester gauge in the spark plug hole and test it

Chris951 · September 3rd, 2009, 02:24 AM

[quote=TheBrat;2281936]

Originally Posted by 93mustank

Your issue is you dont know enough and are trying to figure out shit by throwing random numbers around....

Are you hanging off of the back of the bumper with your nose in the exhaust pipe while a buddy hits it WOT ????????????????????

You should do this less often

Get off your lazy ricer ass and get a Timing light...if you dont own one do not drive a 5.0

ricer ass? so, with your logic, everyone who owns and daily drives a 5.0 like me and doesn't have enough money to buy a timing light is a ricer? I must be a ricer then. I have other expenses to worry about first. I asked a simple question and everyone decided to be an e-thug. cool guys.

R0B0T · September 3rd, 2009, 03:00 AM

you have other expenses to worry about first instead of a 40 dollar timing light from sears that will help diagnose a problem with your motor? well when you blow your motor up again don't come whining to us.

until then, enjoy the problems and have fun stabbing in the dark.

Chris951 · September 3rd, 2009, 04:33 AM

Originally Posted by R0B0T

you have other expenses to worry about first instead of a 40 dollar timing light from sears that will help diagnose a problem with your motor? well when you blow your motor up again don't come whining to us.

until then, enjoy the problems and have fun stabbing in the dark.

Yes. Im still paying off the $600 bill for the oil pump. with that, my checks have been $280 so this month I mad a whole $560. minus ~$200 for gas a month, $75 phone bill, $150 for insurance, maybe like $100 a month on cigs. And I have to pay a $66 ticket for no seatbelt and give my mom $50 for the electricity bill. My next check should be normal $550 then I can get one.

And my car runs fine now with the 91 so im pretty sure my timing is advanced. i mean, why else would it run better on higher octane gas right? and i didn't blow my motor up so there wouldn't be an "again". My engine has over 150k on it and that was the original oil pump and shaft.

baine21225 · September 3rd, 2009, 10:23 AM

quit smoking

93mustank · September 3rd, 2009, 11:20 AM

Originally Posted by Chris951

with your logic, everyone who owns and daily drives a 5.0 like me and doesn't have enough money to buy a timing light is a ricer?

Well....yes

baine21225 · September 3rd, 2009, 01:16 PM

Originally Posted by 93mustank

Well....yes

I broke mine a couple weeks ago, but am going to get another off of ebay when I need it....where does that put me?

93mustank · September 3rd, 2009, 01:59 PM

Originally Posted by baine21225

I broke mine a couple weeks ago, but am going to get another off of ebay when I need it....where does that put me?

Puts you in the same place I am in....Just broke mine....advanced knob broke off.....

Not going to buy a new one..... I am lightining quick with a flash light and I will strip the 1 plug wire and grab it with my hand

grnstang · September 3rd, 2009, 03:05 PM

Originally Posted by 93mustank

Puts you in the same place I am in....Just broke mine....advanced knob broke off.....

Not going to buy a new one..... I am lightining quick with a flash light and I will strip the 1 plug wire and grab it with my hand

you are cracking me up today hahahahhaa

September 2nd, 2009, 02:07 AM	#1
Chris951 Hardcore Enthusiast 1991 mustang 5.0 Join Date: Aug 2007 Location: Mesa, AZ Posts: 1,933 iTrader: 0 reviews	So, I've been thinking... I remember a couple months ago I did a compression test on my car and all of my cylinders were at 150-160psi. Now, that seemed a little high to me for a car with more than 150k miles on it. I've always ran 87 octane in my car and it's always felt like it was lacking some power, even with the 4.10's. And it used to backfire through the intake but it hasn't since I did a tune up. But it always would backfire when I would shift from 2nd to 3rd on WOT runs. I know I need to check my timing, but last week I decided to run 91 in my car and it doesn't backfire at all now on WOT runs and the exhaust smells "cleaner" if that makes sense. But back to the compression... I've been reading up on compression ratio's. And at roughly just over 1000ft sea level atmospheric pressure would be about 14.2psi. So my compression of 155psi divided by the atmospheric pressure would come out to a ratio of 10.915 rounded to 10.92 or 10.9:1. Does that sound about right? Stock ratio is 9.5:1 correct? This comes from a theoretical thermodynamic equation. Psi readings from a compression gauge are related to compression ratio so this has to be fairly close. So, with all that, does my gas issue sound like it solves my problem because I have raised compression? Maybe its not a timing issue at all? What do you guys usually get in psi a stock engine using the compression tester? What do you guys get in psi that know your compression ratio? Last edited by Chris951; September 2nd, 2009 at 02:29 AM.

September 2nd, 2009, 11:58 AM	#3
MustangMatt96GT Proud American 1996 Mustang GT 10.76 @ 122 with d/a of 8365 ft Join Date: Dec 2006 Location: Lakewood, CO Posts: 10,168 iTrader: 3 reviews	YOu cannot use the compression testing numbers to calculate a compression ratio... my engine, has 11.5:1 compression and a nitrous cam in it with nitrous rings... what does my engine that has maybe 50-60 passes on it(brand new as of two months ago) read? well it read 140-145 about a month ago... and i can tell you that the motor is strong and the rings are nice in there... Overlap of the cam causes alot of issues... __________________ RIP Travis Billings Special Thanks to: Andrews Racing Transmissions Baseline Suspensions Blown Small Block Ford with a hole in the block. 9.5 Dart Block 400 CI being saved for. Just because you can fuck a cactus doesn't mean you should. Never Lift Racecars

September 2nd, 2009, 12:13 PM	#4
baine21225 MM Fanatic Join Date: Jun 2007 Location: Baltimore, MD Posts: 4,338 iTrader: 1 reviews	decent gas does wonders __________________ "Whip out your dick you'll either get it sucked or get smacked..." "That's how Dad did it, that's how America does it... and it's worked out pretty well so far..."

September 2nd, 2009, 02:06 PM	#8
baine21225 MM Fanatic Join Date: Jun 2007 Location: Baltimore, MD Posts: 4,338 iTrader: 1 reviews	you need to check your timing, if its advanced and your running 87 then that could be your problem.....that you need to be running 92-93 __________________ "Whip out your dick you'll either get it sucked or get smacked..." "That's how Dad did it, that's how America does it... and it's worked out pretty well so far..."

September 2nd, 2009, 03:39 PM	#10
93hatch Banned 1992 Lx 11.39@119.24 Join Date: Jan 2008 Location: Az Posts: 11,665 iTrader: 0 reviews	cant check compression like that dude, you have to fill the cylinder with water then put a compression tester gauge in the spark plug hole and test it __________________ [QUOTE=93mustank;2577445]We speed tested my right arm for quickness in shifts... So he could design the cam for proper shift recovery.[/QUOTE]

September 2nd, 2009, 03:41 PM	#11
TheBrat Regular 91 Mustang LX Fastback We shall see when she gets done.. Join Date: Jan 2008 Location: Canada Posts: 418 iTrader: 0 reviews	[QUOTE=93mustank;2281673]Your issue is you dont know enough and are trying to figure out shit by throwing random numbers around.... Are you hanging off of the back of the bumper with your nose in the exhaust pipe while a buddy hits it WOT ???????????????????? You should do this less often Get off your lazy ricer ass and get a Timing light...if you dont own one do not drive a 5.0 __________________ 2003 MazdaSPEED Protege. Lava Orange with all the go fast parts 1991 LX. 2.3T in the works. 1977 Pinto Wagon. New motor combo in the works for 2012, C4, 4.10s, 150 pill. Et. unkown 1969 Impala. Needs a resto. Im Canadian, Eh!

September 3rd, 2009, 03:00 AM	#14
R0B0T Banned 12.8@103... stock motor 11.8@113...150 shot Join Date: Apr 2008 Posts: 464 iTrader: 0 reviews	you have other expenses to worry about first instead of a 40 dollar timing light from sears that will help diagnose a problem with your motor? well when you blow your motor up again don't come whining to us. until then, enjoy the problems and have fun stabbing in the dark.

September 3rd, 2009, 10:23 AM	#16
baine21225 MM Fanatic Join Date: Jun 2007 Location: Baltimore, MD Posts: 4,338 iTrader: 1 reviews	quit smoking __________________ "Whip out your dick you'll either get it sucked or get smacked..." "That's how Dad did it, that's how America does it... and it's worked out pretty well so far..."

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