what should my compression be

[ronnies88]

I have 120 on all cylinders,car makes no power help....

 

[Ahsieh2]

For a 91, a compression of 120 is right where it should be. This is the stock motor right? Elaborate on "no power" and maybe we can help. Is it stumbling, poor fuel milage, only certain RPM, all RPMs, when cold, when hot?

 

[ronnies88]

runs great if you slowly push the gas,if you floor it it feels like a 14b car,my base ttiming is 6 degrees,43 psi fuel,no boost leak checked yesterday,fmic,hx40 turbo,750 injectors,knock counts 1-3 wot,18-19 lbs boost, a/f ratio Ive tried 11.0 -12.5 no difference also it get over 20 mpg

 

[boostonboard]

The compression from the FSM says 114psi is the minimum so i would say 120 is not fine

 

[boostonboard]

http://www.geocities.com/dsmgrrrl/FAQs/compression.htm standard compression 164 Service limit 121

 

[nuclearr]

I just put a 6-bolt 4g63t in a talon I sold two weeks ago and the compression was 180-185 across the board. Do a wet test and see if the presure jumps up, if it dose its rings, if it does not the you have bent valves or your valves are not seating and you need to have it the head rebuilt.

Wet test: Put a cap of oil in the cylinder before the test.

 

[boostonboard]

I just put a 6-bolt 4g63t in a talon I sold two weeks ago and the compression was 180-185 across the board. Do a wet test and see if the presure jumps up, if it dose its rings, if it does not the you have bent valves or your valves are not seating and you need to have it the head rebuilt.

Wet test: Put a cap of oil in the cylinder before the test.

Ronnie, If you follow my link it goes into detail on how to do what nuclearr is instructing

 

[misphit]

I just put a 6-bolt 4g63t in a talon I sold two weeks ago and the compression was 180-185 across the board.

Unless you had 2g pistons or something in that 6 bolt that compression is impossible. From the factory, 90-94 motors had 162psi compression.

 

[nuclearr]

As far as I know it was stock. And had 87000 miles on it. Looked to have 1g pistons but didnt pull them out.

 

[boosted ghost]

im having a similar kind of prob i have 160 all the way across but i have 0 in cylinder 3. do you guys think its rings or valves?

 

[GsxMan98]

120 is low it might be your problem it might not but i would follow up with a leak down test and go from there.

 

[jrohner]

The 6-bolt 4g63t's I've tested have always had 145-150 or so. 120 is kind of low, but I don't see it making your car not have any power. Once you get boost it doesn't matter that much, off boost it'll maybe be a little doggier and laggier though. I broke 400awhp with a 16G with around 100psi of compression.

That turbo won't feel amazing at that low of boost. 25+ they start to take off.

 

[Boostinsideways]

180 on a 1g is damn near impossible unless it has some internals or machine work one. Or a ####ING lot of carbon buildup.

As far as I know doing a "wet test" on an engine with dished pistons is not gonna help much, no matter what it will raise your static CR because the oil will collect in the piston.

120 is pretty damn close to the service limit. You could have worn rings, or bad valve seals, or you could be a bit off on your timing. I would do a leakdown test and report back.

 

[19Eclipse90]

Dates, gentlemen.

But to add, 180psi sounds pretty normal... for a non-turbo engine.

im having a similar kind of prob i have 160 all the way across but i have 0 in cylinder 3. do you guys think its rings or valves?

Probably the valves. A leak-down test will tell you for sure. Plus, your rings would have to be in pretty rough shape to give no compression reading at all.

 

[95AWD6Bolt]

18-19 psi on an hx40....wont even feel it until you hit 25+. Turn up the boost.

As others have said, 120 across the board is low...head gasket?

aahh seriously...who revived a 2 year old thread.

 

[boostonboard]

Wow blast from the past, but hopefully still helpful. Gosh i miss my talon i think i over did the smiley faces, but i felt the talon deserved.