Compression Test In 944

butziporsche944 · 03-12-2006, 03:37 PM

Hi I will like to make a compression test in my 944....
My friend's dad has 944s2 1989 with over 160miles on it he test his car 3 weeks ago and got 140-145 psi in all cylinders!!!!I don't know if his car is in good shape !!

So my question is what is the good shape 944 compression #psi I will test my 944 next week I will like to have a number to compare !

brandon2944 · 03-13-2006, 03:17 PM

I couldn't find my haynes to verify, but I think 160 psi. My 87 NA when I bought it had 122K and I got between 159-167 on all cylinders.

Dtchy · 03-13-2006, 04:38 PM

Alina?

WolfeMacleod · 03-13-2006, 05:11 PM

We just did my car a couple days ago.
#1 180-182
#2 185
#3 180-182
#4 185

Razorback1980 · Razorback1980's Garage

The biggest thing you look for is consistency between the cylinders. That matters more than the amount of compression unless you are just after total performance. If one cylinder is much lower than the rest, then you have some serious problem to fix in that one cylinder. The amount of compression depends on the model of car. Obviously the compression ratio is higher on an S, S2 or 951. I can't remember the compression ratio for an 86, I'll try and look that up and see. I'm going to be doing a test on my 87 but I know our engines are different compression ratios. I'll try to post when I get mine.

butziporsche944 · 03-13-2006, 09:22 PM

Thanks alot but I really will need to know right numbers I will do test by friaday
p.d So the 944 s2 of my friend's dad is bad shape he got 140-145
YOU guys posting some 160 for 944na !!
what is the amount of compression for 944na and 944s2 .?

Zero10 · 03-14-2006, 12:18 PM

The 16V engines should be ~200psi at sea level.
Above 200psi is fine, below and you're starting to see wear. Down to 140-145psi...... well... check your tester before you draw any conclusions from that. It could just read low.
On the up side, your readings are very consistent!

145psi is good for a turbo

butziporsche944 · 03-14-2006, 02:25 PM

well I just did my test today I'm very happy I got 180 psi in all cylenders , mechanic said car is perfect shape

Eldorado · 03-14-2006, 03:02 PM

how much did the test run you?

butziporsche944 · 03-14-2006, 03:14 PM

the test cost me $75.00 they also replace the old platinium plugs cars had for regular factory ones, I had to do test before install a brand new cam form web cam company , I will installing in next month $$$ (next paycheck) I will let you guys know resoults!!!

Eldorado · 03-14-2006, 04:07 PM

thanks alina!

armandodiaz · armandodiaz's Garage

I did a test on an 87 944S I'm working on, I got 220 on all 4.

SteveOH · 10-17-2011, 07:58 PM

203 PSI to 205 PSI for all four cylinders - 252 K miles, + many many DE days.
Compression was low when I let the car sit for some time: two years 11 months & 21 days, so don't be alarmed if testing after car has been sitting. Have done nothing to engine, except head gasket and 51 oil changes.

VirginiaF1 · VirginiaF1's Garage

Factory Compression PSI at sea level should be CR x 18.5....
So @ 10.2:1 CR, the original/rebuilt PSI should be:
10.2 x 18.5 = 189.
@10.9 x 18.5 = 202. etc...

I just pulled 181, 179, 180, 182 cold engine w/ no oil in CB for a 95.5% of factory spec after 25 years. Carbon buildup certainly helping but
What a car company..!

Chunkerz · Chunkerz's Garage

Quote:

Originally Posted by Razorback1980

Obviously the compression ratio is higher on an S, S2 or 951.

On the 951 the compression ratio is 8.0:1, so the ratings should be much lower than an S, S2, 968, and even a base NA.

Dean924s · Dean924s's Garage

Quote:

Originally Posted by Chunkerz

On the 951 the compression ratio is 8.0:1, so the ratings should be much lower than an S, S2, 968, and even a base NA.

This. I have developed a tool that has the capability to actually record and graph the compression cycle of a motor. IT can tell you a whole lot more about the actually condition of the motor than a standard compression test.

Here is a graph of a 83 944 motor car I tested a while back. The 83's have lower compression motors and this motor has a cam with more overlap thus the lower compression numbers.

Dean924s · Dean924s's Garage

This on the other hand is a worn out motor I tested.

The real key here is not the max compression is is what I call the snap the snap is a extreemly accurate measurement of how worn the rings / cylindars are.

This photo has the "snap" noted with a red box. As you can see it does not go back below 0 PSI. where as the motor above the end of the powerstroke results in the pressures going negitive thus indicating that the seal between the rings and the cylindar walls is poor.

There are a bunch of other "signatures" in the graphs that can tell you alot about a motor. But this is probibly the best way to really "see" the condition of the core components (cylindars, pistons rings).

Custom944 · 10-28-2012, 06:33 AM

I am just wondering when the compression test was performed if the fuel pump fuse was pulled.Because as you crank the car If your getting fuel into the cylinder it will drop the psi in the cylinder by about 15 to 20 psi.Please recheck and make sure that fuel isn't being injected into the cylinders when compression test i being performed.

baul · 06-07-2013, 10:27 AM

Hello, I just made a few compression tests on a 83 944 and the results look interesting:

Cold engine: Warm engine:
1)185 190
2)225 230
3)180 175
4)170 175

What do u think??

Dean924s · Dean924s's Garage

Something is weird there. 225 is getting up to 10.2 / 1 compression. and a 83 motor should not be anyway near that.

225 PSI is what I get on a fresh rebuild on cars with 10.25-10.5 / 1 These have cams with relitivly small overlap so it should be a close approximation to what CR you have. Are you sure that you don't have a later motor? Or ahs there been work done to the motor?