Easy DIY compression test with pics! - Page 3

FleaDog · 11-07-2008, 01:07 AM

GREAT writeup bro. posted a link to this on the DIY/how to section of iwsti.

And I dont mean to sound like an idiot, but 'cranking the engine' means depressing clutch and turning ignition key (like you're normally starting the car) and getting the engine to turn over 6 times, right?

I was gonna order this one from harbor freight for $17
http://www.harborfreight.com/cpi/cta...emnumber=95187

* Registered users of the site do not see these ads.

txl146 · 11-07-2008, 01:25 PM

Thanks... yes you are correct. Just crank the engine just like how you normally start the car.

NickVu · 11-07-2008, 01:45 PM

Quote:

Originally Posted by FleaDog

I was gonna order this one from harbor freight for $17
http://www.harborfreight.com/cpi/cta...emnumber=95187

i've used these fine in the past. be careful though; if you overtighten them into the cylinder head, the rubber hose would seperate from the metal end clamps and you'd be left with the plug end still screwed on the engine.

paintbing · 11-07-2008, 02:29 PM

Quote:

Originally Posted by bendavi17

2004 WRX
60,000 miles
Rebuilt at 50,000 miles with thick 1.2mm head gasket (long story, don't ask why)
Stage 2 + headers, intake, 06wrx injectors, catless TBE

Results:
1: 137
2: 144
3: 138
4: 142

How does this look keeping in mine that I have the thick head gasket?

It doesn't mean a thing. the ONLY thing you're really measuring, are the values compared to themselves. Your gauge could read slightly different from the next persons, and the elevation and relative barometric pressure will create a different reading as well.

According to FSM, as long as the cyl are all within 7% of each other, then you're fine.

Great writeup though.
-1 for uplugging the ignition fuse - (Plugs and coil packs alread removed =pointless to remove fuse)
+1 for unplugging the fuel relay (Below glovebox just inside passenger door - Brown wire harness)

tazswing · 11-10-2008, 05:55 PM

98,000 miles, been running the 16G for around 50k.

Results:
1: 155
2: 155
3: 145
4: 160

Time to find some more area under the curve with PnP city

ciper · 11-10-2008, 06:39 PM

Quote:

Originally Posted by BuddyWRX

You're going WOT without an air filter on!!!... am I missing something here???

Yes you are

The spark plugs are removed, the coil packs are removed and the ignition fuse is removed.

Quote:

Originally Posted by sorrowfulkiller

going wot at startup cuts fuel to the all cylinders, this is normal on al obd2 cars

Cite your source.

kellygnsd · 11-10-2008, 09:27 PM

Quote:

Originally Posted by ciper

Yes you are

The spark plugs are removed, the coil packs are removed and the ignition fuse is removed.

Cite your source.

Its standard modern EFI operation. Its called "clear flood mode" and and is an algorithm in almost 100% or modern computer controlled EFI vehicles.

DiscoGsus · 11-11-2008, 10:13 AM

Quote:

Originally Posted by T_Racer69

Its not that a cold engine will not read, it is that is will read artificially high. Because the engine is not up to temp, and things are tighter than when warm, you will see slightly inflated numbers. A warm engine simply gets an accurate reading with everything at proper operating temp, thus giving actual use conditions.

Everything else you said it correct. But when the engine is colder, all the gaps are larger, so you get an artificially low reading.

ciper · 11-12-2008, 03:23 PM

Quote:

Originally Posted by kellygnsd

Its standard modern EFI operation. Its called "clear flood mode" and and is an algorithm in almost 100% or modern computer controlled EFI vehicles.

The second google search result states

Quote:

We have often been told no fuel is injected in clear flood mode. This is not always true, many manufacturers go to a 20:1 fuel ratio and the car may start

I'm curious how Subaru handles it now!

mrbigshot · 02-04-2009, 08:04 PM

Here's the numbers I got:

2002 WRX
181,000 Miles on odo
Bone Stock - No mods

Cylinder
1 = 153
2 = 162
3 = 150
4 = 163

I bought my compression tester from harbor freight for $7!!!

o3WRXTC · 02-04-2009, 10:59 PM

Quote:

Originally Posted by txl146

I mentioned above, ".... with wide open throttle..."

why do you need to do it in WOT?? there's no real need for this imo

thats why you crank it 5-6 times to get the compression test.

imo your fouling your spark plugs when u do this. *good chance*

just my two cent

great write up tho.

meebs · 02-05-2009, 12:22 AM

Quote:

Originally Posted by o3WRXTC

why do you need to do it in WOT?? there's no real need for this imo

thats why you crank it 5-6 times to get the compression test.

imo your fouling your spark plugs when u do this. *good chance*

just my two cent

great write up tho.

oh boy.

Magnum626 · 02-05-2009, 01:32 AM

Quote:

Originally Posted by o3WRXTC

why do you need to do it in WOT?? there's no real need for this imo

thats why you crank it 5-6 times to get the compression test.

imo your fouling your spark plugs when u do this. *good chance*

just my two cent

great write up tho.

wow...just wow.

LOL, yup, you can foul your plugs going WOT.

Better put these suckers far away then..

I immediately thought of this after reading that.

http://forums.nasioc.com/forums/show....php?t=1123616

paintbing · 02-05-2009, 02:51 AM

Quote:

Originally Posted by o3WRXTC

why do you need to do it in WOT?? there's no real need for this imo

thats why you crank it 5-6 times to get the compression test.

imo your fouling your spark plugs when u do this. *good chance*

just my two cent

great write up tho.

Like has been stated above already... the plugs are out of the car.

Secondly, you should still go WOT with the throttle just to get the throttle open to allow air to be less hindered going into the motor.

Thirdly, you just need to disconnect the brown wiring harness below the glove box right next to the door. This contains the fuel pump power etc... unplugging this is like turning the pump off so that you don't wash your cylinders with gasoline and thin out your oil.

Nuff said... This resolves any nonsense about any "clear flood mode" and "standard modern EFI operation" crap.

(And it takes like 5 seconds to unplug/plug it in.)

WRXislander · 02-05-2009, 10:55 AM

Quote:

Originally Posted by Magnum626

wow...just wow.

LOL, yup, you can foul your plugs going WOT.

Better put these suckers far away then..

I immediately thought of this after reading that.

http://forums.nasioc.com/forums/show....php?t=1123616

BWAHAHAHAHAHAHAHAAHAHAA!!!!

FleaDog · 03-24-2009, 09:42 PM

bump - what happened to the pics?

txl146 · 03-24-2009, 11:23 PM

Photobucket started to put a monthly limit on bandwidth.

Photos will re-appear in March.

Magnum626 · 03-25-2009, 01:02 AM

You could always open another account.

Another question, everyone says to do it warm. How much time after the car is shutoff still considered warm? When I did mine it was too damn hot to be working on and we just waited for it to cool off.

carnz-pj-410 · 03-25-2009, 12:04 PM

Quote:

Originally Posted by ciper

The second google search result states

I'm curious how Subaru handles it now!

The injectors do not fire when cranking at WOT on Subarus

MAJRMSA · 03-25-2009, 10:32 PM

Quote:

Originally Posted by Magnum626

You could always open another account.

Another question, everyone says to do it warm. How much time after the car is shutoff still considered warm? When I did mine it was too damn hot to be working on and we just waited for it to cool off.

Well I waited like an hour after my engine was warm to do a compression test. I still got the following numbers on a 160k mile motor.

1= 168
2= 175
3= 165
4= 165

furryfootstool · 03-27-2009, 03:05 PM

here are my results from my 02 with 120k miles

1. 162
2. 165
3. 163
4. 165

will a cold compression test point out a damaged ringland? i'm getting misfires when the car is warming up, not when its at temp. any ideas?

Slowsoul · 03-27-2009, 05:09 PM

Quote:

Originally Posted by o3WRXTC

why do you need to do it in WOT?? there's no real need for this imo

thats why you crank it 5-6 times to get the compression test.

imo your fouling your spark plugs when u do this. *good chance*

just my two cent

great write up tho.

You are most certainly entitled to your wrong opinion...

This is how a compresson test is done...by the book...period.

Slowsoul · 03-27-2009, 05:11 PM

Quote:

Originally Posted by Magnum626

When I did mine it was too damn hot to be working on and we just waited for it to cool off.

Man up! A few burns aren't going to kill you.

You have about an hour to do the test.

Slowsoul · 03-27-2009, 05:14 PM

Op...is it me or did you just skip explaining how to get to the driver side coils? They are definately the harder side to deal with.

Chi_San · 03-27-2009, 05:35 PM

Having done compression tests repeatedly, on the same vehicle (V6 Toyota Corolla) with the throttle open and closed, I can say without any doubt, put the damn throttle pedal to the floor, or you will get a low reading, no matter how many times you crank the engine.

I'd also suggest pulling the fuel pump relay or disabling the fuel pump otherwise, as has been mentioned, though getting fuel in your oil isn't a big deal as the PCV system will just suck it out next time you're cruising down the freeway.

If you start the vehicle with the throttle above 80% on any modern car (ODBII), the ECU/PCM/whatever the manufacturer calls it will go into Flood clear mode. What is flood clear mode? That depends... Is the car DBW, or is it cable?

-Cable: The injectors will fire at 20% for a predetermined period of time to clear the cylinders while the engine initially starts, then go into normal operation (open or closed loop)

-DBW: Which ever computer controls the throttle angle will command the throttle plates to either the throttle position the drive is, via the gas pedal, or to a predetermined position. The computer will either cut the fuel off, or cut fuel to 20% for a pre-determined amount of time, then it will go into reguarl open or closed loop operation.

Just to clear this up: Clear Flood is another run mode, just like Open or Closed loop.

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11-07-2008, 01:07 AM	#51
FleaDog Scooby Specialist Member#: 96267 Join Date: Sep 2005 Chapter/Region: MAIC Location: West Chester Vehicle: '06 20G-XT'd STI CGM & NT03+M	GREAT writeup bro. posted a link to this on the DIY/how to section of iwsti. And I dont mean to sound like an idiot, but 'cranking the engine' means depressing clutch and turning ignition key (like you're normally starting the car) and getting the engine to turn over 6 times, right? I was gonna order this one from harbor freight for $17 http://www.harborfreight.com/cpi/cta...emnumber=95187 * Registered users of the site do not see these ads.

11-07-2008, 01:25 PM	#52
txl146 Scooby Guru Member#: 32459 Join Date: Feb 2003 Chapter/Region: Tri-State Location: NY Vehicle: 02 WRX VF34 Junior Tuned 301whp	Thanks... yes you are correct. Just crank the engine just like how you normally start the car.

11-10-2008, 05:55 PM	#55
tazswing Scooby Specialist Member#: 63767 Join Date: Jun 2004 Chapter/Region: NWIC Location: PDX Vehicle: 2009 OXT 5-spd 2011 STi hatch	98,000 miles, been running the 16G for around 50k. Results: 1: 155 2: 155 3: 145 4: 160 Time to find some more area under the curve with PnP city

02-04-2009, 08:04 PM	#60
mrbigshot Scooby Newbie Member#: 191474 Join Date: Oct 2008 Chapter/Region: BAIC Location: Sacramento Vehicle: 2002 WRX Black	Here's the numbers I got: 2002 WRX 181,000 Miles on odo Bone Stock - No mods Cylinder 1 = 153 2 = 162 3 = 150 4 = 163 I bought my compression tester from harbor freight for $7!!!

03-24-2009, 09:42 PM	#66
FleaDog Scooby Specialist Member#: 96267 Join Date: Sep 2005 Chapter/Region: MAIC Location: West Chester Vehicle: '06 20G-XT'd STI CGM & NT03+M	bump - what happened to the pics?

03-24-2009, 11:23 PM	#67
txl146 Scooby Guru Member#: 32459 Join Date: Feb 2003 Chapter/Region: Tri-State Location: NY Vehicle: 02 WRX VF34 Junior Tuned 301whp	Photobucket started to put a monthly limit on bandwidth. Photos will re-appear in March.

03-25-2009, 01:02 AM	#68
Magnum626 Scooby Guru Member#: 62856 Join Date: May 2004 Chapter/Region: Tri-State Location: McDowells Vehicle: MBP SQC#197 Stockpiling parts...	You could always open another account. Another question, everyone says to do it warm. How much time after the car is shutoff still considered warm? When I did mine it was too damn hot to be working on and we just waited for it to cool off.

03-27-2009, 03:05 PM	#71
furryfootstool Scooby Specialist Member#: 200526 Join Date: Jan 2009 Chapter/Region: SWIC Location: Queen Creek	here are my results from my 02 with 120k miles 1. 162 2. 165 3. 163 4. 165 will a cold compression test point out a damaged ringland? i'm getting misfires when the car is warming up, not when its at temp. any ideas?

03-27-2009, 05:14 PM	#74
Slowsoul Scooby Specialist Member#: 126686 Join Date: Sep 2006 Chapter/Region: South East Location: Greenville, SC Vehicle: 2002 Impreza, WRX World Rally Blue	Op...is it me or did you just skip explaining how to get to the driver side coils? They are definately the harder side to deal with.

03-27-2009, 05:35 PM	#75
Chi_San Scooby Guru Member#: 53558 Join Date: Jan 2004 Chapter/Region: NWIC Location: Deadford, OR Vehicle: 2002 WRX Wagon Silver	Having done compression tests repeatedly, on the same vehicle (V6 Toyota Corolla) with the throttle open and closed, I can say without any doubt, put the damn throttle pedal to the floor, or you will get a low reading, no matter how many times you crank the engine. I'd also suggest pulling the fuel pump relay or disabling the fuel pump otherwise, as has been mentioned, though getting fuel in your oil isn't a big deal as the PCV system will just suck it out next time you're cruising down the freeway. If you start the vehicle with the throttle above 80% on any modern car (ODBII), the ECU/PCM/whatever the manufacturer calls it will go into Flood clear mode. What is flood clear mode? That depends... Is the car DBW, or is it cable? -Cable: The injectors will fire at 20% for a predetermined period of time to clear the cylinders while the engine initially starts, then go into normal operation (open or closed loop) -DBW: Which ever computer controls the throttle angle will command the throttle plates to either the throttle position the drive is, via the gas pedal, or to a predetermined position. The computer will either cut the fuel off, or cut fuel to 20% for a pre-determined amount of time, then it will go into reguarl open or closed loop operation. Just to clear this up: Clear Flood is another run mode, just like Open or Closed loop.