Real life Compression Test Results

Discussion in 'Gen 3 Prius Technical Discussion' started by DTKim, Aug 14, 2016.

  1. DTKim

    DTKim Member

    Joined:
    Apr 11, 2012
    51
    31
    5
    Location:
    NJ
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Advanced
    So, there seems to be conflicting reports on what the cylinder compression should be on the Gen 3 Prius. wanted to get a poll of real world results. I figure there's a few variables so it's good to identify a few extra details a poll doesn't cover so here's a survey format instead:

    1. Year and Mileage.
    2. Compression Results (PSI). List all four cylinders.
    3. Method of "cranking". Maintenance mode, with Techstream Compression Test mode, manually cranking in regular mode, etc.
    4. Warm or Cold. Fuel injectors plugged or unplugged.
    5. What tool (brand/model).
    6. Any underlying issues (reason why you were checking).
    7. Special notes (Did you pour oil in after first round to see if it went higher, engine was replaced, head gasket replaced, etc.)

    Reason I ask is that AllData (from another thread) says 118 PSI is Normal/Ideal and 89.5 psi is minimum allowed. Toyota says 199 psi is Normal/Ideal and 157 psi is minimum allowed. Both say variations up to 14.5/14.2, respectively, is allowed. Toyota has a special compression test mode via Techstream and I'm wondering if that allows for a higher results or not. Also trying to see if the HF tester I bought is way off or accurate.

    I'll start off posting the two methods I did. Only real variation is that I continued to crank until it stopped climbing (roughly 15-20 seconds of cranking and pedal to the floor) for the second round as opposed to three rounds of getting the engine to turn over (roughly 8-10 seconds).

    1. 2010 Prius.
    2. First Round: 111 - 114 - 112 - 114 and Second Round: 144 - 147 - 145 - 146
    3. Manually cranking in regular mode.
    4. Warm with fuel injectors left plugged in.
    5. Harbor Freight Pittsburg Quick Disconnect Compression Tester #62622
    6. Feels underpowered vs. my Gen 2, but it's been a few months since I last drove a Gen 2 so it could be a red herring. Also, had intermittent misfire on #2 and #4 cylinders, knocking at startup and slight coolant drop between warm ups and cooldowns. I did this test after cleaning out the PCV, EGR, Intake Manifold, cylinder head, and intake valves. No more knocking (for now) and monitoring the coolant levels.
    7. I did not pour oil to see if compression goes higher. May do that later this week after I confirm the knocking at startup is gone and coolant levels are stable.
     
    privilege and Robert Holt like this.
  2. Robert Holt

    Robert Holt Senior Member

    Joined:
    Aug 3, 2013
    1,312
    876
    0
    Vehicle:
    2012 Prius
    Model:
    Three
    Have not done Prius, but with all previous cars and motorcycles I cranked until the pressure stabilized.
    On Aircraft used a leak down method with a pressurized air feed through an calibrated nozzle, IIRC .
     
  3. DTKim

    DTKim Member

    Joined:
    Apr 11, 2012
    51
    31
    5
    Location:
    NJ
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Advanced
    So, here's more confusing data out there. According to a TIS doc, the 2ZR-FXE Compression should be the same as what AllData says: 118PSI / 89.5 PSI Min / 14.5 PSI Max Variance. This doc is dated 6/9/2016 (2 months ago) and for inspecting the engine, including doing a compression test through Techstream:
    https://techinfo.toyota.com/t3Portal/document/rm/RM1290U/xhtml/RM000002ZLZ00ZX.html?sisuffix=ff&locale=en&siid=1471404494286

    Here's the doc that says 199 PSI, dated 10/2015:
    https://attachments.priuschat.com/attachment-files/2015/10/95555_2010_Toyota_Prius_Repair_Manual_-_On-Vehicle_Inspection.pdf

    So, I'm officially confused since my first run was 111-114 range with a few short cranks, which is typically enough for most cars, but this is an Atkitson cycle so maybe it requires longer cranking? Instructions say to do it as quickly as possible... lol Now my longer crank attempt got me to 140's. So I'm either slightly off the high for lower spec with the first attempt or really low, below minimum, on the higher spec on the second attempt.

    Last thing it could be is a very inaccurate gauge, but I don't want to entertain that right now. Good thing is that it's even compression throughout. Anyone have any input from their experience?
     
  4. Robert Holt

    Robert Holt Senior Member

    Joined:
    Aug 3, 2013
    1,312
    876
    0
    Vehicle:
    2012 Prius
    Model:
    Three
    Did you warm the engine thoroughly before the test? Very important!! Cold engine will give lower pressures than really true. But getting plugs out when engine is hot is a real pita.

    From your second link, I read that
    1. Standard compression pressure:
      1373 kPa (14.0 kgf/cm2, 199 psi) or more Minimum pressure:
      1079 kPa (11.0 kgf/cm2, 157 psi)
      Pressure difference between each cylinder: 98 kPa (1.0 kgf/cm2, 14.2 psi) or less

      So your later 144 pressures are low.
      Did you put a bit of oil in the cylinder and recheck the pressures as the PDF recommended? If pressure comes up to normal, worn rings are likely; if pressure stays low burned valves are likely. But please make sure gauge is calibrated so you are working with accurate data.
     
  5. DTKim

    DTKim Member

    Joined:
    Apr 11, 2012
    51
    31
    5
    Location:
    NJ
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Advanced
    The second link is an older spec. The first link is the newer spec. I'm curious if there's different readings if you do it with TechStream in compression test mode and without it, they don't expect as high of a number. All tests were hot and not a problem. I'm aware of the oil test, but I'm even across the board so before I pour oil to be burned in the head, I'd rather get actual results from other users with their equipment. I know there's faulty gauges out there so it may be reading high/low, but still want to get feedback.
     
  6. theorist

    theorist Member

    Joined:
    Jan 9, 2006
    365
    11
    0
    Location:
    Lexington, MA
    Thank you for starting this. Here is my data for my Generation 2 Prius.

    1. 2006 Prius with 145,000 miles
    2.
    140,145,145,? - Dry with throttle wide open (failed to record cylinder 4, but recall it was comparable),
    178,171,170,172 - wet with throttle wide open (with a teaspoon of oil squirted through each spark plug hole)
    3. manually cranked the engine without techstream, vci or anything like that. (i did neglect to press the gas/accelerator pedal but I did see that the throttle opened fully. (I removed the air filter housing to better access the plugs, injectors, and pcv valve.)
    4. slightly warm engine (about a half hour after driving.) fuel injectors disconnected
    5. OEM compression test kit from Autozone
    6. Car was burning nearly a quart of oil every 1,000 miles. OBD kept throwing a P0420 for an ineffective catalytic converter. I hoped to determine where oil was entering the cylinders. (Apparently past worn rings.)
    7. When I first tried measuring the compression, I failed to notice that a plastic bag I'd placed over the throttle intake was nearly sealing it during cranking, preventing much air from entering the engine. Before I corrected this my compression measurements were 128, 125, 114, 115 without oil added to the cylinders. Again, these are for the 1.5L engine in the Gen 2 Prius.

    I cannot find specs for what the gen 2 compression measurements should be. I'm not sure how comparable they'd be as I did a manual test without techstream or vci.

    Do these wet and dry numbers suggest that the engine is worn but still has quite a bit of life in it? How many miles more do you think this engine will last before it will not perform reliably and pass emissions tests? Should I start planning now to replace the engine or sell the car to someone prepared to do this?
     
    DTKim likes this.
  7. Norcal2

    Norcal2 Junior Member

    Joined:
    May 10, 2017
    23
    9
    0
    Location:
    Sacramento
    Vehicle:
    2015 Prius v wagon
    Model:
    Five
    Just had my 2015 gen 3 Prius V5 in for its 75000 mile service had a time cover oil leak that was fixed under warranty I also replaced the plugs and had a compression and leakdown test done, by the dealer here are my numbers:
    Cyl 1 124 psi 96% Cyl2 122psi 96% Cyl3 121psi 95% Cyl4 121psi 94% so Cyl 4 is the lowest of the bunch has anyone else have figures also? I bought this used CPO and have done all the recommended services fluid changes and use synthetic oil ...
     
    DTKim and GrGramps like this.
  8. Robert Holt

    Robert Holt Senior Member

    Joined:
    Aug 3, 2013
    1,312
    876
    0
    Vehicle:
    2012 Prius
    Model:
    Three
    IIRC, the leak down type of compression test would have different results depending on the size of of the orifice in the high-pressure air supply line. Thus, that result may not be directly comparable to the old-fashioned pressure-gauge-in-sparkplug-socket type of compression measurement (which is the type I have the most experience with). @DTKim cited two standards for the compression results, but I could only access the earlier PDF of the repair manual procedure , not the newer official Toyota techinfo version he cited as it is behind a paywall. I have not done this test on our 2012 hatchback so I hope some others will chime in with their results for the 2010-2015 Prius models.
     
    DTKim likes this.
  9. Grit

    Grit Senior Member

    Joined:
    Aug 22, 2017
    5,302
    3,740
    1
    Location:
    Wilkes Land
    Vehicle:
    2012 Prius
    Model:
    Four
    Glad to see “real life” data that’s not like the typical fake results posted on here
     
    DTKim likes this.
  10. Nor'easter

    Nor'easter Member

    Joined:
    Nov 16, 2019
    151
    91
    0
    Location:
    New Hampshire
    Vehicle:
    2010 Prius
    Model:
    II
    I tested my 2010 Prius using Techstream/Hybrid Drive/Active Test/Compression Test. Engine was warmed to 185F coolant temp with windshield wiper cowl removed, so plugs could be removed quickly. Car has 121k miles, has always been on synthetic oil, it consumes no oil to speak of. Results: 132, 135, 128, 130 psi. Leakdown numbers pending.
     
    DTKim likes this.
  11. Nor'easter

    Nor'easter Member

    Joined:
    Nov 16, 2019
    151
    91
    0
    Location:
    New Hampshire
    Vehicle:
    2010 Prius
    Model:
    II
    Using OTC 5609 leakdown tester, engine warm... 100/99+, 100/99+, 100/99, 100/99+. On all four, a tiny hiss is audible at the oil filler cap.

    Conclusion: "199 psi" specification is crazy wrong, and 118 psi spec is wrong too. Inspection of all four cylinders shows everything clean and dry.
     
    Mendel Leisk and DTKim like this.
  12. DTKim

    DTKim Member

    Joined:
    Apr 11, 2012
    51
    31
    5
    Location:
    NJ
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Advanced
    Thanks for the contribution to the thread. Looks like, depending on method, age, tool used, and how long it's cranked for, anything between 110-150 is about right for Gen 3.
    Question about the techstream and OTC tool you used. Did that automatically crank/turn over the engine for the tests? If so, how many times did it crank for each tool? Wondering if your low numbers for OTC was because it only cranked a couple times vs. techstream vs. me manually cranking.
     
  13. Nor'easter

    Nor'easter Member

    Joined:
    Nov 16, 2019
    151
    91
    0
    Location:
    New Hampshire
    Vehicle:
    2010 Prius
    Model:
    II
    The OTC tool isn't a compression tester, it's a leak down tester (google is your friend -- I don't have time to go find a description right now). What it is showing is that my engine is basically perfect (it's coming out of the car shortly for other reasons, but that's a whole 'nother story (transmission input damper problem)).
     
    Mendel Leisk likes this.
  14. DTKim

    DTKim Member

    Joined:
    Apr 11, 2012
    51
    31
    5
    Location:
    NJ
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Advanced
    Ah, I read that too quickly. Did you recall how many cranks from the Techstream test?
     
  15. Nor'easter

    Nor'easter Member

    Joined:
    Nov 16, 2019
    151
    91
    0
    Location:
    New Hampshire
    Vehicle:
    2010 Prius
    Model:
    II
    I set things up so I could read the gauge while cranking, and I cranked until the gauge topped out... plus a couple extra to be certain. I didn't count the compression strokes, something like 8 - 10. Six seconds or so of cranking.
     
Loading...