Compression test - what range values?
Hi guys, 2014 Nismo 370z here with 34k miles. I’ve been contemplating selling it for a while and think I’ll just hold on to it for now. Still having a
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 04-23-2018, 05:00 PM | #1 (permalink) |
Rahul718 Base Member Join Date: Nov 2013 Location: NYC Posts: 233 Drives: Nismo Z Rep Power: 12  |  Compression test - what range values? Hi guys, 2014 Nismo 370z here with 34k miles. I’ve been contemplating selling it for a while and think I’ll just hold on to it for now. Still having a lot of fun with it. I figured if I’m keeping it then I want to do a compression and leak down test. I don’t have a service manual so I’m not sure what psi range the compression should be aside from the universal rule that all cylinders should be within 10% of each other. What is the range I should be shooting for? For leak down I’m hoping for 7% or less. It’ll be real interesting to see what numbers I get! Thanks in advance |
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| 04-24-2018, 11:03 AM | #2 (permalink) |
| Rahul718 Base Member Join Date: Nov 2013 Location: NYC Posts: 233 Drives: Nismo Z Rep Power: 12 | Bump |
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| 04-24-2018, 11:35 AM | #3 (permalink) |
SouthArk370Z Premium Member   Join Date: Nov 2010 Location: South Arkansas Posts: 8,435 Drives: 2014 Challenger Rep Power: 324198  | Give it a little more time and someone will probably provide a number for you. Assuming the car has been taken care of, you should have more than one good cylinder (probably six of them) for comparison. 34K miles ain't nothin' nowadays. The FSM has gotten hard to find but it would be well worth the time and effort to search for a copy. __________________ Steering Lock Links - Search The370Z Bookmarklet - FSM @ NICOclub Mankind has progressed past the need for war but we haven't evolved that far. - NachoMahma |
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| 04-24-2018, 12:45 PM | #4 (permalink) |
| jmroy6 Base Member Join Date: Sep 2015 Location: CT Posts: 179 Drives: Spirited Rep Power: 235 | Compression values themselves are not as important as the % ranging between cylinders. i say this because you can get different reading with different gauges on the same cylinder. From my understanding these motors should be anywhere from 180-220psi on a wet or hot test depending on gauge and motors condition and a good rule of thumb is 10% between highest and lowest cylinder. I just did a cold test on my motor and ranged from 160-170 psi with a range of 6% between my highest and lowest cylinder. Unfortunately i have not done a wet or holt test, but those number should only go up. Husam2012 can chime in, i think he was reading 220psi on his new (Stock) motor. __________________ 2012 370z GTM SC |
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| 04-24-2018, 12:48 PM | #5 (permalink) |
| Rahul718 Base Member Join Date: Nov 2013 Location: NYC Posts: 233 Drives: Nismo Z Rep Power: 12 | Alright! I was able to track down the FSM online, although it seems like it’s for a non-Nismo. Not sure there should be a difference between regular trims And a Nismo in this respect - correct me if I’m wrong. See attached. It looks like the range should be 242 - 341, if I’m reading this correctly Attached Images  | 98614EBC-37FA-45E0-8D86-2C374523FDAD.jpg (72.0 KB, 120 views) | |
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| 04-24-2018, 01:26 PM | #6 (permalink) |
| Spooler A True Z Fanatic Join Date: Jun 2014 Location: Ga Posts: 13,806 Drives: 2013 Nismo 370z Rep Power: 2684392 | Quote: Originally Posted by Rahul718  Alright! I was able to track down the FSM online, although it seems like it’s for a non-Nismo. Not sure there should be a difference between regular trims And a Nismo in this respect - correct me if I’m wrong. See attached. It looks like the range should be 242 - 341, if I’m reading this correctly | Yeap, that is correct. Minimum should be 178. |
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| 05-21-2020, 11:11 AM | #7 (permalink) |
RanRich Enthusiast Member  Join Date: Mar 2015 Location: St. Louis Posts: 425 Drives: 09 PG Sport M6 Rep Power: 3372 | Bumping this thread to inquire about compression on higher mileage engines. I have a 2009 with 112K miles on it, that's been tuned for about 50K. Just got a compression test and all cylinders were at 150, give or take a couple psi. I don't know if this was done hot or cold, and was just done at my local shop vs. a dealership. A bit worried about those numbers given what I've just read even though they're consistent and the car seemingly runs and drives just fine. The shop (which has a lot of experience building their own and working on tuned cars) didn't sound at all concerned over the phone either. Is this engine on its way out or am I worrying about nothing? __________________ AAM | Dynosty | Ecutek | Eibach | Hawk | H&R | Nismo | Stillen | Stoptech | Z1 Last edited by RanRich; 05-21-2020 at 11:40 AM. Reason: clarified running condition |
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| 05-21-2020, 12:32 PM | #8 (permalink) |
| ZoomZ Track Member Join Date: Jan 2017 Location: Vancouver, BC Posts: 760 Drives: 17' 370Z Nismo Rep Power: 40617 | Quote: | Originally Posted by RanRich Bumping this thread to inquire about compression on higher mileage engines. I have a 2009 with 112K miles on it, that's been tuned for about 50K. Just got a compression test and all cylinders were at 150, give or take a couple psi. I don't know if this was done hot or cold, and was just done at my local shop vs. a dealership. A bit worried about those numbers given what I've just read even though they're consistent and the car seemingly runs and drives just fine. The shop (which has a lot of experience building their own and working on tuned cars) didn't sound at all concerned over the phone either. Is this engine on its way out or am I worrying about nothing? | Try different gauge, and hot. Also note the FSM calls for 200 RPM for those numbers. Make sure you are on a power supply not just battery. I'm guessing 150 was taken cold. FSM calls for warmed "thoroughly" engine, Fuel depressurized/fuse out, all plugs out, ACCELERATOR PEDAL FULLY DEPRESSED, and fully charged battery (I'd use a power supply). If you get low readings still, pour some engine oil into cylinder from plug hole. take readings again, If pressure increases, you have worn rings. zz Last edited by ZoomZ; 05-21-2020 at 12:43 PM. |
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| 05-21-2020, 05:00 PM | #9 (permalink) |
Rusty Ronin Samurai - Assassin  Join Date: Dec 2011 Location: Fayettenam,Pennsyltucky Age: 68 Posts: 35,194 Drives: 2011 Nismo GM 6M Rep Power: 2684437 |  Quote: | Originally Posted by ZoomZ Try different gauge, and hot. Also note the FSM calls for 200 RPM for those numbers. Make sure you are on a power supply not just battery. I'm guessing 150 was taken cold. FSM calls for warmed "thoroughly" engine, Fuel depressurized/fuse out, all plugs out, ACCELERATOR PEDAL FULLY DEPRESSED, and fully charged battery (I'd use a power supply). If you get low readings still, pour some engine oil into cylinder from plug hole. take readings again, If pressure increases, you have worn rings. zz | Make sure that you pour an equal amount of oil in each cylinder. If not, you can get one or two cylinders reading a lot higher. ZoomZ likes this. __________________  浪人 - 殺し屋 "The Difficult Anytime, The Impossible By Appointment Only" http://www.the370z.com/members-370z-...o-journal.html |
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| 05-21-2020, 07:35 PM | #10 (permalink) |
| ZoomZ Track Member Join Date: Jan 2017 Location: Vancouver, BC Posts: 760 Drives: 17' 370Z Nismo Rep Power: 40617 | Quote: | Originally Posted by Rusty Make sure that you pour an equal amount of oil in each cylinder. If not, you can get one or two cylinders reading a lot higher. | Absolutely. Those 50ml syringes with extended nipples would work great. That way you get exact quantity and you can swirl the nozzle (as best as possible) to get even coating on cyl wall. Rusty likes this. |
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| 05-21-2020, 08:52 PM | #11 (permalink) |
| Rusty Ronin Samurai - Assassin Join Date: Dec 2011 Location: Fayettenam,Pennsyltucky Age: 68 Posts: 35,194 Drives: 2011 Nismo GM 6M Rep Power: 2684437 | Quote: | Originally Posted by ZoomZ Absolutely. Those 50ml syringes with extended nipples would work great. That way you get exact quantity and you can swirl the nozzle (as best as possible) to get even coating on cyl wall. | That's what I use. After you are done with the syringe. You have to pull it apart and wipe the oil off the rubber to keep it from swelling up. The rubber hates oil. ZoomZ likes this. __________________ 浪人 - 殺し屋 "The Difficult Anytime, The Impossible By Appointment Only" http://www.the370z.com/members-370z-...o-journal.html |
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| 01-21-2021, 10:26 PM | #12 (permalink) |
| husam2012 Track Member Join Date: Mar 2015 Location: Michigan Posts: 549 Drives: 370Z Nismo Rep Power: 9469 | Just a head up for anyone worried about their compression tests. I tested a ton of Zs recently as I work/tune them everyday and most healthy ones are around 180-190 psi. Keep in mind that most gauges vary a lot, even the same branded ones. I was able to get 220 psi on a older HF compression tester vs about 180 with a newly purchased one. Snap on tester were usually higher reading than the HF testers. __________________ Creator of the GTR TT Conversion Kit, NA Record Holder (401WHP) Ecutek Master Tuner (VQ37, VR30, VR38, B58, S55, S58) BTWTuning |
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| 01-22-2021, 11:34 AM | #13 (permalink) |
| SG4247 Track Member Join Date: Oct 2016 Location: OKC Posts: 786 Drives: 2010 touring Rep Power: 7842 | I just did mine with a new snap on compression gauge kit. This was 10 rev per test, on a stone cold motor, with 50k miles. Compression test 11/4/2020 10 cycles per #1 230 psi good plug #3 220 psi bad plug #5 228 psi really bad plug #2 250 psi good plug #4 250 psi bad plug #6 0 psi real bad plug Burned valve in #6 hole. Rusty likes this. __________________ NA on E85 - 12.402 @ 112 mph 100 shot E85 - 11.589 @ 117 mph JWT C2 cams rev Base Circle & Titan Valves |
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