Jump to content
SAU Community

Recommended Posts

I did a compression on my 94" GTR R32 it has around 73000kms on it. And all my readings were around

132-135 psi on each cylinder. Is that good or bad, if its low why is it low and how do i fix it. My car is running very nicely though. Its got an remote oil cooler and excaust and everything else seems to be stock.

Link to comment
https://www.sau.com.au/forums/topic/139742-compression-question/
Share on other sites

Nissan manual states compression on standard RB26DETT should be between approx 130 and 170 psi (9.0-12.0kg/cm2),with a maximum variation of ~ 14psi (1kg)

You could get slightly higher compression by using a heavier oil, but long term fix is to rebuild engine

So a brand new engine could hold anywhere between 130-170 psi is that what your saying?? or brand new ones usually are all the same at a higher rate???

New engine should read around 170psi, old engine 130psi, below 130 - serious problems

your engine is a bit tired, but not dead yet.

Hmmmm, so whats included in the rebuild to get my engine back to full compression? and does lower compression mean less performance, because i heard you only have a problem if one is different from the other

Unless there are deep scratches in the bores you should be able to get away with a hone and a set of new rings. If not you will need to re-bore and get oversized pistons. Lower compression normally means less performance but im not sure how low it has to be before it actually makes any noticeble difference. As the manual states possily 128psi?

73K....is that original with papers?

Edited

It is more important that they all read similar figures than 3 to be good and 3 to be bad.

If you use it daily....just drive it around and don't worry about comp. tests.

If you want to freshen up the motor,for track use and have 4 to 5K in your pocket....re-build it.

Cheers

WTF?!?! The car is obviously running absolutely fine. You have even pressure across all the cylinders and that's what's important. Plenty of gauges show different readings to each other.

All this rebuild talk is a waste of time.

I also presume you had the correct valve clearances [you checked and reset them?] before you did the test??

Take your worst cylinder, squirt a bit of heavier [say] gear oil in it with an oil can, and then do your compression test again.

If it bumps up to +150psi, then its rings/bore/pistons. If it doesn't change much, then its valves/guides.

Do this on a cold motor.

Thats if your curious to know!

Valve clearence ?? nah i did exactly what the service manual says accept i didnt turn the fuel pressure switch off. They all came out even around 135psi. i spoke to 2 guys today 1 at Bel Garage (regents park) he said it sounded fine & if they all came out even you dont have to worry and the guy that was working on another car comes up to me and says when i turned the ignition was it cranking fast, i explained it to him by sound and he goes it wasnt turning over fast enough and said always use a battery booster when doing compression test like they always do, Might try that. And another thing i thought was interesting another guy today I spoke to at Hills Motorsports in castle hill and he told me he had like 12 gtrs come through his workshop in the last 6 months with similar pressure like mine and some of them were pretty much new, and goes they were runnning excellent like all of them and told me "we'll he thinks" some GTRs came out with low compression pistons. is that true???? he sounded like he new what he was talking about because he specialises in these cars.hmmm

yeah, I don't think you have anything to worry about myself, I certainly wouldn't be doing anything about it if it was my car. It would have to get a lot worse than that before I'd be thinking engine rebuild time.

And you hit the nail when you talked about compression differences re pistons/head gaskets etc What you have is likely a very healthy normal motor.

If you're not looking for big power and/or big boost, ignore all of this rebuild talk - you dont need to rebuild your engine if you just use your car to get you from point A to point B, honestly it will be fine for many years to come.

.. if its low why is it low and how do i fix it....

probably why there is 'all this talk of rebuild' that has been happening - the question was asked

perhaps some of the people on here should write to nissan and get them to update their workshop manual, as you seem to know better

the compression is within spec, just, to completely ignore this, and not keep in mind that the engine MAY be ready for rebuilding in the near future, could be asking for trouble.

Anybody wonder why alot of tuners compression test engines before they try an lean on them on a dyno?

would those that beleive the engine is 'absolutely fine' care to enlighten us all on at what compression an engine is getting tired?

and would you pay just as much for an engine that is at the bottom of the published compression range as you would for one that is showing compression at the top end of the range? (not talking about built or decompressed engines here)

GTRAAH, as I said to you in pm, make sure you are using a good FRESH oil (15W50 would be my recommendation for RB engines) and redo the test, I think you will find the results will vary, as too many people use the wrong oils, and dont service their engines often enough.

I wouldn't worry too much if the readings are all equal.

Compression testing guages can be quite inconsistent from one brand to the next.

A mate of mine in his VLT tested his and made 160 across all cylinders.. erm 160psi with a 7.8:1 comp ratio. oookaaay.. :P

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Well, I can recommend the partial AV system translation CD I ordered from Car Audio Workshop in NZ. Whilst it didn't address the date issue, it has conveniently translated on-screen menu items into English, and now allows the GPS-received time to be offset in hours rather than minutes, so I can display Eastern Australian time accurately ( and bump it by another hour when daylight savings starts ).
    • Yuh, if it's 45°C outside, my car is driving in it.
    • I'd be curious to hear more. Otherwise, have you driven a modern x-trail? I wonder how it compares. Here in Australia they are/were popular for rentals and fleet vehicles. I have been in some and my impression was they are bad. But, this may have been very different in the 2000s at a good trim level. Twenty years is plenty of time to make the model worse. I do very much agree with the 2 silver cars in the garage approach. But, not driving because it's too hot would not leave a lot of time in the year for many Australians. I don't think you need to worry too much unless the car has actual issues with overheating. 
    • Back again. I returned to Japan in Jul/Aug to spend time with the car on my birthday and remind myself what all the sacrifice and compromise is for. It happened to line up with the monthly morning meet in Okutama, which I have been wanting to go to for a long time. It's a unique event at a unique spot with really rare, interesting, and quirky cars. It's where all the oldheads and OGs gather. The nighttime scene at DKF certainly has its place and should be experienced if you're into cars, but there's too much bad attention and negativity around it now. IMO the better time is Sunday morning at DKF or Okutama; it's more chill and relaxed. I'm glad I was finally able to go, but not sure it's worth the drive from all the way from Nagoya immediately the day before, unless I was already staying in Tokyo for the days right before the meet, because you have to wake up quite early to make it in time. Funnily enough though I didn't drive the car all that much this trip because it was just too damn hot. While there were zero issues and running temps were nominal and the A/C was strong, RBs already run crazy hot as it is. Sure, it took it all like a champ but something about driving these cars in the ridiculous heat/humidity bothers me and makes me feel like I'm asking too much of it. I'm just me being weird and treating the car like a living thing with feelings; I'm mechanically sympathetic to a fault. Instead I was mainly driving something else around - a KX4(silver) 2001 X-Trail GT, that I acquired in May. There's a few different flavors to choose from with Xs, but visually it's the Nissan version of the Honda CR-V. Mechanically it's a whole different story as this, being the top-trim GT, has an SR20VET mated to a four-speed auto and full-time AWD! It was a very affordable buy in exceptional condition inside and out, with very low mileage...only 48k kms. Most likely it was owned by an older person who kept it garaged and well-maintained, so I'm really happy with how it all worked out. It literally needs zero attention at the moment, albeit except for some minor visual touch-ups. I wanted something quirky, interesting, and practical and for sure it handily delivers on all three of those aspects. I was immediately able to utilize the cargo and passenger capacity to its full extent. It's a lot of fun to drive and is quite punchy through 1st and 2nd. It's very unassuming -in the twisty bits it's a lot more composed than one would think at a glance- and it'll be even better once I get better tires on it(yes, it's an SUV but still a little boat-y for my liking). So...now I have two golden-era Nissans in silver. One sports car and one that does everything else; the perfect two-car solution I think👍 The rest of the trip...I was able to turn my stressed brain off and enjoy it, although I didn't quite get to do as much as I thought. I did some interesting things, met some interesting people, and happened into some interesting situations however, that's all for another post though only if people really want to know. Project-wise, I went back to Mine's again to discuss more plans and am hoping to wrap that up real soon; keep watching this space if that interests you. Additionally, while working in the tormenting sweatbox that is the warehouse, I was able to organize most of the myriad of parts that my friend is storing for me along with the cars, and the 34 has a nice little spot carved out for it: And since it can get so stupid hot in there, that made it all the more easy -after I was standing there looking at the car and said 'f**k it'- to finally remove all the damn gauges that have mostly been an eyesore all this time. Huzzah. The heat basically makes the adhesive backing on the gauge mounts more pliable to work with, so it was far less stressful getting this done. I didn't fully clean it up or chase the wiring though; that will happen once I have the car in closer possession. Another major reason to remove all that stuff is to give people less reasons to get in my car and steal s**t while it's being exported/imported when/if the time comes, which leads us to my next point... ...and that is even though it's time in Japan is technically almost up since it's a November car and the X would be coming in March, I'm still not entirely sure where my life and career is headed; I don't really know what the future looks like and where I'm going to end up. I feel there's a great deal of uncertainty with me and as a result of that, it feels like I'm at a crossroads moreso now than any point in my life thus far and there are some choices I need to make. Yes, I've had some years to consider things and prepare myself, however too much has happened in that time to maintain confidence and everything feels so up in the air; tenuous one might say. Simply put, there's just too much nonsense going on right now from multiple vectors. Admittedly, I'm struggling to stay in the game and keep my eyes on the prize. So much so in fact, that very recently I came the closest I ever have before to calling it quits outright; selling everything and moving on and not looking back. The astute among you will pick up on key subtext within this paragraph. In the meantime I've still managed to slowly acquire some final bits for the car, but it feels nice knowing there's not much left to get and I'm almost across that finish line; I have almost everything I'll ever want for my interpretation and expression on what it is I think an R34 should be. 'til later.
    • Thanks for that, hadn’t used my brain enough to think about that. 
×
×
  • Create New...