Jump to content
SAU Community

Recommended Posts

Lookin to buy a car and had a compression test done by performance place and just wondering if anyone can give me some advice. ill update the exact results for each cylinder later but on average no higher than 170 and no lower than 150, i think was somethin like 170, 170, 150, 160, 155, 150

like i said ill update bit later, but thats basically what i remember? was told its ok, then told its not any help please????

Thankyou!!

Link to comment
https://www.sau.com.au/forums/topic/247656-compression-results-on-34gtt/
Share on other sites

You get different readings depending on the battery and a few other components. I believe 150 is standard but the higher the better they say.

Of course they must be consistent with each other.

If there not identical to each other move on to another car until you find one that is.

You want it to be spot on

the other thing is you really need a leak down test also.

When i had my 100km service the compression was 170 170 170 170 60 65, since the car is pulling max power for the mods i was like wtf

Turns out i just had a heap of carbon build up in the intake.

Test after was 170 170 170 170 170 170

Ok results were As follows:

CYLINDER 1- 170PSI

CYLINDER 2- 170PSI

CYLINDER 3- 160PSI

CYLINDER 4- 150PSI

CYLINDER 5- 155PSI

CYLINDER 6- 160PSI

Guy from the workshop said car runs smooth as a babys behind. and really seems like the guy doesnt thrash it, middle aged and very particular owner and mechanic said car is very well looked after. then again u never kno what happens in japan. Im gona ask for a leak down test I think to be sure. what u think?

Edited by 1R34SON

When I bought my car, I had a clause on there, which was I can return the car if my mechanics testing showed the engine was not in good condition.

Did a dry compression test: 1 - 176, 2 - 175, 3 - 177, 4 - 176 , 5 - 177, 6 - 176

Did a wet compression test: 1 - 177, 2 - 177, 3 - 176, 4 - 177, 5 - 178, 6 - 178

The minimal difference in figures means that it was great compression to start with, and after using some oil to further seal the rings, the figures where almost the same (there is a variance in or 3 - 5 psi in the gauge I used). Considering the figures where almost identical, it means there is no pressure loss on the rings, meaning any pressure loss is in the valves.

a Leak-down test revealed the pistons hold very good pressure, meaning the valves are not loosing pressure, and the engine is in good condition.

Did a radiator pressure test as well, revealed no issues, did an intake pressure test, no boost leaks or other leaks,so I rang the previous owner and told him to go nuts with the money, I wasn't disappointed with the tests at all.

I later found out from a relative of the previous owner that the engine had blown, and was completely rebuilt from the ground up, forged pistons, rods, balanced crank, all the oil mods to the head, sump baffles, N1 turbochargers, etc. The works has been put into that engine to make it bullet-proof (as bullet proof as an RB26 will get), but then he had to sell for family reasons.

If you get a good RB engine, and you let them warm up before revving them and thrashing them, keep good oil to them, and dont rev them over 7,000rpm (unopened), the engine should be good for a lengthy life.

It's the other bits you need to worry about, gearbox, diff, suspension, rust through the body, but someone who knows cars will be able to pick if they have been in an accident, or if they are riddled with car-cancer.

My only advise: Dont fall in love with a car while looking, treat them all as damaged stock until you find the perfect one, and once you have purchased it, you can fall in love. (I fell in love with a 180sx yrs ago, wanted it no matter what so I wasn't maticulous in checking it out. Later found a 1 inch rust spot, took the screwdriver to it to brake all the rust out before welding a plate to the car, and the hole was 1 inch, but the rust through the panel was 1 foot 2 inches, it was HUGE!!!).

B.

Again - as stated earlier... its the % difference not the actual numbers more than anything.

Obviously if it goes

160 150 155 160 150 80

Then you have a problem, but if they are all near enough to the same number, its fine and a good result.

If you want a much better TEST - Leak Down test is the one your after

Again - as stated earlier... its the % difference not the actual numbers more than anything.

Obviously if it goes

160 150 155 160 150 80

Then you have a problem, but if they are all near enough to the same number, its fine and a good result.

If you want a much better TEST - Leak Down test is the one your after

spoke to a guy from a turbo engine tuning workshop and told me this same thing ^

he said that numbers will usually vary. and as long one isnt out by heaps or under 150 its fine. cheers all!

When I popped my stocker, it went:

Cyl 1/ 0

Cyl 2/ 75

Cyl 3/ 150

Cyl 4/ 150

Cyl 5/ 150

Cyl 6/ 150

See if you can guess which piston had a broken ringland and which had lost ring tension.

I'm guessing Cyl 2 had a broken ring land and your ring lost tension when you realised the motor needed a rebuild :(

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

    • Hey guys, I’m a veteran detailer with years of hands-on experience. I’ll be sharing quick, effective detailing tips to help you keep your Skyline (or any ride) looking its best. Got a question? Fire away!
    • I guess when I say it's a POS I mean.. the solution and the stuff has the capacity for maybe... 1 spot. You know, as a spot cleaner. What I really *want* is the ability to do an entire car, all upholstery, all carpet, mats, all seats, door card inserts, A pillars, roof liners, etc. In one go. I get lured by all the jank that comes out and think "I'd like to be able to clean to that degree"
    • I've got one (not the car one, the domestic spot cleaner one, which is basically the same jobbie) and have driven it hard for hours and hours at a time. Grimy sofas, 6' floor rugs, etc. I'd blame your specific example rather than the whole category. I haven't used mine in the car, because.... you know, it's my car. So there is no-one else's ball sweat in the driver's seat, there's no kid food/drink spills or hand prints inside because they've never had an opportunity to put them there. You know, basic, standard Skyline rules.
    • I normally run with I think a 10mm, and definitely use the second handle you can add to a drill. They hurt when they bins up!   For the crush tube, once all subframe is clear, I'd try some stilsons and see if I can get it to start to twist.
    • Probably because they couldn't, because the use of the variable resistor to create a "signal" in the ECU is managed by the ECU's circuitry. The only way that VDO could do it would be if they made a "smart" sensor that directly created the 0-5V signal itself. And that takes us back to the beginning. Well, in that case, you could do the crude digital (ie, binary, on or off) input that I mentioned before, to at least put a marker on the trace. If you pressed the button only at a series of known integer temperatures, say every 2°C from the start of your range of interest up to whatever you can manage, and you know what temperature the first press was at, then you'd have the voltage marked for all of those temperatures. And you can have more than one shot at it too. You can set the car up to get the oil hot (bypass oil coolers, mask off the air flow to oil coolers, and/or the radiator, to get the whole engine a bit hotter, then give it a bit of curry to get some measurements up near the top of the range.   On the subject of the formula for the data you provided, I did something different to Matt's approach, and got a slightly different linear formula, being Temp = -22.45*V + 118.32. Just a curve fit from Excel using all the points, instead of just throwing it through 2 points. A little more accurate, but not drastically different. Rsquared is only 0.9955 though, which is good but not great. If you could use higher order polynomials in the thingo, then a quadratic fit gives an excellent Rsquared of 0.9994. Temp = 2.1059*V^2 - 34.13*V + 133.27. The funny thing is, though, that I'd probably trust the linear fit more for extrapolation beyond the provided data. The quadratic might get a bit squirrely. Hang on, I'll use the formulae to extend the plots.... It's really big so you can see all the lines. I might have to say that I think I really still prefer the quadratic fit. It looks like the linear fit overstates the temperature in the middle of the input range, and would pretty solidly understate what the likely shape of the real curve would say at both ends.
×
×
  • Create New...