Compression Test On '99 Rs4v

[pyro-ns]

Hi guys

My wife is about to take delivery of a 99 RS4V, subject to a compression test (spotted a dodgy thing or two).

Can anyone tell me what the compression should read? it's a series 2, so the rb25det neo engine.

So far all I can find is this post, recording 130psi (which i'm assuming is healthy, giving the consistency of the cylinders and nature of the post), captinsane's profile says he has an s1 stagea though, and i've heard of compression differences between the s1 and s2?

I was hoping to get this done this afternoon, so if anyone has any info, i'd be greatly appreciative

cheers guys

josh

[QWK32]

dry compression test i got around 155 across the cylinders. i done a mates neo engine and we got 150 across the cylinders, dry test.

[pyro-ns]

weehooooo! thank you very much!

[kidafa]

Your more chasing consistency over all 6 cylinders than massive numbers mate But sure if they all seem to be low figures id be carefull.

What are the dodgy things uve spotted?

[pyro-ns]

yeah, i realise consistency is the key, give or take 5%. just wanted to have a base figure in mind, so i know what kind of wear the engine has.

the main one, is that there's a mechanical boost gauge in the cabin and the vac line has been clipped off in the engine bay (as in, to the fpr, not the wastegate). not normally a problem, but the vac line's been bent on to itself and ziptied off in a rather average fashion. i want to make sure that there's no leaning out problems really.

aside from that, i could see a few bushes which seem a little more than 86,000k's worn. hadn't had an oil change in a while (or they're filling it with chocolate) and a very very small irregularity at idle (like a d/c vac line or something).

Edited July 21, 2009 by pyro-ns

[pyro-ns]

quick question guys, i'm doing a compression test at the moment. i'm doing the usual "remove all plugs, attach tester to plug 1, WOT + ignition, wait until needle stabilises".

is there anything i need to know about neo/rb engines that may be different from regular engines? (i came from sr's and ca's). eg, does a particular vac hose have to be connected?

the car's only done just under 84,000 and it's all over the place i feel like crying

it's so strange. the car blows no smoke at all, feels like a heavy turbo 6 when you get under it and there's very very little blowby in the ic pipes. there's a bit of dried residue, but i've rubbed my finger through all the pipes (as in, top ic pipe to the intake manifold and the crankcase venting pipes between the cam covers) and there's barely anything in there.

edit:

there's hope yet! according to google, the engine must be warm when you're compression testing. can anyone confirm this?

Edited July 22, 2009 by pyro-ns

[zei20l]

i think you need to remove the plug from the CAS so it doesnt attempt to fire or inject fuel, thus a 'dry' test..........

[pyro-ns]

cheers mate

i feel like a n00b :lol:

[zei20l]

im only guessing, on my SR i did the same thing. but being a better motor it was easier

[QWK32]

yeah just unplug the CAS so it doesn't fire or inject. WOT and crank about 2-3 seconds (4-5 cranks), also make sure you have a healthy battery so the crank is strong. dry test just means no oil is added to the cylinder to help the seal.

Josh if your getting readings that are all over the shop add 1-2 teaspoons of oil to the cylinder thought the sparkplug hole and redo the test. if there is an improvement then the rings are worn. if there is no change you need to do a leak down test and find where the compression leak is coming from.

[pyro-ns]

im only guessing, on my SR i did the same thing. but being a better motor it was easier

! seems like everyone's owned an sr at some stage, haha. haha, i'm with ya on that, TOP FACING INTAKE MANIFOLD FTL!

yeah just unplug the CAS so it doesn't fire or inject. WOT and crank about 2-3 seconds (4-5 cranks), also make sure you have a healthy battery so the crank is strong. dry test just means no oil is added to the cylinder to help the seal.

Josh if your getting readings that are all over the shop add 1-2 teaspoons of oil to the cylinder thought the sparkplug hole and redo the test. if there is an improvement then the rings are worn. if there is no change you need to do a leak down test and find where the compression leak is coming from.

cheers for that mate fingers crossed it'll do a bit better once it's warm. i figured seeing as it's just gonna idle there, i'll put the crank case hoses back on, non-clamped, same as with the ic piping. the oil in there's still old too, so trying not to drive it that much. service tomorrow, all things going well, so i'll leave it all apart tonight, so that i don't have to deal with that stupid top facing manifold and cowling any more than i have to, lol.

i get the feeling i've met you before too. are you on nissansilvia? i'm pyro on there, just in case my username didn't give it away lol.

Edited July 22, 2009 by pyro-ns

[RS4StagMan]

The R34 service manual specifies the following;

Compression pressure

175 psi standard

130 psi limit minimum

15 psi max limit of variation between cylinders

This relates to a dry compression test (i.e no oil added to spark plug holes).

[zei20l]

ahhh THATS why dry is. no problems thanks for clearing that up for me!

[pyro-ns]

The R34 service manual specifies the following;

Compression pressure

175 psi standard

130 psi limit minimum

15 psi max limit of variation between cylinders

This relates to a dry compression test (i.e no oil added to spark plug holes).

cheers for that mate

just did it then. mechanical gauge, so it'll be + or - a couple, depending on what angle you're reading.

1: 175

2: 170

3: 165 <-- cranking voltage was getting a bit low when we did this one.

4: 168

5: 168

6: 168

quite pleased!

thanks to everyone for their help

[zei20l]

i think thats pretty much on the money!

[BensDR30]

They're fair numbers, I wouldn't be too concerned about the compression. I would pay to investigate the idle irregularity a little more, however.

If you can get hold of some kind of Consult interface system, you can do an ECU controlled power-balance test.

LOL Iain - I'm glad I've never tried to do one of your 'wet' compression tests!

[pyro-ns]

They're fair numbers, I wouldn't be too concerned about the compression. I would pay to investigate the idle irregularity a little more, however.

If you can get hold of some kind of Consult interface system, you can do an ECU controlled power-balance test.

LOL Iain - I'm glad I've never tried to do one of your 'wet' compression tests!

yeah, the irregular idle is next. doing a service tomorrow. also trying to figure out where i can put some gauges. have some left over from the s13 that we traded in for the stag, so may as well make use of them.

i've noticed there's a few blue silicone pieces of vac lines around, so i'll be checking around them first for any vac leaks.

i need to get my hands on a workshop and owners manual as well. anyone know of any freebies going around?

also looking to convert all interior lights to led's for something a little brighter. currently neither of the interior lights in the roof work (no bulbs) and the shifter light is out as well. can anyone tell me if the series 2's have the lighting systems where the lights stay on for a few seconds after you've closed a door etc? i'll add a capacitor if they don't.

Edited July 22, 2009 by pyro-ns

[KiwiRS4T]

PM Chook for a low cost CD with a full Stagea Manual (in Japanese) and some R33 etc engine manuals in English which will answer most of your mech questions.

My interior light comes on when i unlock with my remote and goes off when i start the engine on my S1 so I am sure the S2 will have this feature as well.

[zei20l]

LOL Iain - I'm glad I've never tried to do one of your 'wet' compression tests!

but you want to dont you? hahah

i honestly thought a 'wet' test was letting the car inject fuel, but not fire (not that it can with the plugs out). i thought putting oil in was called something else. but you learn something every day. i also forget something every day.... now where do i work again?