u12 compression (psi)??

[Pulsar X]

Does anyone know the compression (psi) for the sr20det u12 bluebird engine..?? :confused:

[Lonx]

I don't know the specific compression for that SR20, but the following article quotes 155kw, runs a T25g turbo from factory & did 13.9 on first run, 13.2 on the second with 13psi. Might be an interesting read anyway :)

http://www.autospeed.com/A_1090/page1.html

[AWK666]

Dont Quote Me but im pretty sure its 6psi.

[Lonx]

Ahh you meant boost / air compression... I guessed you meant cylinder compression, obviously also measured in psi.

[Stusse]

Me thinks hes referring to cylinder compression Right? You are looking at the half cut for sale Right? R these guys giving a warranty?

Jap Wreck is selling one for $2400 in cannington if thats the same engine..Not Sure But they are offering a 6 month warranty on the engine..

Cheers, Steve :bounce:

[Pulsar X]

Yeah sorry, I was refering to the cylinder pressure. Yeah looking at buying a front cut. Just want to make sure.....things are in good nick. JapWreck offering 6 month warranty hey....hmm... not sure of the warranty on the one I'm looking at.:(

Well if anyone knows please let me know. Thanks:thumbsup:


Ohh and anyone knows about getting parts for the engine, like are they available here...... or are they hard to get.

[Stusse]

Hey Pulsar X

I dont know how the compression test works but I do know there is a way of hiding the true compression of the engine some how. Got to be real careful. Well at least thats what Ive been told. I believe Tephra should be able to elaborate on this stuff from Perth. PM him..


Cheers, Steve :bounce:

[Lonx]

Well I can't quote figures for the U12 SR20DET, however the original S14 SR20DET ran a compression ratio of 8.5:1, so if the engine is also running 8.5:1 then you should be able to rely on the following figures. When doing a compression test, its possible to put a little oil into the cylinder which will help seal any worn rings, resulting in a higher (but false!) result. Note these figures are from Nissan.

Minimum - 128psi
Standard - 156psi

[QIKRNU]

s14 engines are different, note the black top on a late model s13 or a s14/15. The blacktop means it has VVT

[Lonx]

These figures are from the non VVT engine, I was aware of the blacktops but doubt the U12 came with it considering when the U12 was released. Not sure exactly what it did come with - however if you can confirm the compression ratio, then it doesn't matter if its VVT or not, the compression values should still be the same I believe.

[QIKRNU]

Youre right in saying the u13s dont have VVT, however i was just saying that if they changed the VVT + t28 on a s14 then they might well have changed other parts

[Tephra]

hi guys,

yes the eternal question for me :)

well ive tested my engine, does about 145-150 in a compression test accross all cylinders. the SR20DE is meant to be 140->170, but DET has lower compression 8.5:1 vs 9.5:1 i think...

if you want to know how to do a compression test at the yard before you buy give me a message it will cost about $30 and thats to but a compression tester... which you can resuse... ill tell u how todo it...

if anyone knows what values the DET is meant to have let us know.

cheers
d

[Pulsar X]

Hey thanks for everything guys, me bought it on Sat. It looks to be in good condition and I'm very happy.

and as a friend would say....... Its all fun and games. :D

[Pulsar X]

Hey Tephra,

I got values of around the 155psi mark. What engine do you have..??..

[Tephra]

lowest 145 highest 150...

it seems good...

also when you have it started and the rockercover cap off do you get a lot of oil spitting out of it? or like a lot of blowby comming out of it.

d.

[Pulsar X]

Well I did have it started over there, though I didn't check for that. I'll have to set up the fuel/pump, to it here at home and check it out. I hope all's well with that.

Why Tephra, what does blowby mean.??:confused:

[Tephra]

well blowby means that everytime the piston fires some of the gases and shit leak down the side of the piston past the rings... ie the rings are worn...

usually you can detect this by taking the oil cap off while the engine is running, there should be a slight suction rather than pressure... however i dont know if this is so on the DET as my rings appear fine (compression test) but im getting a lot of blowby... or maybe its something else..

anyone know or can test this out on their engine?

d.

[Lonx]

Tephra, I was quoting figures from the SR20DET... Why do you think you have blowby if the engine is compressing fine?

[Tephra]

Lonx,

Well there seems to be quite a lot of pressure OUT of the oil cap once you take it off, my old car had a slight suction... can anyone else do this test?

Cheers
d.

[Pulsar X]

Hey Tephra, my brothers sr20de Silvia spits a little oil out when cap is off. Not sure but I think this is normal. Mine does it as well, the de anyway.

The engine should be sealed for optimum operation, if the cap is off, well there are pressure differences and this could be the thing your talking about. It doesnt mean it does it when the cap is on.

[Lonx]

Hmmm, I'll ask my old man for his opinion. Is it possible it could be a leaky valve guide or something on the intake side? Though I guess the compression test would also pick this up.... something to ponder I guess :)

[evldan]

I tested my U12 sr20det and got around 150 on two pistons and about 50-75 on the other two (yeah, rooted ring landings!)
So the 150 mark is what you should be getting on it.

[Lonx]

Therefore it would be safe to say your compression ratio is the same as the S14 @ 8.5:1. Compression doesn't vary with engine technology, only piston -> wall clearances (which is affected by the condition of the rings) & compression ratio will do it. VVT is a technology bolted onto the head which doesn't affect the cylinder or compression.