Is My Compression To Low?

[ThomasH]

About a year ago I had my last compression test, with all cylinders between 9.4 and 9.6 bar. I was told these are decent numbers for a 14 year old RB25DET. However, on a differenent forum I stumbled upon a topic where compression was talked about, and several people agreed that the 9bar compression on the engine in question was to low.

So, what gives? Is the compression I have to low, or not?

[Moodles2]

With the RB26, the Nissan service manual recommends a rebuild at 125psi.. which is erm 8.62bar

[ThomasH]

With the RB26, the Nissan service manual recommends a rebuild at 125psi.. which is erm 8.62bar

That seems low. Though it should be higher.

[Spurdo]

it does sound just a touch low to me, but generally as long as the compression across cylinders is relatively even i wouldnt worry about it. when it starts burning oil or you get compression variances of more than 10 or 15 psi between cylinders then i would start thinking about a rebuild.

do you know if the heads ever been off before?

[ThomasH]

it does sound just a touch low to me, but generally as long as the compression across cylinders is relatively even i wouldnt worry about it. when it starts burning oil or you get compression variances of more than 10 or 15 psi between cylinders then i would start thinking about a rebuild.

do you know if the heads ever been off before?

AFAIK the head has never come off, but I have no history of the car in Japan.

To the person that PM'ed me, thanks for the help/info! I can't send PMs untill I have a postcount of ten, wanted to say thanks through here.

[ThomasH]

After a bit of chatting, and the friendly PM I recieved earlier, as long as the engine drives properly, both on boost and off boost and doesn't use oil or anything, I should be fine.

And other then a lowish compression, the engine is spot on and doesn't miss a beat. I'll try and get a leakdown test done soon, see if that says anything.

[t_revz]

did a comp test on my rb25det 5 years ago and got 120psi each although never missed a beat apart from burning a litle bit of oil. thought something was up as manual says rebuild at 135ish psi yet i was making plenty of power. just opened it up and found melted piston and all rings rooted. i guess it shows how well these engines perform even when not in tip top condition

[Miguele]

Yes.It is very low...

[Galois]

compression changed from 8.5-1 to 9.0-1 when the engine went to neo, is it the same on the rb26 or is that just the rb25's?

[Jezza-gtR]

It is a little low but as stated before if it is even on all cylinders then don't worry. 150 psi is average good.

[ThomasH]

Well, I decided that it's probably the best thing to start saving up some parts for a little rebuild. Nothing fancy, just OEM or slightly updated parts. I don't want a full forged rebuild, since that's gonna cost a lot, and I'll never reap the benefits of a forged engine, since I'll never go above a stage1 tune. I want a car to get me to work, which I can take to a driftday every now and then.