Jump to content
SAU Community

Recommended Posts

Last build- RB30/25, standard pistons, ACL rings, 7.8:1, RB20/25 oil restrictors (x2), RB25 oil pump, standard oil returns. 320rwkw on 15psi. Very little to no oil in catch cans ever unless it got a huge rev limiter expereince then maybe a little.

This build- Same except CP flat tops 8.2:1, CP rings, same restrictors, same pump, drilled out oil returns from 8mm to 10mm, ported rear returns, port matched block/head/gasket for oil returns, 3/4" drain pipe from rear of head to std turbo return point (turbo return is in sump wing). 350rwkw on 18psi.

This time it spits oil out at an amazing rate. After a 2nd-4th gear run it will spit out about a litre and make one nasty mess. If I didn't have an 8 litre sump I could be in strife.

Comp test is 168-160-162-162-160-165. I can almost guarantee the bores are NOT glazed up. Motor is 850km old. It did not (and still does not) blow any oil out for the first 800km when it was on 9psi.

I have read the thread about what oil restrictors to run and I am about to block one off totally but before I pull it apart- has anyone else had this amount of oil come out?

(It is obviously power related so it would have to be over 300rwkw I would say.)

Thank you in advance!

Link to comment
https://www.sau.com.au/forums/topic/167444-my-motor-hates-oil/
Share on other sites

my brothers motor with forged cp pistons flat tops does that too, i think its a forgie thing? oh and he has a fully race prepped sr20det

and he only has 185rwkw (standard turbo)

Edited by LTHLRB

Id doubt the delta between his setup and others with 30/25 combos that don't spit oil... is the forgies :blink:

A liter of oil from the cam breathers... past the stock grill / scrubber setup is a insane amount

lukevl could be close, as i would think some serious blow by could push the oil into the can

Interesting issue there man... i dont even have 2c to give :D

Have you had it on the dyno to see volume of air coming out of the catch can? I have never used CP pistons, but i have read that there rings are pretty crap (here say from other people).

maby a leak down test is needed to check the rings?

Edited by GTR1993

well to prove you rong about the forgies... The guy who built my brothers motor built a 9sec vl GMVL6.. one night of racing with 370+kw at the wheels (3 half tracks and 1 full) filled the catch can to the brim twice!

A mate of mine had a 25/30 and had the exact same prob. I would say they have used the wrong head gasket. The correct head gasket has a few more oil drain holes in it. Thus when higher rpms are used the oil can't return to the sump quick enough, causing it to blow into the breather hose and into the catch can.

You say the bores aren't glazed- but was the engine honed on the last rebuild?

To go through oil like that, you must have some fairly serious blow-by/oil control ring issues

Have you eliminated block warp or poor quality ring issues?

hmm

duggans machining and balancing did my brothers engine.. but still seems to have blow by..

hell even a few of CREATD high powered cars have that problem, especially the sr's

As a guide my SR20 and RB26 both have forged pistons and both have no oil in the catch cans. The sr runs no oil catch can at all and not one drop out the breathers.

Edited by GTR1993

You cant use the wrong head gasket. There are no extra oil returns that are blocked off to the extent your getting. Also as he stated it has a return externally from the head to the sump so you will find the majority returns via that!

Its going to be a ring issue. I dunno who built it but was it done properly and EVERY thing checked. Oftern is the case a builder wont measure ring end gaps and side clearance mearly assuming its right.

LTHLRB it sounds like this Created workshop dont know much about building a tight engine if they all use oil!! Ive built many many top end SR20's over the years and only had 1 or 2 that have had any blow by and both were rush jobs that were needed right then and there. If its all built right forgies or no forgies there should be stuff all oil in the catch can.

I can do a years worth if racing in the GTR and not even look in the can.

my brothers motor with forged cp pistons flat tops does that too, i think its a forgie thing? oh and he has a fully race prepped sr20det

and he only has 185rwkw (standard turbo)

i would also like to add to this thread

im not a skyline owner but im a 180sx sr20 owner

my sr20 is full built with forged internals and im making 305rwkw on pump gas out of a 2L engine

my engine also spits out oil the reason for this is. cylinder to bore clearance

im also using CP forged pistons

when installed cp forged pistons it will come with a specs sheet for ur cylinder to bore clearance as u all ready know :P

the clearance is abit more then standard this will cause the oil to spit out and the reason they do this is for when ur aiming at high HP

they give the piston enuff clearance so that the piston can heat up and not lock up in the cylinder

giving the piston more clearance between the bore will also give it less friction when the piston heats up and gets bigger

Ok the build should not be the problem. I built it, but i also built it before when it had no problems. I did all the end gaps and clearancing etc etc. I used the same engine machinist and we always use him- he does great work. I installed the rings with CRC only to prevent glazing and ran it in properly.

Like I said on low boost it does not have this problem- you would think if it had that bad an issue with blow-by it would still do it on low boost but it doesn't do it AT ALL after 800km of hard driving and longer in the high revs.

I am going to block one oil feed. Sydenykid said to only run one so I'll give it a go and it might help since it will be getting just over half the oil it gets now.

Edit- I have also port matched the block, head and gasket. And it doesn't do it on the dyno at all. So its only when it gets G-force that it spits it out.

Edited by lukevl

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

    • Surely somebody has one in VIC. Have you asked at any shops?  Is this the yearly inspection or did you get a canary?
    • This is where I share pain with you, @Duncan. The move to change so many cooling system pieces to plastic is a killer! Plastic end tanks and a few plastic hose flanges on my car's fail after so little time.  Curious about the need for a bigger rad, is that just for long sessions in the summer or because the car generally needs more cooling?
    • So, that is it! It is a pretty expensive process with the ATF costing 50-100 per 5 litres, and a mechanic will probably charge plenty because they don't want to do it. Still, considering how dirty my fluid was at 120,000klm I think it would be worth doing more like every 80,000 to keep the trans happy, they are very expensive to replace. The job is not that hard if you have the specialist tools so you can save a bit of money and do it yourself!
    • OK, onto filling. So I don't really have any pics, but will describe the process as best I can. The USDM workshop manual also covers it from TM-285 onwards. First, make sure the drain plug (17mm) is snug. Not too tight yet because it is coming off again. Note it does have a copper washer that you could replace or anneal (heat up with a blow torch) to seal nicely. Remove the fill plug, which has an inhex (I think it was 6mm but didn't check). Then, screw in the fill fitting, making sure it has a suitable o-ring (mine came without but I think it is meant to be supplied). It is important that you only screw it in hand tight. I didn't get a good pic of it, but the fill plug leads to a tube about 70mm long inside the transmission. This sets the factory level for fluid in the trans (above the join line for the pan!) and will take about 3l to fill. You then need to connect your fluid pump to the fitting via a hose, and pump in whatever amount of fluid you removed (maybe 3 litres, in my case 7 litres). If you put in more than 3l, it will spill out when you remove the fitting, so do quickly and with a drain pan underneath. Once you have pumped in the required amount of clean ATF, you start the engine and run it for 3 minutes to let the fluid circulate. Don't run it longer and if possible check the fluid temp is under 40oC (Ecutek shows Auto Trans Fluid temp now, or you could use an infrared temp gun on the bottom of the pan). The manual stresses the bit about fluid temperature because it expands when hot an might result in an underfil. So from here, the factory manual says to do the "spill and fill" again, and I did. That is, put an oil pan under the drain plug and undo it with a 17mm spanner, then watch your expensive fluid fall back out again, you should get about 3 litres.  Then, put the drain plug back in, pump 3 litres back in through the fill plug with the fitting and pump, disconnect the fill fitting and replace the fill plug, start the car and run for another 3 minutes (making sure the temp is still under 40oC). The manual then asks for a 3rd "spill and fill" just like above. I also did that and so had put 13l in by now.  This time they want you to keep the engine running and run the transmission through R and D (I hope the wheels are still off the ground!) for a while, and allow the trans temp to get to 40oC, then engine off. Finally, back under the car and undo the fill plug to let the overfill drain out; it will stop running when fluid is at the top of the levelling tube. According to the factory, that is job done! Post that, I reconnected the fill fitting and pumped in an extra 0.5l. AMS says 1.5l overfill is safe, but I started with less to see how it goes, I will add another 1.0 litres later if I'm still not happy with the hot shifts.
    • OK, so regardless of whether you did Step 1 - Spill Step 2 - Trans pan removal Step 3 - TCM removal we are on to the clean and refill. First, have a good look at the oil pan. While you might see dirty oil and some carbony build up (I did), what you don't want to see is any metal particles on the magnets, or sparkles in the oil (thankfully not). Give it all a good clean, particularly the magnets, and put the new gasket on if you have one (or, just cross your fingers) Replacement of the Valve body (if you removed it) is the "reverse of assembly". Thread the electrical socket back up through the trans case, hold the valve body up and put in the bolts you removed, with the correct lengths in the correct locations Torque for the bolts in 8Nm only so I hope you have that torque wrench handy (it feels really loose). Plug the output speed sensor back in and clip the wiring into the 2 clips, replace the spring clip on the TCM socket and plug it back into the car loom. For the pan, the workshop manual states the following order: Again, the torque is 8Nm only.
×
×
  • Create New...