Jump to content
SAU Community

Bad piston rings or damaged cylinder walls?

eric240sx
 Share

Recommended Posts

eric240sx Contributor

eric240sx

Posted
Posted
Bad piston rings or damaged cylinder walls?

Recently, I opened a discussion on my excessive oil burning that my rb25det does and thanks to the help of many enthusiasts we concluded that it is bad piston rings or a damaged cylinder wall... or can it be both?

Engine had a full upgraded rebuilt 6 months ago with it being bored over .020 over. It has been driven 1000 miles or 1609 kilometers since 

I have compression tested all my cylinders and it showed a psi of 50-70psi. When I did a wet test it shot up to 120-135psi

My rb25det has a 1.5 cosworth head gasket so compression will be lower than normal 

My hopeful prediction is that the piston rings have seized, been installed improperly, or the rings are worn out. The reason why I don't believe its damaged cylinder walls is because every cylinder shows the same sign of compression loss and piston rings go out together. Cylinder walls are unlikely to all be damaged at the same time

 

What do you guys think?

Birds Grand Master

Birds

Posted
Posted

Why wouldn't they all suffer the same fate/damage? You're repeating the same process for preparation, installation and running in of each cylinder which happens all at the same time. If it was just one cylinder then you could put it down to a faulty part...

eric240sx Contributor

eric240sx

Posted
  • Author
Posted
3 hours ago, djr81 said:

Piston rings don't wear out in 1000 miles.  What does happen is people don't bed them in properly and they never work from the start.  How did you run the engine in after start up?

when i finished with the rebuilt, i would keep the car in high rpm when race on the street and events. But whenever I drove normally, i would try to have it at the lowest rpm possible around 2k-3k rpm 

eric240sx Contributor

eric240sx

Posted
  • Author
Posted
3 hours ago, Birds said:

Why wouldn't they all suffer the same fate/damage? You're repeating the same process for preparation, installation and running in of each cylinder which happens all at the same time. If it was just one cylinder then you could put it down to a faulty part...

The reason why i find it unlikely for all 6 cylinders to be wall damaged is because there needs to be something thats consistent throughout the cylinders thats causing the damage. If something exterior got in and scratched a cylinder wall it would only be on that one and not all of them. While rings go out together since all they do is seal and if they were installed wrong then they are all going out  

Birds Grand Master

Birds

Posted
Posted

Sorry, I think I misread your original post. I meant that they could all have buggered piston rings and not just one.

Though I guess there is a possibility the walls were not honed correctly? Tolerances are all matched up fine, I assume?

KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted

Doesn't really matter the head will have to come off and the pistons out. You can measure the bores and see if they are glazed. If they are within spec you may be able to rough them up with a suitable hone. Get a professional to look at your rings or compare them with a new set.

When the motor is rebuilt do not start it until you have an aftermarket ecu set for your injectors and get it tuned on the dyno with a load of mineral oil or special running in oil. By the time it has had a few full power pulls on the dyno it should be half way run in .(if you can't afford to buy and tune an aftermarket ecu - about $3000 - then return the engine to stock until you can) .

The head gasket will not have a significant effect on your compression ratio although I would be inclined to get a 1.2 Tomei gasket which you can reuse if (hopefully not) you have to pull it down again.

PS and don't keep starting new threads for the same issue!!

eric240sx Contributor

eric240sx

Posted
  • Author
Posted
15 hours ago, KiwiRS4T said:

Doesn't really matter the head will have to come off and the pistons out. You can measure the bores and see if they are glazed. If they are within spec you may be able to rough them up with a suitable hone. Get a professional to look at your rings or compare them with a new set.

When the motor is rebuilt do not start it until you have an aftermarket ecu set for your injectors and get it tuned on the dyno with a load of mineral oil or special running in oil. By the time it has had a few full power pulls on the dyno it should be half way run in .(if you can't afford to buy and tune an aftermarket ecu - about $3000 - then return the engine to stock until you can) .

The head gasket will not have a significant effect on your compression ratio although I would be inclined to get a 1.2 Tomei gasket which you can reuse if (hopefully not) you have to pull it down again.

PS and don't keep starting new threads for the same issue!!

This is exactly what I am going to do. I am going to pay an RB specialist to disassemble my engine and inspect my internals. I am going to be running an e32 ECU with nistune to tune the engine. "I have money, it's trust and character that I never looking for." -Han ?

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
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • Komdotkom
      R32 Gtst - Track Car

      By Komdotkom · Posted

      Good luck on the weekend mate
    • Duncan
      From Japan and back to Europe, my sh*tbox R34 GTT

      By Duncan · Posted

      Must have been an absolute nightmare to drive when the power steer was out, the rack ratio/wheel size/caster is all set up for power assistance
    • Duncan
      New

      By Duncan · Posted

      Welcome to SAU, what are you looking at buying?
    • GabsReDeal
      R32 GTS (RB20DE) Injectors Replacement

      By GabsReDeal · Posted

      I checked the injectors again (1 and 2, since they’re easiest to access) to make sure they weren’t clogged. Even though the entire fuel system had been cleaned, I wanted to be certain. Everything looked clean, so I reinstalled and connected everything. When I started the car to confirm everything was okay, it immediately revved up high, so I shut it off straight away. I checked to see if I’d missed a vacuum hose or something, but everything was connected. On the second attempt, the car ran without the high idle, but I noticed a distinct “compressed air” sound coming from the engine bay. Tracing the sound, I pushed injector #6 forward slightly and the noise stopped — it turned out it wasn’t seated properly, despite the fuel rail being bolted down. While holding it in place, the car idled steadily without stalling and ran for over 5 minutes. At this point, I pulled all six injectors out just in case I hadn’t seated them correctly or dirt had gotten onto the O-rings. Unfortunately, I discovered that I had damaged 3 out of 6 injectors (the OEM 270cc ones) during installation. So yes, this was my fault. Since only the pintle caps were damaged, I’ve ordered a Fuel Injector Service Kit from NZEFI to refurbish them. In the meantime, I reinstalled my new injectors – the car now idles fine for over 15 minutes without stalling. I have not attempted to drive it so far. It’s not perfect yet, as it hesitates when the throttle is pressed, but it’s a big improvement. Unplugging the IACV with the new injectors idles at around 800rpm, even with the IACV screw tightened fully. But this is probably due to tune.
    • hoodedreeper
      Chris' Toyota Mark ii JZX110

      By hoodedreeper · Posted

      I wanted to try and preserve the front bumper as long as possible, they're not cheap and are made to order in Japan. Taking inspiration from my previous K11 Micra build where I made an undertray for the Impul bumper, I did the same for this BN Sports bumper but a little slimmed down.  This time round I only made a 'skid plate' (if that's the correct wording/term) for just the bumper surface area, the Micra version covered the gap like an undertray. Starting off with a sheet of mild steel approx. 0.9mm thick 4ft x 2ft in size. I traced around the bumper, cut it out and cleaned the edges. Luckily I was able to get two halves from one piece of metal In the video I installed it as is, but I've since then I've removed it to spray and add a rubber edging trim. The rubber trim is suitable for 1-2mm and it's a really nice tight fit. The bolts had to be loosened due to the plates being too tight against the bumper, the trim wouldn't push on I used some stainless M6 flat headed bolts for a flusher finish (rather than hex heads poking down), I believe this style fastener is used for furniture too incase you struggle to source some. The corner's are a little wider, but this may be an advantage incase I get close to bumping it  The front grill got some attention, finally getting round to repairing it. Upon removal one fixing pulled itself out of the plastic frame, one side is M8 that fixes inside of the frame, where as the other side is M5. Not knowing I could get replacements, I cut down an M8 bolt, threaded it inside the frame along with a decent amount of JB Weld.  The mesh was replaced to match the bumper. One hole on the bonnet/hood had to be drilled out to 8mm to accommodate the new stud, once the glue had set it could be refitted. I think the reason the grill was double meshed was to hide the horn/bonnet latch (which makes sense) but I much prefer it matching the bumper Bumper refitted and it's looking much better IMO The Youtube video can be seen here: https://www.youtube.com/watch?v=bVZP35io9MA
×
×
  • Create New...