Jump to content
SAU Community

Melted Pistons Only On Intake Side?

Shockster0429

By Shockster0429,
in Engines & Forced Induction

 Share

Recommended Posts

Shockster0429 Enthusiast

Shockster0429

Posted
Posted

Here are some pics of the damage this is the #6 cylinder piston and it is the worst. All 6 of them were damaged. Also a few close ups of 3 spark plugs, as far as I can tell they show no signs of pre-det from what I can tell. Just carbon/oil marks from being rich and well burning oil due to serious blow by.

DSCN4509.jpg

DSCN4512.jpg

DSCN4515.jpg

DSCN4516.jpg

DSCN4517.jpg

As you can see in the pic the damage is ONLY on 50% of the piston all on the intake side. The exhaust side of the piston is as smooth as they day I bought them...

Timing was 16 degrees WOT @ 16-17 psi through the 67mm. 2.7 liter 8.5 to 1 compression. Super super conservative. 93 octane A/f's were 11.0's WOT till 7250rpm were I was letting out. Intake temps around 30-32 C, coolant 88-92 C. I didn't appear to be having EGT issues during this time. It was before when my exhaust adjustable cam gear was super retarded w/o me knowing (finally found the issue) and I was missing 50% of my power when my manifold/turbine housing would be glowing as red as a stop sign after a pull or two.

Question comes down to what does a knowledgeable person on reading pistons feel would make it only melt on the intake side?

Link to comment
https://www.sau.com.au/forums/topic/232311-melted-pistons-only-on-intake-side/
Share on other sites
Lithium Grand Master

Lithium

Posted
Posted (edited)

Thats crazy, I would be clutching at straws really to give anything haha. Is there ANYTHING else about the setup that you think you could share? What kind of air filter were you running? Its a bit weird there isn't obvious pitting/strange shape in the piston - ones I have seen from lean run or det are usually a lot less "smooth" than that, its almost like its been machined and I'm sure you'd have mentioned if the spark plugs had melted or anything like that. Its rather odd.

The more I think about it, the more I think its gotta have been detonation.... did you have knock mic on it etc when tuning?

Edited by Lithium
unique1 Mentor

unique1

Posted
Posted (edited)

i have had something similiar happen to my rb27 in the past making big power (600hp+). Mine didnt melt any plugs but did some serious damage to 3 forged JUN pistons and the other 3 were starting to go as well, also on the intake sides only, cylinder 1, 3 and 6 from memory. My head looked the worst, have u got any pics of the chambers of those cylinders to see what its like?

how much power u pushing at the time?

send me a pm with pics if u like and i can let u know what was causing mine.

Edited by unique1
RPMGTR Community Regular

RPMGTR

Posted
Posted

"Super super conservative"

Um no.....you have detonated it to death.........

See the pic with the side of the piston eaten away....det does that, and yes generally on the intake side.

16 degs (altho it may sound low) can be way too much sometimes, it all depends on the individual engine/setup.

Some combos only cop single digits, while others love 25+...

zeko33 Collaborator

zeko33

Posted
Posted

thats wat happened to me, except all 6 pistons were just fktttt....... It was the bad fuel and topped it when i took it to echuca ....... My friend has access to echuca Airport after hours and its insane man....... but ye now a rebuilt engine with forgies and i will never treat her with standard unleaded again.... Giving my 33 normal unleaded is like slapping god in the face.... YOU JUST DONT DO IT hahahahahaha

Martin HKS Enthusiast

Martin HKS

Posted
Posted

Looks like a big case of too lean.

Why it does it on the intake side is due to cylinder inefficiencies on intake. Swirl in the chamber or intake valve shroud or short side radius air flow etc etc. will cause one part of the piston/chamber to have a problem with detonation first.

I suggest you find a new tuner if they reckon all is well.

Cheers

Marty

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

    • GTSBoy
      So i brought a boat...

      By GTSBoy · Posted

      And also there were for sale scams and the like. For sale posts need piccies, and not having piccies makes it harder to do a driveby scam.
    • GTSBoy
      R33 RB25DET oem turbo replacement options

      By GTSBoy · Posted

      And I forgot to add my *** footnote to the above post, which was that the pipework mods would be even more significant than what had to be done for the highflow. So just add that onto the list. Pipework mods are no killer, just made the tasklist longer at a time when extra tasks were not welcome.
    • Kinkstaah
      So i brought a boat...

      By Kinkstaah · Posted

      I mean he could post them to imgur or the like and create a link. But yeah, spam bots absolutely will post pictures in their first posts.
    • silviaz
      R33 RB25DET oem turbo replacement options

      By silviaz · Posted

      Ah ok, reason I asked was for the sake of not having to upgrade everything if the turbo couldn't be capped.
    • GTSBoy
      AC Compressor

      By GTSBoy · Posted

      pffft! My alignments are starting to take 3-4 weeks each. Bugger overnight - that would be a dream! Overnight is when I leave it on stands with the rear suspension in pieces, hoping I can remember where I was at when I come back to it. I have to set the car up on a level surface so I can get decent camber measurements, then try to set the RUCAs to the right length to get that right. Then I have to put the car somewhere else where I have enough room to set up the bumpsteer gauge (laser, paper, mirror), so I can dial out that. Then I need to go measure camber again because changing the tension arm length affects that also. Then I need to measure toe, and I can't do that to my own satisfaction at home, so I have to put it on an actual aligner. Then I have to go back and fix the camber again, and if that took more than a half a turn, decide if I want to set up the bumpsteer measurements again. I previously had the bumpsteer almost completely banished and then I started changing things again! And that's only the rear end. Not even gotten to talking about the front yet. And this has been going on in the context of me discovering a seized bolt in the LHR FUCA bush at the upright, hence needing total disassembly to replace that bush and the others that were not far away from the same outcome, replacing sphericals in the front end and making a mistake that resulted in needing to do it again, which is only half done right now. It's a selfmade nightmare. Only have self to blame, etc etc. But regardless, I am so complelely unable to utilise the services of a normal wheel aligner that I have no choice. I haven't found a shop in my city that does "race" alignments - and by that I don't mean I want my car to be set up for racing, but the set of adjustments that I have available and that need to be used to do the alignment are the same as you'd find on a race car. I haven't looked everywhere, but there doesn't appear to be the equivalent of the motorsport focused shops that are present in Sydney and Melbourne. And such an alignment would cost $300, and you only want to do it once in a while, and you don't want to find out that you have to replace bushes and bearings and such while you are spending that $300 so you have to come back and spend it again a week later. So I stay living in my self made nightmare for the moment.  
×
×
  • Create New...