Jump to content
SAU Community

Recommended Posts

  • Replies 44
  • Created
  • Last Reply

Top Posters In This Topic

No. .0005" extra is much better than .0005" too little. The clearance they specify is normally the minimum clearance that will work in the vast majority of situations. In all honesty, most of the cheap bore gauges that people use to check a bore are only accurate to .0005" anyway and depending if the block was allowed to cool before the final honing and measurement they can move that much anyway.

Should I worry?

the cp,s will run .004 clearance at the pin if the bore measures right on 86mm exactly. get a competant machine shop to measure the bores , hone the bores correctly and the gaps at what youve stated will work fine. a correct hone finish would be my favor over a tad more piston to bore clearance. we have run the cp,s at .006 thou clearance after a few teardowns and you can hear them at that clearance and dont seem to upset the knock sensor.

i used trust/os pistons. at 1.9thou they are fine. but i didnt like the fact that they came with no ring spec sheet. and was told but the trust dealer at the time they are gapped to suit the 1.9thou bore.....

done 50,000km at 1.6 bar no drammas as yet :laugh:

  • 4 weeks later...

hey guys, so to steal the thread but i am dropping my CPs off tomorrow at the machinist, my mate/ building adviser has not used CPs before. im looking at around 350kw-400kw at rears and spinning to around 8500 tops.

can i get an idea of what a couple of u recomend as far as piston to bore and ring gaps

and how much better is the ACL oil ring over the CP.

Mate im a big fan of the ACL's but no bastard wants to use them. The thick upper rings seal really well...even in big clearanced drag race stuff and as you say the oil control is much better than the CP's as even at 16 thou the CP's tend to 'float' on the bore.

Ha, ha I used em (ACL's)!!!

Built mine near the end of last year and have put 10,000k on it so far. Got the block machined to 86.5 and run a 3.5 thou piston to bore clearance, then built the rest up myself.

I was a little generous with the compression ring end gaps 17 top, 21 thou second ring, but it seems to work well.

Dynoed at 363RWKW at 20psi and revs up to 9000RPM. Daily driver since 2004! and still is.

any opinions on my application i am tending to go with dirtgarages slightly larger clearnces, meeting the manufactorer in the middle..

as i have said its going tomorrow so an opinion would be great

its in a 26 at 86.5

Mate im a big fan of the ACL's but no bastard wants to use them. The thick upper rings seal really well...even in big clearanced drag race stuff and as you say the oil control is much better than the CP's as even at 16 thou the CP's tend to 'float' on the bore.

Whereabouts can I order the ACL rings from and are they piston specific or just bore specific? Meaning do I ask for an 86.5mm set of ACL piston rings? I have no problem spending the extra on them.

Jason.

  • 4 months later...

I started my gapping process only to find out that when I place either the top or second ring in the bore that the gapping is bigger than what was recommended i.e top - 17 thou, second, 19 thou and oil around 16 thou. I am guessing that means that the machinist honed my bores too big allowing the rings to have a bigger gapping. What advice can you'll give me to correct this and please don't tell me to get 86.5mm and rebore? Can I get some ACLs that would fit the build? This has got me really frustrated.

Back to basics. You need to measure the pistons witha micrometer and see what cylinder bore to piston clearance the block was setup with. Check your piston "recommended clearence" data. It will be between 2.5-4 thou depending on the brand and material of pistons. If thats ok then look at rings. Something not right and to proceed without the propper checks will end up in disaster.

Wouldnt you want a steel gas nitrided top ring rather then a chome/moly coated ductile iron top ring?

Or do CP offer a proper top ring now? like acl and mahle use. Out of curiosity, last time we used several sets of CP's they didnt offer a good top ring.

I would do what shane said and get a set of acl rings that have the same thickness about 1.5mm, 1.5mm and 2.7mm from memory???...but I would measure the thickness of your rings now with verniers to see.

Edited by r33_racer

Sorry for hijacking the thread, but I have a question....

Since most blocks when bored/honed are done with a torque plate(well if done properly)...if you were being precise with your ring gaps, then it would make sense to check and set ring gaps whilst a torque plate is bolted to the block right?

Does anyone do that? or only pedantic builders goto that length? I understand the bore distortion might only be .0005 or thereabouts going from torqued to untorqued.....but still...might only be half a thou, to some thats not much, to others thats alot.

Been thinking about it, and was curious if anyone bothers?

Sorry for hijacking the thread, but I have a question....

Since most blocks when bored/honed are done with a torque plate(well if done properly)...if you were being precise with your ring gaps, then it would make sense to check and set ring gaps whilst a torque plate is bolted to the block right?

Does anyone do that? or only pedantic builders goto that length? I understand the bore distortion might only be .0005 or thereabouts going from torqued to untorqued.....but still...might only be half a thou, to some thats not much, to others thats alot.

Been thinking about it, and was curious if anyone bothers?

I've done it both ways on an RB and the difference is negligible plus its awkward to square the ring properly with the torque plate fitted as it's only slightly larger than the bore size.

appreciate the response mate. did you manage to get those pics of the rd28? or too busy? no issue if not.

Have you ever checked bore with and without torque plate to see what variation there is?

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

    • So where is this message group so we can organise another meet? Keen to come along and catchup. Might eventually be in a skyline again next year, but the Mustang will have to do for now. Also need to get the WRX back on the road. Stupid f**king money pit that thing is.
    • Stock equivalent turbo replacement is a bit of a nightmare. The old Hitachi ceramic things were pretty good for their time, but they have primitive, vintage aerodynamics. The only thing they have going for them is a light turbine**, and there are plenty of other light turbine options these days, in both materials and CNC manufacturing methods. So, the old stocker makes absolutely no power at all compared to its physical size and its (not very low) boost threshold and response. ** and the ONLY thing that was good about the ceramic turbine was that it was light. In all other respects it is a nightmare. To get a turbo that is anywhere near equivalent in terms of power capacity (ie, to avoid it being "bigger" and needing tuning/fuelling/etc) you have to physically downsize. And that is not a "stockish" replacement. Doesn't just fit where the old one did. At least a frame size down, probably need a new dump, probably need new inlet and outlet piping made on the compressor side, new hose connections as D said above. I say, if you have to suffer that much work, you might as well do the same work to fit an even bigger (than stock) turbo, have more power (and hence have to do injectors, ECU, etc), and love life, instead of suffering with stock power levels. Or, you get a light highflow from someone like Hypergear. A highflow that has not been pushed too far from stock. There are still modification consequences here though. HG's cores are smaller than the massive Hitachi core, so it is shorter, moves the compressor housing backwards and requires mods to the air side piping. Plus new hoses. Looks stock, mostly fits where the stock one did (with the previous caveats mentioned), makes a bit more power but can be run at stock boost levels and not cause too many ECU problems. But, seriously. It's 2024. Like - 25 years since the R33 came out. It's time to put an ECU in it. I Nistuned my car (on RB20 ECU then later again on the Neo ECU) and it was the single best thing possible for minimal money. Dial out the R&R bullshit, fix up the fuelling and timing to make it more efficient for normal driving (cut fuel consumption by >10%). Nistune is not an option for you unless you change the ECU, so you might as well just do a standalone. it will be worth it. And then you can tune it up to the limits of the injectors and AFM, which is pushing 200rwkW and enjoy some actual squirt, instead of the lazy barge-like motion you get from a stock engine, turbo and management.
    • He can't post pics until he's at 10 post count.
    • Welcome James.....will be interesting to see how much fun there is in the project. .....where's the pics?
×
×
  • Create New...