Rebuilding An Xu10j2te

[pablo 0]

from another thread (http://forum.205gtidrivers.com/index.php?showtopic=88114)

 

rgy - flat top pistons, 7.9:1/8:1 compression, 145bhp

rgx - dished pistons, 8.5:1 compression, 150bhp

 

This is a pic of my dished pistons with a clear lip of crud at the top, but I guess as the rings arent at the top of this piston this means diddly squat and the piston may come right up to deck height.

 

[Jamal 2]

from another thread (http://forum.205gtidrivers.com/index.php?showtopic=88114)

 

rgy - flat top pistons, 7.9:1/8:1 compression, 145bhp

rgx - dished pistons, 8.5:1 compression, 150bhp

 

This is a pic of my dished pistons with a clear lip of crud at the top, but I guess as the rings arent at the top of this piston this means diddly squat and the piston may come right up to deck height.

 

 

Now I'm really confused

 

If these are the dished RGX pistons, what are on my pic? My engine is out form a 96' Xantia TCT, the RGX can be easily read on the block where the engine number is.

[welshpug 1,657]

thought I was correct

[pablo 0]

your block even looks different to mine Jamal. Ive never seen an engine code on mine though.

[Ant 2]

Engine code should be to the right of the oil filter, just above where the block is attached to the sump - or it is on the 2 RGX lumps ive seen.

[Jamal 2]

your block even looks different to mine Jamal. Ive never seen an engine code on mine though.

 

It's on the front of the block under the starter motor, near to the oil inlet, above the sump, engraved into a flat surface

Only can see PSA on the pic

[pablo 0]

must take a look!

[Jamal 2]

must take a look!

 

Yeah, I will take a pic about it. Somehow

[jonnyturbo 3]

not sure if this will help or not but i had flat top pistons on one engine but my next engine had dished but i used the head from the old one as i had the valve stems replaced.

[pablo 0]

Had a look there mine is RGX alright. Pistons are dished with a flat bit on side (rear) only. front of the dish is curved. So guess its alright then

[taylorspug 7]

Pablo, do you want to sell the lower compression flat top pistons and rods? I think you may have replied on my wanted post for some actually! I may be able to get hold of a set of dished ones if you fancy a straight swap?

[Jamal 2]

Mine is RGX too.

 

So why the difference?

And exactly, what is the dished and what is the flat type piston?

[pablo 0]

Pablo, do you want to sell the lower compression flat top pistons and rods? I think you may have replied on my wanted post for some actually! I may be able to get hold of a set of dished ones if you fancy a straight swap?

 

Now Im really confused, I thought the dished were the low comp ones? As per the higher hp RGX engine.

 

same crank I presume?

[taylorspug 7]

No the higher hp comes from the extra compression in this case. RGX is higher comp and higher power. The flat top pistons dont come up to deck height, whereas the dished ones do. In effect, the dish has been added to raise the compression.

 

Cranks are the same yes.

[pablo 0]

so whats the advantage of the lower compression pistons? Ability to run higher boost?

[Jamal 2]

No the higher hp comes from the extra compression in this case. RGX is higher comp and higher power. The flat top pistons dont come up to deck height, whereas the dished ones do. In effect, the dish has been added to raise the compression.

 

Cranks are the same yes.

 

So mine is the dished one, because it comes up to deck height(as seen on pic)?

And what about Pablo's pic?

[pablo 0]

yes mine is the same mate. Probably does come up to deck height alright. Ill double check when Im putting the head back on.

[Jamal 2]

yes mine is the same mate. Probably does come up to deck height alright. Ill double check when Im putting the head back on.

 

Ohh I'm so stupid!

Remember this pic:

I missed the pics right botttom. There can see the flat bit a little.

 

On this pic can easily see, that booth mine and yours are the same:

 

I'm so so stupid

Sorry for the flood...

[taylorspug 7]

so whats the advantage of the lower compression pistons? Ability to run higher boost?

 

In theory yes you could run a bit more boost, although even the higher comp engine would take a bar no trouble id imagine. I dont want them for an 8v turbo anyway, ive something else in its early stages and the flat tops are ideal for me.

[pablo 0]

Ok mate Ill do a straight swap on the pistons no bother if you cover postage, Id rather have the dished ones if they provide more hp out of the box. Ill not be running silly hp anyway, just a bar boost on std turbo. You need the rods and caps too Im guessing?

 

Had a quick inspection of my RGY block, confirmed it actually is an RGY block (the one Im rebuilding) and checked the cylinder walls. Can still see honing marks but there is a definate lip at the top of the cyclinders, just enough to catch with a fingernail say. Not sure what this means in reality. Can I use slightly larger piston rings and get them bored? Or is this ok? Or is it scrap lol? Hard to know!

[jonnyturbo 3]

either chance it or get a new block imo

[pablo 0]

would rather not chance it as it would be a monumental waste of time and money

 

Any measurements I can take etc to determine its state? Or handier just to send it off and get it looked at?

[pablo 0]

Well I took the block and crank up to my local engine rebuilder and he said crank is 100% but the block would really need reboring and oversized pistons fitted. As this is now upping the budget rather considerably Ive decided to knock it on the head. So if anyone needs any parts just let me know.

[jonnyturbo 3]

not worth rebuilding anyway tbh mate as long as its running right just rag it but also make sure you have antifreeze in as that was my downfall and engine died 2 days before xmas

[pablo 0]

why do you think Ive just put a new head gasket in lol? Moved it out of the garage to do some work in the garage, no antifreeze, cold snap started, car completely froze up!

 

Have it running now, new headbolts, gti-6 MLS head gasket, new TPS and its running better than ever. I noticed that the R5 intercooler has a flap inside it that wasnt opening so the fukker was running with no intercooler basically. Have jammed the flap open now.

 

Had it up a known road last night. Pulled 100 (kmph ) at the top, same as my E46 M3 done, so its fast!

 

Car is now running the best it ever has, woohoo!