XU10 8v Head corrosion

[DamirGTI 359]

Picking bits for building 2.0 T engine .

 

I have one head cracked between the valves , and seems like the second spare head is kinda questionable too ..

 

Thoughts on this one please ?

[DamirGTI 359]

.... pitting on this area seems very close to the head gasket fire ring .

 

Not sure if it needs welding , or juts a skim to clear up a bit .

[petert 630]

Dig out the tooth decay and weld it. You can save just about anything these days.

[DamirGTI 359]

Welded up , skimmed ..

 

But now measuring the combustion chambers i'm down 5cc on this head compared to my other 2.0 T head .

 

This welded head is now 28cc , and my other scrap head measures 33cc (seems like virgin aka non skimmed) .

 

Roughly how much of a CR increase does 5cc makes out on XU10 8v ?

 

I've option of making either RGY or RGX engine (that's if i can save/press out RGX pistons as two of them seized up in the block) .

Would prefer RGX because of better squish clearance by using RGX pistons , but with this 28cc head in combination me thinks CR will be bit too high for turbo engine ?!?

 

Anyone knows how much cc is in the piston dish volume on RGX piston , and how deep down the bore is RGY flat top piston at TDC please ?

 

D

[SRDT 233]

I can only find the same compression height of 40mm for both pistons but it's only on one document so there could be an error.

Both types are fine on a stock engine but early flat top RGY pistons are said to be stronger, maybe the lower CR of RGX pistons helped mitigate knock and PSA could get away with a cheaper and weaker alloy.

 

Looking at PSA documents CR with RGY flat top pistons is 8.5:1 vs 7.9:1 with RGX dished pistons.

http://www.ckc.dk/pubs/MAN008930.pdf

Page 299 for RGY and 316 for RGX

[DamirGTI 359]

Strange , i always thought that the early RGY was the low compression engine and the later RGX was the one with higher compression

 

Much of the specs and technical data on the net says it's the opposite too , very confusing engine !

 

I have here only RGY engine in bits and pieces , need to drag the 406 at my place and see what's inside the RGX variant .

 

Now that reminds me , i have an OE PSA book with piston specs for entire XU engine range , need to find it hopefully there's some info there for 2.0 T engine .

 

Was there ever repair manual for this engine ?

I couldn't find any , none in the Haynes books for 406 only some limited info/data about 2.0 T in early blue book for XM .

 

Me thinks they went for different piston design on later RGX engines to lets say "modernize" the engine a bit , to add some engine response off boost , improve overall fuel mixture making it more homogeneous , adding some turbulence to enhance heat transfer , more knock/detonation resistance and more power (yet they only managed around 6hp with comparison to RGY which really isn't much) .

Quite a few positive benefits from improving squish clearance on an engine .

 

D

 

 

[SRDT 233]

Looking at the power and torque curves the early engine looks restricted to ensure constant torque then constant power. The later engine has higher peak values but also more rounded curves.

 

[DamirGTI 359]

... back on this one above - the graphs !

 

Been thinking ...

 

Any ideas what might make the difference between the two , ECU calibration or mechanical stuff ? or mix of both ..

 

They do have different ECU's , no idea about the maps in the EPROM chip .

 

Mechanically , difference is only pistons and CR : 

RGY 8.5 with pistons about 4mm below the deck .

RGX 7.9 with pistons flush with the deck . 

... sound a bit odd that this alone might make such power/toque difference , but i might be wrong . 

 

Car came with the RGX engine and RGY ECU ... haven't tried driving it as it was non running resto project .

I have the right RGX ECU too , but need to unlock it first .. 

 

Also curious what might mixing the ECU do , make one engine performing kinda like the other or ?!

 

 

[SRDT 233]

It's only pistons/CR and ECU software that changed but don't forget that the ECU is also doing boost control so it's not hard to grab 5hp and 10 N.m.

I wonder if the lower CR is to lessen knock so that there isn't as much timing and boost pressure adjustments that can be felt by the driver.

[petert 630]

The RGY is 8.5:1 with a 33cc head. If you fit a 28cc head to that block the CR will be 9.1:1. I can't imagine that being an issue.

Edited Wednesday at 11:00 PM by petert

[DamirGTI 359]

I wont be using that head .

I found another one , actually complete engine for bits and pieces , as i needed one piston too so took the lot .

 

Head will be pretty much stock spec chambers wise so 8.2 - 8.4 maxi id say with a skim on the head and the block .

But i did some porting work on it and 3 aingle seats .

 

Was reffering on the graphs above which Mr. Baptiste posted .

Curious about the difference in the power/torque between the two engines and what might be the prime suspect ! 

[DamirGTI 359]

3 hours ago, SRDT said:

..don't forget that the ECU is also doing boost control so it's not hard to grab 5hp and 10 N.m.

Hmm , so it seems to be more like the ECU tweak ? different boost control between the two ECU's ?

 

RGY graph does look a bit "artificial" , made with clear intention rather than engine natural character .

 

I can build either of the two engines as it's just pistons swap .

However RGX variant seems better to me cause of squish improvement with newer piston design .

 

But the torque seem to come up little bit later and goes down sooner on the RGX than it does on the RGY .. i "think" id like it to keep going for a little longer as it does on the RGY ! 

Edited Thursday at 12:26 AM by DamirGTI

[welshpug 1,722]

they were badged as CT in many instances, ideal for an auto box in a wedgy barge..

 

 

trying to mimic the character of the V6 engine without the cost and fuel consumption. 

[petert 630]

I've often wondered how cool it would be to put an Mi16 head on an XU10J2TE block and add suitable manifolds, in an Xantia CT.

[welshpug 1,722]

Dan (DCC)   has done something close, gti6 head on J2TE block and crank, its going in a 205 though.

[DamirGTI 359]

Indeed , that will make it pretty much "cheap" T16 .. too bad such combinations are bitch to make road legal here in EU 

 

I have 3 Mi16 heads doing nothing but collecting dust ...

 

Still , if going by the flow chart for XU10 8v head , porting work and 3 angle seats seems to make quite a noticeable difference .. some percentage will surely still remain "stuck" with OE inlet/exhaust but hopefully it'll spool up little bit faster and pick up some more umph in the mid and top range . 

[wicked 105 3 Cars]

Don't forget to use the dkz gti cam instead of the lazy original...

 

I would opt for the RGX version with higher compression (which is still low compared to more modern engines). The ecu's differ more than only the mapping; afaik the RGX has newer processor and more detailed maps, so more refined.

Don't draw too much conclusions from the graphs, they are likely less accurate than you'd expect. 

You need an external boost controller anyway to make these engines come alive...

 

[DamirGTI 359]

I have two DKZ cams, but sadly both have one or more worn lobes .
I also have RFX (XU10J2), DFZ, and D6B cams, all of which are in good condition.

From what I've read, the RFX cam is generally considered the next best option , after the DKZ .

What changes in terms of driving characteristics with the DKZ cam compared to the standard OE cam ?

I found some old forum posts where people said the engine would rev higher with the DKZ cam but also that the turbo would  start spooling later in the rev range too .
The engine is going into a 406 rather than a 205 , so it'll be moving twice the weight .

I won't be using a bleed valve for sure , but  considering one of those "dawes device" variants with the spring and ball inside .

Proper electronic boost control unit maybe later as funds are a bit tight at the moment .

[SRDT 233]

The stock cam of choice was from the early non cat XU10J2 R6A, on markets where it was sold anyway. As for the ECU hardware upgrade I think it was done after the switch from RGY to RGX, you can still find RGX ECUs with the removable 28 pin EPROM. On the 406 and 806 you can even use older ECUs with the newer software inside so that they can drive the A/C compressor clutch.

[petert 630]

A friend used Catcams 4912533 and an external boost controller. It went ok, but not as good as it should have, as he didn't remap it.

[DamirGTI 359]

I thought as much , if changing the cam for another one with the more lift on inlet , stock ECU might not be able to cope with it to the full potential at least . 

If it's just fuel , aka going lean then increasing fuel pressure would work Id say , but ignition is tricky bit ..

 

How about DFZ cam ? that one has more lift on the exhaust , and same lift on inlet as the stock 2.0T cam from what i remember .. overlap difference - no idea !

Any benefit with more exhaust lift on turbo engine ? 

 

Post with regards to DKZ/RFX cam instead OE , says as suspected shifts boost upper in the rev range .. not sure Id like that on heavy car such as 406 :

Edited 10 hours ago by DamirGTI