Xu10-j4r Heads Flow Potential

[sorrentoaddict 1]

Hi everybody,

 

browsing through the "search" archives, I just read that the

XU10-J4R head has 34.60mm Inlet valves combined with the thin 6mm valvestems.

 

If this is true, doesn't this make the XU10-J4R head potentially the best-flowing head

of all XU 16v heads ??? (or, to put it otherwise --> of all XU 16v heads this can give

most power with least inlet cam "area")

 

Personally I've never seen one of those heads stripped on a bench.

Has anyone of you already stripped & measured a XU10-J4R head ?

 

Are there any differences in the ports sizing, ports shape, or valvetrain ?

(I mean differences to the XU10-J4RS head a.k.a. GTI-6 head, as these are

obviously a very similar if not a totally same casting.)

 

This all sounds very interesting, as on some series of Peugeots sold in Germany

in 1998-1999 (german market spec. !), there is a XU10-J4R engine fitted with 11.0 : 1 C.R.

from factory...

 

It is also the biggest factory-fitted C.R. I have seen of any XU 16v engines, isn't it ?

 

So, I was just thinking, maybe with a CATCAMS 4903156 inlet camshaft fitted,

with some slightly bigger throttle-body plate (or maybe a GTI-6 inlet manifold ?!),

and some playing with the exh.cam timing, this engine could be a nice and cheap

everyday-use motor, with cca. 150 HP and a serious mid-range transient response,

legacy of those longish inlet tracts and 11.0 : 1 C.R. (which would make it a good

proposition for heavier cars, or longer gear ratios, suited to highway use etc. etc.).

 

has anybody fettled with these lumps ? what do you think ? what MOTRONIC version

do they run ? is the bottom end more similar to the XU10-J4, or to the XU10-J4RS ??

 

P.S. to make things even more confusing, in some Xantiae/406 versions this XU10-J4R

versions came with plastic inlet manifolds, whereas in some other Xantiae and many 605

this engine comes with an aluminium inlet manifold ?!?

And in some other places versions of this engines are denominated as XU10-J4R/L...

can it be possible that this "L" stands for alloy inlet manifold ?

 

Thankful for any experiences & sorry for the long post

 

 

Cheers

 

 

Alex

[sorrentoaddict 1]

Forgot to add: in Phase-II Citroen XM 2,0 16v Station-Wagons

(don't know if this is the same in the "normal" XM 2,0 16v), this

engine XU10-J4R comes with a special, VERY long inlet aluminum manifold,

(with very curvy and forward-reaching runners), which is obviously designed

for even more torque for the heavy XM SW. (and it makes use of the vast

underbonnet space available under the XM hood...).

 

Whereas, in the 605 2,0 16v, it comes with a shorter alloy manifold, although

the 605 offers the same huge space under the hood.... (?!)

 

(I will try to post some pics of these engines if I can find them on the net,

to see what I mean.)

 

Any ideas how this "XM-special" version of the XU10-J4R might be

called ?

 

Have come across XU10-J4R/L-Z, too but I cannot really be sure what

does it relate to ?

[Sandy 189]

I rate the XU7J4 and later XU10J4R heads a s good for porting, because they have smaller ports than Mi16/S16/GTi6 head, which give the man/woman working the head more of a blank canvas to achieve what they think will work best. At low-mid revs I would expect them to work better in standard trim too. I would be surprised if the XU10J4R head works very well at peak as it is though, it's a bit rough on the inlet side.

[sorrentoaddict 1]

I see, OK, so, apart from the finish-detailing of the ports, AND the inlet port size diameter,

everything else seems to be 100% same (as casting, studs, valvetrain etc...) when compared

to the GTI-6 head, true ?

 

Thanks heaps !

 

Alex

[Sandy 189]

Basically. The base model heads don't have spray bars for the cams or the servo pump.

[robbiecfc 0]

Basically. The base model heads don't have spray bars for the cams or the servo pump.

 

Slight hijack of thread...

 

Can the spray bars be retrofitted to the XU7J4 head? Are they needed or recommended?

[sorrentoaddict 1]

Considering (at least on XU10-J4R) that the inlet lift is a VERY modest 8.70mm,

the spray bars are definitely not needed. If one is to install a 10.00+mm lift

inlet cam, then they seem to be a must-have.

 

Havint not yet seen a XU10-J4R nor a XU7-J4 head myself, cannot answer this,

but it sounds like a relatively easy adaptation if the oil galleries are located

equally as on the other XU16v heads.

 

It seems that generally the XU10-J4R might be the best cyl.head to start with

for serious applications, as you have the 6mm stems AND the big valveheads

at the same time, and as a bonus also a "meaty" inlet ports material for some

serious porting job...

 

personally I am after the torquiest XU16v possible for a daily transport in a very

big and heavy french car, which raises some issues about a "XU13-J4R" project

for the nearish future. Basically XU 16v performance, with an added cubic capacity

and powerband dropped-down for cca. 1,000-1,500 rpm (which the narrow inlet

ports on the XU10-J4R are probably all about at the first place...)

 

 

Alex

[Mandic 0]

Alex,

 

XU10J4R has also the longest conrod at 160mm.

 

Cheers

 

Ziga

[B1ack_Mi16 67]

Alex,

 

XU10J4R has also the longest conrod at 160mm.

 

Cheers

 

Ziga

 

That would be 158mm on XU10J4R and XU10J4RS

[Richie-Van-GTi 70 2 Cars]

That would be 158mm on XU10J4R and XU10J4RS

 

is this right? I have an xu10j4r with xud crank and the pistons are coming proud of the block which is causing issues, if its 160 then it would explain a lot and I can then put 158's in, if they are 158 then is there a 156 conrod I can swap to?

[welshpug 1,622]

That would be 158mm on XU10J4R and XU10J4RS

 

so which has a 160mm rod? someone asked over on the 405 forum what the difference was between the 1.9, 2.0 Mi/S16 and gti6 rods.

 

shorter rods + higher piston speed right? but conversely the need for a taller piston.

[Mandic 0]

Sorry,

 

B1ack_Mi16 is right, 158mm for J4R and J4RS and 152mm for J4

 

Dont know why I always think they're 160mm

 

Cheers

 

Ziga

[welshpug 1,622]

so the relative piston speed is lower for the R/RS than the older Mi, is that the same for the 1.9?

[Mandic 0]

1.9 has 143mm rod and 88mm stroke

 

Cheers

 

Ziga

[Sandy 189]

Mean piston speed is only a function of stroke.

 

Piston acceleration curve is a function of stroke and rod length relationship.

[sorrentoaddict 1]

thanks for this info.

 

this means that the XU10-J4R has a RL/S

ratio of 1.818, which should make it a better proposition

for sustained high-rev use, too (which is not an issue here

as I was considering a torquey engine with a meaty powerband

suited to a heavier car etc.. etc..).

 

however, such a "tall"-ish (at least by XU9-J4 standards...) RL/S

ratio is also to be found in the XU7-J4, which is a very revvy and very

sweet-sounding engine itself.

 

In reality, this means that the XU10-J4R is an excellent "universal"

engine both for:

 

- applications that are often ran at high-revs (should

sound sweet with that long rods - of course if a wilder inlet cam AND opened-up

inlet ports are used, possibly with an adapted XU9-J4 inlet manifold (?!), AND,

 

- if its inlet ports are left as they are, to be used as a torquey engine

with strong mid-range response and a healthy 140-145 BHP if ran on the

standard mapping with a de-cat pipe, for example...

(with of course a slightly less timid inlet cam installed, eg. to use one from a stock

GTI-6 engine - which can be found fairly cheap).

 

- if it is the earlier version of XU10-J4R (with oil-squirter nozzles under the pistons),

it should make for a wonderful base for a "budget" Turbo XU 16v engine, as the smaller

inlet ports should (at least in theory) maintain the high inlet gas velocity while the Turbo

is lagging, making it a very lively engine. Again, one could use a GTI-6 inlet cam, making

a good cam "area", or maybe even with the timid 8.60mm stock camshaft it might be very

good for a not-too-ambitious Turbo application (if there is such a thing at all as a "not-too-ambitious-Turbo-XU-16v-application" ). In this "case", the only real internal mod would be to employ different

(shallower) pistons for lower C.R. while maintaining good squish and you have a cracking

good base for a Turbo engine. The only advantage of the XU7-J4 in this context is its lower

weight (which is why it is used as a base for the PSA WRC), but the iron-block of the XU10-J4R

is (for us "budget"-oriented builders) a blessing as it is so much more reliable for Turbo applications,

rendering its excess weight a feasible trade-off...

 

As for the long RL/S ratio, 1,82 is actually very close to what some very serious engine

tuners consider to be the "golden" compromise for a sport-oriented engine of today's era,

(cue some Type "R" engines as of Honda's recent past, but also some other examples),

so it is another "pro" argument for this engine --> making it maybe an excellent "tall block" base

for a race engine too (if it is the version with the oil-squirters, of course).

 

On the other hand, the RL/S ratio on the XU9-J4 engine is damn close to the magical "phi"

number, considered a "golden rule of balance" in geometry and generally in engineering.

 

I am getting one for myself, as the thought of 6mm valvestems is opening a new "sea"

of possibilities, increasing the flow without having to use too-large inlet valveheads (which

are deemed to sometimes suffer from flow obstructions from each other, and also from adjacent

cylinder wall closeness -- yet, the big valvehead "philosophy" is also, admittedly, far superior in

the low-lift-flow "department", because it is a function of the valve circumference etc.. etc..).