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Xu10j4r-xu10j4rs Differences


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29 replies to this topic

#1
SPofRCLD

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hello everyone,

I am in the middle of a pretty nice rebuilding project of a 205 gti.
now, i have a nice rebuilt 1.9 engine in the car, but seek for something a bit newer and kind more reliable
whilst having more power,
which got me to the xu10j4rs.
NOW, as I AM living in ISRAEL, things become a bit more complicated than just getting the engine, putting it in, and rewire everything..
the major issue is that none of these engines cant be approved on the 205 legally, but, i am an israeli, so i have my ways of makin it legal,
the thing is that either one of them will cost me almost the same to buy, and exactly the same amount of money and effort to legalize,
but the RFS is a highly rare engine to get your hands on in israel, so a thought crossed my mind, to take
the standard RFV xu10j4r which can be found in large amounts here as we have a lot of them xsara/xantia or whatever other car that
that engine can be found in..

now my question is will i be able to get close to the RFS power figures with mild changes to the RFV like manifolds and cams from a RFS engine?
what are the main differences between the engines, as ive read a lot of posts here that state that sometimes the RFV head is a better head then the RFS?
do i need to get the engine management from a RFS, or can i keep the RFV, and chip it? how to deal with the 6000 rpm cutoff then?
and basically any other good advice you can give me will be highly appreciated, as im pretty lost here...

Thanx,
Andrew from Israel!

Edited by SPofRCLD, 30 December 2008 - 03:15 PM.


#2
welshpug

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http://forum.205gtid...s...=87635&st=0

http://forum.205gtid...s...;show=&st=0

:wacko:

#3
SPofRCLD

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thank you for the quick reply,
read both topics, dont quite answer the questions i asked..

#4
SPofRCLD

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could someone please shed some light on this matter? i have read most of the posts on this forum that include the xu10j4 in, and didnt get
the final conclusion to my questions..

#5
petert

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now my question is will i be able to get close to the RFS power figures with mild changes to the RFV like manifolds and cams from a RFS engine?


Yes. Put bigger cams in than RFS though. They're still very mild.

what are the main differences between the engines, as ive read a lot of posts here that state that sometimes the RFV head is a better head then the RFS?


Bugger all in the head. Just minor valve sizes. Ports are huge like Mi16. Valve sizes are the same as Mi16.

do i need to get the engine management from a RFS, or can i keep the RFV, and chip it? how to deal with the 6000 rpm cutoff then?


Use after market ECU and bigger injectors.

#6
magic

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The xu10j4rs makes 163 hp the xu10j4 132 hp
So with a inlet and exhaust manifold swap from xu10j4rs to xu10j4r you can get 98 kw at the wheels .
I saw it on a dyno day here in Sydney ..you need to remap the xu10j4r ecu
the rev limiter is on this engines 7400 rpm , thats how i set it when i remap a xu10j4rs or R ecu

#7
Anthony

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Can I please remind people that this is a technical section of a CAR related forum, and not the place to be "discussing" sensitive political issues? Thanks.

#8
SPofRCLD

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thank you anthony,
and thanx to petert and magic for spot on answers.
really appreciated!

#9
jengis

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This is the way I see it - If you want to get RFS specifications you need to get the RFS head and put it on in place of the RFV head. But if the heads are as rare as the complete engine thats no help to you!

As for the differences, the searches should show that there are some significant differences - like very large ports and bigger valves with double springs and different cam profiles...etc. The reason some say that the XU10j4r head is better is when you need a blank canvas to customise your own port shapes. The smaller ports allow you remove only the material you want to remove.

Its been said that by using the well designed manifolds from the RFS is a good improvement on the lower spec engine but I don't know how much of the power difference is due to head and how much to manifolds - you will probably never know for sure without trying yourself. The tubular exhaust mainfold in particular is quite obviously better than the RFV one

As for the ECU, is the rev limit on the XU10j4r (RFV) really only 6k??

#10
B1ack_Mi16

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I tohught it was the 1.8 16V head that had smaller ports, and that the RFV and RFS engines have almost identical ports apart from small differences in valve sizes.

An RFV with manifolds and camshafts from the RFS should be almost equal to the RFS itself.

Then just get it mapped to the new specs or get an aftermarket management...

#11
jengis

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I tohught it was the 1.8 16V head that had smaller ports, and that the RFV and RFS engines have almost identical ports apart from small differences in valve sizes.

An RFV with manifolds and camshafts from the RFS should be almost equal to the RFS itself.

Then just get it mapped to the new specs or get an aftermarket management...


You are right, getting mixed up. :lol:

looking back at Sandy's measurements, the ports are only slightly smaller in the RFV, but different all the same. But perhaps not by as much as i was making out, and yes, the XU7's are significantly smaller again.

#12
petert

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This is the way I see it - If you want to get RFS specifications you need to get the RFS head and put it on in place of the RFV head. But if the heads are as rare as the complete engine thats no help to you!


The RFV port sizes and valve sizes are basically identical to Mi16, but has several advantages over Mi16 - lighter valves and smaller combustion chamber. RFV engines are a bargain.

#13
Guest_JasonS_*

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Just going to jump in on this thread rather than start another similar one as such.

My question is:
Does anyone know if there are any valve clearance issues by using the GTi-6 head (XU10J4RS) on the XU10J4 bottom end? As i'm sure there are differences in the pistons between both, i.e valve cut-outs on the GTi-6 b/end?

#14
DorgersGTI

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here an other thread jumper,

How can we declare the differnce in compression ratio?

From what i understand the RS has an ratio of 10,8:1 and de R has an ratio of 10,4:1

Is it in the head or in the pistons?


I have an seized rfs engine and i want an rfv block and put an rfs head on it.

Greeting Dennis Orgers

#15
large

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From the looks of it an S. :ph34r:

#16
welshpug

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the 10J4R have dished pistons.

#17
Guest_JasonS_*

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the 10J4R have dished pistons.


So therefore no issues with valve clearance if using an RS head on an R bottom end?

#18
welshpug

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no, but the compression will be lower, but not if you fit RS pistons to get the compression back up, or if you want cams with more lift @ TDC some aftermarket ones with deeper cutouts.

#19
B1ack_Mi16

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Just going to jump in on this thread rather than start another similar one as such.

My question is:
Does anyone know if there are any valve clearance issues by using the GTi-6 head (XU10J4RS) on the XU10J4 bottom end? As i'm sure there are differences in the pistons between both, i.e valve cut-outs on the GTi-6 b/end?


The GTi6 head on top of the S16 XU10J4 engine will up the compression to approx 10.8:1 so same as in GTi6 engine.
The S16 head has some more chamber volume than gti6 one.

#20
whizzer71

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The RFV port sizes and valve sizes are basically identical to Mi16, but has several advantages over Mi16 - lighter valves and smaller combustion chamber. RFV engines are a bargain.


Ive just gat my hands on one of these engines,over and above 6 manifolds and a pair of cams what else can I do (Basic stuff/mods) to wring more power out of it ?

:D