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Turbocharging XU10J4R...
Currently looking at the 2.0 16v engine/box sat around out of the parts cabriolet & wondering if refreshing that and adding some boost would be a fun project to go in the White XS.

I believe the engine is going to be an XU10J4R (it's from a Ph2.5 306 Cabrio.) and have heard some good things about them although not had a moment to research much more than some YT videos and a quick squiz on here.  Just after opinions/advice about how much power the stock bottom end can handle, potential weak points, OEM part-swap upgrades (like HDi rods in an XUD sort of thing) etc.

Plan would be to pull it apart and give it a refresh since it's done 160+k and felt tired compared to the 50k lump in the green cabby, so any bits to address while I'm in there would be good. (If I'm going to be swapping rods for example, rather find out before I buy new shells).

Cheers for any advice/experience. I'm off to do a bit more research now lol.
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The XU10J4R is quite a solid engine n the bottom end could handle more power no problem. It's already quite high compression though (10.4:1). If you're serious about adding boost to it I'd search out at old threads (on wider web) about charging of the RS engine, which has a stock compression of 10.8:1.
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Yeh lots of research to do, but turbo/supercharging the J4R is pretty much the plan simply because it's a "free" base engine/box/loom and ECU set that's sat doing nowt. Also have a Garrett 2256V in the garage that might find it's way on there, but struggling to find a compressor map to see if it's going to be any use, to start off with the plan isn't to get super crazy just aiming for somewhere around 250-300bhp. From what I've read the stock bottom end should be able to handle that with a modicum of reliability, although ideally lowering compression would be worth sorting to "futureproof" the build.

Also weighing up whether a 1.9 crank (believe results in 2044cc) would be a good option as we like torque as well as revs. (and indeed, if we did go for a longer stroke crank, whether the DW10 unit would work since that's also 88mm stroke and we have one to hand. Not sure on journal size though). Another potential to look into is whether an XUD11 crank would even fit since that'd effectively be a 2.2 @ 2137cc.

TBH it'll likely end up with either standard or 88mm crank as they're the easier to procure. Possibly C20LET pistons if some come up at a good price, otherwise standard & will look into the possibility of getting some oil to the underside of them plus either machining the crowns or a thick Cometic MLS gasket (they seem to do them up to 3.5mm compressed). honestly sounds a better option than a decomp plate. Ohh, but then there is someone I could enquire with to see if they have any TE or CTE pistons (heard the latter, from XM/Xantia TCT are said to be weak though?).

Off to look at DW10 crank specs now lol...
Thanks given by:
yes xud cranks fit fine, xud11 needs custom rods as well as pistons.
need a part number? and will sort you out.
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Right following on from this, what actually is the stock compression ratio of the RFV engine? I've heard anything from 8.5:1 to the above 10.4:1

Also am I correct that the factory head gaskets are 1.15mm compressed? Looking at head gaskets & depending on the answers to the above, deciding what thickness to go with.

Assuming I'm correct on the HG thickness and that standard CR is 9.5:1 (which seems to be the most commonly stated ratio when looking up RFV) I'm probably going to go with either a Cometic 3mm HG (giving around 8.2:1 CR) or 2.5mm (approx 8.,5:1) but confrimation of the standard numbers from those in the know would be appreciated since there's a £50-odd difference in the price and they're a special order.

Thanks Smile

EDIT- Also, given the crank interchangeability between engines would I be able to order a generic big end/main bearing set listed for pretty much any XU/XUD shells or??? Also any preferred brands amongst engine builders here, I'm seeing Glyco come up a fair bit but have also seen a company called King who seem to be decent. (given how cheap bearings are in general, and the fact the engine is on 160k I'm planning to refresh it before building on it so new bearings, hopefully bores are in spec to just hone and re-ring)
Thanks given by:
I can confirm without any doubt that the stock XU10j4R / RFV engine has a compression ratio of 10.4:1. The info on is wrong.

Here's a screenshot from the Citroen engine workshop manual (same for all PSA vehicles fitted with RFV tho).


I was only aware that gaskets were available in 2 sizes - 1.2mm & 1.4mm; the latter being a repair gasket following a head skim. Off the top of my head I can't remember how much can be safely taken off the head. Might have to look in to it a bit further.

PM me your email address & I'll send you the workshop manuals (.pdf) and any engine info I have from Servicebox.

Thanks given by: ekjdm14
0.2mm max skim.
need a part number? and will sort you out.
Thanks given by:
Thanks Mighty I'll Pm you in a sec. The gaskets I was looking at are custom made by Cometic, and available up to .140"

Given the higher compression ratio to start with, I'd be looking at the .140" (3.5mm) gasket then as a minimum to bring it down to about 8.5:1 but looking at the cost (when I factor in shipping it'd be a £270+ gasket) think the more sensible option is going to be C20LET pistons or having the originals machined if there's enough in the crown of them to do that.

On the bearing thing, think I've answered my own question reading other folk's builds. Journals the same except XU5 big ends. Have found & snapped up some NOS Mahle VP2 big end shells for £25 which seems pretty decent & probably go with Glyco mains unless I hear different or find any VP2 mains cheap!

Thanks again, appreciate the patience given being a noob to turboing petrol engines!
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