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Author Subject: XU10J4RS stock valve spring rpm rating
cristodog

Newbie

Location: Vantaa

Registered: 24 May 2020

Posts: 3

Status: Offline
Post #1
Hi

I rebuilt a XU10J4RS engine with stock parts exept for forged pistons, Kent PT81 cams, and custom fitted
42mm Honda ITB's with 41mm intake runners, running on E85 only

I had the rpm limited to 7000rpm and managed 123.9KW (118.8KW corrected value) at the hubs.

I have stock valve springs that have done 150000Km and was wondering if anybody knew what rpm the
stock springs are good for.

Kentcams does not suggest uprated valve springs with the PT81's but im planning on raising the rpm above 7000 because
the power was still climbing when it hit 7000rpm and I would like to see what I can gain with adjusting the cam timing and raising the rpm limit a bit

So if anyone knows what rpm the stock valve components are good for Id be grateful for your replies.

First time tuning the Xu series engines and I didn't take a baseline from the donor car so I really have nothing to compare these results to.

Id like to hear what kind of setups you have and what kind of power figures you have achieved


Posted 24th May 2020 at 12:54
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prism7guy

Seasoned Pro

Location: DoncastAAAAARGH

Registered: 13 Jan 2008

Posts: 4,637

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Post #2
I think some of the lynx supercharged boys have their limiters set to 7,500rpm. I was under the impression that it's the hydraulic lifters that don't like higher rpm's.

My car makes 200whp with 6-8psi of boost and the limiter set to 7,250rpm, standard cams timed up as per the faq guide on here. I could probably make more if i tweaked the timing a bit but i've not got round to that yet.

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Posted 24th May 2020 at 13:24
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welshpug!

Capt Pedantic

Location: Bigend, Wales.

Registered: 27 Mar 2007

Posts: 25,817

Status: Offline
Post #3
stock rpm for oem ecu on early cars is 7450.

peak power was 6500 though, if your power is peaking that high then I'd want to check cam timing, However pt81 is very marginal on valve to piston clearance.

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Posted 24th May 2020 at 17:57
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pete_rallye

Seasoned Pro

Location: Yorkshire

Registered: 12 Dec 2002

Posts: 5,253

Status: Offline
Post #4
Richs supercharged car used to rev to 8500rpm on stock springs and lifters, it didn't blow up by I wouldn't like to recommend those sorts of revs.

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Posted 24th May 2020 at 18:41
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welshpug!

Capt Pedantic

Location: Bigend, Wales.

Registered: 27 Mar 2007

Posts: 25,817

Status: Offline
Post #5
most certainly not lol.

hudraulic tappets on this engine dont like regular trips beyond 7800, my engine is set to 7700 though I'm not sure where peak is as they were the wildest hydraulic cam profile i could find

(no chance of working with standard piston and springs though)

________________________________________

need a part number? get on here - http://public.servicebox.peugeot.com

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Posted 24th May 2020 at 21:56
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cristodog

Newbie

Location: Vantaa

Registered: 24 May 2020

Posts: 3

Status: Offline
Post #6
Thanks for your replies!

The idea first was to just rebuild the engine with just the pt81's but then it started getting a bit interesting with the non existent valve to piston clearance so I had to get wössner forged pistons, I had to remove some aluminium from the follower cutouts just to get the Cams to rotate, so wilder cams would probably need further machining of the edges of the holes If they have more lift than the 81's.

Im happy with the current setup I have, just going to renew The valve springs with new stock ones before even thinking about raising the rpm limit

I think you are right about the powerband for these cams for I have them dialed in to manufacturer spec and had some ignition issues on The dyno due to the spark plug gap being too big, so I ran out of time to get very top end optimized, so I got Peak Power at 6450rpm after wich the ignition issues started after many hours of tuning so I was unsure of If There was more to gain higher up



Posted 25th May 2020 at 07:34
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welshpug!

Capt Pedantic

Location: Bigend, Wales.

Registered: 27 Mar 2007

Posts: 25,817

Status: Offline
Post #7
I have newman PH4 and didnt have to remove any material, just modify the oil spray bars and use different springs, if you had to do clearancing for your cams I suspect they are not pt81!

did you check the compression ratio with those pistons? last set I know of anyone using and documenting ended up with 14-1 compression Shock definitely not a piston I would use out of choice, might be ok on E85 LOL

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need a part number? get on here - http://public.servicebox.peugeot.com

Bring on the Trumpets.

Posted 25th May 2020 at 11:03
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cristodog

Newbie

Location: Vantaa

Registered: 24 May 2020

Posts: 3

Status: Offline
Post #8
welshpug! wrote:
I have newman PH4 and didnt have to remove any material, just modify the oil spray bars and use different springs, if you had to do clearancing for your cams I suspect they are not pt81!

did you check the compression ratio with those pistons? last set I know of anyone using and documenting ended up with 14-1 compression Shock definitely not a piston I would use out of choice, might be ok on E85 LOL


[img]https://1.bp.blogspot.com/-i1WYVMOsKtI/W-24B--
sIfI/AAAAAAAAAIw/olxBNXF0R6kzeVYRK-oUrLtYzPrnfq_uACLcBGAs/s1600/IMG_20181112_095819.jpg[/img]


Thats odd, the engine is from a 2002 phase 2 Xsara vts, it has AS7 marked on The cylinder head, I linked a pic of the camshaft fitment problem I had, it was stopping on The follower hole edges

I remember The Max lift being 11mm when I had help degreing The cam according to The pt81 specsheet online

I checked the spec sheet for the ph4's and the Max lift was a little over 11mm, so If you had no problems with the fitment then I don't know whats happening here Big grin

I measured the static compression ratio to be 12.5:1
Posted 26th May 2020 at 16:47
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welshpug!

Capt Pedantic

Location: Bigend, Wales.

Registered: 27 Mar 2007

Posts: 25,817

Status: Offline
Post #9
pt81 is well uneer 11mm, standard vavle springs go coilboind at 10.8 or 10.9mm iirc.

________________________________________

need a part number? get on here - http://public.servicebox.peugeot.com

Bring on the Trumpets.

Posted 26th May 2020 at 20:27
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welshpug!

Capt Pedantic

Location: Bigend, Wales.

Registered: 27 Mar 2007

Posts: 25,817

Status: Offline
Post #10
actually it seems they are 10.94mm, so I would not run them on a standard spring or piston, therefore if you uprate the springs, as you already have 12.5-1 I would go for a ph4 or similar.

________________________________________

need a part number? get on here - http://public.servicebox.peugeot.com

Bring on the Trumpets.

Posted 26th May 2020 at 20:33
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