Few Xu10j4rs Questions

[camgti 56]

Hi there,

 

Rebuilding the j4rs. Just completed the head and onto the block.

 

Parts Ive gatherd so far are 45mm Dblias ITBs (need a manifold any thoughts?)+ most bits to rebuild. One thing im stuck on is how high is too high for compression. Im running aftermarket management with individual coils and want to know if 12.2.1 is to high. Im not aiming for a power figure just getting what the budget can afford and making the best for cams and itbs to work. These are wossner pistons and are apparently the next step from the stock 10.8.1. Ill also order them in 87mm. Ive also been looking at this 4903110 (282Deg Inlet 274exh) from catcams and will change retainers and springs to suit. This also apparently means ill need to ditch the oil spray bars from the head (cams) for the cams to fit. (will the actual head need machining?)

 

Im using the car daily and will take it to the track

 

Any help will be great.

 

Regards Cam

Edited August 26, 2009 by camgti

[James_R 3]

I'd havea search there's been plenty of engine's built using these cams now.

 

16v205 has a build thread on his and outputs too.

 

Yes the spray bar needs blocking off and removing for those cams, and the head needs "clearance" adding for some of the cam lobes.

[camgti 56]

Thanks James.

Ive read the build again, now understand a bit more. I would have thought it would make more power. Im not to keen on using 12.2.1 pistons, these seem to be the only ones up from the standard 10.8.1. Anyone shed some light? If i do end up having to get some made ill got bascially the same route as 16v205

 

Cam

[James_R 3]

190ft/lbs not enough? it made 240 or something, but not as much torques.

 

Findinf pistons to suit is a big pain. Could ask for the job number and have copies made??

[brumster 135 1 Cars]

Thanks James.

Ive read the build again, now understand a bit more. I would have thought it would make more power. Im not to keen on using 12.2.1 pistons, these seem to be the only ones up from the standard 10.8.1. Anyone shed some light? If i do end up having to get some made ill got bascially the same route as 16v205

 

Cam

 

Well, I know Longman were not in favour of such a high compression ratio with my engine and also others - they did not build mine to a target CR this high, nor another reputable and very well performing lump - so clearly they don't feel it is absolutely necessary for big numbers. That's not to say there is a problem with doing it, of course, I'm just telling you what I know.

 

You can get custom made pistons from Wossner to pretty much any spec you like; you'll just end up waiting a considerable time for them (last time I checked, anyway). I think many people just have the off-the-shelf pistons machined a little to bring down the CR.

[welshpug 1,661]

depends how wild you go with the cams it seems, 2 kinds of compression ratio, static and dynamic.

 

if the cams are too wild with a normal compression they'll just blow the fuel straight out of the exhaust at lower revs and not make the power higher up.

 

you'd need to speak to an engine builder maybe and discuss your camshaft choices to see if that's too much or just enough.

Edited August 28, 2009 by welshpug

[James_R 3]

From a few sources now I've heard to not go past 12.0:1 even on truely mental cam specs as pump fuel is getting worse in terms of quality, a mapper I spoke to said a few engines have had to have the CR taken back as they couldn't get the ign right on them. 11.5:1 is a nice number Also worth remembering if the engine has a good VE then the compression is going lower as the dynamic will be higher (if that makes sense)

[camgti 56]

Yea 12.2.1 is very high. I ill ask for the job number and try and get copies. Im just not keen on the apparent 14week waiting period. Its hard talking to engine builders over here. They dont really know what a peugeot is or what a 4cyclinder car is. Or if it has not turbo and comes from japan. Im building this in my room in an apartment is sydney which proving fun, got not space but have been on this site percrastinating for ages.

 

Has anyone tried getting the valve cutouts machined and the block decked (also the sides of the piston) to bring the cr up? (if that makes sense)

 

Cam

[James_R 3]

The crowns are wayyyyy to small, other option is to get some std s16 pistons (Petert does them) in an over bore, and deck the block 1mm on a 86mm bore you'll see the CR you want

 

Also means you can use s16 rods and then it's floating gudgeon's etc....

[petert 588]

Has anyone tried getting the valve cutouts machined and the block decked (also the sides of the piston) to bring the cr up? (if that makes sense)

 

There's a guy in Toongabbie who's very good.

[camgti 56]

Yea i know of him too peter. Hes excellent at what he does. Im thinking of having the motor in the car an running in the next 4 weeks though, otherwise i would call him. Im sure hes very busy as we all are so may not have the time right away, if you get my drift.

 

Cam

[camgti 56]

So if someone can help me with some calculations.

 

I want to order these 12.2.1 pistons in 88mm, use and 88mm crank and have the piston machined enough to bring the compression to 11.5.1. Ive been doing some research but cant seem to get my head around it in regards to chamber volume squish height etc. Bascially need to know how much to trim off the raised section.

 

Cam

[B1ack_Mi16 67]

So if someone can help me with some calculations.

 

I want to order these 12.2.1 pistons in 88mm, use and 88mm crank and have the piston machined enough to bring the compression to 11.5.1. Ive been doing some research but cant seem to get my head around it in regards to chamber volume squish height etc. Bascially need to know how much to trim off the raised section.

 

Cam

 

If you are building a 88mm bore engine, you can get the head chambers increased to about 44cc like I did on my 2.3 litre engine.

 

It will help lowering the comp a little bit... and maybe you don't need to do anything to the pistons at all?

 

Mine is 11.6:1 with 1mm squish distance.

[DrSarty 90 1 Cars]

If you are building a 88mm bore engine, you can get the head chambers increased to about 44cc like I did on my 2.3 litre engine.

 

It will help lowering the comp a little bit... and maybe you don't need to do anything to the pistons at all?

 

Mine is 11.6:1 with 1mm squish distance.

 

Slightly OT but...

 

We had a big discussion concerning my 2.2 about safe over-bore resizes. I was advised to go at a push to 87.5mm but I settled on 87mm.

 

Are we saying now after you've run yours for a while (BlackMi) that 88mm is 'safe'?

 

If it is we could see a lot more higher displacement engines around the 2.3-2.4litre mark. And if someone's really brave and uses that 96mm crank that someone in Denmark suggested IIRC then some lumps nearer 2.5litre!!

 

One thing I can say is that with the right cam, 11.6:1 on upped displacement produces a very smooth driver.

 

This is a nice project.

 

P.S. My Wiseco pistons had the gudgeon pin heights tailored to suit the pistons being 'block flush'. IIRC BlackMi also offset ground his crank.

Edited September 3, 2009 by DrSarty

[B1ack_Mi16 67]

I saw a danish company selling 2.5 litre conversions.

 

I think they use a 102 or 103mm strok crank, custom billet one from Farndon engineering or maybe someone else is making them.

 

This and a 88mm bore will give like a true 2.5 litre.

 

A 88mm bore and 96mm crank will not give anything near 2.5 litres.

It actually gives 2334cc so nothing near a 2.4 eiter.

 

Maybe a 89mm bore can work on some blocks.

Wish I had the cash to try...