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mostormxu9

Xu9J2 Compression

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mostormxu9

Hello everybody.

 

Does anyone knows how much is the compression of xu9j2 engine?

 

Thanks.

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jackherer

9.3:1

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mostormxu9

9.3:1

I mean compression pressure.

How much psi?

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Anthony

For a compression test? I guess you should see around 175-180 psi for a healthy engine, but compression testers can vary significantly in terms of accuracy!

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dcc

You'd be most concerned over the cylinders showing the same pressures

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mostormxu9

For a compression test? I guess you should see around 175-180 psi for a healthy engine, but compression testers can vary significantly in terms of accuracy!

thanks man.

i want to use xu9j2 head cylinder with xu9 2c internal for turbo conversing.

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mostormxu9

Does anybody knows the xu9j2 camshaft profile?

lift?

duration?

...

 

and as I said i want to use this head by turbo.

Is it necessary to do some modify on it?

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petert

I assume you mean DKZ? Don't quote me, but I think it's 226º @ 0.050" on the inlet, max lift 0.445" and 218º @ 0.050", max lift 0.405" on the exhaust. ie the inlet lobe from the D6B and the exhaust lobe from a DFZ. Thus it has considerably less overlap than a D6B cam which has identical inlet & exhaust lobes.

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B1ack_Mi16

DKZ ain't that the 205 Gentry engine?

 

The XU9J2 I thought was the one used in the 1987 and 1988 405 GRi with 125bhp. Same looking (probably exact same engine?) as BX GTi engine.

 

D6D seem to be the engine code.

6y0qo154.jpg​

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welshpug

that is also what I would presume a j2 to be, downdraft high port long intake high torque engine.

 

dkz is a 9JAZ ?

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petert

No idea then.

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mostormxu9

DKZ ain't that the 205 Gentry engine?

 

The XU9J2 I thought was the one used in the 1987 and 1988 405 GRi with 125bhp. Same looking (probably exact same engine?) as BX GTi engine.

 

D6D seem to be the engine code.

6y0qo154.jpg​

Yes I have this head.

But I bought just the head and intake.

I dont know the exact code.

Is it necessary to port and polish the inlet ports?

I heard that the stock port is a little narrow and if you port it you will get better performance.

How much boost is safe for this head and block?

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B1ack_Mi16

Anyway for compression I suggest you measure the head CC's if you just bought the head and it is not mounted to the block.

And do the same with pistons etc.

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petert

Take the cam out and measure the lift of inlet & exhaust lobes. You'll then be able to make reasonable judgement.

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Thijs_Rallye

dkz is a 9JAZ ?

 

Yes.

 

This head/intake runner combination is from a D6D engine if I'm not mistaken.

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petert

Specs.

post-2864-0-74738000-1503306660_thumb.png

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mostormxu9

Anyway for compression I suggest you measure the head CC's if you just bought the head and it is not mounted to the block.

And do the same with pistons etc.

I will measure it tonight and will tell it.

The pistons cc is 6.

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mostormxu9

The cc of head cylinder is almost 48 ml.

So with piston and the gasket we have almost 55 ml velocity for combustion chamber.

Is it enough and suitable for turbo?

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Thijs_Rallye

compression ratio = (Vstroke + Vcompression)/ Vcompression

 

Don't forget the headgasket volume.

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mostormxu9

compression ratio = (Vstroke + Vcompression)/ Vcompression

 

Don't forget the headgasket volume.

ALMOST 9.2:1

Is it ok?

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Thijs_Rallye

I've never turbo'ed a XU9, so I don't know and above that it is not my decision to take ;).

 

Newer engines run a CR of 10 and above with a turbocharger, but back in the old days they were more around 8 / 8,8 ish.

 

it's up to you, try reading a book like Maximum boost by Corky Bell.

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mostormxu9

Nobody turbo'ed a xu9 here?

Xu10j2te turbocharger is suitable?

How much boost is safe for this CR?

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B1ack_Mi16

I run 9.2:1 on my 2.2 16v T16 engine.

 

But I have a big turbo so don't get boost till 3000-3500rpm ish.

I have max boost of 1.4 bar this far at 6200rpm and haven't seen any knock tendencies yet.

 

However if you add a lot of boost low down in the rev-range I think it might be applicable to knock easier at lower revs.

But you can run a fair bit of boost at 9.2:1 indeed I'm sure you can add 1 bar quite easily with correct fuelling and ignition.

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wicked
Posted (edited)

In the end it's about the dynamic compression; that is a function of static compression, valve timing, boost....

The common way is to trade static compression for boost to keep the same dynamic compression. Modern engines also use the valve timing to keep higher static compression off-boost.

 

One limit for your dynamic compression is that it will start to knock if you go too high. But that level will differ per engine. If you have a lot of back pressure from your manifold/turbo it will knock sooner that a high end manifold with big turbo.

 

The xu10j2te turbo is suitable and has been used before. It's not suited for really high boost/big bhp numbers but it is an easy conversion.

I would just try it.

Note that the turbo technics conversion for the 1.9 had a compression of 1:8.6 so you're not so far off..

Edited by wicked
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mostormxu9

Thanks my friends.

In fact I dont want to give the engine high boost.

The safe range and 24/7 using is more important for me than achieving bhp.(using it all days)

I think about 9 psi almost.

You said an important topic.

Can I use Mi1.9 fuel injector for this boost?(216cc at 3 bar) I can use 3,5 bar regulator also.

Also buying a xu10j2te turbo and exhaust manifold is easiest way for me.

If i can achieve 160 bhp is ideal for me.

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