Xu5 differences

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Fellow Frogger
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Jun 21, 2018
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Vancouver Island, Canada
Hi there, with all this virus stuff going on I find myself trying to learn more stuff about 205's but I'm a bit stuck so though I would ask some questions.

I have a spare si engine and I'm going to freshen it up so I wanted to find out how similar it is to the 1.6 gti engines. The end goal to rebuild it and then add a more aggressive cam, up the CR with a head skim and then add some bike carbs or ITB's but for now doing some reading and learning about things. it would be nice for it to end up with a bit more power than the xu5ja.

What are the differences between the different xu5 short blocks? Mainly the xu5j, xu5ja and the xu5m motor from the si. Do they all share the same pistons, rods and crank?
I'm guessing they might not because they all have different compression ratio's.

Correct me if I'm wrong but from what I have read the xu5j has the small valve head and the xu5ja and the si have a similar bigger valve head but the si has a mellower cam. Is that correct?
Is the cam the only difference between the xu5ja and si heads or do they have other differences such as springs and porting etc?

I know the si has the mono point injection so it's different to the two other engines so ignoring that for now.

Do they have the same exhaust systems?

What other differences are there?

I'm chasing some power for my si and would like it to end up similar (but better) to a 1.6 gti when it's complete so trying to figure out what needs to be done and if it could easily be done with my spare si engine.

Thanks
 
Cranks are the same. Rods are the same. Pistons vary to determine CR. Heads are the same, except for the early GTi which had smaller valves. Exhaust is the same. The biggest differences are the camshaft and inlet manifold. Thus fit a GTi cam (or similar), GTi manifold and aftermarket ECU and you have a nice package.
 
PeterT said:
Cranks are the same. Rods are the same. Pistons vary to determine CR. Heads are the same, except for the early GTi which had smaller valves. Exhaust is the same. The biggest differences are the camshaft and inlet manifold. Thus fit a GTi cam (or similar), GTi manifold and aftermarket ECU and you have a nice package.
Click to expand...

I pulled the pistons out of an XU5 JA the other day and couldn't find any difference at all from the Si pistons. Thinking it must be the head?
The only 1.6 GTi which I thought went OK was the early small valve model, could be other reasons for this though.
 
GRAHAM WALLIS said:
I pulled the pistons out of an XU5 JA the other day and couldn't find any difference at all from the Si pistons. Thinking it must be the head?
The only 1.6 GTi which I thought went OK was the early small valve model, could be other reasons for this though.
Click to expand...

I thought the xu5ja and si have the same head too? how is there CR so different?
 
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