XU9 engine musings

schlitzaugen

schlitzaugen

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I have a DFZ in my car which is really nice and pulls like a train.

I have a DKZ (Si car) in my spares car. Is there any point swapping the two? Apart form the academic task of finding the actual shape of the Si engine (never seen it run).

I have read on the Puma racing site that Si engines are more likely to be within specs than the GTI, is this true of Aus cars as well?

And lastly, how hard is it to swap the DFZ dizzy to the DKZ engine? I suppose there's no other mod necessary?
 
schlitzaugen said:
I have a DFZ in my car which is really nice and pulls like a train.

I have a DKZ (Si car) in my spares car. Is there any point swapping the two? Apart form the academic task of finding the actual shape of the Si engine (never seen it run).

I have read on the Puma racing site that Si engines are more likely to be within specs than the GTI, is this true of Aus cars as well?

And lastly, how hard is it to swap the DFZ dizzy to the DKZ engine? I suppose there's no other mod necessary?
Click to expand...

Si is an Australian model, how would Puma know anything about it?
Si engines aren't DKZ they are BDY, BDY is 1600cc monopoint and DKZ is 1900 multipoint.
Yes a DKZ will bolt into an Si and has the same head but that doesn't mean it is the same engine.
Graham
 
are you wanting to replace the jetronic with the motronic si unit?

AFAIK there isn't a way to hook up the si motronic to a multi point system and it would be a downgrade to go single point injection.
 
An Si motor has a much more restrictive induction to. A GTI inlet manifold would be the way to go on a Si motor.

If not, stay with the DFZ. My DFZ pulled awesome until I stopped driving it (lousy headgasket)



Chris
 
spar said:
are you wanting to replace the jetronic with the motronic si unit?

AFAIK there isn't a way to hook up the si motronic to a multi point system and it would be a downgrade to go single point injection.
Click to expand...

Si has Marelli management.
Why put in a 1600 instead of the 1900, so no,
Graham
 
No, I would keep the engine management and intake/exhaust.

Just to see if the Si engine has survived better (it seems in pretty good nick) than the GTI. Both are unknown quantities, so no real difference, I guess.
 
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schlitzaugen said:
No, I would keep the engine management and intake/exhaust.

Just to see if the Si engine has survived better (it seems in pretty good nick) than the GTI. Both are unknown quantities, so no real difference, I guess.
Click to expand...

So why can't you start up the Si engine in its own body and then do a compression test?
Sounds like you need something to keep you busy.
Graham
 
That's true.

I can't start it up because I destroyed the wiring to re-wire the GTI so the ECU is no longer connected to the engine amongst other things (and a lot of the wires have been taken away), but I can still do a compression test. As you know though this is not the entire story of an engine.

And come to speak of it, is there any recommended way to store an engine so valves don't rust, seals don't dry up (water pump) etc.?

I was just wondering if there is any chance this Si engine is even better than the GTI engine I am using right now, given that is a newer car (possibly lower mileage) and looks like it has very well taken care of.
 
This is a most confusing thread.

Do you have a DKZ in an Si shell, fed by Si management, induction etc.?
 
My mistake, I thought it was a DKZ.

No, I have an Si car with its original engine (a BDY as you said, I checked). Everything stock.

Look, I have two cars.

A GTI with a replacement DFZ engine (bought S/H off someone here).

An Si with everything original, spares car, BDY engine. Car bought as a write off (crashed LH front), but in very good shape otherwise and looks very well maintained.

The GTI is my daily driver, but it got there thanks to all the bits I cannibalised off the Si. I did reuse some of the wiring off the Si, but I have used it to rebuild the GTI loom, not just swap over the wiring form one car to the other.

I think you are confused because you think I swapped over loom and parts. That is not possible as you know. What I did was replace individual wires (tried to keep the numbers correct) because the GTi loom was frayed and cracked and messed up generally speaking. It was a nightmare, but I did it in the end (took me three months), so now I have a nice new loom made up by wires borrowed from the Si (literally pulled out of the connectors and replaced in the correct connectors on the GTI, keeping the wire numbers), wires I made up myself to replace what I could not find in the Si loom, and some wires I added from scratch because I did not find originals on either car (sunroof wires).

The ECU wiring loom on the GTI was not changed, apart from replacing the injector wires with silicone insulated oxygen free wires and new Bosch connectors.

Wires from the Si ECU loom were "borrowed" to replace similar wires elsewhere in the GTI loom, because they have the right (narrow) spade terminals you can not buy.

Clear as mud?
 
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Why don't you go back and edit the first post then? Change DKZ to BDY.

If you want to make the most of what parts you have, put the BDY head on the DFZ block, with the DFZ cam.
 
if you do the head swap you might as well put a cam in too and really power up.
 
PeterT said:
Why don't you go back and edit the first post then? Change DKZ to BDY.

If you want to make the most of what parts you have, put the BDY head on the DFZ block, with the DFZ cam.
Click to expand...

Thank you Peter, that is in the wings, but I already have a DFZ head which I understand can be machined down to mimick a BDY head, and I actually have a DKZ head (which I understand is identical) as well, so it's not really necessary to pull apart what could be a perfectly good engine.
 
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schlitzaugen said:
T but I already have a DFZ head which I understand can be machined down to mimick a BDY head, .
Click to expand...

not sure where you got that from. The DFZ head is a bit of an orphan. It has Ø39/33mm valves 105mm long, compared to Ø41.5/34.5mm 108 long in the BDY/DKZ/D6B head. Whilst it is possible to skim a massive 2mm off the head to reduce the chamber volume, you only create more challenges by retarding the cam timing.
 
PeterT said:
not sure where you got that from. The DFZ head is a bit of an orphan. It has Ø39/33mm valves 105mm long, compared to Ø41.5/34.5mm 108 long in the BDY/DKZ/D6B head. Whilst it is possible to skim a massive 2mm off the head to reduce the chamber volume, you only create more challenges by retarding the cam timing.
Click to expand...

Sorry, I forgot the valves are smaller, you're right.

And the reason I bought the DKZ head was the timing issue.

Anyway, I still have the DKZ head and a DFZ cam, so there's no real need to pull apart the BDY engine (not that I have something against it).

That means I need to buy some valves then. Can these still be bought new?

What about the pistons, I understand the DKZ pistons are different to the DFZ too? Can I buy these new?
 
Why do you need valves? Is the DKZ bare? I'd just use the BDY head if that was the case. Do you have a DKZ cam? They're more desirable than a DFZ cam.

Why do you want DKZ pistons? You have a working DFZ and another set of identical pistons in the BDY. The DKZ piston has a 15cc dish compared to just 9cc in the DFZ/BDY.
 
PeterT said:
Why do you need valves? Is the DKZ bare? I'd just use the BDY head if that was the case. Do you have a DKZ cam? They're more desirable than a DFZ cam.

Why do you want DKZ pistons? You have a working DFZ and another set of identical pistons in the BDY. The DKZ piston has a 15cc dish compared to just 9cc in the DFZ/BDY.
Click to expand...

Yes, the DKZ head is bare, no cam, no valves.

Nope, no DKZ cam.

Am not sure if the DFZ pistons are reusable (most likely/hopefully they are). I assumed the higher compression of DKZ engines came from a higher deck/smaller dish or a combination of both.
 
you said your dfz engine is still strong, so why replace the pistons? you will get more compression with dfz pistons than the dkz items. the pistons going into my new motor aren't new ones. as long as your dfz items are in good nick you'd have to have rocks in your head to go out and buy new ones.


Chris
 
It's more likely to have liner wear than piston wear. As you have a second set of pistons/liners in the other car you're sorted anyway.

The DFZ has an 11mm deep chamber, 49cc. The other type of head has a shallower 8mm deep chamber, 34cc. Thus the difference in valve lengths.

You can see that 34cc + 9cc is better than any other combination for compression.

It may even be that the D6B piston is 15cc and the DKZ is 16cc.
 
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