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In one word, no, the Si (BDY) has 65 kw and 128 nm of torque the DFZ 75 kw and 143 nm of torque.
The DKZ has 90kw and 151? nm of torque.
Didn't you say the DFZ was going great?
Graham
XU9 engine musings
- Thread starter schlitzaugen
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In one word, no, the Si (BDY) has 65 kw and 128 nm of torque the DFZ 75 kw and 143 nm of torque.
The DKZ has 90kw and 151? nm of torque.
Didn't you say the DFZ was going great?
Graham
Yes, Graham, but that comes without any term of comparison. I have never driven one fo these cars new. That is why for me the DFZ is going great, but who knows how much better it could go with a rebuild or even a spec up to DKZ. Which is where the BDY comes in. What if the DFZ has lost some of its power, enough to bring it down below what the BDY may have lost itself? that is the question I would like to explore.
But it's not really a plan. The BDY engine can always be a stand-in while the DFZ gets rebuilt if it turns out that is the best way to go.
My main aim is to end up with the best engine I can without any serious mods. If I had a DKZ engine, I would use that. I have apparently enough parts that with a minimum expenditure I can build an engine at DKZ specs. All I need right now apparently is the valves and a DKZ cam. I did not mention, but I have a good GTI crank, the pistons, sleeves and conrods I saved from the original DFZ engine and hopefully will be able to reuse some of that stuff. I would only get new pistons to make sure I don't have any problems. Sleeves look very good to me, but I will measure them of course, and if need be I will replace.
But it's not really a plan. The BDY engine can always be a stand-in while the DFZ gets rebuilt if it turns out that is the best way to go.
My main aim is to end up with the best engine I can without any serious mods. If I had a DKZ engine, I would use that. I have apparently enough parts that with a minimum expenditure I can build an engine at DKZ specs. All I need right now apparently is the valves and a DKZ cam. I did not mention, but I have a good GTI crank, the pistons, sleeves and conrods I saved from the original DFZ engine and hopefully will be able to reuse some of that stuff. I would only get new pistons to make sure I don't have any problems. Sleeves look very good to me, but I will measure them of course, and if need be I will replace.
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You have the right valves in your BDY engine but you would need a set of DKZ pistons to build a DKZ spec engine.
And there you have it.
This is why I am so confused. Do I need the DKZ pistons or not? Or better put, using the DFZ pistons apparently gives the highest compression so why would I need the DKZ pistons then?
I will probably have to do more digging on my own.
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If you want 11 to 1 compression then go and use the BDY/DFZ pistons, I tried it and it was a disaster, the resulting 225 lbs of compression just too much, better keeping the compression down and being able to use some worthwhile ignition advance. This was the advice of Ian Shugg of Crankshaft Rebuilders, been building racing motors for over 50 years, I didn't take it and paid the price.
Graham
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It was a pretty wild cam for lift ,480 thou but yes, maybe some more discussion with Clive would have been a good idea. In any case if you want DKZ spec this means standard cam and compression.
Graham
The important thing with 8V's is to spend money wisely. You can spend a lot of money for very little return. Don't get hung up on the differences between DFZ, DKZ, D6B etc. If what you have is in good order, just freshen it up by doing the following:
- compression test to determine condition of bottom end
then
- skim head 1mm
- 3 angle seat cut and blend ports
- Cometic head gasket #C4225-027, (0.68mm thick)
- regrind cam to something slightly warmer (around 225º @ 0.050"), but most importantly, have them advance the grind 2º (4º crank) to make up for thinner head gasket and skim.
This will result in around 9.8:1 CR and give you a nice, crisp, responsive engine that pulls like a train. It will still work with the standard ECU & ignition and get excellent fuel economy.
- compression test to determine condition of bottom end
then
- skim head 1mm
- 3 angle seat cut and blend ports
- Cometic head gasket #C4225-027, (0.68mm thick)
- regrind cam to something slightly warmer (around 225º @ 0.050"), but most importantly, have them advance the grind 2º (4º crank) to make up for thinner head gasket and skim.
This will result in around 9.8:1 CR and give you a nice, crisp, responsive engine that pulls like a train. It will still work with the standard ECU & ignition and get excellent fuel economy.
Thank you very much, Peter.
I guess this is the kind of advice I am seeking.
Questions:
When you mention skim, do you refer to the DKZ head?
About cam regrind, do you refer to the DFZ cam?
I guess I could use a vernier cam pulley to compensate for the head skim instead of trusting the cam grind. This is because I don't know anyone around here who would be able to do a decent cam grind (people here usually send cams over east and I don't know anyone there either).
I take it the 9.8:1 compression you talk about above is achieved with DFZ pistons?
Just use all DFZ parts. As Graham said, if you put the DKZ/BDY head on the DFZ pistons you'll end up with over 10.5:1 and need after market ECU to control the ignition. If you want to retain the std injection/ignition, keep it under 10:1.
You could use an aftermarket vernier pulley, or a GTi6 pulley which has been reduced in thickness.
You could use an aftermarket vernier pulley, or a GTi6 pulley which has been reduced in thickness.
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The DFZ head has smaller valves so DKZ pistons could be useful to go with the BDY DKZ head. Don't forget too that the DFZ only has 8.3 to 1 compression in standard form.
I reckon just go an buy a DKZ from a late series 1 405 and then follow Peter's advice.
Graham
Graham you've missed my point(s) again. The difference in valve size is insignificant. Once the seats are cut correctly and blended they all flow around the same. He doesn't have DKZ pistons, nor a DKZ cam. My point was to use what he had, minimizing costs. Yes, the DFZ is only 8.4:1, thus the 1mm skim and 0.68mm gasket, for a total reduction of 1.7mm. This gives 9.8:1. As I said, don't get hung up on the differences, or you'll start spending money unnecessarily.
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OK, no problems, I took the advice as general not specific to the DFZ and in doing so added to the confusion in this thread!
Things should now be clear for the time being at least!
Graham
That is indeed what I can do with a minimum of spend. Thank you, Peter.
As a side question, why are these engines so low compression? I have an R17G which has 10.5:1 and doesn't suffer, with a primitive old K-jetronic.
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So they will run on 91 unleaded, don't forget this was all that was available in 1986, 95 octane came later and enabled (along with more advanced Motronic management) the DKZ engine to be sold in Australia.
Graham
Hmmm.
You're right, I didn't think of that. I run mine on 98 anyway (just as I run the 17G).
So that means I could potentially go higher in compression and keep running 98?
You're right, I didn't think of that. I run mine on 98 anyway (just as I run the 17G).
So that means I could potentially go higher in compression and keep running 98?
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I've read through my notes and 1.7mm equates to 10:1. I've done this upgrade many times to DFZ's. Not with the thinner gasket, but by taking a 1.7mm skim. I always left 0.3mm for future skims. The thinner Cometic gasket has only recently become available. I used a reground cam with 238º duration @ 0.050", 289º advertised. Owen Wuillemin would modify the original 8V pulley by offsetting the pin 2º. This put the cam in exactly the right position every time. I've since changed the grind to 237º @ 0.050", 286º advertised. It doesn't sound like much of a change, but the lesser advertised allows for slightly less compression ratio. What I should do is get a new master made with approx. 230º @ 0.050", 275º advertised, which would work better with 9.5:1 setups.
Even at 10:1, the advance curve was marginal. The problem is you get pinging in the 2000-3000 range as the advance comes in too early. You still need 30º at full load, but 12º static would be ideal rather than 10º. So it means either fitting stiffer springs in the dizzy or a fully programmable after market ECU. 98 octane is mandatory. With an aftermarket ECU this combo makes a reliable 80kW at the wheels (approx. 145hp flywheel, same as DFW Mi16). You can definitely tell it has a different cam however, thus I suggested approx. 225º, which is similar to the DKZ and D6B cams.
There you go. All my DFZ secrets gone.....
Even at 10:1, the advance curve was marginal. The problem is you get pinging in the 2000-3000 range as the advance comes in too early. You still need 30º at full load, but 12º static would be ideal rather than 10º. So it means either fitting stiffer springs in the dizzy or a fully programmable after market ECU. 98 octane is mandatory. With an aftermarket ECU this combo makes a reliable 80kW at the wheels (approx. 145hp flywheel, same as DFW Mi16). You can definitely tell it has a different cam however, thus I suggested approx. 225º, which is similar to the DKZ and D6B cams.
There you go. All my DFZ secrets gone.....
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