Building m-TDI 1z; 1z pistons vs. ALH, AHU, etc.

Building m-TDI 1z; Machined pistons back...PICS

Well...breaking it down and am ready to go. I'm building a 1z block back up and was going to send in the stock pistons (1z) to swaintech for a top and side coating to help with heat dissapation through the piston, as well..hopefully taking that "care step" in keeping their strength under high boost/more fuel. The plan. I'll be using a plenum style intake manifold I've been working on as well as a DI specific modified mechanical injection pump with a 12mm head. Might end up at 11mm if I don't like it. Haven't concreted my decision on the nozzles yet, but it'll be something larger to support all that fuel. My question...or rather concern in doing some digging into the forums regarding pistons.
What are the inherent weaknesses in the 1z pistons? Will my steps with SwainTech help as a safety against failure? I'd hate to be running 20+psi of boost on this nicely rebuilt motor only to toast a piston. The coating will go a long way but I'm interested in the piston design itself between the 1z and ALH/later models. Are they made stronger? If someone could help it would be great. I was going to send them in this week but am going to do some more digging and see what you guys have to say.

Joe

Joe you dont want to use the 1z pistons if your going to spend money on coating them. The design are very similar if not identical (im not sure) as the rest of the tdi's but If I was you get hold of some AFN or any A4 tdi pistons as they are stronger. Des has been through the 1z pistons a few times and uses the afn/a4 pistons now.

LOL. Thats what I was afraid of... Maybe I'll be able to find another for this ALH set i'm getting ahold of . I'd like to know the design differences between the two though. What makes one stronger than the other. If I had one in hand I'd be able to tell I'm sure but I don't as of yet. The set I can get would be a pretty good deal, but then...i'd have to find one more to make the set complete...
Also...anyone know if the 1z and the later motors share the same OEM rings? Or did they switch rings when they went to the updated pistons as well?

Joe

Joe,
The later model 98 jetta thru 2002-03 tdi pistons in the usa ..have brass trunions for the piston pins supports, and the ring lands are beefier. I forgot but either the older all cast aluminum tdi pistons like in 96-97 passat (like yours) the ring land is lower..the new ones the ring land is raised up to help emissions....any how the later tdi pistons ...98 was first year with em here..are beefy!!! you can clearly see a big 'ol difference when you look at em side by side. I have to see, if I still have a old set laying around. I definately have new sets most of em have a scored piston or two..or valves in the though ha.. Simon Cooper has pic of the bigger transporter pistons, He used to use, on his website...they are the same construction as the ones I'm talking about. ie brass trunions, bigger ring lands, reinforced etc...
Come on tell em the truth you'll be running 30-40 psi on your little hotrod... 20 psi is for stocker 1.6Ls..ha
Later
Deo
\x/ Hillfolk!

OK...truth had it. 25-30 will be the initial run on this motor. I am building it strong, thus the asking of questions regarding the integrity of the pistons. Now what i wonder is if the piston rings are the same between the two types of pistons. I just got new rings for the 1z pistons for a killer price compared to what the dealer wants. Now...might have to get "others" again. I see Vanamania on ebay sells the "newer" style pistons for 500 a set with rings. Might be an option if I can sell off the rings i have and the 1z pistons. Anyone know the story on the rings though because I do have access to buy a set of 3 good ALH pistons and would just have to find one more. Deo...if you had 1 or 2 good pistons laying around of the newer design I'd be interested in the one. Let me know.

Now...about the rings...

Joe

Joe if your doing what you say you are i'd do what simon did/has done with his 1Z motor and which is now mine , yes use the 2.0L pistons but then you will have to have some shortened rods and while your at it have them hardened then you'll need to do a bore for the pistons as well.

Turbobuilder does the cams when he has time i've heard and head job race ware bolts job done , should be good for 40psi at around 17.3.1.

Hmm... I had consider the van pistons...but the price and avaiablity is an issue for me. I think I'm going to try and locate a good set of ALH pistons and go that route. I'd love to toy with that in the future though. Block rebore...shortened rods, man...i bet that motor rocks. By the way...how'd you end up with it and what is he running now?

Joe

He's running the 2.0L 16v pd motor and aiming for over 300hp with a holset hx35 turbo , head job and larger nozzles.

This is the reason i've ended up with this motor but its not running at the mo , and it will be the first time its been ran with a ecu/electronic pump setup.

I have some pictures somewhere of Simon's engine but i have to find my printer/scanner software disc first to post , looks very impresive.

WOW...now that is impressive Intially with this motor like i said...i think my target peak boost will be at MAX 30 psi...more than likely i'll run around a healthy 25psi. Should be plenty with this motor in an MK1 chassis. However, in the future, i may be inspired

Joe

Joe you will need to run at least headstuds with that much boost on a 1Z. They dont handle boost as well as A4 blocks.

I always do head studs on my motors... and Raceware is the only way to go. I may also be doing main studs as well as rod bolts if i'm inclined to go away from stock...but needless to say...the racewares are already here.

Joe

I've tried high boost in a 1z , after a few head gaskets I backed off my boost levels . Studs would help the head gasket failures but watch out for too much stress on the rods in you go with studs .

only problem is the van pistons were about $1000 bucks..last i priced them..if they are cheaper it would be ok..
later
Deo

i agree with Deo on that one. It'd be great if on this side of the pond we could easily access the van pistons...but for the price. Man, i'd go and by a PD to swap in rather than going with the van pistons. Would be nice though if they were more friendly on the pocket book.

As far as studs, head gasket failures, etc. I probably will lower compression slightly on the motor. And boost...boost will be relative to what the Rabbit will like, etc. In other words...an insane amount is useless if I can't put it to the ground. I'll find my medium. I like the idea of 25 psi where I was before Comfortable. and fast...


Joe

I've ran 24/25psi in the engine i had b4 but not for long periods of course and it held together and no studs but it may well have in time , and a large fmic helps big time here.
If when it comes to mapping my setup its under fueled which it could be i will probably use a methanol/water injection into the intake and i now someone who has/can map it in viera the ecu , a programme which allows for any other fuel which has been added by other means........around the 20+% region and an N20 map.

Large FMIC would be nice.... but here is my solution...


Probably overkill...but i won't complain about more cold charged intake air. Friend and I built it for a Lysholm 16v project i was working on but the 'rado got sent to the wind in exchange for my bus last year...so this found its way to the Rabbit and the TDI...

As for the 1z pistons...i have sourced 3 good AHU pistons, still looking for another. But I'm interested in knowing "where" the 1z pistons have failed in the past. If they are stress cracks, etc. thermal coating and the fact that it greatly decreases the amount of heat transferred into the piston would probably null and void this problem. Where specifically have they failed?

Joe

They broke in half. From crank wee end to wee end. I thermal coated mine to. Still failed. You need the later pistons. I did post pictuers a few year ago.

thanks, and that helps alot! I've got three on the way...now if I could just find another one to make a set! No sense in wasting money on something thats going to break...
Des...are the rods between the pistons the same or different? From what I have seen, i don't see any differences between them. In reading...haven't found much...

Joe

Rods are interchangeable in a3 1z and afn engines. The pd 130-160 rods and pistons are WAY stronger and better than even the late a4 pistons etc. BUT the big end dia is larger in the 130+ engines so you need the crank too. The 130+ piston wont fit a stock rod....

Interesting...all things to consider for a future rebuild, etc.
The PD crank/rods and pistons combination sounds very cool. A thought though... because of the location of the injectors on the PD engines...wouldn't this make them incompatible with a pre PD TDI motor?

RabbitGTDJoe said:

The PD crank/rods and pistons combination sounds very cool. A thought though... because of the location of the injectors on the PD engines...wouldn't this make them incompatible with a pre PD TDI motor?

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No, they will work fine.

thats good to know for the future. Thanks Kerma! Oh, and decided i'll be buying new nozzles vs. used....just too many factors to worry about ...

Joe

As far as I know you will have to run the block of a pd130+ as the crank wont work with the normal ve block....is this correct des?

Updates, Updates...
First of All... Mikeyworks, thanks for the ALH piston... no 1z units here. Found the 4th from Vic a Vanamania and all have worked out nicely...

For anyone following the thread.... alot of progress came today when I got my pistons back from the machine shop... should start a new "m-TDI" Rabbit thread...but oh well.

Before machining...

After machining to bring down the CR slightly to allow for more fuel/boost as well as elminate hot spots associated with the lip... Kerma did this previously. I had mine done on a CNC lathe and they did one hell of a job on them.



CR should now be around 17.5:1 after ceramic coating which I hope they will go in for through SwainTech next week.
Going to CC the pistons and also see where I am at prior to ceramic and after though its easily figurable, I'd like to run through it again. If anyone has the CC rating for a stock ALH piston bowl to the top of the lip, that'd be awesome...otherwise, looks like i'm going to be doing some digging in the archives as I had a computer crash recently and the CC information that I had recorded for the stock pistons was lost

Also, using the cummins pump on my application and needed to find a solution to the injection pump pulley since the nose on the cummins pump is shorter than a TDI unit. I liked the stoutness of the MK4 style TDI injection pump sprocket and the fact that it is "adjustable" for timing without loosing the pump...so I went the route of having this machined to fit. Problem was, turned correctly on the injection pump pulley's hub it stuck out to far and wouldn't align. Turn it around backwards and it would align but would hit against the injection pump bracket, its "bubble" on the one. So...problem fixed
Before:

After:


Now, everything is here with the exception of Swaintech doing the pistons for me in TBC and PC-9 and the need to get Racewares... March, here we come!
A few more pics... Will readily start working on assembling the bottom end tomorrow. Have to press in new int. shaft bearings, then do the crank, etc. while the pistons are being done.
Gov. swap on the Cummins pump went like a charm and now with the added adjustablity of the injection pump sprocket on the fly should make for a really nice setup come spring. Also, to those wanting to clue in on using the cummins pump, give me a shout, IDI or TDI and I can help you out.

Man, that block looks great, what did you paint it with?

Cummins Beige... I wish the block would have cleaned up nicer, but even after blasting it after it came back from the shop it still had pitting on the back of it... Front looks great though...couldn't believe how "rusty" the back of the block was for only being 126k on it when it was removed (wrecked Passat 97) and only being that old. I have blocks from Rabbits with 300k on them that looked better on the back and were in the Northeast all their lives!

Joe

Those pistons now look like the t4 5cylinder one's from an overhead shot.

mojogoes said:

Those pistons now look like the t4 5cylinder one's from an overhead shot.

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I searched and couldn't find it.
Could anyone post the Part #s for the appropriate T4 5 cylinder pistons/rods to use for an ALH block?

AtomicSushi said:

I searched and couldn't find it.
Could anyone post the Part #s for the appropriate T4 5 cylinder pistons/rods to use for an ALH block?

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I could have a look through ETKA NA and Euro...but never having much luck with the pistons/rods themselves. I had that written down here from a LONG LONG time ago somewhere...i'll do some digging for you if someone else doesn't find it first...

And...i could resist...one more time since this post started with my piston search when leaving the 1z style units...to ALH, to machined and now coated and in the block...

Any updates?
I am interested in building a TDI-M