Quick question, hopefully this weekend to have an answer.

[theman53]

They seem to take some off the top of these pistons when replacing. I think it is so if you have to take off some of the deck to true it up you will still be able to find a HG for it.
Myke W here got me a MLS 1 notch just last year, so you might start there. I would ask 53 willy's where he got his custom made as that guy could easily make an AAZ if he made a MLS 1.6. That is if you can't find them.

[vanagonturbo]

Well, the pistons are brand new, so I dont think its likely that the tops have been machined...

I did find an AAZ one notch, but I have to get it from the dealer and its $70USD! Now the question is, does anyone think that a one notch difference combined with larger precups is going to cause such a loss in compression?

I have not had a chance to CC the precups yet...

any additional input would be helpful! thanks for reading.

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I don't think it will.
I have the same engine build that you do, 1.6L bottom end 1.9L AAZ cylinder head. 1 notch gasket and KS pistons. It ran slow and smokes on start up. Until some heat was built up and then the smoke goes away. Thats even with the pump timing set to run better on the top end when warm than cold start cocerns. It smoke till warmed up a bit, not fully warm but till at least 300deg. on EGT gauge. It always starts right up but smokes a little. I had a 3 notch in it before but didn't seem to make any difference. Also 1.6 TD injectors made it smoke worse than the AAZ dual spring injectors I have in it now.
Of course, I have a custom built pump and I'm boosting 30psi and wide open throttle most of the time.
Untill some one comes out with the info needed and gives the exact parts needed, pump needed and timing specs for you build, 1.6 bottom end and 1.9 AAZ head, thats how it'll run. Slow to throttle responce under load, clacky noises, smokey starts and high EGTs.

[vanagonturbo]

Perhaps you have not read the whole thread?

I didnt think the gasket thickness would be the culprit either. but 275 psi on a hot motor is still pretty low. Then there is that whole part about having a mere 15psi of boost on a GT20 @5500 rpm. I had a Giles pump that was built for this engine, but there are some bugs with it and Giles (being the awesome guy he is) is going to handle it.

I expect it to smoke on start up. No complaint there. It smokes like a *** and thats fine for now.

I really want to address the compression problem as I feel that it is the root of the low boost situation.

Thanks for your input, it is much appreciated! Perhaps in light of some of these things there is more you might know? Or possibly suggestions of things to check?

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I have read your posts, but its been a while. Sorry for the snide replies. Yes those compression #'s would be a problem. I don't remember if you had done a leak down test or not, but 275 is not good. If you've pulled the head and it looks ok, then pulling a piston will be the next thing to check what the rings look like unless the cylinder walls look glazed/washed. but in your earlier post back you said that the pistons are new. maybe its a broken ring?

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What brand of pistons did you use.

I had used a new set of pistons from Prothe and the rings he sent with the piston kit were broken right out of the box.

[Rabbit TD]

I think I would doulecheck to see if your cam and crank are timed correctly while you are at it.  You could be off some there affecting your low commpression.  Like another member said, most aftermarket pistons are about .005 lower in deck heigth to allow you to mill the block surface that amount if needed and still be in the right range for avaiable gaskets.  What is the compression spec. on the engines that use the head you have on there now?  You should still be reasonably close to that range.  Are all the cyl.s showing about the same amount of compression?  If they are all within around 20 psi. of eachother I'm sure you didn't crack any rings putting it together and with total seal rings especialy they should be sealing pretty good even now, even better as time goes by.  My rebored 1.6 TD with The new 1.6 TD head showed just about 500 cranking before I even started it the first time, lots of assembly lube in the bores and ring lands at the time though also but 20,000 later it still shows the same.  I did have to use the 1 notch gasket instead of the 2 notch that was on it because of the .005 shorter pistons which I compared with the originals and are exactly .005 shorter and you should deffinately use the next one down too.  I know the later engines have a good bit lower compression ratio as previously stated but what are the compression specs. on them, I have no idea, but you should be close to that. I would almost bet that if they show a significantly higher number than what you have now that your crank moved when you tightened the belt tensioner changing the valve timing enough for it to have the lower compression.  You are right though, the compression has to be right first before you even think about anything else, nothing makes up for the loss of it to run like it should let alone even better.  Check those marks on the flywheel and with the cam locked in the back and see where it is now just out of curiosity.  I know you will because you will always be wondering from now on if you don't

[theman53]

The pistons being brand new is my point. They do machine them, no way could they cast/forge pistons that good to just drop in the engine. I am saying new pistons they cut a little more off the top, just in case you had to take say .010" off the deck to get it straight after a bad over heat. Then if you were in a 1 notch before and cut .010" off you could still run a 3 notch or so instead of taking your newly machined block to the recycler.
Myke w still probably has the 1 notch aaz.

[vanagonturbo]

when the head was still on, I triple checked the timing to make sure cam/crank correlation were correct. I even took an injector out and used a small screwdriver to verify TDC in the event that there was a problem with the marks on the flywheel.

I also did a leakdown test. I do not have an actual leakdown tester so I made an adapter out of an old injector and connected it to shop air. i have used this method many times on gasser motors, so I am familiar with it sounds like if there is leakage somewhere. it turned out that there was only minimal leakage through the crankcase and none out of the valves.

compression was checked in all 4 cylinders and it was 275psi plus or minus 5psi.

I beleive an AAZ has a compression of about 450psi on a healthy engine. The head is an AAZ head and the head gasket is an AAZ gasket.

gotcha on the piston crowns being machined. that makes sense :thumbup: the pistons I used were KolbenSchmidt which I beleive to be OEM.

I did not use assembly lube on the rings. I have never done that and have always had success with putting them in dry...

thanks for all the input guys!

[vanagonturbo]

UPDATE!

Ok, like I said, longest diagnosis procedure ever! I sent the head out to the machine shop. they checked everything and came to the conclusion that there was nothing wrong with it at all.. They also decked it 10 thousandths. While the head was off, I pulled the pistons and rechecked the ring end gaps. They were a little wide but still within spec. I swapped the upper compression ring and the oil scraper ring with iron rings as opposed to the chrome ones that I installed first. It was advised to me that I should be using iron rings instead of chrome rings... I was also told that the oil pump was too large and causing the lifters to overpressurize causing the valves to stay open. I wasnt really buying that story.. I checked the oil pressure after I put it back together and it was about 23psi at idle when hot.

So, I put it all back together and added an ALH cam which had significantly less valve overlap (none) vs. the cam that was in there to begin with. Road tested and checked boost. Boost is the same. No change. Now here is where it gets kinda strange; compression tested it today and it was 450psi with the engine running and 400psi with it not running. I have no idea what the difference could have been other than the cam change.

Either way, I am beginning to think I made a $700 mistake on the turbo. Sure looked good on paper. Sure doesnt feel good on the butt dyno, wallet or the boost gauge. I am contemplating installing the stock TD T3 turbo just to get a baseline.

If anyone as any further ideas, that would be great!

[vanagonturbo]

Thanks for the input. This is actually in a Scirocco. I have a few diesels the T3 was in reference to the stock 1.6lTD turbo. the only reason I mention it is because I have one on the shelf that I can use. My Vanagon has a K03 already and no issues.

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So are you going to sell the turbo? How much?

[vanagonturbo]

Whcih turbo are you talking about?

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The GT2560R.
Are you having trouble with it. Sorry, I havn't read all of your post through yet.

[vanagonturbo]

Having trouble with the gt2056, not the 2560. I dont really want to sell it though. I have other cars that may need it