Getting There! 2 The AFN strikes back..

[max and caddy]

A bit more has been done on the new engine...first of all actual bore size has been determined, and is 0.02 larger than the nominal size...so nothing to worry about there..however as the base of the bore is not worn in use and Andy did tell the factory hone marks were still present on the bore before it was honed I do wonder where the 0.02mm of metal went..if it was ever there of course! Anyway it's within spec, and even with the 0.02/3 of dectected wear (measured at the top of the bore at 90degress to the gudgeon pin it well within the 0.10 max difference...viewing it as half worn is not really valid either.

So, happy with the holes I started on the things to go into them, rings removed, grooves scraped clean with bit of broken ring to remove carbon...found one oil ring stuck in due to carbon build up as well, pinged free easy but was stuck in..

Now these pistons are a little odd...normally behind the oil ring is a few holes to allow oil to pass into the sump...but oddly these pistons don't feature the holes...looks like they do but there is no hole..


So I checked on my Afn...and sure enough holes are there...must be a production change and reason is unknown to me...mine..

I know it's dirty...but see the holes?
Also...pistons are smaller than stated in the book!

79.44

I'm certainly not worried...but strange non the less!

Also measured up the crank...it's unworn! Less than 0.01 of wear on the big ends thrust side anyway...I have some plastigauge to check oil clearance on assembly as well.

Need some bearings and some rings now...

[max and caddy]

The piston size markings have got me wondering so I dug out a pic of my Afn ones...79.46.. Closer to what the book states but still not quite...however I am using a 1Z book...but also check a newer BXE pd book and that has the same figures stated...I guess it's just one of those vw things sent to confuse..good news is that the piston does actually measure the 79.44 it's marked with so isn't worn to any measurable degree.



My pistons look hammered compared to lloydys!

[lloydy]

Good pics
a little search on tdiforum showed the pistons come in a few sizes..

79.44, 79.46, 79.47 or 79.49 mm

79.44 is the most common size and it also lists those sizes in ETKA
Odd with the oil holes, is the pretend hole where the oil ring sits, or is it the next one up? Trying to understand why the holes would have been needed.
Out of interest, do the rings just come in one size then, to fit all the different size pistons? i guess so?

Good news that the crank is healthy Let me know when you need funds for the rings ect

[max and caddy]

Rings are "standard" and as long as the grooves are correct the piston has nowt to do with them really...the bore and the end gap are all the rings need, not a piston if you see what I mean..

The holes are not drilled but the piston skirt is not a full circle either..so oil can drain Dow the sides and into the pin area..there just different...every piston I have seen for years had holes in...but I guess it may be stronger however. It obviously works ok and as the motor was a 99 version I guess it has a reason behind it.

I will talk to the local engine guy about a ring set...if he can't supply top spec ones I will get a price off vw..I don't like the 3 peice oil rings much so will try and avoid if possible.

Pistons are a selective fit by all accounts..will ask andy what came out and even use some other pistons to be sure.

Bearings are more straight forward at least and will get those this week.

[lloydy]

by selective, do you mean the block should keep the same size pistons it came with from the factory? A little googling suggest so.. let me know if i have to look out for a set.. hopefully Andy's pistons from the block are .44

[youthy giblets]

Nice build you've got on the go here lloydy, should be pulling decent power without running issues when it's done. Just out of interest how much we're your new nozzles?

[lloydy]

hi, nozzles were £125, and setting up and balancing inc both opening pressures was £125. So, £250 in all. Nozzles are HFLO-X

[max and caddy]

by selective, do you mean the block should keep the same size pistons it came with from the factory? A little googling suggest so.. let me know if i have to look out for a set.. hopefully Andy's pistons from the block are .44

There is no real stated rules to go off...if I were to order a replacement piston from an aftermarket engine part supplier I would be offered one of 3 sizes, standard (often not available for vw engines anyway) or first or second oversize..that's it..but from the factory they size them into different groups, and also have different weight groups. 2 hundredths of a mm is not a concern really, but would be good if the figures matched up to the manual!

Don't read a lot into it, there's more to pistons than running clearance and size variations may be due to material specs of manufacturing developments. A tighter bore clearance is good in some ways for noise, oil use maybe, but can also mean seizure is more likely if overheated or over fuelled for example...a loose clearance can be a good thing as long as its within spec.

Rings are sized to the bore by the way, standard, 1st, and 2nd..

[max and caddy]

By the way...an average human hair is 0.05 mm thick as a comparison!

[lloydy]

such small measurements.. hopefully this block had the same size pistons

[lloydy]

It's all a bit over my pay grade though really, so I'll defer to your experience on the importance of it. If it needs different pistons, I'll try to source some. If it doesn't, it doesnt

[lloydy]

Grrr, bloody winter! Looks like I'll be removing injectors in the rain then! Need to start stripping the van out for bodywork too

[lloydy]

Removed the injectors, the one that was down on psi is the one with a lump of soot on the end.......
pic of the opening pressures for the HFLO-X 0.216 nozzles
(220-300bar)

I've refitted one of the standard sets of 0.205 injectors, the 0.216's ive put in a container of diesel hoping it will clean of some of the soot on the end. If it doesn't i'll just leave them as is, as i don't want to use a brush and damage them..
Also removed the expensive new bosch MAF and fitted the spare copy one i have
As you can see from the pics there is a fair difference in them
lower one bosch

[max and caddy]

Why have you removed a good Maf and fitted a crap one?

[lloydy]

As a precaution, the cheap one works fine as well. Want to keep the expensive one for the new engine. Funnily i had the cheap one fitted for ages thinking it was the good one so it's basically brand new:lol: