just had a few quotes for getting the crankshaft lightned and balanced plus polishing the journals... under

i spent some time cleaning the pistons today.. it's a horrible job and i have little cuts all over my hands now...

used wire brush wheels and to clean the carbon deposits from the crowns, broke up one of the piston rings and ground it down to a point and used it as a scraper to clear the crud out of the ring lands

i feel i should say a few words about pistons now.....

piston terminology:

crown: the bit on the top

skirt: the area at the sides which are below the pin

gudgeon pin: the pin that is goes through the centre of the piston and through the small end of the conrod

piston height: the total length of the piston from the top to the bottom

compression height: the length between the top of the crown and the dead centre of the gudgeon pin bore

bowl: the reccess in the top of the crown

lands: the recess in which the piston rings fit

this particular piston is a very high quality hypereutectic casting it has a full skirt and is cast all the way accross the gudgeon pin bosses which although adds weight it makes it a very strong piston. there is only one potential design problem i can see with this piston, in the bottom ring land it has oil control holes drilled through to the centre for, they allow the oil to escape into the centre of piston after it has been scaped off the bores by the oil rings.. these holes weaken the piston which could lead to the skirt breaking away from the crown, but this highly unlikely!!!

it is a fully floating design too, which means that the gudgeon pin is secured into the bosses with a small c clip at each end and the pin can rotate freely in the bores, the other method many other manufacturers use an interference fit pin which is fixed in position by heating the piston, then dropping in the pin in and when it cools down it 'locks' in place. the fully floating design has the advantage of being easier to assemble and also because the gudgeon pin can rotate it doesn't get worn out on one side only and hence lasts longer... the disavantage of the fully floating piston is that there are 2 c clips in there and somtimes they can jump out at very very high revs. and it is fairly castrophic for the engine:eek:

all vw pistons have an arrow scribed into the crown, this arrow allways points towards the timing belt end(front) of the engine. except the vr5/vr6 engines where the timing chain is at the back of the engine, but the pistons still point towards the front(if that makes any sense:D). this is the case for most other production engines except renault/peugeot/citroen where the arrow points towards the flywheel end(back).. dont ask me why... it's probably because the french are nuts:rofl:

you may notice there is a vw badge cast into the piston too, but it only has one, there isn't one on the other side. it isn't there just for show, there is a vw badge forged into one side of the conrod as well, and when assembled together the badges are allways the same side which helps you assemble them the right way round!!

this piston is more than capable of handling a massive increase in power.

you barsteward!

I spent the day cleaning road grime, 19 yrs worth of oil and wax off the inner front gizzards of the touring today:mad: and you were playing with pistons....:thumbdwn:

gah!

good cleaning work, although I would have soaked them in gunk overnight to loosen the carbon then scraped off.. wire wheels do my box in!

Gonna lighten them or fit total seal rings?

Whats the plan re compression? ITBS and stand alone management has gotta be good for 10:1 min:thumbup: :confused:

Whats the plan re compression? ITBS and stand alone management has gotta be good for 10:1 min:thumbup: :confused:

yeah i've looked at that... unfortunately the deck hieghts of the pistons are very close and not much can be done there.... so the only option is to have the head shaved(skimmed). but i dont like doing that for road engines...

i need to think about it for a while:confused:

yeah i've looked at that... unfortunately the deck hieghts of the pistons are very close and not much can be done there.... so the only option is to have the head shaved(skimmed). but i dont like doing that for road engines...

i need to think about it for a while:confused:

how much of a skim are we talking?whats the stock comp ratio?

wouldnt be a worry with a CHAIN driven MPi lump:rofl:

the stock compression ratio is 9.8:1 which is theoretically perfect for normal unleaded fuel. but you have to consider volumetric effieciency too, with the throttle bodies and better breathing capacbilties it may be more benificial to keep the compression ratio nice and low....

the absolute maximum i would ever have skimmed off a head is 0.5mm, but to be honest this is way too far and it means you have no safety net whould the head gasket blow in the future and need skimming again. so on carefull consideration i'm going to get this skimmed, but i only want the bare minimum taken off

the stock compression ratio is 9.8:1 which is theoretically perfect for normal unleaded fuel. but you have to consider volumetric effieciency too, with the throttle bodies and better breathing capacbilties it may be more benificial to keep the compression ratio nice and low....

the absolute maximum i would ever have skimmed off a head is 0.5mm, but to be honest this is way too far and it means you have no safety net whould the head gasket blow in the future and need skimming again. so on carefull consideration i'm going to get this skimmed, but i only want the bare minimum taken off

Fair enough. iirc, the correct volume of fuel to air for max efficiency is 14.7:1 or thereabouts (if suitable fuel etc used-taken as purely theoretical!)

so given that the TB's and standalone can precicely monitor air intake per cyl, surely you could bump her up to 11:1 or so with no major issues

Fair enough. iirc, the correct volume of fuel to air for max efficiency is 14.7:1 or thereabouts (if suitable fuel etc used-taken as purely theoretical!)

it is true that the correct stoichhiometric ratio for air to fuel is 14.7:1 for complete combustion and also the economy will be higher. but in reality the engine wont actually make the most power at this ratio. but it is a very good way to set up base fueling map settings using solely the lambda probe to sense the air/fuel ratio, it is probably more like 13:1 at full load but this will have to be worked out on the dyno

so given that the TB's and standalone can precicely monitor air intake per cyl, surely you could bump her up to 11:1 or so with no major issues

there is more than one school of though on this subject, but aside from writing pages on combustion theory, here's how basically it works... with a higher compression ratio there is (theoretiacally) a higher compression, and hence more heat in the combustion chambers.... which means the ignition advance angles need to be retarded to avoid pre-ignition(pinking). and it is a well known fact that an engine with a lower compression and more ignition advance will make more power (upto 5%)

the ideal compression ratio for unleaded fuel is just under 10:1, but this assumes you have a 100% volumetric effiency, but in reality most n/a engines ever go higher than about 85%, so in these cases the mechanical compression ratio can be made higher, some modern production engines can go as high as 11.5:1 but working on a 85% theoretical VE that comes about 9.77:1

that being said, it's also worth remembering that the VE isn't uniform throughout the entire rev range, it may be as low as 50% at 2000rpm say, but be upto 70% at 6000rpm. this is due largely to the valve timing and the porting. the other point to note, is that the rpm where you are getting peak torque is also where you have the higher volumetric efficiency and this is how car manufacturers set thier compression ratios...

on later cars they do it slightly differently because of economy/emissions. they set the compression ratio by the VE at the rpm range where the car will be doing most of it's driving(cruising/motorway) probably around 2000rpm. but at 6000rpm this becomes 'too much' and this is where the modern engine management systems with knock sensors are used to back off the ignition timing to prevent detonation.. but all this gain in economy at 2000rpm is offset by a loss in power/economy at say 6000rpm due to retarded ignition...

so as you can tell there is allways a trade off somewhere, and what you gain at the swings you loose at the roundabouts... it's not just a case of blindly 'jumping' in an grinding the head down to raise the compression

i'm sorry if i've blinded everybody with science again, and i hope it makes sense:O

but in summary in regards to my own engine, i shall be keeping the compression ratio nice and low and go for a nice advanced ignition angle(at the cost of fuel economy)

thanks for that Tom- always beena bit of a grey area, that whole "high comp, retarded ignition, or low comp, advnaced ignition" thing.

VE is a bitch- makes for fun calculations when trying to install blowers....

A big thankyou goes out to Richard at Keith's Welding & Fabrication in Portsmouth for very skillfully welding up the mistake i made whilst porting this head..

now i have to very very carefully grind it back with the carbide burrs:O

i've made a bit more progress today.

pressed in the new guides, then reamed/honed them to give the correct running clearance, regrounf the valve seats, lapped in valves, skimmed the old baby flat..

just waiting for my schrick valve springs to arrive from germany, then i can rebuild the head

edit: who can see where the weld is??

here's a close up of the exhaust valve seat, i used a special orbital valve seat grinder to cut a 3 angle seat onto them

and here's the intake valve seat, which also recieved the same treatment

1) is a 70 degree throat cut

2) 45 degree seat cut

3) 30 degree top cut

after the grinding, i lapped the valves in using coarse grinding paste, hence the dull finish of the 45 degree seat, then using a smear of engineers blue on the valve and double checked it made contact all the way around the seat.... then after finally lapped then in using a fine valve grinding paste

is the weld inbetween the left hand pot and the left of center pot?????

is the weld inbetween the left hand pot and the left of center pot?????

it's almost impossible to tell now i've groud her back, and skimmed it

looks amazing tom- wish I had the space, time, money and 1.6 felicia to match you mod for mod

Excellent example of the "3 degrees".....

i had a look inside the oil pump today....

there's nothing much wrong with it so i'm going to clean it up and re-use it..

this pump is a duosentric type which runs directly off the front of the crankshaft. it uses a pair of hardened steel gears to force oil around the engine... note: this is only fitted to engines made after 1998, the earlier ones use a chain driven oil pump.

the arrow points towards the pressure relief valve, i saw no point in removing it because there is nothing wrong with this pump other than the fact that it's filthy. but it basically has a pluger and a spring, when the oil pressure goes over a set pressure the pressure applied to the plunger defeats the tension of the spring, the plunger moves down and allows some of the oil to bypass the gears via a small hole in the plunger's bore.

the only other things to note about this pump...

1) the crankshaft timing marks (2v & 4v) cast into the pump, this is fairly self explanitary, 2v mark is for 8 valve engines, 4v is for the 16v variant, both use the same pump

2) the little 'dimples' in the pump gears.. these need to face towards you when you ressemble the pump because the innner part of this is tapered, and so is the front of the crankshaft, and they only fit on one way round

not the most interesting of things.......

but very necessary. got these from my local motor factors for

again not the most interesting thing in the world.....

the aee engine uses a plastic intake manifold as standard, so the cylinder head gasket set came with 4 little o-rings for that.... because i'm using a alloy manifold i need a proper gasket.... not sure what the vw part number is tho..

looks amazing tom- wish I had the space, time, money and 1.6 felicia to match you mod for mod

Excellent example of the "3 degrees".....

Agreed. Not to mention the mechanical know how. Is there any chance you would consider filming the rebuild and posting it in chunks on youtube? Would make an excellent resource - I couldnt find a decent video of a engine strip down or rebuild when I was looking a few months ago.

Agreed. Not to mention the mechanical know how. Is there any chance you would consider filming the rebuild and posting it in chunks on youtube? Would make an excellent resource - I couldnt find a decent video of a engine strip down or rebuild when I was looking a few months ago.

trouble is with that.. if i have to stop to film bits of it it will take me forever to get anything done..

should be more updates later today:)

haha... some more goodies

the basic idea is to try and prevent oil splashing up onto the crank which causes oil drag

got this from clubpolo

haha... some more goodies

the basic idea is to try and prevent oil splashing up onto the crank which causes oil drag

got this from clubpolo

Nice! you gonna mod the sump to avoid surge?

Nice! you gonna mod the sump to avoid surge?

i'm going to weld in some baffles in the bottom of the sump

i'm going to weld in some baffles in the bottom of the sump

is it an Alloy sump?That could be a bitch...