PD/VE compression ratio dilemma

[oldskool rich]

ok as sum of you might know im building a 2.0 PD with an ALH VE head, the 16v PD has no recesses in the pistons for the valves, and as i want to drop the CR anyway i was going to go for a thicker head gasket, can i just hack one apart and use 2 extra copper sheets to make it thicker? or does anyone make one already that thick, the valves dont quite hit the pistons but must be dangerously close

i need sum suggestions, i cant go any further with my build until i know what im doing, bottom end is all fully rebuilt btw

[rallydiesel]

ok as sum of you might know im building a 2.0 PD with an ALH VE head,

Do you mean you are using an ALH block? Cuz that would be a lot of work converting an ALH head into a PD!!!

[dillenger1]

you should get one made?

[RabbitGTDguy]

I was wondering if the 2.0 TDI heads would fit the older blocks.

Why discard the 16v head for the 8v head?  What are you gaining there?  Do you just want to rid yourself of the PD electronics?

You can't just "rid yourself of the PD electronics" if that is the heading towards what your suggesting. The PD does not rely on a VE based pump to run the motor, but rather a couple electronic hi pressure pumps and each injector on its own operates as a "pump".  The 16v head would simply just rely on the electronics to run it. No real way around it.

oldskool rich's original plan for the ALH block base with PD components was for a stronger "stock" bottom end for a ALH VE based motor....not to run a PD setup.  You'd really just need to have the valve recesses cut for the PD pistons so that you don't run into any issues.

Joe

[aidan]

As an alternative, would the T4 2.5 tdi pistons fit? Physically in the bore, and to the 2.0 con rods?
That should then match the valves on the ALH head?

Then again, were people using these for the extra strength or for use on an overbored and otherwise scrap block?

[snakemaster]

is it flat top pistons , if so what cc do you have in the 16 pd head and what cc do you have in the 8v tdi head , then you can work out CR  with the 8v head  on the pd block , put the 8v head on  the pd block with a old gasket make tight  set cam timing and check for valve to head contact and see what your clearince is , you could put som eng blue on the valves to this would mark the pistons so if that needed moded you would see where, i my self would not go with 2 H gaskets  to get the CR down i would mod the pistons or the head , what CR you looking for 16 to 1 ?

[oldskool rich]

for those of you who may have got the wrong end of the stick, this whole engine has been built from spares so i havent done away with a 16v head, i just dont trust electrics enough to go with a PD so im running the biggest most powerfull 4 pot VE that you can shake a stick at.

i dont know what CR im looking for, i want it to start up no trouble up to minus 10 degrees and also run up to 40 PSI of boost without cracking my head so if sumone can tell me what i need, that wud be great

i think the best course of action will be to get my valves skimmed flat the same as the PD 16v and then get a thicker after market head gasket, anyone know a pace that sells them? i asked GSF for the thickest one but i dont think it will cut the mustard, unless the PD can run this much boost no trouble, anyone know?

[RabbitGTDguy]

You'll need to be careful removing anything too much from the valves as I believe they are still sodium packed. I could be wrong though. Haven't gone that route before.
As for compression. I can attest to lowered compression as I have the mTDI in the Mk1 down around 17:1 or so, close to the VWMS specs. I'd have to look at my old sheets or see what I reported in my build thread as to what EXACTLY i arrived at. Too many numbers in my head at the moment.

As for a head gasket. If your going for a "thicker" head gasket for the sake of lowering compression...a headgasket is NOT the way to do it. Yes...yes...it has been done, blah blah blah but it is still not the most efficient way to lower the CR as in doing so with a thicker head gasket (like alot of budget gasser FI cars do) your going to hurt the squish volume of the motor...especially if you intend on going low. If you really want to go that route, stock metal headgasket could be taken apart and put back together to achieve a "thicker" gasket. Or...you can look to companies that do copper o-ringing of motors and custom head gaskets to get a thicker one. I can't remember the name of the company stateside that I was looking at...but originally, I considered this route when I was still working with the ole' IDI TD engine in the original GTD. I remember a good discussion that we had on the old board about it as well...and WHY not to go with a thicker headgasket.

Anyways...my .02

I'll be happy throwing mid 30-40 psi at the mk1's mTDI motor next year and have no worries of doing so with the route that I took to lowering compression and the ceramic coating that I did as well. The new turbo will warrant and allow that to happen and it'll be fun to see what it does as long as I can find a clutch that will hold it together as I'm seeing major slippage now if I hammer 25psi in 3-5th. The 02a will be solving alot of those problems *which is running a Stg 3 020 clutch...but not as strong as what a comparable 02a STG 3 unit would*.

With the lowered CR in the mk1, I can still EASILY start the car down to about 30F without glow plugs...its just a smokey start. With glow plugs I had no issues at the VWMS spec CR at -10F last year when starting the car. Just cold start smoke to deal with at startup until it warms up.  

Joe

[oldskool rich]

do you meen i should get the pistons machined and coated? ive put all that stuff back together now and also that sounds like mega money that i havent realy got atm, well if i just skim a fraction off the valves that will put the head back to standard and then was just gona put in 2 more of those tiny copper strips that go each side of the head gasket, should just drop it a fraction without going nuts, im running on biodiesel so start up can sumtimes be an issue, my AAZ can take 35psi+ with stock gasket so im sure this will be fine

unless anyone deeply objects

[RabbitGTDguy]

No, I'm not saying that you need to. A suggestion...maybe, but that is a choice that you would need to make. I did a few calculations when I did the mk1's mTDI motor that helped determine "where" my CR is currently at.
You would need to do the same calcs to see where you are at as well...if you want to succesfully lower it to a point that you want *i'm not sure what that is...what are you looking for?* and I can tell you that the copper shims only are not the most effective way to correctly lower it...nor if they are too thin will they do much of anything at all.
I'm not sure how much you could successfully remove from the valves. I seem to remember someone on here substituting one type of valve for the VW sodium valves before...but who that was....I can't quite remember. I even remember someone experiementing with tuliping the valves as well...
Again "how much" are you talking about removing? .005mm?, .005mm? .05mm? just to throw random numbers out to you. Have you determined how much you would need to remove to have success, etc?

No need to pull things apart, etc. if you don't want to. I considered the ceramic coating CHEAP insurance when I did it and it wasn't bad. I was under 200.00 to have all 4 coated with the TBC top coating and a PC-9 skirt coating. I'm sure the prices are comparable over your way.

As for machining the pistons. In your case that method really wouldn't work all that well the same exact way that I did mine since the PD pistons lack a good portion of the combustion chamber bowl "lip" that exists on the ALH units like I have.

Joe

[Tintin]

Making a PD engine working with basic electronic is not a big problem, much more easy than what you tried to do, it's just a pity that you demoted to the mechanical pumps, you cut the potential power in half.

[RabbitGTDguy]

Agreed, especially considering the PD's and the latest motors that will start popping up now with the CR injection. I'd be interested in seeing what people are able to pull out of the newer designs electronically. Honestly, pump wise...and though a big support of mTDI motors... the newer motors were motors that were designed around electronics...not older tech designed to blend and look for temp solutions to meeting emissions and creating efficiency like the VE based TDI's were. Truly, in their natural form...they have a hybrid pump that relies upon electronics to operate an essentially mechanical pump *that was made to accomodate electronics after being fully mechanical since its conception*.  The newer motors take advantage and exploit potential to the extreme.

That said...when acquiring the 'rado that Duane has, I think this is the route I'll be taking with it. A crazy simplified PD motor or a new CR swap in a year or so once a few have been totalled on the road. A diesel fleet! Two mTDI's for that older school feeling...and a PD or CR in the 'rado where old school again meets new tech...but keeping more of that new tech. Def. powerful, efficient and with very few sacrifices...

Joe

[oldskool rich]

well i havent got the money to pay for any piston work atm, it starts at £100 which i dont realy have and not conviced its needed, i didnt listen to people that told me my AAZ wud blow up and a year on and its still going.

im taking about 0.6 mm of the valves. i know that you say head gasket is a big no no but i dont hav any other options, 2 copper sheets make 0.5mm or i cud use the middle peace that is 0.6 but then must use another copper peace to seal it so can ether go for an extra 0.5 or 0.85 what do you recon? i dont even know where to start to work out my CR, will be whatever a stock 2.0 PD is then + 0.5 or 0.85

i will be going for a 16V pd head in a few years, i just want to see what i can do with a VE, i know i wont get much over 250 bhp with this method but then planning to use methanol injection and loads of extras to get it up to 350
i am aiming for this to be the fastest 8V in the world but maybe im way off :roll:

[snakemaster]

Hay bro why dont you get your valve seats recut 1mm -1.5mm that will help in the cr , are you using hyd follers ?  and if you skim .5mm of the pistons ,put them in a laith your self , your cr should be 15.5-16 to 1 rufflay you would need to work out your cc to get the exact cr  :wink:

[oldskool rich]

thanx snakemaster, im gona try the gasket first because that will amount to the same thing, if that fails then i will skim the pistons, im running hydraulic tappits, was to hard to convert to mechanical