First I care less than nothing about emissions and care for mpgs a lot

I know we get TDI-PDs with lowered compression to lower NOx output . Could we get an increase in mpgs with a thinner head gasaket an increased compression ??

I'm convinced that the higher compression in my 1Z TDI due to the use of a thinner head gasket one called for in the specs. is the reason that I have had a consistance 20 % mpg over befoe the change .

So along those same lines the TDI-PD engines compression is lowered to reduce NOx but at a cost of mpgs . So if we were to go to the next thinest head gasket increasing compression and raising mpgs averages ???.

This would increase mpgs and raise NOx output but as I said eariler I care less than nothing about NOx but would be very happy to booste the mpgs by 10 or so mpgs .

Any input on this theroy on this idea of increasing mpgs by using a thinner head gasket to raise compression thereby inceasing mpgs working on a TDI-PD ????

T%his idea dawned on me after reading some diesel emissions related articles . The articles dealt with the stupid American restrictions on NOx that are not doing anything to clean up the air and achieving nothing other than killing mpgs .

I dunno about any practical use on TDIs, but AFAIK the theory is sound: with other factors being equal, higher compression equals higher fuel economy.

You won't get a lecture from me on the NOx emissions...I'm convinced that they've been far overregulated anyway. They're just a catalyst...CO, HC, and particulates are the bad guys.

Mike

Decking the block or milling the head will probably make a significant CR difference - Have to do the math again, but I think the 0.010" that you "MIGHT" get out of a thinner gasket won't change the CR by more than a few tenths of a point.

The oldsmobile 5.7 liter diesel ran 22.5:1 in stock form - adding a 0.010" thicker gasket to help account for the 0.020"+ milled from the head to straighten it (for a net ~0.012" 'shorter') only raised the CR by ~0.5 points (by calculation only)

Being a full 3 points lower on an ALH motor (dont know what the CR is on a PD (BEW?)) you have to make a bigger change than ~0.010" to achieve any meaningful change in CR.

I agree with your theroy though, it's a tough/and or $$$ modification.

Milling the head wont help much, the head is already flat, save the area for the valves, as this is a DI engine, with the combustion chamber inside the piston. A thinner gasket is the way to go, but be careful, you must measure piston height above the deck at TDC, there has to be some clearance. A engine running at high rpm has some slack and stretch, which under certain operating conditions, can allow the top of the piston to have an interference fit with the cylinder head if the gasket is too thin, resulting in catastrophic engine failure.

I think that the lower compression is a benefit to a turbo charged diesel. The 2006 may be as low as 17.5, stress. Your head is marked for its gasket. As CaJones said there is some stretch how much is crucial.

I did not know the piston is actually above deck. That really does complicate things. You are in NC and there are many experts within 2 to 3 hundred miles.

I have a feeling that this theory may also be in effect for TDI owners that have upgraded to ARP head studs and also seen a nice bump up in MPG. I'm thinking that the ARP studs allow less stretch and play in the head and thus offer higher overall compression.

Do any of the chips disable the EGR? I assume that they run a little higher boost too. Would this not have about the same effect, while still being able to take it back to stock? Or maybe buy aftermarket heads that have a small chamber?

When I first got my car in 4-02 I read some were that I can not find now that the base Ero. TDI had 1/2 more CR then ours do and it was a thiner gasket.

Looking to undo what VW did to reduce compression

What I was thinking was if the car came with a 3 notch head gasket , if there is enough physical thickness to spare ( piston protrusion to spare ) I would drop to a 2 notch head gasket . For those that don't know 1 to 3 notch head gaskets are used on these engines . 1 notch being the thinest , 3 notch being the thickest to deal with piston protrusion .

IF there is room to do so that would raise compression some . This worked well to raise the compression on the old IDI diesels .

But the TDIs combustion chamber is inside the piston so a larger chamber inside might be how VW lowered the compression . IF that is the case we would need to find pistons with a smaller combustion chamber to raise the compression enough to get a real increase in mpgs .

Somehing else I know for a fact that VW did to lower compression was to use smaller pistons on the old 1Z engines . I've rebuilt 2 1Z engines and both engines had pistons smaller than could have been used . In fact without reboring the engine I was able to use the next oversize piston .

So I put 1st oversize pistons & replaced the 3 notch head gasket with a 2 notch . These changes raised the compression and could very well be why I have consistantly returned mpgs in the 50s for both the cars entire lives .

or you could fill the plenum I guess to call it in the piston. That chamber in that piston was designed to help with combustion. So I would imagine you would want to decrease its size and not change the mix to much. Does any one know if the germans make optional pistons, maybe for racing.

Mike_M said:

...
You won't get a lecture from me on the NOx emissions...I'm convinced that they've been far overregulated anyway. They're just a catalyst...CO, HC, and particulates are the bad guys.
Mike

Click to expand...

So when NOx mixes with water vapor in the air it DOESNT form nitric acid? And the forests of the NE United States AREN'T damaged (forked trees, etc) by acid rain? Oh, ok.

SO2 coming out of the power plants and gasoline powered vehicles are the main cause of what you describe . NOx that comes out of auto diesels are not the casue but get much of the blame so that loophole vehicles and coal power plants can poor out tons more SO2 .


What you are quoting is political garbage that the power producers and the big 3 want you to say . NOx is the phantom gas that covers many different gassses that do not come out of auto diesels .

PDs can get awesome mileage as well. my jetta with rc2 recently got 57.4mpg by driving slow (50-65) - see my recent thread about that in the fuel economy section for details. previous tanks had been 52 and 48 (by driving slower but not quite as slow)...

i can't comment on any of the head gasket, piston, etc stuff... i'm not that experienced but i also think nox from auto diesels is small peanuts. the tdi's already put out far less CO, CO2, and the harmful tiny particulates. engines last longer, oil changes are generally less frequent than most cars - all in all reduce the environmental impact a tdi has on the environment.

More boost would do the same thing. A simple performance chip can do that, without even taking the engine apart.

The best diesel (in terms of power, efficiency, etc.) would have very LOW compression and very HIGH boost. Problem is if you go too low with the compression, the car won't start, since there is of course no boost at start-up.

I really don't think the PD is nearly as bad at fuel economy as some think. Too many people rely on the outdated EPA rating on the moroney tag which is pretty worthless if you ask me. Our 2-ton PD Passat, automatic and all, gets within 3-4 MPG of my 1.6L Jetta. Pretty good if you ask me.

No It really did happen

No bull the bore was sized for the 1st oversize but had standard size pistons from the factory . I wouldn't have believed it if I hadn't seen it .


I did no boring and dropped the 1st oversize . Not just one engine but I found this on 2 97 Passat 1Z TDIs .

rotarykid said:

SO2 coming out of the power plants and gasoline powered vehicles are the main cause of what you describe . NOx that comes out of auto diesels are not the casue but get much of the blame so that loophole vehicles and coal power plants can poor out tons more SO2 .


What you are quoting is political garbage that the power producers and the big 3 want you to say . NOx is the phantom gas that covers many different gassses that do not come out of auto diesels .

Click to expand...

I see, so because SO2 is a primary component of acid rain, NOx doesn't matter. Makes sense to me. Wake me when the revolution comes.

Gothmolly - You might find this page enlightening. http://www.epa.gov/nitrousoxide/sources.html More nitrous oxide comes from farming than all other significant sources COMBINED, including vehicles. Nox gets a bad rap because it's an easy tail pipe target but I'm guessing a single bolt of lightning
forms a lot more Nox and ozone than a whole bunch of cars. Nitrogen oxides won't destroy the world they just happen to get along well with ozone to make smog which can irritate peoples lungs... maybe people should be irritated seeing as they insist on driving everywhere. Bacteria get along fine with Nox and N2O. It ain't poison.

Use Boost

Only on non-boosted engines is CR so important. The Olds 5.7 was an atmosphere boost motor. 22.5:1 x 15PSI atmosphere = 337# - effort
15:1 x (15+15boost) = 450# - effort 2 more pounds boost = 480#

It is a lot easier to add 2# boost than to find 1 more point of CR in heads/gaskets... only bigger bore.

RT1 said:

Gothmolly - You might find this page enlightening. http://www.epa.gov/nitrousoxide/sources.html ...

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My point is that the attitude of "I know I'm putting extra NOx into the air, but I don't care because everyone else is doing worse" is shortsighted.

How about I piss on someone's lawn, because hey, there's worse pollution they should be worrying about?

Can you come pee on mine, I hate cutting grass...

pee'ing on the lawn does wonders for making green grass! as long as you don't pee in the same exact spot everytime....

by urinating outside frequently, i made a very nice green healthy lawn.... and also reduced my use of water and septic system...

Not mine, my pee must be evil.

can I watch

wjdell said:

can I watch

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Who.... oilhammer, burpod or gothmolly?

Good Golly Gosh Molly

Gothmolly said:

My point is that the attitude of "I know I'm putting extra NOx into the air, but I don't care because everyone else is doing worse" is shortsighted.

Click to expand...

...but only IF you accept the premise that NOx is a Bad Thing, which is what is being disputed.

(not joining the argument, just pointing out the obvious)

Mike