Tdi 300 turbo pressure

**rick130** · 10th July 2013, 12:40 PM

Originally Posted by Judo

Although Dave seems to have proven you can go higher than 18psi without blowing head gasket, there is a clear difference between pressure at intake and pressure at combustion.

Depends on the head gasket used too

Use a genuine Elring composite and it seems they don't like any more than 20psi, 18-19 appears to be a reasonable long life compromise.

Use a steel shim gasket and I'm sure you'll be able to safely wind more boost into it, but from what JC has said to me, unless both decks are perfect, (ie. as new) you stand a good chance of it letting go anyway.....

**Blknight.aus** · 10th July 2013, 12:44 PM

if you were going for maximum effeciency you would be advancing the timing, increasing the injection pressure + delivery rate, increasing boost and backing off the total amount of fuel injected.

want the anology question?

Whats the difference in fuel economy and power of a 7.5:1 2.25p and one thats been shaved up to 9.5:1?

**Dougal** · 10th July 2013, 02:34 PM

Originally Posted by Blknight.aus

Whats the difference in fuel economy and power of a 7.5:1 2.25p and one thats been shaved up to 9.5:1?

Well, my investigation on industrial petrol engines has found a pretty good correlation between compression ratio and torque. To the point where a 6:1 petrol can only do ~60Nm/litre and a 8:1 petrol can do around ~80Nm/litre.

Provided they can breathe well enough to get a decent cylinder fill when required; economy should roughly follow suit. On petrols.

Regarding head gaskets. I had a composite on my 4BD1T once (yes I know better now). It leaked around 18psi. Stock multi-layer-steel will take more than most single stage turbos can deliver. Randy made his leak somewhere after 60psi.

**Blknight.aus** · 10th July 2013, 04:57 PM

Originally Posted by Dougal

Regarding head gaskets. I had a composite on my 4BD1T once (yes I know better now). It leaked around 18psi. Stock multi-layer-steel will take more than most single stage turbos can deliver. Randy made his leak somewhere after 60psi.

yes, Randy and I are about to have some words......

**rick130** · 10th July 2013, 05:47 PM

Originally Posted by Dougal

Stock multi-layer-steel will take more than most single stage turbos can deliver. Randy made his leak somewhere after 60psi.

Except it appears the ones available for the Tdi aren't worth the aggro from JC's experience, they all seem to let go prematurely

It's genuine composite all the way and keep the boost down for moi.

**muzza99** · 10th July 2013, 05:56 PM

Thanks for all the avice

**Dougal** · 10th July 2013, 06:43 PM

Originally Posted by rick130

Except it appears the ones available for the Tdi aren't worth the aggro from JC's experience, they all seem to let go prematurely

It's genuine composite all the way and keep the boost down for moi.

Is there any scope in the head bolts for more torque?

I do realise that any extra load on the head bolts is also extra load on the (marginal) bottom end.

**rick130** · 10th July 2013, 07:40 PM

Originally Posted by Dougal

Is there any scope in the head bolts for more torque?

I do realise that any extra load on the head bolts is also extra load on the (marginal) bottom end.

John did that way back when he still had a Tdi, just can't recall ATM how much more angle he turned them ??

You can also get a (mix and match) ARP stud 'kit', at vast expense.

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