Warning for GTB owners...

[sepulchrave]

Very long duration for bigger nozzles isn't it. The duration I'm running on kevs is very close to stock pd150.

The original 215bhp limit for stock nozzles came from the theory of EOI being around 7 degrees ATDC. People said running past this will result in increased smoke and EGT. This theory I believe is wrong as you still make power past 7 degrees without EGT increases. EGT increases when your not burning the fuel.

 

EGT increases because there is still enough oxygen left in the end gases for any fuel not burnt during combustion to continue burning as it exits the cylinder and enters the turbo, this is why EGR can reduce EGT because it adds inert gas in place of some of the oxygen.

No diesel engine uses all its oxygen, they all run in a lean condition when compared to petrol engines because there isn't time for the flame front to spread into the space vacated by the piston as it moves down due to the bulk of combustion happening in that little bowl.

[faboka vrs]

Because BHP is directly proportional to boost,

 

Assuming you keep the same AFR. If you only increase boost without fuel then their will be very little in terms of BHP difference.

 

Diesel mappers don't all map to the same AFR, some don't even bother about AFR. So one mapper might run 2bar with AFR X. Another might run 1.8bar with AFR Y. But both having the same BHP but the latter having more smoke.

 

Silky prefers his to run richer with less boost.

[sepulchrave]

Assuming you keep the same AFR. If you only increase boost without fuel then their will be very little in terms of BHP difference.

 

Diesel mappers don't all map to the same AFR, some don't even bother about AFR. So one mapper might run 2bar with AFR X. Another might run 1.8bar with AFR Y. But both having the same BHP but the latter having more smoke.

 

Silky prefers his to run richer with less boost.

 

You missed the bit where I said it was just a guideline. Look, I know there are a lot of assumptions here, but most of them are made in the interest of keeping things simple and understandable and boost is the dominant factor in getting moar powah.

Silky probably understands the trade off between running higher boost and risking bursting the engine and running higher EGT but risking cooking the VNT mechanism.

However some of the boys that come on here really aren't too bright and discounting the possibility that they just give the missus a slap when she complains about how much they're spending on a ten-year old oil burner, they spend money like water chasing headline power figures.

So I'm just trying to explain my reasoning simply for the benefit of all concerned.

[Lofty]

You are a judgmental old bugger! What gives you the right to liken members of this site to domestic abusers to prove one of your know it all points?

Pathetic thing to say for a supposedly clever bloke

Edited 19 February, 2016 by Lofty

[coskev]

I'm thinking  cuprinoldave has not masterbated for a while ........

 

Go on,it is the weekend

[sepulchrave]

You are a judgmental old bugger! What gives you the right to liken members of this site to domestic abusers to prove one of your know it all points?

Pathetic thing to say for a supposedly clever bloke

 

It was supposed to be funny, put your teeth back in.

[Lofty]

Knocking women about funny???

Never mind my teeth my entire liver fell out I laughed so hard... I am genuinely staggered at how you can pigeon hole members of the forum as "not bright".

Not many things boil my **** these days, I'm far too old for that but your way of belittling people is genuinely annoying.

The thread is a decent one about pushing the boundaries, yet you seem to be content in being all old school Etonian head master with your "amusing" comments.

[sepulchrave]

If you read more closely you'll see I was discounting the possibility of domestic abuse by our esteemed forum members, as to 'brightness' I speak as I find, if someone can barely read or write and has absolutely no idea what they're doing then it's reasonably safe to assume they shouldn't be trusted with a pair of sharp scissors.  :sun:

[Stuart27183]

This is starting to get far too serious for me! What has happened cannot be changed now unless you are david blaine, so good luck to both guys with cracked pistons on getting back on the road again. I personally dont give two hoots what my bhp is, all i care about is that im running around 2bar until i get my injectors then can wind it up a bit and get the most from my turbo, whilst maintaining driveability and reliability.

[faboka vrs]

https://www.savvyanalysis.com/articles/understanding-cht-and-egt

Good read about how to use cylinder head temp to monitor what's happening inside the engine

[faboka vrs]

http://www.innovatemotorsports.com/resources/myths.php

And another about cylinder pressure and timing.

[alex_e3]

[felicia16v]

What difference do the later pd pistons have ? I was thinking about the ones designed for the dpf and the hotter temperatures involved when that's having a regen and if they are coated or anything?

[alex_e3]

Not too sure on this personally. However, I plan on getting the new BKD pistons I buy next month ceramic coated. Will give better thermal protection and increased fatigue life.

[alex_e3]

For those who haven't seen my project thread, I stripped my engine fully yesterday. This is the damage to the piston...

 

 

 

 

 

 

The brass insert has been rotated round. The bore is also scored. Underside of the piston has since cracked through as well.

 

 

Rest of the engine is in fantastic condition I might add! You really wouldn't think it had covered 135k miles.

Edited 22 February, 2016 by alex_e3

[vrs180]

Perhaps a good quality/efficient oil cooler would help prevent piston failure.

Not only can effective oil cooling reduce piston crown temperatures (ideally no more than 600 degrees F) but it will also reduce combustion temperature and EGT.

[alex_e3]

I've run the car with an oil cooler.

 

Plus I have an oil temperature gauge fitted, and the temperature rarely rises above 90 degrees.

[felicia16v]

Does that chip in the bowl go thru to the hole above the gudgeon pin? It almost looks melted above the bush.

[sepulchrave]

It does look like the little end has seized, is the gudgeon pin heavily blued from overheating?

[alex_e3]

Yeah, chip goes all the way through.

I can't see any evidence of overheating. Just looks like a brittle fracture. Although the score on the bore would be in line with the thought of a seizure...

Sent from my D5503 using Tapatalk

[Southy]

Alex has the score on the bore been caused by the bronze bush where the wrist pin sits rotating due to becoming loose once the piston has cracked? This is what has happened with mine, you could see the edge of the bronze bush had started to wear where it had rubbed on the cylinder wall

[felicia16v]

The score is surely from the side of the piston where it's broken away ?

[chris-H]

With relation to scoring with the pressures and temperatures involved, the hardness of the different metals has to be considered. Ie more likely broken piston than bronze bush.

[PoloTom]

Just to add my 2p. Polo with 2260 etc @ 280bhp.

 

My first engine cracked 2 pistons in 4k.

 

Second engine cracked 1 piston in 3k.

 

Third engine - added an oil cooler.. No problems @ 6k. 

[hutchysrs50]

Alex has an additional oil cooler fitted though.

Although I'm sure it helps