why do........?

[bad boy]

why do diesels have iron blocks? possibly one of their biggest disadvantages the weight of them could be solved by having aluninium blocks or steel, is their a technical reason why they dont?

[Alien]

Extremely high compression ratio results in a lot of stress on the block/crank/pistons/rods. Diesels would have to be heavier than spark ignition engines even if they were to be aluminum.

[JakeR]

And why do they all sound so crappy too?

[RichardD]

The noise is to identify and embarass people who have diesel cars. Although some such people who skimp on an everyday car do it to save important ££££ to also run something fibreglass and noisy (a nice sporty noisy that is!) on a weekend.

On this topic, is the the reason the skyline engine is an iron block is to handle the massive boost pressures reliably when they are tuned?

>> Edited by RichardD on Monday 10th November 15:23

[Fatboy]

RichardD said:

On this topic, is the the reason the skyline engine is an iron block is to handle the massive boost pressures reliably when they are tuned?

The Skyline's ability to take ridiculous amounts of boost came as the result of the engineers accidentally factoring in too much tolerance for the block strength, which some tuners discovered, hence the huge boosts they can achieve. IIRC

Then again the Supra twin turbo 6 can take huge boost as well, so it might have been either an oversetimation on both companies parts, or just for safety's sake, as those blocks were going to be used for the Japanese touring series, where expiring engines would not be good

[Pigeon]

JakeR: Diesel rattle on tickover is caused by the extremely rapid pressure rise you get at the onset of combustion in a diesel, occurring over a very small angular fraction of the cycle. It's a little bit like pinking except that it's not a fault condition and the engine just has to be built to take it. It can be reduced by more complex injection systems at the expense of reliability.

[edc]

I have a friend in Thailand with a Skyline which puts out a reputed 800bhp. It runs circa 700bhp because of losses due to climate. The only thing standard in the engine is just the block; turbo on boost at 5k rpm, 10k rpm limit. He's now over here pootling about in a Audi A4 Avant 1.8T.