Anyone know about mahoosive diesel engines?

[MrPeters]

I have a question about train / bus diesel engines. I believe the engines in question are Cummins lumps - but can't be sure. Oh yes, I have asked on a railway forum but non of them seemed to have one iota of technical intelligence.

The trains I'm interested in are Class 185's (FTPE). Now after a few years of having them round these parts they idle somewhat suspiciously. The best way of describing this is like "vroooom.....vrooooom.....vroooom" etc... some of the units almost stalling in between the 'vroooooms!'. At first I assumed this was down to needed maintenance as I can remember early 90s buses doing similar when they got a bit (lot) leggy.

I was talking to someone who had been told by a mate of someone who might once have been a train that it was actually the ECU deciding not to inject diesel into one cylinder at a time, and it would cycle round each cylinder in turn.

Why? What would be the reason for this?

Fanx.

[crmcatee]

Logically and knowing nothing about big diesels. Why inject diesel and waste it when it's idling when the engine will continue run (albeit lumpy) on say a 1/4 of the fuel needed to idle when injecting all cylinders.

Seems common sense really - especially if you don't care about the noise it makes.

[cheesyblob]

MrPeters said:

I was talking to someone who had been told by a mate of someone who might once have been a train

Really?

[MrPeters]

cheesyblob said:

MrPeters said:

I was talking to someone who had been told by a mate of someone who might once have been a train

Really?

Yes.

[danyeates]

cheesyblob said:

MrPeters said:

I was talking to someone who had been told by a mate of someone who might once have been a train

Really?

Quote of the day!

[thinfourth2]

Train engines ain't massive they are quite small on the massive engine scale.

Big engines are bigger then your house

[curlie467]

I met a girl once, she used to be the village bike.

[smele]

I know Deltic Diesels can hunt when cold, the oil is thick in the mechanical governor thus causing the engine rpm's to hunt up and down. Can sound interesting with the turbos whistling as well.

[curlie467]

Yep, more likely the governor than the injectors etc

[MotorsportTom]

Slightly off topic but the words mahooosive and diesel made me think of this;

http://www.techeblog.com/index.php/tech-gadget/wor...

I'm not an expert but that's a LOT of torque!

Edited by MotorsportTom on Thursday 13th January 16:49

[Zad]

Not really optimal for powering trains though

Googling found another quote from the Railway Gazette: "An automatic shutdown feature for use at depots and stabling points has been introduced, as TPE Engineering Director Nick Donovan acknowledges that the QSK19 power unit 'does not like idling'.

http://www.venturemagazine.co.uk/article-page.php?...

19 litre, 650-750hp. I guess they are going for longevity then.

[F i F]

bit difficult to answer based on a vrrooom vrrooom but isn't this just the old mechanical governor which switched fuel supply on and off based on a particular rev range when idling?

Or is it different from that?

[matchmaker]

Zad said:

Not really optimal for powering trains though

Googling found another quote from the Railway Gazette: "An automatic shutdown feature for use at depots and stabling points has been introduced, as TPE Engineering Director Nick Donovan acknowledges that the QSK19 power unit 'does not like idling'.

http://www.venturemagazine.co.uk/article-page.php?...

19 litre, 650-750hp. I guess they are going for longevity then.

Highish state of tune for a railway engine! Look at an English Electric 16CSVT. 247 litre V16. 2700 bhp.

[stinkysteve]

Is it not something to do with the demand going up and down as major systems (i'm thinking predominantly teh compressor) cuts in and out?

I know the Class 43 engines (Intercity 125 HST power car) have recently been upgraded to drop a bank on idle in stations. That's why KX is a lot less smokey that it used to be.

[MrPeters]

HellDiver said:

They're English Electric engines, and the governor is controlled by oil pressure, which is obviously low at idle. They're usually nicknamed "thumpers".

They're used by the older trains here in N. Ireland. Over here the trains they're used in is the NIR Class 450 DMU (not the same as the BR Class 450). Commonly used in the BR Class 201 on the mainland.

http://en.wikipedia.org/wiki/English_Electric_dies...

I'm not on about thumper engines.

http://en.wikipedia.org/wiki/British_Rail_Class_18...

[HellDiver]

Class 185 use a Cummins QSK19 engine.

[MrPeters]

HellDiver said:

Class 185 use a Cummins QSK19 engine.

I know!

[anonymous-user]

There would be some fuel economy benefits on a diesel engine at idle if you "round robin'd" the cylinders and hence avoided running at very low loads (where a lot of heat is lost to the combustion chamber surface, and hence the engine is very inefficient). But i suspect given the lack of sophistication of these engines (and their age) this is unlikely to be a deliberate strategy. Much more likely to be the mechanical speed controller response frequency (i.e. not fast enough to catch (trim) indivudual cylinders, so system overshoots and next cylinder gets a big fuel reduction, then undershoots etc etc)

[HellDiver]

MrPeters said:

I'm not on about thumper engines.

I know, I realised that after I'd posted.

Edited by HellDiver on Thursday 13th January 17:38

[matchmaker]

stinkysteve said:

Is it not something to do with the demand going up and down as major systems (i'm thinking predominantly teh compressor) cuts in and out?

I know the Class 43 engines (Intercity 125 HST power car) have recently been upgraded to drop a bank on idle in stations. That's why KX is a lot less smokey that it used to be.

The lack of smoke is more down to re-engining - the lovely Paxman Valentas have been replaced by MTU engines which are a lot cleaner.