Diesel engine warm-up

[nb Innisfree]

With reference to the above, a question for those that know.

 

Is it possible that the engine is 'plumbed' wrong and the calorifier should not be supplied until the engine has reached operating temperature?

 

If the engine is 'plumbed' correctly would a missing thermostat have the same effect?

 

As far as I am aware most have the calorifier takeoff before the t/stat (comes off exhaust heat exchanger) which is why cals shouldn't be oversized. A few years ago Barrus introduced twin t/stats, one for engine and one for cal. My engine is plumbed into two cals and CH! takes a long time to warm up in winter if I don't preheat engine coolant (in that case I can divert coolant back to engine) but once working temp is reached it is able to maintain it throughout CH and cals

[tosher]

Interesting question !

 

My understanding, before I put a calorifier in, was that it should intentionally bypass the engine thermostat, so that the domestic water heats as fast as possible, without waiting for engine thermostat temperature to be reached, (and even then competing with the skin tank for the heat).

 

The rationale is similar to a car heater or van or lorry cab heater.

 

That's what I went for, so I'll admit my calorifier is slowing engine heat up from the moment the engine is started.

 

That said, the bits that companies like Calcutt and AMC supply as marinisation parts, are designed to attached to the engine so they do bypass the stat.

 

Am I killing my engine faster than before I added the calorifier ? Possibly ??

 

I'm confused !

 

 

That is correct, the pipes to the calorifier are taken off and returned before the thermostat. A 12v solenoid valve of the correct bore, fitted in the calorifier supply and controlled from a switch on the engine panel labled "Fast Warm UP" may be the answer?

[alan_fincher]

That is correct, the pipes to the calorifier are taken off and returned before the thermostat. A 12v solenoid valve of the correct bore, fitted in the calorifier supply and controlled from a switch on the engine panel labled "Fast Warm UP" may be the answer?

Thanks,

 

I'm starting to wonder now! I did what I did because that's how it generally seems to be done unless multiple stats are involved, and I received specific advice that I should go in before the stat to heat domestic water faster.

 

Your suggestion would of course cause the engine to reach stat temp faster, but rather negates the original reasons for doing what was done.

 

I'll have to have a think, although I can't say I have noticed the engine temperature gauge rising that much slower since the calorifier got added.

 

Alan

[nb Innisfree]

That is correct, the pipes to the calorifier are taken off and returned before the thermostat. A 12v solenoid valve of the correct bore, fitted in the calorifier supply and controlled from a switch on the engine panel labled "Fast Warm UP" may be the answer?

 

Before fitting solenoid valve check that water circulation round engine block won't be impeded. Sometimes calorifier takeoff can be cut into the engine by-pass hose which ensures circulation before t/stat opens, if that makes sense

[alan_fincher]

Before fitting solenoid valve check that water circulation round engine block won't be impeded. Sometimes calorifier takeoff can be cut into the engine by-pass hose which ensures circulation before t/stat opens, if that makes sense

It can't be a problem on mine, as the calorifier was recently fitted by me, and where it attaches to on the engine had previously always been a blanking plug. A valve can't possibly impede circulation more than that plug used to!

[jake_crew]

You do need to exercise some common sense .

 

If the engine won't run on load from cold, then warm it up. Otherwise just use it.

 

Ref the comment about alternators sapping power, they use just a few horsepower, so I'd be surprised if that's the explanation for poor cool pulling. More likely cold gearbox oil creating a lot of drag.

[tosher]

Before fitting solenoid valve check that water circulation round engine block won't be impeded. Sometimes calorifier takeoff can be cut into the engine by-pass hose which ensures circulation before t/stat opens, if that makes sense

 

Thanks for that, the Izusu engine manual says that if a calorifier is NOT fitted then both the take off and return pipes on the engine should be blanked off and not connected directly together so I assumed that blanking just the supply off for engine warm up would be OK.

[stuart23]

OK....I have a mitsubushi 3 cylinder...I start the engine with a bit of throttle, but to get the charging system to work ( the red charging light to go out) I have to give it virtually full throttle....On reading this, am I correct that I should wait a few minutes before doing this as by doing it straight after switching on, I'm doing some harm to the engine?

[nb Innisfree]

OK....I have a mitsubushi 3 cylinder...I start the engine with a bit of throttle, but to get the charging system to work ( the red charging light to go out) I have to give it virtually full throttle....On reading this, am I correct that I should wait a few minutes before doing this as by doing it straight after switching on, I'm doing some harm to the engine?

 

PersonallyI would give it at least 5 mins

[NB Alnwick]

Most, if not all, modern engines fitted to canal craft are based on industrial units originally designed to run 'on-load' (and often at a constant speed) from start-up. I doubt if anything would be gained by running any of these engines 'off-load' as part of a 'warm-up' procedure. If you enjoy the convenience of a modern engine then you should be able to switch it on, start it up and go . . .

[NB Alnwick]

>snipped<

 

Am I killing my engine faster than before I added the calorifier ? Possibly ??

 

I'm confused !

 

You will be able to analyse this in more detail when next you carry out a full overhaul on your engine.

I would suggest that you strip it down, regrind the crankshaft, re-profile the camshaft, re-bore the block, fit new pistons, fit a new oil pump and replace all bearings etc. in approximately twenty years time rather than leaving it for another twenty five years.

 

The petrol version of the 'B' series engine of my 42 year old MGB (which has been raced and well thrashed) needed such an overhaul in 1989 and has barely been touched since.

 

Edited to add that in my opinion we all worry far too much about such things. Most engines will easily outlast a boat's woodwork and paintwork.

Edited July 3, 2009 by NB Alnwick

[Albion]

Most, if not all, modern engines fitted to canal craft are based on industrial units originally designed to run 'on-load' (and often at a constant speed) from start-up. I doubt if anything would be gained by running any of these engines 'off-load' as part of a 'warm-up' procedure. If you enjoy the convenience of a modern engine then you should be able to switch it on, start it up and go . . .

 

Precisely. Most of us will be worn out before the engine is!

Roger

[nb Innisfree]

Most, if not all, modern engines fitted to canal craft are based on industrial units originally designed to run 'on-load' (and often at a constant speed) from start-up. I doubt if anything would be gained by running any of these engines 'off-load' as part of a 'warm-up' procedure. If you enjoy the convenience of a modern engine then you should be able to switch it on, start it up and go . . .

 

Yes, but full throttle? industrial engines like most engines are designed to be run continuously at less than max speed, generators 1500rpm, I occasionly rev my engine to max before turning off just 'stretch it a bit, but only when full temp has been reached.

[alan_fincher]

Precisely. Most of us will be worn out before the engine is!

Roger

Point largely taken.

 

But some people manage to buy boats with engines that are already 50% or 75% knackered.

 

If you do have an elderley engine in need of TLC, the same arguments don't necessarily apply as if you buy a spanking new boat with a spanking new "Mitshiyamasota".

 

Some people are happy to try and keep a slightly iffy engine going as long as they can, and not do anything that might exacerbate problems.

[Albion]

Point largely taken.

 

But some people manage to buy boats with engines that are already 50% or 75% knackered.

 

If you do have an elderley engine in need of TLC, the same arguments don't necessarily apply as if you buy a spanking new boat with a spanking new "Mitshiyamasota".

 

Some people are happy to try and keep a slightly iffy engine going as long as they can, and not do anything that might exacerbate problems.

 

Understood, but nowhere in my posts will you see where I have recommended revving the whatsits off an engine immediately after start up. All I'm saying is that there is no need for prolonged warming up. Start up, undo the ropes and set off. No matter what engine you've got, old or new, knackered or straight out of the box you won't hurt it by doing that.

Roger

[NB Alnwick]

Point largely taken.

 

But some people manage to buy boats with engines that are already 50% or 75% knackered.

 

If you do have an elderley engine in need of TLC, the same arguments don't necessarily apply as if you buy a spanking new boat with a spanking new "Mitshiyamasota".

 

Some people are happy to try and keep a slightly iffy engine going as long as they can, and not do anything that might exacerbate problems.

 

That is a very good point but if you are really worried about the state of your bores and bearings, it may be a good time to make plans for a decent overhaul. Otherwise don't worry, most vintage engines are far from being seriously stretched in the canal environment.

 

Provided you change your oil at the prescribed intervals and carry out the usual pre-start checks (for example: oil level, coolant level etc.), there is really no reason why you shouldn't start the engine and go straight off at the start of each day's cruising without need of running the engine off-load in neutral beforehand. After all, it isn't as if you are going to thrash it - unless you planning a speed record or towing a water-skier . . .

[pertamafe]

It might be worth considering the state of batteries on start up. My Alternator WILL demand 90 - 100 Amps which will pull the slow running RPM below normal 'happy' tic over. Thus if I am to make an early start from a crowded mooring it is impossible to keep RPM low & creap away with minimum disturbance. Thus an engine start with advanced RPM (sufficient to stop vibrations) whilst preparing to cast off is my best option. After the first 5 minutes the current charge has fallen to about 75/80 Amp, & oil pressure stabalised, allowing a less disturbing departure. The engine is a NANI 1.5 & this is the best answer I have discovered over 12 years. If the tic over is adjusted to compensate on start up opne is left with a high tci over for the rest of the day.

[NB Alnwick]

It might be worth considering the state of batteries on start up. My Alternator WILL demand 90 - 100 Amps which will pull the slow running RPM below normal 'happy' tic over. Thus if I am to make an early start from a crowded mooring it is impossible to keep RPM low & creap away with minimum disturbance. Thus an engine start with advanced RPM (sufficient to stop vibrations) whilst preparing to cast off is my best option. After the first 5 minutes the current charge has fallen to about 75/80 Amp, & oil pressure stabalised, allowing a less disturbing departure. The engine is a NANI 1.5 & this is the best answer I have discovered over 12 years. If the tic over is adjusted to compensate on start up opne is left with a high tci over for the rest of the day.

 

Surely the engine's governor will keep the speed constant, irrespective of load?

[nb Innisfree]

Surely the engine's governor will keep the speed constant, irrespective of load?

 

No the governor doesn't override the throttle but prevents overspeeding as a diesel is an unthrottled i.c. engine, governor meters fuel to vary engine speed, a constant speed governor can be fitted to an engine, diesel or petrol.

[Theo]

Excellent topic, this, but I think it will live more happily in "Boat building and Maintenance".

 

Nick

[NB Alnwick]

No the governor doesn't override the throttle but prevents overspeeding as a diesel is an unthrottled i.c. engine, governor meters fuel to vary engine speed, a constant speed governor can be fitted to an engine, diesel or petrol.

 

Not quite - a diesel engine is not fitted with a throttle - the flow of fuel to the injectors is controlled solely by the governor and (in marine and vehicle applications) the governor's speed settings are adjustable via a speed regulator.

 

If the speed varies for a given regulator setting, this is indicative of either: an inefficient governor, poor adjustment, or, stalling due to excessive load.

[Albion]

Not quite - a diesel engine is not fitted with a throttle

I think Innisfree meant that the inlet manifold is unthrottled on a diesel, unlike most spark ignition engines (except certain BMW spark ignition engines where they were experimenting with variable valve lift via high speed solenoids to throttle the intake and eliminate pumping losses....back when I was in Rover Car engine management development)

 

- the flow of fuel to the injectors is controlled solely by the governor and (in marine and vehicle applications) the governor's speed settings are adjustable via a speed regulator.

Agreed. On my Gardner 4LK the throttle set the required speed and the governor maintains that set engine speed if it is possible to do so considering other factors such as load etc

 

snipped

Roger

[nb Innisfree]

Not quite - a diesel engine is not fitted with a throttle - the flow of fuel to the injectors is controlled solely by the governor and (in marine and vehicle applications) the governor's speed settings are adjustable via a speed regulator.

 

If the speed varies for a given regulator setting, this is indicative of either: an inefficient governor, poor adjustment, or, stalling due to excessive load.

 

Yes as I said a diesel is an unthrottled i.c. engine i.e, no throttle, part of the reason why petrol engines can close the economy gap with diesell on a fast run, the petrol flat out is unthrottled. If you have a fixed throtte setting on diesel and the load increases then rpm will decrease, or vica versa, same as petrol. Having said all that I have worked on a throttled diesel, a tractor. We had removed butterfly assembly and then turned the engine to adjust valves, having no throttle it went to full revs, big panic scrabbling for the fuel pump stop lever!

[MoominPapa]

Not quite - a diesel engine is not fitted with a throttle - the flow of fuel to the injectors is controlled solely by the governor and (in marine and vehicle applications) the governor's speed settings are adjustable via a speed regulator.

 

If the speed varies for a given regulator setting, this is indicative of either: an inefficient governor, poor adjustment, or, stalling due to excessive load.

Modern engines may be more subtle, but on the FR the governor is not sophisticated enough to keep the engine speed completely stable with changes is load.

 

It consists of a pair is centrifugal weights pulling on a spring and the other end of the spring is held in a position which corresponds to the speed regulator setting. The fuel flow is controlled by the position of the weights which depends only on the speed of the engine and the position of the speed regulator.

 

Assume that the engine is at a stable speed and load: now increase the load. The speed will drop and the spring will pull the fuel rack in the direction of more fuel flow. The engine will speed up, but it can't ever get back to exactly the same speed with the new load, because the fuel flow depends only on speed and regulator setting. If the engine reached the original speed it would be running with the original fuel flow: impossible with a heavier load.

 

In control-theory terms, I believe that the control loop doesn't have enough gain for completely stable speed control. It's easily good enough for a marine engine, so why worry?

 

MP.

[Albion]

snipped

Having said all that I have worked on a throttled diesel, a tractor. We had removed butterfly assembly and then turned the engine to adjust valves, having no throttle it went to full revs, big panic scrabbling for the fuel pump stop lever!

 

Ah, a diesel runaway, always focuses the mind and necessitates a change of underwear

The only throttled diesel that I can recall, but I stand to be corrected, was the early Sherpa van with the BMC 1.8 where they throttled the inlet manifold to develop vacuum for the brake booster IIRC. I seem to remember something in the manual for the engine about the adjustment that had to be made to synchronise the engine accelerator linkage with the 'inlet throttle?' butterfly setting.

Roger