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Historical engine - which engine gauges and why?


dpaws
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Just now, Mike the Boilerman said:

And a diesel HAS to have no throttle because it is a 'compression ignition ' engine. If the air intake was throttled back the the compression pressure would fall leading to lower compression temperature and no bang. 

I must take a picture of the butterfly on the intake of the BMC 2.2 diesel in the workshop

Richard

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4 minutes ago, RLWP said:

Which leads you to think about a petrol engine, where the amount of air on part throttle is limited. Where a diesel is a constant compression engine (give or take flow losses at speed), a petrol engine is a variable compression machine. At part throttle it starts with a cylinder full of mixture below atmospheric pressure

Note: compression, not compression ratio - that's a function of geometry

Richard

This also explains why older diesels vibrated so much on tickover, they are still compressing a full cylinder of air so have some of the vibrations associated with an engine running flat out. Really clever modern engine mount designs have reduced this in recent years.

The throttled cycle of the petrol engine wastes fuel with the resulting pumping loss, dragging in air past the closed throttle, like trying to work a bicycle pump with your thumb over the end. This is why diesels do so much better in slow urban driving.

............Dave

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1 minute ago, RLWP said:

I must take a picture of the butterfly on the intake of the BMC 2.2 diesel in the workshop

Richard

What does it do and what era is that engine? I was involved in a project years ago investigating throttling to reduce vibration at idle but it never went anywhere, pretty daft idea really.

...........Dave

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1 minute ago, dmr said:

This also explains why older diesels vibrated so much on tickover, they are still compressing a full cylinder of air so have some of the vibrations associated with an engine running flat out. Really clever modern engine mount designs have reduced this in recent years.

The throttled cycle of the petrol engine wastes fuel with the resulting pumping loss, dragging in air past the closed throttle, like trying to work a bicycle pump with your thumb over the end. This is why diesels do so much better in slow urban driving.

............Dave

What I find interesting is, if you set out to design a variable compression engine, I'm not sure something as simple as a butterfly in the inlet would be the obvious place to start. I can imagine all sorts of variable stroke machines that wouldn't do the job anywhere near as well

Richard

Just now, dmr said:

What does it do and what era is that engine? I was involved in a project years ago investigating throttling to reduce vibration at idle but it never went anywhere, pretty daft idea really.

...........Dave

1960s, it's part of the fuel system. From memory it uses the vacuum to power a diaphragm on the pump to move the rack

What we need is a BMC 2.2 or 2.5 manual

Richard

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33 minutes ago, Mike the Boilerman said:

No.

the diesel has no throttle. Engine speed is controlled by the amount of fuel injected on each compression stroke.

 

 

Ah of course, having installed hundreds of the things I knew that. Must be senile premature dementia setting in :mellow:

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29 minutes ago, john6767 said:

Anyone remember the windscreen wipers that worked on vacuum, when you put your foot down they stopped!

Ford Angla/Prefect 100E had this feature. Not Ford's greatest contribution to road safety, the faster you went the slower the wipers went.

Edited by cuthound
To unmangle the effects of autocorrect.
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7 minutes ago, cuthound said:

Ford Angla/Prefect 100E had this feature. Not Ford's greatest contribution to road safety, the faster you went the slower the wipers went.

'Faster' was kind of relative. I remember overtaking an old Hants and Dorset double decker in a ford popular, in the rain, unable to see sod all and after being on the wrong side of the road for about 1/4 mile I still hadn't reached the front wheels of the bus. Kids in Vauxhall Corsas these days, tearing round like Fangio, don't know they're born. Grumble grumble. Had to decoke the blasted thing every other week as well.

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31 minutes ago, Bee said:

'Faster' was kind of relative. I remember overtaking an old Hants and Dorset double decker in a ford popular, in the rain, unable to see sod all and after being on the wrong side of the road for about 1/4 mile I still hadn't reached the front wheels of the bus. Kids in Vauxhall Corsas these days, tearing round like Fangio, don't know they're born. Grumble grumble. Had to decoke the blasted thing every other week as well.

Brings back memories.......and you had to master the choke lever after starting the engine from cold or else it would cut out as you pulled away at a junction. (Vauxhall Victor and BMC's) I agree about kid's to-day, try explaining to my wife's offspring that you have to warm up a 30/40 year old B&S, Villiers or JAP engine before cutting the grass..

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1 hour ago, RLWP said:

Maybe Im having a thick day, but I cant find page 66, section A goes up to A43 (I think) then section B starts at B1.

Using the pdf page counter gives section C8 about the fuel filter??

but I can see the throttle plate in the cross sectional picture at the start of the manual.

...............Dave

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16 minutes ago, dmr said:

Maybe Im having a thick day, but I cant find page 66, section A goes up to A43 (I think) then section B starts at B1.

Using the pdf page counter gives section C8 about the fuel filter??

but I can see the throttle plate in the cross sectional picture at the start of the manual.

...............Dave

It's page 66 of the PDF, section C, just above C1

Richard

 

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32 minutes ago, RLWP said:

It's page 66 of the PDF, section C, just above C1

Richard

 

Well how interesting. Maybe this engine was a designed by a bloke who only understood petrol engines :D  why not just connect the accelerator directly to the injection pump?. I suspect its a driveability thing, the injection pump maybe did not provide the correct characteristics as was possibly not intended for road vehicles, using a venturi gives a fuel demand  based upon both engine speed and accelerator position.

...............Dave 

or looking at it another way, its not really a throttle but the vane of an air mass flowmeter with users foot adjustable sensitivity.

..............Dave

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On 10/6/2017 at 18:46, Athy said:

For fuel and water testing I use a garden cane. The clean end dips into the water tank, the darker end dips into the diesel. Seems to work, as we have not yet run out of either..

It does make me wonder, though, why don't boats have water and fuel gauges? I don't think I have ever seen either on a n/b.

"Cor" that"s a recipe for oily tasting water, & having to drain the fuel filter down at frequent intervals  Extra things to fail at awkward times & out of the way places :D

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22 hours ago, dpaws said:

Yes, it's that warning system that I'm after... I think the engine room gauges are useful once the alarm has sounded so you can analyse the issue after an engine restart etc. Previously I've found a tacho useful to indicate the possibility prop fouling, but nothing more. The roof mounted oil pressure gauge reading seems to be proportionate to rpm and so substitutes in a way, and it seems is much easier to install. 

You don't need a tacho to know your props fouled Smoke from the exhaust & the engine laboring are better than any tacho When youv'e got to know the foibles of your engine you will probably be able to tell if you have bread bag on your prop

Edited by X Alan W
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8 hours ago, koukouvagia said:

Now if you had a Kelvin all you'd need would be 

A sense of touch (the cylinders should be "as hot as a man's hand can bear");

Keen eyesight (there is no oil pressure you just have to make sure the reservoirs are full and the dipstick is at the correct mark before starting out);

Good hearing (keep listening for the splashing sound to show that the Rae water pump is working);

A sense of smell (to detect anything overheating).

 I would guess the same gauges would have been OK for the "Seffle as well I had similar ones fitted in my "Seffle" days+ a green light for the glow plug heater & a BAr pressure gauge on the air start bottle O my all these mod cons

 

 

 

 

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15 minutes ago, dmr said:

Well how interesting. Maybe this engine was a designed by a bloke who only understood petrol engines :D  why not just connect the accelerator directly to the injection pump?. I suspect its a driveability thing, the injection pump maybe did not provide the correct characteristics as was possibly not intended for road vehicles, using a venturi gives a fuel demand  based upon both engine speed and accelerator position.

...............Dave 

or looking at it another way, its not really a throttle but the vane of an air mass flowmeter with users foot adjustable sensitivity.

..............Dave

In fact, it's probably a bit cleverer than that. It uses the vacuum in the inlet manifold as a governor. If the engine speeds up, it will make more vacuum and shut down the pump - and vice versa. So you don't need a centrifugal governor in addition to an expensive injection pump

And I control the speed of my boat with a lever, operated with my hand - and often my leg - never my foot!

:P

Richard

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4 hours ago, dpaws said:

Ahhh but there are many ways to resolve the issue. I had a problem with no stopping power with a JP3 and Blackstone gearbox, finally identified by a genius on here as being worn reverse cones - apparently the gear box has two clutches, one for each direction and my reversing clutch was slipping! 

I've now got a PRM500 hydraulic box fitted so the issue will never arise again, but if I had had a propshaft tacho fitted then I'd likely have sussed the issue myself.

I'm now investigating bi-rotational propshaft tachos :) My engine's max rated RPM is 1500 but the day to day limit is 1200. The PRM's reduction ratio is 2:1 so I can fit a 600-0-600 tacho (no issue with over-speeding the gauge, physical limit is 1350). A couple of examples are below; common instruments on big ships of course, absolute unquestionable overkill on a narrowboat but don't worry, if you're not tempted by the $36000 asking price for the Pan Delta system then a little bike computer with a magnetic cadence sensor should do the same job for £20...

It means I don't need to find a cream-faced low-rev engine tacho - though they do exist with mechanical drive if you google carefully... the one below is a little 3" unit made in Japan for a Yanmar LD engine: 

8502-9004.jpg

 

 

 

 

 

image.png

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You shouldn't require all that fancy kit just look over the side when the box is in "backards" & see how much swill is coming from under the counter that will give you an idea how much/fast the blade is revolving

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My spitfire in 1984 had all the instruments oil pressure voltmeter vacuum gauge.

they were very useful one morning when I got in at the swan and bottle at Uxbridge. The oil coursing onto my foot from the cut pipe and the Sparks from the wires indicated that yes indeed someone had broken in and stolen them. The halfrauds moss alarm of course had ignored the whole lot as they were stealing the instruments not the car...

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3 hours ago, LEO said:

Brings back memories.......and you had to master the choke lever after starting the engine from cold or else it would cut out as you pulled away at a junction. (Vauxhall Victor and BMC's) I agree about kid's to-day, try explaining to my wife's offspring that you have to warm up a 30/40 year old B&S, Villiers or JAP engine before cutting the grass..

My Austin 7 had a manual choke and on the steering wheel a lever to advance and retard the ignition.

Try explaining that to kids today. 

:)

austin-7_9939.jpg

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