At what RPM Do You Start a Diesel ?

[SvenG]

Originally Posted by Jesse

the concept of drawing raw flames through the air intake to start a cold diesel is as frightening as it is effective.

Is that really what it does ?

I assumed it just electrically heated the air intake. Wasn't aware that there is combustion in the air intake !?



-Sven

[Seahunter]

I accept there are a number Perkins out there with HS, most of them were added post installation. Because the marine version does not have a filtered or fire suppressed breather, just a screened intake their use can be quite dangerous and can actually cause the engine to momentarily to run backwards on engines with a dry exhaust, as pre-ignition back-firing does not usually happen on diesel engines. An open flame in my engine compartment doesn't thrill me either.

[Seahunter]

Originally Posted by goboatingnow

Sorry. I was looking at a mobo with two Perkins recently , funny the keys had HS for heat start. Perkins used the same engines everywhere in many forms with a couple of different heat start systems

Secondly you didn't read the " starting the engine " section. You read the " cold start " section regarding preheaters etc.

Lastly please don't be rude. You 'are quite mistaken in your views.

It's worth noting that many simplified marine manuals often recommended idle throttle starting purely as a safety as too many users misinterpreted the manuals and engaged the gearbox with some consequences. However the fact remains from a design perspective diesels like full fuel flow starts

Anyways I point you to my original reply to the OPs specific situation.

Dave

I have read and instruct on the Perkins manuals. Offering your opinion doesn't make it the right answer. Starting a diesel at more than an idle if it's been sitting for more than a week will put more wear on it than running it at full throttle more than 8 hours straight. Furthermore the manual is quite clear, the workshop manual is even clearer, please give it a read.
To squarepeg, read the manual, not all diesels were created equal.

[Tranquilo]

After my 4-108 rebuild in 2002, bleeding the fuel system requires to start at WOT. After a few, failed first attempts, I ran an errand leaving the mechanic by himself. While I was gone, he managed to start up the engine from the engine room but I had left the throttle lever above at WOT. The engine fired up to full revs with everything new inside. Seconds that seemed like minutes passed until he could get out of the engine room, up on deck and to the steering pedestal to throttle back. I was very worried by this. Now almost 10 year later, never had a problem. I start up at 600RPM and wait till oil pressure comes up and go to 900 to reduce vibration. I use the engine almost on daily basis and on longer layups, I start with fuel shut of deployed a few seconds to lubricate before letting her fire up. I have a big ass Volvo cooler (donation from the same mechanic, as the Bower replacement was very $$$) and run a cool engine for almost 5 years now. Had the head off a couple of times and from the top everything looks fine. No smoke, no headaches same injectors since before Moses parted the sea and have not been pulled or serviced in all of that time. Funny knock in my drive train lately but that's another story.
I'm running my fathers old 4-108 and I won't replace it for nothing in the world!
Diesel Engines: Not Your Father's 4-108 | Cruising World

[lancelot9898]

I have a Perkins 4-108 (1985 vintage) that over the past 25 years I start at idle rpm which is around 600. There are occasions during the colder months where I've given more throtle to start, but once started I back off to idle until warmed up which usually takes 10 minutes or more. One other note about rpm. My tach is completely out of calibration and several years ago I borrowed a friend's photo tach to calibrate. Not sure if the Balmar alternator and external regulator that I installed about 15 years ago is the cause or if it's always been off from day one. Here are the numbers FWIW.

Tach Reading Actual rpm

420 620
1000 830
1500 1120
2000 1500
2500 1890
2600 1954
3000 2267
4000 3000 est

[meyermm]

Originally Posted by David M

With a turbo diesel that is very true according to Cummins, but for a different reason. Turbines spin down pretty quick and are always spinning so long as there is exhaust flowing through them. What you do not want is for a hot turbine to burn the oil that lubricates it's bearings. A turbine needs a few minutes to cool before shutting down the engine.

Correct that is the real reason.
Turbine is hot and once engine stops oil stops flowing allowing it to heat up and turn to ash in extreme cases, unlikely on small marine diesel but a good practice just the same.

[meyermm]

Reading this thread it amazes me how much can be written about so little. I am sure others in the trade will be enjoying the banter as well. Talk about over complicating a subject wow. Its an internal combustion engine with pistons, valves, camshaft etc etc.
Diesel engines are high compression so loads on bearings are high, so high RPM at start up is not what I would recommend. Why, it takes more fuel to produce that RPM hence higher loads, oil is not warm & flowing fully through the engine, on some it will drain back to the sump since last start up. The most engine wear in a petrol or diesel engine occurs during cold running that is why we have thermostats to attain and maintain temperature.
Run the engine at enough REVS for it to run smoothly until it sees a little temperature. (you will know as it will tell you it is happy) Use enough throttle for it to start easily in the environment your in.
Do not believe everything that is written in a workshop manual, it is a guide in some areas and the bible in others (pump timing, tappet clearances, bearings etc) Some of those books were written a long time ago and if they were rewritten today would be heavily amended.
The above applies to all engines some of you get too hung up on particular makes and models. Just because something has worked for you does not mean it is best practice. Many people smoke and die from related disease some never have any bad health but what is best practice to smoke or not???

[Blue Stocking]

Deja vu--all over again.

[Sailmonkey]

I always start at zero, to do anything else is really hard on the starter

[meyermm]

Originally Posted by Sailmonkey

I always start at zero, to do anything else is really hard on the starter

No your not synchronizing the insertion of the pinion gear with the ring gear at the precise time. Keep practicing

[goboatingnow]

Originally Posted by Seahunter

I have read and instruct on the Perkins manuals. Offering your opinion doesn't make it the right answer. Starting a diesel at more than an idle if it's been sitting for more than a week will put more wear on it than running it at full throttle more than 8 hours straight. Furthermore the manual is quite clear, the workshop manual is even clearer, please give it a read.
To squarepeg, read the manual, not all diesels were created equal.

You've obviously never instructed on Perkins based generators them.

Nobody is suggesting a continous full throttle start. It's open throttle then back down on firing same system used on many Perkins based tractors.

Ps the heat system were often supplied by Perkins to marine builders and left on. Perkins themselves never to my knowledge built a marine version of any engine.

Dave

Face.

[SvenG]

Originally Posted by goboatingnow

Perkins themselves never to my knowledge built a marine version of any engine.

From the Perkins web pages regarding marine support: "The Wimborne Marine Power Centre manages all aspects of the Perkins marine engine business."

The above doesn't prove that Perkins built a separate marine version but the Perkins manuals also refer to the marine versions with language which implies that the marine versions were different.



-Sven

[Seahunter]

Originally Posted by goboatingnow

Ps the heat system were often supplied by Perkins to marine builders and left on. Perkins themselves never to my knowledge built a marine version of any engine.

Dave

Face.

Most of the 4 Series engines were modified utility engines, that WAS my point. However they did support recreational marine conversions as they did in fact built larger commercial marine engines. Most of the 4 series engines were shipped out by Perkins without the heater assembly and they recommended NOT to install it as there was NO flame arrester. In fact the 4-236 (the big brother of the 4-108) was and still is the most reliable, naturally aspirated, fuel efficient marine diesel ever built. This is why CAT bought out Perkins a number of years back as Perkins would not sell them the patent rights to reproduce the 4-236 in the USA. Cat uses the newly named "4.4" (originally designated the 4-236) for their marine genset series as well as a commercial utility engine. As many 4 series engine owners have found, CAT has discontinued many of the parts for these engines. CAT still manages Perkins-Sabre which operates as a stand alone company with CAT worldwide support. Perkins-Sabre still builds the "236" as the M92B.
You might want to check these pages out then. Perkins Sabre Marine Diesel Engines
Perkins Sabre M92B - Description - Marine Diesel Engine for Leisure Craft and Commercial Craft Applications

[Mark Zarley]

In the genset motor dept. I sure wish mine had a manuel throttle so on start-up it would run in the 800 rpm range instead of a constant 1800. Let it warm up as usual and before switching it "on" set the manuel throttle wide open at it's governed speed. Because of the "manuel" effort I would visit my genset on a better schedule and I am sure I would be rewarded with longer engine life

[Therapy]

Originally Posted by meyermm

Reading this thread it amazes me how much can be written about so little. I am sure others in the trade will be enjoying the banter as well. Talk about over complicating a subject wow. Its an internal combustion engine with pistons, valves, camshaft etc etc.
Diesel engines are high compression so loads on bearings are high, so high RPM at start up is not what I would recommend. Why, it takes more fuel to produce that RPM hence higher loads, oil is not warm & flowing fully through the engine, on some it will drain back to the sump since last start up. The most engine wear in a petrol or diesel engine occurs during cold running that is why we have thermostats to attain and maintain temperature.
Run the engine at enough REVS for it to run smoothly until it sees a little temperature. (you will know as it will tell you it is happy) Use enough throttle for it to start easily in the environment your in.
Do not believe everything that is written in a workshop manual, it is a guide in some areas and the bible in others (pump timing, tappet clearances, bearings etc) Some of those books were written a long time ago and if they were rewritten today would be heavily amended.
The above applies to all engines some of you get too hung up on particular makes and models. Just because something has worked for you does not mean it is best practice. Many people smoke and die from related disease some never have any bad health but what is best practice to smoke or not???

I'll keep smoking..............

Oh yea.

I have a Westerbeke 30 B three and if I don't open the throttle a little it starts just fine but shakes like all hell for a couple of seconds which makes me think I will wear out mounts and alignment pretty quick.

So I start it and then drop the throttle immediately and it sounds happy.

I am happy.

Do you guys think I will stay that way?