Injector Selection for DD4-71 ranges from N35 to N90- Anybody insight?

[Meander]

Hi Trawler community - new here - just bought a Gladding Hearn Pilot steel hulled lets call it trawler technically would say its a DownEaster but nice displacement none the less - single engined with an awesome DD 4-71N Twindisc combo.


I try to get to know the systems and hands on spare parts - optimize what ever is possible for long range.


So here my question out to you:
the injector range that is compatible seems to go from 35 to 90 and I assume its the amount or a number correlating to that is injected into cylinder?
What are your experiences know how if I may tap into that?
Can efficiency be increased by putting smaller once in - is there associated risk to consider etc.


thank ya all in advance!!!!

 

[Lepke]

You need the correct injector for the power range you want to use. A slightly smaller injector will cause the governor to open the injector more and you won't reach full power. A larger injector will be closed more. In the end your governor has less control.

I've been burning diesel since the 1950s and the fuel we have today is crap. It has less lubrication, doesn't combust as well, and doesn't do a good job of keeping the fuel system clean. But a lot of people in the EPA that never had a real job are happy.

The best way to get economy out of a Detroit is have it in good mechanical repair. Make sure governor and valve adjustments are correct. Get a temperature gun and see what each exhaust port is registering at cruising rpm. They should be close. Very slight adjustments to the valve lash can balance the cylinders. Be careful. Also use a good diesel additive. One that improves combustion. I use Archoil 6200 and see a gain above 6% better mileage. It also improves lubrication of the fuel system, kill organisms, and cleans the tanks. Along with that I use Archoil 9100 oil additive that reduces friction. (archoil.com)
If you like to build things, make a hydrogen generator. I've been using them for years and get about a 20% improvement in gas and diesel. If you do, then you can use a 1 size smaller injector.
I have twin IL 671s naturals and at 1800 (max continuous) burn about 4.3gl/hr each with n65 injectors. Before overhaul, no additives, they burned 7+. Nice thing about Detroits, the sleeves are numbered and you can buy the same the factory used. Because of machining, each cylinder can be slightly different, but made the same with the sleeves.

 

[Meander]

Thanks for elaborate message!!! Really appreciated


I will look into fuel additives for sure - the dual racors need regular filter changes.
Fuel is an overloked factor in the whole power system I agree - I looked into fuel polish systems and except for all the more and better filters there was a strong magnetic component where fuel goes through and the molecules get for lack of more scientific terms - aligned for better power whila also killing algae?? Sonds esoteric but for $100 I buy in why not


with sea trial we measured the cylinder temp and they were close +/- no smoke from engine whatsoever not at start not with smooth load changes so I wont rock the boat - pun intended



one of the previous owners made a chart for consumption for anybody to reference:


2100rpm 7,7gph 145

2000 6,6 135

1800 4,9 130

1500 3 110

1200 1,8 (90bhp)


nice one everybody!

 

[Meander]

Also Lepke - you mentioned a hydrogen generator - would you mind elaborating? thx!!!

 

[FF]

The usual DD rule of thumb is to use 60% of available power or more to have similar economy to other engines.

If you have a log seeing where the boat was cruised would give away the power required .DD has tables for injector size and HP, at various RPM.

The CC rating used on injectors is for 1,000 strokes of the injector.

 

[Meander]

Hi FF - cool info thx - "cc" I assume is metric for cubic centimeter

 

[FF]

"I looked into fuel polish systems and except for all the more and better filters there was a strong magnetic component where fuel goes through and the molecules get for lack of more scientific terms - aligned for better power whila also killing algae?? Sounds esoteric but for $100 I buy in why not"


For the same reason the Brooklyn Bridge is seldom an investment.

Or the guy in Kenya needs your bank number to send a you few million bucks.

"Fuel polishing" seldom works to clean a fuel tank , it only cleans the fuel in the tank, the crud stuck to the sides and bottom is seldom removed.Till the boat is shaken.

A set of good fuel filters with a home made selecting set up will allow switching tanks underway..

Best is if they are mounted OUT of the engine space (copper tubing or fuel hose is cheap) where a filter can be changed with least effort or danger.

 

[Jon H]

Any pics of your new boat?

It must be one of GH's very early pilot boats if the hull is steel.

 

[Ski in NC]

Memory is foggy, but I think the 80 and 90 and bigger were generally for turbo engines. For non-turbo I think the N60 and N70 were typical.

What injectors are in it now?

 

[Lepke]

Also Lepke - you mentioned a hydrogen generator - would you mind elaborating? thx!!!

We ran 90s in Vietnam on natural 671s at higher than yacht rpm. Considering a bunch of kids were running the engines flat out, the DDs held up well.

You can probably get a better description online for a generator, but here's mine: Hydrogen generator is a sealed tank with positive and negative electrodes in a solution that helps the power flow. One side produces 1 oxygen and the other makes 2 hydrogen. It slightly pressurizes the tank and creates an air flow to be piped into the air intake. All it does is increase the efficiency of the fuel burn. It only works up to about a 25% increase in mileage.

Usually it's setup to use excess power from the alternator to power the two electrodes submersed in the solution. You install an amp gauge on the positive wire running to the generator and add hydrogen peroxide to water until you get the amp use you want. You need to leave enough charging amps to keep the battery up in a car. Once you know the water to HP ratio, you can have replacement mix ready to go. Or build a supply tank like I did.

I've been playing with this since the 1970s oil embargo. Originally I bought a generator from someone making them and decided I could do better. Most of the ones sold are too small. But you can see a better picture online than I can draw. What I use now are 2-4" horizontal plastic pipes about 5' long, teed together with a riser that is capped and piped to a DD intake. Each pipe has a steel electrode (1" rebar) that dissolve over time. I have one HG under the drip pan of each DD. I have a 48v system for my inverter and that supplies power.

 

[Meander]

 

[Meander]

SKI_IN_NC

To answer the question I have to look next time I am on the boat - would guess N60 by previous owners max BHP statement of 140 which correlates with N60 - will let you know


Lepke
I was looking up those HHO systems over weekend - love it - was wondering since I have an air "blower" compressing air via spiral screws and an oil air filter on top - how to insert the HHO into air stream?

 

[Meander]

Attached Picture - Engine

Hope I am not annoying forum - try to figure out how to insert pictures from my computer to posts - I tried the attachment route - hope that

works

 

[Lepke]

SKI_IN_NC
Lepke
I was looking up those HHO systems over weekend - love it - was wondering since I have an air "blower" compressing air via spiral screws and an oil air filter on top - how to insert the HHO into air stream?

Just insert in the intake air stream. I have the same DD roots type blower. Mine is routed to the air silencer intake and is just in front, open to the air flow. There's a Y so it goes to both ends of the old style rectangular silencer. At anchor, if I'm going to run a generator for a long time, I send the HHO to a Perkins 4108 intake. But I have to cut the amps or the addition of so much bonus fuel causes the engine to oscillate and effects the hz. All my ac goes thru my inverter and the oscillation drives it nuts.
Once the HG is off, the flow of HHO flow quickly shuts off. I don't try to store any HHO because of fire or explosion threat. I talked to someone years ago that tried compressing and storing HHO in a propane tank, but under pressure it made some water, over time rusted the tank bottom, eventually there was a large leak and a small thermobaric bomb blew the roof off and windows out of his unoccupied workshop. I never had an issue with unpressurized HHO. I never did the math, but at shutdown probably have 2-3 cu.ft. of HHO that dissipates into a 1500 cu.ft. engineroom. I usually don't run the HGs until at or near cruising speed because the 48v alternators aren't putting out extra power at idle. I turn the HGs on by a relay controlled from the lower steering station or a switch in the engineroom. When everything is right and I flip the switch, I'll see the linkage move to reduce fuel to the injectors, rpm stays the same.

 

[Meander]

Hi Lepke - thanks for your detailed reply - I painted a similar picture in my head - have an old but gold 8KW Westerbecke generator right after the transmission to play and experiment with - keep you appraised - might take a while the project list is long


"I flip the switch, I'll see the linkage move to reduce fuel to the injectors, rpm stays the same" - that's one of a good visual aid - thx!!!

 

[Lepke]

Hi Lepke - thanks for your detailed reply - I painted a similar picture in my head - have an old but gold 8KW Westerbecke generator right after the transmission to play and experiment with - keep you appraised - might take a while the project list is long


"I flip the switch, I'll see the linkage move to reduce fuel to the injectors, rpm stays the same" - that's one of a good visual aid - thx!!!

With a small engine, start small. On a generator at light load, it's easy to overwhelm the governor. No harm, just shut down the HHO if it gets out of control.

 

[omoore]

Injector Selection

Most displacement yachts are way over-powered. Google for a formula to indicate power requirement for your boat's specs. Then call a Detroit Diesel Distributor or the factory for an injector recommendation.

 

[Trimjb]

More then likely N-60's for a 145hp, N-65's should be about 160hp. @2100 RPM for a 4-71NA
When you get into the 6-71NA you start looking at 2 valve vs. 4 valve heads.

 

[Meander]

Hi Omoore and Trimjb - thanks for response


You mentioned boat specs - I do try to get an overall sense of where energy is used/lost - how much is needed - is prop right sized and such.
Tough part with old Detroit Diesels (DD) in term of energy input is (to mention Lepke's note on fuel quality) that the in-time fuel consumption is hard to measure with fuel circling back in high amounts to tanks - so it will take time to measure over many miles to get an "average" sense of consumption.


I did see that there are fuel consumption modules out there with 2 sensors to measure delta from flowing into engine and out of engine - unrelated to thread and don't wan't to delude the topic but anybody experience/recommendations and such? - feel free to send me private message if forum rules are to keep thread topic clear to end.


Getting my dinghy and outboard this week somewhen so will check soon for injector size but yes as Trimjb said - would think/hope its N60 don't need any larger I assume.

 

[FF]

Beware with elderly DD engines , there are H series injectors and N series.

An engine built to operate on H injectors does not run well or start easily if newer H series are installed.

Most of the H engines were built in WWII and thru the 1950's.

A DD dealer can help if you have the engine serial number.

 

[Meander]

Thanks FF - good point - it seems and I have to check deeper - there was a company called GrayMarine that sold DD/Twindisc combos under their label not sure but went belly up some-when 80s??

 

[FF]

Grey Marine assembled thousands of engine packages during WWII.

Their 6-71 Navy training manual is still the best there is.


MY error...... An engine built to operate on H injectors does not run well or start easily if newer H series are installed.


Should read ,,will be hard starting if newer N series are installed.

 

[Meander]

FF - thanks for comment - I noticed it takes 20-30 sec max to jump on from cold - it has a beefy Delco Remy starter - and it jumps on no problem - I attributed that to the self priming injectors to pump the fuel through and build up pressure temp to ignite? - what is a normal crank startup time if I may ask??


Was wondering if a fuel primer pump similar to airplanes would lower the startup time if it even is fuel pressure related slow startup?? Unless the time is normal?



thx again!

 

[Ski in NC]

Looks like a pretty old package from the pic. Old mechanical shift gearbox. Can't really tell if fuel rails are external or not, that indicates quite old.

So could have come with the old HV injectors. I don't have any experience with changing them over to N, but I know there are differences.

A DD with N injectors set up right should fire off in one or two revolutions unless cold.

 

[Meander]

Thanks SkiInNC - good input to follow up on - cranking for 25sec vs a few revs startup from cold - Detroit handbook mentions max 30 sec so I didnt feel bad about it but if a normal cold start would be lets say 5-10sec then I should take a look - starters don't come cheap

 

[FF]

The old H or HV injectors should start with a turn or two, unless its quire cold.

Then its not extra fuel that is needed, but extra heat in the cylinders.

The old bus technique is 30 seconds of cranking and a 45 or so wait , then another 30 seconds of cranking , the heat from compression will usually have the engine start on the 3rd crank.

It may only be running on one or 2 cylinders , so keep the start button down until it starts to fire on more cylinders.Wont hurt the starter.

Starting in zero F requires a block heater or a touch of ether .

NEVER EVER use ether on a warm engine say that has simply run out of fuel, broken piston rings can result.

DD changed to "high compression" when installing the N injectors.

All they did was to raise the seat for the top compression ring higher on the piston.

If a DD was rebuilt , the "high compression" pistons were probably installed.

Happily on a DD removing one bolt will allow the air box cover to be removed so you can take a look.

Air box covers are great for winter layup , spray the cylinders with preserving oil , yes there will be loads of smoke on the first of the season startup.

 

[Meander]

Hi FF - wow very good information - that would somehow confirm that its in original state without overhaul other than at some point changing color from yellow to Detroit blue/greenish - ha - and smartly overpainting all info plates on cylinder head.


As for the hint on GrayMarine selling off WWII components - I was surprised to read on the Twindisk tranny schematics and manual some WWII dates - old but gold - wow is that stuff in awesome quality and shape - thanks and nice one everybody!

 

[FF]

"wow is that stuff in awesome quality and shape"

The info on my T-D from WWII stated "do not shift from Fwd to Reverse at full throttle TOO OFTEN!

Guess it was created for landing craft hitting a beach , but would not be a choice today as it was shifted with a lever and rods, not a cable shifter, that takes less time to install.

All gears inside ran in 5 quarts of 50wt non detergent oil, no oil cooler was required.

Those were the days!

 

[Trimjb]

"wow is that stuff in awesome quality and shape"

The info on my T-D from WWII stated "do not shift from Fwd to Reverse at full throttle TOO OFTEN!

Guess it was created for landing craft hitting a beach , but would not be a choice today as it was shifted with a lever and rods, not a cable shifter, that takes less time to install.

All gears inside ran in 5 quarts of 50wt non detergent oil, no oil cooler was required.

Those were the days!

Those gear boxes were called "Crash Boxes". Yes, typical Landing Craft gear boxes. I have 2 in a modified Landing Craft. They can take a lot of abuse.
Easy does it though. Parts are getting scarce. I had to have a few parts made.
Palmer Johnson was a good source for clutch plates. There are a few old yards around the Gulf Coast that have bone yards for parts. I bought a couple of old boxes just to have on hand for parts.