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Detroit Diesel 2-71 mods for fuel consumption

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Old 01-11-2012, 10:37:24 AM
fallrock fallrock is offline
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Default Detroit Diesel 2-71 mods for fuel consumption

We have a 1958 2-71 genset that burns about a gallon per hour. Can this be improved? This unit is completly stock to my knowledge.
Thanks in advance for your help.
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Old 01-11-2012, 03:58:51 PM
Norm W Norm W is offline
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Default Re: 2-71 mods for fuel consumption

What injectors are you running? What type of cylinder head do you have? When was the last time the air cleaner was serviced? These things all matter.
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Old 01-11-2012, 08:47:39 PM
Jeff Miley Jeff Miley is offline
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Default Re: Detroit Diesel 2-71 mods for fuel consumption

Norm is correct. The smaller the injectors the less power and the less the fuel consumption. The reverse is also true. Good reliable engine. The 71 series was built for 60 years or more and were decades ahead of their time when first introduced.
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Old 01-11-2012, 09:55:37 PM
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BTPost BTPost is offline
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Talking Re: Detroit Diesel 2-71 mods for fuel consumption

One thing to remember here is that with Diesel Engines, once you pay the price to get the machine rolling over at speed, then Fuel Consumption is almost directly proportional to the Load or Work being done by the Genset. It is a very Linear Straight Line Ratio.... Gallons in, and Kw's Out. The efficiency of the engine, is not nearly as important in Consumption calculations, as the Specific Load in the Genset. Just Say'en.... YMMV.....
Bruce in alaska
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Old 01-12-2012, 10:10:49 AM
Cbum Cbum is offline
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Default Re: Detroit Diesel 2-71 mods for fuel consumption

I would pop test injectors adjust exhaust valves run the rack and adjust injector height or timing. As engine is coming up to temp use a heat gun to tell if both cylinders are coming to temp at the same rate . if not time for a tune up . Also which injectors do you have . I forgot the letter designations but the newer injectors may give slightly better economy . Is this a 1200 or 1800 rpm genset?
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Old 01-12-2012, 11:38:06 AM
pegasuspinto pegasuspinto is offline
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Default Re: Detroit Diesel 2-71 mods for fuel consumption

The easiest way to increase the efficiency is to increase the load. I'd put it at 80-85% or so and keep a chart, adjust the load up and down and find the sweet spot. If you can't change the load, you change the engine-not so easy. My 2-71 burns close to a gallon an hour with no load, tho I don't claim mine is in any great state of tune. Good intake, exhaust, oil, etc is important. If the exhaust is clear, and you've got a few KW on it, I can't see you getting much improvement. It breathes like a 284 cubic inch 4 stroke engine! That's quite a monster to keep rollin' on a gallon an hour!

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Old 01-12-2012, 01:15:50 PM
turbodiesel09 turbodiesel09 is offline
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Default Re: Detroit Diesel 2-71 mods for fuel consumption

I been told that if you added an Electric Governor to most Diesel Gen set's that it is suppose to help with lowering the amout of fuel you burn. This is if you are running all the time.I agree with checking your injector's make sure the timing is correct, and the rack is set correctly. If this is for back up, and or stand by I would be happy with a gallon and hour. There are a lot of people that have small gas engine generators that are a lot smaller and burn a gallon or more an hour. You cannot compare your set to a small diesel generator. You have a lot of heavy steel you are moving.
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Old 01-13-2012, 11:49:49 AM
miltruck miltruck is offline
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Default Re: Detroit Diesel 2-71 mods for fuel consumption

My own research has shown that these older gen sets will use about .85 to 1.1 gallons per hour per 10 kw. Our 2-53 20kw set used about 9-10 gallons over 13 hours during the October storm with a light load of less than 8 kw. Detroits like a steady normal load. A 20kw set works best @ about 15kw non stop and I would guess use about 1.1-1.25 gallons an hour. Other wise they wet stack and slobber bad. I installed an exhaust plate in the outlet of the big muffler to help keep some of the heat in the system to cut down on the slobber. I think it helps some. Smaller sized injectors will help some, but under any real load the rack will just pull further and the engine will use about the same amount of fuel, up until the injector is full open and then you will lose power.

The newer smaller engines will be down in the range of .5 to .8 gallons per hour, but only in the 5 to 10 kw range. For a steady load, you can't beat the Detroit powered gen set.
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Old 01-14-2012, 10:07:06 AM
K-Tron K-Tron is offline
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Default Re: Detroit Diesel 2-71 mods for fuel consumption

Modifications to the Blower, Cylinder Head, and the addition of a turbocharger will decrease fuel consumption. These old two cycle brutes require a blower to scavenge air. In any situation, the blower is a giant parasite consuming tremendous amounts of energy to spin and compress air inside of the air box. Adding a turbocharger converts some of the waste heat energy of the exhaust into pumping air into the blower, which decreases blower noise, and blower horsepower needed under a loaded condition. That being said, 2-71's were never offered with a turbocharger, so you would need to make your own exhaust manifold, and add a properly sized turbocharger, to make it work. My friend Jason did the same with a 2-53 he decided to put in his car. There are images here:

I think he used a Holset HX30W, and he said it was on the small side for a 2-53, but a HX35 may be a good size for your 2-71.

If you really want to hot rod this engine for fuel economy, talk to Ervin at Leid Diesel 717-776-7725. They made a customer with a 2-71 a modified blower, with 2 lobed straight rotors, (which replaced the 3 lobed twist rotors commonly found on the 2-71's) to blow more air. These engines were also only fitted from the factory with 2 valve heads. You can get a 4 valve head off of a 3-71 or 4-71, and cut it down, so that you can make a custom 4 valve head for your 2-71. Adding a low lift, high volume cam will also do wonders for your fuel consumption. You can also modify the injectors, going to a latter N series injector, or a C series injector. If your engine is stock, it may have HV or S injectors, which are 50+ year old technology. The latter injectors are a simple swap, as all offset body injectors from the 53/71 and 92 series engines will crossover. (I think the 149's used bigger injector body's)

Good luck,

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Old 01-14-2012, 11:20:46 AM
cornbinder89 cornbinder89 is offline
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Default Re: Detroit Diesel 2-71 mods for fuel consumption

Adding a turbo to a blower scavanged engine with no other mods will INCREASE the blower load, not decrease it. Supplying air at pressure to the inlet of the blower makes it more dense. The blower is a fixed displacement pump and will always move the same amount for the same speed. But now the air to be moved is denser and the same pressure ratio across the blower, mean the load will be higher. To reduce the blower load you must slow the blower or add a bypass to the blower.
Detroit used a sprial lobe on the blower to prevent the pulseing that a streight lobe would cause.
There are many inproved injectors depending on what you have now. A good Detroit shop shop be able to advise as to what can be used with your engine.
You can also check on the ATHS website and ask in technical question. There is a man (JunkyardDAN) who was with detroit for many years and has a lot of knowedge. You need to know what you have now, before you can decide on what you want to change.
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