Ford guys can't figure it out

[Cummins Corvette]

I was playing around and visited the ford diesel forum. We all know that the ford owners are slightly disadvantaged (if you know what I mean ). As you can tell I am kind of board and think that the folks here could figure this one out. They were discussing how adding a supercharger to a diesel that already has a turbo. The idea came from someone that saw a Detroit Diesel with both. No one there knew why this was. I am betting that there is someone here that knows why Detriots have both. This forum is such a good info source with a bunch of smart people so lets see if someone here knows why Detriot Diesels have both. Is it just for power or what?

 

[SnoKing]

Detroit Diesels like the 6-71 and others of the family are two cycle diesels and the roots type blower is used to provide the air charge to the cylinders. These engines only have exhaust valves. At the bottom on the cylinder liners are ports that allow the compressed air to enter the cylinders pushing the exhaust out the exhaust valves at the same time. Turbo's were added much later in the life cycle of the design. Snow King

 

[Cummins Corvette]

DING DING DING!!! And Snow King wins!!! I knew there were smarter people here! . I used to have a 6-71 without a turbo. That thing was tough- cast iron pistons. The thing would not run without a supercharger due to the fact that it lacked an intake stroke (and otherwise an entirely different design). The exhaust from those engines has a unique smell to it also, and the only reason I can think of is that a two stroke diesel burns the fuel with more oil and exhaust in the mix? When a bus with one of those in it passes me I can always tell that it is a detroit because of the smell.

 

[SnoKing]

OK, now that we are having fun. The 6 is for the number of cyclinders and 71 is for the Cubic Inches of a single cylinder. These engines were built as 1-71's 2-71's, 3-71's, 4-71's, 6-71's, 6V71's, 8V71's, and 12V71's. I do not believe that there was a 16V71. There was a 16V92. Seattle fire boat the Chief Seattle has three 3000HP 16V92's. There are also samer 53 series and larger series 92's and 149's.



These engines are a true engineering marvel. The blocks are a mirror image end to end, a left hand 6-71 can be reassembled as a right hand engine with only a very same number of different parts. As a kid we installed a government surplus 6-71 in our Sea Scout ship.



I also drove a Titan 90 Chevy truck with a 350HP 8V71 for three years. This was a turbo charged model. Non turbo 8V71 was a 318HP unit. 350HP Cummins would out pull me any day. When they came out with the 92 series engines the HP ratings of the Detroit stood up to the CATs and Cummins much better.



The big problem was the two cycle design is not a clean burning engine and has been scrapped for the new 2000 series or something like that. Snow King

 

[Ray Torresdal]

92 series Detroit

The 92 series Detroit might run w/Cummins or CAT, but rarely as long w/out overhaul. On the bright side, parts were cheap and readily available. Ray

 

[Harley152]

yes there was a 16-71 and probably still is---was basicly 2 8-v 71's bolted together with a common crank---2 blowers, 8v71 heads interchangeble to each point, also available in TI, and TA(turbocharged and intercooled or turbocharged and aftercooled), some we're 2-valve and some we're 4 valve----the value to detroit diesel for many years was and is---cheap to buy---lightest weight/horsepower---and because of the total interchangeability of parts---cheap to fix 'cause you could practically get spare parts at 7-11!!! Disadvantages---lousy fuel effigency---NOISY---oil EVERYWHERE(pressurized base from the blower means oil "mist" everywhere"---lousy oil consumption( a good running 6-71 generator will use approx. 1 gallon of lube oil/day[24 hours]---and a life expectancy of 10 to 12,000 hours between major overhauls(about 60% of our 4-cycle cummins).

 

[QRTRHRS]

I ran quite a few 318's. Some had more snot than others. I understand that was due to the injector size? Also drove a Ford tri-axle with a 238/13spd DO. Shift, shift, shift and shift some more.



Talk about easy to fix. Running through North Carolina one day, I see an 18 on the side. Slowing up a bit, I come on these two guys with an Astro 95', cab up. They have a head off, patching it up along the road. By the looks of that rattle box, I think they might of done that before.



Used to get blown off by this guy running a 12V?. For it's time, it was pretty untouchable except for the fuel stops.

 

[Joe G.]

The best description for the 6-71 in the fish boat I used to run was that it turned fuel into noise! After running it for three days at full throttle to get to an albacore bite we were ready to swim for it! The damn thing never broke.

 

[SnoKing]

Joe G. , they don't call them screaming jimmy's because they are quiet. As a kid there was nothing that sounded cooler than the Coast Guard 40 footers with two 6-71's and straight exhaust out the back.



When we first put the 6-71 in our Sea Scout boat, (a WWII Coast Guard 38 footer) it had 90 injectors and we could outrun the local CG 40' by putting the governor in battle, until we burnt it down. Replaced two pistons and liners in the boat, and the local log truck mechanic traded us some 70's for those 90's so he could make someone's log truck go faster. We pulled the head, jacked up the front of the engine and drop the pan right in the boat, and pulled the bad pistons. They looked like someone had used a cutting torch on them (90's). Snow King

 

[Joe G.]

Yeah, those 40 footers sure sounded good when we were screaming to be heard over the engines the time we rescued some guys and wanted to transfer them to the CG boat. They were so loud that it interfered with that kind of thing. The CG crew and us had a hard time communicating. We got the guys over without the CG fouling our rigging. Lots of fun on a dark night in rough weather. The later CG boats are a lot quieter. They finally figured it out.

 

[Dr.Evil]

You underestimate those Ford boys. Detroit 2-cyl. engines can have the air blow thru the engine either way so the positive displacement blower HAS to be put on to make sure it goes the correct way. A reed valve would have worked too, but the minimal extra boost helped performance. The turbo just pressurized the Roots blower. I actually thought they were a poor engine. Had to drive them flat-footed, and there was NO mid-range torque.

 

[David_VT]

Fondly recall the twin turbo VT901's in my CG41'

They were monsters.



Made that aluminum 41' foot with it's power screws (i. e. not speed) move real well. Towed fishing boats more than twice it's size with ease.



It was my memory of CG days that forced the decision to buy the Ram oil burner over any other!!!



Cummins ROCKS

====



Another boat 32'UTB had twin cats (3208maybe) and a detroit water pump for the overhead fire monitor. Interesting boat, especially being all fiberglass. (no so good in the ice... )



Spent a long weekend under the Boston railroad bridge when it caught on fire, oh so many years ago... . You know, those x-navy candle burning Oxygen Breathing Apparatus things really do work. .

 

[Dr.Evil]

You underestimate those Ford boys. Detroit 2-cyl. engines can have the air blow thru the engine either way so the positive displacement blower HAS to be put on to make sure it goes the correct way. A reed valve would have worked too, but the minimal extra boost helped performance. The turbo just pressurized the Roots blower. I actually thought they were a poor engine. Had to drive them flat-footed, and there was NO mid-range torque.

DENNY... ... ... ... ... ... ... ...

 

[THubbard]

I travel with 3 other 5th wheel fools and they have Fords, I get crap all the time. I finally told them that it sure was nice that Ford made their engines with 25% more displacement so as they could keep up with my 24HO. They still don't understand..... DAH!

 

[Gonzo 1066]

screaming meemies

The later model Detroits used a turbo ontop of the blower to help meet EPA requirements and help with power. =more air=more fuel=more power. The turboed engines were called the silver series and were much better engines than the older series. This is not to say they were in the same league and the current Cummins, Cats and detroit 4 stroke engines. I have seen more than a few times that operator error would cause a Detroit 2 stroke engine to run BACKWARDS!! It was interesting to see exhaust coming out of the air filter! These engines were high horsepower for there weight and quite inexpensive compared to equivelent hp 4 stroke engines. If you ever get a chance to drive a large truck with the old 318 detroit you will see the reason so many old truckers have inline 6s now. Those engines had good hp on NO torque!! Typical for a V8 engine.

 

[redneckdr]

PHORDS

a friend of mine just traded her flowerpoke for a new used CTD to pull her horse trailer. LOVES it, esp the fuel mileage. she still runs with a bunch of phord drivers, and laughs at them at fueling time. bone stock, she keeps up with them, too.

 

[SnoKing]

If I remember correctly, the 350HP in the Titan 90 (Same Truck as the Astro 85) was driven in a 300 RPM range. I am trying to remember I think it was 1800 to 2100 RPM's. Never below the lower limit and never let it idle very long. Hauled 8500 gallons of Gas out of Port Angeles. Averaged 4. 5 MPG half loaded/half empty. Snow King

 

[Case500D]

The purpose of turbocharging a GreasyTroit is to remove the load of the blower on the engine. A blower robs an engine of power because it is either belt or gear driven off the crankshaft. The turbocharger just helps relieve the load on the blower, hence, more power!

 

[KKaiser]

Two Strokes

I thrashed many a Detroit while playing Army in the '70s. 6V53s, 6V53Ts and 8V71Ts. they ran like a raped ape if the Allison was working right. If not, they were slugs. I too have fond memories of 3am alerts in Germany with the smell of diesel heavy in the air prior to leaving the motor pool. This definatly led me toward purchasing a Cummins.



My question to you folks is: does anyone know of a site that shows the cycle of a two stroke diesel? I got in a conversation with a guy at work today about it and couldn't remember how it worked. Felt like a moron.



Thanks, Kent

 

[SnoKing]

Read back in the string, I explain how it works. Snow King