Why are Detroits so loud? Is it just that they didn't come with a good enough muffler, or something else with the design? http://www.youtube.com/watch?v=97r0NXNT8LA
They are 2-stroke engines, like a chainsaw.
Cause they are Awesome! ha ha now seriously... like Mitch said, two stroke diesels... Louder if they are aturaly aspirated. turbo jimmy's are a little quieter...
Well I knew they are two stroke diesels. I've owned a few two stroke dirt bikes and it wasn't that hard to silence them for woods riding. Never owned a Detroit -- do they use straight pipes on them?
It's not just the exhaust noise alone, you're also hearing noise from the engine that you don't hear from typical 4 stroke liquid cooled engine. First of all you have a roots blower making noise as it spins. Second, you're hearing combustion chamber noise because of the open "air box" design of the Detroit two stroke, noise that is typically muffled by coolant and engine block on other engine designs.
As one of my friends used to say "Detroit Diesel... The only engine in the world that can take perfectly good diesel and turn it into noise" They are a bit noisier then some of the others but the silver series were not that bad. As far as running straight pipes, you better have some very good hearing protection.
In the '80,s worked at asphalt plant with Roots blower for baghouse. That's where the Detroit noise comes from, the blower sucking air. Don't ever want to be around one with straight pipe, even on back of green scraper!
Makes one wonder if they still aren't the most popular..... thousands of the bugger's still running in boats around the world.
I was driving an old White 9000 tractor/trailer with a 8V71 and 13 speed hauling asphalt. Half way through the morning the exhaust pipe blew off the muffler right under the cab. Words can not describe how noisy that thing was!!! Fortunately I found a pair of ear muffs behind the seat, it wasn't my regular truck. I had to work the remainder of the day with it like that.
A lot of people hate the old GM Diesels , if you think about it they were the ones hauling parts to cat and cummins while they were building they're names in the truck engine business. A little lack of modernization killed them until they came out with the series 60. Always said they had no power , they had a funny power curve on or off. I had a 3-71 and a 4-53 in Oliver tractors and they would hold there own against any other 120hp tractor. The 3-71 would over heat if you pushed it but it was pulling 125 pto hp. Injectors were a little to big.
This is an interesting question with an unexpected answer. What is the function of the blower on a Detroit Diesel??!!
The DD does not have intake valves. there is a box around the lower portion of the cylinders that the blower charges with air. The liners of these engines have a series of holes in them that mate up to the air box. When the engine is running the air is pushed into the cylinder goes up for ignition , has power stroke then the exhaust valves in the head open as the cylinder goes back down to BDC the blower pushes the exhaust out then charges the cylinder with fresh air for combustion again. On a straight piped engine you can here the blower working. The blower doesn't work to actually build pressure like a turbo or super charger. ( If your building a pulling tractor engine you can overdrive the blower for an actual super charger effect. AKA cheating ).
I still have a baby Detroit in my 59' JD 440 track loader-a 2-53. Runs like a top,but loud of course.
I ran an "A" model Terex TS 24 scraper with a non turboed V12 and it was insane loud. The sound would go right through you. The muffler wouldn't even help. The same company had "B" model TS 24's and they were much quieter.
The problem with GM IMHO was that they spectacularly failed to see the writing on the wall that 2-strokes diesels were going the way of the dodo ..........
Apart from being the loudest SOB on the block, I think it was one of the most engineered engines ever built . What other engine can you build from a pile of parts 8 different ways . reverse rotation , switch the block front to back , put cam on each side , switch head front to back , etc etc . The 71 series i think came out in 1938 for the military tanks and everything was basically the same right up into the 80s or there abouts. After running DDs for the last 40 years and now half deaf LOL , I have nothing bad to say about the 71 series DD other than the noise and the oil leaks . Now as for the 53 series ( unless its in a compressor or something with a constant speed) , I'll call it a poor mans engine ............you'll always be poor while you own it LOL . The 92 series is worse !!!
Boats are where the Detroits really excelled. With a wet exhaust they mumbled at low idle. Bring them up to half throttle and they bring a feeling that some women compare to sitting on an idling well tuned shovel head Harley at bar closing time. Full throttle and they bark like a Rottweiler defending a litter of pups. I know the noise comes from the blower and such, but I always figured it was more because every stroke of the piston is a power stroke. So two, four, six, eight or more cylinders hit on every revolution which makes for twice the noise of any four stroke with the same number of pistons. I haven't worked on one for years so I sold all my special tools for these monsters yesterday. There are younger people looking to keep the faith. Also makes me see the gray on skull in a different light.
John C. I wish I had known you were selling your special tools. I have a pair of 6-71TIs in my boat and I try to do all my own maintenance. Any manuals or service documents left? Rick
I think all I have left is an old 71 series book. I'll have to look to find it.
Here's a bit of a write-up on the Detroit. http://www.dieselduck.ca/historical/01 diesel engine/detroit diesel/index.html#.US2YgTdf2z8
John: If it is a service manual I would be honored to have it. Rick
boaterri, you can buy most of the tools from Snap-on or you might be able to order the tune up kit made by Kent-moore through your local dealer. I know you can get fuel line tube socket from snap on still.. Do everything by the book and you will have no dramas...
Old truckers commentary... If a Detroit would run like it roars, it would outrun the word of GOD... Just saying.
Cat-man, what you said is true. If there was an empty hole somewhere in a truck, a bus, a tractor, or a boat, the GM engineers would tinker-toy (erector-set) a bunch of 71 engine parts, and power, to fit into that hole... I know some guys maintaining 40 year old snow blowers with 12v71s. The only parts of the machines that aren't PITA nightmares to keep working are the Detroits. Detroit Green or Silver Series, DD engines are all Delo black...
:falldownlaugh Delo Black
Isn't there a saying that if you take a picture of a Detroit engine and put it in your pocket that your pocket will turn black from the oil leaking out?
Every time that piston goes up it fires , on the way down it draws fuel through a reed valve , up itfires again , 2 cycle . that is part of the noise and also why they sound like they are running so fast . Very good design and don't be surprised if they don't come back .
the old two stroke or cycle (whatever floats your boat) Detroit's were a feet of engineering all of there own they were a modular engine with transferable componentry between size's a 4-71 was a straight four cylinder its heads could be used on the 8v71 then also on a 16v71 as they were 2 8v71's bolted together the 6-71 and 6-92 where treated the same use bits off ethier to repair a 12v71 of 12v92 respectively 3-53 and 6v53's heads and the likes where interchangable etc...etc...etc the list goes on and then there was the pistons and other components as long as the 53,71,92,149 was the same they where compatible also they where a series of engine that if choosen correctly could power a whole fleet of trucks put a 4-71 in the small delivery truck's then a 8v71 in the large delivery truck's then a turbo 8v71 in the semi's and then in the workshop have a large supply of parts compatible to the entire fleet quite genius really cheers the learner
detroit's best virtue was also it's worst in my opinion: it lasted too long.
They worked great with a machine that had a convertor,powershift,or in front of a hydrostac.Anytime they was used on manuel shift stuff and they pulled down and lost rpm they would fall on there face.Power only at high rpm.But used with the other examples they performed great and the fuel usage was one of the best when you keep the rpms up.Loved the fuel saving. Liked the 71 series better then the 53's.The 71 series was dry sleves compared to wet on the 53's,that you had to watch for water(antifreeze) getting in the oil.Also the 53's tended to have more oil leakage. Also learned when used on a trencher with the hydrosta,that when it pulled down,or you hit a rock and stopped quick by pulling the hydo lever back to fast,just before it died,she would fire back up on her own and be running backwards.Lots of smoke and oil trying to come out the air breather.Good times,loved it! Lesson learned.
You better read that book again , no reed valve here in the Jimmy Diesel world.
They always leak but they always run. Put one low in the bilge and that tub will always come home, if it gets low on oil there is always some in the bilge.:usa
just tell me that you're talking about a chian saw and not a detroit because detoits do not have reeds and the fuel is not drawn in thru the intake just so we're clear.
The problem was that the injector sets max power by determining the maximum quantity of fuel that can be injected per stroke and no other way. Therefore higher RPM = more strokes per second = higher total rate of fuel injection = higher power. (DDEC injectors did not have this trouble as they were electronically controlled and a DDEC could lug down like any other modern engine) Contrast this to Cummins from the same era with the PT fuel system, total fuel rate determined by fuel pressure through an orifice, independent of engine RPM, melt the engine down if you're not careful running it too low of an RPM. Cat of course had a discrete injection pump with its own profiles.
not even
Well maybe not quite, but I used to drive a DDEC II 6v92 every day and that thing would chug right down to 1400 RPM. I forget what the high end was, maybe 2000-2100? But I remember one particular hill I had to go up frequently and it always seemed to settle in at 1500-1400 there.
Another interesting tidbit is in the numbering system a 4-71 was 4 cylinder 71 cubic inches per cylinder and the same as the number goes up.In the Dresser Haulpacks we had 16v149 now thats alot of cubes!I see that was listed in article sorry I missed it.
The unit injector (non-electronic) had a barrel and plunger arrangement the plunger was machined with helix and the rack moves the helix with the rack at minimum the helix is at its smallest area at full rack the helix is at full helix opening and full fuel the injector stroke is always the same. The only increase in fuel is speed so at lower RPM you just get smoke under load as speed increases you get more fuel and power.
hmmmmm.......... I wonder then why they were fitted with a governor ??? .......wouldn't have anything to do with adjusting fuel delivery at various engine speeds would it ?? I think they were a very well designed engine for their day, for all the fore mentioned reasons, cat even copied their unit injector/sleeve design (with questionable success and not that great imho). The UD version with better sealing and catch can on the airbox drain was an improvement and yes they were known as rainbow makers in the wet and did leak oil with a few miles on them particularly when idled for extended periods but they had an enviable reliability record and were easier on truck driveline components due to their softer delivery than other engines (a saving for fleet operators who used steering wheel attendants in place of operators)
From what I understand they were usually fitted with a min-max governor in automotive applications, meaning that the driver's foot controlled fuel rack position directly when inbetween min and max RPM. And with the pedal controlling fuel directly, the RPM comes into play meaning the faster the engine goes the higher the lb/min of fuel injected because of the increased number of strokes per minute. Ever try to use a hand throttle to set a specific RPM unloaded? The engine either takes off to max RPM or returns to idle but it's not really possible to get it held steady. Of course, as with any Detroit Diesel part there were an infinite variety of combiations made.
One of the nice things about Detroit was they offered a "variable speed" governor on some of their engines. This was very handy for some equipment applications as it "holds" selected engine RPM regardless of load. I operated a number of hydro cranes with this arrangement, you could set the throttle at a good high RPM for operations, at moments of no work, engine would hum at that RPM, then start pulling levers to move crane functions, pumps would be under load which would load engine, the variable speed governor would crank up the fuel to match load, holding set RPM. Very nice feature for crane operations.
A few interesting thoughts above on how jimmy's run... can't say I have ever heard of the reed valves before! Chainsaw, motorbike yes... jimmy - NO. However most of you guys have a handle on how they work reading the above posts. Willie you are correct, they came with LSG or VSG governors. LSG = Limiting speed governor, VSG = Variable speed governor. Both are complex but in a nutshell - LSG governs low idle and high idle only. So yes it governed in between by how much the operator is standing on the loud pedal. If there is no load and you stand on it, the LSG will pull back the rack once RPM reaches high idle setting. VSG will govern fuel at whatever the fuel lever setting is at. found on boats, cranes, pumps, gensets and most other "stationary engine" applications. Quite a few ways to get them to not leak oil, we used "ultra-blue" rtv sealant mostly. Many leaks are caused from 'open' threads in the gear train housings, need to clean bolt and thread thoroughly, thread sealant on bolt and also rtv under washer and bolt head fixes this.