Supercharger,Turbocharger Question.

[Overmod]

I think this is somewhat generic on Mercedes and BMW diesels: when you punch them, the turbo often 'won't keep up' with the fueling (whether because of weak wastegate, backpressure due to plugged cat, or whatever) and the rich black smoke emerges.

I had one of the Baby Continentals with the 2.4 liter turbodiesel, and you could have fun on steep grades by punching the throttle into kickdown (this used a ZF transmission; the Germans love 'kickdown' the way the Japanese love 'drifting' and have fancy maps in many automatic transmissions that go down more than one gear...) This car had dual tailpipes, and wonderful smoke would come out of them, especially when I was towing a trailer at the same time (LOVE that air suspension!!).

I can't say whether a stock 524TD motor in good condition throws acceleration smoke. I do know that on occasion I've been able to provoke trailing smoke out of my '94 6.5TD Suburban... which isn't supposed to happen with the electronic Stanadyne pump and the pathetic levels of boost this engine uses in stock trim.

I won't comment on how envious I am of certain people with PSDs.

I did have some fun talking to a guy with a pre-24-valve Cummins in a Dodge. He mentioned that his mileage and acceleration weren't what he expected, and he was getting lots of smoke, and in general the truck wouldn't perform 'no matter how hard he hit the accelerator'. I told him that diesels needed a more gentle 'foot' most of the time -- let them accelerate into the load, and 'tap' your foot a bit to work the automatic transmission in and out of stall. He went out of the parking lot to test this... like a scalded cat!

By the way, it isn't unusual to see a puff of smoke from car diesel engines with worn turbo bearings, or with worn rings... but this may be WHITE smoke when seen against dark backgrounds. I'm also used to seeing a brief puff of brown smoke from larger gas motors when someone goes out to pass or changes lanes from cruise and 'punches' the throttle all the way down; whether this happens with sequential port injection, I don't know.

For sheer fun, watch someone with a Peugeot turbodiesel start up on a cold day. I wouldn't have believed the banks of white smoke, and we're not talking misfiring cylinders either! (Run the engine up to about 1500rpm to spool the turbo and the exhaust rather abruptly clears up even when cold!)

[oltmannd]

QUOTE: Originally posted by Overmod

I didn't think there was anything 'magical' about EMD's mechanical drive, only that it eliminated the problem with turbo spoolup at low engine power. Think of the fun Alco could have avoided with a drive and sprag clutch to the 244's turbo wheel... I enjoy the smoke show as much as anybody, but all that soot could have been horsepower. And now the EPA is watching...

Not sure you can even have a meaninful amount of turbo lag on a two stroke diesel...I've always thought of the fast loading ability of EMD engines as a byproduct of the design, not because of it. A overriding clutch is an awfully expensive way to get rid of turbo lag....

GE pulled all kinds of tricks to eliminate smoke. "Half notches" on U25s. 1-5-8 speed schedules on later U series. "Skip 3, double 6" on the early dash 7s, and finally a three slope loading curve on later dash 7s and beyond. While an EMD will get from idle to full load in about 25 seconds, a GE needs 80 and more than half comes on in the last 20 seconds. Can make for some fun times starting trains with mixed consists...

[Anonymous]

Overmod mentions the introduction of water into the system to provide extra power through steam pressure. It's funny, but my little Skoda straight diesel always seems to run better and more smoothly in wet weather (we get a lot of that over here !) and there don't appear to be any adverse side effects - I have owned four diesel cars - two normally aspirated, one low pressure turbo and one turbo - and they all appear to be subjected to the same wet weather effect. On all of these, the engines have always ran perfectly and felt unburstable, and were only scrapped because the rest of the car fell apart around them. Am I the only one to notice this effect ?

[adrianspeeder]

I'll tell you something, NOTHING and i mean nothing puts a smile on my face as fast as when i MA***he throttle on over 600 foot pounds of torque from my PSD!!!

POWER STROKE DIESEL!!!

I wish it was a stickshift, but i make do with the automatic. To get the best launch, i left foot break, pop to 4x4 high, and give enough throttle to get the boost built without breaking free, and then when the tree goes to green, dump the break, and full throttle down the quarter mile. I got in the 14s, and for a three and a half ton TRUCK, that is pretty dog on good.

Also have no problem acceleratin on the highway. just crusin, i can punch it and the boost gauge pegs at 25, and i rocket away. All with just enough smoke to let you know its a diesel.

The only motor i like better than my 7.3L PSD is the 5.9L inline six cummins. But i hate dodge trucks. If ford put the cummins in the superduty, there would be a long line at the dealers and dodge would be out of the diesel truck bisness.

Keep on truckin,
Adrian"diesel"speeder

[Modelcar]

....Adrian.....Are you saying a production Diesel Power Stroke to 1/4 mile in under 15...??

[adrianspeeder]

15.9 stock, 14 with chip. see my "what would happen thread" for what a really modded diesel would do.

Adrian"high on diesel exhaust"speeder

[Modelcar]

Ok...that production number pretty much coorelates to what I've seen in print...and you better thin that thick diesel exhaust out with a bit of oxygen, probably would be a bit better for you. You really sound "hooked" on the diesel bit.....

[Anonymous]

I CAN TELL THE MAKE OF AN ENGINE BY THE SMELL OF THE EXHAUST!!!!!!!!!!!!

i CAN TELL YOU IF ITS 4 STROKE, 2 STROKE, DIRECT OR PRECUP !!!!!!!!!!!!![:P]

[Anonymous]

Oh, I should also say all engines run better on a cool damp day.

When I was younger and stupider, I would ride my KZ650 flat out in top gear about 120 mph very early in the morning about 4 o'clock in southern california, and every once in a while the road would dip and I would hit a pocket of cold air and pick up another 5-10 mph., a nice little 500 rpm kick in the pants.

[Overmod]

modelcar: see what Diesel Dynamics is doing (with 7.3, not the newer 6.0 which I would think could be 'thumped' still better). 14s are bone slow for a PSD in a pickup; there are some modified Excursions that do 12.9s or better... (at 127+mph terminal speed!)

Interesting further information on EMD turbocharging is here:

http://utahrails.net/webpubs/up-gp9-turbo.php

An interesting thing about this article is that it nowhere discusses the design of EMD's 'replacement' approach, but notes (if one knows what to look for) that AiResearch understood some of the consequences of turbo lag on EMD 2-strokes, and used smaller turbos (just like some modern engines like that in the EB110 Bugatti) to keep the lag down. They also mention that the Elliott engines had two turbos "above the Roots blowers" (which indicates that the scavenge and boost were two separate, parallel systems on these locomotives) but later that many of the converted engines had the turbos 'replaced with Roots blowers' (or some just-weaselly-enough language equivalent to indicate that the authors didn't care about the key difference between turbo-with-Roots and turbo-without-Roots in assessing 567 engine operations!)

Makes interesting reading... in part because most of the early journal references are in SAE publications (an unlikely place, I'd think, to read about locomotive technology), and in part because even the earliest reference cited uses the word "turbocharger" explicitly to refer to what's being done, in the early 1950s.

[oltmannd]

QUOTE: Originally posted by Overmod

and in part because even the earliest reference cited uses the word "turbocharger" explicitly to refer to what's being done, in the early 1950s.

And engineers (mechanical, that is) often prefer "gage" to "gauge", too. I think they're just lazy :-)

[Overmod]

Engineers can sure be lazy -- some of 'em also use 'guage'.

To be honest, I use 'gage' to refer to things like Jo-blocks and 'gauge' to indicators with dials and needles. Like the difference between disc (as in brakes) vs. disk (as in computers), never confusing the two.

I think it does point to the automotive community, either led or exemplified by SAE, as being the place that 'turbocharger' as a word for exhaust-driven-turbine supercharger got established...

Perhaps we should be thankful that someone didn't trademark the word, like 'streamlining'. And then try all sorts of suits.

[Anonymous]

Actually, I have seen use of the term "turbocharger" in newsreels from WWII era. They were used on both fighters and bombers. Watch programs on The History Channel on cable or satellite TV or Discovery Wings channel.

[jchnhtfd]

Just a miscellaneous thought on the wet weather effect... it isn't the steam (the water is already mostly vapour) it's that water injection lets things run a little cooler for a given amount of fuel (and, therefore, power -- works in both gasoline and diesel). Water injection was commonly used in very large piston aircraft engines on takeoff to get permit, typically, and additional 10 percent horsepower by cooling the mixture a bit to prevent detonation (knock). 10 percent doesn't sound like much, but in the big Wrights and P&Ws at the end of the line, 10 percent was 400 to 500 horsepower (really!). On the other hand, a really humid day reduces gasoline engine horsepower; the effect can be significant on takeoff and initial climb.

[Overmod]

The only thing about this is that nothing that 'reduces heat' in a diesel (compression ignition) engine can possibly make it run 'better'.

On big gas engines, pre-ignition (which is what 'knock' is) is a consequence of using last-century carbureted/throttled technology, where a hot cylinder or... too much compression... can cause the fuel mixture to ignite before the intended 'timed' point. Water injection can also help situations where the fuel is 'hotter' than usual (e.g., you're using nitrous as a 'high-energy oxidizer') and hence the brazent speed of the fuel at even properly-timed spark ignition is unexpectedly high... review the reasons why stoichiometric 'exactness' and homogeneity in the charge has not been 'preferred' in spark-ignition engines; you don't want a critical mixture in the cylinder)

Diesels are DIFFERENT. 100% of the combustion dynamics are related to the fuel injection -- speed, volume, turbulent mixing characteristics. The heat that makes the fuel react with oxygen is generated by compression, not by any 'point source', once the engine is running. The only result of 'decreasing' that heat, PER SE, will be to cause incomplete oxidation at some part of the fuel combustion cycle... this might show up as white smoke, soot, deposits, weird smells, etc. But it would CERTAINLY not show up as extra power...

Meanwhile, the density of water vapor is less than that of air at the same temperature, which is one reason weather does what it does. Therefore even an argument that the water injection helps 'cool' the intake charge better, and hence allows a higher density of oxygen in the cylinder charge, isn't a particularly thermodynamically correct one.

On the other hand, it can be readily understood that water in the intake charge will exert just the 'right' kind of pressure... which, let's not forget, is the PRINCIPAL point of burning stuff in one of these engines in the first place... on the piston, or on the power turbine in a jet engine, and in doing so it also limits permitted EGT levels and peaks (at just the other end of the engine from what jchnhtfd is talking about) -- which in turn can allow you to run increased turbo boost (with its concomitant higher back pressure) if you want.

I hate to keep bringing up that diesel stuff is different from gasoline stuff... but it is.