General DieselDiscussion about diesels in general. All brands are welcome, please refrain from brand wars. Discussions about types of diesel fuel also go here.
quite true. however i did want to point out that we need to be sure to compare apples to apples. it takes a whole lot less energy to spin a centrifugal supercharger than a much physically larger roots-type blower. a whole bunch.
a centrifugal supercharger is a very close comparison to a turbo because it is half way to identical. the energy needed to drive the gear multiplication box is where the energy gets robbed by the supercharger. the turbo by comparison has much less mass to accelerate and therfore takes seemingly less power to operate.
just a thought.
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Travis
'03 F350 Dually, 6.0, Supercab, longbed, 4.10 LS, sport pkg, extremely RED, STRAIGHT PIPED, SCT Xcalibrator, full guages
- Job1 programming, Harpooned, Skweeker Mod, Zoodad Mod
- Did that thing that you're not supposed to talk about
'79 Bronco, 468cid Ford 460 marine motor, C6/NP205
Previous -'99 F250, Rg Cab XLT, 7.3/6spd, 3.73
Project truck
- '96 Cummins, 215hp/5spd, Diprocol guages, Plate & AFC full fwd, hi-capacity external lubrication system
To add: 2 1/2T axles, 46" goodyears, etc.
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...were mechanically driven with a clutch to drop out when the purpose was no longer needed as in the case of 2 12V EMD's and 1 V8-EMD engine....
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really? were they roots type blowers?? i'm just wondering how that wouldn't cause problems if the blower vanes no longer were driven. i guess i'm looking at it as if the vanes weren't turning than they would basically block the intake air flow and the turbo would have to force the charge through the vanes.
or, is it the case that since the clutch disengages while running, so that means that the intake charge keeps the blower vanes turning, but really just kinda "coasting"????
i guess i could see that better if it were a centrifugal compressor/blower, but doing that to a positive displacement roots-type seems strange to me.
but a lot of things seem strange to me.... [img]/ubbthreads/images/graemlins/biggrin.gif[/img]
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The EMD engines use a centrifugal blower/supercharger (since it performs both functions) which is driven either by the engine or by the exhaust turbine with an overrunning clutch which, when the exhaust flow comes up at higher loads, will disengage from the engine and drive the compressor at turbine speed instead.
For whatever it's worth, positive displacement pumps of any kind are generally only used in the small end of a range, be they air compressors, supercharger/blowers, or water pumps, etc., and centrifugal usually takes over above a certain volume in industrial settings.
The supercharger robs power from the crankshaft to generate the boost thus decreasing fuel efficiency. Why take power from the crank that can go to the flywheel when you can just use free energy in the exhaust?
Nope......Driving a turbo causes exhaust back pressure which in turn causes higher cylinder pressures on the exhaust stroke...It's not free energy, but the increase in power outweigh the losses if properly designed.
It's not entirely "free" but it does not take as much power from the engine crank shaft to drive it as the power you are getting out the compressor side. Most of the power from an exhaust driven turbocharger is taken from the extra energy of the exhaust gases and not the engine crank shaft. Now a mechanically driven supercharger takes 100% of its energy from the crank shaft and therefore is not an "energy scavenger" like the exhaust driven turbo.
Birken
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I was gonna say, so what! If I have 10 lbs of exhaust backpressure and I add 12 lbs of manifold pressure on the intake stroke, am I not offsetting the increased backpressure with increased intake manifold pressure?
Just in case anyone asks, it takes 38 HP to drive the 'blower' on the 2 cycle engine. At least that is what I was told by a factory rep many years ago.
So if you think about it, the old double 'O' 92 series had 430 hp. After it had newer injectors, a redisgned block, new design cylinder head,new design cylinder liners, and a 'bypass blower', The HP rating went to 450 and eventually 475, then to 500.
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95 F250,XLT, 4WD, Auto Trans,bbshimmed,synthetic trans oil,4:10 gears ,Truck Trunk ,Nerf Bars ,crome Mud flaps, Aux. trans cooler, front diff. drain plug. External trans.filter, trimmed snorkel. American wheels water temp guage, front fuel tank mod,Warn Manual hubs,Putman class 4 hitch 181k mi.
It is said if you sit by the river and watch the water flow by long enough, your enemies will pass by. This I believe to be true. It is also possible to watch your loved ones pass by as well.
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The supercharger robs power from the crankshaft to generate the boost thus decreasing fuel efficiency. Why take power from the crank that can go to the flywheel when you can just use free energy in the exhaust?
Nope......Driving a turbo causes exhaust back pressure which in turn causes higher cylinder pressures on the exhaust stroke...It's not free energy, but the increase in power outweigh the losses if properly designed.
It's not entirely "free" but it does not take as much power from the engine crank shaft to drive it as the power you are getting out the compressor side. Most of the power from an exhaust driven turbocharger is taken from the extra energy of the exhaust gases and not the engine crank shaft. Now a mechanically driven supercharger takes 100% of its energy from the crank shaft and therefore is not an "energy scavenger" like the exhaust driven turbo.
Birken
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I was gonna say, so what! If I have 10 lbs of exhaust backpressure and I add 12 lbs of manifold pressure on the intake stroke, am I not offsetting the increased backpressure with increased intake manifold pressure?
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Too much junk/toys to mention, ever changing due to too getting bored too quickly. I need a 10 step program!
Want to call? I'm in the book. Want to argue....First explain the square root of negative one....lol
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If I have 10 lbs of exhaust backpressure and I add 12 lbs of manifold pressure on the intake stroke, am I not offsetting the increased backpressure with increased intake manifold pressure?
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whoa, i need a turbo like that!! does more work than the energy it uses?!?!?!? [img]/ubbthreads/images/graemlins/eek.gif[/img]
i knew all that "conservation of energy" stuff they told us in school is a bunch of boo-crap [img]/ubbthreads/images/graemlins/phoney.gif[/img]
CTD, you might wanna patten that turbo...
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Travis
'03 F350 Dually, 6.0, Supercab, longbed, 4.10 LS, sport pkg, extremely RED, STRAIGHT PIPED, SCT Xcalibrator, full guages
- Job1 programming, Harpooned, Skweeker Mod, Zoodad Mod
- Did that thing that you're not supposed to talk about
'79 Bronco, 468cid Ford 460 marine motor, C6/NP205
Previous -'99 F250, Rg Cab XLT, 7.3/6spd, 3.73
Project truck
- '96 Cummins, 215hp/5spd, Diprocol guages, Plate & AFC full fwd, hi-capacity external lubrication system
To add: 2 1/2T axles, 46" goodyears, etc.
[img]/ubbthreads/images/graemlins/cool.gif[/img] Centrifugal superchargers operate in the same fashion as a turbo; however, the energy to spin the compressor is taken from the rotating output energy of the engine's crankshaft as opposed to exhaust gas. For this reason turbochargers are ideally more efficient, since their turbines are actually heat engines, converting some of the heat energy from the exhaust gas that would otherwise be wasted, into useful work. Superchargers use output energy to achieve a net gain, which is at the expense of some of the engine's total output.
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2002 F350 Red PSD Auto SC/LB SRW 4x4 Tymar Intake 4"Dual Exhaust DI 6 position twisty knob BTS 4R100 Vegistroke V3
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The supercharger robs power from the crankshaft to generate the boost thus decreasing fuel efficiency. Why take power from the crank that can go to the flywheel when you can just use free energy in the exhaust?
The supercharger's boost also does not change based on load, only with engine RPM.
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Period. [img]/ubbthreads/images/graemlins/biggrin.gif[/img] Well said.
The big one that is one here is that again, the supercharger boost does not change based on load, only on engine RPM, so that really sucks for diesel engines that redline at 1800 RPM. With a turbo, you could feasibly be making maximum boost at any RPM you want (depending on setup, turbo map, etc). This means that you don't need to be at redline to get maximum boost from the charger.
Also, IN GENERAL (this isn't absolute, so no one needs to get on here and prove me wrong with one exceptional example) the supercharger makes power at the expense of efficiency. Typically, you can see loads from a super heading towards 25% of NA engine rating. There is a net gain of horsepower, but at a loss of total efficiency.
A turbo, on the other hand, generally creates a net GAIN in efficiency, because the only load it places on the engine is an amount of exhaust backpressure, which is generally in the 2 to 8 percent total NA rating range.
So, in an industry where one half of one mile per gallon can mean millions on the bottom line of a big enough company, power with efficinecy dominates the day.
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'99.5 PSD 6 SPD 4x4 Extended Cab long Box F-350
AFe Stage 1 intake, Marinco Block Htr Plug Mod., Hutch in-Tank Pickup Mod, $10 AIC, Walker BTM, Edge Juice with Attitude, and that is all, FOR NOW!!! Next mod = Regulated Return???
Old Truck - '95 PSD 5 spd 4x4
Haulin' a 11.5' camper, an '85 Bayliner Capri 20' boat w/ Chevy 350, and a flatbed w/ two big quads.
2004 Grizzly 660 Yamaha (For Me)
2004 Polaris 500 HO (For the Wife)
Spokane, WA
"I don't ride bulls, but I have fought some men" Hank Williams, Jr.
"Sie vie pacem, para bellum" (if you want peace, first prepare for war...)
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F350 Red PSD Auto SC/LB SRW 4x4 Tymar Intake 4"Dual Exhaust DI 6 position twisty knob BTS 4R100 Vegistroke V3
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