Poll: Torque & Horsepower

[eia430]

Demon Xanth, yeah bottom line is power does cost money no matter how you look at it. It is generaly cheaper to go big displacement low tech than small displacement high tech. Where big displacement low tech losses big time is the area of handleing. Hence big displacement low tech american cars do well in one area drag racing, a straight line. In other areas like autocrossing and road racing, turbocharged small displacement (lighter) motors fare better than big displacement low tech brutes. There's a time when a club will do you well, there are other times when you should invest in a katana(sword.)

 

[Demon-Xanth]

Me Zog, me like oak tree. Oak tree bash squirrel good.

Well, that's my opinion on engines. I like them big and stupid most of the time

Edit: is a 24V (pushrod) turbocharged straight six considered high tech if it's a 5.9L diesel or is that still low tech?
(245HP+460Lb/ft, 3250RPM redline)

 

[eia430]

demon, pushrod ??? I wonder why a modern engine designer would still opt for pushrods? unless it's just to reduce cost. Pushrods increase the recipocationg mass of the valve train effectively lowering it's rpm limit where you start to experience valve float (where the valve no longer has the time to fully close before it is forced open again. I would have to say low tech on that 24v v-6 because performance is a secondary consideration to cost. As for that disel... I don't know if it's low or high tech... it could have advanced technology for the diesel class of motors. But again since it is diesel they opted to place as primary consideration things other than performance otherwise they would have picked a gas motor.

 

[eia430]

Demon, well I used to autocross with the SCCA and the porche car club (even though my car is not a porche) so I'm biased towards lighter smaller motors. V-8's don't do so well in our autocross events, corovettes get eaten for lunch on a daily basis by just about every other car there. But then again when we roadcourse the corovettes do very well.... you can have your oak tree to bash the squirrel, I'll use my arrow shaft..

 

[HaVoC]

If you wanna talk about displacement you can look at the big rigs with their 500+ cubic inch engines. They make only "300-400HP" but MASSIVE amounts of torque, maybe 1200 ft-lbs. HP is fine and all, but torque makes for the VULGAR DISPLAY OF POWER. BTW, you ever seen those 18-wheeler cabs without a trailer? They can get up and go pretty quick. All that torque with no weight holding it down.

BTW, speaking of HP, I was in a German science museum and they had this HUGE piston from a marine Deisel engine. It was about 15' tall with a 4 foot diameter, solid steel. The engine it came from made around 12,000 HP at 200 RPM! All that through torque, not RPM.

 

[Demon-Xanth]

EIA: umm, read it again. It's a straight six diesel. the valve train is not the limiting factor in it's redline. (it's the combustion speed of the fuel)

 

[PG]

You guys shouldn't knock american V8 engines so much. I really like the current GM V8's. Ford and Chrysler have a history of just creating new engines all the time, but GM refines the engines they have. They just keep getting better all the time. The latest GM V8's seem to have more HP per liter than their competition, and cars like the Corvette and Camaro are pretty fuel efficient as well. I think that they are rated in the mid 20's for highway cruising. That isn't much worse than say a midsized 4 door car with a V6.

PG

 

[PG]

That cummins tubo diesel is a good motor. It's the only 24V diesel in pickups right now that I know of. I'd say it's pretty high tech for a pickup diesel. The Ford Diesel has more torque, but it's a V8, and has a very different design. The cummins in Dodge trucks looks just about like the semi engines, just smaller. I think the straight 6 engine design for diesels is a stronger design. I read somewhere that the cummins engine has about double the main bearing area as the Ford's diesel motor. That should give you longer engine life, but both engines should last a good 300K miles easy.

PG

 

[geno]

<< the valve train is not the limiting factor in it's redline >>


The valve train may not be the limiting factor but it definitly plays a big part in the engines redline

 

[Demon-Xanth]

Genocide: The engine doesn't even feel rough when near redline. Generally in gas engines the valvetrain is the limitation, but in diesels the fuel's combustion is usually the limitation. DOHC on a diesel would be like a Geforce2 Ultra on a P75... pointlessly expensive. If the fuel's combustion rate were much quicker (like gasoline!) then the valvetrain would be the limit and most likely around 5000RPM.

 

[geno]

Like I said, most of the time it is, but I wasn't sure what it was in the case of that engine.

 

[eia430]

Demon, as I mentioned... performance was not the top consideration in that motor or it would not have been diesel to begin with. Genocide was right... I was looking at it as two different motors one v-6 gas the other diesel. In the case of the diesel the redline limitation would be because it's diesel. Although are you sure it is because of flame front(burn speed)speed limitations? I would imagine that at 22 to 1 compression the whole mixture will be quite near spontanious combustion point(hence a glow plug heat retention is enough to ignite.) Although I'm not qualified in diesel mechanics I was leaning more toward injection speed as the limiting factor. It is mechanical to begin with, plus the viscosity of the fuel itself, plus the fact that it has an extremely narrow window to be injected. Unlike a gasolene motor that sprays fuel when there is negative pressure in the chamber and it has the period between full stroke travel, the diesel only has time between near full compression stroke when the fuel starts burning then all the fuel must be injected while the combustion is occouring. That's a much smaller time window than a gasoline motor has to inject it's fuel in the chamber. Either way, you're right, the pushrod would not be the rpm limiting factor. In a gasoline motor (I thought the v-6 was) it would be most of the time.

 

[Demon-Xanth]

Diesels do sponateously combust. glow plugs are used to get the engine started (although in this case it's a manifold heater), then it's just the heat and compression that fires the cylinders from there on. In the case of this engine &quot;performance&quot; is measured with a 9000lb trailer attached

And in my post, I was referring to a single engine when I made the statement about the high or low tech. (unless you're mistaking the VTEC-GM3.1 comparison)

 

[LAUST]

Chevy now actually has a good diesel going into the new 2001 series it's a Duramax made by Isuzu Which is all made in Ohio so it is still an American plant.. The one thing that was really amazing about this Diesel was that is does have HP in a diesel 300 actually where most of the time it's all torque and no horse in a diesel. I think the HP has allot to do with the Direct Injection desighn.. Not sure though I'm still a gas motor man Gotta have more power and torque.... I guess if I was hauling allot and going long distances though I would be pretty interested in the Diesels

 

[eia430]

Demon... Hmm.... I thought that besides first creating (electricly heated) enough heat to fire I thought the secondary function of a glow plug was to be the localized heat flash point. The cylinders walls, roof, and piston all have very good heat sink and can't really even approach combustion temps, the coil itself is able to get to beyond combustion temp and retain it long enough to be the trigger point on the next cycle. No matter, either way it's just a technicality in our discussion

 

[eia430]

Laust, all diesels are &quot;direct injection&quot; unlike gasoline motors where the air-fuel mixture is pulled into the chamber with a vacum from the piston down stroke. Diesel fuel is injected when the piston is on the upstroke nearing peak cylinder pressure. The fuel is being burned as it is injected into the chamber. I think it is injected at something like 1800psi of pressure vs around 43psi for gasoline fuel.

 

[Redneck]

eia430, a little bit off on the diesel fuel injection pressures. The fuel injectors on the Cummins dont even open until 4000 psi, and nominal pressures are in the 18,000+ range.

 

[brassmonkey7]

it's hard to roast tires off of a car without the proper torque,
does anyone have any old Mopar muscle cars?

 

[eia430]

Redneck, youch.... I was guessing hence &quot;like 1800&quot; but I had no idea I was off by that much.... oh well live and learn. Thanks for the info.

Brassmonkey, there's the old small weak 4cyl method of roasting tires called the fly wheel energy storage system just rev that motor up (storing engergy in the flywheel and other rotating mass of motor, then drop that clutch!! (hopefuly not the trannie too)

 

[Redneck]

eia430,I'm sure you know more about gassers than I do The injection pumps on diesels are IMO technical marvels. You could mistake a inline pump for a minature engine if you only glanced at it.

 

[eia430]

Redneck, you seem to know about diesels, perhaps you can enlighten us on this question. Are glowplugs single function? is it only used to electricly heat up to begin the process? Or does it serve dual purpose. Is it still needed to retain heat to be a flashpoint for the next cycle? after the electrical current to the coil is turned off?? In other words if the coil were to be &quot;removed&quot; once the diesel engine was running will the combustion process still occour? or is the coil needed to maintain the process??

 

[DABANSHEE]

&quot;: is a 24V (pushrod) turbocharged straight six considered high tech if it's a 5.9L diesel or is that still low tech?&quot;

24 valves on a pushrod straight-6, that works out at 4 valves per-cylinder, that's a hell of a lot of pushrods running up the side of the engine, it hardly leaves any room for inlet/exhaust ports on that side of the head. It also means a hell of a lot of rockers up top. Are you should its not a 12 valve head or a OHC head, Demon-Xanth? I know it is possible for there to be a 4 valve per cylinder engine with pushrods, someone developed such heads for Chev blocks (or were they Windsor blocks) about 15 years ago (I remember a thing about them in a magazine), where each pushrod worked 2 valves, but its really not practicle (hence no more has been heard about it), its much more likely that its a conventional 12 valve straight-6 or if it's does have 24 valves its got a OHC head.

&quot;. DOHC on a diesel would be like a Geforce2 Ultra on a P75... pointlessly expensive.&quot;

Hey Demon, BMW, Mercedes &amp; Toyota (&amp; I think Fiat too) all make DOHC diesels, but mainly for the European market, where diesel is half the price of petrol. They are used in upmarket cars for refined smoothness &amp; quietness, like the Turbo\deisel BMW 525, etc.

 

[Demon-Xanth]

iirc, the rockers are mounted on shafts. Check your local Dodge dealer for a look-see

 

[PG]

Glow plugs are only for when the engne is cold and it's very cold outside. Normally if the air is warm enough to start with, it gets so hot after compression that if you inject the diesel fuel, it ignites automatically. When the engine and outside air are cold enough, a diesel wouldn't even start without glow plugs. The glow plugs are only activiated when necessary and are not like spark plugs. The glow plugs are to heat the air only.

The Dodge Cummins has no glow plugs. It has a grid in the intake manifold that heats the air when the engine is cold and the outside air is too cold. I belive that the engine computer will control when the gird is turned on and off. I think that even in cold weather the grid will be turned off after the engine gets warm enough.

PG

 

[Redneck]

eia430, I aint't an expert on diesels but I should be able to explain what glowplugs do(or the intake heater on the Cummins ISB does).

Diesels depend on the heat created by compression of air to ignite their fuel. When it gets cold enough, the compression cannot heat the air enough to ignite the fuel. AFAIK glow plugs are there only to heat the air enough t to ignite the diesel. They do not actually ignite the diesel. Once the engine has reached operating temps (ie the air in the cylinders is warm enough ignite the fuel) the glowplugs are shut off.