Since I can't ever answer anyone's questions when it comes to these trucks, I figure I may as well ask lots of them.
The Cetane/Octane question made me wonder why diesels can make so much more power than a gasser. If one were to start at an equal size engine with a turbocharger would a 6.6 L gasser be able to equal the power of a diesel?
Why so much more torque and easier upgrades?
Thanks in advance for the lesson.

Torque is just the fact the engine is designed to make maximum power at 2500-3000 rpm. If you made a gas motor that made peak power at 3000RPM, it would have huge torque too.

Diesels are more efficient by design and there is more energy in a gallon of diesel than gasoline.

Another big reason a Diesel will make more power than an equivalent gasoline engine is that as long as there is air to burn you can inject fuel during the power stroke. In a gasser you mix air and fuel in a somewhat set ratio (usually 14.7 to 1), then during the compression stroke you light it off with a spark and you get one big bang slapping the piston back down at or near top dead center (hence the term “piston slapper” for gassers) creating your power stroke. On a Diesel you can have an almost infinite air to fuel ratio, as the air is pumped in and compressed it heats up near top dead center fuel is injected and begins to burn, and continues to burn as long as fuel is injected and air is available to burn (hence the term “oil burner” for the diesel). Basically all this means is you’ve got a big bang pressing down on the piston in a gasser for very few degrees of crankshaft rotation where in a diesel you’ve got fuel burning pushing down on the piston for much longer during the power stroke.

there are more btu's available in diesel than gas,also diesel expands at a different velocity than gas when burned.stroke on a diesel is longer than a gas motor,hence the big torque numbers.

They're not.

You can make both engine types make any amount of power you want. We can thank GM marketing for the nice power our trucks have.

Power is torque x RPM (and a constant to correct units). If marketing calls for 310hp, and your engine design redlines at 3200 RPM due to how the fuel burns, then you have to size it for high torque to make up for the low RPM's.

If diesels had better power to weight ratio, then you'd see them in racing and light aircraft. Imagine a modern 402 ci gasoline engine with 4-valves per cylinder and an intercooled turbocharger. It would have way more power than 310hp.

Diesels make power with less fuel, at the expense of weight and cost. Their power density is getting alot better, but that's true for gasoline engines too.

Power accelerates a vehicle. Engine torque at the crankshaft is only half the picture. Wheel torque accelerates the vehicle...and there's a transmission in between. Higher RPM means a lower gear, which means more wheel torque. To know which comes out ahead, look at horsepower.

Crank throw and stroke are selected for an optimal piston speed, not to increase torque. The lower RPM dictates that the stroke be longer to achieve optimal piston speed.

Cit1991, you are very smart. And I for one appreciate your knowledge being shared on this board. I enjoy learning about my new truck (my first diesel) and your knowledge is awesome.


They're not.

You can make both engine types make any amount of power you want. We can thank GM marketing for the nice power our trucks have.

Power is torque x RPM (and a constant to correct units). If marketing calls for 310hp, and your engine design redlines at 3200 RPM due to how the fuel burns, then you have to size it for high torque to make up for the low RPM's.

If diesels had better power to weight ratio, then you'd see them in racing and light aircraft. Imagine a modern 402 ci gasoline engine with 4-valves per cylinder and an intercooled turbocharger. It would have way more power than 310hp.

Diesels make power with less fuel, at the expense of weight and cost. Their power density is getting alot better, but that's true for gasoline engines too.

Power accelerates a vehicle. Engine torque at the crankshaft is only half the picture. Wheel torque accelerates the vehicle...and there's a transmission in between. Higher RPM means a lower gear, which means more wheel torque. To know which comes out ahead, look at horsepower.

Crank throw and stroke are selected for an optimal piston speed, not to increase torque. The lower RPM dictates that the stroke be longer to achieve optimal piston speed.

They're not.

You can make both engine types make any amount of power you want. We can thank GM marketing for the nice power our trucks have.

Power is torque x RPM (and a constant to correct units). If marketing calls for 310hp, and your engine design redlines at 3200 RPM due to how the fuel burns, then you have to size it for high torque to make up for the low RPM's.

If diesels had better power to weight ratio, then you'd see them in racing and light aircraft. Imagine a modern 402 ci gasoline engine with 4-valves per cylinder and an intercooled turbocharger. It would have way more power than 310hp.

Diesels make power with less fuel, at the expense of weight and cost. Their power density is getting alot better, but that's true for gasoline engines too.

Power accelerates a vehicle. Engine torque at the crankshaft is only half the picture. Wheel torque accelerates the vehicle...and there's a transmission in between. Higher RPM means a lower gear, which means more wheel torque. To know which comes out ahead, look at horsepower.

Crank throw and stroke are selected for an optimal piston speed, not to increase torque. The lower RPM dictates that the stroke be longer to achieve optimal piston speed.

Actually, diesel is coming up as a major power player in the future. Forget the fact you can make huge power at low RPM. That just shows efficiency. My engine has just tuning and an exhaust, and it can make 450rwp (~500+ crank) at just 2400rpm. Hard to do with a gasser.

As electronic fuel controls (common rail) gets more and more advanced, engine efficiency and power will continue to climb, as will power output.

Why such huge power off "low-grade" fuel? Boost. While cars are relegated to meager amounts of boost due to detonation, diesels LOVE da boost. Hot rod Cummins are running 120 PSI of boost. You can't touch that with gasoline. And you have the whole compression issue. Compression makes power all across the powerband, and even the wimpiest diesels run more compression than alcohol race engines. Starting ante is about 16:1 for diesels, and it goes up from there.

But the biggest surprise is how much power you make on the stock motor. My engine (certainly not the most powerful) makes 200 more RWHP than stock, just by tuning and exhaust. You cannot do that with any other engine in production. And without hurting the mileage! There is nothing like it in the gasoline community.

:grd:

Actually, diesel is coming up as a major power player in the future. Forget the fact you can make huge power at low RPM. That just shows efficiency. My engine has just tuning and an exhaust, and it can make 450rwp (~500+ crank) at just 2400rpm. Hard to do with a gasser.

As electronic fuel controls (common rail) gets more and more advanced, engine efficiency and power will continue to climb, as will power output.

Why such huge power off "low-grade" fuel? Boost. While cars are relegated to meager amounts of boost due to detonation, diesels LOVE da boost. Hot rod Cummins are running 120 PSI of boost. You can't touch that with gasoline. And you have the whole compression issue. Compression makes power all across the powerband, and even the wimpiest diesels run more compression than alcohol race engines. Starting ante is about 16:1 for diesels, and it goes up from there.

But the biggest surprise is how much power you make on the stock motor. My engine (certainly not the most powerful) makes 200 more RWHP than stock, just by tuning and exhaust. You cannot do that with any other engine in production. And without hurting the mileage! There is nothing like it in the gasoline community.

:grd:
Ain't it great! Last time I saw stock engines this de-tuned from the factory was the diamond-star turbo motors from the early 90's.

There are three main reasons Diesel can have more power:

1: Higher compression ratio. Work performed is related to expansion.
Higher compression ratio means more work. Indeed this is why twin-crank
opposed piston engines can be more efficient than single-crank motors.

2: Higher energy density in the fuel. More work per unit volume. Here
in CA we have a almost-certainly-illegal move by the legislature to change the energy density of gasoline to _reduce_ the energy per unit volume so as to increase the tax burden per mile driven!

3: Most commonly overlooked... no throttle plate. That throttle plate
in gas motors uses up a stupendous amount of energy. This one is
a subtle issue due to the way testing is done, but that throttle plate
uses up 10% of the power in a gas engine.

Since I can't ever answer anyone's questions when it comes to these trucks, I figure I may as well ask lots of them.
The Cetane/Octane question made me wonder why diesels can make so much more power than a gasser. If one were to start at an equal size engine with a turbocharger would a 6.6 L gasser be able to equal the power of a diesel?
Why so much more torque and easier upgrades?
Thanks in advance for the lesson.

Ain't it great! Last time I saw stock engines this de-tuned from the factory was the diamond-star turbo motors from the early 90's. Yes the engine is detuned but as much as you're saying. The larger exhaust is vital to prevent heat issues. GM could go to a larger exhaust would help some but the big limiter is emissions. Look at the hurdles the LLY guys are facing due to the EGR.

Diesel has a lot more potential for power because of some key things: 35% energy efficiency vs. gasoline's 25%. (as stated above) Expansion through the entire power stroke (as stated above.) The leaner you run diesel, the cooler so pump more air.

Diesels are more about reliablility and efficiency though. A diesel will probably never beat a top fuel dragster. But try to drive an 12 second camaro 36000 miles in a year with only fuel filter and oil changes.

A turbo charged 6.6L gas engine would probably make more power but less torque then the 6.6L Duramax makes. But the mpg would be about 1/2 of what the Diesel gets.

Race engines make 2,000+ horsepower, and some times much more then that by adding turbochargers, blowers, laughing gas, and what not. But the fastest truck in the world is run on diesel. It is an 1957 Chevy with twin jet engines that run on diesel, and it produces 25,000 horsepower. The truck uses 80 gallon in one run, the top speed is about 375 mph. I don't thing there is any vehicle that runs on gas that can produce that kind of power.
The owner of that truck also has a triple engine Peterbilt truck capable of producing 36,000 horsepower at the speed of sound. I believe it runs on diesel as well, but I'm not sure.

Since I can't ever answer anyone's questions when it comes to these trucks, I figure I may as well ask lots of them.
The Cetane/Octane question made me wonder why diesels can make so much more power than a gasser. If one were to start at an equal size engine with a turbocharger would a 6.6 L gasser be able to equal the power of a diesel?
Why so much more torque and easier upgrades?
Thanks in advance for the lesson.

Hey,

Look up the specs for the 400 Pontiac, or a 403 Olds, and see how they compare, after all they were 6.6L

Take care

Will

the turbo charged gas engine will make more hp because you can turn it 9 grand with the right stuff. can you imagine running 6500 rpm pumping 120 psi into a duramax.

A turbo charged 6.6L gas engine would probably make more power but less torque then the 6.6L Duramax makes. But the mpg would be about 1/2 of what the Diesel gets.

Race engines make 2,000+ horsepower, and some times much more then that by adding turbochargers, blowers, laughing gas, and what not. But the fastest truck in the world is run on diesel. It is an 1957 Chevy with twin jet engines that run on diesel, and it produces 25,000 horsepower. The truck uses 80 gallon in one run, the top speed is about 375 mph. I don't thing there is any vehicle that runs on gas that can produce that kind of power.
The owner of that truck also has a triple engine Peterbilt truck capable of producing 36,000 horsepower at the speed of sound. I believe it runs on diesel as well, but I'm not sure.

Yeah the guy and his sons that own those trucks their last name is Shockley if I'm correct. Shockwave Shockley is what they call him. I guess they could go faster with that old Chevy (like 400mph or so)but the Dad won't let his son who drives that one.

There are three main reasons Diesel can have more power:

1: Higher compression ratio. Work performed is related to expansion.
Higher compression ratio means more work. Indeed this is why twin-crank
opposed piston engines can be more efficient than single-crank motors.

2: Higher energy density in the fuel. More work per unit volume. Here
in CA we have a almost-certainly-illegal move by the legislature to change the energy density of gasoline to _reduce_ the energy per unit volume so as to increase the tax burden per mile driven!

3: Most commonly overlooked... no throttle plate. That throttle plate
in gas motors uses up a stupendous amount of energy. This one is
a subtle issue due to the way testing is done, but that throttle plate
uses up 10% of the power in a gas engine.
1. A higher compression means that the engine is more efficient in converting thermal energy into mechanical, but not by alot. There is not that much more power by having higher compression, i.e. not double the power/energy. I think I was told for gasoline engines, about 6 L in size, you'll get about 5 hp increase for every 1 point increase in compression you run.

2. I'm not sure about the thermal energy released comparing diesel to gasoline, but that doesn't really matter. It is the speed that the fuel burns. Diesel burns slower than gas, and therefore it cannot burn efficiently at a high rpms. Even if you could spin a diesel engine 7000 rpms, its my guess, that the piston would be almost halfway down before the fuel was finished burning, losing alot of the potential thermal energy that was pushing on the piston. You would be wasting alot of the potential hp/power. I believe alcohol has lower energy than gasoline, but alcohol has oxygen in it, and therefore you can burn more fuel, and make more overall power than gasoline. Why do drag racers run alcohol? It is the amount of fuel an engine can burn efficiently that determines how much power it can make. The faster an engine runs, the more air/fuel it consumes, the more power it can possibly make. Gasoline has this advantage, I think the most implrtant difference.

3. The lack of a throttle plate in a diesel means that with every stroke, the diesel is getting a full 18:1 compression (normally aspirated, with turbo, it's higher), therefore diesel is very efficient in converting thermal energy into mechanical energy. A gasoline engine has to have a throttle plate to keep the air:fuel ratio about 14:1, at all times, by limiting (obstructing) air intake flow to match fuel usage. By having the throttle plates at part throttle, the gasoline engine operates at a lower effective compression, like 3-4:1, even though the engine static comp ratio is 10:1 . Therefore , the gas engine, by design, is not as efficient as a diesel in converting thermal energy into mecahnical energy. You can't run a gas engine real lean, because you don't get an efficient burn, flame, that is initiated by a spark. With a diesel, it burns spontaneously, so you can run it real lean, and benefit from maximum compression, to "extract" as much energy as possible.


There are turbo 2 liter gas engines making 450 hp or more. They can run at high rpms, burning fuel efficiently, converting that thermal energy into mechanical energy.

I think a gas engine will always make more power than a comparable diesel engine, whether it is normally aspirated or turbocharged.

2. I'm not sure about the thermal energy released comparing diesel to gasoline, but that doesn't really matter. It is the speed that the fuel burns. Diesel burns slower than gas, and therefore it cannot burn efficiently at a high rpms. Even if you could spin a diesel engine 7000 rpms, its my guess, that the piston would be almost halfway down before the fuel was finished burning, losing alot of the potential thermal energy that was pushing on the piston. You would be wasting alot of the potential hp/power. .

Diesel burns slower... Therefor the diesel burn pushes the piston for a longer period of time! Hence, more torque, also the reason for the need for the higher compression. Yes RPM is required for HP but when you can make 1000 lb of torque at 2500 RPM out of 6.6
ltr motor - all is good!
Gasoline goes "POP" and the burn is all over... The piston gasoline motor will spin faster, but the right diesel will always make more power! IE Jet Turbine! :muahaha: :muahaha:

On final thing. I think the reason why diesel engines often have turbochargers, is that because if they were normally aspirated, they would not be that powerful, and not as many people would buy them. To sell alot of diesel trucks, you have somehow supercharge them to make them marketable.

Diesel burns slower... Therefor the diesel burn pushes the piston for a longer period of time! Hence, more torque, also the reason for the need for the higher compression. Yes RPM is required for HP but when you can make 1000 lb of torque at 2500 RPM out of 6.6
ltr motor - all is good!
Gasoline goes "POP" and the burn is all over... The piston gasoline motor will spin faster, but the right diesel will always make more power! IE Jet Turbine! :muahaha: :muahaha:

I think you got that backwards. You want the burn to be as fast as possible. Ideally, you would not have the burn start until the piston just reached TDC, and then the burn would be instantaneous, and then the piston would start to move down, under the full force of the burned fuel "increased gas pressure" extracting as much energy as possible. The longer the burn is, the less efficient you can extract the energy. The slower the piston speed doesn't mean as much. A slower piston speed will allow more thermal energy to be absorbed by the head. cylinder wall, piston itself. The faster the piston speed, the more friction generated in the rings/piston/wall interface. I'm not sure where the advantage is.

I'm sure you can make over 1000 lbs torque from a turbo chargerd 6.6 gas engine. If you really want to know the true facts, give Gale Banks a call, I'm sure he'll know the limitations of turbocharged gas and diesel engines.

Here is a 2.5 L gas turbocharged engine, you can buy right now, from subaru.

http://wardsauto.com/ar/auto_subaru_fuji_dohc/

2.5 L, 300 ft-lbs, 300 hp. Factory stock, no modifications. Lets see, upsizing to 6.6 L, then the engine would be 800 ft-lbs, 800 hp.

Gasoline has 125,000 megajules of energy per gallon. Diesel has 143,000 megajules per gallon. Diesel has a higher flash point which requires the higher combustion pressure to ignite compleatly. Any one wonder why a diesel only uses a 1/3 of what gasoline vehicle of equal displacment uses to just idle? This is why Diesel will always be superior to a gas motor in terms of efficency and fuel consuption at a given power level. Also diesel has a lubris quality in comparison to gasoline hence longer life of them engine. A turbo and diesel is a match made in heaven. The auto manufactures learned there lessons long ago on how the higher compression that the turbo provides helps ignite all of the diesel fuel available at the time of ignition. A diesel loves heat (not steel melting temps though).

Diesels will always be more "fuel efficient" then gasoline engines, the spark that is used to ignite the fuel in gassers robs the potential energy of the fuel being ignited by compression heat rather then the thousands of volts used to create a spark. Also diesels will become more fuel efficient with the use of a turbo charger, the turbo is not only to make more power or a maketing device. Since diesels require a high fuel to air ratio the turbo charger is there to shove air in the engine to help it burn. Ever see semis when they come off from a dead stop and they get on the pedal a huge black cloud of soot shoots out? Thats the fuel computer telling the engine to add more fuel in the eninge to spool up the turbo because there is not enough air to burn. Thats why our trucks shoot out black smoke when we get on the throttle, no air from turbo lag so bad burn.

I think you got that backwards. You want the burn to be as fast as possible. Ideally, you would not have the burn start until the piston just reached TDC, and then the burn would be instantaneous, and then the piston would start to move down, under the full force of the burned fuel "increased gas pressure" extracting as much energy as possible. The longer the burn is, the less efficient you can extract the energy. The slower the piston speed doesn't mean as much. A slower piston speed will allow more thermal energy to be absorbed by the head. cylinder wall, piston itself. The faster the piston speed, the more friction generated in the rings/piston/wall interface. I'm not sure where the advantage is.

I'm sure you can make over 1000 lbs torque from a turbo chargerd 6.6 gas engine. If you really want to know the true facts, give Gale Banks a call, I'm sure he'll know the limitations of turbocharged gas and diesel engines.

:funnypost

you said it! Diesel burns slower... Not instantaneous like a gas motor. I am not trying to argue, just giving my bone head, book learned, opinion. And I don't believe you could get 1000 lbs of torque from a 6.6 ltr gas motor at 2400 RPM :D :chillpill

The fuel/air mix in a gasoline engine does not burn all at once. That would be a detonation. It makes noise you hear as ping. The shock wave also destroys the gas boundary layer between the gas and metal boundaries of the combusion chamber. That's why it can lead to overheating...higher heat transfer.

It still burns faster than diesel though...but not all at once.

If it burnt real fast, all cars would have ignition timing at TDC.

Setting off the flame at two places across the chamber makes the burn complete faster for a given flame speed. That's why dual plug engines need less advance and still make more power and have better efficiency.

Diesel fuel takes a few seconds to heat up and burn after the injection starts. Then you get a fast pressure rise...that's why they clatter. High cetane fuel lowers the delay and reduces clatter.

Diesels are more efficient because diesel is more dense (about the same BTU/lb, more BTU/gallon), and because of the high compression ratio.

Turbo's have a downside in gasoine engines...the need to lower CR to stop detonation. Diesels can't preignite or detonate, since the fuel isn't there until the compression stroke is about finished. So no CR penalty.

You want the burn to be fast, but not all at once. Find a way to reduce the delay and get diesel to burn faster, and you've found the holy grail....then we can spin 'em at 6000 RPM and double the HP.

:funnypost

And I don't believe you could get 1000 lbs of torque from a 6.6 ltr gas motor at 2400 RPM :D :chillpill
Well, I just looked in my 5.0 mustang book, and there is a guy with a 400 ci stroked windsor (about 6.6 L ), with a procharger. 1800 hp. Does the 1/4 at 190 mph. It didn't state what the torque was at 2500 rpm,s, but it has to be up there.

Gale Banks will sell you a crate 366 ci (6.0 L) twin turbo engine, with 900 ft-lbs torque ( I bet if it was 6.6 L you could get 1000 ft-lbs). Granted it is at 4000 rpm's, but I bet if you put a shorter duration cam in it ( I don't know why you would want to do that) , I bet you could get the torque peak down in the 2500 rpm range.

http://www.bankspower.com/twin-turbo-performance.cfm

Turbo's have a downside in gasoine engines...the need to lower CR to stop detonation. Diesels can't preignite or detonate, since the fuel isn't there until the compression stroke is about finished. So no CR penalty.

Then why did Isuzu/GM design the duramax with 18:1 compression, down from the 22:1 in the older 6.5 GM TD? I believe it's the same reason why you lower the static compression on a supercharged gasoline engine, to be able to intake more air/fuel, to make more power safely.

Then why did Isuzu/GM design the duramax with 18:1 compression, down from the 22:1 in the older 6.5 GM TD? I believe it's the same reason why you lower the static compression on a supercharged gasoline engine, to be able to intake more air/fuel, to make more power safely.
Probably NOx.

cit1991,

you may be right, but before I bought my truck, I was looking into buying a diesel suburban, with the 6.5 (from the south, i.e. little rust), and then having the engine possibly rebuilt for more power, performance. In the several companies that I researched, when they rebuilt the 6.5 for more power, they lowered the compression, so I think there is something to that. I never contacted them. There is one place in Mich, somewhat close to me, that is into marine engines, that will sell hopped up 6.5 TD's for GM vehicles, and charge you a core charge or exchange. They'll even replace the engine, do the labor, for you. I can't remember the name at this time. I'm sure they know this stuff inside and out.

Here's the dealer/builder.

Peninsular diesels. They sell a performance rebuild kit to lower the compression to 18:1

http://www.peninsulardiesel.com/compare.htm


http://www.peninsulardiesel.com/marine%20kit.htm

2. I'm not sure about the thermal energy released comparing diesel to gasoline, but that doesn't really matter. It is the speed that the fuel burns. Diesel burns slower than gas, and therefore it cannot burn efficiently at a high rpms. Even if you could spin a diesel engine 7000 rpms, its my guess, that the piston would be almost halfway down before the fuel was finished burning, losing alot of the potential thermal energy that was pushing on the piston. You would be wasting alot of the potential hp/power. I believe alcohol has lower energy than gasoline, but alcohol has oxygen in it, and therefore you can burn more fuel, and make more overall power than gasoline. Why do drag racers run alcohol? It is the amount of fuel an engine can burn efficiently that determines how much power it can make. The faster an engine runs, the more air/fuel it consumes, the more power it can possibly make. Gasoline has this advantage, I think the most implrtant difference.



You are partly correct! But there are several Cummins that run between 7,000-8,000 rpm, and they are making gobs of power up there in the higher rpm range. Also; Banks is working on a GM truck with a highly modded Duramax that will run 5,000+ and I'm thinking I heard it is closer to 6,500 rpm red line. But then there are gas engines running 10,000-12,000 rpm. And I have a nitro fueled truck that run at 43,000 rpm, it is about 5 cc and puts out almost 4 hp.

The direct injection diesels have lower compression than the IDI engines, such as the 6.5 and 6.2. The main reason is that you can't run as much boost with higher compression as low. The 6.5 was a low boost engine, I believe it maxed out at about 7 lbs. The guys that drop compression to 18:1 on the 6.5s can run alot more boost without damaging the engine than they could with stock compression.

There are quite a few of us here making 1000-1500 fpt at 2500rpm on our street trucks that still get out on the hwy and average about 14-19mpg doin it (driving 55-75mph). I can't recall to many gassers you can get to that point as daily drivers that meet those peramiters let alone get up to that torque level with it still being a actual street drivable vehicle. All vehicle have their place though. It just isn't such an easy place to compeat in with a gasser any more. The energy available in diesel fuel is just much higher than gasoline no matter what you do. Thats the reason some of these 3 cylinder diesels over in Europe are getting 80-120mpg. Less fuel needed to get to a certain power requirement.

Thsi has been a good thread. I like these discussions.

marcdeluca "The direct injection diesels have lower compression than the IDI engines, such as the 6.5 and 6.2. The main reason is that you can't run as much boost with higher compression as low. The 6.5 was a low boost engine, I believe it maxed out at about 7 lbs. The guys that drop compression to 18:1 on the 6.5s can run alot more boost without damaging the engine than they could with stock compression."

exactly what I thought.

Super Diesel "There are quite a few of us here making 1000-1500 fpt at 2500rpm on our street trucks that still get out on the hwy and average about 14-19mpg doin it (driving 55-75mph). I can't recall to many gassers you can get to that point as daily drivers that meet those peramiters let alone get up to that torque level with it still being a actual street drivable vehicle. All vehicle have their place though. It just isn't such an easy place to compeat in with a gasser any more. The energy available in diesel fuel is just much higher than gasoline no matter what you do. Thats the reason some of these 3 cylinder diesels over in Europe are getting 80-120mpg. Less fuel needed to get to a certain power requirement."

I actually agree with you on everything. I believe the diesel is easier to get that power out of an engine, and still be very streetable. 1000-1500 ft-lbs is ALOT. However, do you use your N2O and propane to get there? Or just Diesel? I would think the vast majority of people on this forum don't have 1000 ft-lb engines, and even less in the general pick-up diesel population. Most people who build megapower gas engines ( from what I read in car mags) don't intend on running it at 2500 for max output, as the gas engine is I think better suited for 5000-7000 rpms, where it can shine and make a lot of power. I think a gas engine could be set up to make max torque at 2500 rpms, but why? In addition, I would think most of these megapower gas engine vehicles are purpose built racing machines. How much power can you utilize in a street car, weighing 3500 lbs, as opposed to pulling a 15000 lb trailer. Again I believe you can make a 6.6 L gas engine, purpose built for turbo, about 7:1 compression or maybe less, to get max power, but it's going to be expensive, and the engine will never be as efficient as a diesel for a street driven vehicle. Even though I think you could make the engine very streetable, what are you really going to use such an engine like this other than for racing?

One other comment has to do with fuel efficiency. Yeah, the diesel fuel liberates more energy, but I think that is the lessor of the advantge that a diesel has. I think the main advantage is that it operates under maximum dynamic compression all the time, getting the most efficient conversion of thermal energy to mechanicl all the time, as opposed to a gas engine, with throttle plates severely limiting dynamic compression at partial throttle, and not converting as much energy to mechanical. From my experience with gas and diesel engines, it seems the fuel mileage advantage really shines when pulling no load, or a light load. Once I start towing something heavy, and I'm more in the throttle, I think I saw less of an improvment in fuel mileage comparing my gas vehicles to my diesels. Maybe it was just me.

Back to the initial question.

question made me wonder why diesels can make so much more power than a gasser. If one were to start at an equal size engine with a turbocharger would a 6.6 L gasser be able to equal the power of a diesel?
Why so much more torque and easier upgrades?
Thanks in advance for the lesson. The gas trucks are normally aspirated, engineered to be efficient as possible under these circumstances. You could get a turbo system (expensive), intercooler, but you may need to rebuild the engine with lower compression and different cam to really take advantage of the turbo. It's going to be expensive, and you'll end up with a vehicle that will suck gas. I would think it will be very powerful, but overall there would be no advantage over a diesel other than some gas stations not havin diesel, which I don't see really as a problem. Paxton / procharger / etc. sell bolt on superchargers for truck gas engines, but again, the engine was never designed from the beginning to be supercharged. I investigated that option with my suburban, about $4000 I think. I don't think it would help my fuel economy despite what the manufacturers claim.

In contrast, new diesel pick-ups come standard with the needed groundwork to build off of. The engine is designed from the ground up to be run with a turbo. The truck already has an intercooler. It's easy to change a couple things and boost your power up alot. The diesel is more efficient by design than a gas. Perfect for towing, everyday driving, fuel expense. The diesel option is more expensive to begin with, but still alot cheaper than the total cost to really convert a gas engine over to turbo assist.

Diesel is the only way to go.