One more V6 vs V8 ?

[Cliff s]

Maybe this will shed some light on the V6-V8 controversy.

The gasoline engine is basically a heat engine(it generates heat from the fuel).

The only way to increase the HP is to either flow more air through the engine
or consume more fuel(to a point). Increasing the compression ratio is another factor,
as it releases more heat from the fuel. Turbo-charging and Super-charging do this.
They raise the effective compression ratio.

At a given RPM the more displacement a engine has the greater the output.
So to get the same HP out of a smaller engine you must spin the engine faster
to obtain the same quantity of air flow.

The only other way you can increase HP is to reduce pumping losses, modern
engines are engineered to minimize these losses, so little can be gained here.

Efficiency is a compromize of camshaft timing, fuel flow and ignition advance.
The computerized fuel injection systems constantly adjust the last 2 for maximum
efficiency. The VVT engines can also adjust the first(cam timing).

The VVT engines adjust the camshafts for maximum output at the higher RPMs
so little is gained at the normal driving speeds. The engine is more sensitive to
cam timing at higher RPMs do to the increased air flow.

Cliff s

 

[Iowa4Runner]

Originally posted by Cliff s
The only way to increase the HP is to either flow more air through the engine or consume more fuel(to a point). Increasing the compression ratio is another factor, as it releases more heat from the fuel. Turbo-charging and Super-charging do this. They raise the effective compression ratio.

Turbo-charging and Super-charging does raise the effective compression ratio, but that's not where the real power gains come from. The increased mass fuel/air flow into the engine is what makes the extra power.

 

[Northof49]

Turbo-charging and Super-charging does raise the effective compression ratio, but that's not where the real power gains come from. The increased mass fuel/air flow into the engine is what makes the extra power.

Actually, it would be more accurate to say forced induction effectively increases the displacment of an engine, rather than the CR. The compression ratio- key word ratio, stays constant no matter how much A/F mix you are cramming into the cylinders.....

 

[Iowa4Runner]

Actually, it would be more accurate to say forced induction effectively increases the displacment of an engine, rather than the CR. The compression ratio- key word ratio, stays constant no matter how much A/F mix you are cramming into the cylinders.....

When talking about power gains, I would agree that it'd be more helpful to somehow calculate an "effective displacement" instead of talking about effective CR. Effective compression ratio is important and has it's place in the engineering world, it's just not a good way to describe forced induction power gains.

 

[02SE]

I can't believe I just read all 7 pages of this thread. :awais:

 

[Hitman]

The VVT engines adjust the camshafts for maximum output at the higher RPMs
so little is gained at the normal driving speeds. The engine is more sensitive to
cam timing at higher RPMs do to the increased air flow.

Cliff s

I think you missed the point of an engine designed with variable valve timing.... The idea is to provide decent low-end torque in combination with good high-end power. Most engines with variable valve timing have two cam profiles that come into play at different rpm.

Did you ever hear an old muscle car with an aftermarket cam in it that barely idles while stopped at a light? Did you ever wonder why it sounds like it is about to stall? The cam is set up to make max power in a specific rpm range, which means the cam timing quality at idle will suffer. Modern engines with variable valve timing attempt to provide a smooth, quiet idle/decent low-end torque, and good upper-rpm power as well.

The day when we see cars without camshafts is probably not too far in the future. We'll have electrically operated valves that are infinitely variable, providing the best of both worlds. The main reason we don't see them now is the limitations of the 12V electrical system in modern vehicles. That's due to change soon too, which means electrical valves will not be far behind....

 

[Iowa4Runner]

The main reason we don't see them now is the limitations of the 12V electrical system in modern vehicles. That's due to change soon too, which means electrical valves will not be far behind....

Electrically actuated valves would be cool, although F1 type pneumatic actuation might be even cooler. Can you expand on the limitations you spoke of regarding 12V systems? Are vehicles heading toward a different voltage standard? I haven't anything about this but would be really interested in hearing more.

 

[Hitman]

Electrically actuated valves would be cool, although F1 type pneumatic actuation might be even cooler. Can you expand on the limitations you spoke of regarding 12V systems? Are vehicles heading toward a different voltage standard? I haven't anything about this but would be really interested in hearing more.

Yes, the days of 12V systems are numbered. Look for 42V system soon.... With the amount of components that rely on the electrical system of a modern vehicle these days, the higher voltage systems will be sorely needed.

I'm sure if you do a quick web search, you'll find plenty of information. Just search for 42V electrical systems.

Edit:

Keep in mind that there will be a transition to the 42V systems. Because of all the components designed to work on a 12V system, expect the early vehicles to have a dual voltage system. After all, a 12V headlight bulb wouldn't last too long on a 42V system...

 

[MicaBlue03]

42V is 12X more power!

I'm not sure why the proposal is to use 42V instead of 48 or something like that. It may be a safety thing--42V used to be a limit where direct shock hazard to humans was thought to begin (and extra warnings and precautions were necessary).

The reason to use higher voltages is to deliver higher power more efficiently. For a given current capacity and wire (conductor) area, 42V will deliver more than 12 times more power (wattage) to handle a high power load like a fast valve actuator or suspension adjustor. Higher voltage can allow for smaller wires or lower loss over the same size wire or both. The central factor that power goes up with the square of voltage, so 3.5X the voltage equates to over 12X the power.

Wire diameter goes linearly, though. A wire to carry a given amount of power at 12V would have to be 3.5X the diameter of one that carried 42V (not counting the insulation). Copper is heavy and expensive, and thick cables are cumbersome to install. However I suspect that 42V components will also be more expensive initially. This may be a rather long and gradual transition.

 

[Hitman]

Re: 42V is 12X more power!

I'm not sure why the proposal is to use 42V instead of 48 or something like that. It may be a safety thing--42V used to be a limit where direct shock hazard to humans was thought to begin (and extra warnings and precautions were necessary).

The 42V system is supposedly the actual working voltage level of these future sytsems. In other words, a 12V system actually works at about 14V, not 12V.

If you multiply 14V times 3, you get 42V. Maybe that's where it comes from? I'm not sure........

 

[Iowa4Runner]

Re: 42V is 12X more power!

I'm not sure why the proposal is to use 42V instead of 48 or something like that. It may be a safety thing--42V used to be a limit where direct shock hazard to humans was thought to begin (and extra warnings and precautions were necessary).

The reason to use higher voltages is to deliver higher power more efficiently. For a given current capacity and wire (conductor) area, 42V will deliver more than 12 times more power (wattage) to handle a high power load like a fast valve actuator or suspension adjustor. Higher voltage can allow for smaller wires or lower loss over the same size wire or both. The central factor that power goes up with the square of voltage, so 3.5X the voltage equates to over 12X the power.

Wire diameter goes linearly, though. A wire to carry a given amount of power at 12V would have to be 3.5X the diameter of one that carried 42V (not counting the insulation). Copper is heavy and expensive, and thick cables are cumbersome to install. However I suspect that 42V components will also be more expensive initially. This may be a rather long and gradual transition.

Interesting, although there are a couple things I should point out. At a given current, a 42 volt system will deliver only 3 times (not 12) the power of a 14 volt system. At DC, watts = volts x amps. And at DC, a conductor's ability to carry current depends on it's area, not diameter.

Thanks for the info...

 

[Iowa4Runner]

Yes, the days of 12V systems are numbered. Look for 42V system soon.... With the amount of components that rely on the electrical system of a modern vehicle these days, the higher voltage systems will be sorely needed.

I'm sure if you do a quick web search, you'll find plenty of information. Just search for 42V electrical systems.

Edit:

Keep in mind that there will be a transition to the 42V systems. Because of all the components designed to work on a 12V system, expect the early vehicles to have a dual voltage system. After all, a 12V headlight bulb wouldn't last too long on a 42V system...

Can you imagine how bright that would be? Forget about Silverstars, I'm running 42 volts to my headlights! :thumb:

 

[MicaBlue03]

Increased electrical power in vehicles

Iowa4Runner, you bring up a good point, and my reasoning was incorrect. Power (for loads that are reasonably resistive) does goes up with the square of the voltage, but that doesn't hold if the current is limited by, say, wire size. And that is indeed the case in vehicles. What can I say--I should know better than to post late at night!

I looked around a little and discovered that calling these new systems 42V invites some confusion. The battery voltage will apparently be 36V and the "operating" voltage will be 42V. Each is 3X the existing 12/14V systems. Since we generally describe existing systems as 12V it seems we should describe the new ones as 36V, but I guess the horse is already out of the barn on that one.

BTW, I saw one report of a luxury sedan from Toyota (not sold here) that uses a 42V system now.

 

[Iowa4Runner]

Re: Increased electrical power in vehicles

Iowa4Runner, you bring up a good point, and my reasoning was incorrect. Power (for loads that are reasonably resistive) does goes up with the square of the voltage, but that doesn't hold if the current is limited by, say, wire size. And that is indeed the case in vehicles. What can I say--I should know better than to post late at night!

I looked around a little and discovered that calling these new systems 42V invites some confusion. The battery voltage will apparently be 36V and the "operating" voltage will be 42V. Each is 3X the existing 12/14V systems. Since we generally describe existing systems as 12V it seems we should describe the new ones as 36V, but I guess the horse is already out of the barn on that one.

BTW, I saw one report of a luxury sedan from Toyota (not sold here) that uses a 42V system now.

I noticed the same thing about the system voltages being referred to differently. Maybe there will be a new battery technology introduced around the same time and there won't be the typical lead-acid ~15% difference between nominal and charging/running voltage.

 

[Hitman]

Re: Re: Increased electrical power in vehicles

I noticed the same thing about the system voltages being referred to differently. Maybe there will be a new battery technology introduced around the same time and there won't be the typical lead-acid ~15% difference between nominal and charging/running voltage.

Although it may not be as high as 15%, the charging voltage will always have to be higher, which also means that the operating voltage will be greater as well.

I suspect the early vehicles will use 3 batteries (in series) very similiar to the 12V battery used today. This will allow a series/parallel hook-up that would make a dual-voltage electrical system easy to accomplish.

 

[TechWrench]

Re: Re: Re: Increased electrical power in vehicles

Although it may not be as high as 15%, the charging voltage will always have to be higher, which also means that the operating voltage will be greater as well.

I suspect the early vehicles will use 3 batteries (in series) very similiar to the 12V battery used today. This will allow a series/parallel hook-up that would make a dual-voltage electrical system easy to accomplish.

Oh great, now there will be three batteries to replace instead of one, and three times the weight!! Not to mention the increase in alternator output required to keep em charged up.

Progress, I love it.

 

[Iowa4Runner]

Re: Re: Re: Increased electrical power in vehicles

Although it may not be as high as 15%, the charging voltage will always have to be higher, which also means that the operating voltage will be greater as well.

Oh absolutely, I was just throwing out possible reasons for why the new systems are referred to as 42 volt instead of 36 volt. The upper number seems pretty well fixed, where as the lower number may change with newer technologies.

I suspect the early vehicles will use 3 batteries (in series) very similiar to the 12V battery used today. This will allow a series/parallel hook-up that would make a dual-voltage electrical system easy to accomplish.

That wouldn't surprise me, but I'd imagine the more ambitious manufacturers could economically make a straight 42 volt system and use DC-DC switchmode converters for things like lights that will be 12V for a while.

 

[Hitman]

Re: Re: Re: Re: Increased electrical power in vehicles

Oh great, now there will be three batteries to replace instead of one, and three times the weight!! Not to mention the increase in alternator output required to keep em charged up.

Progress, I love it.

Are you ASE certified? The reason that I ask is because the ASE newletter from a few months ago had a really good article on the 42V electrical systems.... Do you get the newsletter in the mail?

 

[TechWrench]

Re: Re: Re: Re: Re: Increased electrical power in vehicles

Are you ASE certified? The reason that I ask is because the ASE newletter from a few months ago had a really good article on the 42V electrical systems.... Do you get the newsletter in the mail?

Nope. I, by choice, got out of the automotive service line quite some time ago. I liked repairing vehicles, and was considered good at it, but in my area the pay and long term benefits weren't enough to keep me. I went 'postal' and work in maintenance. I still do most of my own work on my vehicles, but now 'fix' computers and other mail processing equip. Given the advanced state of computer and electronic controls incorporated in todays vehicles, I would think todays auto technician would have a much more challenging job than what I routinely was faced with. I am going to have to do some research into the future of 42V automotive exectrical systems, I think it will be interesting.

 

[arra]

Okay, I started this thread, maybe It's time to end it. I purchased a 2005 SR5 V6 Silver on Friday, 12/31/04 30 g's out the door. All the usual options, moonroof, spoiler, etc. Here are my reasons I chose the V6: Better gas milage, performance-wise not that big of a difference for 95% of daily driving, very little towing and the big thing is the option of 2 or 4 wheel drive. Maybe it's just me, but I like the handling of the vehicle better in 2wheel drive than 4 wheel. Please don't ask me to elaborate on the 2 vs. 4 wheel, it just seems the vehicle is a bit more responsive in 2 wheel rather than 4 wheel. Just my humble opinion. Got to tell everyone, I agonized over this V6 or V8 decision for quite sometime, but I think I made the right decision. So far loving the 4R. What do I hate about it? I find myself parking in the last spot in parking lots, always looking outside to make sure no one is messing around the vehicle and majorly upset because today it got rained on. Thanks to all on this forum for the responses given on this thread. Wait a minute, there's somebody outside standing around my truck. Gotta go -----