Naturally Aspirated (NA) V8 Engines

[MRC01]

You are forgetting stuff like the 6.0, 6.4, 6.2, 6.6, 7.3. Duty cycle. ...

Yep. Put differently: the larger displacement NA engine (or better yet, a diesel) is more likely to be designed to produce its max rated power continuously with decent efficiency. The smaller displacement boosted engine cannot; run it at max power continuously and it is likely to have issues with heat, reliability, etc.

One extreme example of this is motorcycles. Years ago I had a GSXR750 that made 110 HP RWHP on the dyno. But if you rode it hard in 2nd gear, after several minutes it would get heat soaked, lose power noticeably and run like crap. At that point you had to shift up to a taller gear and ride it easy for a while to get it cooled back down. My 2014 Mazda3 is the same, if you drive it hard in 2nd gear, after a while it will heat soak and lose power.

An opposite example is aircraft piston engines. The Lycoming O-360 is very common, 360 cubic inches rated at only 180 HP. Usually redlines at only 2700 RPM (which is more of a propellor limitation than an engine limitation). But it produces that rated power continuously, all day long with good efficiency.

 

[JTK]

I owned a 2017 Ram 1500 quad cab 4x4 with the ~300hp pentastar and now own a 2019 Ram 1500 classic crew cab 4x4 with the ~400hp hemi. For your typical day to day driving with just me in the truck I feel very little difference in terms of power, performance and economy. The V6 did do about 10-12% better in terms of average fuel economy. For sure the hemi sounds like a hemi and the pentastar sounds like a mad swarm of bees. There's times when you get on the hemi that it does give you an enormous amount of seat of the pants power, where the V6 is surprisingly good there too, but not quite as much.

To me, what are the advantages of the hemi? Like said, it's a simpler engine. V6s like the pentastar are a rather big job to replace coil packs, spark plugs, valve cover gaskets, etc..etc... The upper intake has to come off along with a lot of other things in the process.

On the hemi, all that is pretty much accessible as is.

I've got nothing against fewer cylinders, smaller displacement, multi-valves and turbo charging other than that is a lot more components which will equal more expense as time goes on. Especially for those of us blessed to live in the rust belt.

 

[2EHA]

Whats not impressive is a twin turbo/ blown multivalve headed V8 that can only manage 500HP, when a couple of teenagers can slap together an NA 2 valve cam in block pushrod mill that makes the same if not better HP and torque using 75 year old tech.

you and i both know the answer to that......the only 500hp boosted V8s on the market are either very old or deliberately crippled for emissions/warranty reasons.

OHV engines came into use around the same time as overhead cam designs. nothing is new there

 

[wpod]

I'm with you. And it goes beyond trucks.

A 3.5EB Mustang would rip!

A 5 liter turbo would rip even better.

 

[wpod]

All the stock V8's are watered down to the point of being really tame.

Uncork them and you'll never want anything else except maybe a big block.

Probably only half a dozen guys here have even experienced what a good running NA V8 is like.

Heres what you can put together for 10K in garage with all the right parts.

basically its a 500/500 mill on pump gas with an 800 RPM idle.

View attachment 55079

I have had V8 engines in My flat bottom drag boats and cars and pickups. Friends and Is have all built lots of big block hot rods. But I likes my flat bottom drag boats as my favorite , They are useless but fun boats

 

[UncleDave]

you and i both know the answer to that......the only 500hp boosted V8s on the market are either very old or deliberately crippled for emissions/warranty reasons.

OHV engines came into use around the same time as overhead cam designs. nothing is new there

I dont remember a gas turbo V8 that was impressive out of Detroit.

Wasn't saying anything was "new". Im pointing out a simple old design can make serious HP pretty affordably.

With access to high flow cats multivalve heads, multiport/ direct injection/ phased timing A 5-600 HP twin turbo V8 with either SOHC or DOHC is a lot of complexity for a result below what the average guys Chevelle puts out.

 

[UncleDave]

I have had V8 engines in My flat bottom drag boats and cars and pickups. Friends and Is have all built lots of big block hot rods. But I likes my flat bottom drag boats as my favorite , They are useless but fun boats

(if you cant tell) I love useless fun toys like that.

You got a sister? hehe

 

[UncleDave]

Yep. Put differently: the larger displacement NA engine (or better yet, a diesel) is more likely to be designed to produce its max rated power continuously with decent efficiency. The smaller displacement boosted engine cannot; run it at max power continuously and it is likely to have issues with heat, reliability, etc.

I wonder what the duty cycle being engineered for actually is for the various, but most specifically the 3.5 ecoboost.
There is no reason it couldn't be engineered for continuous max duty.

 

[Cujet]

So aside from a pleasant exhaust soundtrack, why would anyone choose a V8 over a turbocharged V6 IF you are given the option? Seems like the V8 is just the thirstier and more dated way of delivering power.

Many good points above, I won't repeat them.

I have 3 F150's.

2009 5.4L V8 4x4 super crew lariat 13 mpg
2011 3.5L V6 2x4 super crew XLT ecoboost 17-18 mpg
2018 2.7L V6 4x4 super crew XLT ecoboost 19 mpg

The 2018 is obviously the aluminum body. All trucks have similar enough performance. But the V8 is by far, the most pleasant. It is so much smoother on long trips. The 3.5EB sounds like a UPS truck and the engine really is not smooth. On 1000 mile trips, it actually starts to bother me. The 2.7 is much smoother and has a "race-car" like sound in sport mode. Love that. But it's 10 speed transmission does hunt up and down on hills, where the V8 just remains in 6th, content to loaf along.

In the end, I choose the V8 for epic road trips, due to the pleasant nature of a smooth and very quiet engine.

 

[Cujet]

So true, you can have Eco or Boost, just not at the same time.

That's not entirely so. My 2.7L ecoboost will operate at very low RPM with the gas pedal in the normal, highway cruise position, yet it's making plenty of boost, the throttle plate is nearly wide open, and providing very good economy. The driver is unaware of this.

When the driver asks for more power, what actually happens is a downshift, followed by increased RPM. It all feels seamless and normal, but the 2.7L engine is well tuned and it's superior economy is partially due to being able to operate in very low RPM modes, without falling short on torque, even though it's on the edge.

It's not like the old V8 days, where there is ample reserve torque at very low RPM.

 

[MRC01]

I wonder what the duty cycle being engineered for actually is for the various, but most specifically the 3.5 ecoboost.
There is no reason it couldn't be engineered for continuous max duty.

It would most likely require an increased capacity cooling system, among other things. With some cars, the sports or "R" version, or with trucks, the "towing package" sometimes has these kinds of upgrades that increase the engine duty cycle. Bigger or double radiators, an oil cooler, intercoolers for turbos, etc.

 

[stanlee]

The turbo V6s are more efficient and being turbocharged don't need much work to walk all over it's stock V8 counterpart. The cons are:
1. turbos...especially twin turbos add complexity (lots of piping on the intake and exhaust side, wastegates and electronic solenoids for boost control, intercooler/s), bypass valves etc. More complexity = more things to break (or to come loose/boost leak. Having owned MANY turbo cars it happens).
2. While technology has helped turbos don't last forever. We've gone from lucky to get 100k miles to maybe typically 200k miles but nobody wants that replacement expense and while a 100k car might be considered old most people with trucks consider that just broken in. And while they've got better with technology like twin scroll most manufacturers still size turbos small for low end tq which is good for drivability but not for heat/reliability (like a big turbo that lacks low end but makes power at low boost and run cool).
3. Less experience. While there may be decades of R&D in diesel and large truck turbocharging there isn't hardly the knowledge there is for building a V8. These turbos on non commercial gas engines really just became popular due to gas mileage stipulations. Mixed with direct injection there have been all kinds of issues to sort with reliability (see BMW N54 which I owned), deposits (see all before port injection began implemented with direct injection), LSPI which is a tuning issue trying to be masked with oil.
They tell you to buy the V8 based on partly valid reasons mentioned above (NA engine less complicated with less to go wrong, manufacturers not re-learning the wheel modernizing turbo use to today's efficiency and drivability standards) and partly dinosaur mentality (more cylinders, more displacement= better) with a little nostalgia thrown in for good measure (the V8 sound).
The turbo 6s are fine, just know you are STILL a part of the long term R&D and you sound like hot garbage driving by on the throttle. If you only keep your trucks for 100-150k miles then sounding like hot garbage is the only real downside.

 

[Blinker]

deleted

 

[Jetronic]

Do you think any of that could be solved by education? What I mean is, turbo motors, even today's with the advanced control systems and better lubes, can probably still benefit from some old-time turbo habits, such as.

- Letting the turbo cool down for a few min after being worked hard
- Changing the oil more often
- Being easy on the motor until things are up to temp
- Using a higher octane gas than recommended*
- Avoid excessive idling
- Make sure to work it hard now and again to keep the variable vanes moving properly

*Ford specs 87 octane for my truck, I don't think I'll ever be comfortable using that, certainly not if I plan on working the truck hard.

I think a lot of problems today are driven by a 'non car' userbase. I've mentioned this before. People today treat cars/trucks like appliances. They want to get in and go, stop to fill up with gas, and take the vehicle for maintenance sometime around when it tells them to. There's no mechanical sympathy or any understanding of how the vehicle works. They expect the vehicle to monitor itself, not let them do anything that would seriously hurt it, and tell them when something is wrong, end result, the vehicle lasts until the extended warranty is up.

I'd bet, you take 2 theoretical identical BITOG'ers give one a NA truck and one a turbo truck and you get the same life out of both, barring any massive engineering problems or faults in the vehicles.

Are they using VNT on gas trucks? It has always been a diesel thing except for Porsche.

 

[taurus3.5v6]

My 2020 Ram 1500 pick-up has the 5.7L HEMI V8 w/eTorque. It is the first V8 engine I have owned.

On this site (and others), there is a lot of discussion about the superiority of a Naturally Aspirated (NA) V8 engine over a turbocharged V6 engine in a light-duty pick-up truck. Or just in general. Whenever there is an option to choose between a NA V8 and a turbocharged V6 option, the overwhelming consensus is to choose the V8.

Hypothetically, if Ram had offered a turbocharged V6 option in this truck, I would have chosen it in a heartbeat. There is nothing special about the HEMI V8 in this application aside from the soundtrack it offers. IMO, there are more modern and more efficient ways to deliver the performance and capability that most V8's in this segment are able to deliver.

For example, I have driven F-150's with the 2.7 Ecoboost and the 5.0. I see no advantage to the 5.0 over the 2.7. The 2.7 delivers better performance for a daily driver with better fuel economy.

From a reliability standpoint, I also do not see any advantage to any of the current domestic V8 options (in the light-truck segment). Although the NA V8's are less mechanically complex, the HEMI has cam/lifter issues that have never been fully resolved. The GM 5.3L V8 with AFM has similar cam/lifter issues but to a lesser extent. Ford has oil consumption issues with the newest iteration of the 5.0 V8. Point is, I do not a significant reliability advantage by choosing the V8 option.

So aside from a pleasant exhaust soundtrack, why would anyone choose a V8 over a turbocharged V6 IF you are given the option? Seems like the V8 is just the thirstier and more dated way of delivering power.

Forced induction won't last as long. You have way, way more pressure and heat in the engine compared to NA. It doesn't matter what you do, somewhere that extra pressure and heat is going to wear the engine faster.

Natural aspiration is always better in my opinion. The modern trend of turbo charging everything for "efficiency" is complete "have your cake and eat it too" BS. There is no substitute for displacement. Enjoy your V8.

 

[supton]

Forced induction won't last as long. You have way, way more pressure and heat in the engine compared to NA. It doesn't matter what you do, somewhere that extra pressure and heat is going to wear the engine faster.

Natural aspiration is always better in my opinion. The modern trend of turbo charging everything for "efficiency" is complete "have your cake and eat it too" BS. There is no substitute for displacement. Enjoy your V8.

I'm sure that is true. But there's a few class 8 trucks out there who would like to have a word.

Furthermore... how long is required? Once an engine type can routinely go 500k... does it matter? Most trade out long before then, and the vehicles get junked for various reasons. Transmission, wiring, electronics, accident or just lack of perceived value.

While I agree there are probably no end of disposable cars today with a turbo and no intention of "lasting", I don't think they were designed to last any longer when they had a larger displacement NA engine either. IMO the OEM's know how long they want a car to last (at least to a minimum) and are quite capable of designing to that level.

 

[el Nuke]

same boring and torqueless experience as the 392 charger

I’m sure a reality exists where the 6.4L Hemi’s torque output is considered boring, but it is not a reality populated by many people.

In fact, it is likely so sparsely populated so as to be considered a fringe/edge case.

 

[dlundblad]

I’ll always take the NA gas engine. Keep it simple.

 

[DGXR]

Yes Ford's ecoboost line has proven robust. I can see only one benefit of the NA V8 over V6 turbo: the turbo engine will require more frequent service. I would also add that repair costs are potentially higher with a turbo engine but that depends on a few things and not always true. Personally I prefer the simplicity and proven durability of the NA V8 and would gladly sacrifice a few MPGs to get it.

 

[StillLearning]

I think when it comes to pickups, it's the simplicity that is the key to the N/A V8s, especially if they are planning to keep it for the long haul. Everything from having fewer parts and sensors to potentially replace, all the way down to the simplicity of the maintenance afforded by the N/A V8 all make for a better long term choice in my opinion.

In my area, I see a fair number of older "beater" trucks that aren't pretty, but are solid and likely have 2 - 300,000 miles on them. These are obviously older vehicles at this point, but I feel like they are still used and on the road because they are simple enough that the typical back yard mechanic can perform the basic maintenance and replace most parts as they fail.

It's my opinion that the newer generation of turbo charged small displacement trucks are less likely to reach that status of a "beater" before being retired because the cost of upkeep at dealerships/independent mechanics will be significantly greater for the work that people can no longer do themselves as easily.

Other than body damage, it tends to be when something major fails on an older vehicle that most people decide to junk it. I think a 15 year old truck with close to 200k miles on it needing a turbo replacement could be a more likely candidate for retirement, because "who knows how long the transmission might last." Whereas an N/A engine vehicle removes one of those major points of failure, making a repair more likely. You might be more willing to take your chances and say "That engine is has been a good engine, lets put another transmission in it and run it."