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Low end grunt as it relates to modern engines

27K views 128 replies 24 participants last post by  Litos 
#1 · (Edited)
Everybody is familiar with the conversation where you are trying to describe how powerful an engine "feels like" as far as low end grunt, right? Hopefully the point of reference is fairly reasonable, but admittedly it can be wildly subjective. The shape of the powerband means everything. I would consider the powerband shape of a GM Vortec 7400 as a good example of a "generic v8 engine"...medium rpm range and torque spread fairly evenly throughout that range. There's no real surprises...no shortage of low end torque, no overly hot top end, and a very mild rise in torque in the 3000-4000 rpm range. You don't have to "get to some rpm" to enjoy its best because it gives more or less the same amount of brute force no matter where you hit it in rpm. The Vortec 7400 is the quintessential example of a broad powerband v8 with real ruler flat torque output, imo.

So the exercise is how do modern performance v8 engines (yes, I included a Pentastar v6, just for additional perspective) compare as far as output between 2000-2500 rpm (pretty much what you would consider "low end torque" on most engines)? What does the engine "feel like" in that particular range? Does it feel like a 300 hp engine, 350 hp, 400 hp?... I'm not suggesting that 300 hp is actually occurring at that rpm. I'm suggesting this is about what you would expect out of a garden variety v8 engine that carries that rated hp number in that low rpm torque region.

The results are pretty much what I expected, but some may find surprising to see quantified here! :) Most of all, it really does illustrate how modern engines don't really "feel" like classic engines as far as horsepower values, unless you are expressly exploring some rpm's. If you are just rolling around town at modest rpm, these engines are more tame than their hp spec suggests. Also note that a higher hp spec engine isn't always going to feel "stronger", at least not right out of the gate. The ranking can surprise you.

On the low end,...

-a 320 hp GM Vortec 8100 feels like a whopping 383 hp engine

-a 390 hp Hemi 5.7 feels like a demure 312 hp engine

-a 415 hp Ford dohc 5.0 feels like a very nonathletic 265 hp engine

-a 305 hp Pentastar v6 feels like a very uninspiring 206 hp engine (not at all "v8-like power" as far as the 300 hp number)

Gearing is the key to how these modern engines even maintain a respectable demonstration of output on the low end. 1st gear is critical to let these engines quickly dig out to their respective and proper powerbands. Another way to think about it, is this (383/312/265/206 hp) is more like how these engines would be rated if they weren't being saved by the higher rpm liveliness (the Vortec 8100 being the exception to this and an example of just the opposite, for its clear lack of top end extension). Cams on modern performance cars are more high end oriented than they ever have, eh?

The point is especially poignant as far as the "305 hp" Pentastar v6. Unless you are frequently exploring 3500 rpm and above, it is not "v8-like" in the slightest. It is not far removed from any other "old school" 200-ish hp v6. That's not to say that nobody should ever pick the v6 engine tier for this car. If you seek a v6, then you should get a v6, but you don't get it because the hp rating seems v8-caliber as far as a hp number. It is just not the case, unless you are explicitly intending to keep the rpm on boil as you drive, and even then, it is only a modest example of v8 power, anyway.

Thoughts? Objections? Outrage?...

 

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#2 ·
Coyote 5.0 is definitely a high revving beast.

doesn't make too much grunt down low - those engines need to be kept up over 4500rpms......
 
#3 · (Edited)
Even the Hemi isn't blowing any doors off down low. If the Challenger was only marketed as a 312 hp v8 with 4000 lbs of weight, it would never even get out the door. That is too little hp and too much weight. Therein is the realization that if you are rolling along in town in 3rd/4th/5th gear and expect to suddenly dig out from 2000-2500 rpm with heavy throttle,...that's just barking up the wrong tree because you are essentially feeling a 312 hp engine at work at that point. There's nothing "wrong" with the engine when it doesn't blast off on a dime in that scenario...the driver is simply not leveraging the engine's powerband properly.

Even the chart above suggests that you need a whopping 8.1 L of v8 displacement to pull off like that with low end torque and actually feel like a "380 hp engine".
 
#4 ·
(yes, I included a Pentastar v6, just for additional perspective)
You, cruel, cruel man... :lol:

Thoughts? Thanks for putting this in graph form where things are so much easier to visualize. I'm not surprised at all because this trend isn't new, though. I remember reading almost 30 years ago a magazine article that compared two BMW 3.0s, one from the '80s and the other from the '70s. The discussion was all about driving impressions and how then modern engines had more HP up in the power band, and felt very elastic, but had lost character and grunt in the process, the seat of the pants feel.
What you describe here is the same thing only much later and applied to V8s. Engineers make engines rev more freely and find enough torque down low that the cars perform great and are usable and docile around town, but don't 'feel' that powerful. I've seen this come up too when people drive a 1970 Challenger and a modern one back to back.
IIRC, one writer put it that way: "modern cars, with their elastic powerbands and tall gearing, feel pacy, not quick". Track numbers tell another story, but most cars never see a track.

Tell you what, there's obviously no going back, just like with the electronic nannies and MDS, as we've discussed before. We need more mileage, less pollution and, let's face it, cars that are drivable by people who never learned how to handle power and who freak out whenever the rear wheels break loose. But I personally deplore the change: I'm not particularly interested in track results, more in real world impressions. Some cars feel powerful and satisfying, while others are fast, but leave you bored at the wheel. Modern cars tend to be the latter.
CVT is just another facet of that trend toward the electric engine. More efficient, less entertaining and involving. Eventually the driving aspect of personal vehicles will disappear completely, I'm sure of it; it's mathematical.

I was playing with my Hemi the other day (it's the 5.7/340 HP), in Drive and at low rpm to observe the MDS's behavior. And I was surprised by the amount of torque available down low. There is no real 'need' to rev the engine like I normally do. It's just so smooth and different from what happens above 3,000 or so that the engine feels peaky and somewhat gutless, unfortunately. And again, the enjoyment of driving (if I am to keep my driver's license anyway) comes in great part from tractor-like behavior and low end grunt for me, so this isn't exactly it. Don't get me wrong, I love the Hemi.

I've considered the 5.0 before, and its performance is appealing, but that 7,000 rpm redline so admired by some tells the story. For a daily driver, I'll stick to the old wisdom that 'there's no replacement for displacement'. Technology can fool you some, but not reinvent physics, and if I had the scratch I'd get a 392 precisely for that reason, not for the 20's and the options.
 
#5 ·
Another interesting point not to be missed is just how radically different a "320 hp" engine can feel, not for knowing its displacement. If it happens to be 8.1 L of displacement as in the Vortec, that modest hp rating is still enough to utterly clobber what modern 390 and 420 hp engines are doing on the low end. Surprisingly or not surprisingly, the lowest rated v8 in this sample is actually the hardest puncher when it comes to low end output, and not by just a "bit" more. It is the brutal schoolyard bully that knocks down all comers, takes their lunch, and doesn't even get to losing his breath. This Vortec is dropping like a rock on the top end, and that is reflected in the modest hp rating it gets. Even a 320 hp v8 can do some serious damage, if the displacement is right. ;)
 
#6 ·
Besides tradition and other more or less rational issues, the answer to why people pick V8s over V6s (please God, not another one of those threads!), all other things apparently equal, is in this thread.
 
#7 ·
Besides tradition and other more or less rational issues, the answer to why people pick V8s over V6s (please God, not another one of those threads!), all other things apparently equal, is in this thread.
So what you're saying is, V6's are inferior in every way, and are only driven by women and should only be sold as rental cars? Wow.

That's a very strong statement you made there, how I wish someone would tell me why they would ever choose to drive the V6. We even have graphs now proving they suck.

:lol:
 
#9 ·
Adding weight to the car is another test for low-end torque. Load 4 guys into my R/T and it doesn't seem to notice, but load 4 guys to my buddy's brand new Charger SXT and it acts just a little more sluggish.
 
#10 ·
Yet another way... When I lived in Europe, where big engines are rare, they used to say that while for most people a fast car gets around corners quickly, like a fighter jet, to Americans, fast is more like a 747, where the power is felt from all the incredible mass it moves. It's part gut feeling, part cerebral kick. I only guessed what that meant until I got my first V8, but I never owned anything like a big block. I can't do the small, high-revving, peaky motors anymore. The effortlessness is where it's at. For me. And it's low-end grunt.
 
#11 ·
Before this turns into a v8 vs v6 discussion, I just want to get one more thing out about the Hemi 5.7 (especially in the context of the 5-spd auto). I think it is fairly well understood that it is geared relatively on the tall side between how 3rd gear will cross the 1/4 mi and the axle ratio. Just the first 3 gears matters greatly as to what you can expect to get out of the available output from 2000-2500 rpm. Here's why...

1st gear is the shorty out of the bunch in the NAG1, for sure. It doesn't matter if the Hemi is not its strongest on the low end...you more likely have to worry about not having enough tire traction to move 4000 lbs of car than not enough torque at the rear wheels. Between the literal gear ratio, the torque multiplication at load, and the slip to further allow the easy dig out from 2000-2500 rpm, there is no issue here of not enough torque. The moment it gets to 3000+ rpm, this combo is like a powder keg going off to pin the redline.

2nd gear in the NAG1 is considerably taller. It would be more like "2 and a half" gear compared to other cars. However, it is not as bad as it sounds. You still have torque multiplication at load and slip to a higher rpm when you put liberal throttle in to work that fluid coupling. The car will pick up speed relatively quickly and enter the 3000 rpm gateway readily, after which it takes to air with great energy and speed.

3rd gear in the NAG1 is where you likely encounter a double whammy. It's a tall step up from 2nd, and tall enough to carry the car to a speed that the manual has to grab 4th to do same. The double whammy part is that 3rd is where the torque converter clutch comes into effect. If you are just rolling along and then suddenly take-off in 3rd, that clutch is likely going to be engaged. So it is direct mechanical connection, no torque multiplication, and no slip to step off with some rpm. Then you REALLY feel how tall 3rd is. If you are trying to dig out from 2000-2500 rpm, remember you only have that "312 hp engine" at work through a tall gear and hauling 4000 lbs. You bet, it is going to be a long wait before you see 3000+ rpm, where the Hemi can start piling it on. If you aren't aware of the mechanics in play while it is going on, you may very well experience it as a bog or the engine simply not responding to the throttle. It isn't. It's just all that Hemi can offer up on the low end through a tall gear and 4000 lbs of car. If you don't want to experience that, don't use 3rd trying to dig out of 2000-2500 rpm. You either go to 2nd, or you really drop the pedal so the torque convertor clutch disengages and you can get some torque multiplication + rpm slip. In 3rd, that is a priority while at low rpm. The math dictates it has to be a dog, otherwise.
 
#14 ·
Observations? Yes...

Acceleration from 0 is just not that important to me. What I want is 10-50 roll or 30-70 roll. Things like that. It is accelerating from low speed to much higher is where I want the low-end torque to create maximum acceleration. Passing power, 55-90.

Accelerating from 0 is irrelevant to me.

If the gearing maximizes my power rolling from 30-65 or 55-90, that works for me.
 
#16 ·
Lest anyone wonder what the venerable 325 Hp VQ37 v6 that goes into Nissan 370z's and such...it is even worse than the Pentastar. If you are smart, you don't get caught at 2000-2500 rpm in an upper gear trying to zip away with that engine, period. It might as well be the "S2000 engine" of the v6 world, in that respect.
 
#17 ·
Well I had a 2009 infinity G35 sport with the paddle shifters and despite all the criticism than motor took of was pretty damn fast to 60. I remember one particular time a Challenger R/T though he was going to take me from a dead stop. The all wheel drive Infiniti embarrassed the R/T pretty bad. I think it was rated at 5.2 0-60.


Sent from my Autoguide iPhone app
 
#18 ·
For a V8 the Hemi has a bit of a schizophrenic nature. At times I'll be cruising in 5th (autostick) on the freeway, and the pickup will surprise me without need for a kickdown. And then at others I'll clearly have to drop 2 gears in order to get max acceleration, which I wouldn't expect from a 5.7. It's like they managed to make it quite serviceable on the low end, but it's still peaky by the nature of its power curve.
Years ago, I wouldn't have believed that I'd live to see 8 speeds (not yet, I know, but the 5.7 could really use at least 6) and paddle shifters on big V8s. Because when I was growing up those engines were known for making transmissions pretty much useless.
 
#19 · (Edited)
...It's like they managed to make it quite serviceable on the low end, but it's still peaky by the nature of its power curve.
That's how I look at it, too!

Personally, I think the 5-speeds it has is fine for a number. I would only specify a more "normal" 1st gear ratio, so it isn't so much of a powderkeg when you lay into it.

When my experiences were young with the car, I would say the 2nd gear could stand to be a bit shorter, but after building more experience and finding the ideal conditions to use it, it's probably in the place it should be, in the context of how fast this car wants to be. When you are good in a turn and putting the suspension and tires to work, you will be carrying sufficient speed such that the existing 2nd speed ratio is right at home. I would dare say that is probably what they were shooting for. 2nd gear lines up when you are hustling in that turn, not when you are babying it around a turn. Should you expect less in an RT?

Whether it should cross the 1/4 mi in 3rd or 4th is probably up for great controversy. It seems to be doing quite fine with 3rd covering the feat. If there was "a lot" more to be liberated if 3rd was shorter and 4th finishing the run, that would imply it would get considerably faster than the 6-spd manual. As much as I would be pleased of such a revelation, I think it to be a bit optimistic to be true. I think they just lucked out with 3 gears being able to leverage the Hemi powerband just right, and such a balance should not be disturbed (because it ain't broken).

If they experimented with an even peakier Hemi, then perhaps I could see 1 or even 2 extra gears might yield some benefits. Personally, I don't think the Hemi needs to explore getting "peakier", though.
 
#21 · (Edited)
Low end torque is one thing, but turbo-diesels are another kind of animal altogether. They have excellent low end torque, but at the expense of significantly less rpm extension than a gas engine, not to mention increased block weight and mass in the moving system (i.e, high inertia which further impacts responsiveness and revability). In that context, the big gasoline engine is quite an unbeatable profile as far as all the things you want in a performance car. There's a reason the gas engine has become as prolific as it has.

I'm not trying to shoot down your remark when I say that. I know you are just extending upon the sentiment of the virtues of low end torque. When somebody brings up diesels, though, I have to make sure we understand the distinction of how different an engine that is, even though they both can have very good low end torque. Imo, they aren't really that interchangeable as far as applications.

The gargantuan GM Vortec 8100 would be an interesting test case, though. I'm sure it is quite heavy, and is not all that up to revving, even when not even close to the redline. So maybe a turbo-diesel would be quite similar in driving nature to the Vortec 8100. It's an interesting question, that I have no answer for. ;) A large turbo-diesel will likely be punching even higher torque than the Vortec, though. There's no way a naturally-aspirated gas engine could hope to keep up with a turbo-diesel in that respect, right?
 
#22 ·
i've never felt more low end grunt than my old tuned 335i.

390ftlbs on a mustang dyno in a 3400lb sedan.

to this day, even the 392 felt feeble down low compared to the 335i........
 
#23 ·
So, randycat99... we hear your observations, but what are you advocating exactly? I'm with you in that, although fun as it is, the Hemi shouldn't get any peakier. But would you like to see larger engines in the lineup? Or would you like to see engineers give us tunes that favor low and midrange rather than the top of the powerband? Would you consider what Litos is pointing at, namely a huge weight reduction in order to recover some of the grunt we expect from V8s?
 
#24 · (Edited)
I don't think I am at an "advocating" stage on this...just a discovery/understanding stage of how things ended up the way they did and how that fits with certain motives that may have been in play. I'm just appreciating what they came up with and how best to leverage its strengths/peculiarities to appreciate it even more. :) Hence, in noting that powerband looks like x, I laid out how critical the choice is between 1st, 2nd, and 3rd in order to leverage that powerband. Once you can do that, you are in a far better position than getting caught in a "bog" with the wrong gear for the situation, am I right? :D The peaky Hemi powerband becomes less of an issue after than, rather the impetus for a strategy as you drive.

If you think about it, that Hemi peakiness is rather authentic to what the Hemi stardom was originally about, anyway. In the late 60's and early 70's, it was THE v8 out of them all with top end for winning races. Of course, it was in 426 ci of displacement back then. So even its tame low end torque was serious low end torque by our standards. It's still 7 fricken liters of v8 goodness, right? The style of powerband of the modern Hemi remains authentic in shape, though. I'll say that. The Hemi was never about being a low rpm bruiser, so I really would have no basis to suggest it should be so in modern day, just for its generous displacement. A Hemi still needs to behave like a Hemi, right?

Now if the low end torque was really bad, then I would just call it hopeless. When you cut low end too much in order to maximize top end, it's not going to be an enjoyable engine for driving around on regular streets. Yes, you can employ "the strategy", but you are stretching great lengths to make it work for it to be fun, when the reality is the designers sacrificed too much in order to make it spec better and/or appeal to track duty. Ironically, that is somewhat of a complaint I've heard made as far as people who have experienced the original 426 Hemi's. They were not all that well-behaved for regular driving until you put some rpm into them (after which they sung, but you were doing a bit more than just "normal driving", right?).

So I suppose I can tolerate "some" hit to low end torque, but there better still be some meat in there, or I'm gonna complain. I think the Hemi is in such way about as much as I would like, before I say, "Really?!...5.7 L of v8 displacement needs to feel better than this on the low end, period...or I'm not really seeing the point of big displacement v8's." Yes, 5.7 seems big in my book, but in reality, you pretty much need it to move a car this size/weight properly.

I think in various other discussions, I've expressed preferences if they could tune the powerband differently, to tune for a bit more meat on the low end. If that comes at the price of top end, then I imagine that will assault the goals of other Challenger customers who live and die by the performance specs and actual forays into racing. So, I think that is a no-win scenario. Dodge does need to cater to those customers or the car won't have the "rep points" to keep people interested (and ultimately keep the model alive). I can understand that.

Lighter/smaller Challenger?...I think the cast has been set. One of the exclusive perks of the Challenger IS its room and accommodations, I believe. Necessarily there is a weight penalty for it. It saves a couple hundred pounds over the standard LX cars, so I reckon that was a solid effort to make it lighter already. I don't think they should bother making it lighter. I do think they should introduce a different car model that will have a Hemi and be appropriately sized and weight to legitimately fall in the "pony car" category. As it is, I think we are lucky that these big Challengers even exist for us to enjoy them. If Dodge has the resources to actually introduce another model that is smaller and lighter, that would be great, but I'm betting they don't. So we just got to be happy that a Challenger exists as-is, whatsoever. If they start cutting it up and changing it just to make it lighter, I fear the patient will ultimately end up DOA for disturbing a distinct balance that made it all work in the first place. Even if the patient did live from the surgery, it would just be walking into a firefight coming from both sides. What do you think is going to happen? Unless it is the car that Zeus races, it will get strangled for sales between Ford and Chevy and die, anyway. So will that be worth it? I don't think so.
 
#25 ·
After owning several "older" muscle cars including the torque laden Buick 455 Stage I, it seems today that almost all if not all performance V-8's are tuned for HP ahead of low end torque - probably more for marketing/bragging rights and possibly CAFE standards than anything else.
 
#27 ·
Yes, you are absolutely correct. Everybody has to in order to stay on the same playing field as the other guy, as far as marketing perception. The LS3 and the Ford dohc 5.0 are all peaky style engines. Doesn't matter if you are Hemi, wedge, or multi-valve...you got to be camming for peakiness to keep up these days.
 
#26 · (Edited)
Lots of truths in your post, randycat99. I saw you mention low end grunt and older V8s before so I was wondering what you wanted us to think about (so many people post about what Dodge should be doing...).

I also think that you're right about the NAG1's gearing. A taller 1st would tighten the other gears up and maybe get rid of the 1-2 and 2-3 gaps. Of course, more torque or 400 lbs less would also work, but that's probably not gonna happen. Cars are getting heavier and heavier, engines peakier and peakier, so we'll just see more and more speeds in our trannies.

That low end torque we have is there for sure; it just feels a little artificial and is not exactly gonna push you back in your seat at 2,000, but like you I'm pretty much resigned to what we have in that department. And the first gear masks that really well, as you said.
 
#28 ·
That low end torque we have is there for sure; it just feel a little artificial and is not exactly gonna push you back in your seat at 2,000, but like you I'm pretty much resigned to what we have in that department. And the first gear masks that really well, as you said.
That brings up an interesting point about the Mustang GT. If you think the NAG1 1st gear is short, you should take a look at the 1st gear that is in the Getrag 6-spd. They don't play around, and the result with that 1st gear is mindshattering despite only 5.0 L of displacement and a definite shortage of low end torque. Of course, when you have a 7000 rpm range to burn, I guess such a choice in 1st gear ratio is not all that unreasonable. ;) ...still got to pick your gears wisely after that for spontaneous bursts of acceleration at a roll, though.
 
#29 ·
I understand what your getting at, but having driven the old cars, with many 440's, a couple of 426 hemi's, and several 383's, and a big block chevy or two thrown in.....I have to say I think the 5.7 is a pretty torqy motor. I haven't driven the 392 yet (hopefully in the next couple of years) but the 5.7 has enough torque in my challenger 6m to lug it down to 1200 or so in 4th gear with no difficulty. Had I tried that in my 440 or 426 cars it would have resulted in bucking and a serious bog, maybe a backfire through the carb....lol. They had the same gearing with shorter tires, and considerably less weight.

Using this as an example I think they have done a great job stretching the usable rpm range to heretofore unknown lengths, you do have a point that if you are in third or fourth gear cruising at 1800 r's and step on it hard you aren't going to win any races, but you will accelerate smoothly with no drama. The same could also be said of my 440+6BBL roadrunner with a 4spd, 4.10 gears, and weighing in at 3500lbs if I was cruising at 1800 r's and eased into the throttle it would accelerate smoothly, but if I punched it not so much.....more of a bog building up to stronger pull you into the seat power as the rpm's climb.

And seeing as how the 5.7 redlines at 5700 or so (or at least stops making power) I don't see it as peaky at all. I think it has a strong low end, with incrementally stronger mid range and top end. What I think is giving this feeling of peaky behavior is perhaps that the cars are so smooth, and the power delivery is also very smooth, plus the weight of the cars maybe it doesn't feel like your really doing anything until you get up around 3000 rpm or so.

The quarter mile times along with the 0-60 don't lie, another member I think hit the nail on the head when he said they don't feel like they did in an old car, in other words drama free acceleration. I will freely admit they don't feel nearly as fast as my old cars, but the stock ones didn't run much better than this car and that was only on perfect runs. By far the average runs were closer to what a good driver in a new R/T is running in the 1/4.

I have raced a few buick GS 455's back in the day, and they had exceptional mid range and low end torque. You had to be on your toes to beat them if they hooked, of course a properly setup 440 has outstanding low and mid range torque as well. The common denominator being they were both considerably bigger engines...with the SMALLER of the two being 440 inches...lol.

I venture to guess that if you took the 5.7 engine out of my 2010 challenger and put it in a '68 stripped taxi cab B-body it would feel a whole lot stronger....from the bottom to the top of the RPM range. I believe the difference would fool someone that was driving it into thinking it was a MUCH bigger engine. If you did the same with a 6.4 hemi, I believe it would be stronger than a 426 roadrunner.....stock for stock.
 
#121 ·
Had I tried that in my 440 or 426 cars it would have resulted in bucking and a serious bog, maybe a backfire through the carb....lol.
You seriously had me ROFLMAO with that comment.

So true.

I used to worry that I couldn't find 3rd gear effectively on a down shift with the 5.7L / 6m. Then I discovered there was essentially no need to downshift to 3rd except under the most extreme circumstances. It would actually CAUSE more bucking (popping the clutch in too low a gear) than it would CURE.

Fascinating discussion.
 
#30 ·
^^^ Great perspective, especially for someone like me who never drove the oldies and just extrapolates from second-hand info and other engine types (motorcycles).
 
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