This is a total bullshit and fabricated conclusion. How in the hell would you suggest the LS7 has a better power to weight ratio? It was the first engine to be passed under the new SAE engine rating system. How exactly are they going to underrate an engine, when a neutral third party was involved in the rating in the first place?????? The Merc engine is the more powerful motor. Sorry that the truth hurts.


I have seen dynoes of Supras making more peak torque than an LS7, but I certainly wouldn't say they have anything resembling a good power curve, let alone a better one than a lower peak torque LS7. Did you just make this up too?

 

I wish I could find those dyno numbers with any degree of consistency, because it is certainly not typically of a stock LS7, at least from what the search provided on this board. Most are 440-450rwhp stock dynoes, give or take.

As was stated, with the new SAE procedure, it would be extremely difficult to lie about engine ratings, given there is a third party involved in the procedure. I believe they are allowed to rate the engine anything within a certain percentage of what it dynoed, and I am thinking it is 3%, but I could be wrong. However, if the LS7 did dyno at exactly 505, then the highest they could advertise it at would be 515hp, if my 3% SAE correction factor is indeed correct. Nowhere near 550hp.

 

I never said 550rwhp. As I said, numbers in the first post were at the crank. If you want to doubt Katech's numbers being accurate, fine. Honestly, it is very close either way and the cost is the major factor.

Generally speaking, when comparing two engines of roughly equal horsepower, the one with the higher peak torque output (especially if it is at a lower rpm) has the more robust power curve. But I already said that we would need a power graph to confirm this, so you're really swinging at air.

I ignored this the first time you said it because it was so silly. But it seems you actually mean it. Where exactly did I say that the AMG motor proves that the LS7 responds to mods? I said it proves that the LS7 is a good motor.

look:

Structure: The AMG motor proves the point: given (x) and given (y), it really shows (z).

The AMG motor doesn't show (x) or (y). Given (x) and (y), it shows (z).

 

I never said anyone at SAE or otherwise was lying about the numbers. If I were to hazard a guess, I'd say the culprit is the stock computer of the LS7. We already know it's killing a lot of power, so it's not a big leap to figure that it might be responsible for funky low dyno numbers.

Either way, you're having a fit over 15hp, (since I only used the 520hp number to figure power/weight ratio). I described the two engines as being "about equal," which is true no matter what dyno you go by. (SAE, Katech, etc).

And I'd still bet good money that the LS7 has more power under the curve. But as I said before, I would like to see the graphs side-by-side to confirm this.

 

What is "engine dynamics" apart from how much merit an engine has in making a car perform?

 

You said "dyno at..."

Generally, making vague generallizations is a poor idea in a tech forum. We operate based on facts here, not warm fuzzy feelings. This isn't a football pregame show.

gooooobye logic
How does the AMG give you that? Even given that its true, how does AMG motor + LS7 response to mods = prove LS7 is awesome

 

 

You do know there there exists a thing called an engine dyno, don't you?

It may be a generalization but it isn't vague. Perhaps you could provide a case where it isn't true?

AMG motor = pinnicle of large DOHC V8's. (according to some)

LS7 = highly competetive with it in general and definitely beats it on cost and response to mods.


And that means?

 

Originally Posted by black_knight
What is "engine dynamics" apart from how much merit an engine has in making a car perform?
In english?

 

ok.

 

that 1.3L is not hauling 3500lbs of weight... but be it as it may... who is winning lately on drag racing bikes?

 

We have some invalid points, first of all you don't need 2.7L of pushrod motor to make greater than 163rwhp out of a small 4 cyllinder, it can be done with less.

 

What would physical size of a 1.8L 4 cyllinder be compared to a 1.3L of DOHC fury.

 

I didn't have a fit. You sure have a flair for exaggeration. Besides, your arguements are so vague how was I supposed to know number "you decided to use" for the LS7's actual power output when you determined the LS7 to AMG power to weight? Yes, both motors are "about equal", but the AMG does better based off the SAE dyno correction GM used to rate their LS7. These are the facts, and I didn't have to make up any numbers to get to them.


Sorry. I thought this was the advanced engine performance board, where all engine principals are fair to get scrutinized, not just the ones that make the GM small block look good.

Actually, you didn't say that at all. You said.
"And the LS7 definitely beats it in torque and thus the power curve.",
which doesn't make any sense at all. Another assumption on your part.

I won't argue with you over cost. It is one expensive *** motor. However, how do you know how the AMG will respond to mods? Another assumption on your part? I believe it is. Yes, mods would be more expensive for it, but we already covered that in the cost department. You have assumed a lot about the AMG motor to make an LS7 look better. Was the AMG tested under the new SAE guidelines? I know the LS7 was, but I am not sure about the AMG motor, since the test still is still voluntary. It is possible the the AMG could be putting out even more power than advertised. The supercharged v8s and turboed v12 Merc engines certainly seemed to be putting out more than advertised at the drive wheels, at least for the few owners that actually dynoed them and put their results online. I know that Treynor guy who has 1000hp Viper who posts over at fuelslut.net and a bunch of other boards had a very healthy dyno for his AMG Merc, which he posted. Again, I am not saying that AMG 6.2 is underrated, but if you are going to start posting bigger numbers for the LS7, it is worth thinking about.

 

It's not a matter of whether it happens to make the LS7 look good or not. There's a very important point that I'm making: there is no such thing as "engine dynamics" apart from how well the engines make cars move. The entire purpose of an engine is to make a car move! To judge it by some other standard is the definition of meaningless! You may as well say that one is prettier than the other!

The fact is that if the standard of making a car move is the one that makes the GM engine look good, then the GM engine IS good.

Actually, I said:

Why would I even be interested in seeing the graphs if I considered it 100% proven that the LS7 must have the better curve. I'm still waiting for a counterexample to prove my generalization wrong.

Here it is again, for anyone who wants to try and find one (yes, I am actually interested because I care about the facts): when comparing two engines of roughly equal horsepower, the one with the higher peak torque output (especially if it is at a lower rpm) has the more robust power curve.

If anyone can show me two engines of roughly equal peak horsepower, where the one with a higher peak torque number at a lower RPM does not have the more robust power curve, I would be interested.

It's something I am assuming, but not baselessly. The AMG motor already has variable valve timing so I don't think power can be extracted from the cam. (whereas the LS7 is clearly undercammed) It also has a tuned intake so I don't think there's power to be found there. I imagine the exhaust is restrictive, but what exhaust isn't in these days of emissions (certainly, the LS7's is restrictive)? I don't know the AMG's deck height to know if it can be stroked or not; if it could, then that would help it. (The LS7 is already basically maxed there) And I don't know if the AMG's computer is nerfing it; certainly the LS7's is. I know for instance AMG’s biturbo V12 is computer-limited.

But that is speculation which I will admit. If it turns out that the AMG can gain 125+ horsepower from cam(s), headers, and tuning like the LS7 can, then they'd still be equal on that footing and we'd be left with cost (winner, by a wide margin, would be the LS7). Right now, I honestly think the LS7 will respond better to mods. You can go on the record disagreeing if you like, no skin off my back. Maybe at some point someone will prove one of us right, maybe not. <shrugs>

 

Oops!

Looks like we all forgot that zee Germans use METRIC horsepower. 375 kW = 502.8 Horsepower in domestic terms. So the AMG is down 7.2 HP, oh well. I guess someone should tell "the world's most powerful naturally aspirated V8."

'Course that's not SAE horsepower so who the hell knows what it makes anyway. I tried to put up non-SAE numbers for the LS7 to match the AMG's non-SAE numbers but got flamed for that.

 

Generally, you're supposed to support your own generalizations with proof, logic, reasoning, sources... not just "because i like the LS7 more." This is more "I believe in the home team" type crap than "tech."

no.
I'm not wasting my time, its comletely irrational and unfounded. Go look at F1 vs NASCAR or the S7TT vs the any other 750hp engine.

Its completely baseless. Supporting your original basleess assumption with other baseless or illogical assumptions doesn't make the original any less baseless.
regardless of whether you're right or wrong, you haven't
a) proven anything. you just took a lucky guess based on fabricated or distorted information and managed to hit a bull's eye with your eyes closed.
b) proven anything about OHC vs DOHC

 

You're hilarious. Who are you quoting there? I never said anything of the sort. If you're so sure I'm wrong, then go ahead and provide an example to prove it.

Here's an example that shows my generalization to be correct:



Let's see:
"when comparing two engines of roughly equal horsepower,"

check.

"the one with the higher peak torque output (especially if it is at a lower rpm)"

That would be the LS2. Higher peak TQ number at a lower RPM.

"has the more robust power curve."

Well, what do you know? That's the LS2! So there's one example where I'm right. Do you by any chance have an example where I'm wrong? (I'm going to say for naturally aspirated engines, so you don't just throw a graph with a nitrous spike in...) I'm not saying I know it will be right but it makes sense given the math of TQ and HP calculations. I honestly don't know why you're so hostile to it. Perhaps it's because you're the one playing favorites with engines...

If it's so irrational, then provide a counterexample. It should be easy if I'm wrong.

Calling it "baseless" and "illogical" is meaningless without a description of how those terms fit what I wrote. You keep doing calling me that, but have in no way shown anything.

 

GM is good at that, and they make one hell of a powertrain. However, somewhere, someone had to take into account trying to get this prospective engine to breathe as well as possible in the design phase. You know, making as much power from the smallest sized package, and all that jazz. I guess we aren't allowed to talk about what kind of engineering went into an engine's development according to you though.


No, this is how you tried to recover your original idiotic statement. You said:

"And the LS7 definitely beats it in torque and thus the power curve.",

You then tried to make the statement you highlighted here to recover some degree of credibility in your arguement. Why should we have to prove your statement right or wrong? You are the one who made it, and you are the only one who has actual said that the generalization is in fact acceptable.

Well, I actually took some time to find a dynograph for a Ferrari 4.3L v8, but to no avail. That has similar output to an LS7, so I think that would be a reasonable enough example. Hopefully someone might have one saved to their hard drive on here that they could post, because apparently most Ferrari owners don't know or care what a dyno is.

Seems to me most of your assumptions are baseless. The only conclusion I can come to is between the two is that the LS7 certainly is relatively more attainable, but even so, the LS7 is a very expensive motor that I can't see too many people buying just to modify. As to which motor is better, I certainly have no idea, but I don't come to my conclusions from assumptions.

 

Its ok Russ, he knows everything. We are at a severe disadvatage in this debate because our posts have to be true.

I guess God just blessed him with this superpower where his intuition is always correct or something Great to compare two engines of similar power output and different displacement to make a case of flatter torque curves.

Engines with lower specific output have flatter curves because they aren't tune for maximum power at a specific rpm