s.hasan546

I've owned both. whats your point? owning both has made me realize awd is unneccessary. The only thing that will help you in deep snow is ground clearance. Thats why i have a SUV. I don't see the need/want of AWD in a small car. Than again i hate anything thats not RWD, it's just more fun. & yes i don't like that my GTI is FWD either but hey i needed a cheap DD.

Duke Togo

u no nuhzeeg!!!!!

the gtr lords on all surfaces all of the time - it's not the awd alone it's the tq vectoring to any wheel. I have a couple of friends that don't like the harsh ride and poor tire life on the 20's and went to 18's and drive them in all conditions and love it.

We took my friends to mammoth last year and had a blast when the roads were snowed over. I'd say its the safest all weather car i have ever drivin in.

I know a couple Porsche drivers that switched but some others that like to tell people they drive a Porsche not a Nissan. - If i could only have 1 car and I had a family the gtr would be a very attractive option with young kids and compared with the 911 back seat it's like a limo.


The main difference and the reason it won't replace my s2000 is it's a gt car great for open road cruising and most back roads but really tight areas like my favorite local road it's not as fun.

Plus I <3 top down

rockville

fishfryer

I think the people that stayed with Porsche may be just too embarrassed (and rightly so) to say they spent $90K on a fast, but homely Nissan, not that they just wanted to say they have a Porsche.

rockville

So we are still missing answers from StepedOn and Nunco.

NuncoStr8

I explained in English. I explained in physics equations. You always fell back on "I talked a guy that worked on a competing product..." instead of thinking for yourself.

If you want to talk about "bad form," let's talk about insisting people explain things in a particular language so you can always claim superior knowledge of the language as a trump card. If you don't understand English, say so. But don't point to other people as a proof. That doesn't work. It just demonstrates you yourself don't think you fully grasp the subject. And if you are willing to say you don't fully grasp the subject, why would anyone buy your assertions that you are right and the person who lays out the reasons you are wrong somehow is confused?

I'm not saying you are an idiot. I'm saying you are quick to criticize others for a lack of knowledge but fail to accept your own lack of knowledge. Rather than educate yourself and recognize there are things you don't fully grasp, you revert to "this one guy said I was right, so you are wrong." That's BS. And anyone with a thinking, analytical brain would know that.

I pointed out the failings of the Torsen paper. Torsen is selling a product that competes with the pre-loaded clutch-types, but their product is inferior because when one wheel has zero traction, the other can deliver zero torque. The pre-loaded clutch-type can deliver 100% torque to just one wheel even if the other wheel is off the ground - due to the preload. That represents a deficiency in the Torsen design compared to the pre-loaded clutch type. Do you really think the engineers getting paid to publish a white paper on their bread and butter will publicly or even privately admit that their description of the clutch-type LSD is favoring their work?

Your failure to grasp the fact that a wheel can only deliver torque when there is a reaction torque, i.e traction, is the main issue issue. Physics and engineering are not the same thing, and when the notation and symbols look the same, they don't always mean the same thing. Even when the terms are the same word, the meaning is sometimes quite different.

Start a new thread if you want to revisit this issue. I'm not going to clog this thread to satisfy your weak ego. You are not dumb, you are not ignorant, but you have a weakness for assuming you know more than *anyone* around you and assume anyone who cannot discuss an issue in engineering terms is an ignorant fool. You'd argue with Newton because he wasn't privvy to the mathematics invented long after his passing. You'd call Descartes stupid because his coordinate system did not work for intercontinental navigation on a planetary sphere. You would never consider that those men might not have been able to convey their understanding in the terms you learned in college but they understood the subject as well or better than you.

I'm a software engineer, and I cannot tell you how many people I have had to listen to bemoan the failings of a particular software package for "failure to adhere to standards." But in programming there is a concept called "object-oriented programming." In theory it is perfect. In reality is is a good paradigm for thinking about the structure and execution of a model. But in practice it is insufficient to provide the solution. In many cases it is simply massively inefficient to adhere to the ideal model. And beyond inefficiency, the code becomes increasingly opaque to anyone who has to maintain the code base to deal with the ramifications of adhering to a paradigm that doesn't fully represent reality. So "object-oriented programming" is useful as a general model and useful in the planning stages, but when it comes to execution - the actual writing of the code - one breaks the object-oriented model for efficacy and readability. And gains efficiency as a freebee. But in the context of a college course on "object-oriented programming," no matter how many times the professor stresses that the paradigm has real limits, you still see people writing code that is cumbersome, inefficient, and impossible to maintain. Trying to adhere to a "standard" or ideal that is untenable in the real world.

We won't even get into the ignorance and arrogance of those who maintain that adhering to a "standard" is always the best practice :/

I write this to illustrate that "book-learnin'" is a weak substitute for observation of the real world, and really ought to serve as a framework for interpretation and a foundation for knowledge, not as a substitute for reality to the point where one insists that any opinion that cannot be expressed in the language and symbols of a textbook is somehow fundamentally invalid without analyzing the content itself, even if such content cannot be conveniently diagrammed per the textbook.

You fail to grasp how limited slip differentials work, and part of the fault lies in the few published papers, which simply says you are hardly alone. And the other part lies within your own unwillingness to acknowledge that despite your education and experience, people without that same formal education and experience can still understand phenomenon more accurately and completely than you.

In a recent "torque vs. horsepower" conversation here, some people who should know better cannot resolve the reality of actual observation with what they believe to be true. It has nothing to do with education levels. Some people have zero difficulty understanding that torque equals acceleration, and when they look at the relevant physics the equations seem obvious. Yet other people seem to have issues accepting physical observation and established science, and prefer to belive in a fallacy. The disconnect does seem most extreme in individuals with an engineering background, however. Perhaps because they think they understand more than the "common folk," e.g. anyone but themselves. Even when long-accepted equations differ from their beliefs. Don't let your education blind you or turn you into an elitist that maintains your opinions are infallible even when wrong.

rockville

Even though I am not at all convinced you know what you are talking about, I do appreciate that you have taken the time to type this up. This separates you from those who say crap but then can’t back it.
That’s not true. I started the thread and included illustrations and math equations. That’s hardly a case of I didn’t do any thinking.
You disagreed with the math I put in the thread. Well I asked you to provide your own equations. You provided some verbal stuff but nothing that fully described the torque flow through the diff. BTW, I didn’t point to others for my proof. I showed all the math myself. I just showed that others, people at companies such as Gleason and Eaton, agreed with my equations and math.
I’m not quick to criticize others who don’t know. I’m quick to criticize others who espouses things that just aren’t true. Remember, when we started that thread you weren’t willing to even accept that an open diff sends equal torque to both rear wheels. You did see that and I’m glad we agreed on that point but if you didn’t know that it’s hard to understand how torque flows through a diff.
What failings in their paper? Their paper was describing the function of the diff. I think you are saying the diff isn’t the perfect LSD. I won’t argue with that. Of course the Torsen paper wasn’t a part of my arguments nor was it a corroborating source for any of my arguments.

Actually I didn’t fail to understand that. That is a basic part of physics, sum of the forces equals zero. So if the shaft to the wheel transmits torque then the wheel must be resisting that torque. Saying the diff applies x Nm of torque to the ground via the wheel is the same as saying the ground resists with an equal amount of torque (forced via the wheel).
I don’t know more than anyone. However, I do know more about this subject than most. That is why I created the thread in the first place. I don’t assume anyone who can’t discuss it in engineering terms is a ignorant fool. However, this is an engineering topic. A non lawyer can discuss the finer details of the law with a lawyer but if they don’t use legal terms correctly then there is a great risk that what they mean and what they say will not be the same to a lawyer.
I’m a research engineer. I do look at power flows, torques, dynamic systems etc. I do understand how forces are transferred. The hard part is keeping the details correct while not losing people in them. Regardless, the equations I presented were correct and correlated with those of Eaton Corp and others. While we shouldn’t decide these things via a vote, when you are disagreeing with several engineers in the field you, not I, need to ask if perhaps there is something you are missing.
Both book learning and experience are valuable. Happily I have both with regards to this topic. I have my personal observations and comparisons between RWD cars with and without LSDs. I also have the observations of an engineer who was doing this work on Indy cars back in the 1980s and early 90s (still doing diff and other parts today). When we can’t correlate observation to theory we have a problem. When observation and theory match as they did in my case, you can feel good about the answer. Using an inability to express the answer in the common vernacular is a problem because even if you might be right, well you can’t communicate the idea thus the idea is only in your head. That said, I don’t believe that you understood the topic since you couldn’t understand how relative wheel speed (not that the left wheel is turning 5 or 10 rpm faster than the diff but that it’s simply turning faster) was a critical part of the math even if all it did was control a sign (+ or -).
Again, before my thread you weren’t even sure of the idea that an open diff sends equal torque to both rear wheels. If you were uncertain of that I don’t know that you are qualified to judge the validity of my statements any more than I am to assess the validity of complex computer code. The torque flow through the diff isn’t that hard to understand if you are willing to break it down. If you want you could use bond graphs to do the job but that really is over kill. If you wish I would be happy to try to derive the equations more clearly and will even do it in the case where the clutch pack is only on one wheel. The math will work out in the end.
I didn’t partake in that discussion so I can’t comment on what mistakes people made.
I would be happy to create a second LSD thread but only if you are willing to lay out in math terms what you claim is going on in the diff. I can try to change my description but in the end I will say the same thing just in different terms. Even though I disagree with you I’m happy to see that you are at least willing to back what you say when you tell me I’m full of it.

Christople

getting juicy up in here

NuncoStr8

I'd be happy to respond when you can articulate your arguments in grammatically correct Swedish. Until then I'll just maintain you are wrong. Like looking in a mirror much?

Your whole contention regarding relative wheel speed illustrates your ignorance. A clutch has nothing to do with relative velocities. Period. Which is why I can say with some degree of authority that you are simply wrong in your understanding of how an LSD operates. I had my car on jackstands yesterday and played with my differential. Have you ever done that? I didn't think so.

Give it up. You whole "understanding" of an LSD comes from incorrect papers and perhaps, at best, discussions with the mislead engineers who wrote those examples of marketing by poor science.

I use discussion to clarify understanding. I might enter a discussion looking for a greater understanding. I might know one or two points based on experience but be unsure of some intermediary situations or be unclear on the reasons behind the observed behavior. To claim someone knows nothing based on their desire to clarify certain gaps in knowledge is a sign of an unsure intellect desiring to bolster an ego. You read like a newly minted engineer convinced they now possess the sum total of human knowledge, not realizing they have barely scratched the surface and the veteran Piper Cub pilot knows more about how angle of attack affects lift than they will ever learn from reading every book on the subject. Despite the Piper Cub pilot not being able to use textbook engineering math to explain it because engineering math doesn't encompass that realm. Not to mention "knowing" is not the same as being able to convince a know-it-all.

For you any friction clutch operates on relative velocities, ignoring contrary evidence provided by disk brakes and transmission clutches. Suck it up and admit a possible failing of knowledge rather than advertise your stubborn adherance to ignorance on a public forum.

rockville

And right there you missed one of the key points that I had made. Velocity is not the issue. We assume simple coulomb friction (as opposed to more complex models) thus the MAGNITUDE (that is the absolute value) is not a function of velocity. However, which direction is the DIRECTION of that torque? That DOES care about velocity to decide direction. When you press the brake pedal the calipers clamp the disc. The disc imparts a torque to the wheel. How does it know which direction to apply that torque? When I'm going forward the brakes reduce my forward velocity. When I'm going backwards they reduce my rearward velocity. How do they know? Well of course, you say, it's easy, friction always tries to stop things from moving with respect to each other. So to know the direction of friction I need to know the velocity of say the wheel with respect to the caliper. If the wheel is spinning forward then the brake torque is backwards. THAT is why we need to know velocity. Because we need to know which direction the torque is acting in the diff's clutch.

When the plates of the clutch are turning (which they normally do as you corner) which direction is the friction torque acting? If the axle is spinning at say 15 RPM clockwise and the diff housing is spinning at 10 rpm clockwise, which direction is the clutch torque with respect to the axle? The engine torque is making the axle spin clockwise. But the axle is spinning faster than the diff. So which direction (not how big, what is the direction, clockwise or counter clockwise) is the clutch torque applied to the axle?

If the axle is spinning faster than the diff housing that means the torque as seen by the axle is in the opposite direction. So the engine torque makes the axle spin clockwise. The clutch torque as seen by the axle is counter clockwise. Do we agree that when the axle spins faster than the diff housing the clutch torque is working against (opposite sign, direction what ever) the engine torque?

BTW, thanks to Tamiya I understood the basics of an open diff before I could drive.