lol i was thinking about that too but then again im not full race like some people =x

 

The difference in each car if you give them all the same performance upgrades (wheels/tires, springs/dampers, brakes, etc.) is still going to be in the suspension geometry. Each model, whether it is the IX, the X, or an M3 will have different suspension geometry. With that being said, remember that there is no perfect suspension geometry, and just by changing the tires being used, you could change the outcome in a race. What I mean by that is that the IX might perform best on XXX tires while the X might perform best on YYY tires. The other major factor is in how the cars are setup. Designing a good suspension set up with good components is only half the battle. Setting up everything is critical to achieving the maximum performance for any given car on a certain track in certain environmental conditions. Setting up a car properly is very time consuming and involves balancing the corner weights, setting proper toe adjustments, static camber (based off measured temperature gradients across the tires after they are warmed up), jounce and rebound damper settings, spring rates, spring preload, ride height, and sway bar stiffness (front and rear) to name some.

Now when you talk about the differences between the IX and the X, you listed a couple major differences. The track width is different but I am not really sure how much a difference this makes. A wider track width will decrease your weight transfer keeping the load more evenly balanced (assuming that the CG height remains the same). The reason this can help is that all tires have a coefficient of friction that is relevant to the normal load on the tire. For a given tire design, the coefficient of friction will start to drop off as the normal force increases beyond a certain point. With an excessive amount of weight transfer, the coefficient of friction is often reduced.

A stiffer chassis is important for a couple reasons. First, it helps to hold your suspension points in the correct positions to make your vehicle reactions more consistent and predictable in the turns. The other side is that you can see your chassis as a massive spring connecting your 4 wheels (or contact points with the ground). There is not way to dampen this spring so if it is softer (more flexible chassis) then bumps and forces acting on the chassis will cause it to oscillate more and cause the car to be less stable. If you can stiffen this up, you will get less deflection, less oscillation, and a sturdier or “planted” feel.

Finally you mentioned the S-AWC. This system is actually pretty amazing and is a system that is now possible with our modern computer processing power. Most traditional suspension systems are passive, meaning they basically use mechanical devices to aid in keeping the tires planted to the ground. The S-AWC is active, in that is monitors several inputs so the computer can determine what the car is doing at any given moment and then it makes a decision on how to improve the traction of the vehicle and keep it stable using the front to rear power distribution (ACD), the left to right power distribution in the rear (AYC), the total power being generated (ASC), and the braking system on each wheel (Sport ABS). This whole process is dealing with the force vectors coming form the tires.

I would say that these things combined with a better suspension geometry design are some of the factors that would contribute to the X being a better track car than the IX.

Now in actual track comparisons and testing with very similar setups on different cars, it will often come down to the driver skill and comfort level in each car. A driver can make all the difference in the world and even using the same driver between cars will still introduce some variations.

“It comes down to whether the technology is worth the lighter weight.”
I think this quote you had is what most automotive engineers think about whenever they are designing new vehicles. This is a major topic in modern vehicle design and will continue to be. Several technologies are developed but only some will prove to be worth their weight.

As for the extra technology in the M3 being worth the extra 200 lbs over the Evo X, I really don’t have an answer. I am sure it can be argued either way until enough testing and data acquisition it performed to support either side. This same argument is continuing between the IX and the X, however, there are engineers that I assure you have done that comparison.

 

lolz they believed what the company said about its own cars.


Blacktrack, have you removed the airbags? I am curious how much the extra airbags added to the weight of the car.

 

Thanks,

So by "fixing" the IX's suspension geometry, it doesn't fix it, because the IX inherently has a worse geometry? Maybe I am approaching this incorrectly, because I thought of it as, say there are two cars, and one has a much more restrictive exhaust (worse suspension geometry) than the other. Fixing it on the car with more restrictive exhaust yields more benefit than on the other car, though the final output may not be the same depending on the car. I thought that the two evo's would be similar, as the ct9a is still a very competent chassis, etc.

Otherwise, yea, it really is basically stiffer chassis vs. s-awc vs lighter weight. Throw in the fact that most track cars driven remove these devices, as the benefit they provide are not actually worth the extra weight.
But, I think most X owners are still convinced of this. If IX's lighter weight is not enough to overcome the X's advantages, is the X's lighter weight not enough to overcome the M3's?
Let's be honest, the IX isn't incompetent, yet X owners consider their various advantages to trump it, so I wonder how they feel about the M3, which has similar advantages with a similar penalty of weight. But yes, you're right, I'm sure the argument can go both ways, I just don't get why that's not the case for the IX.
Thanks again for your great input, and not turning this into a X vs IX thread.

 

bump for more input, but please read all before commenting.

 

I did, I don't have the weight #'s with me right now, but it wasn't as substantial as I expected. I'll check the #'s when I get back in town next week.

 

Which M3 and at what prep level?

The biggest *disadvantage* for the M3 on the track vs. any evo is the AWD vs RWD.

An E36 M3 is very light (compared to "modern cars", but it came with so little power, if you throw an LS1 *cough* Vorshlag *cough* in there, you have a monster. Of course, you need the supporting suspension mods to handle the change in power. I think an E36 M3, right now, is the best bang for the buck 4 seater track car (Miata being the best bang for the buck 2 seater).

The E46 is heavier than the E36, but has more HP, but extracting more HP out of it is a very expensive operation.

And the new E90/92 M3 is HEAVY but it has a ton of horsepower and torque, and prepping it to be a "race" car is not a cheap operation.

 

Ah,
I was more considering the E90/92 M3, because of it's similarity in advantage, compared with the X vs IX.
Stiffer chassis, bigger wheels/better brakes, M differential, which, honestly I would take over any 4wd system, similar track, perfect weight distribution, great naturally aspirated engine. Likewise, a similar disadvantage, about 200 extra pounds. Yet X owners aren't definitive on the M3 being superior, yet with those same advantages are for the IX.

And then I think my more general question was kind of this:
If you take like an old lightweight 90's civic hatch or miata, had a theoretical unlimited amount of money,
and did the same for a X, or any modern sports car, which would come out on top, I wonder, for track or autocross.

 

and what does perfect weight distro have to do w/ handling? Just cus BMW plays that card does not make it the end all and be all of handling...

 

Well it's not the "perfect" or "ideal" weight distribution as BMW and others advertise, but I don't think anyone really needs to go into the effects of weight distribution and handling.... It's not just BMW playing "the weight distribution card"

 

Weight distribution affects how the car turns and how the car reacts to driver's input.

As for the OP question, like some members have mentioned already, there are just too many variables and unless you can isolate out everything, you won't have a definite answer as to why car X handles better than car Y. But one of the most dominating factor that affects handling is suspension geometry. For example, how this geometry changes when a car is under cornering load (ie. camber changes?)

You can buy this book and learn about suspension. It's an old book, but very informative on many levels
http://www.amazon.com/How-Make-Your-.../dp/0912656468


For electronic gadgets and weight adding, I think a very very good example is the R35 GTR. The car is 3800lbs, yet tests after tests show that this car corners better than most of its lighter competitors. I think the Evo X shares the same analogy. It's a little heavier than the IX, but the advantage of having AYC probably compensates a lot of the added weights.

 

But ultimately, as a track platform, would you go with the R35, or say it is too heavy? I think a lot of people would say ultimately it's too heavy, and I'm sure of lot of people would opine that the X with mods would make a better track car. And I'm sure away from the track, through a lot of tight, wrenching twisties, the car would show it's weight.
That's why I bring up the M3 etc., to separate bias from fact a little bit. For the most part I think a lot of people with a lighter car would say light weight is very important, and for people with a more tech-heavy car they would say technology is more important.
So far chassis stiffness and suspension geometry have come up as very important. Weight distribution as well, though some chose not to acknowledge it when it wasn't in their 'favor'.

I wonder if anyone can answer what I asked earlier: If a car's suspension geometry is already good, will improving it yield as much effect as fixing the geometry of a car who's geometry wasn't as good to begin with? Is it analogous to two cars, one of which has a more restrictive exhaust, and it having more to gain than a car with a non restrictive exhaust (though not necessarily ultimately make more power)?

 

At Formula 1 level, isn't the tire's structure and chemistry that dictates majority of handling capabilities? I think at this level, only other thing that would matter is the weight. Or is the modification of brakes and suspension heavily restricted in F1?

Street-wise though, if you compare with cars like Caterham 7 and Ariel Atom, technology is not enough to outhandle the lack of mass and lower center of gravity.

The thing about track racing and at an 'ultimate' level, sky is the limit so you need to at least set some variants. If look at an E92 M3 'GTR' (its called something else) for example, uses a lot of stock-looking parts yet the car makes close to 500hp and weighs just over 2500lbs, and that is only because of the minimum required weight, I'm sure they could bring it down to 2300lbs easily without having any additional research. This is because the chassis/drivetrain/engine is totally different, at least material-wise.

 

For the most part, yes, it's probably too heavy. But then again, if one were to seriously track the car and be competitive, they would be in a class where weight/power determines what they are competing against. For argument sake, you can't say a Miata is better platform than the R35 JUST because it's lighter, and you pick Miata to be your track car. Ultimately, it depends on WHERE you want to race. The same question can be asked: Is FWD or RWD better? Answer is: depends.


My attempt to answer this again, if you have 2 cars: one with very good suspension geometry to begin with; the other with not so good to begin with. The marginal effect on improving the suspension on the latter car should yield more positive results than improving the first car. That's why if you go to autox events, you will see 10 yrs old Civic running faster times than a stock Evo X even though the X arguably has better suspension designs.

 

That test was rigged by mitsu, they put the U.S. spec IX vs. the JDM X which is 200lbs lighter than the U.S. spec X. So if u put U.S. X vs. U.S. IX it would not be a 2 sec adv., all the other tests ive read had the IX on top stock vs. stock.