GXP FE3 Suspension not the FE3 from ZOK as advertise by GM

[VTXSTi]

“If one were to leave stability control on, I would imagine that the Solstice would out-accelerate the GXP for the first hundred feet or so after the apex.”

I am sorry that made me laugh

Have you driven both?

I can assure you, and with all due respect to the NA that’s not even close to being true.

[jimbo]

Originally Posted by RobL I fixed that for you. As I said a couple of times now, stability control inhibits the cars use of power while turning at or near the limit. If one were to leave stability control on, I would imagine that the Solstice would out-accelerate the GXP for the first hundred feet or so after the apex.

Based on what?

Lets use your example that Stabilitrak kicks in at 80%, which I think is laughably low. You own a GXP with Stabilitrak. You know the tires will slip and go sideways before stabilitrak even kicks in. That tells me that Stabilitrack kicks in AFTER you exceed 100% tire grip, NOT before.

But lets use your assumption that Stabilitrack kicks in at 80%.

So a base Solstice has 166 ft-lbs of torque to apply at the apex at maximum revs.

The Solstice GXP has 260 fl-lbs of torque to apply at the apex at maximum revs without stabilitrack.

Apply Stabilitrak and limit power to only 80% (again, I refuse to believe this, but lets do the math). So the GXP applies 80% of 260 ft-lbs of torque that is not negated by the application of brakes and that is still a net application of 208 ft-lbs of torque.

Or are you trying to tell me that that Stabilitrack will apply the brakes so hard that it will overcome a full 95 ft-lbs of torque

YOU can't say. I can't say. WE can't say because unless you designed the system, you have no clue how much braking force 2 brakes apply to the car. Remember that the brakes are applied to the front of one corner and the rear of the opposite corner and ONLY applied just long enough to straighten the car out. They don't lock up four brakes. They don't stay on longer than needed to straighten the car.

In fact, if you are driving in such a manner as not to drive your ass off the road, Stabilitrak won't kick in at all! It only kicks in when you have fish-tailed so damn bad that you are sending you spinning the rear end into a ditch.

Rob, I am really starting to wonder if you have ever engaged Stabilitrak at all off of an autocross track. Have you?

Are you trying to tell me that when you drive on local roads the stabilitrak is engaging and slowing you down mile after mile, corner after corner? Because stabilitrak is not supposed to engage at all until the car thinks you have completely lost control of it and it is running off the road and needs a very hard, immediate correction. Stabilitrak is NOT supposed to be something that is used to help you race through a curve at the correct cornering speeds. I have read review after review on the Ford Mustang's stability system which clearly lets a driver hang the tail out on a Mustang a good little bit before the stability every kicks in. So the brakes never engage driving a Mustang like that. I like to believe the GXP's system is similar. You can hang the ass end out a bit and Stabilitrak does not engage until the system thinks you've crossed the point of no return.

I would say any driver who is driving on the street with stability control engaging regularly is a dangerous driver and shouldn't have a license. That tells me, once he gets back into a RWD car without stabilty control, he is going to be fishtailing all over the road until he kills somebody or wraps his car around a telephone pole. Stability control is just for emergenices. I have heard it called "active handling" but I don't believe it. You should not be driving so wildly and dangerously that you otherwise would crash your car and stability control has to save you bacon time and time again. Not on the street. Not even on a track. It may come in handy on a track, but you shouldn't be driving so wild as to depend on it on a track and if you do, then you deserve all the nanny-induced braking you get.

I can't speak to autocross, and I am beginning to wonder if your entire outlook about the power-robbing effects of Stabilitrak aren't confined to autocrossing in parking lots, which is NOT what Stabilitrak was designed for.

The only reason I ever brought up stability control is to address the issue of the , quote, better handling car. Without stability control, a mistake will put a base Solstice in a ditch. With stability control, a mistake may well be recoverable and keep you on the pavement. The result of this is, on a track, a driver of a GXP has more breathing room to try to achieve the limits of tire adhesion becuase the risk is smaller - his rear will fishtail and correct itself while the driver of a base car will skid or spin.

So I simply asked, with that safety net available AFTER you lose all tire adhesion, how can it be that the base Solstice is a better handling car without that safety net?

[jimbo]

Originally Posted by JUSTICE I remember for certain that Road and Track had the same slalom of 67.0 for both cars and I think their skidpad number for the GXP was 0.86 if I recall. So that fills in two gaps for you jimbo.

OK, I'll update my list. Maybe we can get it filled out and detect a meaningful trend. My memory was that the GXP had slighly lower skidpad numbers but higher slalom numbers.

The lower skidpad numbers make sense to me. The car is heavier and it is all on the nose while the suspension is roughly the same and most importantly, the damn GS2 tires aren't any sticker than the pathetic RS-A's.

[LatinVenom]

OK Guys and Gals FOUND THE ANSWER! IS THE WEIGHT DISTRIBUTION OF THE GXP!!!

This time the car was checked to have a FULL and I mean FULL tank of gas plus the additional 22lbs lost to the exhaust system, and this time with the same tests it felt just as planted as the old car.
Also and this is for Jimbo, the tests were always made with TC OFF and ESC OFF.
Now that the car feels planted as it should it can also be push further, however what I find troubling is as the weight of the car gets unbalance, this is really noticeable once you reach the 1/2 tank mark and it gets worse from there. What I mean by this is that it no longer feels as planted as when you start it with the weight as balance as the factory wanted to be.
Please understand this is my opinion and my tests, all control to specific speeds and places.
My conclusion is that these 2 cars are so well engineer from the factory, that any deviation from the intended specs, will definitely affect the overall feel of both cars.

[vermontster]

I wish s-man would chime in,this could possibly amount to jack afterall

[Daywalker]

As far as Stabilitrac kicking in, here are my observations while at the limit. Sometimes it engaged too early, sometimes just right, and others I was wondering were it was at all. For me it was not consistant enough for me to anticipate when it would be activated. Also when trying to engage the ESC while testing, I was able to induce a full tail out drift, which I was surprised that ESC did not catch. As well as the ESC works, when running at 9 tenths it is just to unpredictable to produce the best times. For the street, rain and loose traction situations it works great. I also did notice it either cutting power or applying brakes, once it was triggered coming out of an apex, which I think is what RobL is referring to. I have not been able to run a stock Sol Z0K so I could not, and would not speak to a comparision of two cars.

[jimbo]

Originally Posted by LatinVenom OK Guys and Gals FOUND THE ANSWER! IS THE WEIGHT DISTRIBUTION OF THE GXP!!! Please understand this is my opinion and my tests, all control to specific speeds and places.

Your opinion is valid and important. I'm sorry to hear how touchy the GXP is to weight distribution, but we've learned something. I guess if you lighten the car, you don't want to lighten just the back end of it.

I don't find your conclusion too shocking in light of how touchy the car is about tire pressure.

I am used to RWD cars, but this world of powerful RWD cars with short wheel bases and nearly 50/50 weight distribution is going to be a brand new ball game for me. I've always heard they handle well but are sensitive to input, ie - harder to drive but more rewarding when driven right.

Thanks for sharing your experiences about how the car's handling feel with ballast in the rear end. Very interesting. I would never have guessed 20 or 30 pounds of weight at the back would have such a drastic effect on handling and handling feel. Thanks for sharing.

[JUSTICE]

So keep some extra weight in the back and lose some weight in the front. Or always keep the tank half full.

[jimbo]

Daywalker,

Thanks for the insight. I don't own either car, so while I am strongly opinionated, I don't have all the facts and I appreciate what others can teach me here, not just speculation. I didn't realize the Stabilitrak is being inconsistent. Hopefully that will be tuned better in later iterations. Thanks.

[jimbo]

So LV, are you sorry you got the GXP? Do you think you would have been happier just keeping the Solstice? Or are you pretty happy with the GXP?

[todd_raleigh]

Originally Posted by jimbo And this is why I feel sorry for LV, bird and Todd.

Don't feel sorry for me! I totally enjoy the GXP and would not switch back to the base. I'm not a professional driver. Just an average Joe who has one AX under my belt. BTW, I did have the rear diff on the base sol. I compared the handling on a curved road near my house. Speed was similar. I don't remember the level of gas in the tank. My reaction to the difference was more of a surpise than a major concern. But, I'm sure more sophisticated drivers have a different opinion than me. One more thing, I think the GXP is a smoother ride than the base...go figure.

[jimbo]

Todd,

Good to hear!

[LatinVenom]

Jimbo here is a quote from SM on the weight distribution when answering my question about the 22lbs difference.

....hmmm, curious. Take a 3020 car @ 53% front. That's about 1600 front and 1420 rear. Subtract 22 lbs from the rear, and the weight change is more dramatic than I thought - it becomes 53.4% - that's approximately the difference between the distribution of a base solstice and a GXP (maybe a bit less)....

[vermontster]

LatinVenom So that I understand you right are you saying that with the extra weight in back the car has less oversteer on corner exit? Any changes on corner entry?

[LatinVenom]

Jimbo,
I love my GXP because of the power increase that comes with it and the potential for increasing it, but at the same time I wounder how would my 1st 1K with the GMPP suspension upgrade I was going to do plus a Supercharger would have feel.
However after finding out about the weight distribution and how it affects the GXP, then how would the N.A. would have react to the additional weight of a Supercharger/Turbo and the less weight of a better exhaust system in the rear.
So now that I know the parameters of my GXP and it's behavior, I can learn to adjust and compensate for it.