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

[todd_raleigh]

What percentage of the driver's weight goes toward the front and back? Is it 50/50?

[SolAnderson]

Sounds like we have an excuse to install that 1.5 extra cf box in the trunk that RPI is working on Supersize me trunk please

Battery relocation!!!


Assuming battery will fit (optima?) and that it is strong enough, and that there aren't any insurmountable obstacles related to keeping stray spark away from the gas tank etc.

[mena661]

Originally Posted by todd_raleigh What percentage of the driver's weight goes toward the front and back? Is it 50/50?

I would say the driver weight is more towards the back. You're basically just in front of the rear tire.

[SolsticeMan]

Originally Posted by JUSTICE Jimbo, I completely agree with you. As far as the traction and stability control goes, I'm not sure. It's a factor, someone else will have to make a comment about that. I'm not saying that I personally know for sure the GXP doesn't handle as well, because I can't. Based on several opinions of others stating it does not handle as well, I just cannot ignore that. I like to hear opinions of people who have driven both, state their opinion, and then say what they think the reason is. I'm just a little uneasy about there being this much doubt about the handling of a performance model compared to a base model. I'd rather 90% say it definitely handles better, then 70% say they're not really sure if it handles better or at least it doesn't feel like they'd want it to. It would be great to see more hardcore evidence, but sometimes even when the numbers look good, it just still doesn't feel right.

I found the competitive mode quite liberating. Lets you do burnouts, and quite a bit of shennigans, but still have the 'safety net' available just in case I happen to so something stupid...

It's simple, too. Start the car, tap-tap on the ESC button, and off ya go. If you have a nice straight launch with no rotation of the car (no steering and no fishtailing) , 1/4 mile times are pretty much the same as if you run the car with ESC disengaged. About 14ish @ 98 or 99 mph.

[JUSTICE]

I thought if you hit it twice it turns off the ESC and the traction control?

[SolsticeMan]

Originally Posted by 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.

Well, I'm not surprised. It's also not likely to be the 'engineering' that creates this sensitivity - it's the oversized tires.

I've also had the opportunity to 'plow' snow in a GXP. I'm not kidding, either - and to have a car equipped with 'summer only' tires be able to get through 4" of snow is downright AMAZING...

...but THEN I wonder, would the max lat and the handling be like if this wasn't that good in the snow? My answer is, of course, the way the car feels on RE050A PPs, or GS-D3s.

However, I have never been in a car that is so sensitive to small variations in alignment when it comes to grip, nor have I ever been in a car that is so damn fussy about tire pressure. Sometimes, you can almost 'feel' the car change on an autox evaluation, as each successive test lap increases the temperature and tire pressure.

Your post gives me a clue - changing the weight distribution is changing the basic part of the understeer equations, that of cornering stiffness and the load on the tire. So, armed with this new knowlege, LV, what do we do next?

This might be one of the first RWD cars to come along where adding weight is the thing to do in autocrossing .

[SolsticeMan]

Originally Posted by SolAnderson Sounds like we have an excuse to install that 1.5 extra cf box in the trunk that RPI is working on Supersize me trunk please Battery relocation!!! Assuming battery will fit (optima?) and that it is strong enough, and that there aren't any insurmountable obstacles related to keeping stray spark away from the gas tank etc.

Nah - BMW and GM have been putting batteries in the trunk for years.

(nearly all BMWs. Delta-platform ne Cobalt, ION, and HHR... )

[SolsticeMan]

Originally Posted by JUSTICE I thought if you hit it twice it turns off the ESC and the traction control?

Nope, hitting it twice only turns off the traction control (the part that yanks engine torque to control wheelspin - which ALSO allows turbo to spool down ) and moves you to a competitive mode with different, performance-oriented ESC tuning.

I can definitely feel the difference between one-tap (Traction off and normal ESC) and two-taps (traction off and Competitive ESC).


I'm still faster on an autocross course with everything off, but on a minute-10 course, it's a demerit of about 2 seconds or more with everything on, another 3/4 second better with traction off, ANOTHER 1/2 second or so in competitive mode, and fastest when everything is off (assuming you're on your game).

On stock tires, I need to add. Change the tires, and any runs with the traction on is totally F*ck3d up. Lots of *traction* messages, and the friggin' light blinks like a turn signal whenever the boost spools up... and then spools down... and then spools up....

[LatinVenom]

This might be one of the first RWD cars to come along where adding weight is the thing to do in autocrossing

If I was autocrossing as I used to, then I would start with a full tank of gas and if I had a modify exhaust system would put the weight back in the exact same place as the original muffler, then try different tire preasures.

Your post gives me a clue - changing the weight distribution is changing the basic part of the understeer equations, that of cornering stiffness and the load on the tire. So, armed with this new knowlege, LV, what do we do next?

I am sure you are thinking shocks, but I would still would want to play with the springs in the rear ONLY, but I think GM or GMPP is the one that needs to step up and give us an upgrade, they certainly have the knowledge to get this car (GXP) to be a bit better handling contender.

[snaponbob]

Had about 15 runs on Saturday at a test & tune on a very technical 45 second course. The day started with a bit over 1/2 tank of gas. My RL has the MF 3" cat back, 1.75 deg neg front, 1 deg neg rear, 245/35X18 Hoosier A6's. As the day went on I found that the initial pressures of 30/29 was too low. Miles at Tire Rack has suggested 29/28 A6s. Don't know. Mine were roliing over too much at both ends. Tire temps and chalk marks helped me settle in at 34/32. I ran with the ESC in both Comp Mode, and OFF. Frankly, I think I needed the Comp Mode to help me a bit, and my best times were in Comp Mode. And I wasn't far off the local A/S hot shoes. It was a productive day. Sunday was a 55 sec average course and less technical, but still demanding. First and second runs were miserable with the tires at 33/31. Reset them at 35/32 and the car was much better. Also, FULL gas tank.

What have I learned? 1) Full tank makes the car feel more balanced and stable. 2) I now have a 3x5 card that says "COMP MODE" that gets stuck in the tach after each run. Don't ask? 3) The realignment made a HUGE difference. More negative should help, but I want to drive the car on the street without killing tires. 4) Tire pressures are a function of chassis setup, tire type, and driving style. As I learn this car and get smoother (and that is happening already) I can foresee the pressures coming back down 1 or 2 points. 5) A/S is still going to be a Honda S2000 class. They can go 62-63 mph in second, and we can't. It WILL matter. But with all the torque we have, short shifting will be the answer. 6) I am convinced that when hammered in second gear this car may be sensing demand and producing more power than on the street when we jsut "run through the gears". Either my car is adjusting to the MF cat back, or it is responding to demand differently than on the street. Sounds absurd, but on certain portions of the course I had traction issues well into second gear, on dry asphalt, and going nearly straight in comp mode. 7) For the first time I could hear the turbo spooling up and popping off. There seemed to be a lot more stuff going on as I "worked" the car harder. And this with a very good fitting helmet that blocks a lot of noise.

A lot of this can be explained away, and I understand that. Bottom line, this is a LOT of car, and the right driver is going to be in the hunt at divisionals and nationals. I lot will depend on the speed of the course. If GM fixes the gearing (two edged sword there for current owners), or the right 40 series tirecomes along (say a 255-265/40X18 that has stiff enough sidewalls AND mounts up properly) the GXP/RL will be a real force in A/S.

[MemphisReighns]

I've resisted commenting in this thread, but I think I will now.

First my GXP now has the SOLO "race" exhaust, but I've not yet run it to the alignment shop which will happen this week. At that point I'll be dialing in 2.5 front camber, 1.5 rear, and 0 toe. Here are my opinions on what's been floated here:

Rear caster: shouldn't matter one iota since caster directly affects steering angles. I'd pull out some sources for this, but I think this is a dead horse.

Twitchy Rear end: Simply, the power really changes this car. I drove a regular NA and while i liked it, i thought it had too much chassis for the engine. Now the GXP is nice since I feel that I can balance the car with the throttle. But i will say that the GXP is way more forgiving feeling than the S2000 i drove. Once I get it onto a AutoX course I'll be better able to judge.

Factory alignments: I have never seen a car roll off the truck with a good alignment. in some way they will all be off. If this car is like the S2000 it can be transformed with a good alignment. You could take an S2000 from being a twitchy mess to a realtively stable car by simply getting the alignment right. I'll report on mine figures once I get it to the shop.

Gearing: That is going to be the achilles heel of this car. That said, I think that it can be developed into a winning car. Is it going to win Nationals? Hard to say the S2000s and C4 Vettes have tons of development in them, and the class is hotly contested with some really good drivers. I think the key is going to be managing shifting into third and finding the places where you can exploit the car's superior mid-corner grip.

Springs: The ZOK springs might be the way to go if they are let out in the wild. That said, I do think the car can use some firmer compression damping. I'm going to look at what Bilstein can do for me once I get a chance to drive the car on race tires.

Tires: I tend to be of the school, "stuff what ever tires you can under the car and deal with the results". Gearing aside, I think wider is better if they'll fit on the rim. Seeing that, I doubt that we'll see anything other than the current sizes (although a nice 265/40 would really fit the bill - Hoosier are you listening?)

There is an old saying that's more fun to drive a slow car fast than a fast car slow. I think that's the difference between a NA and GXP Sol.

[Krazed Kanary]

Originally Posted by snaponbob Had about 15 runs on Saturday at a test & tune on a very technical 45 second course. The day started with a bit over 1/2 tank of gas. My RL has the MF 3" cat back, 1.75 deg neg front, 1 deg neg rear, 245/35X18 Hoosier A6's. As the day went on I found that the initial pressures of 30/29 was too low. Miles at Tire Rack has suggested 29/28 A6s. Don't know. Mine were roliing over too much at both ends. Tire temps and chalk marks helped me settle in at 34/32. I ran with the ESC in both Comp Mode, and OFF. Frankly, I think I needed the Comp Mode to help me a bit, and my best times were in Comp Mode. And I wasn't far off the local A/S hot shoes. It was a productive day. Sunday was a 55 sec average course and less technical, but still demanding. First and second runs were miserable with the tires at 33/31. Reset them at 35/32 and the car was much better. Also, FULL gas tank.

from the tire temp readings we took yesterday (Longacre recording contact pyrometer) on 285 30 18 A6s you're going to want more camber front and rear and ~ 10# more pressure in the front tires and 5# in the rear. More camber will not have any serious affect on street tire wear, especially if you rotate the tires front to rear every couple of months. Flip them on the wheels after 15K miles.
We ran our first set of Hoosiers with -1.9 front camber and corded the edges after ~ 40 30 sec runs at a T&T.

[JUSTICE]

Well, for those of you who are just using the car on the street, are you most of you just having it aligned to what the factory specs are supposed to be or are you going to tell them to dial in what you want? Obviously after I get my new wheels and tires on, I'll have it aligned, especially since my rear wheels will be wider then and the wheels will be one inch larger in diameter but the overall diameter will be about the same as stock since I'll use lower profile tires.

So my question, since I understand the basics of camber, toe, and caster, but have no idea how they will change the handling/cornering, which numbers are best, and how much to change, should I just take it to the shop and say "align it", or would anyone recommend settings that would be better than the factory specs?

[snaponbob]

Originally Posted by Krazed Kanary from the tire temp readings we took yesterday (Longacre recording contact pyrometer) on 285 30 18 A6s you're going to want more camber front and rear and ~ 10# more pressure in the front tires and 5# in the rear. More camber will not have any serious affect on street tire wear, especially if you rotate the tires front to rear every couple of months. Flip them on the wheels after 15K miles. We ran our first set of Hoosiers with -1.9 front camber and corded the edges after ~ 40 30 sec runs at a T&T.

BARELY corded a front tire this weekend. I am going to flip the fronts and just kill them again before I grab another pair that I have. Are you suggesting 44 PSI in the front and mid to high 30's PSI in the rear? WOW. Hell, I'll try anything, but that sure sounds high. Not saying you are wrong, more a reflection of surprise. What camber/caster settings are you suggesting?

[brentil]

Originally Posted by SolsticeMan This might be one of the first RWD cars to come along where adding weight is the thing to do in autocrossing .

We're really re-writing the auto-x book here with our cars.

Drop the tire psi instead of increase. Add weight instead of removing it.

What's next, larger diameter tires so we can overcome our gearing issues?