Hi guys,

Hope someone here can help me out.. seems like I am in trouble.
I have just installed a GT2 Wing on my TT and every other things stay stock in terms of aerodynamic. (Stock F&R bumper, sides). But I have lowered the car with B16 and I am happy with it.

Here is the problem. After installing the GT2 wing, I went to on the highway for some fun also testing how the B16 has changed the car. I was going in the corner (not very sharp since its a pretty fast highway, like 30 degree maybe?), going like 170km/h, when i was turning, (sport mode on, not braking, foot 1/2 on the gas, front tires PS2 with 70% left same as the rear) feels like the front has so little grip that all the grip/weight are at the rear, no longer giving me the stable 4WD feeling from the 997TT!

Would it be the GT2 wing causing too much down force on the rear of the car so that I didn't feel anything from the front? Does this mean I need sth for the front? Maybe a GT2 front bumper, or at least a techart lip?

I am so sorry for describing the situation poorly, kinda hard to explain in words, but anyway, really hope you guys can help me out!

Thank you guys so much for reading my post in advance.

Cheers,

 

you may have unbalanced the car...the guys who designed it didnt intend for it to have only the gt2 wing without the front enhancements

 

I think there are several variables at play here. It could be too much downforce or it coudl be your suspension setup. If you got the b16's done at the same time as your wing, I would suggest you put the stock rear deck lid back on and see how the car feels then. This way you can at least narrow it down to exactly which mod is causing this lack of front end grip.

 

I would say try to adjust your suspension first. I have similar problem even tho i have full techart body kit but no-one back home know how to adjust the KW-V3 properly

 

i would bet it would be the suspension since you did both at the same time. maybe an alignment would help...

 

The Gt2 is a complete aero package, you can't mix and match pieces. You will need a GT2 front to balance it properly.

 

That makes sense, but isn't the GT2 front chin very similar to the Turbo? Will the minor differences in the front chin spoiler make that much of a difference and cause the noticeable instability that the OP is having?

I am having a GT2 wing installed on Monday and I currently have the front factory Aerokit lip... should I be worried? I think the aerokit lip may even be lower than the GT2 lip, however, its probably close.

 

Ha ha, this is word for word how my reply would be. (We are starting to think like twins.) Double change is not good and I do suggest to put the stock rear lid back on and test the suspension by itself.

FWIW, regarding the front spoiler and rear wing: It's not that the front lip balances the rear wing -- the front creates little down force -- but it's that the rear wing is made for the the rear suspension of the GT2 with its much higher spring rate.
I could well imagine that the higher down force of the GT2 wing presses down on the rear end of the Turbo, with its softer spring rate, and lifts the front up. We had a long discussion on this in a thread on rennteam.com a while back and I recall it was brought up that the force of the wing becomes significant at higher speed. This is consistent with what the OP is stating.

But this is all speculation. Bottom line is as Mike suggested: Change rear wing back to stock and see if it makes a difference.

 

Or get this instead...

 

The vented front air dam on the Gt2 is designed to create more downforce. I don't recall the exact numbers, but it is significantly more than the standard Turbo. Good point about the stiffer suspension (springs, bushings etc) on the GT2, gotta consider that too. But I think the problem here might have been so many changes at once, it's hard to evaluate.
Bobby, don't show me that picture any more....must resist.......

 

Thank you so much for all the useful inputs! Really appreciate them.
Now may try to get the old wing back on see if it makes the difference.
And today Ray@ROTtec Carbon has sold me and helped me install a very good quality front CF lip, I wanna see if this lip would help me on the downforce on the front. Hope it will!
Thx again everyone..

 

Doug...you know you want it...

 

At over 100 mph, changes in DF can certainly be felt, but I'm more inclined to think it was the suspension. Do you know your height measurements compared to stock front and rear? Spring Rates? Corner Weights? If all those things were not taken into account, you have taken a shortcut on modding the suspension and you're now paying the penalty for it.

 

Regarding front spoiler: You could try to change but I would be very much surprised that it would make a difference. Front spoiler is there to reduce air from coming underneath the car; it needs to below to the ground to work and I believe how close it is to the ground is more important than the slight change in shape between these lips.
In this sense, how the front spoiler works is very different from the rear wing, whose angle of attack, size, and height have very significant effect on the car's drag and lift.
(Front spoiler is also important in creating "ground effect," but our cars are too high off ground to have any of this.)

FWIW, the magazine Sport Auto tested both Turbo and GT2, and I believe the numbers are as followed, at 200 km/h:
Turbo: Front has LIFT of 8kg, rear has down force of 12 kg
GT2: Front has downforce of 9kg, rear has down force of 29 kg.
I always wonder about these numbers. For example the gas tank in front has capacity of about 50 liter = 50 kg? So does that mean the car is more stable with a full tank as 50 kg is a lot more than the downforce?
Regardless, it's true that the rear wing is a significant stabilizing force at speed. I don't mind messing around with front spoiler and side skirt, but to me the rear wing is not something you want to be very careful about.

There is a good article on this subject http://www.autozine.org/technical_sc..._aero.htm#Drag .
In the article is a table that shows that significant effect of the rear wing in a 996 Carrera. What's interesting is rear wing works to reduce lift (increase down force) BOTH front and rear.

<TABLE cellSpacing=0 cellPadding=3 width="70%" bgColor=#ffffcc border=1><TBODY><TR bgColor=#000000><TD width="30%"><CENTER></CENTER></TD><TD width="35%"><CENTER>Front lift (at 157mph)</CENTER></TD><TD width="35%"><CENTER>Rear lift (at 157mph)</CENTER></TD></TR><TR><TD><CENTER>Wing down</CENTER></TD><TD><CENTER>64 kg</CENTER></TD><TD><CENTER>136 kg</CENTER></TD></TR><TR><TD><CENTER>Wing up</CENTER></TD><TD><CENTER>5 kg</CENTER></TD><TD><CENTER>14 kg</CENTER></TD></TR></TBODY></TABLE>

One more thing you might want to consider: Sometimes after I have a significant change to my suspension, the car would feel "difficult" the first couple of weeks. Once I get used to the change, then it feels more stable.
Bottom line is I am STILL speculating. Have your mechanic check the coilover installation and alignment, and if your car continues to feel unstable, then you may not have much of a choice except return to stock wing.
Good luck and hope you'll find a solution!

 

Man that looks amaazing. What wing is that? Can you link the site please?