Solution to an annoying problem
Thread Starter
|
Registered User
Joined: Dec 2010
Posts: 497
From: South FLA
Rep Power: 38
Solution to an annoying problem
As some of you know, Champion Motorsports built one hellava GT2 for me completing it some months ago. The car runs like a banshee and everything about it is great ……….after 4 previous buids I can say this is truly an amazing car and second to none of my others.
I ran into an interesting problem and the resolution became one of creative thoughts and process by elimination.
As some of you may know, the GT2 computer will push the car into limp mode if it senses the front tire is larger than the rear tire. What good this does I have no idea but it is what it is.
Given my big HP and TQ I was keen to find the very best tires for the car offering handling and holding power. I was spinning under accelleration with R888's and MSC at 70-80 MPH. I knew I needed holding power but didn’t want to lose all the handling one would expect with DR’s. My first step was changing the wheels to 18” in an effort to expand the selection. I tried MT Street DR’s II. They certainly hold the power, but would "squash" because of the TQ and handling was horrible.
I had several things going against me relative to avoiding limp mode.
1. Given I have a GT2RS body kit I also had installed the more aggressive rear spoiler blade. This blade increases down force (over the std GT2) by as much as 200%+.
2. Given my ~ 750FT# of torque it has a tendency to “squash” the dia. of the rear tire under full load.
Upon installing the Mickey T’s I didn’t expect any problems but knew right away that the tires did not fill out the wheel-well. Further, as soon as I hit 80 mph I would start seeing signs of limp mode and by 120mph I was in limp mode. As I varied the PSI the limp mode problem would move (range start/stop) or decrease across the board.
I was bound and determined to fix the problem and found the solution in a slightly smaller front tire (NT01 235/35ZR18) and the NT555R in a 335 width and 18” dia. The NT555R holds my power just fine, takes off like its on a rail, low noise, comfort, has a stiffer sidewall than most DR's. I started playing with tire pressures and found it was a key ingredient to the solution. Discovering this I identified the “perfect” pressure and used nitrogen to insure variations are minimized. The NT555R actually handles very well and is better on wet roads than most.
The ultimate solution………the GT2RS Rear Spoiler blade. I switched out to the std GT2 blade and my problem has disappeared up to 160 MPH. During ¼ and 1 mile runs I will remove the blade altogether or I may try to reverse engineer the profile of the blade and make an aluuminum one with zero incline.
I fully intend on upgrading to ~ 1300-1400 BHP in the future and given the increased TQ I am sure the problem will pop up again. I have already found a front tire which will resolve what I believe will happen.
The tire/wheel combo fits the car very well...I am pleased. Time to race!!!
Hope this helps us crazy people whom want BIG hp GT2’s.
</O
>
<O
I ran into an interesting problem and the resolution became one of creative thoughts and process by elimination.
As some of you may know, the GT2 computer will push the car into limp mode if it senses the front tire is larger than the rear tire. What good this does I have no idea but it is what it is.
Given my big HP and TQ I was keen to find the very best tires for the car offering handling and holding power. I was spinning under accelleration with R888's and MSC at 70-80 MPH. I knew I needed holding power but didn’t want to lose all the handling one would expect with DR’s. My first step was changing the wheels to 18” in an effort to expand the selection. I tried MT Street DR’s II. They certainly hold the power, but would "squash" because of the TQ and handling was horrible.
I had several things going against me relative to avoiding limp mode.
1. Given I have a GT2RS body kit I also had installed the more aggressive rear spoiler blade. This blade increases down force (over the std GT2) by as much as 200%+.
2. Given my ~ 750FT# of torque it has a tendency to “squash” the dia. of the rear tire under full load.
Upon installing the Mickey T’s I didn’t expect any problems but knew right away that the tires did not fill out the wheel-well. Further, as soon as I hit 80 mph I would start seeing signs of limp mode and by 120mph I was in limp mode. As I varied the PSI the limp mode problem would move (range start/stop) or decrease across the board.
I was bound and determined to fix the problem and found the solution in a slightly smaller front tire (NT01 235/35ZR18) and the NT555R in a 335 width and 18” dia. The NT555R holds my power just fine, takes off like its on a rail, low noise, comfort, has a stiffer sidewall than most DR's. I started playing with tire pressures and found it was a key ingredient to the solution. Discovering this I identified the “perfect” pressure and used nitrogen to insure variations are minimized. The NT555R actually handles very well and is better on wet roads than most.
The ultimate solution………the GT2RS Rear Spoiler blade. I switched out to the std GT2 blade and my problem has disappeared up to 160 MPH. During ¼ and 1 mile runs I will remove the blade altogether or I may try to reverse engineer the profile of the blade and make an aluuminum one with zero incline.
I fully intend on upgrading to ~ 1300-1400 BHP in the future and given the increased TQ I am sure the problem will pop up again. I have already found a front tire which will resolve what I believe will happen.
The tire/wheel combo fits the car very well...I am pleased. Time to race!!!
Hope this helps us crazy people whom want BIG hp GT2’s.
</O><O
Last edited by Slow911TT68Tip; Apr 22, 2012 at 06:37 AM.
Wierd Science.....I would not have guessed that too much downforce in back was the culprit. Deductive reasoning at it's best. Well done!! (and, thanks for sharing this info with us.)
Best of luck with the future mods. Just keep the damn thing on the ground.
Best of luck with the future mods. Just keep the damn thing on the ground.
Registered User
Joined: Feb 2012
Posts: 230
From: Right Lane
Rep Power: 41
Car looks very nice. I Currently run the MT DR 18" on my 997TT with 245/40/18's up front. This is at the same .7 differance front to back like stock. When I ran the 335 out back it sure looked mean, but needed to be paired with a much wider tire up front (More understeer) With that much power, engine in the back and wider front fenders than a standard 997. I would run a much wider front tire. Ultimately how much HP did it make at Champion?
Thread Starter
|
Registered User
Joined: Dec 2010
Posts: 497
From: South FLA
Rep Power: 38
Car looks very nice. I Currently run the MT DR 18" on my 997TT with 245/40/18's up front. This is at the same .7 differance front to back like stock. When I ran the 335 out back it sure looked mean, but needed to be paired with a much wider tire up front (More understeer) With that much power, engine in the back and wider front fenders than a standard 997. I would run a much wider front tire. Ultimately how much HP did it make at Champion?
~845 WHP on 68mm VTG's
Registered User
Joined: Oct 2008
Posts: 501
From: S. Florida
Rep Power: 48
Good god man...that car is a monster! I saw it while she was under the knife at Motorsports. Would love to see the car in person one day....maybe when ur at CMS I could come see that beast.
Ken
Ken
Trending Topics
Thread Starter
|
Registered User
Joined: Dec 2010
Posts: 497
From: South FLA
Rep Power: 38
Hi Ken,
They just brought it back today after an oil change. I will let you know for next time. That would be the turbo upgrade to bring (hopefully) 300-400 more BHP.
BR,
Paul
Registered User
Joined: Oct 2008
Posts: 501
From: S. Florida
Rep Power: 48
Ken
Thread Starter
|
Registered User
Joined: Dec 2010
Posts: 497
From: South FLA
Rep Power: 38
I just spit out my beer!
Registered User
Joined: Sep 2009
Posts: 2,658
From: GTA, Ontario, Canada
Rep Power: 236
Is it an upgrade to the 68vtgs or are you changing to a different type of turbo? Have you had the chance to get any pbox numbers on this monster? Enjoy!
Thread Starter
|
Registered User
Joined: Dec 2010
Posts: 497
From: South FLA
Rep Power: 38
Changing to a different type from 68mm VTG's but have not made any determinations yet. I will be gathering data within the next 2 weeks.
