- Joined
- Jun 18, 2001
Book it, done
1.1g lateral in a Grand National?
- Thread starter Turbo6inKY
- Start date
Book it, done
- Joined
- Jun 18, 2001
Here's my best run from the left side course:
And for the record, I drove like crap. DFL. But the car works. My harness bruised my chest.
And for the record, I drove like crap. DFL. But the car works. My harness bruised my chest.
- Joined
- Jun 18, 2001
It's less complicated than many make it out to be. You need to improve the front suspension geometry and stuff giant tires under the car. In my case, I got Speedtech front control arms, loaded them with taller lower ball joints, aligned with as much caster as I could get, put a Watts Link in the back to keep the rear end from steering the car, put Moog 5660 springs in front and CC651 cargo coils in back with Bilstein shocks from Autozone, and put 275/35R18 BF Goodrich Rival S tires on 18x9.5 rims on it.
The wheels and tires cost more than the suspension parts. It's all about the tires.
SpeedRacerX
Well-Known Member
- Joined
- Jan 20, 2014
Can you post some pix of the car and stance? Was fitting that size wheel and tire up front hard?
Great job with this. It's awesome to see a GN handle like this.
Any tradeoffs on the street?
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Great job with this. It's awesome to see a GN handle like this.
Any tradeoffs on the street?
Sent from my SAMSUNG-SM-G900A using Tapatalk
- Joined
- Jun 18, 2001
The stance isn't really that impressive. It's just a smidge lower than stock ride height due to the taller front ball joints. The suspension on these things really needs to be close to stock height or it doesn't work right. I still have stock swaybars, too. A front MonsterBar is on my birthday list.
Fitting the wheels up front wasn't hard. I downloaded the worksheet from Weld and measured everything three times. They rub at full lock, but not in operation. I have a Wilwood 140-2508 brake kit in the front, which widened the front track by 2", so my offsets in the front are different than what you'd need with stock brakes or one of the other kits you can buy. The rears don't touch anything, but I also have a Watts link, which prevents the axle from moving laterally, so I was able to get super close to the frame in the back.
Measure and consult with the wheel maker. Each one of these cars is a bit different and those differences start to really matter when you're up against the limits like this. But for people that want the numbers, the wheels are Weld RT-S71Bs in 18x9.5. 4.7" backspace in the rear with no spacer, 6.7" in the front with a 1/4" spacer.
Tradeoffs on the street are nil up until about 65mph, then it starts to shake. Turns out Weld can make a beautiful and light wheel, but the rears I got aren't actually round. They have a LOT of runout, which is disappointing considering how much they cost. They balanced, but it wasn't easy. I'll be measuring the runout with a dial indicator tonight and writing them a letter. Their policy is no replacement if a tire has been mounted, but I'm not sure how somebody would discover their wheels were not round until they were up on the balance machine. The front wheels are perfect, so I don't know what happened. We shall see what happens after I contact them. I just got them last week and had to scramble to make the event.
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SpeedRacerX
Well-Known Member
- Joined
- Jan 20, 2014
Very cool. Thanks for the detail.
How do you deal with the auto transmission and turbo spool on the twisties i.e. having not enough boost or too much boost, spooling through the transition to braking, etc? I'm sure it's fun yet challenging.
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How do you deal with the auto transmission and turbo spool on the twisties i.e. having not enough boost or too much boost, spooling through the transition to braking, etc? I'm sure it's fun yet challenging.
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- Joined
- Jun 18, 2001
Spool time is certainly a consideration. I have a PTE 5658 (I think? Maybe a 5856? I can't remember), and it's just a tad big for this stuff. I rebuilt the engine in 2014, and recammed it and had the heads ported, so it makes lots more down low before the the turbo spools up than it did stock. I also have a 10" 3100 stall torque converter in it, which really woke the car up.
Basically, you want to balance the turbo and torque converter combo so that when you step on the gas coming out of a turn, the turbo spools up as quickly as possible as smoothly as possible. You don't want so much lag that you bog initially, then suddenly hit boost and upset the chassis. It's about balance and driveability and less about maximum power.
And you absolutely must install a shift kit and an additional transmission cooler. A power steering cooler is also a good idea.
And then there's the little things. Like this weekend, launching the car on Rivals on concrete, I was pulling 0.5G accelerating off the line. That was enough to cause my brake light and cruise control switches to fall out of those cheap push-in mounts under the dash. I had to cram my hand through the fuse box opening to shove them back in twice this weekend. I'll need to figure out a better way to retain those.
And brakes. Stock size brakes with good pads are fine for this. I had big troubles with my vacuum conversion and autocross, though. Manifold pressure always found its way into the booster and I had no assist initially, followed by four wheel lockup halfway through the braking zone when the vacuum came back after getting off the throttle. I finally swapped out for a manual master. Telemetry shows I'm able to brake at least 1G, so I think the only thing you'd gain from a hydroboost is extra weight and flat spotted tires. I am very much looking at the new aluminum drums Kirban is about to start selling. I think with the reduced weight and better heat shedding, they might be almost if not just as effective as a rear disc conversion without any of the cost or hassle.
Basically, you want to balance the turbo and torque converter combo so that when you step on the gas coming out of a turn, the turbo spools up as quickly as possible as smoothly as possible. You don't want so much lag that you bog initially, then suddenly hit boost and upset the chassis. It's about balance and driveability and less about maximum power.
And you absolutely must install a shift kit and an additional transmission cooler. A power steering cooler is also a good idea.
And then there's the little things. Like this weekend, launching the car on Rivals on concrete, I was pulling 0.5G accelerating off the line. That was enough to cause my brake light and cruise control switches to fall out of those cheap push-in mounts under the dash. I had to cram my hand through the fuse box opening to shove them back in twice this weekend. I'll need to figure out a better way to retain those.
And brakes. Stock size brakes with good pads are fine for this. I had big troubles with my vacuum conversion and autocross, though. Manifold pressure always found its way into the booster and I had no assist initially, followed by four wheel lockup halfway through the braking zone when the vacuum came back after getting off the throttle. I finally swapped out for a manual master. Telemetry shows I'm able to brake at least 1G, so I think the only thing you'd gain from a hydroboost is extra weight and flat spotted tires. I am very much looking at the new aluminum drums Kirban is about to start selling. I think with the reduced weight and better heat shedding, they might be almost if not just as effective as a rear disc conversion without any of the cost or hassle.
achalmersman
Well-Known Member
- Joined
- May 28, 2012
The most accurate way to measure the radial and lateral runnout of the wheel is with the tire unmounted using the "measure bare rim" on a Hunter Road Force balancer. I do this with most new aftermarket wheels that I have any question im my mind as to if they are round before I mount tires. If you take your wheels to a shop that has a road force balancer they can measure the assembly uniformity, rim runout, and move the tire on the wheel to get the best possible match with that tire / wheel assy. You can locate a shop by entering your ziocode at www.gsp9700.com good luck and sweet car!
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Sent from my VS990 using Tapatalk
SpeedRacerX
Well-Known Member
- Joined
- Jan 20, 2014
Having a wheel/tire combo road force balanced versus non road force balanced solved years of shaking/vibration problems on my Pontiac G8 GT that the dealer nor any normal place could solve. I highly recommend it.
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- Joined
- Jun 18, 2001
Yeah, my guy doesn't have a force balancer and neither of us thought to check them before mounting. I checked them for clearance on the car and everything before putting the tires on, but it never occurred to me the QC would be bad enough on something this expensive that this much runout would make it out of the factory.
I'll do the best I can with a dial indicator and see what Weld says. If they tell me to take it to a place with the fancy hunter machine to verify the measurements, I certainly will. If I'm stuck with them, I'll get a tire trailer and put some comfy all-weathers on my cast 17" rims for transit.
RmvBfrFlght
Well-Known Member
- Joined
- Sep 28, 2007
The switches have standard threads on them, CC is 5/8-18 and the brake light is 1/2-20. Can use thin jam nuts to retain them. Note that the CC switch doesn't have a lead-in to the threads. Will need to trim down the end so that the nut starts onto the threaded area.
RemoveBeforeFlight
- Joined
- Jun 18, 2001
Sweet. I knew this problem had been handled by people on here before. I was pulling janky 2.4 60' times Saturday, so just about everybody on here comes out of the hole faster than that and had to have run into this issue. Thanks!
- Joined
- Jun 18, 2001
Not hard at all. I have the old ATR 2.5" exhaust with side-exit pipes and pit bull mufflers under the floorpans from 2001, and it clears just fine. The Watts mounting frame goes in the space behind the axle where the stock muffler went. Plenty of room. The only interference issues would be with pipes going over the rear axle and the tires rubbing the mounting bolts if your tires are REALLY close to the frame.
- Joined
- Jun 18, 2001
It's Harry's Lap Timer, it's an iPhone app, so it's using the accelerometer inside the phone. The main video is a GoPro Hero 3, and in-car is the iPhone camera pointed at my face. The App controls both cameras, and can merge the video and do the overlay all on the phone.
- Joined
- Jun 18, 2001
I'm not sure what you're asking.
