Need help eliminating oversteer

Rusty · 08-03-2018, 11:47 PM

Quote:

Originally Posted by Hotrodz

I need to see some pictures of your car she sounds bad *** and you got all the good stuff.

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Really.

Another question. How did you get 354HP with a Stillen G3 and FI LTH's? What else was done?

Hotrodz · 08-03-2018, 11:53 PM

Quote:

Originally Posted by robertkroll

The bite at the front is good, the oversteer is the issue. I am researching suspension alternatives for the rear that can improve the grip with new geometric angles since the car is lowered.

Copy that, my setup is somewhat close to yours. I have pretty much the same suspension up grades except for one way coilovers 14k front and 11k rear. I run no bar in the back as well. I run square but not on slicks, nt01's 315 30. I am lowered as well and have just a slight oversteer.

I mentioned this in another thread but in talking with a Nissan employee while looking at some Nissan race cars in their heritage collection he said you might want add some weight over your axles. He went on to say that every z back in the day had added weight in the rear. He the showed me a few cars with post over the rear tire well were they added the weight help the car with traction.

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robertkroll · 08-04-2018, 05:39 AM

Quote:

Originally Posted by Hotrodz

Copy that, my setup is somewhat close to yours. I have pretty much the same suspension up grades except for one way coilovers 14k front and 11k rear. I run no bar in the back as well. I run square but not on slicks, nt01's 315 30. I am lowered as well and have just a slight oversteer.

I mentioned this in another thread but in talking with a Nissan employee while looking at some Nissan race cars in their heritage collection he said you might want add some weight over your axles. He went on to say that every z back in the day had added weight in the rear. He the showed me a few cars with post over the rear tire well were they added the weight help the car with traction.

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I certainly don't want to add weight to the car. It's hard enough to be competitive against E46's. The car does perform differently on a full tank of fuel. Since we put the large cell into the car for endurance events, but you can't count on that because it is a dynamic change to the car. We custom built the cell to replace the stock tank and keep the fuel as low as possible.

Did I read correctly that you are running 315's square? WOW, that's a LOT of tire. The front bite is so good on the car, that we can't induce any slip on the 275 fronts, so the added weight just wasn't worth it to us. I notice that you also have VERY heavy springs. Did you do that to prevent squat and loss of camber through the suspension travel?

robertkroll · 08-04-2018, 05:42 AM

Quote:

Originally Posted by Rusty

Really.

Another question. How did you get 354HP with a Stillen G3 and FI LTH's? What else was done?

It's a bone stock motor (has to be for racing). There wasn't much magic done here, the exhaust has a lot to do with the performance. The car IS ear shattering at speed as a result, but I don't care who suffers as long as I have the power. When we have to muffle down for certain events, there IS a loss in power (Thank you Lime Rock Park). I have the car tuned at Vinny Ten Racing, and if you are running a VQR motor, I would strongly recommend them!

robertkroll · 08-04-2018, 05:46 AM

Quote:

Originally Posted by Rusty

Too add to that question. Is it tail happy all the time? Or at different corner speeds? What's your tire temps across the tires. What's your fuel level when it happens? How many heat cycles on the tires?

The car is tame in the straight braking zone and becomes slightly lose as you trail into the turn. You have to be careful not to carry too much speed or the back will start to wash out and this will destroy your turn. It's predictable for rotation at the apex which is helpful, but I would rather have the added grip. Once through the apex, the car doesn't let you go back to power without the back pushing out. You have to very gently add power through the track out without getting too excided, but as you get closer to a straight wheel, you can go back to power. I can hear the E46's get back to full power ahead of me. The crappy part is that I have the power on the straight, so I can reel them back in, but lose the distance again at the next corner.

The WORST thing about this is that we rent seats out for endurance racing and we use the car for instruction and when we put somebody in the seat with slightly less experience, it becomes a dangerous situation.

andy_meng1024 · 08-04-2018, 06:37 AM

I think this is your car. Nice mods.

http://www.zcarblog.com/for-sale-1/2...-370z-race-car

Spooler · 08-04-2018, 11:46 AM

What are your spring rates in? Pounds per square inch or Kilograms per mm.
Most folks on this board use Kg/mm. The hard core autocrossers and racers use Lb/in.
It's sounds like you have the suspension adjusted all whacky causing the oversteering issue.

Hotrodz · 08-04-2018, 12:43 PM

Quote:

Originally Posted by robertkroll

I certainly don't want to add weight to the car. It's hard enough to be competitive against E46's. The car does perform differently on a full tank of fuel. Since we put the large cell into the car for endurance events, but you can't count on that because it is a dynamic change to the car. We custom built the cell to replace the stock tank and keep the fuel as low as possible.

Did I read correctly that you are running 315's square? WOW, that's a LOT of tire. The front bite is so good on the car, that we can't induce any slip on the 275 fronts, so the added weight just wasn't worth it to us. I notice that you also have VERY heavy springs. Did you do that to prevent squat and loss of camber through the suspension travel?

I totally understand not wanting to add anymore weight being NA. When I have suggested this to others whether road or drag goers, the answer is the as yours...the car does hook better with a full tank of gas but is slower.

I run two sets of wheels one that is 18x11 +18 square with 315 30 tires and 18x10.5 +30 square with 295 30 on them. I am boosted so weight balance and grip is what I continue to push for. The nt01 in 315 are actually really good up front. Turn is good with an equally good initial bit and grip consistent through the turn in and exit. The r888 295 are good for about a session and half before they become greasy and do not hold their grip.

I just had my coilovers serviced and upgraded by Fortune Auto and they recommended that for my car setup to go with the heavy springs all around. I think you logic is spot for the reason why some companies recommend heavy spring rates. Not all do and some have more spring to rear than front. I believe HKS is that way.

Hotrodz · 08-04-2018, 01:11 PM

Quote:

Originally Posted by robertkroll

The car is tame in the straight braking zone and becomes slightly lose as you trail into the turn. You have to be careful not to carry too much speed or the back will start to wash out and this will destroy your turn. It's predictable for rotation at the apex which is helpful, but I would rather have the added grip. Once through the apex, the car doesn't let you go back to power without the back pushing out. You have to very gently add power through the track out without getting too excided, but as you get closer to a straight wheel, you can go back to power. I can hear the E46's get back to full power ahead of me. The crappy part is that I have the power on the straight, so I can reel them back in, but lose the distance again at the next corner.

The WORST thing about this is that we rent seats out for endurance racing and we use the car for instruction and when we put somebody in the seat with slightly less experience, it becomes a dangerous situation.

Thank you for providing detail on what you are experiencing. It is obvious you have a lot more track experience than I do and I hopefully we can find some solution to what you are describing. Although I might not be driving as aggressively as you are I know exactly what you are talking about when accelerating out of low to medium speed turns. I have thought it was and still maybe to a degree my inexperience and driving technique along with boost (torque) coming on strong and early. That said, if I must go to second gear I have to really be light on the throttle or allow the car to totally rotate beyond the apex to apply throttle many times I simply stay in third gear for risk of loosing to much time or spinning out. It is definitely annoying to run away from most in my run group only to be caught in the corners because of poor exit speed. I am not a fan of short twisty tracks because of this.

You said you were researching some geometric suspension alternatives, care to share what you have found so far? I know some of the folks that are doing the quarter mile and half mile thing are making strides in this area and it is very much on the down low as records continue to be broken in the straight line game.

Rusty · 08-04-2018, 01:32 PM

Because of the camber curve being what it is on the Z. Steep. Sometimes I wonder if we are running too much in the rear.

Hotrodz · 08-04-2018, 01:48 PM

Quote:

Originally Posted by Rusty

Because of the camber curve being what it is on the Z. Steep. Sometimes I wonder if we are running too much in the rear.

I reduced mine back to -1.8 from -2.0 but I got to sort things out again as my whole rear setup has changed again. I now have true coilovers and higher spring rate and the car sits lower. I have not been to the track since I changed things up, but she felt a lot more balanced on the dragon. I also softened the damping in the rear quite a bit. Out of 24 clicks I went with 10 in the rear and 12 in the front. Before the change on a slightly softer rear spring, 11k and a less aggressive damper, it was set at 18 clicks.

Mr. Kroll, are you on true coilovers?

cv129 · 08-04-2018, 03:12 PM

I believe JRZ only has true type for the Z34

Hotrodz · 08-04-2018, 03:18 PM

Quote:

Originally Posted by cv129

I believe JRZ only has true type for the Z34

I thought so, but didn't want to assume. Thanks....

robertkroll · 08-05-2018, 08:36 AM

Quote:

Originally Posted by andy_meng1024

I think this is your car. Nice mods.

http://www.zcarblog.com/for-sale-1/2...-370z-race-car

That’s her!

robertkroll · 08-05-2018, 08:43 AM

Quote:

Originally Posted by Rusty

Because of the camber curve being what it is on the Z. Steep. Sometimes I wonder if we are running too much in the rear.

The problem is that with a lowered car, the camber is set at a point in the suspension travel that is typically reserved for a “compressed” state. This leads to rapid and noticeable change in kenimatics when compressed further. This keads many people to over “spring” the car to prevent further geometric progression and loss of grip. This car is NOT designed to be lowered to this degree. I’m thinking of raising the ride height, installing spacers (or even the WiseFab kit). To change the kinematics to favor a bit of squat and body roll.

08-04-2018, 06:37 AM	#21 (permalink)
andy_meng1024 Premium Member Join Date: Nov 2009 Location: Taipei Posts: 233 Drives: 2012 370z Rep Power: 3382	I think this is your car. Nice mods. http://www.zcarblog.com/for-sale-1/2...-370z-race-car __________________ Current: 2015 C200 / 2018 Cayenne / 2012 370z / 2012 C250 Coupe Gone: 2013 Cayenne / 2004 Cayenne S / 2003 SL55 AMG / 2008 C300 / 2006 350z / 2006 C280 4Matic

08-04-2018, 01:32 PM	#25 (permalink)
Rusty Ronin Samurai - Assassin Join Date: Dec 2011 Location: Fayettenam,Pennsyltucky Age: 69 Posts: 35,530 Drives: 2011 Nismo GM 6M Rep Power: 2684439	Because of the camber curve being what it is on the Z. Steep. Sometimes I wonder if we are running too much in the rear. __________________ 浪人 - 殺し屋 "The Difficult Anytime, The Impossible By Appointment Only" http://www.the370z.com/members-370z-...o-journal.html

08-04-2018, 03:12 PM	#27 (permalink)
cv129 A True Z Fanatic Join Date: Jul 2011 Location: Dallas, TX Posts: 3,271 Drives: 09 Nismo, 16 Nismo Rep Power: 163996	I believe JRZ only has true type for the Z34 Hotrodz likes this. __________________ Setrab \| RE-71 \| SPL \| JRZ \| Nismo \| ARK \| Whiteline \| RacingBrake \| CJM Oil Pan \| Ti shield

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08-04-2018, 11:46 AM	#22 (permalink)
Spooler A True Z Fanatic Join Date: Jun 2014 Location: Ga Posts: 14,136 Drives: 2013 Nismo 370z Rep Power: 2684394	What are your spring rates in? Pounds per square inch or Kilograms per mm. Most folks on this board use Kg/mm. The hard core autocrossers and racers use Lb/in. It's sounds like you have the suspension adjusted all whacky causing the oversteering issue.