vqliam

Hey everyone, I’m super stumped on this one

I recently installed FUCA, toe arms, Silver’s coilovers, 18x10.5 wheels fitted with 275/35 all around on my 2007 350Z. Got it aligned and the only thing that couldn’t be adjusted was rear camber, so I’m left with whatever camber comes with lowering the car to where it sits now. (Around -3°) The front also sits at -3°. I can drive it around right curves on the highway and it takes them extremely well, but as soon as I get on a left curve, the oversteer/understeer is inconsistent.

I checked everything under the car and it all seems tight/in good shape. Just installed the Z1 subframe bushing collars as well. I do have the solid diff bushing to install but I don’t believe that would cause cornering issues like the one I’m having. (So many people let the diff bushing go and not one has had this issue.)

I’m running Federal SS595 all around too. Preload on the rear coils should be at about a couple mm. The dampening is adjusted to 4 clicks more on the firm side. I also have the open diff as my Z is a base model. ):

I don’t know what the issue would be as it only happens in 1 direction and while braking/downshifting. I don’t have the alignment sheet but toe all around was within 0 to 0.10. (Again it’s not on both turns just lefts.)

Any help would be appreciated!!

dkmura

iTrader: (64)

You'll need to explain what you mean by "the understeer/oversteer is inconsistent" going around left landed turns. The dynamic handling of any car will shift depending on driver input, road camber, elevation changes, and other factors. My street and race Zs are set up for slight understeer on corner entry, going to neutral through the apex and shifting to slight to medium oversteer (depending on throttle application) on corner exit. What is your Z doing?

vqliam

I mean more that it feels like the front dips in and then the rear catches up, whether I let off the throttle or not. The back end slingshots to catch up and the car feels like it wants to go sideways. I’ll have the wheel turned to follow the curve of the road and even with no bumps I’ll have to go back and forth to not either go into the other lane or the guardrail, as the backend seems to float behind me.

dkmura

iTrader: (64)

OK- that sounds like there may be a problem with damping. I've never heard of the coilovers you're running, but with a porpoising problem like you describe, it's the first thing I'd look at. Might be a blown shock, or some other component failure.

Also what kind of toe settings are you running?

vqliam

I just installed them and only have driven the car a few times since install because of this issue. Toe was between 0 and 0.10 I believe in the rear. I can change the damping to be softer as they’re pretty firm as it sits now, and report back after that.

I was reading a thread with a similar issue but it ended up being the camber arms, which I have the OEM ones and they appear to be fine all around.

dkmura

iTrader: (64)

Are the coilovers adjustable for both bounce and rebound? Or is there only a single adjustment? If so, make sure to go full soft on all four corners to ensure uniformity in response.

I've never known rear camber arms to be a cause of porpoising like you describe. The aftermarket ones on my street Z do provide additional range of toe and camber adjustment. Due to SCCA rules, I must use the OEM camber arms on my race Z. It's quite low and in the photo below, you can see what it looks like making a high-speed turn to the right (left side loaded).