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370z Time Attack Build!

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Hello all,

I joined racecraftHQ in hopes of expanding my knowledge of motorsport. I am no mechanic, just an enthusiast. I have bought a 370z back in 2009 during college with eventual hopes of tracking the car. I am finally in a position in which I can focus on tracking my car. Below are some pictures of the cars current state and what I'm currently working on.

Instagram: @z34_motorsport

https://ibb.co/Lhzw978

https://ibb.co/0yxszhB

https://ibb.co/JpP8g2F

Currently, I am finally transitioning from HPDE (high performance driving experience) AKA "for fun" tracking to Gridlife Time Attack "Street" class competitive racing. I am looking to perfect my suspension setup, weight distribution, and driving skills.

January 2021 - Working on Bump, Droop, Roll Centre, & further "perfecting" my suspension. I have just purchased a set of Fortune Auto coilovers and have followed the video guide to properly install my coilovers. Here are my measurements:

Bump, droop, & ride height measurements from top of center cap to center of fender:

Rear:

Fully Compressed (no spring): 317.5 mm

Full droop: 444.5 mm

Ride height (car on ground with spring): 352.425mm

Pics of rear:

https://ibb.co/V28dnVB

https://ibb.co/L0b2zpW

https://ibb.co/HC9vg9c

Front:

Fully Compressed (no spring): 311.15 mm

Full Droop: 444.5 mm

Ride Height: 342.9mm

Front Pics:

https://ibb.co/G5ZzgSF

https://ibb.co/gdtDwpT

https://ibb.co/JRFmzCZ

I may need to raise the front up a bit.

I know I need to corner balance the car to dial in each individual corner but since this is the first time I've done this, I'd like to know if I'm on the right track in terms of measuring full bump and full droop. The full bump setting is set to just barely tuck the fender. (even though I have a LOT of room for compression on the inside of the fender in the rear).

Next: I will be doing some research on the Z forums to see what alignments other time attack competitors are running and use that as a baseline to go off of since I have 0 data on tire temps, pressure, etc. After that, I will be corner balancing the car, then taking it to get aligned. Once this is all taken care of, I'd really like to learn how to measure roll center and try to dial in rebound.

Looking for some feedback, I'm a noob so all help is appreciated!

Hi Benny, nice work on the build. I can tell by the quality of your questions and the work you've put in so far you're on the right path!

My first question is- the measurements you've given for "fully compressed", you say the springs are removed but are these measurements with the bump stops removed as well? You should do your "fully compressed" measurement with the bump stops removed if you aren't already.

The normal starting point for setting your "bump to droop" ratio is to aim for roughly 2/3 of your travel available in compression and 1/3 in droop. From the measurements you've given it looks like only 1/4 of your available travel at each end of the car is available in compression, are your numbers right?

I assume you've watched the Wheel Alignment and Corner Weighting courses where there is some discussion on this topic, but here is the general process I recommend:

-Remove the spring and bump stop from each damper

-Reassemble the suspension and re-fit the wheel

-Fully compress the suspension so the damper is fully closed

-Adjust the lower collar of the damper (sometimes called lower mount) such that there is no contact between the tyre/wheel and chassis/inner guard

-Measure the fully compressed and fully extended positions of the wheel

-Refit the spring and set your ride heights using the spring perch

-Measure the wheel position at ride height

-Calculate your bump to droop ratio

-Adjust the lower collar/mount and offset the spring perch position as required to correct the bump to droop ratio

-Iterate through this process, always making sure there is never any way the tyre can contact the chassis at full compression. You'll often end up having to compromise!

The 2/3 to 1/3 rule isn't a hard and fast rule, it's just a guide and starting point. Compromise is normal.

Does that make sense?

Tim

I am going to be following your progress to see what you come up with on alignment settings.

I too have a 370z, but I am setting it up for Autocross instead of time attack, with the eventual hopes of doing some road racing. Hallet in Tulsa OK has some really awesome HDPE track days from what I understand, and we are all pretty excited for the new track being built as we speak in Missouri.

I ended up with RedShift Motorsports coilovers, complete GKTech suspension arms, GKTech speed sense delete fitting, EBC Yellows/2 piece rotors, Eibach sway bars, and going to be running Hoosier A7's on the factory Touring wheels. All this is going to bump me up to the top open class with the big boys (Local autocross does not go by SCCA classifications) and I was 4 seconds behind them at the finish of last season. Last year was my first year, ended up winning every event in my class. Some were really close at the start, I believe one was .012 margin. By the end of the season, I was 5-6 seconds faster than everyone.

Video of the fastest lap of the year. You can hear my disbelief at the end. I was super cold that day and track surface was super slippery.

https://youtu.be/5Vw41AkNgz8

I would be more than happy to help you with parts you need if any. I own a shop with access to a huge variety of parts. Unfortunately a lot has to come from either Z1 or ConceptZ.