Arse Freezes 2021 - Early Prep (Brake Upgrades)

To start, I do like the performance of the current brakes on the Z.  We are running the StopTech Sport Slotted Cryo Rotors and Hawk Performance DC-60 brake pads.  However, since this is an arms race, improvements are always the goal.  With that in mind, there are two items that I would like to improve the brakes.

The first upgrade is to get an increase in brake pad longevity.  Currently, when we run the car for the 7-8 hr we are going through about 60% of the Hawk DC-60 front brakes.  This means we replace pads after every major stint.  Looking around, I have been able to find and believe we can upgrade to a mixed version of 350z rotors and caliper setup "with a little bit of help with an A-daptor kit".  The router and pads are the same material, so this should increase pad and rotor size by ~15% and keep the desired performance.  Even as the car evolution continues, and we get faster, this increase in brake size should see brake wear get below the 45% per stint and allows for one set of brakes per weekend.

The front brake change will exacerbate the second issue.  The brakes are too sensitive and lacks the preferred fidelity.  The cause of this we believe is the bore size of the master cylinder.  We have examined the unit, and it is stated to be a 17/16", Torch measured it and the bore size is really only an 1".  This has proven to be a consistent problem as I have sourced Master other OEM cylinder from three other manufactures and all were found to be 1".  Thus, upgrading to the 350z brakes, we will then really have a hot mess.

Normally the solution is to increase bore size.  Since we are have such trouble with this, I am thinking of going to a Wilwood Master Cylinder setup.  They have 17/16" and 9/8" bore size options.  Now the question is just changing bore size be enough?

To answer that question, we need to look into braking pressure.  I don't know the peddle's ratio, so this will be all a guess from a 7:1 @ 100 lbs peddle pressure chart I found (shown below).  From this, my guess is that we want to drop 200-300 psi to give us some better feel.  Then, moving forward with the proposed 350z break system, if I assume a linear increase of brake size to pressure, a 15% increase in brake size could result in a relative increase brake pressure of 250-300psi.  Looking at those combined number, we are looking at a 450-600 psi brake pressure drop.  Bore size change is not going to cover that, so our attention turns to the brake boosters.

Looking at the brake booster, the 300z and the 350z diaphragms are similar in size, so no help.  This had me look, at the Nissan's 240SX single 9.55" booster.  The booster did have the same mount points as the Z, except the studs were about an 1" short.  No trouble. With some welding by Torch, we had some stud extension, and it fit right in.  So now, I estimate that we get a brake pressure reduction of about -225 psi.  This might be enough reduction to give us better brake sensitivity in our current setup.  We will find out in about 4 weeks.

Then, when we move to the 350Z brake system, I would propose changing the master cylinder from the current 1" to the Wilwood 9/8" bore.  The referenced chart indicate that we would get a brake pressure change of ~ -320 psi, and with hope matches the 350z brake increase.

How could any of this cause a problem? 

Arse Freezes 2021 - Early Prep (continues)

Work on the Z has continued, with some headway being made. We still have most of the major work still to finished before getting into the punchlist.  I am think in the next two weekends we should be able to complete these changes. Here is a review of the three major projects:

Front Bumper rework

The one area I have plugging away at for most of the fall is the front bumper area. It has been an ambitious project, and we will see if it is worth the endeavor. The general framing, ducts, and vents have been completed. Here is the front leftside view:

For a closer look of the vent system we have the side curtain vent (top), Brake duct (middle), and splitter diffuser (bottom):

I now need to add the crash absorbing elements, aluminum sheet flashing, and paint.

Brakes

Torch came over on Sunday and did a lot of work on the brake system. Repiping from the cut line was the main focus. With some scrounging the shop, enough 3/16 tubing was found. We are now one compression coupling away from closing the system. Also, the new brake boost was test fitted and found to not quite fit. Some extensions on the four mounting studs should correct the trouble. We should see the fruits of this labor this weekend, and I'll post another blog just on this brake up grade plans.

Fuel System

We have had a devil of a time with the fuel system since the installation of the VQ35. My earlier plan of connecting the two lobs with a line between the drain plugs is now scrapped. Finding the right check valve has proven elusive. I have thus gone full circle and now revisiting the initial OEM design setup.  In that design, Nissan used a Venturi Pump to aid in the transfer of fuel from one lob to the other.  Here is the general Venturi pump design:

The OEM Venturi pump failed when we increase the fuel pressure to support the VQ35 motor. At that time I looked, but could not find an adequate pump replacement. So, that led us down several other paths. This time, when I looked, I did find a company that produces a Venturi pump with a wider pressure range. A second factor is the name of the company, Radium. Now, how can I go wrong with this?

The second item we are fighting is the dynamic nature of the car. The OEM tank cause a lot of slushing of the fuel at low fuel levels. So, to control fuel movement, we thought of several plans. The one we liked to try is this swirl pot that Lugnut found:

The trouble we ran into is that literally that the pictured swirl pot would be fitting a square pot into a smaller round port. So, the search was on and what we found was a waste product out of the Hal-Life Racing HQ kitchen.

With some rummaging around the pantry, and some negotiation with Z-Chef, a Hunt's can of Crushed Tomatoes was procured (negotiation was made easier as the sell by date had elapsed.)  After emptying the contents (which turn into my dinner tonight), removing the label, and optimizing the form, I think we are in business. After some tinkering, we test fitted our new system.

Thus, we have a plan. So, this coming weekend, Torch is planning to return with his bore scope to aid us in the installation of our new fuel system. With a lot of hope, let's see if we can get the car to start again this weekend.