S2's Build Thread

[Scott]

In a previous post I cut a huge hole in the top of the monocoque / foot box to fit the Restmod Air evaporator. Although I have the optional removable side impact bars which add a lot of rigidity (they have welded steel plates that pick up the upper control arm mounts and the upper shock mount) I wanted to ensure that I wouldn’t have a structural problem.

The first step was to fill in part of the circular access hole with 1/4” plate. As can be seen in the photo below the edges were chamfered to get good penetration and a flat weld. Once that piece was welded, a 3/4” x 1-1/2” x 1/8” tube was welded to the top of the monocoque. The right corner is now rock solid.

 

[Ken Roberts]

What size are your brushless fans and where did you get them from Scott? It would be great to see your custom rad and fan packaging.

 

[Scott]

What size are your brushless fans and where did you get them from Scott? It would be great to see your custom rad and fan packaging.

Ken,

I spent of time a lot of time time working on the stock cooling system. I upgraded the fans, made a shroud and spent a lot of time designing 3D-printed brackets to mount the condenser. I was really impressed with my brackets until another builder pointed out that attaching the condenser to the floor wasn’t a great idea because the both it and radiator should be isolated from the chassis. D’oh!

I started doing some research which, in my case, can be dangerous. I decided to start from scratch with the following improvements:

• Complete vibration isolation
• Higher quality core
• Slightly larger core
• Move inlet from bottom of core to top
• Move outlet from top of core to bottom
• Move the bleed port from the high-pressure to the low-pressure side
• Air-tight shroud with proper spacing from radiator
• Highest quality fans available
• Integrated mounting tabs for the condenser
• Hard tube from bottom of radiator to inlet at the top
• No brass parts

Vibration Isolation
I spent of time a lot of time time working on the stock cooling system. I upgraded the fans, made a shroud and spent a lot of time designing 3D-printed brackets to mount the condenser. I was really impressed with my brackets until another builder pointed out that attaching the condenser to the floor wasn’t a great idea because the both it and radiator should be isolated from the chassis. D’oh!

I started doing some research which, in my case, can be dangerous. I decided to start from scratch with the following improvements:

• Complete vibration isolation
• Higher quality core
• Slightly larger core
• Move inlet from bottom of core to top
• Move outlet from top of core to bottom
• Move the bleed port from the high-pressure to the low-pressure side
• Air-tight shroud with proper spacing from radiator
• Highest quality fans available
• Integrated mounting tabs for the condenser
• Hard tube from bottom of radiator to inlet at the top
• No brass parts

I spent of time a lot of time time working on the stock cooling system. I upgraded the fans, made a shroud and spent a lot of time designing 3D-printed brackets to mount the condenser. I was really impressed with my brackets until another builder pointed out that attaching the condenser to the floor wasn’t a great idea because the both it and radiator should be isolated from the chassis. D’oh!

I started doing some research which, in my case, can be dangerous. I decided to start from scratch with the following improvements:

• Complete vibration isolation
• Higher quality core
• Slightly larger core
• Move inlet from bottom of core to top
• Move outlet from top of core to bottom
• Move the bleed port from the high-pressure to the low-pressure side
• Air-tight shroud with proper spacing from radiator
• Highest quality fans available
• Integrated mounting tabs for the condenser
• Hard tube from bottom of radiator to inlet at the top
• No brass parts

Vibration Isolation

Isolation dampers; stock/black ones on left, new/red ones on right

The stock radiator was well made, but it was jammed so tightly between the vertical supports that it was almost a stressed member and the provided grommets were laughable. My solution was to support the new radiator with two vibration-sandwich mounts per side. The picture compares the stock grommets (black) on the left and sandwich mounts on the right (red). Now, you’re probably thinking that the large mounts will reduce the size of the core. Well it just so happens that side tanks don’t need to be wide to be effective. In fact, they can be a lot narrower than the OD of the 1.5” inlet and outlet tubes. As can be seen in the picture the picture below, the side tank is narrow at the top to accommodate the mounts, but wider at the bottom to support the outlet tube. This approach results in a wider core than the stock radiator and reduces weight (the smaller tank uses less aluminum and stores less water). The downside to this approach is that it costs more to fabricate and it’s more difficult to prevent air from slipping around rather than through the radiator.

C&R RACING
Will and I visited C&R Racing’s booth at SEMA and we were impressed. They are the same guys that made the radiators for the Raver cars and for Howard and I found them to be professional and good to work with. After filling out a form to specify the requirements we went through several CAD iterations. They spec all dimensions and every part down to the washer. I’m ordering heat exchangers from them for air-to-water intercooler.

FANS
C&R recommended SPAL 11” brushless ABL315P drop-in fans. They are the highest performance fans that Spal provides, but there isn’t much information on them as they are only available from resellers who bundle them with a fan shroud (see spec sheet below). Bundling makes it difficult to figure out the actual cost of the fan, but it appears that they cost a little over $400 each. You’ll also need something to control the fans which in my case will be MoTeC.

SPAL ABL315P SPECS

The drop-in-style fans result in really nice packaging. I’ve wondered if they should have put a couple of flaps in the shroud, but I assume they know exactly what they’re doing. If not, I’ll send the shroud back to them to have flaps installed.

The stock radiator has a brass drain cock which promotes electrolysis in aluminum. I replaced it with a zinc-plated steel drain cock which will be connected to a drain tube drilled through the floor.

 

[Ken Roberts]

That's amazing Scott. Did you test fit the hood yet? I had to angle my shroud down to prevent hood height interference.

 

[Scott]

Did you test fit the hood yet?

Ken, when I replaced the nose box with the tube frame it changed things a bit. I've done a quick check and it's really close. I might need to tweak to the top of the shroud... wouldn't be the first time ;-)

Also, per your suggestion, I sent my throttle body to Solar Engineering to have it modified and ported. If anyone is interested in throttle body design and performance improvements the link that Ken previously posted is very interesting:

https://www.solerengineering.com/technical

They offer a quick turnaround and my tricked out throttle body arrived in the mail yesterday. The engraved plate must make things faster ;-)

 

[Scott]

This is another one of those two steps forward, one step backwards situations. Two and a half years ago I 3D-printed a mounting plate for a heater bypass control valve (picture above, post here). I spent a fair amount of time on it and it’s a slick piece, but I’m not going to use it. I’m going to create a mini museum in the garage with three displays:

• Shelf of Lost Fame — Great parts that I designed, but I didn’t use because I changed direction
• Wall of Shame — Parts that I mangled… there are some doozies
• Drawer of Lame — Purchased parts that I can’t return which don’t fit, don’t work or aren’t compatible with the new direction

I decided to not use the heater valve plate for two reasons. First I’d have to remove the spider to service the valve… no way would I want to do that once the car is painted, the windshield is installed and everything is sealed up. Secondly, now that I am replacing the mechanical water pump with an electric one I don’t need the heater bypass valve which means that hot water won’t be constantly flowing through the valve. Since I don’t have to worry about heat soaking the cockpit when the heat isn’t on, it makes sense to move the valve from the rear of the car to under the dash. It will be easy to service in that location, it’s more protected than the engine compartment and I don’t need to run control wires to the rear of the car.

The straight-through heater valve is easier to mount than the bypass version. The four posts can be tapped for 6-32 screws. I fabricated an aluminum plate, 3D printed a spacer and mounted it to the aluminum tube that was recently welded to the top of the foot box. The lightening holes in the bracket don’t save much weight… I just like using Hougen hole cutters because they cut metal like butter.;-)

I bought several heater hoses looking for one that was flexible enough to make the required bends without kinking and I found the nylon reinforced silicone hose offered by Vibrant Performance to be good to work with.

 

[Scott]

When the chassis was empty I thought “wow, there’s lots of room for everything including all of the cool shit I want to add to the car.” After dropping in the engine, the Ricardo transaxle (a beast) and a few of the other big items things quickly got claustrophobic.



Building the car presents the proverbial ten pounds of shit in a five-pound bag problem as demonstrated in this Myth Busters episode. My most recent 10-into-5 challenge, as Ken pointed out, was that my upsized custom radiator/shroud was hitting the nose… not good.

I fixed it by tilting the radiator forward a few more degrees and modifying the corners of the assembly. The shroud is bolted to aluminum plates that are welded to the top and bottom of the radiator. This provides a strong, airtight interface with a clean appearance. However, it meant that I needed to cut the top plate which is welded to an expensive radiator. I clamped a steel bar across the cut line, scarified a small animal and used a cut off wheel. It worked well. I then lopped off the corner of the shroud and Abe welded it up. I now have plenty of clearance.

Before

After

This is the first time that I had the fans and shroud off and I continue to be impressed with C&R. For example, they flat rivet the same type of use self-locking, floating nut plates that I used in a previous post. This makes assembly/disassembly very easy and it ensures that the screws don’t back out.

The next step is to deal with the condenser… the bottom mounting flange is rubbing on the floor.

 

[Scott]

I finally finished the lines in the left side pod. The first step was to weld the 1-1/2” cooling lines that run between the engine and radiator. To mount them, I used the same billet clamps that Stephen used expect that they no longer sell them with the rubber installed — 1/8” self-adhesive rubber from McMaster solved that. To get the tubes low enough to clear the control arms, the clamps had to be machined to accommodate the weld bead and floor plate. The lower mounting holes on the backside were also moved up to clear the weld bead. P-clips would have been a lot less work!

Once the body is painted, the windshield is installed and everything is sealed tight, I never want to take the body off. The only way to achieve that is to ensure that nothing in the side pods will need to be serviced. That’s why I tossed the super-trick heater control valve plate I designed and I had Abe weld shut all of the bulkhead holes that I had drilled in the monocoque. So, how do you plumb everything with no connections and no bulkheads? Continuous hard lines, of course.

All of the lines that are exposed in the wheel wells are stainless steel and the ones that run inside the body are aluminum. Since it’s impossible to get coiled tube perfectly straight, that 5/8” stainless doesn’t come coiled and that some of the tube lengths were over 8’ long, I ordered 20’ straight pieces which had to be delivered via freight. That said, the coiled stuff is less expensive and is perfect for making templates. For example, the bends over the top of foot box are tricky to get to clear the body and if you mess up that last bend the entire piece is junk. I added three tube benders to my tool collection o handle the different tube diameters. Vintage Air sells stainless A/C weld fittings which were welded to the tubes after their IDs were machined on a lathe to fit.

To hold everything in place I designed seven different brackets and printed 3D-printed 14. The orange sleeves are pieces of insulation which are being used to properly locate the tubes in the brackets.

The tubes from top to bottom:

• A/C Suction (evaporator to compressor, -10, aluminum)
• Radiator Bleed (radiator to expansion tank, -4, stainless steel)
• A/C Discharge (compressor to condenser, -8, stainless steel)
• Intercooler (pump to heat exchangers, -10, stainless steel)
• Intercooler (heat exchangers to intercooler, -10; stainless steel)
• Cooling (engine to radiator, 1-1/2”, stainless steel)

Engine compartment ends not welded yet

The front of the foot box is crowded, but everything is serviceable. The Y-blocks are to plumb the intercooler’s heat exchangers in parallel.

The next step is to have the tubes coated in Cerakote to reduce heat transfer, slide full length insulation on and weld the ends on in the engine compartment. The 1-1/2” cooling lines get two five mm wraps of aerogel blanket. Aerogel is cool tech and l'll talk about it in a future post.

 

[Roger Reid]

Absolutely beautiful Scott. Love that sway bar.

 

[Joel K]

Very nice work Scott. All the tubing looks well organized.

 

[Joel K]

Scott, also looking forward to seeing your Intercooler setup.

 

[DaveC]

I see you switched to a simple coolant cutoff switch for your heater core.
We GTM guys are familiar with a unique overheating situation with LS engines that can occur if you sit at idle for a while after startup. This occurs when the heater core coolant path is blocked by a valve like yours. Blocking this path prevents normal thermostat operation. So we do install valves to stop flow to the heater core in the summer, but that flow has to be rerouted back to the thermostat (usually through a header tank or expansion tank).

 

[Scott]

Dave, thanks for the heads up. I switched from the heater bypass valve to the basic valve because I switched from a mechanical pump to a remote electric one. So, I don't have to worry about that issue... I just need to figure out the best way to plumb the cooling system (i.e., use a thermostat or not, etc.)

 

[Scott]

C&R Racing delivered my custom heat exchangers this week. Before mounting them I needed to figure out how to isolate them from vibration. I had planned on using sandwich mounts similar to what I used for the radiator, but I wasn’t able to come up with a good way employ them. I then spent a lot of time looking for a rubber grommet with a metal bushing like what I’ve seen on lots of OEM applications. The only aftermarket ones that I could find where intended to isolate oil and gas tanks on choppers. However, they’re designed to be installed in 1/4” thick steel brackets… I guess choppers shake a lot.

Striking out with aftermarket vendors, I decided to look for an OEM part. Abe had a Nissan GT-R in his shop and we found a some nice grommets on its oil cooler. He checked the service manual, and ordered some Nissan parts:

• Grommet: 18316-S3260 (Nissan calls it a “Clip-Rubber”)
• Bushing: 49728-55S0A (Nissan calls it a “Collar-Insulator”)

I used 0.10” aluminum for the bracket which fits in the grommet’s groove well. The groove’s OD is about 11/16” so I used a 5/8” hole saw and then a step drill bit to open up the hole a little. Note that you can’t install the grommet with the sleeve it — duh, it took me a little longer than it should of to figure that out.The picture below is a test bracket made of 0.10 aluminum and isolated from a weld tab with a grommet and bushing.

The bushing’s ID will accommodate an M6 or a 1/4” screw. However, I had some 3/16'“ steel weld tabs with 1/4” through holes that I wanted to use as nut plates. I was able to open the bushing ID with a drill bit to fit a 5/16” bolt which allowed me to drill and tap the existing holes in the tabs.

You can increase the stiffness of the grommet by machining or grinding the small end of the bushing which increases the “squish". It appears that the stock squish is good, but I won’t know for sure until the heat exchanger is installed. I should finish mounting them on Monday.

 

[Scott]

I finished mounting the heat exchangers today. The first step was to weld a support tube and three mounting tabs to each side of the nose structure. The tubes lean back at the same 62-degree angle as the heat exchangers and the tabs use used to mount the rubber isolation grommets described in the previous post..

The top bracket is a simple 0.10” aluminum tab welded to the heat exchanger. It has a single grommet.

The bottom bracket is more complicated. It uses a 1/8” u-channel lined with 1/16” self-adhesive, high-temperature silicon to cradle the bottom of the heat exchanger and to prevent it from twisting. The u-channel is welded to a vertical plate with two grommets and a gusset is welded between two. I couldn’t resist using my dimple dies.

The heat exchangers are well isolated and the splitter. nose floor and nose sides can be easy removed with them installed.

 

[Joel K]

Looking good Scott, well done!

 

[Del]

Scott, you're level to detail is outstanding....and that's an understatement!

When I first read about the isolating, I was thinking the same thing and use the bushings for a motorcycle gas tank. My Hayabusa used identical (looking) ones you had pictured.

 

[Scott]

Thanks for the compliments guys. All of the research is finally starting to pay off.

I decided to use a Pierburg CWA100-3 for the intercooler. Pierburg is the same manufacturer that I plan on using for the main cooling system. They were the world's first series-production supplier of an electric coolant pump so they've been doing it longer than anyone. The pumps are manufactured in Germany and are OEM equipment for BMW and others. They have a brushless motor and an integrated variable speed controller which can be controlled via a PWM signal. I’m not sure what other pumps spin at, but I was surprised to see this one is rated at 7,000 RPM. As can be seen in the graph below 30-35 l/min @ 0.75 bar.

Like many electric fluid pumps the inlet and outlet are 90-degrees apart. It makes sense to vertically orient the pump so that inlet is gravity fed by the reservoir and the outlet points towards the tube in the side pod. The top is clock-able in one of four directions once the four T20 Torx screws are removed. As can be seen in the picture below the top is sealed with an O-ring. I clocked the top so that electrical connector was oriented towards the chassis.

The pump has a rubber sleeve for vibration isolation. The sleeve has a full-height ~0.06” x 0.73” bump on the OD so the mounting bracket requires a notch. I’m sure that there are OEM brackets out there, but a 3D-printed bracket makes sense in this situation; I’m no where near a heat source, it will be lighter than an aluminum one and I can place the notch exactly where I want it to orient the pump.

Note the bump on the OD

O-ring seals the top

I might need to relocate the notch on ID

3D printed bracket

Bracket installed

 

[Scott]

SL-C racks on the left and Aero racks on the right

The stock steering rack has a slow ratio which is evident even when pushing the car around the garage. Lock-to-lock steering requires 2.6 turns and even then the SL-C seems to have wider turning radius than most cars. I assume that the slow ratio was chosen because SLC’s have big, sticky tires and very few have power steering — there’s typically no room in the engine compartment for a power steering pump and electric assist systems aren’t cheap. Without power steering a quicker ratio would require Popeye arms to park the car.

Based on their experience with endurance racing SL-C’s, Agile Automotive has developed a steering rack for the SL-C and the Aero which they are installing on all of the Superlite cars they build/maintain. The race rack is 42% faster, the street rack is 25% faster and they can provide custom ratios as well. While the stock rack is robust enough for the street, Agile doesn’t think it’s a good fit for a car running slicks so they significantly beefed up their version.

Key benefits include:

• Faster steering ratio
• Manufactured in Europe by a motorsports manufacturer
• CNC-machined cast aluminum housing
• Considerably more robust pinion and rack shaft (tested and validated in professional motorsports)
• Designed to withstand the stresses of column-driven electric-power-assisted steering
• Larger, stronger inner tie rod ends for increased load capacity and longevity

I just received my rack today and it’s in keeping with the rest of the car — well engineered and lots of CNC-machined aluminum. The diameter of the housing is larger than the stock rack which minimally means that I’ll need to drill a couple of new mounting holes in the monocoque. I’m pretty sure that the rack’s mounting blocks will collide with the welded steel plates use to mount my nose structure, but that’s the way these things go. You change one thing and it has a ripple effect… in this case one ripple colliding with another ripple… LOL

 

[Mesa]

Damn you Scott!
How much is the rack?
The power steering?