#MeToo-Endorsed Cooling Pump Inlet and Outlet

I didn’t want to use the cooling pump’s barbed inlet or outlet. Fortunately, the cap is removable and made of aluminum so I cut the barbs off. A Y-shaped outlet was made from a 1-1/4” and two 3/4” tubes. The junction of the Y was slot shaped and a mandrel mounted in a hydraulic press was used to bend it round so that it would match the larger tube.

Two -12 ORB weld bungs were shortened on a lathe and a shoulder was machined to keep everything concentric during welding. In the picture below, the top bung is stock and the two at the bottom have been modified.

The Y was welded directly to the pump’s cap to keep packaging compact and to reduce the number of connections that might leak. The cap was replaced and the pump was mounted to check the outlet and to mock the inlet. When we tried to remove the cap to weld the inlet we couldn’t get it off.

Do’h #^#%#$! I had it on and off at least five times, but no matter what we tried we couldn’t remove it. It was late and with removal attempts quickly escalating, I decided that for the cap’s safety we should resign our efforts for the day. Abe was able to remove it in the morning. We’re not sure what the issue was, so we put some grease on the o-ring and compressed the split ring a couple of times.

The inlet uses a 1-1/2” tube for the radiator return and a 1” tube for the heater return. The heater line uses a standard AN fitting and the remaining three lines use clamshell couplers.

All of the weld bungs are female because if the cap were dropped the threads on a male bung might get damaged and wreck the entire part. This allows damaged male threads to be tossed and easily replaced. This “disposable male genitalia” approach is endorsed by the #MeToo Movement. External plumbing does have disadvantages!

A lot of effort went into the cap. If I need to replace the pump, I can simply swap the caps — assuming I can remove it LOL.

Cooling Pump Bracket

The cooling pump bracket was made from 3/16” aluminum plate and 1/8” right-angle aluminum. Two of the pump’s mounting flanges are offset, so aluminum spacers were machined on a lathe. I had Abe weld them to the bracket because that reduces the number of things that I can lose by two;-) The bottom two holes are mounted through the 2” x 2” chassis tube with long M8 screws. The top screw is an M8 into a rivnut located in the top of the chassis tube.

As can be seen below the pump is slammed to the bottom of the car. This provides the inlet with the maximum amount of gravity feed from the radiator, keeps it’s center of gravity as low as possible and it allows the outlet to clear the cold air box.

The next step is to fabricate the inlet and outlet

Cooling Pump

I decided to use a remote electric water pump for the cooling system. I chose Pierburg, the same company that makes my intercooler pump. I initially purchased a CWA200 from Agile Automotive. They spec it on all of their SL-C and Aero builds and they’ve proven it at the 24-hour Thunderhill race and other endurance races. It allowed them to move the engine forward an inch or so and to relocate the pump’s weight to the nose box. Apparently the CWA200 has also been used by several GT2 teams. While the race credentials are nice to have, it’s been proven in many BMW and other OEM applications which is more applicable to my use case.

My engine builder expressed concerns about using an electric water pump. Seven or eight years ago he was retained by GM to test electric water pumps and he burned up a bunch of engines trying to find one that worked when a forced-induction, high-HP engine was pushed hard. Interestingly, the issue wasn’t flow rate. Rather the pumps didn’t create enough pressure to force steam pockets out of the rear of the block. This caused hot spots around the two rear cylinders (i.e., 7 and 8) which scorched their rings.

This need to have enough pressure to force steam pockets from the rear cylinders is why he advised me to leave the rear steam vent ports plugged. He strongly disagrees with the aftermarket steam vent kits that up-size the vent hose because they reduce pressure where you need it the most in an LS motor. Given that he’s been retained by GM for multiple R&D projects and he built the engines for the SL-C national champion after the team had a spate of blown engines from their prior marquee engine builder, it’s worth listening to him. That said, the tests were done a while ago.

To ensure that I would have enough pressure in the block, I upgraded the CWA200 to a CWA400 because its differential pressure rating is 1.9x higher (its flow is also ~40% higher). As can be seen in the comparison table, the CWA400 is marginally (i.e., ~1%) larger and while its max current rating is 2.2x it has an integral motor controller which is driven by a PWM signal. So, I gain ~2x increase in performance for a ~1% increase in size and a ~2x increase in power consumption (but only if I need it). In the end, the upgrade was a no-brainier.

In the pictures below, the CWA200 is on the left and the CWA400 is on the right. The primary physical difference is that the mounting tabs are on opposites sides of the outlet (i.e., they are 180 degrees apart).

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The cap on the CWA200 can be easily removed via four Torx screws, but it can’t be clocked. It took me a while to figure out how to remove the cap on the CWA400. It’s held in place by a split ring. To remove it, I used a large flat screwdriver to compress the ring between a bump on the body and a notch in the lid while twisting the screwdriver between the bump and the edge of the lid. It takes a couple of tries because an o-ring makes everything tight. When putting it back together you want to ensure that the split in the ring is 180 degrees (i.e., opposite) to the notch.

There’s a notch that’s machined in the edge of the lid which fits around the aforementioned bump. The sole purpose of the notch is to prevent the top from rotating and putting strain on the inlet and outlet hoses. The top can be easily clocked to any position by machining or filing a new notch.

Fortunately, the CWA400’s outlet orientation is perfect for my application and I didn’t need to make any modifications. The CWA200, whose cap can’t be clocked and is 180 degrees different, would have been a real pain in the ass to mount in my configuration. This was one of the other reasons why the upgrade made sense.

The next step is to mount the pump.

Pushrod Suspension

The rear suspension uses pushrods and bellcranks (aka rockers) rather than the conventional configuration in which the shock absorbers are mounted directly to the lower control arms. This is an exotic architecture found on Indy Cars, formula cars, prototypes and other pure race cars. While a few exotics have pushrod suspensions most production-based racers such as the Porsche GT3 Cup, a Spec Miata, or a Spec E30 have a conventional configuration.

Pushrod suspensions have the following advantages:

• Packaging: pretty much all open wheel race cars have pushrod suspensions because they allow aerodynamics to be optimized. Specifically, the shock can be placed inside the body (i.e., out of the air stream) and the width and height of the body can be drastically reduced because there is a high degree of freedom with respect to shock placement. If you look at the picture above, it’s clear why packaging is critical for open-wheeled cars.

• Unsprung weight is reduced because the shocks, springs and reservoirs are supported by the chassis rather than the lower control arm.

• Ride height can be adjusted by changing the length of the pushrod without changing the pre-load on the springs.

• Corner balancing can be done via adjustment of the pushrods.

• Body roll is reduced by relocating some weight towards the center of the car.

• Wheel rate can be easily changed by modifying the bellcrank’s motion-spring ratio (i.e., changing the length of one of the bellcrank’s arms). Wheel Rate = Spring Rate * (Motion Ratio ^ 2) * Spring Angle Correction. Since the notion-spring ratio is squared, small changes have a big impact. That said, the SL-C’s bellcrank has a 1:1 ratio.

The SL-C is basically a race car, so it’s not surprising that it has a pushrod rear suspension. The bellcrank is mounted via a large shoulder bolt which is retained by a billet aluminum bushing welded into a 1/8” x 2” x 2” chassis tube. The bushing takes high loads and the bellcrank is in single shear. It would be a nightmare if the bushing deformed because the only way to fix it would be to cut the entire tube out and replace everything. The chassis was welded in a jig at the factory and doing it properly on a finished car would be a challenge. Like some of the other builders, I decided to add a support arm to put the bellcrank in double shear.

Agile Automotive went through several iterations on their endurance SL-Cs and they offer 4130 chromoly parts for their latest iteration:

• 2x barrel welded to a cone (aka misalignment) washer

• 2x tube nut

• 2x bent and notched tube

There is a fair amount of variation from chassis to chassis and even from left-to-right on the same chassis, so they shipped me the parts with only the cone washer and barrel welded. The picture below shows the parts with the ones on the left having the tube’s mill scale and the barrel‘s weld discoloration re.

I’ve found that when loaded in a Dremel the AUSTOR abrasive wheels shown below do a great job preparing irregular metal surfaces (a tube polisher is obviously the best tool for round tube). The kit below costs less than $15 and contains 60 wheels in multiple grits (e.g., 120, 180, 320, and 400).

As intended, the tube needed to be trimmed and each side was on/off the car several times to get fitment right. I placed a grade-8 washer between the tube nut and the billet upright.

Once everything was installed the open barrel didn’t look finished and it would collect water and dirt which might make its way into the bellcrank’s bearing. I designed and 3D printed a cap. The first version had a mundane flat top so I gave it a profile similar to the dimple dies elsewhere.

I also plan on welding a gusset between the 2” x 2” tube and the vertical billet member.

Right Side Pod

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The lines in right side pod are finished. The approach is the same as the left side pod described here. There’s a lot less going on this side! The lines from top to bottom are:

• Air Jack (manifold to front jack, -6, aluminum)

• Heater Supply (engine outlet to heater, -10, aluminum)

• Heater Return (heater to pump inlet, -10, aluminum)

• Clutch (master cylinder to throwout bearing, 3/16”, stainless steel)

• Rear Brakes (residual pressure valve to brakes, 3/16”, stainless steel)

• Cooling Return (radiator to pump inlet, 1-1/2”, stainless steel)

The air jack line won’t be insulated because it doesn’t carry any heat.

While most of the clamps were 3D-printed, I used NotcHead Line Clamps in several locations. The hard line version requires a solid push on the line which results in a reassuring click.

Intercooler Pump Outlet

In a previous post I mounted the intercooler pump with a 3D-printed bracket. I thought about converting the barbed outlet to an AN fitting, but the cap is plastic and I couldn’t come up with a reliable solution. Mega-priced supercars use silicon hose and hose clamps so I guess that it would be OK to use them in this one place LOL.

The intercooler pump outlet’s OD is 20 mm and the stainless steel tube running to the front of the is -10 (i.e., 5/8” or 15.9 mm). To resolve the mismatch a barbed adapter was machined on a lathe from a solid stainless steel rod. This adapter will be welded to the stainless steel hard line once the line is ceramic coated and the insulation sleeve is slid on.

The angle between the pump outlet and the stainless steel tube that runs down the side pod is 112 degrees. After lots of research the closest elbow I could find was a 19 mm ID, 120-degree silicon elbow.

Induction Tube

The space between the body and the chassis is tight and the prior induction tube put a small crack in the fiberglass. It’s difficult to figure out how much space you have with the body in place. However, when the body is removed the tail section sits too low. To solve this, I cut two temporary tubes to support the tail at the correct height which makes it easy to check clearance when the body is off. The vertical sharpie line spanning the temporary support and the chassis makes it easy to align the support and the rubber on top protects the fiberglass.

I was concerned that I’d need to scallop the 2” x 2” chassis tube or use an oval induction tube, but a 45-degree bend was all that it took… well, that’s only the case because we previously positioned the throttle body in the right place and used a tight-90-degree elbow on the cold air box lid.

I used a -64 AN (i.e., 4”) AdelWiggens tube connector to connect the elbow to the induction tube. These clamshell-style connectors have been used in aerospace for over 30 years. They can be opened and closed with a single hand and require no tools. They have some impressive specs, all overkill for an induction tube, but that’s how I roll LOL

• Operating Pressure: 125 psig

• Proof Pressure: 250 psig

• Burst Pressure: 375 psig

• Axial Displacement: 0.250"

• Angular Misalignment: +/- 3.5 Degrees

I had to look up what psig was. It’s pounds per square inch gauge which is the pressure relative to atmospheric pressure as opposed to pounds per square inch absolute (psia) which is pressure relative to a vacuum. I guess if you manufacture parts that can be used terrestrially or in space you need to spec things that take atmospheric pressure or the absence of it into account.

The ferrules are typically butt welded, but I counterbored their IDs on a lathe to allow the them to fit over the tube. This ensured that they were perfectly concentric to the induction tube. Things were a bit sticky out-of the-box so I cleaned the grease off of the o-rings, ferrule grooves and sleeve and applied a thin layer of lithium grease.

Apparently the standard aerospace color for these types of clamps is purple, similar to the red/blue standard for AN fittings. I want to be 100% clear here. It’s purple and not any shade of pink!

The induction system is done other than the cold air box and the duct, neither of which are needed to start the engine.

Cold Air Box - Frame and Top

I started fabricating the cold air box. The top frame is made of 1/8” flat and right-angle aluminum and it’s bolted through the 2” x 2” chassis tube with three 1/4” screws. It’s designed to: (1) allow the body to be removed with it in place which is important during the build and go-kart phase and (2) allow the air box to be removed with the body in place which is important once the car is finished (the wheel and wheel well liner must be removed first).

Underside of frame with Dzus springs installed

My plan is to fabricate aluminum closeout panels to dress up the engine compartment. With that in mind the lid for the cold air box is larger than it needed to be to cover the 2” x 2” chassis rail and to close the gap between cold air box and the wheel well liner. I used four Dzus fasteners to fasten the top to the frame.

Here’s how I got everything to line up perfectly. The placement of springs under the frame was tight so I flipped the frame upside down on the bench, located the springs and drilled a 1/8” hole at the center point of each spring. I then installed the frame on the chassis and clamped the lid in three places. Using the hole in the frame as a guide, I drilled upwards through the lid with a 1/8” bit and inserted a cleco to further clamp the lid to the frame. I repeated this for the remaining three holes. Now that the center hole for the Dzus connector was located, the left and right holes for the rivets needed to be drilled. To accomplish this, I fabricated a simple drill jig — three 1/8” holes, 1/2” apart in a straight line on a piece of scrap. I affixed the center hole of the jig to each hole in the frame with a cleco. After rotating the jig to the desired orientation (i.e. what would fit) I drilled the left hole with an 1/8” bit, inserted a cleco into that hole and drilled the right hole with the same bit. At this point, I had three perfectly spaced 1/8” holes, 1/2” apart in a straight line. The center hole was then enlarged with a 5/8” carbide hole cutter which had a 1/8” pilot so it was easy to get that part right. 1/8” flush rivets were used to affix the springs.

Left, center and right holes for Dzus connector

I repeated the process for the lid with four exceptions; (1) I used 4-40 screws rather than rivets because I didn’t want to drill clearance holes in the frame for the back of the rivets. The screws worked because the lid was 1/8” thick to prevent warping when welding, (2) the left and right holes were were drilled with a #43 bit and tapped, (3) the center hole was chamfered to get the Dzus connector to sit flat and (4) since there were no clearance issues the orientation was determined by what looked best rather than what would fit.

So that’s a total of 36 drilling operations. Screws or nutserts would have been a lot easier, but the convenience of the quarter-turn fasteners was worth the effort.

A bellmouth-style velocity stack was welded to the underside of the lid to reduce air turbulence. It also significantly stiffened the lid which kept it from warping when the 90-degree elbow was welded to the topside. The filter mounts directly to the velocity stack with a stainless steel clamp.

Velocity stack welded, upper elbow not welded yet and Dzus fasteners not installed yet

With the lid fastened via the Dzus connectors, a tight 90-degree elbow was positioned and tacked into place. The seam between the velocity stack and the elbow was welded on the inside and it was carefully ported. I defy you to find the seam in the picture below;-)

Velocity stack and elbow are ported; note that the screws for the Dzus connectors are flush

While not necessary, I had Abe weld the seam between the elbow and top because I didn’t want dirt getting stuck in seam. The picture below shows the finished lid with the Dezus fasteners tightened.

I’m not going to fabricate the actual box or the duct the connects the body to the air box at this point because I don’t need it for the first engine start. With both the source (filter) and the destination (throttle body) in place, it’s time to fabricate the induction tube and connect the two.

Throttle Body Tube

In a previous post I designed weld flanges for the throttle body and supercharger snout and 3D printed them to check fitment. Since then I had them CNC machined from 6061 aluminum and they came out great. Due to minimum volumes I have a few extras so let let me know if you’re interested in a weld flange for ab LS7 or an LT5.

The prior version of the supercharger-to-throttle-body tube was in the passenger’s ear. The new version is much better. The passenger could put a pad on it and use it as a head rest LOL. The good news is that it fits behind the carbon fiber panel so it won’t be seen, but it sure as hell is going to be heard! The improvement was achieved by using tight-radius, mandrel-bent, made-in-the-USA tube from Performance Tube Bending.

One of the neat things that I learned from Abe is how to surface finish tube like a pro. Apparently there’s a specific tool for sanding and polishing tubes. It’s basically a belt sander with two fixed rollers and a third roller on a spring-loaded arm. When pressure is applied the belt conforms to the tube’s OD. Once I had removed the big grooves, scratches and dings, I found it useful to mark the remaining blemishes with a black sharpie. Similar to using a guide coat during body work, you sand the area until the black is gone. The video below shows a surface-prep belt (similar to a scotch pad) on a 4” aluminum tube. In this case the tool is clamped in a vice and the tube pushed into the belt. When I used the tool to remove the mill scale on the 1” OD chromoly, I switched things around and clamped the tube in the vice.

The tubes had some relatively deep grooves from the bending process. In addition there are some minor ripples on the inner radius of the bend. Even with the right tool it took me over an hour to get the surface to a perfect condition. Well, it actually took 45 minutes longer than that because when Abe went to tack weld the pieces on the car it didn’t fit…

WTF? D’oh! I accidentally used the cut end! Next time I’m going to use a sharpie to put some big “X’s” on the cut end.

Things would have gone faster if I had a belt with more aggressive grit for the first pass and a narrower belt when working on the inner radius. In any event, I’m happy with the results.

The next step is to fabricate the cold air box.

Intercooler Pump and Bracket 1.1

I previously posted about a bracket that I designed and 3D printed for the intercooler pump. It was a nice bracket, but when I went to install it I realized that there was a better location which required the pump to be as tight as possible to the bottom of the car and the chassis tube. So, into the bin went the bracket.

When designing the new bracket I held the pump in place and rotated it until I found the best angle for the outlet. I then removed the cap and clocked the body all four positions, each 90 degrees apart. Since the inlet is on the radial axis the electrical connector drove that choice.

One of the nice things about 3D printing is that it’s easy to incorporate features. For example, the picture below shows the back of bracket. The recesses around the mounting holes accommodate the flange on the NutSerts (i.e., gold piece with ridges) which allows the bracket to sit flush with the chassis.

In the picture below, the pump is mounted to the 2” x 2” chassis rail in front of the fuel surge tank. The top stainless steel hard line supplies the heat exchangers in nose and the bottom one returns the coolant to the intercoolers. The pump outlet is clocked two degrees too high so I’m going to tweak and reprint it. Once that’s done I’ll cut the lines, add beads and connect them with silicone hose.

Steering Rack 1.2

I finished installing the steering rack by using the stock top hole to clamp the rack in place while I located and drilled the bottom hole. The rack was removed, both of the stock holes were welded/closed, the top hole was drilled and 1/8” steel backer plates were fabricated.

Agile sent me taller pillow blocks which allowed me to ditch the spacer. Rack-to-steering-arm alignment looks good so I‘m not expecting any bump steer issues. Agile also sent me beefy tie rods with Auora heim joints which are higher quality than the ones provided in the kit. In addition, they have a misalignment mono ball which removes the need to use misalignment washers — two less things to lose!

I also noticed that the uprights were binding on the sway bar drop link brackets about 8 degrees before full lock. I had previously fabricated 1/4” spacers to allow the brackets to clear the top of the shock pins. This extra height was exacerbating the binding. It then occurred to me that I could clip the corner of the shock pin. This resolved the binding so I tossed the spacers. This also enables me to remove the shocks without removing the brackets. Duh, I wish I had done that sooner!

MORIMOTO MAKES MY DAY

Morimoto has released Aventador-inspired tail lights for the 2014-2019 C7 Corvette. They’re DOT-compliant and feature optional sequential turn signals. I’m not sure why they’re not listed on their website, but I purchased a set from Vette Lights.

In the image above, the right tail light is a 3D scan of an OEM C7 tail light and bezel with the “fang” removed. The tail light on the left is cut from a photo I took of the Morimoto light. While my graphics hack job is pretty bad, I think I like the Aventador style a lot more. I asked my daughter which she preferred and she responded “the one on the left because it looks meaner” — that’s my girl:-)

The one wrinkle is that they placed the backup light in the “fang” which I plan to cut off. I have two options:

1. Put the backup lights somewhere else.

2. Modify the fang so that it’s flush with the bottom of the tail light. That might provide enough space to retrofit some backup LEDs into the lower outer corner. Filling in that corner may also make the lights appear more fit for purpose.

Thanks to some help from Ken regarding the connector pin mappings, I was able to get them wired up on the bench. I’m sure there’s a way keep the lights from saturating the video, but it escapes me.

Oil Cooler Mounted

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I finally got the oil cooler mounted. The first step was to trim the wheel well liner so that I would know where to locate the oil cooler. The flange that goes against the body needed a lot trimming! Fitment was complicated by the air jacks and the liner was in an out of the car at least 20 times to get it right.

I bought a MHX-520 oil cooler and a MHX-520-FSS shroud with mounted SPAL fan from Improved Racing. The cooler has a high-quality, made-in-USA core and the shroud has four rubber grommet vibration isolators that are very similar to the ones that I used on the intercooler brackets.

I designed the upper and lower brackets to achieve the following:

• Allow the body to be removed / installed without touching anything

• Robust without adding too much weight

• Provide upper and lower mounting points for the rear tire liner

• Stiffen the bottom body flange in front the rear tire

• Cover the fan, the lower backside of the tire liner and the fiberglass body

• Provide mounting points for a panel that will eventually cover the upper backside of the tire liner

• Look cool — because that’s the way that I roll LOL

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I made the brackets out of 6” wide x 4” tall x 1/4” thick 90-degree aluminum (the structural stuff with a fillet on the inside corner). When the three-foot-long piece arrived in the mail I thought “that’s bigger and heavier than I thought!” After rough cutting it with a bandsaw, I used an end mill to clean up the edges. I then used a 3/4” end mill to cut six slots in the top and two in the vertical face. The slots on the top were milled parallel to the 2” x 2” chassis rail (62.5 degrees) to give it a custom appearance. This significantly lightened the piece and created a lot of chips!

Having enough of the fancy slots, the bottom bracket just got two big windows.

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Upper and lower brackets and support rod

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Cooler mounted

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Good fit to top of wheel well liner

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Good fit to bottom of wheel well liner

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1/8" backer plate on 2" x 2"

Each bracket has 1/4” screws that mount through the 2” x 2”, a 1/8” aluminum backer plate, a washer and a nyloc. The backer plates are held in place with a 10-24 button head. The vertical support rod was made from 5/8” stainless tube with M8 stainless flange nuts welded into the ends. The result is a very robust structure.

In the future, I’ll fabricate mounting tabs for the liner, a closeout panel to hide the upper portion of the wheel well liner and a bracket to stiffen the lower body flange in front of the rear tire.

Steering Rack 1.1

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As expected, I ran into some issues installing the new rack. Specifically, the housing OD is larger than and the section where the steering shaft connects protrudes lower than the stock rack. Compounding this, my chromoly tube frame prevents the rack from sliding upwards. To get it to fit, I had to scallop the top of the extended foot box and enlarge the opening in the vertical face of the monocoque. I’ll add a close out panel when the rack’s location is finalized. Most builders don’t have a nose frame, so I assume they won’t need to scallop the top of the extended foot box.

The pillow block holes were sized for M6 bolts and at Agile’s suggestion I enlarged the holes to M8 (future pillow blocks will be predrilled). I was hoping to reuse the stock rack’s top mounting holes in the monocoque, but that would result in a loose fit. So, all four holes will be welded shut and re-drilled. I don’t have the tie rods yet and I want to check bump steer before I finalize the mounting.

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To keep the bellows from rubbing the monocoque, 1/4” spacers are needed. I fabricated some temporary ones and I’ve asked Agile if the manufacturer can provide pillow blocks that are 1/4” taller. The factory ships the car with washers and nylocs on the backside of the pillow blocks. I added backing plates out of 1/8" steel.

Once the rack was in place I was able to determine where to locate and weld the crossbar on the top of the nose frame in front of the foot box. Due to ongoing changes, the Penske shock reservoirs have been kicked out of every location they’ve had and the crossbar provided an ideal place to mount them with some trick brackets from Joe’s Racing. Pull the pin and it pops open. Push the cam down, replace the pin and it’s locked. A simple design that works really well.

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Steering Rack

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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 that mount thenose 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

Intercooler Pump & Bracket

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.

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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 the 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. Once I get the pump mounted to the chassis I may need to tweak the location of the notch.

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Bump on the OD

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O-ring seals the top

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Note notch on ID

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3D printed bracket

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Bracket installed

Heat Exchangers Mounted

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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.

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

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Vibration Isolators

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Nissan grommets and bushings

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 well in the grommet’s groove. 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 bushing in 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.

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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 exchangers are installed. I should finish mounting them on Monday.

Left Side Pod

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One of the challenges building a mid-engine car is running all of the lines for the cooling, heating and intercooling systems from the heat-soaked engine compartment to the front of the car where there is copious cool air. The path runs alongside the cockpit so you must properly space and insulate the lines so as to not cook the driver.

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!

One of the brackets

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 space-tech and I’ll talk about it in a future post.

10 Pounds of Shit in a 5-Pound Bag

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 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, sacrificed a small animal and used a cut off wheel which worked great. I then lopped off the corner of the shroud and Abe welded it up. I now have plenty of clearance.

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Before (top plate already cut)

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After

This is the first time that I had the fans and the 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.