520R SV build has commenced

[slowdude]

17 hours ago, JohnCh said:

I'm running Racetech mechanical gauges on the Westfield for water temp, oil temp, and oil pressure and like them, but opted for an AiM display on the Caterham.  I'd prefer to keep that minimalist dash aesthetic and not add any standalone gauges.  The good news is the pigtail was the issue.  A multimeter confirmed the 12v+ wire had a problem, showing fluctuating positive resistance vs 0.00 ohms for the other two wires.  It's most likely a failed crimp at the plug end.  

A multimeter has been my best friend with this car. 

[JohnCh]

1 hour ago, slowdude said:

A multimeter has been my best friend with this car. 

 

It's been Guinness and creative swearing for me.  Although typically not in that order.

[JohnCh]

I've had a chance to confirm the effectiveness of the small LEDs in the lower grill used as DRLs. They work well when viewed head-on from a distance but are a lot less effective off axis.  Given my primary use case is for oncoming traffic on long straights of undivided roads, they meet my objective, but I can see the need to supplement them with the headlights in some situations.  So not perfect, but reasonably close, and unlike the headlights, there is no need to remember to turn them on and off.

 

 

-John

[JohnCh]

The intercooler scoop on the top of the 620 nosecone is covered by a metal grill glued to the underside of the fiberglass.  Unfortunately, production tolerances being what they are, the front of the grill section on my car touches the top of the radiator in two places.  It's not enough to notice when installing the nosecone and not so much that a piece of paper can't be pushed between them.  However, as I discovered a couple of weeks ago, it's enough that when things are moving around while under way, the grill was wearing away the radiator.  Not good. 

 

 

 

A thread on BlatChat this week from someone having an even bigger interference issue with the same 620 nosecone/SV chassis combination spurred me to address this before taking the car out this weekend.  The fix was simple: drill new mounting holes on the radiator brackets 10mm lower than stock.  These new locations are highlighted in red in this old photo of the brackets.   

 

 

Given I'm a measure thrice, cut twice kind of guy simply because I invariably measure incorrectly the first two times, I opted to print up a quick jig to perfectly locate the new holes.  It inserts into the original bolt holes via extrusions and has two much smaller holes sized to accept a center punch that dimples the exact starting points for the drill bit.  This is one of these areas where 3D printing comes in really handy.  It only took a few minutes to get the measurements, draw it in CAD, then send to the printer.  I've said it before and I'll say it again, if you haven't explored the world of 3D printing yet, you should. 

 

 

The lower mounting position required slight rotation of an oil cooler hose to maintain clearance with a chassis tube, but no other issues...yet.  I'll test the car over the next few days to make sure I didn't introduce another problem.  

 

 

[JohnCh]

A few updates.

 

Now that the low-level fuel feed issues have been resolved with a proper positive displacement pump, I swapped out V2 of the in-tank fuel assembly setup for my original version.  Those keeping track at home may recall there were initial concerns that those fuel feed issues were due to additional plumbing restrictions in V1 which used a remotely mounted Hydramat attached to the tank floor.  In contrast, V2 used a smaller Hydramat attached directly to the bottom of the pump but that placed it slightly above the tank floor.  Unfortunately, I don't have good photos of either setup but these will give an idea of the difference.  The top photo is the outgoing V2 with the positive displacement pump alongside, and the bottom photo is V1 but without the fuel sensor installed (the long silver tube in the V2 picture).  

 

 

 

While doing that job, I decided to map the Centroid fuel level sensor's output by slowly adding fuel to the nearly empty tank and taking voltage measurements after every gallon.  I could then update the 0-5V sensor map used by the AiM to ensure accuracy throughout the range.  What I didn't realize at the time is the sensor has a built-in empty to full detection capability triggered when certain conditions are met.  I appear to have unintentionally met those conditions, creating all kinds of accuracy issues such as reading full with less than 3 gallons in the tank.  After redoing it a couple of times with troubleshooting assistance from Centroid – whose support was excellent – things seem to be sorted but they did advise to watch for future anomalies as there remains the possibility the sensor has a random issue.  During the mapping, I was also able to confirm the SV tank really does hold 41 liters.  With the Hydramat, I should be able to access nearly all of it, rather than just ~35 liters as with the factory setup.  

 

This weekend I had my first opportunity to drive the car in hot weather.  I'm happy to report the factory heat insulation works just fine.  After one hour of driving in 90F weather with a very strong sun, temps were similar to the Westfield which has never had an issue in this regard.  

 

The unused fastener holes for the 3-point seat belts have been bugging me; they look unnecessarily unfinished.  To rectify, I printed some plugs (don't worry, they add under 1.9 grams each) and popped them in place.  

 

 

 

-John

[CBuff]

I like your fueling solutions. Something about not being able to use the last couple of gallons bugs me more than it should. Love the hydramat. Maybe a long term project so that I can use the fuel that's in the tank. Thanks for the inspiration. 

 

Your 3d printing and obsession with finishes is appreciated here. 

[JohnCh]

I drove the Caterham Saturday and the Westfield Sunday.  That second drive confirmed the MOG seats are definitely more comfortable for me, but I also noticed they are slightly more reclined, which is a contributing factor.  I experimented a bit today with rake on the Caterham's seat and ended up increasing it another 10mm; the equivalent of one Tillet spacer.  Rather than use those spacers or washers, which only have partial contact with the seat base given the base isn't parallel to the runners when tilted, I decided to print spacers designed to fit.  Certainly not necessary, but it soothed my OCD.  

 

A proper test will need to wait until this weekend, but based on a short trial in the garage, comfort seems a bit better.

 

 

[wdb]

OCD FTW!

[JohnCh]

6 minutes ago, wdb said:

OCD FTW!

 

Hmm...  Perhaps I should rename this thread to something along those lines?  It would be more reflective of the content.   

[JohnCh]

I finally got around to addressing a couple of issues lingering from the build that required scuttle removal. First was installing the remote button interface for the AiM which includes a shortcut to reset the trip odometer with a single push of a dedicated momentary switch. Without this, resetting involves no fewer than four buttons on the sides of the AiM and a total of eight button pushes: six to reset the odometer, and two to return to the gauges screen. My stops for fuel will now be seven button pushes quicker.

 

 

The other issue was heated seats that have never worked. Each seat has a dedicated relay controlled by an On-Off-On switch. A master relay controlled by the ECU, then feeds power to both seat relays but only while the engine is running. Caterham told me they do this to prevent someone unintentionally draining the battery while parked. Their instructions were to assign Pin 25 to Shift Light 2, then have it switch on (connect to ground) when the engine is over 800rpm and off when revs fall below 750rpm. Simple. SBD opted to configure this slightly differently on my custom map, assigning Pin 25 to Shift Light (not SL2) and setting the on/off rpm to 800/500. 

 

When troubleshooting, my initial assumption was that something in the wiring was wonky. However, there is continuity from Pin 25 to the coil on the master relay and shorting that wire to ground triggers the relay and allows the seats to work. Hmm...  Checking the map showed that Pin 25 was assigned to Shift Light and Shift Light set to go on/off at the revised rpm points. I didn't see anything else to tweak, but did contact SBD and sent them screenshots of the relevant screens to ask.  

 

 

With the holidays, however, I don't expect to hear back soon and opted to go a different direction. Given I can't imagine a scenario where I will sit in the car with the key at position 2, the engine off, and the seats on, I decided to simplify and bypass the master relay with a jumper wire. The photo below shows the backs of the three relay sockets bolted to the fire wall, with the master relay in the middle. The jumper connects pins 30 and 87. Now the seats work perfectly. 

 

 

 

[wdb]

Ooooh, 'lectrics. You must be a mage!

[JohnCh]

2 hours ago, wdb said:

Ooooh, 'lectrics. You must be a mage!

 

I think the "m" word you were looking for is masochist  

[JohnCh]

The weather here since the Holidays has been either atrocious, or those rare dry days have occurred when I'm unable to take out the cars.  As a result, yesterday was the first time I've driven the Caterham since connecting up the short-cut button to zero out the trip odometer in the AiM.  I did a 25-mile loop, then went to fuel the car, and the button no longer works.     I'm assuming vibration caused a connection to no longer connect, but I'll need to remove the scuttle to confirm and to fix it, so it will be a while.  

 

This was also my first opportunity to try the heated seats.  I didn't order these as a means to keep me warm, but rather to help with a bad back, which does respond a bit to heat.  Sadly, the Caterham seat heaters appear to be designed by the same Lucas engineer who did the wiper mechanism.  Yes, they work, but not particularly well.  I'd say the seat heaters on high feel equivalent to a modern car's seats on their lowest setting.  Better than nothing, but not quite what I need.  Oh well...

 

With rain returning tomorrow, I took the car out again today, doing my favorite 40-mile loop up High Bridge Rd.  Traffic was fairly light on the out leg, but virtually traffic free on the return.  The engine continues to amaze.  I've driven 265hp and 280hp Caterham's in the past, but the lower powered car didn't make me involuntarily swear when accelerating hard like this car.  Here is a photo taken along the way.

 

 

 

[pethier]

On 6/6/2024 at 12:28 PM, JohnCh said:

I've said it before and I'll say it again, if you haven't explored the world of 3D printing yet, you should. 

I am lucky to have a computer-professional son-in-law who dabbles in 3D printing.  He printed an ABS spacer for my steering-wheel release mechanism.

 

 

[Austin David]

@JohnCh -- I think I starved my "stock" in-tank pickup last weekend with a relatively calm left turn, 209 miles on the tank.  After it stalled I let it sit a sec, it fired back up and no further issues; I was already on the way to the fuel station.  For the record it took 7.463 up to top of the neck.

 

I went back over your build and I think I understand your final in-tank setup, but I'd like to confirm:

- positive displacement pump

- hydramat, offset, directly on the bottom of the pump

- pump hanging from a custom 3d-printed lid, ported for the two lines + a few passthroughs for the pump + gauge lines

 

And I saw a note that the hydramat slightly above the tank floor

 

Questions:

1) why not position the pump and mat directly on the tank floor?  is it just an issue of getting the hanger exactly right, or was there another problem?

2) did the mat fit under the baffle, or did you need something small enough to fit on the left-hand side of the tank, before the baffle?

3) what material did you use to print the lid, and can you share the STL?  Given the clearance under the boot floor I'm pretty sure I'd like to angle and offset the fuel lines, but I'd love to see what you ended up with.

4) I assume it is still working well after a few years (and hopefully many miles) of use

[JohnCh]

@Austin David 

Initial speculation was that the two 90 deg fittings between the pump and Hydramat were too restrictive and causing the issue. That drove the V2 design with a smaller matt attached to the bottom of the pump. Once the true cause was discovered and the pump was replaced with a positive displacement unit, I reverted back to V1 which is shown below. The fuel level sensor is missing in the first two photos but fills the hole in the top. I have over 3000 miles on the car, and other than those initial foibles stemming from the use of a standard pump, there have been no issues.

 

 

 

 

Although I can send you the STL, unless you are doing this exactly the same, including changing to a return style system with AN -6 hoses and using that same sensor, it won't work. The design is really simple. Just mirror the dimensions of the stock lid. The fiddly aspect is placing the holes for the inlet and outlet hose ends, the fuel level sensor, fuel pump terminals, and the mounting holes for the pump bracket. Space is a little tight and you need to ensure that placement of the various parts doesn't interfere with mounting/unmounting.

 

The Hydramat fits between the baffle and the pump. The opening in the baffle you referenced — at least on my car — is placed on the tank floor, but a few inches up from the front of the tank, meaning if placed there it won't get to all the fuel thanks to the steeply sloped floor. By reverting to my V1 design, the Hydramat is located on the floor where it meets that bulkhead and can access all the fuel on that side of the baffle. It may miss a liter or two in some situations, but that's a far cry from the factory design which appears to miss about six liters.

 

If you are going to this trouble, I suggest adding a fuel filter. Although I've never heard about problems arising from Caterham's decision to not use one, it doesn't seem right to me. These photos show the filter mount I made and the location under the aluminum channel that supports the boot floor.

 

 

 

 

I standardized on PA-CF filament for nearly everything on the car, although I experimented with PETG-CF for the fuel cover with success and printed my back up out of that material (I left a piece in a fuel filled jar for a couple of years with no softening.) You don't need the extra heat resistance offered by PA-CF in that area, and PETG has no issue with fuel, and is also easier to print.

 

-John

[Austin David]

I already ran the fuel pump, and more or less followed your lead with the filter.  Literally the cheapest part of this project, an inline filter costs about as much as a single AN-6 fitting.  I just "need" to re-hang the pump (or maybe a new one) to get access to the last ~ 8L in the tank. 

 

I've had more success with PETG-CF and fuel over time, PA creep kinda weirds me out in an important application.  I see there's also options for epoxy coating if it ever gets weird.

 

Thanks for the added photos, those answer my questions!

[JohnCh]

I haven't had a creep issue on any of the parts -- supposedly the CF addition helps -- but if I do, I'll reprint in PET-CF. I'll send you a PM re: files.

[CBuff]

I am very jealous. I just keep carrying that 1 plus gallon of fuel around without anyway to use it.  
pinning this for an upgrade down the line.