JohnCh

420R SV on BaT: https://bringatrailer.com/listing/2023-caterham-seven-420r/

Piling onto this comment, another place where people go wrong -- including Caterham -- is the sensor mounting orientation. Sensor manufacturers recommend positioning it at least 10 degrees above horizontal to minimize the condensation pooling on the tip.

I may be using TPU for a tricky airbox to air hose connection in another car. I'll be interested to hear how things go for you.

Very nice! For under bonnet items, check out PET-CF. Prints just as nicely as PETG-CF, but can handle very high heat.

He has a problematic Zetec that is getting horrid mileage. Someone with a 420 should be able to chime in with their typical street mpg. As proxies, my Westfield, with a taller (3.62 vs. 3.92) final drive returned ~25 mpg when it had 420 cams with ITBs, and about 1-2mpg worse after changing to more aggressive cams. Highway consumption when touring was much better. The 2.4L Duratec in my Caterham is pretty thirsty, barely breaking 20 mpg in normal (back roads/around town) street use. Something would need to be wrong for you to go through 5 gallons in just 40 miles of street use in a stock 420.

BTW all the suggestions above are assuming your car is running well and you aren't getting @Vovchandr-like fuel consumption.

Caterham doesn't offer smaller fuel tanks, so even if they somehow managed to install the slightly smaller S3 tank in your SV, you would still have 9.5 gallons less ~1.5 gallons the fuel pump can't reach. That doesn't mean the tank wasn't crushed, but you that would be pretty obvious from beneath the car. From the owner's manual: It seems there are only two possibilities: The way you checked earlier that the tank was full was done incorrectly, or you have an issue with the tank. Although it's a little tricky to do because of the flap and the curvature of the filler neck, you could make a curved dipstick out of thick single strand wire or thin rod to confirm the fuel level. I have done this before when troubleshooting, but it took several attempts to get an accurate reading. I found putting painter's tape on the rod was helpful to see the actual level. Another possibility is repeatedly tapping the front of the tank going from bottom to top to see if you note a change in the thud that delineates the transition from fuel to air. I've never tried this myself, so the difference may be too subtle to hear. If you do attempt it, avoid the middle of the tank where the baffle is located. If you think the tank should be nearly full and the dipstick or thump test shows about half, then you know the issue is with filling it. If not, then there could be a blockage, or possibly an issue with the baffle, which divides the fill side and pump side of the tank. The foolproof method to confirm the fuel level is to remove the floor and pull the fuel pump/sensor assembly and do a visual check. However, that isn't easy as an uncut floor can be very frustrating to remove, and you need a special tool to remove the fuel assembly's locking ring. Fortunately, that tool is readily available and isn't expensive. My boot floor is currently removed, so let me know if you need pictures of anything.

I'm not sure how @Croc will feel about losing top billing

Yep! The MAP sensor is really just there for barometric compensation. A TPS controls the tables. I can share my map that was done on a dyno for my 2.4L. I'll shoot you a PM.

@redursidae welcome to the world of se7ens where Alpha-N is the norm. Even the MBE in new Caterhams employs this older strategy with time-based injector control. It's certainly not as good as a VE-based PID control, but it's certainly possible to achieve good behavior with these less sophisticated ECUs. Over the last 22 years, I've run Emerald and MBE on Duratecs with ITBs and have never had running issues related to the mapping strategy. Your advice is spot on when it's time to replace the Pectel, but I suspect @Vovchandr's issues run far beyond his map or mapping strategy. Fuel milage doesn't plummet by 40% unless there is some kind of failure. He needs to address that first. I suppose it's possible that the Pectel has a driver failure that is intermittently holding open an injector, but other than that, I'd start by looking at all sensors that can trim the injection map, run a compression and leak down, then check injector flow to see if one or more is bad. If the AFR numbers provided above are accurate, I'd be very concerned about bore wash. Given all the issues with this particular engine over the years, I suspect there are multiple things going on. Occam's razor won't apply.

If your totals and fill procedure above are accurate, and assuming your car wasn't used to smuggle anything into the country via a hidden compartment in the fuel tank, I wonder if you experienced a fuel delivery issue, that is discrete from your gauge accuracy? Either some kind of blockage in the tank or the fuel pump cutting out? Has this only happened once?

I'm having trouble correlating your last two posts. Nearly 6 years ago, you wrote: Now you say: Did you make map changes in those intervening years, or does the Pectel have a self-mapping function that would have altered it without your intervention? If not, and if the supplied data is accurate, then something else has occurred to account for the significant drop in mpg; leaking injectors, fuel pressure has increased, TPS is out of adjustment, O2 sensor feeding the closed-loop mode has failed, compromised cylinder(s), etc. Changing the map to compensate for an unknown issue is just kicking the problem down the road. You need to identify the root cause(s).

The latest issue of Avants magazine has a nice article on Caterham that was pulled together with the help of some Seattle-area owners and features some very nice photography. https://www.avants.com/magazine/the-benchmark-for-lightness?

Per Caterham, S3 fuel tank capacity is 9.5 gallons (36 liters), and the SV is 10.8 gallons (41 liters). In both cases, the last 1.5-2 gallons isn't accessible due to the shape of the tank and the relation to the fuel pump pickup. It might be worth starting a separate thread on this if you need troubleshooting advice.

@Vovchandr is wrong. Now add that to your signature!