KnifeySpoony

Your car already has the 8%. The 8% rack has been standard for some time. I have no experience with the 22%, but even in hairpins I don't have to shuffle with the 8% rack so I've no desire to upgrade. Also effort is already pretty high when under load.

I tried unplugging the new sensor and the car runs exactly the same. So clearly my new 02 sensor is not doing anything. So it seems to me that either it's 1: sensor is DOA, 2: it's incompatible (it's a Bosch sensor that used to be included with r400/420R not the no-name sensor my kit came with), 3: the wiring from the sensor to the ECU has gone bad, or 4: the ECU has gone bad. Seems like sensor logging wouldn't be that valuable at this point. I suppose I should check wiring continuity; how to do this? Multimeter at sensor plug and at ECU plug? What pins go where? I could also put the OEM sensor back in and see if the behavior reverts or stays the same.

Not to soapbox you, but imo rotor and pad inspection should be done before every trackday, and sometimes even multiple times during a trackday, depending on the car and condition of said consumables in the morning. Glad you caught this before something bad happened.

Well.. It's kinda solved but now there's a new symptom. Now the 5-20% throttle range is smooth, but from 0-3%, ie initial tip-in there is hesitation/sputtering/misfire. And it does it immediately after starting even when cold. Car starts instantly and idles fine. Giving it verrry slight throttle will cause it to sputter/miss. More throttle and it revs fine. Interesting the drastic change in behavior with the new 02 sensor but not sure how to interpret. I'm thinking the 02 sensor isn't even active when the car is freshly started so I don't understand why the new sensor would cause this behavior. I'm going to triple check the TPS voltage, roller idle spacing, sparkplugs, etc.

New lambda sensor and problem seems to be solved. I had the no name sensor that others have mentioned recently. Replaced with proper Bosch part.

I put in a Spa designs dual temp gauge. Love it.

Can you describe the issue with each gauge in more detail? As others have said, the fixes may be easy. My 420 tach read low when i built it. The dipswitches were set wrong. Even caterham denies the existence of the switches however...

Given the concern that all Avons will be unavailable soon, I assume many of us will be making this change. To anyone that has actually done it- Did you notice any change in balance going to the narrower rear tire? Where does the Toyo grip fall relative to the ZZS and ZZR? And did you make any ride height /geo changes to compensate for taller sidewalls?

Given the concern that all Avons will be unavailable soon, I assume many of us will be making this change. To anyone that has actually done it- Did you notice any change in balance going to the narrower rear tire? Where does the Toyo grip fall relative to the ZZS and ZZR? And did you make any ride height /geo changes to compensate for taller sidewalls?

Define "performance"

Yes mine moves too. Have you seen how much the dedion deflects laterally under load? Maybe it's by design. Although not many things in our cars are...

I know you're done with it, but another way is to use a screwdriver to leverage it over the corner. Worked well for me on my build.

Thank you all for the input- you've given me a lot to look into. Interesting about possible vapor lock - I didn't think that was a thing with fuel injected engines. The roller barrels, having a lot of thermal mass and being right under the injectors and fuel rail, seems to make sense as a possible heat source to boil fuel. Here in California, all we have is E10.

I should clarify that my symptom does not go away after one episode- it is persistent once it starts acting up.

My 420R on roller barrel throttle bodies has developed an issue. When the car is hot, ie only after driving for 20-30min, well after the engine is up to temp, I'm getting hesitation at partial throttle - basically from 0-5% throttle, tip in feels normal, however it's like from 5-20% throttle, no fuel is being added, and the car hesitates severely/will not accelerate at all. If I keep gradually opening the throttle, once its gets past about 20% or so, then it's like it catches, I get a surge, then the rest of the throttle travel is normal. Car pulls hard and smooth to redline at larger throttle openings. When I get the hesitation, it's interesting in that if I keep the throttle depressed at that position, and press in the clutch, the revs do not climb at all as they normally would when the load is removed- this initially led me to believe it was a TPS issue. No popping from exhaust. No smoke that I can tell. I checked the TPS with easimap - idle voltage is correct, and it seems to be sweeping/responding normal with throttle. Barrels are adjusted properly. I replaced the TPS and initially thought it was solved on a long drive, but it now it's behaving the same again. Seems impossible a second TPS could fail so quick and exactly the same manner. I swapped out the sparkplugs and no change. I have read that there can be an issue with the wiring to the TPS failing, but I can't see how it would cause the behavior I'm seeing. Any thoughts? I know that CC sells the silicone TPS setup: https://caterhamparts.co.uk/looms/5817-tps-duratec-race-flexi-silicone.html

Were you guys on carbon or metal plates with your early failures?

#27. Woops yep other end of motor!

I had a high rpm, high load misfire caused by wire failure in the coil subloom to coil #1. My theory is that the coil cover puts stress on that wire leading to failure. I think that's why cc puts that hole there, with grommet to try to give more relief for the wire, but there solution is poor. I removed the grommet, which gives additional space for the wire to have a more gently curve. I repaired the broken wire and bought a backup subloom to have to quickly swap out if necessary.

Depends on climate and how and when you intend to use your car. Given the well-cooled oil on a street-driven 420R, a thinner oil would be reasonable I suppose. I'm running the cc-recommended Motul sport 5/50, but I have considered other options myself. Given that most of my miles are hard track miles, I've considered "upgrading" to a more racy oil like the 300V. However, given that I still drive it to the track on some cold mornings, and that my car spends a lot of time idling in the paddock trying to get heat into it, I worry about fuel dilution so I think running the thicker, wider-grade 5/50 makes sense for me. I'm still open to other options though. None of the car failures I've experienced thus far have been oil related, and I doubt they will be for some time, if ever...

Hmmm, I know that Exige/Evora with remote front mounted oil coolers leave a LOT of oil the system during an oil change, and those cars aren't blowing up willy nilly. Any oil change is just another serial dilution, but of course the more you get out, the better.

CC doesn't market it is a rccr for the road. I'm saying that it is closer to one than most other cars marketed as such. Unfortunately, it's up to potential buyers to understand what they're getting. Many 420R buyers would probably be better off with a 360S.

My point is that the 420r, with regards to its cooling, really is a "race car for the road", and not just a marketing fantasy like 99% of other cars labeled as such. Many people think they want that but actually don't. Get a rosd car for the road. For a 2.0 duratec 7, that means a wet sump car with modine cooler. Which cc also offers.

I think there may have been some logic. One thing to consider is that the oil coolers on the 420R racecars (run in the now titled 7 UK championship) look similar but actually are larger then those in the road-going counterparts. So apparently they decided that those cars needed even more cooling. They also modified to nosecone to allow for additional airflow. This suggests to me that cc has made some attempt to make these cars able to cope with the maximum heat demands that could likely be placed on them. Of course, that means they become less suitable as dual purpose machines. But real racecars don't have oil thermostats afaik. They are properly warmed up, then run hard. Which seems how the 420r is intended to be used.

My kit was missing one so i bought a 2" grommet on Amazon. Fit perfect. https://a.co/d/i2C4hIj

From my research an inline Tstat will only bump oil temps up marginally. I guess any improvement is improvement, but it wasn't worth the hassle for me.