Incoming 420R, California

[Nocturnal005]

Went on a shakedown yesterday, finally got the rev upshift light to turn on, sounds great! 

[KnifeySpoony]

It's not slow, is it...  The intake sound is glorious as well. You can really hear when it comes on cam and gets into it's happy place. bwaaaaaaaaaa

[Nocturnal005]

It's definitely not slow, although it's tough to tell how quick it really is due to the onslaught of wind. It's a different character to the last few cars that were all turbo charged and had endless torque, but those motors didn't have the same responsiveness. Its also been a while since I had a stick shift so that's a treat!

 

 

[KnifeySpoony]

Yeah I always do full face helmet because aeroscreen. Above 55mph or so it gets bad fast. And yea the throttle response with NA and ITBs is par excellence. I'm all about it. Many benefits, including the ability to dial in your yaw angle with great precision without any lag. 

[Nocturnal005]

Anyone weigh their aeroscreen 420R yet? I'm wondering how close I'll end up to the 540kg stated weight. 

 

I'm definitely getting used to the car.  I'm glad I went with the 420, I don't think I'd want less power. In fact, 30 more would be nice. Open to ideas!  =) I am second guessing the choice of the 5 speed I chose vs the sequential, but I don't think there's a right answer here.

 

The cup shocks seem like a pretty versatile upgrade. I think I'd recommend them if you are in the market for a 420r. The adjustment range is huge, prob too large to fully use all 10 clicks actually. On a setting of 6 front, 4 rear (out of 10) the car has a reasonable sporty ride on rougher roads. On settings of 9 or 10, the car feels like it has no suspension. Prob best on a super smooth track. Each click makes a discernible difference from the cockpit. 

 

I'd also recommend the scroth 6points over the standard harnesses. the lap belt buckles are slimmer and end up above the sides of the carbon buckets. It's easier to slide down into the seat since you aren't trying to slide down past the bulkier luke buckles which also happen to want to occupy the same space as the seat sides. Tthe scroth belts are way more supple and 2" vs 3" which makes a comfort difference. 

 

This car is absolutely the most fun I've had on 4 wheels, and I've been fortunate enough to try plenty of others. Perhaps I'm in the honeymoon phase but I can't recall having more fun than this. 

 

Can't wait to take her to the track! 

[KnifeySpoony]

Do you know the spring rates on the cup dampers?

 

re: weight. I weighed mine (420R, roller barrels, trackday rollbar, no heater, CF aeroscreen/mirrors, CF tillets, CF front wings, CF interior panels, OEM Banner battery, about 2/3rd to 3/4 tank of gas) and it was 1230lbs. I have since gone to an antigravity battery, so I think that was like 15lbs savings. So I assume with half tank of gas it's under 1200.  540kg wet is a fantasy by Caterham. 

[Nocturnal005]

10 hours ago, KnifeySpoony said:

Do you know the spring rates on the cup dampers?

 

re: weight. I weighed mine (420R, roller barrels, trackday rollbar, no heater, CF aeroscreen/mirrors, CF tillets, CF front wings, CF interior panels, OEM Banner battery, about 2/3rd to 3/4 tank of gas) and it was 1230lbs. I have since gone to an antigravity battery, so I think that was like 15lbs savings. So I assume with half tank of gas it's under 1200.  540kg wet is a fantasy by Caterham. 

thanks, that’s useful. I’ll weigh the car myself mid June and will report back.

 

Re the spring rates, I did look but I don’t think they are marked. Curious myself. Will let you know if I find out more or get them measured.

[KnifeySpoony]

Oh also i have a decat pipe on mine, that's a decent weight loss right there.

[Nocturnal005]

Ok, I'm ready for a bit more power and a little less weight. I think I want to do a decat pipe, but am thoroughly confused by the parts website. My guess is this is the correct fitment, but they don't seem to have a polished version. 

 

Also, anyone have luck with custom mapping? The factory maps seem to be rich. I would like to know what gains I might expect; it's been a while since I've had an NA car. If the gains are ~5hp or so I'll not bother, but if double digits can be found I'm all in. 

[11Budlite]

I'm pretty sure there is no polished version. I ended up installing one on my Sigma-powered car and had to polish it myself. It saved almost 4.5 lbs.

 

Sorry I can't help you on the mapping.

Edited July 29 by 11Budlite

[Nocturnal005]

I finally corner weighted the car. With 1/2-3/4 tank of gas the car weighs in at 1206 lb, which is 548kg. Since the curb weight is supposed to be 560kg, I’m pretty happy with this! 

Edited August 21 by Nocturnal005
Found the heavy car cover in the trunk

[empti]

On 5/21/2025 at 8:07 PM, KnifeySpoony said:

Oh also i have a decat pipe on mine, that's a decent weight loss right there.

I am wondering, how much louder it is after the decat pipe? I am thinking about it. 

[KnifeySpoony]

I put it on during initial build so nothing to compare to. That said, it's definitely not that loud in general. In fact I cannot hear any exhaust noise over the roller barrel intake noise. If i'm up against the wall to my right at the track, then I can hear it a bit.

[11Budlite]

I know the Duratec could be different, but for my Sigma-powered car it's a little bit louder but I never measured the difference. To me it sounds better, but it is still not close to the loudest car that I run with on track. No problems passing any of the sound limits at the tracks I frequent.

Edited August 22 by 11Budlite

[KnifeySpoony]

Oh - re: sounds limits, I blew a 95db at Laguna, so no go on most days there. I had a custom rear exit pipe made but blew a 95db again lol. And that is with the sound station off to the right. I think the intake is the loudest thing. I do have a full Caterham trackday exhaust setup with cat and second rear muffle but I've yet to try it.

[Croc]

25 minutes ago, KnifeySpoony said:

Oh - re: sounds limits, I blew a 95db at Laguna, so no go on most days there. I had a custom rear exit pipe made but blew a 95db again lol. And that is with the sound station off to the right. I think the intake is the loudest thing. I do have a full Caterham trackday exhaust setup with cat and second rear muffle but I've yet to try it.

 

The thing with noise is that it depends on how (static or on track drive by) and where they measure it plus the decibelometer they use.  

 

If you have standard 420R intake then with the Caterham twin muffler track set up, my UK 420R consistently runs 90db so I can use it on 92db noise restricted tracks in the UK  and Europe.  I have the cat bypass set up for this noise reading.  However at Goodwood I was struggling to get it under 92db.  They describe their system as "thorough'.   I used another two words that day to describe it.  

 

The use of a cat pipe knocks a couple of decibels and probably 5hp off that.  Plus the fact is that you will use it up pretty quickly on track - so it is an expensive noise reduction technique.  Cat converters are very expensive animals these days.  

 

If you add the roller barrel intake setup then that adds an extra 5-10db of noise (depends on track and mic placement).  Most Caterhams in the UK then use air boxes or the like to encase the intake to limit the noise and pass the 92db noise tests or just limit themselves to 95db tracks.  The intake is a real source of noise if you have to pass a track sound limit.  Fortunately most US tracks do present us with that issue.  

 

[Nocturnal005]

Who are you guys using for insurance? Looking to get liability coverage only. Anyone have issues with state farm?

 

This morning I was able to go to the BAR inspection and now have a crookedly placed, but official SB100 exemption sticker! One more trip to the DMV and this entire reg process should be DONE! 

 

 

[hahuang65]

No issues with State Farm. Mine got insured as a 2024 Caterham 420R a week ago.

[Vovchandr]

I have state farm and my only issue is that it's not an agreed value policy. Since you want liability looks like that doesn't matter to you either way. 

[hahuang65]

1 minute ago, Vovchandr said:

only issue is that it's not an agreed value policy.

May I ask why this is an issue? I think I need some education around this.