JAL73

yes, new engine mounts and gearbox mounts, and new Redline diff oil as recommended by Road&RaceTransmissions. 

Was out in a friends roadsport which has a 2L duratec with 420 cams but not lightened flywheel. It has a ford 5 speed box (doesnt touch tunnel walls) and open BMW diff. That car had almost no NVH, no chattering on over run, silky smooth and very fast. 

Yes mine is the sintered plate titan. 
my understanding is that the titan LSD really only makes a noise when cornering and the clutch plates are engaged, my noise happens in a straight line and i though it was more likely crownwheel and pinion noise rather than the Titan going straight. 
 

I’ve been in a car with a tracsport diff that was even noisier than mine and other cars with Titans that were much quieter than mine, so I’m not sure in my particular case the Titan is the culprit 

So I got the car back and I’m very disappointed.
 

ScottR400D and Ainsley seem to be correct. 

Garage told me they had moved the gearbox clear of the tunnel walls, but it’s still in EXACTLY the same place. Engine mounts and gearbox mounts were replaced and it’s made no difference to NVH. The old mount had the spacer in it, as does the new mount.

As Ainsley pointed out the gearbox mounts are not slotted for side to side adjustment, only fore/aft. The gearbox mount itself is asymmetric with the mounting channel offset to the passenger side so it seems Caterham has deliberately chosen to have it skewed to the passenger side tunnel wall for some reason?!?
If the mount was symmetrical or offset the other way I guess the gearbox would be set more centrally in the tunnel.

Why Caterham has designed the mount asymmetrically I’m not sure, maybe to keep the gearbox output flange parallel to the diff input flange? 

The only way to get everything sitting perfectly in the middle of the tunnel would be have asymmetric engine mount arms and/or a symmetrically scalloped gearbox mount. This would keep the gearbox and diff flanges parallel I think and prevent touching. 

Anyway, this issue seems to be common to all Duratec/Mazda gearbox cars. See the video below from 5:25 which perfectly illustrates this. Interesting to note Caterham inserted a recessed cutout panel in the passenger footwell to try to accommodate this but mine is carpeted so I was unaware of it until seeing it at the end of the video below. 

Finally, I had a look at an S3 chassis car from  below whilst at the garage and the gearbox seemed to touch on BOTH sides, I guess because the tunnel is even narrower than on my SV chassis. I’ve never heard of S3 chassis cars having more NVH than SV chassis cars, so as ScottR400D suggested maybe the gearbox touching the tunnel wall is a red herring in terms of NVH because it’s just touching the heatproof padding and not really applying any pressure to the metal tunnel wall behind it thanks to the recessed cut out panel, though the jury is still out on that one for me…

What are the recommended tyre pressures (cold and hot) for Toyo R888Rs, for general road use? 

I’m on 185x60x13 fronts and 205x60x13 rears on a 420R. 

PM sent to you David

They are currently working on the car. I popped in to see them yest pm, the technician had just left for the day but the service advisor seemed to be of the opinion that the gearbox can be realigned to NOT touch the tunnel. There is clearly some space for the gearbox to move into on one side, whether its enough space to fully clear all points of contact on the other side where its touching remains to be seen.

They also showed me my gearbox mount which had the small spacer already sitting in it, it looks like its only a few mm thick. Also my gearbox mount was slightly bent in places where it attaches to the chassis so thats being replaced, im also going for new engine mounts as they are not expensive. 

Hopefully I'll have the car back on Friday so will have a definitive answer then.   

Still not had an anwer as to whether the circled appendage (see bottom pic below) is required for Caterham or is a redundant item from fitting to a Mazda MX5 or similar. If that can be removed and blanked off it would certinaly help. Anyone on here know if its a critical part for Caterham fitment?

2 hours ago, ScottR400D said:

I’d love to hear what HWM have to say. 
 

Caterham didn’t change the chassis when the Mazda box began to be used. Just like when they changed the radiators, diffs and anything else. Engineered? 🤔
 

By the way, back in 2020 I asked one of CC’s ‘experts’ to confirm that the Duratec sloped forward to clear the hood. His answer? “I have no idea”  

As I asked, do you have a Titan LSD? Sintered plates? You’ll never enjoy low levels of NVH with that if so.

A final comment. The accumulated knowledge and experience in these pages will outweigh that of HWM by orders of magnitude. I would be wary of how much time I wasted.    

 

All fair very points. If Mazda boxes are wider than their predecessors then i guess they would be more prone to NVH than earlier cars, unless being fitted with millimetre precision. If that's a fact, I've never heard it widely being cited, but you learn something new every day!

I guess it just comes down to knowing the width of the box and bellhousing relative to the appetures they sit in.
Im sure some knowledgeable person on these pages can prove or disprove the hypothesis with knowledge of the measurements in question.

2 hours ago, Ainsley said:

You have eliminated the Diff cradle touching the boot floor support ?

 

Im not sure on this, ill have to recheck, thanks for pointing it out

It’s going in to HWM tmrw and they are aware of the issue, will report back if they have any success in reseating it to avoid contact with the tunnel walls and checking the engine and diff incline angles. 

Surely Caterham have not engineered the width of the inside of the transmission tunnel to be less than or equal to the width of the widest section of the gearbox. I appreciate the tolerances maybe very fine but I’d hope it’s possible to seat the gearbox so that the only NVH transfer point to the chassis is via the gearbox mount. 

Im about to go on a road trip hence my renewed focus on NVH...

I was talking to Ollie at R&R Transmission about NVH and he said that the relationship between incline of the engine and the incline of the diff can stress the UJs on the propshaft and cause NVH to be transmitted from the engine to the diff. That sounds plausible but no idea how to test whether my car suffers from that particular ailment. Vibrating elements touching the transmission tunnel also seem highly plausible but not sure if this can be avoided with Duratec/ Mazda applicaiton given the tunnel width.   

I have been in other cars which seem quieter and less vibration than mine, so I know something on mine can be fettled to improve it. 
I love thrashing the pants off it on track but I also find unnecessary NVH irritating and dont mind the challenge of minimising it.

In my continuing quest to reduce NVH in my car I had a look at the placement of the gearbox in the transmission tunnel and noticed an appendage on the LHS of the gearbox touching some lining material on the inside of the tranmission tunnel walls (see pic) and wondered if this might be the a big contributor to the NVH I feel and hear. I have a 420 with Duratec engine mated to Mazda box and BMW diff. I've had vibration analysis carried out on the car with sensors attached along engine & drive train and been told theres no obvious rotational imbalances detected and been advised the engine mounts are not great at isolation, however I'm wondering if my gearbox seating/ placement might also be compounding the problem. 

Space is incredibly tight in the transmision tunnel so wondered if others have managed to fit their gearbox without any part of it touching the inner tunnel walls.
Also wondeirng what the circled appendage on the Mazda box is for and whether it can be removed and blanked off to give a bit more room to avoid touching the walls.
Im assuming it serves an important function so unlikely to give me the breathing space Im looking for!

Thanks that’s helpful info. Maybe I’m being too resistant to the change over…

Did you feel the need to re-do your geometry and corner weighting when switching from ZZS to R888Rs given the difference in dimensions etc? 

Is the R888R softer, harder or very similar compound to the  trusty ZZS. 

Just reviving this thread - as more and more people will have switched from from Avon ZZS to Toyo R888R on 13" wheels by now, how have you found the switch? Any pros or cons?

Do the R888R have a stiffer sidewall than ZZS?

Has any one had issues with the taller sidewalls on the fronts rubbing the cycle wings? 

13 hours ago, Ballast-ic said:

I recently replaced my rear shocks with Protechs and noticed an immediate difference in improved road holding, so you don't need to spend £thousands on Nitrons and the like. Having adjustable dampers is also a bonus so you can tighten up for track days. Echo previous comments on tyre pressure and ARB. When I first got the car, tyres were at 21 cold and it bounced around like a wild thing. Dropping down to 18 cold transformed it. Also setting rear ARB to lowest setting  definitely helped make it more predictable.

Fiddling with relatively small settings in a number of areas make significant differences, but the biggest difference I did was the Protechs, which were bog standard from Protech.  

I've had a look on the Protech website but when you search for their Caterham offerings it says 'no products listed'

Which particular damper and spring combination did you go for? Do they have fitting/ geo setup facilities there also or supply only?

Their product offering seems dramatically cheaper in price than the more well known brands offered by the well respected Meteor motorsport. Just wondering if anyone has any experience comparing Protechs vs Nitrons, Core or Penske - is it a question of you get what you pay for or are these Protechs really just better value for money. My question is in the context of ride comfort on the road, not shaving seconds off laptimes. 

the other issue i have, which i think is also suspension related, is when you go over bigger bumps/ potholes you sometime get a horrible (bang/ crash) noise coming from rear of the car but whenever i look under the car i cant see/feel anything loose. I thought it sounded like it was coming from DeDion tube but HWM who service the car assure me its not that, so maybe its the dampers. Curious as to whether others out there have experienced similar and managed to trace the source of it?   

i took off my rear ARB and it did seem to improve things a bit.
i only did the rear cos thats where poor road surfaces seem present the problems but i havent tried the front ARB - would removing the front improve ride comfort much?

Has anyone tracked a 420R with all ARBs removed? I reinstalled my rear ARB cos thought it would understeer a lot on track without it but i really dont know what im doing.

Also, for those that have removed all ARBs - did you then do a flat floor chasis set up after on standard Bilsteins and get nice results?

I’m already on 13” Apollos with Avon ZZS tyres….! 

What is it about the standard 420R suspension that people think is inferior to the various available upgrades out there for compliance on the road?

Is it the Bilstein compression or rebound is too slow or the springs are too stiff? Apologies if that’s an over simplistic question but i was just wondering if its the damper or the spring that contributes most to peoples dissatisfaction with the standard Bilstein components.  

I am considering upgrading the Bilsteins on my 2020 420R SV in search of refining the way my car handles bumps and poor road surfaces.
My car can be quite crashy over bad surfaces and prone to the rear skipping over bumps at high speed, Im wondering whether this is just something inherent in such a light weight car or whether its possible to achieve a really significant improvement in ride quality with better suspension components and a proper set up.

It seems the price of suspension upgrades plus geo/flat floor starts around £2k and goes up to about £8k which is a serious chunk of money.
Curious to know what other owners have upgraded to and whether they think its worth the money? Appreciate its a quite a subjective topic.

Please note im more interested in improving compliancy and road manners rather than shaving seconds off lap times! 

I had this issue and was told that my reluctor ring on the RHS drive shaft had slipped out of position. I have a 2020 420R SV.

Next time it was in the garage they moved the reluctor ring back into position and secured it and Ive not experienced any issues with my speedo sticking since that fix. 

Has anyone ever used these chaps in Bicester for vibration issues? 

https://vibrationfree.co.uk/our-services/motor-sport/

Looks like they specialise in A-Z of resolving engine vibration issues and also seem to have developed the "sterling damper" a torsional vibration absorber for cranks. Didnt know such things existed...

22 minutes ago, ScottR400D said:

Could be as much to do with the fuelling set up as anything else. Has it been set up since leaving the factory? 

It used to have lumpy idle, kangaroo and serially fouled its plugs which was down to corrupted map and faulty TPS but this has been resolved perfectly. 

yes its seems to be engine speed dependent, the vibration seems to diminish above 2-3k rpm i think but not really been able to measure this scientifically.

the car has a perfectly smooth idle around 950rpm and drives beautifully, its just the low rpm vibration that ive noticed

I have read Aerobods very impressive account of his engine teardown and rebuild and feel somewhat blinded with science. I didnt want to detract from the purity of his thread with an amateur question but I noticed the incredible lengths he went to, to ensure all the engine components were equally weighted alongside the balancing of crankshaft and flywheel.

I assume the reward for a meticulously balanced engine like that is engine vibration is minimised across the rev range. 

The reason I ask is because i have always wondered what causes noticeable vibration on my car at idle and other engine speed dependent NVH at other parts of the rev range. For example, at idle if you hold the headlight bowls you can see and feel them vibrating.

To this end, I was wondering whether other owners out there have ever spent time and money rebalancing their engines in search of minimising engine related vibration. Ive no idea if this sort of thing is prohibitively expensive or who the specialists out there are. 

My car is a 2020 420R on 5k miles so I assume most of the vibration im witnessing might be a balancing issue rather than failed or worn engine mounts. 

I have managed to erradicate pretty much every rattle and squeak on my car (there were many...) and so now im interested to see if vibration is something that can be fettled out to some extent. I realise its a Caterham and "they all do that sir" but there is usally a rational engineering explanation for why they do it and what can be done to minimise it!

I've learned to accept the CWP noise from the diff however, so not sure that will ever be as quiet as I'd like it to be...

Let’s say the front KNs are 0.5kg heavier each corner and rears maybe 0.7kg (?) heavier each corner, would you notice that difference in unsprung weight in terms of handling/ performance?
 

I have a set of Apollos on ZZS already for road biased use and was thinking of getting a set of KNs with ZZR equivalent rubber on them for summer track use, but sounds like the Apollo is a better performance wheel given its lower mass, just not sure how much difference you’d notice