JNC Posted September 14, 2016 Share Posted September 14, 2016 I now understand its on tick over while the butterfly is shut restricting the incoming airflow causing the partial collapsing of the plenum ! . When I was still using the plenum on mine I never saw what you are experiencing so I would say it's a defective part , Have you spoken to CC ? Link to comment Share on other sites More sharing options...
Dr Slotter Posted September 14, 2016 Share Posted September 14, 2016 To use the old-style alloy plenum I reckon it'll be much easier to swap the location of the battery and airbox and use an appropriate K&N that fits.You might need a new throttle body too, but I'm not familiar with the layout of the plastic plenum/single throttle body setup. Link to comment Share on other sites More sharing options...
John Vine Posted September 14, 2016 Share Posted September 14, 2016 Yes, that pic is exactly like mine -- angle, TB, K&N and all.I agree with Dr S re moving the battery. Can't comment on the airbox as I never had one.JV Link to comment Share on other sites More sharing options...
Dr Slotter Posted September 14, 2016 Share Posted September 14, 2016 Sorry, I really meant "move the battery to where the airbox currently is and then not use the airbox". I get a photo... Link to comment Share on other sites More sharing options...
Dr Slotter Posted September 14, 2016 Share Posted September 14, 2016 ...or photos! Link to comment Share on other sites More sharing options...
tomwood Posted September 14, 2016 Author Share Posted September 14, 2016 Thanks guys, this certainly looks like an option that could be worth considering then by the looks of it. Can't imagine relocating the battery to be all that difficult. Likewise the air box will be easy to remove.just so I'm clear, the throttle body is the bit between the plenum and the filter with the butterfly valve correct?ill have a look more closely at mine and see if it looks like those in the photos (thanks for those). I'll try and work out whether it would likely fit the alloy plenum. Hopefully it's a like for like swap.i think I'd probably be best calling Caterham first to see what they have to say about it. If they think for certain it's not normal then I'll need to start thinking of what option to take.John - are you happy for me to contact you as and when? Link to comment Share on other sites More sharing options...
slap_ed Posted September 14, 2016 Share Posted September 14, 2016 Not sure if this video will work. 1st attempt i don't think mine is as pronounced as yours. See what you think? Link to comment Share on other sites More sharing options...
tomwood Posted September 15, 2016 Author Share Posted September 15, 2016 Thanks for that. Have watched it several times now. Yours does have some flex for sure but not to the same degree as mine I don't think.how old is your car? I'm wondering if mine has got progressively worse over time. Link to comment Share on other sites More sharing options...
Rattie Posted September 15, 2016 Share Posted September 15, 2016 Tom, I suspect you've got a particularly thin casting. Definitely should talk to Caterham about it. Your videos show the issue very well. If I were you I'd avoid switching to the alloy boat anchor. It causes heat soak issues, particularly on trackdays. Not only does it pull air from behind the hot block, it also then adds soaked heat from the block for good measure.That and it weights a ton!If CC think it's normal, ask them if they are happy indemnifying you against the cost of an engine rebuild if it does fail and get eaten. Link to comment Share on other sites More sharing options...
slap_ed Posted September 15, 2016 Share Posted September 15, 2016 Mine is a 2011 year. I wouldn't have thought yours is getting any worse than from new. Your plastic is predominantly thinner causing it to flex more easily. The question is whether it is within the manufacturers tolerance.i must admit I've never noticed mine doing that until I checked after seeing yours. Link to comment Share on other sites More sharing options...
tomwood Posted September 16, 2016 Author Share Posted September 16, 2016 If anyone else could do a comparison for me it would be appreciated. In the meantime I'm going to discuss with Caterham to see what they think. Link to comment Share on other sites More sharing options...
tomwood Posted September 16, 2016 Author Share Posted September 16, 2016 So, spoke to the Main Technician at Caterham South. Apparently the design of these have been changed more recently to make them a bit stiffer but he has watched the better of the videos I took and reckons that its well within what he would consider to be normal.So its a case of TADTS. I will however be watching it very closely to see if it gets any worse. Link to comment Share on other sites More sharing options...
John Vine Posted September 16, 2016 Share Posted September 16, 2016 I'd agree with Rattie that the plastic plenum is a better all-round bet than the alloy one. When I was up with the Two Steve's in Sep 2010, Steve P was less than complimentary about the alloy item for the same reasons (heat soak etc). He had a 7 there fitted with the plastic plenum (possibly under test as I think it was before CC switched over), and said the lack of kink in the body of the plenum improved airflow.John - are you happy for me to contact you as and when?No problem. I'l PM you my contact number.JV Link to comment Share on other sites More sharing options...
tomwood Posted September 16, 2016 Author Share Posted September 16, 2016 Thanks John, what you and Rattie have said makes a lot of sense. Also in light of the feedback I got from Caterham today I'm inclined to stick with it and monitor it for now.it is interesting though that I was told the design has been made stiffer recently. I did ask if they'd seen any failures of the plastic plenums and i was assured there hadn't been any. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted September 17, 2016 Member Share Posted September 17, 2016 Do you want to add some external stiffening?Jonathan Link to comment Share on other sites More sharing options...
tomwood Posted September 17, 2016 Author Share Posted September 17, 2016 Probably but not sure how best to do it. What did you have in mind? Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted September 17, 2016 Member Share Posted September 17, 2016 The neatest solution would be a stiff exoskeleton, but hard to get the points of contact right. Ribs and backbones? Could be done in plastic with 3D printing or in aluminium using water jet cutting. (I don't understand carbon fibre reinforced plastic.)But it might be possible, and would be a lot simpler, to use long worm drive strips and clips. How about a couple around it at 1/3 and 2/3 of the long axis?Jonathan Link to comment Share on other sites More sharing options...
JNC Posted September 17, 2016 Share Posted September 17, 2016 By trying to reinforce the plenum your self and the possibility of it going wrong and causing engine failure you will have no hope with CC , Personally I think take a very firm stand with CC and demand a replacement !. Especially now you know they are making the newer ones reinforced !. My 2012 car never had a problem , I think yours is defective . Link to comment Share on other sites More sharing options...
SM25T Posted September 17, 2016 Share Posted September 17, 2016 If plastic keeps flexing .... It must come to a point where it eventually fails. How long that is ... is the gamble. Link to comment Share on other sites More sharing options...
tomwood Posted September 30, 2016 Author Share Posted September 30, 2016 Thanks to JNC who kindly spotted one for sale on eBay for me this week, I have just secured a new replacement at a fraction of the cost of a new one from Caterham so will fit it once it arrives and do a comparison video. Link to comment Share on other sites More sharing options...
nickh7 Posted October 1, 2016 Share Posted October 1, 2016 Result, thanks for the update Link to comment Share on other sites More sharing options...
tomwood Posted October 9, 2016 Author Share Posted October 9, 2016 So, finally had the chance to fit the new plenum. Struggled to get the old one off at first because some of the bolts were inaccessible. Made all the more easy once the belt tensioner was removed from the engine so for those doing this job in the future, do this first and save yourself some time.The new plenum is definitely different in its composition. I took photos of the inside of both old and new and they are noticeably different textures. That said, that's about the only distinguishing factor, they otherwise look the same.have done another comparison video now it's on the car: the lighting isn't great so sorry about that. To me it looks marginally better but it does still flex a fair bit. Link to comment Share on other sites More sharing options...
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