tomwood Posted September 12, 2016 Share Posted September 12, 2016 Car was in for its first MOT today which it duly failed but whilst it was there, one of the guys testing it remarked at how much the input plenum flexes on my car under load. I went home and took a video of it. Must admit it does look quite bad. Does anyone else have this problem on their Duratec Car?im worried that over the course of time all that flexing is going to result in cracking and If any of it were to break off and get ingested it wouldn't be pretty.Is this a known issue? How worried should I be? What if anything could I do about it?Thanks,Tom Link to comment Share on other sites More sharing options...
shn7 Posted September 13, 2016 Share Posted September 13, 2016 Looks like it's very thin walled . Clearly a weight saving measure and would have been very acceptable to ACB as long as it crosses the finish line before breaking.No idea if TADTS as I have no Duratec experience. Link to comment Share on other sites More sharing options...
ScottR400D Posted September 13, 2016 Share Posted September 13, 2016 When did you last change your filter? Looks to be a lot of resistance there. Link to comment Share on other sites More sharing options...
7 wonders of the world Posted September 13, 2016 Share Posted September 13, 2016 Opportunity here to sell this into SWMBO as a safety upgrade and get some TB's fitted Link to comment Share on other sites More sharing options...
Clousta Posted September 13, 2016 Share Posted September 13, 2016 Looks a tad concerning. Reminds me of the time I had an MG Metro Turbo (I know, I know but it was la ot of fun and Lotus were involved in the tuning/turbo charging) coming home on the A30 on a filthy wet night gradually I couldn't rev about 3,000 rpm. Everything else seemed OK so I nursed it home. I thought I had blown the turbo but the next morning in daylight the cause was obvious and much like the video. The air filter was mounted remotely and connected to the engine via a large diameter wire-reinforced paper hose. Over the years the paper hose had become soaked in oil (it was still an A-series engine) and the torrential rain and consequent spray on that night had caused the hose to collapse every time the engine revved. At 3,000 rpm the hose was almost flat. An easy fit but worrying at the time. Link to comment Share on other sites More sharing options...
tomwood Posted September 13, 2016 Author Share Posted September 13, 2016 Well the filter has never been changed but then again the car has only done 2500 miles so I wouldn't expect it to need changing yet. Will certainly have a look at it.throttle bodies - like that suggestion, not sure I'll get it past SWMBO though, she's not as daft as I'd probably like her to be!im also sure I would have noticed this before if it was always like that. Starting to think this is getting worse. Could the plastic have become weaker over time? Car is only 3 years old and spends its life in the garage so isn't having a hard time.car was tracked 3 weeks ago and wasn't at all down on power and suspect I would have noticed of there was some sort of restriction. Link to comment Share on other sites More sharing options...
7 wonders of the world Posted September 13, 2016 Share Posted September 13, 2016 Link to comment Share on other sites More sharing options...
ScottR400D Posted September 13, 2016 Share Posted September 13, 2016 It's odd. Your filter should be fine after that mileage. I've just looked at my plenum, not running, car's up on stands for oil change, service etc. The plenum seems very solid and firm, can't imagine it doing what you're seeing but I'll check when I start it. Link to comment Share on other sites More sharing options...
JNC Posted September 13, 2016 Share Posted September 13, 2016 A simple test ! Remove the air filter and run the engine while checking the plenum chamber , no flexing replace the filter. Link to comment Share on other sites More sharing options...
ScottR400D Posted September 13, 2016 Share Posted September 13, 2016 That's a good idea, so obvious now we hear it! Link to comment Share on other sites More sharing options...
Ian Mackenzie Posted September 13, 2016 Share Posted September 13, 2016 What did it fail on...and did it pass the emissions?CheersIan Link to comment Share on other sites More sharing options...
JNC Posted September 13, 2016 Share Posted September 13, 2016 Never think because the filter isn't very old ! It depends what has been sucked into it , it may look clean but still be blocked. Link to comment Share on other sites More sharing options...
Mark w Posted September 13, 2016 Share Posted September 13, 2016 I would be worried about that if a new filter doesnt cure it .Saw an engine completely trashed when the air box disintegrated and bits found their way into the cylinders .............. Link to comment Share on other sites More sharing options...
garybee Posted September 13, 2016 Share Posted September 13, 2016 It's the other way round guys. Flexing is under max vacuum with engine at idle. Plenum releases to natural position as revs increase/vacuum reduces. Nothing to do with the filter. Doesn't mean a brace wouldn't hurt. I Have a spare one of these, will have a look to see if there's a threaded hole/location for a brace.Gary B Link to comment Share on other sites More sharing options...
ScottR400D Posted September 13, 2016 Share Posted September 13, 2016 Well, I see Tom has posted some other video on YouTube revving the car without filter so he'll no doubt be along soon to tell us what it did.It's hard to see in the video whether it is still flexing or not. Link to comment Share on other sites More sharing options...
tomwood Posted September 13, 2016 Author Share Posted September 13, 2016 Very eagle eyed of you! Yes indeed some more testing has been done.heres a video of me cracking open the air box and here's me inspecting it: It's a bit dirty but nothing to write home about. I've seen a lot worse. Once it was removed I redid the test and, although this is not a great video, it behaved near enough identically to when the filter was still in it. I'd have to agree with a previous comment which is that it appears to expand once the air is sucked into it. It's almost like the plastic has deformed slightly in on itself when at rest. Could you tell me more about this bracing idea, sounds promising.also if anyone else has the same plenum, would be grateful to see if mine is a one-off or whether they all do this.with regards to it failing the MOT, it failed on 2 things, handbrake needs tightening slightly (easy) but the reason it didn't make it through is it had a blown rear damper. Not bad going for under 3000 miles! It's been sent away to Bilstein in the post to be refurbished. Apparently it's quite common for dirt on the damper shaft to burst the seal if and when you hit a particularly large bump in the road and the damper travels further than normal. I'm currently hunting for some damper socks to see if I can keep the dirt away. Passed the emission test no problem. Link to comment Share on other sites More sharing options...
ScottR400D Posted September 13, 2016 Share Posted September 13, 2016 So when you rev it up the top surface of the plenum lifts? And switched off it is in the 'sucked in', lower position as at idle? Link to comment Share on other sites More sharing options...
tomwood Posted September 13, 2016 Author Share Posted September 13, 2016 Ok just been back out to double check what's going on. As luck would have it the sun is now in a better position to make this clearer in these 2 videos:its seems as though at rest the plenum is the correct shape. When you start the car and leave at idle there is then a vacuum powerful enough to deform the plenum (sucking itself inwards from its rest position). You can see that here: and here's a better side on view at rest, at idle and then revving. It looks a lot like someone blowing into a paper bag! i guess you could brace it externally to stop it ballooning outwards but to overcome the vacuum issue you'd need bracing on the inside surely?i definitely don't want to be buying a new one if I can help it. Just looked on the Caterham Parts site and it's over £500 for a new one! Link to comment Share on other sites More sharing options...
garybee Posted September 13, 2016 Share Posted September 13, 2016 I was on the tablet before so couldn't type a more thorough response without losing the will to live.The greatest vacuum is at Idle as the engine is sucking against a closed throttle plate. As you raise the engine revs the vacuum decreases therefore the deflection of the plenum moves closer towards the 'at rest' position. It appears the other way round because you start watching with the engine at idle. When the engine isn't running, the vacuum is no longer present within the plenum so it will return to the 'at rest' position. It's slightly counter intuitive if you don't understand how an engine works.If there is room for a brace beneath the plenum to resist the downwards movement that would be one way to go. If the plenum is still within it's elastic deformation range the brace would be a waste of time and effort of course. Are these known for failing? If so then it would be a worthwhile exercise and I could easily knock up a brace to transfer the load to a spare boss on the block. Something tubular and carbon so that it looked sufficiently 'Caterham' of course. It wouldn't necessarily need to be bolted to the plenum as it would be pulled on to the mating face as vacuum increased. If failures are common I'd knock up a batch and put them in the trading section of course. edit: added punctuation Link to comment Share on other sites More sharing options...
shn7 Posted September 13, 2016 Share Posted September 13, 2016 Having seen the video's and read the updates I conclude this is a faulty part. No way should it be thin enough to flex like that. I'd be very nervous about using it like that for fear of it collapsing at some time and being ingested into the engine. That would cost a lost more than £500 to fix.I wonder if someone who has upgraded to throttle bodies has a spare to pass on for less than the new price or on loan to test to prove this one is not up to standard? Link to comment Share on other sites More sharing options...
tomwood Posted September 13, 2016 Author Share Posted September 13, 2016 Hi Steve that's a great idea. I'll put something in the sales section to see if there's a spare going.would very happily test and return one loaned to me as well if any one was willing to do so. Link to comment Share on other sites More sharing options...
John Vine Posted September 13, 2016 Share Posted September 13, 2016 I have an old-style R400D alloy plenum, complete with throttle, sitting on my garage shelf, redundant after I upgraded to RBs. It may not fit in with your battery but if you're interested I'm sure we could come to some arrangement.JV Link to comment Share on other sites More sharing options...
tomwood Posted September 13, 2016 Author Share Posted September 13, 2016 Hi John, thanks for the offer. Can I check, is your one this design with the air filter on the end?https://goo.gl/images/rxeeFBIf so, i wonder if could route the existing pipework from the air filter into it rather than having the K&N type filter on the end. Might still foul the battery/heater but it might just work Link to comment Share on other sites More sharing options...
garybee Posted September 13, 2016 Share Posted September 13, 2016 Tom,Just seen my last post overlapped yours. You are correct in that bracing the plenum will only counter the tendency for it to be pulled downwards at idle. If the sides of the airbox are deflecting inwards there's nothing you can realistically do about that. Again, if it's only deforming elastically then it really isn't a problem. I've only had a quick search but can't find any people complaining of plenum failure. If they were letting go I would expect lots of posts on here about it. Gary Link to comment Share on other sites More sharing options...
SM25T Posted September 14, 2016 Share Posted September 14, 2016 That looks worrying in the video ! Our continuing policy of product cheapening ? Link to comment Share on other sites More sharing options...
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