JAL73 Posted March 17 Share Posted March 17 (edited) 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... Edited March 17 by JAL73 Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted March 17 Member Share Posted March 17 27 minutes ago, JAL73 said: 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. Does the vibration disappear if you lift the speed from idle slightly? Jonathan Link to comment Share on other sites More sharing options...
JAL73 Posted March 17 Author Share Posted March 17 (edited) 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 Edited March 17 by JAL73 Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted March 17 Member Share Posted March 17 28 minutes ago, JAL73 said: 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 The experts should be along RSN. I don't expect that to be caused by mechanical imbalance of the engine. Jonathan Link to comment Share on other sites More sharing options...
ScottR400D Posted March 17 Share Posted March 17 Could be as much to do with the fuelling set up as anything else. Has it been set up since leaving the factory? Link to comment Share on other sites More sharing options...
7 wonders of the world Posted March 17 Share Posted March 17 Caterham are not subject to NVH development in the same way tintops are... Costs...! We have engines and transmissions mounted on rudementarry metalaltic mounts many of which date back to.the early 1960's... Different frequency of resonance can manifest themselves in vibration or noise booming etc as you have found alterimg the engine speed changes this frequency equally just placing your hand on the headlight has the same effect.. Bonnets, rear arches, headlights, steering wheels can all.show these symptoms but unless you have had recent engine work clutch replacement etc or encountend and engine or transmission problem it's unlikely to be e major problem. If the headlight become annoying you cod slightly alter the engine idle speed or add a small piece of noise deadening material inside the headlight bowl. Link to comment Share on other sites More sharing options...
JAL73 Posted March 17 Author Share Posted March 17 (edited) 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. Edited March 17 by JAL73 Link to comment Share on other sites More sharing options...
JAL73 Posted March 17 Author Share Posted March 17 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... Link to comment Share on other sites More sharing options...
ScottR400D Posted March 17 Share Posted March 17 30 minutes ago, JAL73 said: 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. In that case I’m with 7 Wonders. Link to comment Share on other sites More sharing options...
oilyhands Posted March 18 Share Posted March 18 On 17/03/2024 at 19:52, JAL73 said: 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... Many many times, they do an excellent job, highly recommended, not cheap but very good. The sterling damper(or ‘rattler’) is a novel solution and replaces a dual mass front pulley Link to comment Share on other sites More sharing options...
Rob Walker Posted March 18 Share Posted March 18 I can also testify to the professional work carried out by Vibration Free. Good company to deal with. However I find most of the vibration on the sevens I have owned comes from the exhaust can and the poor way that it is isolated at the cockpit end. Link to comment Share on other sites More sharing options...
aerobod - near CYYC Posted March 19 Share Posted March 19 I think that many variants of the Duratec have a natural vibration in the 2000 to 3000RPM range, especially the variants without balancer shafts. Quite a lot of discussion on Mazda groups about it. My R400 engine had it around 2500RPM from new that induced a “buzz” through the chassis, especially on the overrun. If it is only apparent at lower RPMs, internal engine balance likely won’t have any effect on it. Link to comment Share on other sites More sharing options...
D Jones Posted March 19 Share Posted March 19 Another vote for vibration free, they balanced my K series crank, TTV 3.2kg flywheel and clutch last year when Rob at Ratrace built my engine. Link to comment Share on other sites More sharing options...
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