Duratec Vibration - Can you help?

[spiderlane]

Hi All,

 

I'm looking for some help in diagnosing/resolving an issue with my car (or at the very least establishing whether it is just a characteristic which cannot be changed).

 

The Car : 2010 R400 Dry Sumped Duratec SV, kit built (by me) with all standard Caterham parts. It has been mapped by the 2 Steve's at T'N'R.

 

The Symptoms : The engine seems to have noticeable vibration which pattern (above what I would consider the normal vibration from an engine in a Caterham) which varies with revs. At idle it's really quite a noticeable and uncomfortable teeth rattling experience. As you go up the rev range it becomes a much higher frequency "tizz" which can be felt through the steering wheel and chassis. Over a period of time I actually find that my hands start tingling with a slightly numb/pins & needles sensation. I've just come back from a 2,500 mile European tour yesterday and I can still feel some numbness in my right hand today because over long distances it becomes really quite irritating. It's definitely not from the rolling chassis, because if I dip the clutch at, say, 80mph where the vibration is quite strong, then it goes away completely and it can just feel the usual road vibration. Also I can feel the vibration with the car stationary in the garage. I've had a Caterham before (albeit a K series) so I like to thing I'm pretty familiar with the usual Caterham noises, feelings and vibrations.

 

Some Background : I don't remember having this vibration when the car was new, however it went back to Caterham after a 1000 miles to have the sump pan replaced because it was leaking. I can't be 100% sure, but I seem to recall it becoming noticeable after the car came back. I'm not sure what replacing the dry sump pan involves, but could the timing have been disturbed during that process? (I think that the timing sprocket isn't keyed?). Would that causes such symptoms? The car pulls and revs fine through the range.

 

I have carried out a spanner check to make sure that the engine and gearbox mounts are tight. Is there anything else that I can check?

 

Could it be a flywheel or clutch imbalance? Would there be any reason why this could have developed? I'd be grateful for any help, suggestions or input from people experienced with this engine or people with a similar car with the same or differing experiences.

 

The car runs well in every other respect, but this vibration is making long distance drives quite uncomfortable and is starting to spoil the driving experience for me. I'd really like to understand the problem and see if there is anything which can be done.

 

Cheers for any and all input,

Mark

 

Edited by - spiderlane on 1 Sep 2011 12:31:56

[Paul Deslandes]

I have a similar situation with my Vauxhall engined car. I did all the things that you've done plus replaced the engine and gearbox mounts and had the engine/clutch assembly fully balanced by Vibration Free, all to no real benefit but at least I know its not a rotational imbalance. My suspicion is that its the exhaust although I've checked that its not touching the chassis tubes where it comes out through the side. I have a big heavy duty Powerspeed Exhaust system and I suspect that the mounts may be too hard and the vibration is being transmitted into the chassis.

 

If I can get someone to help me sometime I'm going to try sitting in the car with the engine running and try levering it gently to one side and maybe jack it slightly, just to see if it makes any difference. I suspect too rigid mounts or actual mechanical contact. One possibility with a Duratec is that the exhaust vibration is being coupled into the steering column which I guess is on the same side. Maybe get someone to press/lever against major components with a lump of 2x2 to see if it makes any difference.

 

Not a lot of help I'm afraid but you're not alone!

 

Paul

[jonboylaw]

Check the steering column as it passes by the engine mounts etc... it might be coming into contact with the DS pump or mounts. I am not an expert on the Duratec setup but on my Xflow the colum was just touching the DS pump and I had the same symptoms. Easily fixed with a washer under the engine mount where it rests on the rubber....

 

 

 

Edited by - jonboylaw on 1 Sep 2011 15:02:18

[jonboylaw]

double post...

 

Edited by - jonboylaw on 1 Sep 2011 15:01:47

[2slo]

Mark,

 

my car (same as yours you may remember) had a similar vibration and it bugged me until I finally found it. Where the nosecone sits on the chassis just ahead of the upper dzuz fasteners the fibreglass was resonating against the chassis and causing the entire problem. A bit of carefully applied tape both sides and now it's fine. Worth checking.

 

Mark.

[spiderlane]

Thanks for the suggestions guys.

 

@2slo - yes I recall that you have virtually the same car. That's a very interesting suggestion, I hadn't thought of that. I'm struggling to visualise where you put the tape to stop the resonance - I don't suppose you have any pictures?

 

Cheers

Mark

[2slo]

Mark,

 

Unfortunately not with my car at present to take pics but I can do so tomorrow.

If you take the bonnet off, just under the front of where the leading edge of the bonnet rests is the upper dzuz fastener on the nosecone (the bonnet covers this when fitted) From the fastener point on the nosecone to where it curves downwards below the headlights the nosecone sits on the chassis here (and is secured both sides by the dzuz fasteners) This part of the nosecone was vibrating against the chassis on mine (both sides) and I suspect acting like a soundbox.

If you still can't picture it no probs I'll take a couple of pics and post them up tomorrow

Mark.

[paul abrahams]

I had a rattling vibration that increased with revs / speed which turned out to be the No.7 in the nosecone resonating against the mesh grill in turn vibrating against the nosecone. Made an awful racket and could be felt buzzing, so used some dense foam and insulation tape to cure.

[spiderlane]

@2slo - cheers, I know where you mean. I will have to check that out - what sort of tape did you use to stop the vibration?

 

@paul - ah, another good idea. I think I'll have to have the nosecone off and try it stationary at the various rev points which are worse than others - that would rule the nosecone in or out at least.

 

Cheers

Mark

[Pendennis]

Is all 4 cylinders firing correctly? a poorly combusting pot may cause stutter/vibration. Check/replace all spark plugs, a very small gap or no gap would also make it mishave in a such a manner

[spiderlane]

Hi Pendennis - thanks for the suggestion, I guess that's kind of what I had in mind. However the car is pretty new and has only done 4000 miles and recently been on the rolling road at T'N'R for a mapping session and they didn't report any misfiring (presumably that would have shown up?)

 

Also, it pulls cleanly from idle to the redline with no hesitation. Just the vibration/tizzing along the way.

 

However I can easily check the spark plugs - anyone know what the gap should be for this engine/plug combination? Is there a possibility that one of the coils could be partially faulty? Any way of checking?

 

Cheers

Mark

[Pendennis]

Mark, age and miles is not really relevant, you have a sympton that has just started. It could well pull like a train with a pinking sort of sympton.

 

Not totally sure what the gap should be, neither have I ever been anal about it, but should be around 1mm, maybe slightly less.

 

Could be a coil pack, can you not witness the plug spark without the thing firing?

 

 

 

Edited by - Pendennis on 1 Sep 2011 22:34:15

[2slo]

Mark,

I used electrical insulation tape. The heavy duty type, although not quite as thick as Caterham put on the rear of the nosecone to stop the bonnet chaffing. You can see both in the picture below. I originally said it was on the top of the chassis where the nosecone sits. I should, of course, have said the top of the sideskin. Anyway, picture of the offside below, n/s is the same idea. HTH.

Mark

http://i1103.photobucket.com/albums/g480/2slo1/015-1.jpg

[Angus]

Some suggestions:

 

Check that the coil cover is not vibrating against the mounting legs of the fuel rail.

I had this problem and it made a huge noise. I solved it by cutting clearance notches in the cover.

 

Check that the engine mounts are not touching the chassis. There is very little clearance, especially on the LHS. (Certainly an S3 Duratec, not sure about the SV).

 

Check the gearbox mount is not touching the chassis, and that there is clearance all around the gearbox. Any part of the gearbox / engine touching the chassis will cause vibration you describe.

 

Dont rule out the suspension - incorrectly set front suspension or poor wheel balance will cause unpleasant high frequency vibration through the steering wheel.

 

The general fit of the nose cone can be problematic. Check for general tightness and fit.

 

Also check the bonnet for fit. I cured rattles and vibration by sticking thin foam tape onto the mounting faces along the sides of the bonnet.

 

Hope you cure it !

 

Angus

 

[The Pikey]

Quoting spiderlane: 

However I can easily check the spark plugs - anyone know what the gap should be for this engine/plug combination? Cheers

Mark

 

The two Steves set my Duratec plugs at 37 thou so a shade less than 1mm.

 

Jason

[John Vine]

Hi Mark,

 

Is the water rail under the plenum aluminium or silicone hose? If it's aluminium, are the mounting brackets sound or has one (or both) fractured (a common fault, IME)? If there's a fracture, the broken stub could be in contact with the mounting lug, and this would generate a lot of vibration.

 

It's also worth checking that the steering column is not touching one of the primaries.

 

JV