Running in ailments

[Jonathan Kay]

I am still bothered by the asymmetrical nature of the box.

I can't see a way to move the gearbox any further to the right. The slots in the gearbox/chassis mounts run longitudinally, so no real way to push the unit to the RHS. 

It's an asymmetric design, short side to the left. I am rather hopeful that the work I've done tonight will cure the vibration. i will report back after a test drive tomorrow. 

Hope that fixes it. It will leave a lot of questions:

1. Why yours and not others?
2. When did the ability to adjust in yaw disappear?
3. Would it be easy to restore it? By fettling the chassis or mounts? Or otherwise?
4. Would a single spacer or replacement mount with two holes be any better than two stacks of washers for the adjustment in pitch? The latter does allow adjustment in roll.

Jonathan

[patneale]

Sorry to hear of your speedo problems. Guess the instruments are still the Caerbont Caterham Branded instruments. I had this problem and you need to do 2 things. 1)  check what the gearing is in top for your car with Caterham  i.e. 22 MPH per 1000 revs. 2) borrow a Tomtom or other GPS and note down what your speedo is showing against the GPS and also what revs. as both instruments could be wrong.  If you find that you are doing 50 when Tomtom is showing 45  you need to adjust the speedo. To do this at home just put car on axle stands with rear wheels off the ground. With ignition off. remove the speedo and obviously pull off the wiring connector block. Examine the back of the speedo and there should be a rubber grommet  behind which there should be a slot for a small "jewellers" size screwdriver. Carefully ease down the  connector block and there should be enough slack to reconnect the speedo below the dashboard where you can get to the adjustment slot and see the speed at the same time.

Then keep the revs steady at 50 MPH in top gear and turn screwdriver to get the speedo to show 45 MPH.. Providing you kept the revs steady you should find  that 50 is correct with the TOMTOM.  However is the Rev counter correct for your new 50?  You can calculate what it should be at the new 50 from the revs Caterham have provided per 1000 revs. If the revs are wrong from your base MPH per 1000 revs then you will have to do the same exercise with the Revcounter.

It will vital to chock up the front wheels to prevent the car moving when doing this as you don't want the car to fall off the axle stands with the wheels doing 50 MPH !!!.

Don't worry if you find that the speedo readings are slightly out at set multiples of 1000 revs you always want the speedo to be a little fast say 68 correct at an indicated 70 MPH so you don't get caught on cameras. My speed shows correct reading and revs at about 40 ,but slowly shows higher speeds against actual the faster you go.    Remember Caterham has a great range of gearing combinations due to wheel sizes and axle ratios so one speedo does all will always need adjustment depending on the model.. Mine has claimed top speed of 122, but speedo goes to 160 to allow for R500's and the latest 310 BHP models.

[John Vine]

But surely he has a programmable speedo?  If so, calibrating it is simply a matter of entering the correct 6-digit code to match the number of pulses/mile generated by the sender.  Once that's done, the accuracy of the readings (speed and/or trip) can be refined by small changes to the code.

JV

[ScottR400D]

Yes, I'd have thought it was the electronic one with the code I putted. 

Mine was 10% fast against my satnav, on delivery. I had some details that told you how to access the code and adjust it. I adjusted it by 7% to leave the speedo about 3% fast.

 

[Mucus72]

Yep, adjusted. 30 second job with a code. Just used the one for my tyre size from Johns link. May elect to adjust further after I've checked against sat nav at steady speed. 

[Clousta]

 

Speedo problems,

then a gearbox that doesn't fit,

and then:

"...although the image in the guide shows a flange that sticks out of the bottom of the box and potentially this rests on the mount. My gearbox does not have this."

leads me to ask if you have correct gearbox?

Do you have the gearbox serial number/format of the serial number so that you can check that you have the correct gearbox and not variant of the gearbox destined for another part of the world?

a one off wrong variant would explain why it appears that only you have a problem.

It might be unlikely but worth checking.

 

[ScottR400D]

From what I know the speedo calibration is a very common issue. It's easily sorted once you know how but not mentioned in the handbook or manual. 

I don't think the gearbox is a one off issue either. 

[Mucus72]

I've driven 450 miles this weekend whilst away in Yorkshire. Before I left I'd raised the gearbox on 2-3mm thick spacers and I do believe that this has reduced the vibrations a little. However, the problem is not fixed. The vibrations are really annoying and I still believe the clearance tolerances on the Mazda 5 speed are too tight. I have spoken to a few others who describe similar issues. If you don't know what Caterhams are supposed to be like then my additional assumption is that there are many folk who think that this is normal. I beg to differ and need to get to the bottom of the issue.  

[pugwash]

I drove Caterhams 420 demonstrator on Friday and it had no more "vibration" than my supersport.  Does sound like something is amiss. Can you get it to CC to get it up on a ramp and do a direct comparison with another?

[ScottR400D]

I had a close look at my 6 speed whilst it was up on stands for a spanner check last week. It is adjustable laterally, a little and I remember taking quite a bit of time getting it exactly central. It's well clear of any rails; there is a bulge, forward on the left side of the box that is very close to the insulation, possibly touching, but I can't say I've noticed any undue vibration. 

Is your box clear of the insulation? Is the vibration still high frequency? 

[revilla]

Not sure how well it will work on the whole body / chassis unit but I've got an engine stethoscope you can borrow to give it a try if you want? Works well for finding engine vibration noises and vibrations, there's a long metal rod you touch to the part you want to listen to. You may find you can hear the buzzing getting louder as you get closer if you are lucky. Worth a try?

[Mucus72]

@Lee - I am thinking that I will need to adjust laterally, fabricate some soft wood levers (Jim123 has done this previously, so I'm not a lone nut), loosen gearbox and engine mounts and try and shift it right a little.

THe box does touch the insulation. Much more than touch, it looks like its fully compressing the insulation foam (pressing v hard). The vibrations are high frequency.

@Andrew - yes please Dr.Revill, Caterham consultant... ;) Even better if you had a spare hour (tea and biscuits provided)

[revilla]

Just back from spending a pleasant couple of hours with Marcus in his garage looking at the vibration issue and promised I would write up what we found. However I have just noticed in the last post above I was promised biscuits with my tea so I'm feeling a little hard done by all of a sudden! Anyway ...

With the engine at idle, there's quite a lot of vibration to be felt throughout the chassis. It is quite noticeable through the seats, body panels and the steering wheel. Much more so than in my car. I should qualify all of this by saying that all of my experience is with K Series so when I compare things with my car I'm not comparing like for l don't know how much of the difference is just K vs. Duratec.

The gearbox is now spaced away from the chassis. There's not a lot of clearance in there but if you press a finger tip in against the points where the gearbox comes close to chassis rails with it running you can feel relative movement between the box and chassis as the engine vibrates, so there is some clearance and I don't think there's much vibration being transmitted through the points where it contacts the heat shielding. It also feels as though the amount of vibration to be felt in the gearbox at that point is a lot less than the vibration you can feel in the chassis, so I don't think gearbox to chassis contact is the primary source of the bodywork vibrations.

The engine mounts feel very firm. When blipping the throttle the whole car can be seen to rock slightly from the torque reaction but it's hard to make out any relative movement of the engine relative to the chassis. However we removed the engine mounting arm to rubber bolts and checked their length and they don't appear to be too long. With these bolts slackened right off the levels of vibration in the bodywork were still about the same, and with the bolts tightened again, using a stethoscope against the central engine mounting rubber bolt and then against the mount to chassis bolts it was clear the mounts were absorbing a lot of the vibrations so appear to be working correctly and are not being clamped out by the central bolt grounding on the bottom plate or anything similar.

There are no other obvious points of contact between the power train and the chassis. The steering column is clear of the exhaust primaries and the exhaust primaries are well clear of the bodywork through the exit hole. There is some light contact between the bell housing and the heat shielding towards the front of the tunnel but I don't think there is firm pressure transmitting engine vibration to the bodywork.

The one thing that really did strike me was just how much vibration is actually being produced by the engine. Certainly comparing it to a K Series, if you put your hand on top of the engine when it is running there is a lot more buzzing vibration. The engine feels very harsh and has actually vibrated the cam cover bolts out as mentioned by Marcus earlier. In addition, if you slowly open the throttle, somewhere around about 2500-3000rpm there is a resonant knocking rattle sound. It is not coming from external engine covers as we tried putting out hands on all the external bits that could be rattling without any effect. It does sound as though it is coming from inside the engine. It's a heavier more mechanical sound that you would get from something external resonating, but it is only really obvious over a narrow RPM band. Using an engine stethoscope the sound appeared to be coming from around the rear end of the inlet camshaft but it wasn't anything like normal cam or lifter noise. It's also not coming from the injectors. It's the kind of noise you might expect if the cam was loose in its bearings; I'm not trying to suggest that it, just to describe the noise a little better.

As I said earlier I have no idea to what extent a Duratec would normally feel harsher than a K series and whether the noises we were hearing were common to Duratec engines but the vibration levels from the engine were such that if it were a K Series I would be concerned that it was distinctly unhealthy. I honestly think that the main reason that there is a lot of engine vibration being transmitted to the chassis is simply because there is a lot of engine vibration.

It almost feels as though there is a problem with engine balancing.

Marcus, as we discussed earlier I think the best course of action now would be to take the car back to the dealer for them to investigate under warranty. In the meantime I would try to familiarise yourself with other 420s and Duratecs in general to try to get a feel for how much of a difference there is between the level of vibrations in your car and others of a similar specification. Tese things are so subjective and difficult to describe that I think the only way you will know if your car is different to others is through direct personal experience of a number of cars for comparison.

[7 wonders of the world]

My K and Duratecs were both very smooth, though I do balance mine to a fine tolerance,

Has the mapping been checked?, as this could be inducing vibrations,

[revilla]

One thing was puzzling me after I left last night Marcus - the frequency of the vibration you are getting. Even at idle, it's quite a high frequency buzzing. If the idle speed of the engine is around 900rpm that's around 15 crank revolutions per second. Just from the feel of it I would say the vibration is higher frequency than 15hz even at idle. I may be wrong and it may be at crank frequency but it's certainly not at cam frequency.

The only way I can see of getting a strong higher frequency vibration from the engine are:

1. Something that happens multiple times per revolution.
2. Something that is turning faster than the crank.

If it was vibrating at the frequency of one per firing stroke that would be around 30hz at idle, so that's a possibility but then makes it less likely to be balance related.

The only obvious things that rotate significantly faster than the crank are the pumps and alternator that are belt driven at the front of the engine. I'm not sure how the belts are arranged on a Duratec - does the alternator belt drive other things too? Just wondering if it is possible to remove the alternator belt without losing dry sump pumps and the like just to rule out it being a real problem with balance or bearings in the alternator? Even if not, can you slip the belt off and spin the alternator by hand to see if it feels normal? Any roughness or play in the bearings would be worry, as would any tendency to rotate back to the same position each time you let go. Possibly a very long shot, but thought worth mentioning.

[Mucus72]

It's one belt that drives all, but v easy to slacken the tensioner and slip the belt off to hand crank the alternator to check for what you are thinking here. I'm working from home today and will do that at lunch time and report back Andrew. Thanks!

[Mucus72]

@seven wonders - I have heard of other cars with comments on blatchat where the wrong map was used and Caterham needed to re-flash the ECU. But these were cases of really rough running, and mine doesn't. It is just really severe vibration all of the time. Is this what you mean by mapping or do you mean a map sensor issue. Apologies but I'm not very savvy with this kind of thing...

[Steve_K]

This may be a red herring but doesn't the Duratec use internal balance shafts to counteract the 4 cylinder engine's intrinsic secondary out of balance forces? The shafts run at double crankshaft speed which might explain the highish frequency observed. Maybe the engine was supplied with the timing for the shafts out of kilter?

Steve

[revilla]

That was precisely something I was talking to Marcus about last night. The problem was, neither of us knew if the Duratec used balancer shafts or not. If it does, I would think you might just be onto something.

[Steve_K]

I've just done some checking on Google. While the 2.3 Duratec seems to have balancers, it looks like the 2.0 doesn't although I didn't find anything definitive, just an absence of info. Sorry.

Steve

[Mucus72]

I googled last night and its rather difficult to work out which engines are actually the Duratec ones in our cars. Does anyone else know definitively whether ours have balancer shafts please? 

[7 wonders of the world]

2.3 were shafted, but not the 2.0 units, though in Caterham application the shafts in the 2.3 are deleted making them similar to the 2.3 engine used in the Ranger.

 

The mapping I referred too is when the idle data is 'just' unstable enough to set up a vibration and the map isn't fine enough to give a pure idle.

Natutally alternators will be balanced when built too so could easily cause this

Is the vibration still present when you hold the clutch in?

[Mucus72]

I will check the alternator. Will have to be tomorrow, work got out of control today and I didn't find spare time. 

Yes, the vibration is identical irrespective of clutch position. 

[revilla]

Vibration is also present at all RPM, both in neutral and when out on the road too.

[7 wonders of the world]

Just thinking assuming the exhaust only has a single mount is this a rigid or rubber mount at the rear of the silencer.

There aren't many places where the powertrain comes into contact with the chassis - this is one though, might there be some tension in the exhaust system?