ChrisC

Been trying to alter the sound for days :-(  

Steering column checked, no vibration upper or lower, and well clear of primaries.  

Engine/Gearbox and Silencer mounts are all standard, how do you mean allowing metal to metal contact?    It does have the wider gearbox tunnel for the Mazda box, but being a 6sp the gearbox mount is the standard type 9 mount, all be it on a removable mounting plate as per Mazda install.   The chassis is almost vibration free apart from 2500 rpm, where all hell breaks losses. 

Pedal box lid removed and the resonance still happens, also happens if brake and clutch pedal are pressed. 

Scuttle panel.  I will check. 

Hi Jim.   That has been my prime focus all weekend.  Initially the gap was smaller, I have doubled the gap to about 5mm but this made no difference to the resonance.   I didn't test with something between the gap, so that's another thing on my check list.    

Thanks Adam, I will check the plugs and snug. 

Hi Tom 

No FIA switch on mine :-( but thanks anyway.

As for yours, there is a small unused mounting tang inside the pedal box, at the front of the box, directly in line with the steering column as it passes through.  Mine touched the column and had to be bent out the way during IVA,  I wonder if yours is touching at some steering angles.  

Chris.

Would a stethoscope help?  The noise / vibration I am looking for is louder than the exhaust at 2500 rpm.  I thought a stethoscope amplifies the sound, won't that blow my ears off?

Hi All

I am looking for some pointers in trying to track down a very loud resonance at 2500 rpm.  It seems to come from under the dash behind the speedo, but obviously noise travels.   It's present stationary and moving, in any gear.  It's very pronounced, and can be clearly heard over 37db ear plugs.  It's really is spoiling the pleasure of driving the car, it's like having a rev limiter, because I don't want to go over the resonance point, and hate it as decelerating back through it.  

So far I have checked:

All the instruments, and the brackets holding them

The wiper tube, fixings and plates.

Bonnet and nose, happens with them off the car.

Gearbox touching the Chassis, there is a gap (not much, but a gap)

Column clears the exhaust, and the exhaust is not touching anything.

Touching the dash, outer column, steering lock, knee pads, coil cover, windscreen, heater, battery,  airbox, ECU, side skins, fuse cover, all to no effect.  

Basically, if I could touch it when the engine is running I have, yet the resonance exists.

So, where next to look?

Chris.

B37 is the tacho earth, G79 is the power (joined to G74 from the instrument fuse).   Check the earth continuity between B37 and the earth on the engine loom (two eyelets BY12 / 13 / 14  and  BY 15 / 48 / 49 / 51.   The two eyelets are separate earths in the engine loom, both need to be good.

I agree the occasional flick from the rev counter seems normal at tickover for a sigma, but I was able to greatly reduce the occurrence of this on my car by improving the earth connection between the looms and engine and chassis. 

From memory, I think the rev counter provides the power to the rest on the instruments, and also the ECU provides the engine speed signal to instruments.   The connections to the pressure sensor and the ECU are on the engine loom, and the instruments are on the chassis loom.     If you have a working oil pressure and temperature gauge now I would check the connection between the engine loom and chassis loom are clean and good (three plugs located above the gearbox), and the earth on the rev counter is good compared to the engine block (not just the chassis). 

Daniel's blog has some nice pictures of watts links http://www.caterhamr500.co.uk/2014/02/build-day-fourteen-decals-watts-link.html.   If your chassis has the mounting points its a bolt on upgrade from Caterham.

What rear suspension setup do you have.   If you have a dedion car, and you have radius arms, you will find there is an element of rear steering happening.    You can remove / reduce this with watts links.    Its my understanding racers perfer the radius arm setup because it improves turn in, but watts links are better for the road.

PM sent

Try cycling the hazard light switch a few times.

The design of the plug cover for the Duratec allows water to get between the cover and plastic cam cover, Unlike the sigma cover which covers the whole engine.  I guess you have to be careful when washing and getting caught in the rain without the opportunity to heat the water out.

You can always test that, get the car up to temperature.  Then switch off, wait a few seconds, then start again, you then have the lambda sensor warm up time (90 second I thing) before the ECU uses it.  Mine tended to be rich during that period.  Obviously with the lead it's very simple to check the running status of the lambda sensor. 

Yes, in 2014 I converted a 2011 125 to 150 against the trend.  When my car was new the 150 kit was the upgrade, so that's why I went for it.  I did hours of reading on here and knew the pit falls of the 150 kit.   The kit was fitted by a caterham specialist, but drove like a pig when I got it back.  Once I set it up according to my posts the car was transformed.   When I sold it, last year I had comments on how smooth it drove, better than 140 examples potential buyers had test driven at caterham.  I would say it drove better than my 360R, which is my only regret about the change.  

As for 1.03 vs 1.04, it all depends on the throttle site the ECU is using.  The ECU seems to idle at 0 throttle site, and wants to pull away at 1.  Set to low you will try and pull away when the ECU is trying to idle the engine and you get hesitation at low speed.   Too high and the idle is poor, and you get problems when you're off throttle.    Without the MBE lead you just can't tell.

More than happy to check and tweak 150s for anyone local, I still have the syncronometer, and MBE lead.

Have you got the basic right first?  

Balanced TB's, at the correct idle and the TPS set at 1.03v.   If not then that's where to start first. 

Mine needed checking/resetting about once a year.   

I use a 21mm crows foot, but my car is a metric car so maybe that's the difference.

For reference, my hunting was caused by a high idle screw.   It was ok after PBC and IVA, but has got worse since 500 miles.  I am guessing it's a combination of the engine freeing up and increasing the rpm into a range where the ECU gets confused.   Incidentally I didn't notice the rpm rise because the R spec tacho seems to read 1100 rpm regardless of the actual rpm below that figure seen on the MBE ECU, I.e 700 - 1100 all read 1100 on the tacho. I am sure this is because the needle is vertically pointing down at 1100 rpm.

Mine is a jäger at idle, I have tried the reset, and the TPS signal is fine, I have the lead to check.  I am concerned there is no adjustment in the TPS position, mine likes to sit at throttle position 2, when at idle, I am sure this should be 0.  All the sensors look fine, the "hunt" for a solution continues.

Access to an MBE lead would help to see the actual problem.  If you don't have a battery isolator, try an ECU reset (disconnect the battery of 1 min, or unplug the ECU), Then be careful not to press the accelerator before starting.

Careful of upgrading the calipers and disc.   I have the four pots on mine, and the pads rattle a lot.   The wheel bearings have no slack, and all the components are new (it's a new build).  Make sure you don't jump from the frying pan into the fire. 

Found mine needs a nip when hot to make it clamp tight enough to hold the exhaust level.    Until that point it droops. 

Mine is installed because the speedo sensor type and the sensor are miss matched.   PNP vs NPN.   I did a tone of investigation into this when my car failed IVA due to the speedo. 

Sorry miss posted - Resistor "SEE A" has a different purpose on my car - it's connected to the speedo.