vibratey/metallic resonance on lifting off throttle-s1 111S
Discussion
Mine has being doing this for the last 50 miles or so. It doesn't seem to do it under load, but makes itself felt on lifting off, so I guess something is coming forward slightly and vibrating on something. It is quite a tinny noise, as if you put an empty bean tin on a loudspeaker type vibration.
It couldn't be anything mechanical could it? Oil is good and plenty of it.
The little electronics module with the foam packer could be a culprit as that moves very slightly, but I doubt I would be able to hear that with the engine in the way, then again it must be the chassis that is transmitting it because standing next to engine and blipping throttle you don't get much sense of anything, but again perhaps there needs to be some deceleration in the mix to make it happen.
Has anyone else had this and any clues to help me track it down, it is irritating and getting in the way of tuning my new Nitrons!
It couldn't be anything mechanical could it? Oil is good and plenty of it.
The little electronics module with the foam packer could be a culprit as that moves very slightly, but I doubt I would be able to hear that with the engine in the way, then again it must be the chassis that is transmitting it because standing next to engine and blipping throttle you don't get much sense of anything, but again perhaps there needs to be some deceleration in the mix to make it happen.
Has anyone else had this and any clues to help me track it down, it is irritating and getting in the way of tuning my new Nitrons!
it could be that, the garage would have had it off to fit the Nitrons, although it wasn't doing it for the first 300 miles or so after that then just started all of a sudden. Is there a good place to pull/push it to test (I can't get underneath!) I suppose that would make quite a dominant noise.
if anything, it isn't as noticeable when it is warming up (although that might be because until the thermostat has opened and temps stabilised I drive very steadily indeed so there isn't much lifting going on). This morning I even thought it was cured at first but it isn't, it is there everytime from above 30ish and then lift on - rrrrrrrzzzzz, back on power, just a nice clean engine note.
whip the under tray off and go for a short drive. This will rule out the diffuser being the cause.
Check the flexi section of the exhaust; it might be failing and this will make the exhaust drop a bit, potentially hitting the undertray.
Check/replace the sump to chassis engine mount. If you haven't done this then it's probably a bit tired by now, the engine could be rocking about a lot when you lift off. Fit the elise parts adjustable one; made a huge difference to mine.
I can't think of anything else off the top of my head. I doubt the garage would have had the under trays off to fit Nitrons; you don't need to go near the undertray to change dampers.
Check the flexi section of the exhaust; it might be failing and this will make the exhaust drop a bit, potentially hitting the undertray.
Check/replace the sump to chassis engine mount. If you haven't done this then it's probably a bit tired by now, the engine could be rocking about a lot when you lift off. Fit the elise parts adjustable one; made a huge difference to mine.
I can't think of anything else off the top of my head. I doubt the garage would have had the under trays off to fit Nitrons; you don't need to go near the undertray to change dampers.
thanks chaps, I think it is a resonance caused by the engine revs now, but definitely only on lift off. Its from 1500 to 2500, irrespective of gear and the moment you apply throttle, even just to hold speed or even a light application to stop losing speed so fast, it stops. So I am less convinced it is due to g-forces tipping something forward and causing a vibration now? So could it be something rattling in the throttle body? I suppose it could be exhaust related to, on the basis that an exhaust flow on throttle might be pushing whatever is rattling out of the way. Where is the flexi section? Manifold and heat shield area isn't looking too pretty.
zebedee said:
thanks chaps, I think it is a resonance caused by the engine revs now, but definitely only on lift off. Its from 1500 to 2500, irrespective of gear and the moment you apply throttle, even just to hold speed or even a light application to stop losing speed so fast, it stops. So I am less convinced it is due to g-forces tipping something forward and causing a vibration now? So could it be something rattling in the throttle body? I suppose it could be exhaust related to, on the basis that an exhaust flow on throttle might be pushing whatever is rattling out of the way. Where is the flexi section? Manifold and heat shield area isn't looking too pretty.
I think you have to concentrate on all the things that are affected by the torque reaction of lifting off, which has the effect of rocking the top of the engine forward towards the bulkhead, so if the heat shields are loose, or the lower engine mount is a bit worn, then there is plenty of scope for rattly trays and shields. Try to see if you can reproduce the sound by reversing away, which produces the same torque reaction,. if so With a VERY competent person behind the wheel, you could lean into the engine bay from the side and have a listen around whilst the driver eases his/her foot up and down on the clutch in reverse whilst holding the brake pedal down very firmly, handbrake on too.
The flexi section is underneath the engine. Take the undertray off and you will be able to see it. Could also be worn exhaust mounts allowing the system to move about a bit. Easy to change and cheap as well.
If you live close to me (west yorks) i'd be happy to help you get to the bottom of it.
If you live close to me (west yorks) i'd be happy to help you get to the bottom of it.
Very kind, I will have a good prod around the heat shield area, it seems most likely given the volume of it, thanks for the tip on the top of the engine shifting forward on lifting off, that will help focus my efforts. It is such a light tinny sound that it is probably something only just touching. It doesn't sound from what people are saying like it is anything mechanical anyway, so that is a relief.
Could be a broken spring on the clutch driven plate.
Only shows up when on overun and the load is reversed on the plate causing the spring to relax and rattle in its aperture.
is it more easy to replicate in the higher gears ? as the driven plate is subject to more load in the higher gears.
Only shows up when on overun and the load is reversed on the plate causing the spring to relax and rattle in its aperture.
is it more easy to replicate in the higher gears ? as the driven plate is subject to more load in the higher gears.
jfk01 said:
Could be a broken spring on the clutch driven plate.
Only shows up when on overun and the load is reversed on the plate causing the spring to relax and rattle in its aperture.
is it more easy to replicate in the higher gears ? as the driven plate is subject to more load in the higher gears.
This sounds quite likely actually...Only shows up when on overun and the load is reversed on the plate causing the spring to relax and rattle in its aperture.
is it more easy to replicate in the higher gears ? as the driven plate is subject to more load in the higher gears.
Yes only on overun and it sounds like a springy paper clippy sort of rattle. The moment you apply the slightest bit of throttle or indeed the clutch it stops. And yes, it probably is more obvious in the higher gears. Would it do it from cold though?
Any idea what that would cost to sort out/is my clutch going to pack in shortly if it is that?
The spring will probably just stay the same as it is now, neither getting better or worse in my opinion.
Used to get lots of broken springs on aircraft exhaust joints , they are very fickle things and can last forever or break with heat and vibration as and when they feel fit !
Used to locwire them in place on aircraft to stop them falling into the propellor.
To increase their longevity I used to run a bead of silicone along their length to dampen down resonance but obviously you can't do that on a clutch plate !
Used to get lots of broken springs on aircraft exhaust joints , they are very fickle things and can last forever or break with heat and vibration as and when they feel fit !
Used to locwire them in place on aircraft to stop them falling into the propellor.
To increase their longevity I used to run a bead of silicone along their length to dampen down resonance but obviously you can't do that on a clutch plate !
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