Hi Can anyone shed some light on this. Its just started happening in the last month or so. Not a major problem but i would like to get it sorted.
I have a 2007 exige s with cn 270 kit on (done 5000 miles ago). 11000miles on the clock.
When i first pull away or roll out of a junction in say 2nd gear and the engine labours slightly there is a rattly noise coming from the engine bay.It doesnt do it at any other revs or on tickover just when the engine is loaded from low revs. My first thoughts were that it was a loose undertray or exhaust rattle or something but now i know its not. It is noisier on a morning when the engine is cold but doesnt do it when it has been raining and the engine is wet for a few minutes untill the aux belt squeels a bit then it is present. Weird. Anyway i have removed the aux belt (which is like new)and ran the car up the street and back and the noise is gone so it is something to do with one of the aux pulleys including the supercharger. There doesnt seem to be any play or notchieness on any of these pullys so i am a bit lost so was wondering if it could be the supercharger itself. It does seem a little stiff but im guessing this is normal. My next step will be to fit a new belt off a N/A car to eliminate the supercharger and see what results i get.
Have any of you guys heard of noisy superchargers on these cars? I thought if the bearing was worn it would just rattle all of the time?
Anyway thanks for any advice in advance.
Scott.
Check your bypass valve actuator to see if it is operating properly at idle from vacuum when you blip the throttle…
MMMmmm interesting point. I have noticed the car does hesitate a little when i blip the throttle from tickover (like its got a flat spot)also it takes a seccond or two for the revs to return back to idle. How do i check the bypass valve actuator is operating properly? I guess its attached to the supercharger somewhere?
Thanks again.
Check the supercharger. When you turn the pulley back and forth as far as you can, do you get a single clunk? There is a plastic bush between the pulley and the supercharger gears internally that has been know to fail.
[quote=scottydog]MMMmmm interesting point. I have noticed the car does hesitate a little when i blip the throttle from tickover (like its got a flat spot)also it takes a seccond or two for the revs to return back to idle. How do i check the bypass valve actuator is operating properly? I guess its attached to the supercharger somewhere?
Thanks again. [/quote]
It’s on the side closest to te firewall, reach over and feel if the control lever is moving when the throttle is blipped. If it is not moving then it needs to be replaced…
They are available on their own, we usually replace them when we do a supercharger rebuild (bearings in the nose, replace butterfly throttle plate at other end which wears and replace bypass valve actuator). I haven’t found them available anywhere other than Lotus yet.
You can get them directly from Magnuson 805.642.8833 if it is the problem.
Just an update.
I have tried to fit a belt off a NA Exige with air con but can’t get it to work. The alternator must be positioned higher on the NA version (about where the supercharger pulley is). When I try to fit the belt on, the back of the belt fouls on the supercharger pulley so this is a no go I’m afraid.
I have checked the valve on the supercharger and it is working fine when I blip the throttle.
I have checked for any free play on the supercharger pully and there isn’t any at all either rotationally or in and out.
There doesn’t seem to be any play or roughness to the two idler pulleys, alternator, a/c pully and water pump pulleys.
My only thought is that it can be the tensioner shock itself but I really need an assistant to check under the car while I simulate the rattle by slowly letting the clutch out whilst in gear with the handbrake on (this Puts load on the engine whilst at low revs and highlights the rattle)
My local lotus dealer says he has seen alternator brackets fracture and crack and to check this. All looks good there also.
The car is going in for service next week so I will see if they spot anything that I have missed.
Getting annoyed now. Grrrr.
Any more suggestions welcome. Thanks Scott.
Dude if you are knowingly trying to install an NA belt on your engine put down the tools and step away from the car…