Who's Supercharger Makes A Blow Off Sound?

[A.J]

was just wondering if any of the s/c guys can hear the blowoff sound when shifting? cos mine has been making that nice 'hisssss' lately and i discovered it was because the old spring on the bypass (not the uprated one) had come away- but iv been told its not good for the throttle/sc to leave it like that (??)... no matter how much i like the sound.

....btw the pull hasnt been that much worse with just the one spring.

[Unregistered_User]

Yes, mine has been making that sound as well. Need the uprated spring asap tbh.

Still got a nasty rattle on start up as well, so hoping someone will be able to diagnose it this weekend for me.

Jamie

[aido]

@ Jamie - check the bracket under the supercharger - probable that the metal bar to the back of the engine has snapped - common problem mate :)

AJ - were you running both springs - the old and the new together? I thought that could put too much stress on the servo - saying that people with both always said it felt better!

[bigal]

Yup mine does its loud too because i have an induction kit fitted

Alex

[Unregistered_User]

Cheers fella, I'll nip and check now. Also, when the spring starts to become a problem, does it appear slack or anything?

Jamie

[aido]

I think it just sticks open mate, best thing is to check if the bypass is opening and closing freely - or should I say opening freely and snapping shut :)

If it is the cradle that is snapped you can just remove the bolt that holds it to the rear of the engine and remove that part - it's just overengineered but has a fracture point on the cradle itself - at a guess is your noise shield on the bottom of the bonnet etched away where the supercharger pulley is located too?

[Unregistered_User]

Not too sure what you mean about the last bit matey

[aido]

On the underside of the bonnet there's a black foam sheet which is to help keep the noise down outside the car - on some IS's with the supercharger the engine seems to sit a little higher and due to this the pulley on the supercharger eats the foam away when the engine is under load - the majority of ones that I saw that had the bracket snap also eat the foam away you see mate :)

[Unregistered_User]

I had a look before you posted and yes, it appears to have chewed away a tiny bit, revealing the yellow innards lol ;)

Can't see a crack in the cradle fella; Is it usually visible?

Jamie

[aido]

Not so much visible when the engine is off, if you turn the engine on you'll usually see the rod towards the rear vibrating if that is what has gone, and if you try to move it you'll see it's no longer attached to the cradle - if you can't see it possibly it is something else, and you're gonna be at the right place to find out tomorrow :)

[Unregistered_User]

if you can't see it possibly it is something else, and you're gonna be at the right place to find out tomorrow

Can't tell you how comforting that is haha :D

J

[Moffet]

I have the rattle still too. Hoping someone can take a look tomorrow

[yemgi]

no worries, there will be a lot of people to take a look :)

[RX-Men-8]

With the old spring, the bypass may not open quick enough when lifting the throttle. This makes the charger run into a pressure buildup, making the belt slip. Inside the cabin this may sound as a blowoff sound, at least I thought so until I heard a camera recording of me driving by with a squeaking belt.

I installed a BOV since which sounds nice and releases some stress on the supercharger when lifting the throttle ;)

Cheers,

RX-Men-8

[A.J]

AJ - were you running both springs - the old and the new together? I thought that could put too much stress on the servo - saying that people with both always said it felt better!

yes now its got both- infact iv even put the uprated spring in the second 'notch' (closer to the original spring) – so that holds it even more tightly closed! and its not blowing off whatsoever which makes the accelleration feels very solid.

...but as you say this could be worse?? - will probably put the uprated one back to normal and keep the original in (and see about removing it later)- but will be interesting to see how others have it.....

[Fin_IS_200]

My spring snapped few days ago and it sounded like one of the boost pipes were off.

[Chris.S]

Mine used to do it if i accelerated really hard in 1st

[cho]

Mine makes that noise, I just had my s/c fitted a few weeks back and it is brand new and bypass valve snaps shut fine. Could it be something else, I have to say thought that at times I seem to get a lag before the charger kicks in when in 1st any ideas anyone?

[Unregistered_User]

The lag could be the spark plugs (IK20) and not the uprated ones which are best suited to the supercharger (IK22) - I'll be getting some of these at some point.

The rattle could be down to the belt being loose - Rob and Barry fixed my in a couple of minutes when they witnessed the belt on the s'charger rattling about due to being too loose.

Check this ;)

Jamie

[RX-Men-8]

Mine makes that noise, I just had my s/c fitted a few weeks back and it is brand new and bypass valve snaps shut fine. Could it be something else, I have to say thought that at times I seem to get a lag before the charger kicks in when in 1st any ideas anyone?

The lag - if it is below 3000 rpm, is probably due to running lean going from no boost to boost, until the ECU corrects it (well, almost) reading the O2 sensors at the exhaust manifold. The (non-boost-aware) closed loop fuelling control is just trying to follow the (crude) mechanical boost control. It can be made better with custom fuel mapping.

[Rob]

With the old spring, the bypass may not OPEN quick enough when lifting the throttle. This makes the charger run into a pressure buildup, making the belt slip. Inside the cabin this may sound as a blowoff sound, at least I thought so until I heard a camera recording of me driving by with a squeaking belt.

I installed a BOV since which sounds nice and releases some stress on the supercharger when lifting the throttle ;)

Cheers,

RX-Men-8

A small edit.....

[RX-Men-8]

of course :)