*MAXXD* Ollie's Nissan 200SX S14a

[meatball westwood]

is it just the air going back through the turbo blades that makes the chatter noise?

[LeeWestwood]

meatball westwood;23931 Wrote:is it just the air going back through the turbo blades that makes the chatter noise?

Yeah come on barrels, enlighten us vtec boys as to how a turbo works!!. I thought chatter came from a wastegate? :dearme:

[Roger_Sausage]

Yup....once the blow off valve is removed, there's nowhere for the compressed air to go once the throttle closes, so it comes out back through the turbo. If you're accelerating at full-chat, then the turbo can be doing anything up to 100,000 RPM, so when the throttle butterfly closes there is still some residual boost pressure created that is now sandwiched between the turbo, and plenum. At this stage, the blow-off valve would see this excess pressure build up and vent it out (either to atmosphere or back in to the inlet tract). Without a blow off this pressure builds up to the point where it has enough force to travel backwards through the now-slowing compressor and turbine blades. The noise is the air being disturbed by the force of travelling against the direction of the turbo. That's why the over-fuelling happens, because the AFM just sees a load more air so dumps fuel in to the manifold.

The wastgate doesn't chatter, it either opens or closes, it's purely a device to bleed of excess boost from the turbo. That's what electronic boost controllers do, they just control when the wastegate opens. Usually the wastegate sees a set pressure and opens up to relieve it. What the boost controller does is fit a solenoid in-line with this, and bleeds off the pressure that would normally activate the wastegate, preventing it opening before the desired boost level is met. Once the controller gets to it's determined value it stops bleeding off the pressure and the wastegate opens. This is why uprated wastegates are required are cars running high boost, because once at a certain level, despite the boost controller solenoid bleeding off the signal to the wastegate, the pressure is simply too much and forces it off it's seat anyway. S14a's usually need an uprated actuator and wastegate at around 1.2 bar.

[OllieWestwood]

eightsmokinbarrels;23930 Wrote:*deep breath* It's not the WAAASTEGAAAAAATE!

Ahh....that's better.

Have you done the "pidgeon mod" then Oll, i.e. removed the recirc?? It'll overfuel quite a bit now, and if you've still got your front cat in place it's gonna melt fairly quickly because of all the unburnt fuel igniting inside it.

Ive not done the pidgeon mod mate no, all the noise has come from the airfilter (Compressor surge meatball )

i fancy doing the pidgeon mod...will it make it louder?

As for the front cat as soon as the fuel pump is ordered that will be next.

[Roger_Sausage]

Yeah it gets much louder mate. If you've not done the mod then what's happening at the minute is just low pressure escaping and the recirc is handling the rest. By removing the recirc what will happen is that the full .7 bar of boost will come out through the filter and the sound will be longer and louder.

People could hear me coming long before they could see me!

[OllieWestwood]

wow!

Its loud now!

Do you know what size bungs are needed to block off the pipes? and where i can get them from?

Im off till wednesday so might have a go!

[Roger_Sausage]

27mm and 30mm I think, I got mine from Apex but http://www.danodesign.com do them too. Some people just use broom handles but they don't seal. I ended up using a gob of RTV on my bungs too for the same reason.

Just remember that if you do it for too long on the standard front pipe it will damage the cat. Oh, and it will flame now too, try accelerating to about 3000rpm, come of the throttle and than just *tap* it gently and *bang*

[OllieWestwood]

Apex do 25mm and 32mm?

Dano dont exist anymore!

Any idea where i can get some others from?

[Roger_Sausage]

Yeah the main Apex one is slightly bigger and an absolute nightmare to get in. It took a long session with a cup of boiling water and a rubber hammer to get mine in.

Have you tried SRB Power or Jez at H-Dev? Just try the traders on SXOC, someone's bound to do them. Either that or just get a couple machined up, it won't be much.

[olstar]

sounded good last night dude...

the modding has commenced!