Confirm My Exhaust Restriction :(

[666DAN]

Just so you know I have no problems with power or holding boost.The only reason I changed the split pipe to bellmouth is as an experiment because I`m a hopeless fiddler.But think about it,when the wastegate opens the only time the gases are not going in the same direction is when the flap STARTS to open.Thats when the gases are going sideways but only till the flap opens further then all gases are going in the same direction.Plus the Fact that the standard or high flow turbo is quite small in the turbine outlet area,putting a restriction in the way via a divider is causing more problems than it solves.Gas wants to expand when it is hot so why would you stop it by keeping it in a 2" pipe? Don`t forget,the wastegate opens after boost has been reached so the turbine will boost faster with less restriction via a bellmouth.Realistically,the turbine dump pipe on a high flow should be a 4" pipe to ,say,the rear side of the cat.Now that would be efficient at 20lbs of boost.

I remember a published experiment years ago involving a V8 holden and going from twin pipes to a single.The single gained some 15kws due to all the gases in the same pipe speeding up the gas flow.Just a thought.

That's exactly right, it doesn't make a shred of sense that a split with a 2" exhaust side would flow as much as a full 3" bellmouth with a turbo running decent boost. I stand by my opinion they're good for stock but not for modified highflow

[VB-]

i havent read every post in detail but scanned most of it, have you tried putting a spring on the wastegate actuator? my money would be on that at this point

doubt it would be the dump pipe, it shouldnt be too big of a restriction just lookin at it from a design point of view, but beyond that i've only ever heard good things from CES

[skylinecouple]

Exactly VB.I personally don`t think it is the exhaust.I think boost control.Gain on EBC should be turned up till spiking occurs then turn down a notch.This will allow the EBC to keep the w/gate closed up the top end.Worked for me anyhow.

[666DAN]

Problem Fixed!!!!!

The Bellmouth has made a difference, putting preload on the actuator is now actually working and not just blowing open.

I've got a solid 15psi now

....no need for the Profec anymore though

[BAMR33]

Good to see, you may have found the fault with all split dump pipes.

Edited July 31, 2007 by BAMR33

[Haines]

If it is the Problem with all split dumps would this be solved by cutting the wategate pipe into a screamer pipe ??

and how do you put preload on the actuator

do you add a spring to the side ???

Edited July 31, 2007 by Haines

[InterCooL]

Problem Fixed!!!!!

The Bellmouth has made a difference, putting preload on the actuator is now actually working and not just blowing open

sorry i'm still unsure, was the problem the preload on the actuator, or the bellmouth?

[666DAN]

sorry i'm still unsure, was the problem the preload on the actuator, or the bellmouth?

My actuator is an adjustable, set at 15psi with the split dump it wouldn't hold 15psi to save it's life (same for stock actuator and RB20 actuator...to be expected) adding more pre-load was just seeing a bigger psi peak which still dropped off to 11psi.

With the bellmouth fitted, when pre-loaded to 15psi it holds, yey!

Moral of the story, with the turbo on my car the split dump didn't seem to be beneficial at all and led to boost drop-off...I suspect low pressure on the wastegate was helping it get pulled open by the exhaust gas up against it.

[Haines]

If the main exhaust gases are flowing past the smaller split pipes entrance at a high velocity could that in turn create a vacuum effect and try and pull the wastegate flap open

[666DAN]

If the main exhaust gases are flowing past the smaller split pipes entrance at a high velocity could that in turn create a vacuum effect and try and pull the wastegate flap open

Yeah, like a paint-brush...that's the theory I'm going with

[OVADRV]

so after all this what were the results on the dyno?

[666DAN]

so after all this what were the results on the dyno?

Give me a chance, only just swapped the dump over last night It's booked in for Thursday next week

Dan

[skylinecouple]

And i can confirm my new bellmouth is so much better in the top end.I just know when I get it tuned It`ll be at least 10kws up over the old figure.Have to tell you though,mine is custom made by me as I cut up the pipe at the flange and enlarged it to at least a 4" diameter.I cannot see how there could be any resistance to exhaust flow now.

[Haines]

External gate for me

Id say by reading all of this that would be the best option

ill have to mod the split dump to take the external gate but should be possible

[operationsideways]

So how did you go on the dyno today Dan??

[666DAN]

So how did you go on the dyno today Dan??

They "forgot" I was going down there, booked in for 2pm today though

[666DAN]

Well there you go...I've still got some boost trailing off, not as bad as before....end result though, same power output for more psi....so I'm over it!!!! EVO7 please!

[666DAN]

Back from the past....more to add.

The knock sensor on my car is reading an alarming 3.4v even when the car isn't running. Normally anything over 3v makes the ECU drop timing, so the car has been running in a sort of "limp mode" for ages.

I've fiddled with the sensor and it now puts out a solid 2.0v (what it should at idle, and now the car feels a lot more responsive...back to the dyno we go.

bloody cars!

[Get EPIC]

Back from the past....more to add.

The knock sensor on my car is reading an alarming 3.4v even when the car isn't running. Normally anything over 3v makes the ECU drop timing, so the car has been running in a sort of "limp mode" for ages.

I've fiddled with the sensor and it now puts out a solid 2.0v (what it should at idle, and now the car feels a lot more responsive...back to the dyno we go.

bloody cars!

Well,How did it go?

[DECIM8]

Good question!! I also had boost drop have now fitted a Bellmouth (also had ces dump pipe which was awesome on the stocker) I honestly think its actually the turbo.

Wednesday im due for a tune I hope... Dont know if it holds boost better because boost controller is totally wild and dont have enough space or balls to set it in todays police climate. So we shall wait and see!