Jump to content
SAU Community

Recommended Posts

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. :santa::D

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

  • Replies 81
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Posted Images

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

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.

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 :whistling:

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 by Haines
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?

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.

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

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.

  • 1 year later...

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!

  • 4 months later...
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?

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!

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • I can see between the water jacket and cyl 3 there wasn't a hard line of combustion gas. It certainly appears that the issue is coming from there. Yes, checked the tension. All at 100ft lbs where I set them 5 years ago. These blocks can crack but generally when they have been over bored. Mine is only 0.5mm oversize at 89.5mm. They break between cylinders around the 91mm mark. No sign of that with mine. My gut feeling is the head gasket lifted a while back when the studs stretched and i bandaided it by retorquing the studs. It's finally let go.
    • My Nismo 1.5 churps a bit on reverse turns when cold, but besides that feels like a stock diff.
    • Yes, but, I paid cash and I'm pretty sure the receipt was in the bin 10 minutes after I got home Note to self, keep all receipts
    • Bunnings would have just handed you your money back on that one!
    • So, version 4 intake is on its way I was looking at these a while ago but at around $200 or more it was a little pricey for something that might not work, but, I had it in my watch list, but, I got a message saying it was on special, and I had a code thingie to use, it eventually came in at $120 delivered, so BAM, BUY NOW.....LOL I'll need to have a look when it arrives but I feel it will "look" better than what I currently have, as it comes with a PCV fitting, so I will be able to get rid of the alloy pipe that goes to the throttle body with the PCV fitting  Well, that's what the voices in my head are telling me  Oh, and this happened today Yeap, it was a Trojan, and it was cheap, so I headed back to the hardware store and actually spent a little bit more on a heavy duty,  one that was actually recommended by a plumber mate, a Cyclone one with a fibreglass handle that is actually rated for clay The broken shovel will eventually be "modified" into a short handle shovel
×
×
  • Create New...