Call me lazy if you like. https://www.nopistons.com/forums/pub...IR#>/blush.png



Would like to hear your opinions on this topic. >



http://ausrotary.dntinternet.com/forums/vi...ic.php?t=101806

Not a good idea...

Yea not a good idea , a good responsive turbo will boost creep. If the wastegate pipes have a good collector exhaust interference will not be a problem .

Im curious, what were the results? Im not totally convinced it will make high boost on 1 rotor with the WG open.

Thats stupid as hell!



If you have a divided turbine housing then the air has to go into the turbo and come backwards down the other runner to bypass the turbine. Even if there is no boost creep which i think there would be, its still stupid.



I dont know that it would make high boost on one rotar, but if it did it would probably be on the rear rotar and thats bad.

I dont know though, i dont really think it would, the exhaust pressure btwn the rear rotar and turbo would be higher but that just means alittle less new air would enter the rear combustion chamber (a very very small amount less). It would just cause boost creep is all that i can see, and that may not be bad either, but that set up just doesnt make any sense. Intake manifold pressure is equal on both sides, so boost pressure is the same on both rotars. Its still stupid though, if he wants to do it that way he needs to have 2 small wastegates.

Nospig, I expect it to either work & hold boost @ the desired 20psi or will Creep. Will be 1 or the other I imagine. Another possibility I think might happen is boost might come on softer/slower.



Ronin, I havent put it on the dyno yet. Booked for this time next week. Will be sure to post results.



WankelTII, I dont think you understand how a turbo & wastegate work together.



More boost to rear rotor simply because that rotors exhaust runner doesnt bypass the turbine? Dude, Theres no intake restriction to the rear rotor so it will recieve the same intake pressure as the front.





Ahha, boost creep. https://www.nopistons.com/forums/pub...R#>/tongue.png

Its a completely divided set up, (i assume that means the turbine housing is divided too) air from the rear rotar cannot get to the wastegate without actually going into the turbine housing and coming back down the front rotar's exhaust runner. I dont think the air can or will do that, so the creep wont just be a small amount.



Do you understand how wastegates work?!?! If the air cant get around the turbine then it will continue to spin the turbine wheel.



Someone else said there would be high boost on one rotar, i realized in a matter of 3 sentences that wasnt possible, i just didnt go back and take out my thought process. But your right intake pressure is intake pressure, ok duh.



Even if it works, I still think its a ridiculous way to do it. Its got to cause some wierd stress on the bearings or something to have way more exhaust pressure on one rotar. Why not just do it the normal way, or with 2 smaller wastegates? Neither are difficult, this just looks like you got lazy or something.

A properly sized wastegate anywhere before the turbine will technically work.



Obviously, dont use a little 28mm wastegate on this setup. I would use the largest you can find. You have to remember that a wastegates function is to equalize the pressure before and after the turbine. The more pressure you can release, the more control you have (larger is always better in theis case).



Its not a good design, but it should do what you need it to, but you may have some creeping issues depending on the rest of your system.

Yes, but how does the pressure get equalized if the only way for it to escape the rear exhaust runner is to go through the turbo? There is undoubtedly going to be high pressure between the rear rotar and the turbine housing, I guess since the turbine is rather large and the front exhaust runner could possibly get close to atmospheric pressure when the wastegate is fully open, the creep might stop somewhere fairly reasonable, but i am willing to bet that the boost will be more than the wastegate spring was rated for.

I think everyone is shooting down the idea before it even gets tested.



I have some theories about that setup and what it will do. Some positive, some negative that I think I will hold on to until it gets dyno'ed.

Wankel, there is no way gasses from the rear runner would, should or even could run in 1 side of the turbine & back out the ther side to the gate. haha makes me laugh just thinking about it.

Besides the fact theres exhaust pressure un the front runner to stop any reverse pressure the turbine itself would have to spin in reverse direction to stop it exiting the rear of the turbo & back out the manifold flange.



You have to remember even when the gates venting, you still need to keep the turbo spooling. The aim is not to cut boost but to limit it to a desired amount.



My case is 48mm gate with 14psi springs & desired boost level is 18-20psi. Boost is controlled by ecu via duty solenoid.





Im starting to think over the weekend I'll rip it apart & plumb the other runner to the gate as all ive got is negative responses.



On the other hand Id love to prove so many nay sayers wrong https://www.nopistons.com/forums/pub...#>/biggrin.png

now that you point that out, the s4 stock turbo just goes to one runner....



it also depends on the turbo/engine and the boost he wants to run. if you want a big street port and smallish turbo to run 10psi, then no it prolly wont work, but if you want to run 20psi, then it might be fine.



the more boost you wanna run, the less you need the wg.....

Dont do that! Try it first, if it doesnt work out, plumb the other side.



People are just afraid of change.

Try it. It will work. There is no reason that it shouldnt.

Thats what i was saying, air cant do that. So to escape the air has to go through the turbo and this spins the turbine. But i have been looking around and reading a bit, this set up might work, i appologize for saying the idea was stupid. I still think there are better ways to do it, and if this way isnt dont correctly like j9fd3s was saying then yeah there could definately be problems. But, no one really knows how much pressure the wg has to bleed off and it is going to be different with different set ups so bleeding off pressure from one runner may be enough to keep the turbo from spinning any faster at the right boost level.



Dont quit now, test it and tell us the results. I am interested to know if it works and if so I want to know the positives and negatives. I promise if it doesnt go well, i will not be a dick, i say that with everyone as my witness.



Be careful though, you dont want to break an engine or anything. What kind of fuel management do you have?

Sorry guys, I caved in & changed the setup.



See the Ausrotary link in 1st post for all the info.



I would have liked to have it work but gave in for fear of engine damage due to VE differences front to rear rotors.



Thanks for your responses.

Wow. https://www.nopistons.com/forums/pub..._DIR#>/sad.png You gave in to theory and rhetoric. I guess we will never see if there were any benefits to that setup.

highly doubt any benifits, but running 20psi it prolly would have worked

Well, at least the runners would be totally separate. At 20 psi and the right turbo, the WG isnt doing much.