Ok, My series 4 tII motor is currently on an engine stand in my garage while I get it all prepped for install. I am going to be removing the turbo assembly to port the wastegate and was just wondering if I should remove the twin scroll flapper and port the exhaust manifold while it is all out. I will be running a full 3 inch exhaust. I have heard two sides of the story. I have heard that you will gain alot of turbo lag with the twin scroll removed, and I have also heard that if running a wide open exhaust it won't matter because the engine will rev much faster. Someone please help!!!!!! Oh yeah, is there anything I should know to help in removing the turbo? Those heat shields are kinda pesky!

 

My heat shields came off easier than my exhaust manifold

Anyways, lets look at it this way. The s5 doesnt have a twin scroll. Some say it creates massive lag, some say they didnt notice a difference. IMO, its stupid to have a little door in your exhaust.

 

I removed mine, and ported the passages to equal size on my s4. Yeah there is a little more lag, but I can feel a lot more power up top especially with full exhuast.

 

Yes, but the S5 turbo is significantly different then the S4 unit. The major reason it doesn't have twin scroll is because it has a true divided manifold. Mazda realised with that design, twin scroll was not necessary. IMO, twin scroll is benefician on a stock S4, and should not be messed with just "because the S5 doesn't have a twin scroll". We are talking about two very different systems here.

To the original poster, your large exhaust will just cause the twin scroll to become a restriction, so you should remove it and port out your turbine housing inlets (just don't go too thin on the bridge that devides the two).

 

I removed every single solenoid and the entire solenoid rack, etc. BUT I kept the twin scroll solenoid. I think you should keep it.

The car had full exhaust and intake. 13.425@105.5mph.

Jeff

 

i dont think it matters. i removed my entire emissions rack also, and removed my twin scroll. i couldnt tell a difference (however i do still have the stock catback, maybe that has something to do with it?)

 

Thanks for the responces thus far guys, I can see that there are mixed feelings on the subject. Hopefully I will get a few more posts about it. The twin scroll solenoid works on pressure right? What I mean is the ecu doesn't have anything to do with twin scroll does it? I am going to be using a Haltech if it would change anything.

thanks
John

 

correct, twin scroll is only controller by that solenoid and the actuator. ecu doesnt even know whats going on (big surprise)

 

I know there is a difference between the two units. However, it is in my opinion if you remove the twin scroll system and port the manifold you will make more power uptop (i dont care about +150rpm lag it might give me). Really, its a trade off between a semi-quicker spool and more power.

 

I was think about doing this also, but for differn't reasons, I may be driving my car alot next semester for college, and wonder is I take the twin scroll off, it won't hit full boost untill 4000 to 4500 rpms so there has to have an advatage of some gas milage, right or wrong?

 

Technically. You dont need as much fuel w/o boost. Or you could just shift at 3k before boost really comes in anyways?