The Twin Scroll Wastegate Debate

[ADIKT]

So last night I was doing some research - and I was trying to decide how and where I want my external wastegate plumbed

I will be running twin scroll headers into a vf22 with p25 TS exhaust housing (oversized billet wheel and ceramic bearing upgrade from SM) - Internal WG flap tacked shut

-

Basically the internets has given me a few options:

1. Alot of people seemed to think the ONLY way your going to keep a TRUE twin scroll set up is to have TWO EWGs.... (seems VERY overkill (the smallest EWG I could find was 38mm x2 = 76mm or 3" of wastgatage) - especially for a turbo of this size - I could understand doing it for a much larger turbo)

-

2. People also said that you can have the WG feed separate right up to the EWG (so the bottom of WG diaphragm seats on top of the diversion plate)

Compared to the IWG configuration. Theoretically they would essentially be set up the same (both scrolls kept separate right up to the WG)

This is a believe the back of an Evo turbo

3. Go with the internal gate and actuator

-

So many opinions and thoughts out there

At the moment I prefer the 2nd option

Edited August 11, 2014 by ADIKT

[boon]

I was having a good think about this a couple of nights ago.

I'm pretty sure the difference between option 1 and option 2 is going to be negligible. Even if the EWG valve doesn't seal perfectly on the divider plate it's not going to interfere significantly with the split pulses.

[ADIKT]

 boon said:

I was having a good think about this a couple of nights ago.

I'm pretty sure the difference between option 1 and option 2 is going to be negligible. Even if the EWG valve doesn't seal perfectly on the divider plate it's not going to interfere significantly with the split pulses.

My thoughts also... I think i will go with option 2 and see how that goes

[Guest]

Gtlegacy runs a split 38mm job with holset. Surely the internal would keep up with what youre going to be pushing thro it? Its not a mastiff 280wkw turbo.

[Ninja8)]

Is the diversion plate a must though? Definitely wont be cheap fabricating a twinscroll EWG setup!

[ADIKT]

 evowrx said:

Gtlegacy runs a split 38mm job with holset. Surely the internal would keep up with what youre going to be pushing thro it? Its not a mastiff 280wkw turbo.

I might still end up going back to internal

However I would like to go EWG if I can

[ADIKT]

 Ninja8) said:

Is the diversion plate a must though? Definitely wont be cheap fabricating a twinscroll EWG setup!

In my eyes it is. Without it you are essentially joining the two scrolls (balance pipe)

[Guest]

Twisting and raising it makes a heap more room to fit a gate in there. Just ask Steve if he thinks internal will handle it. Would think the gate area would be larger than p18/20 flappers and housings also slightly bigger again.

[ADIKT]

 evowrx said:

Twisting and raising it makes a heap more room to fit a gate in there. Just ask Steve if he thinks internal will handle it. Would think the gate area would be larger than p18/20 flappers and housings also slightly bigger again.

Fitment isn't such an issue Clint. Im going to give Steve a call when i have a chance to find out more details and to also get his view on this subject

At the moment my preferred option it to go ONE 38mm vband WG and have the diversion plate between the two scrolls

The Internal WG flap holes on the twin scroll are tiny - 1 38mm will be more than capable of handling

[Marky]

Will EWG definately be needed at all? Can you get by with porting out the internal instead maybe?

(Subaru turbo noob so dunno where that "point" is)

[ADIKT]

 Marky said:

Will EWG definately be needed at all? Can you get by with porting out the internal instead maybe?

(Subaru turbo noob so dunno where that "point" is)

I probably could get away with the Internal. but wank factor wants me to get an external cuzzy

[Marky]

Hahaha

For what it's worth - I used a twin scroll evo turbo on a V6 VR4, to keep it twin scroll I had the internal flapper removed, and the EWG was fed direct from there. The pipe to it was part of the exhaust flange if that makes sense.

If there's room to do it, I'd go that way (maybe a 90 bend would probably mount the gate about where clint has his?)

[ADIKT]

Don't really want to **** with the p25 housing. Would much rather cut holes in the headers. I get what you mean though.

[Marky]

Oh it's not part of the housing itself - just the flange you bolt to it

Call it option D haha

[ADIKT]

Na I mean by chopping the flap out or whatever.

I tried looking for pics of gotasuby holset twin scroll set up but couldnt find them

[Guest]

Option marky doesnt fly. Recess in the housing unlike the evo housings.

[ADIKT]

 evowrx said:

Option marky doesnt fly. Recess in the housing unlike the evo housings.

Yea i was just looking at pics on pc and thought the same thing.

Pic of vf36 p25 housing

[Guest]

Nope I stand corrected its not a single chamber like the S/S stuff. Op Marky is go. Be a prick to do tho.

Just stay internal then certs not required but youre going to adjusties anyway arent you?

[ADIKT]

 evowrx said:

Nope I stand corrected its not a single chamber like the S/S stuff. Op Marky is go. Be a prick to do tho.

Just stay internal then certs not required but youre going to adjusties anyway arent you?

Yep picked up some adjusties off a friend (scoob) to try. Hopefully they are ok!

[gotasuby]

this is what i have done for a few of these.

[ADIKT]

Any pics with no wrap? Or any close ups of the wastegate port? Is the wastegate port divided up to the flange?

[Koom]

I built mine with just one 38mm ewg and kept the split up to the valve face of the wastegate. I couldn't see the point in running two as you'd also have to keep their exits separated til much further down the exhaust otherwise there's the same balancing as a single wastegate once they open.

Two 38mm wastegate's is equivalent to running one of about 53mm. Which is still rather large and pointless as far as I can see.

[hijacka]

Running a divide means is not true t.s cough cough. lol. there will be a gap between the divider and the waste gate seat.

[Koom]

 hijacka said:

Running a divide means is not true t.s cough cough. lol. there will be a gap between the divider and the waste gate seat.

Same thing happens once one (or both) wastegates crack open with a twin system too.

And there won't be a gap between the divider and wastegate valve if you're really, really ridiculously good with an angle grinder

[hijacka]

 Koom said:

Same thing happens once one (or both) wastegates crack open with a twin system too.

And there won't be a gap between the divider and wastegate valve if you're really, really ridiculously good with an angle grinder

Noy really its about even flow right up to the turbo untill target boost pressure is reached. There will be a leak no matter how good you are with grinder, you could never get it to seal air tight, once pressure builds in the uppipe and it will leak and there will be a disturbance with the pulses. Running 2x wastegates keeps it true twinscroll its not theory its fact.

Edited August 15, 2014 by hijacka