3 to 4 bolt conversion

RUQWKNF

KEEPER OF SECRETS
Staff member
May 26, 2001
2,427
292
83
47
NEED TO KNOW BASIS
s78.photobucket.com
Before you weld your wastegate feed pipe, make sure you loosely install the wastegate, so you can determine the dump angle and if there's going to be any interference with surrounding components. That would really suck if you got it all fabbed up only to find out the wastegate won't clear this or that. Kinda the measure 4 times cut once method. Also, I'm glad to see you decided to plumb it under the turbo, so that both banks are feeding the wastegate vs just plopping it on the cross over pipe. Sure that worked for a lot of us years ago, but with better flowing cam/heads and more efficient turbos, mounting it on the crossover it no longer a 100% sure bet. Chuck's wizardry welding of that stubby feed pipe directly onto the turbine housing would be nice, but I would keep an eye on the welds overtime. That much weight of a large wastegate hanging onto the turbine housing at insane EGT's would take a tole on it over time. Think metal fatigue. But it would be in an extreme constantly raced case, not something that you'd occassionaly race.

A lot of guys have been using the .81 A/R T4 Tangential turbine housings with great results over the years. With your CI size, the .96 single inlet Tangential style turbine housing would be GTG. A good PTC or Husek converter will be required once you start initial testing. And having a BB turbo will help the transient response and spool up on the initial hit. Tune will help finalize the spoolup curve as well. When I was spec'ing back in the day, if the combo was under 270", I would recommend the T4 .81. If 274+ and racecar, the .96 would be the starting point. High hp (over 1200 fwhp) would change it from there. You mentioned a 6871 turbo and the CI size, so I'm guessing this will be a street car with some active street antics involved. Is it safe to say you're looking for 850-950 rwhp with 1:1 - 1:8ish BP goals? If so, look closely at Gen 2 CEA turbine wheels and BW's top of the line turbine wheels. But you probably already know this so I digress.

Others have dabbled with divided T4 twin scroll housings with larger A/R's. Most of those guys keep their results COSMIC TOP SECRET though. There are limitations to what the normal size T4 housings can do, as evident by the larger T4 "mid" frame turbo combos out there. IE: the old TSL class and current TSO class combos.

-Patrick-
 
  • Like
Reactions: dank GN

dank GN

BlackArts Automotive (661)993-8277
Jan 11, 2009
3,451
401
83
SoCal the high desert
Thankfully I finally fit it up in the car . Where I was thinking I could go with the wastegate pluming is going to be alil tight. So I’m just going to move it up towards the turbo alil more . I am waiting for my wastegate to actually get here before I cut and weld anything. I did invest in a good wastegate finally. I got a precision 46mm instead of my old Chinese 4 bolt POS. A quick question about that 46mm gate does it work well with CO2? I will be running co2 with my boost leash controller. He actually recommends having 2 ports on the top of the gate can I just drill and tap another port up there like I did with my POS gate?
2657A31F-94FD-45A6-B095-03A5A50CF8B7.jpeg
A8A268E8-99CF-461D-8D48-77C116E1F0B8.jpeg
 

dank GN

BlackArts Automotive (661)993-8277
Jan 11, 2009
3,451
401
83
SoCal the high desert
Before you weld your wastegate feed pipe, make sure you loosely install the wastegate, so you can determine the dump angle and if there's going to be any interference with surrounding components. That would really suck if you got it all fabbed up only to find out the wastegate won't clear this or that. Kinda the measure 4 times cut once method. Also, I'm glad to see you decided to plumb it under the turbo, so that both banks are feeding the wastegate vs just plopping it on the cross over pipe. Sure that worked for a lot of us years ago, but with better flowing cam/heads and more efficient turbos, mounting it on the crossover it no longer a 100% sure bet. Chuck's wizardry welding of that stubby feed pipe directly onto the turbine housing would be nice, but I would keep an eye on the welds overtime. That much weight of a large wastegate hanging onto the turbine housing at insane EGT's would take a tole on it over time. Think metal fatigue. But it would be in an extreme constantly raced case, not something that you'd occassionaly race.

A lot of guys have been using the .81 A/R T4 Tangential turbine housings with great results over the years. With your CI size, the .96 single inlet Tangential style turbine housing would be GTG. A good PTC or Husek converter will be required once you start initial testing. And having a BB turbo will help the transient response and spool up on the initial hit. Tune will help finalize the spoolup curve as well. When I was spec'ing back in the day, if the combo was under 270", I would recommend the T4 .81. If 274+ and racecar, the .96 would be the starting point. High hp (over 1200 fwhp) would change it from there. You mentioned a 6871 turbo and the CI size, so I'm guessing this will be a street car with some active street antics involved. Is it safe to say you're looking for 850-950 rwhp with 1:1 - 1:8ish BP goals? If so, look closely at Gen 2 CEA turbine wheels and BW's top of the line turbine wheels. But you probably already know this so I digress.

Others have dabbled with divided T4 twin scroll housings with larger A/R's. Most of those guys keep their results COSMIC TOP SECRET though. There are limitations to what the normal size T4 housings can do, as evident by the larger T4 "mid" frame turbo combos out there. IE: the old TSL class and current TSO class combos.

-Patrick-
Thanks for your input I really appreciate it when someone with your knowledge especially with turbos can shed alil light on these type of topics .
 

dank GN

BlackArts Automotive (661)993-8277
Jan 11, 2009
3,451
401
83
SoCal the high desert
If you are not satisified with spooling/response, you could get the converter re-stalled higher.
Yes and luckily my converter guy is local and is really cool with doing restalls for me . It’s a pain getting it out but I’ve done it to many times to count so if I I’ve gotta yank it again what’s one more time to add to the count :) also thanks for your input aswell nick :)
 

dank GN

BlackArts Automotive (661)993-8277
Jan 11, 2009
3,451
401
83
SoCal the high desert
Okay so I tacked up the wastegate pluming. I will add a brace later from the T4 flange to the wastegate . It’s sitting at a 33* angle . I’m pretty sure the location where I choose to split to the wastegate should supply the gate with plenty of hot gasses to bypass .
 

Attachments

dank GN

BlackArts Automotive (661)993-8277
Jan 11, 2009
3,451
401
83
SoCal the high desert
So I got my 46mm precision wastegate. And the inlet and outlet are 2 different sizes unfortunately so it looks like I will have to chop the Vee band off and weld on the larger one . I will also have to cut the striat piece of pipe and angle it so it’s a lil more flat . Other then those last 2 welding deals I believe I should be all finished up . I’m also going to be running CO2 and on the boost leash instructions it recommends the pressure sensor and the inlet be separated does anyone know if I just use a tee fitting and screw the pressure sensor in on the side and the inlet coming in from the top of this would mess up my boost leash readings ? In my previous gate I actually just drilled another hole and tapped it 1/8” not . Also what size spring should I run ? The 1.5lb spring ? No spring like my last gate ? 3lb? Thanks guys for your input
 

Attachments

turbobitt

Well-Known Member
Feb 14, 2002
2,373
368
83
46
Southington CT
IMO you should have run a solid pipe to the wastegate and ran the flex coupling post wastegate into the downpipe. At least with a rigid wastegate mounting if you decided to run the gate to atmosphere you wouldn't need a support to the floppy wastegate. If its a cheapo 300 series flex than expect to be replacing it soon. The flex wouldn't be exposed to the exhaust back pressure post wastegate and less chance for failure and even then would just cause a annoying leak/noise and not effect boost.
 
Top Bottom