So I have a vq swapped s13 and I've bought a 6766 precision turbo with a 1.32ar twin scroll hot side. I was going to mount the turbo in front of the timing chain cover and have both banks come in. My question is, considering the twin scroll, do I now need to purchase 2 38mm wastegates? one for each bank. Also, do the wastegates need to be angled a certain way kind of like wideband sensors? Thanks.

 

If you want the twin scroll to work properly you should use two wastegates. The angle can affect wastegate operation and creatw issues like boost creep.

 

I believe a recent article in either modified or import tuner gave some good waste gate advice. Planning on boosting mine soon so it was some useful information.

 

Ok thanks guys. I just ordered 2 tial 38mm gates.

 

not the route i would have went personally, with the 1.32 AR definitely would have set it up for quick spool. i have mine set up (its a 6766 with 1.32 ar) so everything feeds into one volute and uses a tial mv-s?(cant remember off the top of my head) for boost control and a little closer to the turbo i use a 60mm that splits off the main exhaust pipe and feeds the other volute at 15 psi. 6 psi on the 2 step set to 4250 rpms, and have seen 5 psi as low as 2500 rpms.

are you intending to push the turbo to the max?

 

Do you have pictures of your setup. I'm having a hard time imagining it. Right now probably not pushing the turbo to the max. I want to see how the 1.32 plays out. I just bought it cuz someone was selling one for a decent price. Worst case scenario I change out the hotside for .96.

 

each wastegate has its own line now, but you can see how its setup, first time welding stainless with a mig so wasnt very happy how it turned out, plus i dont recommend using a plasma cutter to cut everything just because its easier............... makes it look crappy like this also its a cheapo ebay wastegate to feed the turbo volute, figure if it fails its unlikely to damage anything ill just have a leak, had to seal it with rtv because the top of the housing leaked, prefer tials version that is secured by screws.
you can also use the sound performance QSV i dint because this was cheaper and they where on backorder, 1.15 AR divided housing is about equal in flow to the .96 open so a qsv on that would be awesome or even the 1.0 divided housing if not looking to push the turbo to its max.

if whatever you use connects with vbands i encourage not using the lipped vbands in a setup like this because it makes it difficult to take the wastegate off.

 

lol amazing welds you got there. jk.

I'm kinda confused on what you did there. What is the purpose of dumping excess waste back into the up pipe. Why is there even a wastegate there. Can you clarify that for me.

 

thats not excess waste, the flange is a divided, the wastegate spring is a 15 psi spring so what happens is the entire exhaust feeds into a single half of the turbo turning my turbine housing essentially into a .55-60 ar open housing(since half is .66 but the divider takes up some of it.), this causes the turbo to spool much quicker as well as lowers boost threshold.

in a perfect world this would mean a 50% reduction in time to spool however the world is not perfect and there is some bleed off between the two volutes so the spool is actually increased by about 33% by time is what i and others who have similar setups have observed.

now i have a 15 psi spring in there so when the turbo hits 15 psi it begins opening the wastegate giving complete usage of the turbine housing and preventing the system from choking the engine up high and at higher boost. this works very similar to the sound performance quick spool valve however i have no idea if there is any advantage to one or the other, i do know that being a 60mm secondary volute feed wastegate there wont be any performance reduction from the turn simply due to shear mass, and the turn should cause enough of a backup to keep velocity high. can probably get away with a 50 or 55mm wastegate as well.

purpose is to give me the spool of a smaller turbine housing but the breathing and power potential of the full size housing. the two pipes dont actually merge they are seperate the entire length, the flat piece welded in is because i cut the second pipe wrong and had like a two inch gap in places, like i said dont be lazy and use a plasma cutter, tubing notcher or chop saw way better method. the much smaller tial unit is what is actually controlling boost pressure

 

I had to read you post twice before completely understanding. So how many lbs are you running that you needed a 15lb spring before purging into the second scroll.

and yes that pic was a little misleading, its hard to tell its a divided flange.

 

I just did some research on the QSV by SP and it seems like a great clean way of doing what you did there. What you did I can appreciate, its innovative but im gonna give this a shot. Good thing I didn't order the collector yet either because the qsv requires a undivided flange which makes sense.

also I did some research on what size wastegate would be essential for my build. I'm looking for 550-650whp. maybe more if I get greedy. According to some people you should get big wastegate for low boost and smaller wastegate for big boost. Is that true, so in terms I should stick with a 38mill or should I go 44. I don't think 60 is gonna do me much good. What do you think?

 

yup like i said the only reason i did it this way was the qsv's where on back order and this cost me about $200 to do vs $500 something for a qsv i just upped the boost so i run 26 psi on pump now, i was running 20 psi

 

Thumbs up to the QSV method , if you have the real-estate , great results on big ST Supras.

 

as i mentioned in deadeyes post with the 6766 1.32 housing i saw 1 psi at 3800 in first gear and 17 at 7000, vs jeffs 6765 with .96 open housing only seeing roughly 10 psi max in first even though the 1.32 is essentially a step up from the .96 open(1.15 divided is about equal to .96 open). higher gears show boost at a lower rpm, as low as 2500 for 5 psi

 

With a 38mm wastegate on each bank you will not have a problem with boost creep. I have mine mounted 90* and I'm only running 1 38mm tial on it with no boost creep. Just run higher boost and it goes through the turbine and not the wastegate.

 

Binder, I don't think im going with 2 gates anymore. Because the QSV requires a undivided flange so 2 gates is pretty pointless. Ill do one 38mm couple of inches before the flange.

 

What size turbo and what pressure are you running? If you are using high boost then most will go through the turbo and you won't have creep. Larger turbine housings will take more exhaust gas as well so no boost creep as well.

Just to be sure I would make sure it's at a nice 45* angle. Mine with a 6765 at 90* didn't have any issues with a TiAl MVS (38mm) and open dump. The MVS 38mm is a new design that is supposed to flow about 20% more than the old 38mm though.

 

he has a 6766 with 1.32 AR, i think he bought konrads =P

 

Hi i have built the same setup on a hr with a gt4294r, i tried a 50mm wastegate in the collector but it would creep from 5000rpm on. The best way i have found to control it was welding a pipe of the back of turbine with a 60mm gate hope that helps.

 

your either trying to run too little boost for the turbo, too small a turbine housing or something crazy