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hey guys i m trying to find 022' approaches to rear mount SINGLE turbo setups.
im planning on swapping a E90 BMW with a 5.3LS (cam heads etc) through a 4l80e. for daily driving usage.
there is good quality kits (engine bay) out there for the E90 chassis but fairly expensive
+ i like the idea that i can setup the engine bay "NA" and since i have to build a exhaust anyways ( Y pipe most likly) i can Vband this exhaust , drive the car NA and work on a Rear mounted Turbo setup over time.
i understand the extra length of piping but i feel much more comfortable to weld those "hot side setups" than in a setup for a very confined space in the Engine bay.( guess its skills and patience lol)
i have T4 78/75 already and think this could be a good turbo for such a rear mounted setup.
i understand that getting Heat into the turbo is a focus and a exhaust wrap helps+ a turbo blanket.
do you downsize the hot side pipe after the Y to increase "pressure" from 2.5 to 2.225 or 2 " to the T4 flange?
i also understand that you need a oil reservoir where the Turbo drains into and a scavenge pump to lead the oil back in the drain. which i can setup in the oil pan ( 8AN or 10 An drain line?)
in terms of costs i think its not that wild ... i have the t4 78/75 already
exhaust/ hotside needs to be build regardless.
Location of the Oil reservoir ( around 50$) + Scavenge pump (80$) is probably the hardest part.sicne you want to drain the turbo via gravity
any comments will help
here is a nice setup on a 1 series , a bit to much 90s i think but he claims it works well
OP, you don't need to downsize the hotside after the merge. Stock manifolds/y/etc. Chuck cats if you can. A standard diameter axle-back is fine, just no muffler. Wrap the hot side as much as you can.
Run as big of an oil return as you can. I run an turbowerx Spartan pump to the pass side valve cover but the timing cover is fine too, which ever is easier.
My setup is rowdy when the exhaust cutout post turbo is open, so if you do street driving I suggest tucking in a muffler instead of running an open turbo downpipe.
I would downsize the turbo for a daily. On my 5.3 with a cam it was fine with a front mount 78/75 t4 billet but switching to a billet 70/70 the car was a whole new animal. Made more boost and faster on light throttle around town and made it perfect under 6500. Logs show no real loss in power at the same
boost level but I picked up a bunch down low bc boost comes in harder and sooner. I did some tests making my own 70/75 and the 70/70 was better all around. Turbo is $700 ish at VS. The 72/65 is $399.
On a rear setup I would suggest a cheapy 72/65 or around there in either a .8 or .9 AR. I think you will be much happier but keep the t4.
https://turbo4less.com/product/vsr-72-65-billet/
Last edited by customblackbird; 08-29-2022 at 06:10 PM.
I can share my direct rear mount turbo swap experience as I went through 3 turbos-
Started with the STS upgraded turbo which is a GT67. Light switch but felt choked.
Went to a Billet 7665. Much better and more suited to stockish rpm range. Topped out about 6k, maybe a little higher.
Finally went to a Billet 7875. Pulls to 7k+ and wants to keep pulling. Give up some lowend, but its helped with traction in lower gears. When 3rd gear hits and it wants to spin the tires at 90 mph, its LOL.
When I had a rear mount I ran a straight thru "race muffler" which is more like a resonator before and after the turbo, made it amazingly quiet to cruise around. I ran long tube headers, merged to a single 3" to a T4 flange. Worked about as well a single 7875 could.
I can share my direct rear mount turbo swap experience as I went through 3 turbos-
Started with the STS upgraded turbo which is a GT67. Light switch but felt choked.
Went to a Billet 7665. Much better and more suited to stockish rpm range. Topped out about 6k, maybe a little higher.
Finally went to a Billet 7875. Pulls to 7k+ and wants to keep pulling. Give up some lowend, but its helped with traction in lower gears. When 3rd gear hits and it wants to spin the tires at 90 mph, its LOL.
Could you post some pics of your rear mount setup?
Thinking of going this route, i have a Comp Oilless Billet 78/75 im going to put out back and was curious in routing of everything.
I’d like to hear a power goal? I’d also assume you can ditch the aftermarket heads idea if you go with a turbo… Its really not needed. If my goal was a 600hp remote setup… I would use 2” off the manifolds merged to a single 2.25”. Then run a 2.5” cold side. It would be easier to package, cheaper, less weight, and IMO it would spool better.
I hear a lot of “you don’t need to downsize the piping” claims. But I’ve yet to see someone who has went from say a 3” setup feeding the turbo to say a 2.25.
Being one of the few to actually run 2” piping (1.8” ID) on my “Standard” turbo kit. I can say 2” off factory manifolds to each side of a T6 S480 was a nasty setup and worked extremely well to about 900chp. Going by trap speed and weight, Wallace calc put me over 900. And I believe that’s wheel HP. Ran it on a 370” 6.0 and a 4.8. Net the same 158/159 trap with both at different boost levels. Previously had a 2.5” setup with a t4 1.10 S475. The 2” setup spooled the T6 1.32 S480 faster. It weighed less, was cheaper to make, and easier package. Another plus is smaller piping is cheaper to wrap. You can double wrap it in most areas too, as it takes up much less space. I saw zero down sides… except possibly hitting a wall power wise above 900. My setup didn’t want to trap quicker with added boost on either setup.
I’d like to hear a power goal? I’d also assume you can ditch the aftermarket heads idea if you go with a turbo… Its really not needed. If my goal was a 600hp remote setup… I would use 2” off the manifolds merged to a single 2.25”. Then run a 2.5” cold side. It would be easier to package, cheaper, less weight, and IMO it would spool better.
I hear a lot of “you don’t need to downsize the piping” claims. But I’ve yet to see someone who has went from say a 3” setup feeding the turbo to say a 2.25.
Being one of the few to actually run 2” piping (1.8” ID) on my “Standard” turbo kit. I can say 2” off factory manifolds to each side of a T6 S480 was a nasty setup and worked extremely well to about 900chp. Going by trap speed and weight, Wallace calc put me over 900. And I believe that’s wheel HP. Ran it on a 370” 6.0 and a 4.8. Net the same 158/159 trap with both at different boost levels. Previously had a 2.5” setup with a t4 1.10 S475. The 2” setup spooled the T6 1.32 S480 faster. It weighed less, was cheaper to make, and easier package. Another plus is smaller piping is cheaper to wrap. You can double wrap it in most areas too, as it takes up much less space. I saw zero down sides… except possibly hitting a wall power wise above 900. My setup didn’t want to trap quicker with added boost on either setup.
I went from large piping to stock piping. Longtubes and 3 inch Y to stock manifolds and Y was a HUGE improvement in boost response and I was even able to make more boost as well.
I went from large piping to stock piping. Longtubes and 3 inch Y to stock manifolds and Y was a HUGE improvement in boost response and I was even able to make more boost as well.
That’s great to hear! If there was that drastic of an improvement, 2” and 2.25” would likely be a tad better if you didn’t hit a HP cap. I’ve seen a few impressive remote setups, but they all used what I consider grossly oversized piping on the hot and cold sides and undersized turbo housings. Owners claimed lag wasn’t an issue with the right converter and housing. I’d just be super curious where the power cap was. If I could get away with smaller diameter pipe and a larger exh. housing w overall lower back pressure, it would be a win across the board.
I’d like to hear a power goal? I’d also assume you can ditch the aftermarket heads idea if you go with a turbo… Its really not needed. If my goal was a 600hp remote setup… I would use 2” off the manifolds merged to a single 2.25”. Then run a 2.5” cold side. It would be easier to package, cheaper, less weight, and IMO it would spool better.
I hear a lot of “you don’t need to downsize the piping” claims. But I’ve yet to see someone who has went from say a 3” setup feeding the turbo to say a 2.25.
Being one of the few to actually run 2” piping (1.8” ID) on my “Standard” turbo kit. I can say 2” off factory manifolds to each side of a T6 S480 was a nasty setup and worked extremely well to about 900chp. Going by trap speed and weight, Wallace calc put me over 900. And I believe that’s wheel HP. Ran it on a 370” 6.0 and a 4.8. Net the same 158/159 trap with both at different boost levels. Previously had a 2.5” setup with a t4 1.10 S475. The 2” setup spooled the T6 1.32 S480 faster. It weighed less, was cheaper to make, and easier package. Another plus is smaller piping is cheaper to wrap. You can double wrap it in most areas too, as it takes up much less space. I saw zero down sides… except possibly hitting a wall power wise above 900. My setup didn’t want to trap quicker with added boost on either setup.
Wallace has a disclaimer they are calculating crank hp. 900 crank would be a limitation for some but I doubt that's the limit of 2" hotside especially on a 4.8L. I've done over 1100whp with 2.25 hotside, I'm sure others have done a lot more. Most guys that go to 3" hot sides aren't concerned with stoplight races, they want to rev to 8000 or more, make 1500+whp often with engines larger than the typical 5.3/6.0 stuff, some are running races longer than the 1/4 mile,
I still don't get some peoples desire for more low end power on a turbo V8. Big turbos already spool up too fast for street use without pulling timing for traction, drag race guys are leaving with the turbos lit at 4000+ RPM anyway. Maybe people just like doing rolling burnouts, can't fault that
That’s great to hear! If there was that drastic of an improvement, 2” and 2.25” would likely be a tad better if you didn’t hit a HP cap. I’ve seen a few impressive remote setups, but they all used what I consider grossly oversized piping on the hot and cold sides and undersized turbo housings. Owners claimed lag wasn’t an issue with the right converter and housing. I’d just be super curious where the power cap was. If I could get away with smaller diameter pipe and a larger exh. housing w overall lower back pressure, it would be a win across the board.
On a stick car with no slick or 2 step, I don't want to wait for power lol. My DD is tuned to make boost at 1500 rpms....and it's NOT a diesel 🤣. I want all the low-end, its just more fun when cruising around.
On a stick car with no slick or 2 step, I don't want to wait for power lol. My DD is tuned to make boost at 1500 rpms....and it's NOT a diesel 🤣. I want all the low-end, its just more fun when cruising around.
Don't need a slick but a stick car certainly needs a better tire than an auto to handle instant boost, only thing instant power got me with my TR-6060 was a broken input shaft.
Generally any turbo that's online at 1500RPM has severely limited top end, reminds me of those K03 and K04 turbo days running 30+ PSI with hardly any gains just hotter IAT's, slap on a disco potato and they actually started to get quick.
I don’t need more rolling response on the street, but I don’t like sitting at the tree waiting on boost. Or running bleed valves on transmissions, or needing to spool the turbo for extended periods of time cooking the fluid before staging etc. The quicker I can light off the turbo on the brake, the better IMO. I think the argument was originally geared towards running a larger turbo with less back pressure and retaining similar spool characteristics.
I went through all the usual channels and suggestions as to why the car wouldn’t pick up. First everyone said it was the T4 turbo. Even though it was a 1.25 T4 with the 87/96 wheel and I was monitoring back pressure. So went with the T6 1.32 S480. BP dropped from 1.6 to 1.4… But basically ran the same. Then everyone swore it was valve springs. So I tested mine. Even though they were fine spec wise… I replaced with a heavier spring with more than enough seat pressure. Didn’t fix it. Richer/leaner more/less timing didn’t matter. Even changed intakes… converter and cam (several times) nothing made a difference. It would just hit a wall and didn’t want to make more power. With the 6.0 it was done by 6800ish. With the 4.8 7300ish… Both trapping identical making the same power. (4.8 running more boost of course.) I wasn’t sure what else to try and then wrecked the car… so I’ll never know I suppose.
I wouldn’t build a setup with 1.8” ID piping again if I wanted over 800ish crank though. 800ish and below I think your golden… no reason to run larger. 2.25” 16g exhaust tubing is pretty much 2” ID anyway. (Believe its 2.1” ID)
Don't need a slick but a stick car certainly needs a better tire than an auto to handle instant boost, only thing instant power got me with my TR-6060 was a broken input shaft.
Generally any turbo that's online at 1500RPM has severely limited top end, reminds me of those K03 and K04 turbo days running 30+ PSI with hardly any gains just hotter IAT's, slap on a disco potato and they actually started to get quick.
Definitely need a better tire than an auto for sure. I don't mind topping out the DD at 6300-6500 rpms....variably cams FTW. Being in boost at 1500 is fantastic for my driving style. But that's also why on my Camaro I shifted from the GT67 to the 7665 to the 7875, so it'll rev over 7k no issue.
Thanks to everyone.
amazing knowledge here..
So I have no real HP goals. And Its also very bold to say it will be a daily..lol .. lets say i want it reliable with potential to drive it to work. But the initial build is nothing usual.
I will put this nice 5.3 LS + 4l80e I have in a BMW e90 4 door.
it's cammed with good specs to still run a stock converter for drivability.
I will run gen 5 camaro manifolds due to clearance, so another reason i am not sure if i will benefit of head porting really i might choke the potential NA.
I have a 78/75 on the shelf and I will use it. I am not looking to invest in a another turbo.
Good info on the hotside piping. YES I was planing on. Going Y pipe.Ythe oil return will be a 10AN most likely into the pan. Since that's a straight shot on the driver side most likely.
I understand to have a oil reservoir but what size is efficent?
and I read most scavenge pumps run strong and suck the turbo/reservoirs dry? How do you control the scavenge pump speed and where do you mount this controller?
OP, you don't need to downsize the hotside after the merge. Stock manifolds/y/etc. Chuck cats if you can. A standard diameter axle-back is fine, just no muffler. Wrap the hot side as much as you can.
Run as big of an oil return as you can. I run an turbowerx Spartan pump to the pass side valve cover but the timing cover is fine too, which ever is easier.
My setup is rowdy when the exhaust cutout post turbo is open, so if you do street driving I suggest tucking in a muffler instead of running an open turbo downpipe.
Other questions ask away.
thanks alot.
Yes I plan street driving, so a muffler after the turbo i assume.?
08-22-2022, 10:12 AM
Rear mounted turbo advices needed 
I'm here!
