2" piping too small?
11-23-2016, 02:59 PM
#1
2" piping too small? Hi guys, I'm getting ready to start building the pipes coming off the stock truck manifolds to go to the turbo. Motor is a 5.3 btr stage 1 turbo cam, running stock truck manifolds and will be using the on3 7875 .96 a/r. now my question is will 2" od pipe be too restrictive? I'm trying to to build the most responsive and fastest spooling setup as possible and keep exhaust velocity high. The inside diameter of the pipe is 1.78" because it's thick walled. I feel like this is just slightly too small for what I'm doing with a goal of 700whp. I only ask because i can get this stuff all day long (mandrel) at work for next to nothing and its good steel.
11-23-2016, 04:12 PM
#2
TECH Regular
Hi guys, I'm getting ready to start building the pipes coming off the stock truck manifolds to go to the turbo. Motor is a 5.3 btr stage 1 turbo cam, running stock truck manifolds and will be using the on3 7875 .96 a/r. now my question is will 2" od pipe be too restrictive? I'm trying to to build the most responsive and fastest spooling setup as possible and keep exhaust velocity high. The inside diameter of the pipe is 1.78" because it's thick walled. I feel like this is just slightly too small for what I'm doing with a goal of 700whp. I only ask because i can get this stuff all day long (mandrel) at work for next to nothing and its good steel.
i use two inch piping on my 5.7 iron block on3 88mm and made the hp your looking for with tick performance cam
but the on3 went out with very few hours on it just an f.y.i. but i like my size pipe turbo lights off very quick with a 3.27 gear
11-23-2016, 04:13 PM
#3
11-23-2016, 04:49 PM
#6
Yeah that sounds like the perfect size, however the stuff I have is 2" od and 1.78" id, I feel like this might be on the restrictive side, that's why I'm asking. does anyone think this would cause any back pressure problems? or stop me from making 650-700whp?
11-23-2016, 05:09 PM
#7
there is a thread on just this subject on y.b. I have made a couple with that turbo and a 5.3 with a triple 12 cam and a 2.5 hot side . it spools fast on the 2 step at 3500 rpm it will build 7 or 8 psi pretty fast. and once released it will get to 20 psi in 8 tenths of a second.works pretty good. your 2" pipes will get you to 6 or 700 but it will be maxed out pretty hard.
really doesn't give you room to grow.
really doesn't give you room to grow.
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11-23-2016, 05:35 PM
#8
I agree, 2 inch OD might be very limiting after 6 or 700.
Should be okay if that's all you want.
I like using 2 1/4" OD 16 gauge, supports well over 1000hp
A few years ago I made the mistake of using 2 1/2" on my 300zx and Thunderbird, both 5.3L builds, wayy too big for a 600ish hp setup.
Should be okay if that's all you want.
I like using 2 1/4" OD 16 gauge, supports well over 1000hp
A few years ago I made the mistake of using 2 1/2" on my 300zx and Thunderbird, both 5.3L builds, wayy too big for a 600ish hp setup.
11-23-2016, 06:27 PM
#9
I was going to just buy some 16ga 2.25 od off ebay, then I realized I can have this 2" bent however I needed for next to nothing, it's killing me haha cause I really wanna start making pipes but don't wanna have to do it twice because I know I'll wanna go higher in the future. I haven't read anybody going that small so im kinda on the fence about it...I mean the stock truck manifolds are 2.5" so right off the manifolds I would be Taking out roughly .750" but that might be a good thing for fast spool up and velocity. just don't know how small to small is haha
11-23-2016, 08:32 PM
#12
So after more reading, I think I'm gonna go for it. however, I think I'm going to run a 44mm wastegate per bank coming right off the manifold outlet BEFORE the 2" crossover pipe, that way there will be no back pressure issues while still having the fastest spool possible running the small pipes. if that makes sense. sounds good anyway...
11-24-2016, 05:35 AM
#14
I was going to run twin wastegates before, but had planned on putting them close to the turbo coming off the pipes. My thinking is that having them coming right off the manifolds will reduce any excess back pressure IF any under boost, but under light throttle there should be awesome low end torque and response with this size piping...? I mean if it's a bad idea and someone can tell me why I will gladly just buy the larger piping...
11-24-2016, 08:54 AM
#15
at higher flows small pipe becomes a restriction.
i dont think it'll keep you from 700hp in any way, but it will create higher drive pressures at the same boost pressure than a larger diameter would.
now for some totally anecdotal evidence...
I was in a similar spot as you this time last year, except for coming from the other direction. I was going to use 2.5 O.D schedule 10 stainless weld els and a standard 69mm gt45. After some reading I realized I didnt want to make myself an outlier in case I had problems. For my first scratch turbo build, I want the same cookie-cutter build as everyone else so I could get help diagnosing and troubleshooting.
So with the hot side partially built I scrapped it and went to 2.25 .065" exhaust tubing. I still want to try using SS weld els since they hold heat much better than thinwall tubing.
That wastegate placement might not be ideal and I can't really explain why. In school we learned that hot gasses very rapidly equalize pressure in a given space, but I guess that doesn't apply to exhaust since there are pulses? I'd put the gate(s) as close to the turbo as possible.
i dont think it'll keep you from 700hp in any way, but it will create higher drive pressures at the same boost pressure than a larger diameter would.
now for some totally anecdotal evidence...
I was in a similar spot as you this time last year, except for coming from the other direction. I was going to use 2.5 O.D schedule 10 stainless weld els and a standard 69mm gt45. After some reading I realized I didnt want to make myself an outlier in case I had problems. For my first scratch turbo build, I want the same cookie-cutter build as everyone else so I could get help diagnosing and troubleshooting.
So with the hot side partially built I scrapped it and went to 2.25 .065" exhaust tubing. I still want to try using SS weld els since they hold heat much better than thinwall tubing.
That wastegate placement might not be ideal and I can't really explain why. In school we learned that hot gasses very rapidly equalize pressure in a given space, but I guess that doesn't apply to exhaust since there are pulses? I'd put the gate(s) as close to the turbo as possible.
11-24-2016, 08:56 AM
#16
I had these same questions about a year ago when I turbod my stuff You can read night and day on the subject. I ended up with 2.25 od tubing as recommended by my camshaft guy in the end. We had a great talk about header design in turbo applications, and how cams affect both intake and final exhaust decisions
With that said, do yourself a favor and weld in an 1/8 inch pipe port and buy the 25.00 eBay 100psi sensor. Even if you can't log it, you can still monitor voltage and convert it to pressure in the system
With that said, do yourself a favor and weld in an 1/8 inch pipe port and buy the 25.00 eBay 100psi sensor. Even if you can't log it, you can still monitor voltage and convert it to pressure in the system
Last edited by Nathaninwa; 11-24-2016 at 09:15 AM.
11-24-2016, 09:15 AM
#17
I found with the thinner tubing of you ceramic coats it, it holds heat really well, and usually get my whole hot side done and the engine bays downpipe stuff done
at higher flows small pipe becomes a restriction.
i dont think it'll keep you from 700hp in any way, but it will create higher drive pressures at the same boost pressure than a larger diameter would.
now for some totally anecdotal evidence...
I was in a similar spot as you this time last year, except for coming from the other direction. I was going to use 2.5 O.D schedule 10 stainless weld els and a standard 69mm gt45. After some reading I realized I didnt want to make myself an outlier in case I had problems. For my first scratch turbo build, I want the same cookie-cutter build as everyone else so I could get help diagnosing and troubleshooting.
So with the hot side partially built I scrapped it and went to 2.25 .065" exhaust tubing. I still want to try using SS weld els since they hold heat much better than thinwall tubing.
That wastegate placement might not be ideal and I can't really explain why. In school we learned that hot gasses very rapidly equalize pressure in a given space, but I guess that doesn't apply to exhaust since there are pulses? I'd put the gate(s) as close to the turbo as possible.
i dont think it'll keep you from 700hp in any way, but it will create higher drive pressures at the same boost pressure than a larger diameter would.
now for some totally anecdotal evidence...
I was in a similar spot as you this time last year, except for coming from the other direction. I was going to use 2.5 O.D schedule 10 stainless weld els and a standard 69mm gt45. After some reading I realized I didnt want to make myself an outlier in case I had problems. For my first scratch turbo build, I want the same cookie-cutter build as everyone else so I could get help diagnosing and troubleshooting.
So with the hot side partially built I scrapped it and went to 2.25 .065" exhaust tubing. I still want to try using SS weld els since they hold heat much better than thinwall tubing.
That wastegate placement might not be ideal and I can't really explain why. In school we learned that hot gasses very rapidly equalize pressure in a given space, but I guess that doesn't apply to exhaust since there are pulses? I'd put the gate(s) as close to the turbo as possible.
11-24-2016, 09:33 AM
#18
I had these same questions about a year ago when I turbod my stuff You can read night and day on the subject. I ended up with 2.25 od tubing as recommended by my camshaft guy in the end. We had a great talk about header design in turbo applications, and how cams affect both intake and final exhaust decisions
With that said, do yourself a favor and weld in an 1/8 inch pipe port and buy the 25.00 eBay 100psi sensor. Even if you can't log it, you can still monitor voltage and convert it to pressure in the system
With that said, do yourself a favor and weld in an 1/8 inch pipe port and buy the 25.00 eBay 100psi sensor. Even if you can't log it, you can still monitor voltage and convert it to pressure in the system
11-24-2016, 09:38 AM
#19
That wastegate placement might not be ideal and I can't really explain why. In school we learned that hot gasses very rapidly equalize pressure in a given space, but I guess that doesn't apply to exhaust since there are pulses? I'd put the gate(s) as close to the turbo as possible.
11-24-2016, 09:49 AM
#20
I'm running a T6 twin scroll. 2.25 tubing fits nicely into each scroll. I'm running 44mm gates on each bank about 10 inches in front of the turbo flange. I have ran 4psi Wastegate pressure with no issues before. Still need to measure back pressure, but the turbine is the ultimate restriction in the system
I've been 168mph in a 2750lb car, puts it close to 1100whp, and I'll tell you what, spool time is not really an issue on the street
I've been 168mph in a 2750lb car, puts it close to 1100whp, and I'll tell you what, spool time is not really an issue on the street