Hot side tubing/bends
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TECH Fanatic
Joined: Sep 2013
Posts: 1,001
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From: Mechanicsburg, PA
Hot side tubing/bends Several guys here have built multiple hot sides in varying locations on different chassis'. What general tubing/bends do I need to at least come close to having enough to finish the hot side? I know nobody knows exactly. But I'd like to avoid extra shipping cost on some of the unique pieces. Straight pipe is readily available locally. Its the bends that I'm most interested in. I have flipped forward truck manifolds with V-bands welded on. The turbo will be mounted in front of the engine on the right side above the frame rail. T6 split flange. I think a pair of the U-J bends with some straight pipe would get me there. Thoughts?
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Joined: Feb 2020
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Only built 2 but I would say 180° bend per side is going to be cutting it close , I would like to have a bit more on hand if it's not readily available - shipped in. Don't forget you will need some for waste gate plumbing - in your case 2.
I've had good luck with these kits and they are cheaper than buying all the bends separate. I keep 2.5 and 3" on the shelf:
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Couple mild steal u/j bends should work fine I'd think. Or a set of bends like pictured above in mild steel can be had super cheap. SS can be a bastard to cut/shape weld. Mild steel is half the price (if that) and ive never managed to crack or have an issue with it. Not saying its better... just that it's easy and I've never had an issue. Smaller piping is easier to package too IMO. 2.25" to each side for the T6 flange should be more than enough.
Couple mild steal u/j bends should work fine I'd think. Or a set of bends like pictured above in mild steel can be had super cheap. SS can be a bastard to cut/shape weld. Mild steel is half the price (if that) and ive never managed to crack or have an issue with it. Not saying its better... just that it's easy and I've never had an issue. Smaller piping is easier to package too IMO. 2.25" to each side for the T6 flange should be more than enough.
I think it will depend alot on the engine used and its na power output. Mild motors would benefit much less from the larger piping. Makes sense with what I've done anyway. Not saying its "right". The diff between 2.5" to 2" was pretty night/day on my mild 5.3. went from not being able to spool the T4 S475 turbo at all, to spooling it very easily. (had way too tight of a converter and lazy compression). Then stepping up to a T6 S480... and spooling that very quickly as well. Not that a proper 2.5"/3" setup can't do the same. But with my particular setup/tune it couldn't and the only change was a 2" hotside.
And even if there were no benefits or draw backs to either power/spool wise. Smaller piping is much easier to package, is cheaper, and is thicker wall to boot usually. Not to mention a 2.5 or 3" pipe doesn't neck down to a typical T6 divided flange inlet well. Easier to double wrap etc. Wouldn't' suggest it for 4 sec drag cars but for street strip burnout machines its more than enough for 1000ish crank hp in my experience.
Its odd you say that as I've heard and experienced the opposite. Heard others big names say the same as you though. That larger piping net more power up top. Others state they are able to run smaller piping and a larger housing/turbo with the smaller piping netting less over all back pressure and better response. Which is what I experienced.
I think it will depend alot on the engine used and its na power output. Mild motors would benefit much less from the larger piping. Makes sense with what I've done anyway. Not saying its "right". The diff between 2.5" to 2" was pretty night/day on my mild 5.3. went from not being able to spool the T4 S475 turbo at all, to spooling it very easily. (had way too tight of a converter and lazy compression). Then stepping up to a T6 S480... and spooling that very quickly as well. Not that a proper 2.5"/3" setup can't do the same. But with my particular setup/tune it couldn't and the only change was a 2" hotside.
And even if there were no benefits or draw backs to either power/spool wise. Smaller piping is much easier to package, is cheaper, and is thicker wall to boot usually. Not to mention a 2.5 or 3" pipe doesn't neck down to a typical T6 divided flange inlet well. Easier to double wrap etc. Wouldn't' suggest it for 4 sec drag cars but for street strip burnout machines its more than enough for 1000ish crank hp in my experience.
I think it will depend alot on the engine used and its na power output. Mild motors would benefit much less from the larger piping. Makes sense with what I've done anyway. Not saying its "right". The diff between 2.5" to 2" was pretty night/day on my mild 5.3. went from not being able to spool the T4 S475 turbo at all, to spooling it very easily. (had way too tight of a converter and lazy compression). Then stepping up to a T6 S480... and spooling that very quickly as well. Not that a proper 2.5"/3" setup can't do the same. But with my particular setup/tune it couldn't and the only change was a 2" hotside.
And even if there were no benefits or draw backs to either power/spool wise. Smaller piping is much easier to package, is cheaper, and is thicker wall to boot usually. Not to mention a 2.5 or 3" pipe doesn't neck down to a typical T6 divided flange inlet well. Easier to double wrap etc. Wouldn't' suggest it for 4 sec drag cars but for street strip burnout machines its more than enough for 1000ish crank hp in my experience.
I've don't usually have a problem spooling turbos, I had 3" off the manifolds with twins so I knew dual 3" into a twin scroll T6 would only be faster. Pretty sure the SBE 5.3 record guys also run dual 3" to a GTX55 which has been proven to work well, granted they are running 40PSI at 8000+ RPM so the increased airflow helps.
2.5 vs 3" is about a $3 difference in material for me so not much saved there. The headers have 3" vbands so I dont need reducers to need to neck it down, and I run a flange like this which makes it easy on the turbo side:
I agree on backpressure, most everyone I deal with now has a 102 or 112mm turbine because they realized backpressure sucks. The amount of power the larger turbines make even on low boost is impressive, went from needing 25+ psi to crack 1000 to often doing it under 18PSI.
I've don't usually have a problem spooling turbos, I had 3" off the manifolds with twins so I knew dual 3" into a twin scroll T6 would only be faster. Pretty sure the SBE 5.3 record guys also run dual 3" to a GTX55 which has been proven to work well, granted they are running 40PSI at 8000+ RPM so the increased airflow helps.
2.5 vs 3" is about a $3 difference in material for me so not much saved there. The headers have 3" vbands so I dont need reducers to need to neck it down, and I run a flange like this which makes it easy on the turbo side:
I've don't usually have a problem spooling turbos, I had 3" off the manifolds with twins so I knew dual 3" into a twin scroll T6 would only be faster. Pretty sure the SBE 5.3 record guys also run dual 3" to a GTX55 which has been proven to work well, granted they are running 40PSI at 8000+ RPM so the increased airflow helps.
2.5 vs 3" is about a $3 difference in material for me so not much saved there. The headers have 3" vbands so I dont need reducers to need to neck it down, and I run a flange like this which makes it easy on the turbo side:
Also if the scroll exit is approx 1.6" on a 1.32 T6. I just can't see needing 3" piping feeding each side of that. If the bottle neck in the system and wheel restriction dictates the drive pressure... whats the benefit of having big 3" pipes before that? Stepping up and down exh speed all over the system seems odd. I'm not doubting it works, or that people see results at huge power/rpm/boost. I just don't understand it fully.
The 8000+ RPM and retardo boost def play a big roll in exh speeds and turbulence. If we cut that down to the 6-7k range and 20lbs and under many mild setups run, I think its much less of a factor! Not sure what the OP's goal is. but sub 900 crank at 7k and below I just can't see needing more than factory manifolds and 2" piping. 2.25" max. Big power/RPM setups are a little out of my wheel house unfortunately. But I'm trying to get quicker!
Also if the scroll exit is approx 1.6" on a 1.32 T6. I just can't see needing 3" piping feeding each side of that. If the bottle neck in the system and wheel restriction dictates the drive pressure... whats the benefit of having big 3" pipes before that? Stepping up and down exh speed all over the system seems odd. I'm not doubting it works, or that people see results at huge power/rpm/boost. I just don't understand it fully.
Also if the scroll exit is approx 1.6" on a 1.32 T6. I just can't see needing 3" piping feeding each side of that. If the bottle neck in the system and wheel restriction dictates the drive pressure... whats the benefit of having big 3" pipes before that? Stepping up and down exh speed all over the system seems odd. I'm not doubting it works, or that people see results at huge power/rpm/boost. I just don't understand it fully.
Thread Starter
TECH Fanatic
Joined: Sep 2013
Posts: 1,001
Likes: 123
From: Mechanicsburg, PA
It's a street/strip sleeper. 5.3, 78/75 (for now, hence the T6 flange with T6-T4 adapter), 4l80E in a heavy weight car. Goal will slowly increase, I'm a realist! Starting off at whatever whp the billet 78/75 will make maxed out on E85 and then go from there. I need to get a handle on the tuning end of things before the next step. Plan is 2.25 pipe and stock manifolds. I don't see this car ever over 800 whp. Not going to cage it and I have kids.
It's a street/strip sleeper. 5.3, 78/75 (for now, hence the T6 flange with T6-T4 adapter), 4l80E in a heavy weight car. Goal will slowly increase, I'm a realist! Starting off at whatever whp the billet 78/75 will make maxed out on E85 and then go from there. I need to get a handle on the tuning end of things before the next step. Plan is 2.25 pipe and stock manifolds. I don't see this car ever over 800 whp. Not going to cage it and I have kids.
Several guys here have built multiple hot sides in varying locations on different chassis'. What general tubing/bends do I need to at least come close to having enough to finish the hot side? I know nobody knows exactly. But I'd like to avoid extra shipping cost on some of the unique pieces. Straight pipe is readily available locally. Its the bends that I'm most interested in. I have flipped forward truck manifolds with V-bands welded on. The turbo will be mounted in front of the engine on the right side above the frame rail. T6 split flange. I think a pair of the U-J bends with some straight pipe would get me there. Thoughts?
I usually try and visualize the pipe route, get some J or U bends, some straight. I can get diff bends by cutting at angles. Walker has a short 90 deg. (41221) that makes life easier in some cases, but in the end I have a pile of tubing for the next project, lol. Try and get the thicker tubing, not the thin wall parts store stuff.