Turbo Thread links - aka choosing a turbo

[Will L.]

Yes, the divided housing is too cause a faster spool but the division causes a little loss on top end. Help one area and it hurts another. No free lunches. There are types of a QSV that blocks one side of the twin scroll to get the similar effect.


The progression from there is to a variable vein turbo to get the best of both worlds. Thats whats on the new diesel trucks. But now a computer and a stack of sensors feeding it to control the turbo. And the soot eating egr then helps mess them up.

I don’t know of many folks to have put vvt on the 6.5. @Twisted Steel Performance has a nifty one on his wazoo p400. Controlling it is the challenge.
Many of the controllers fall short - I am anxiously awaiting to see this one is dialed in. A bit out of my price range unfortunately. Then again, some say when dealing with the wife it’s better to ask forgiveness than permission…

 

[Rockabillyrat]

Yes, the divided housing is too cause a faster spool but the division causes a little loss on top end. Help one area and it hurts another. No free lunches. There are types of a QSV that blocks one side of the twin scroll to get the similar effect.


The progression from there is to a variable vein turbo to get the best of both worlds. Thats whats on the new diesel trucks. But now a computer and a stack of sensors feeding it to control the turbo. And the soot eating egr then helps mess them up.

I don’t know of many folks to have put vvt on the 6.5. @Twisted Steel Performance has a nifty one on his wazoo p400. Controlling it is the challenge.
Many of the controllers fall short - I am anxiously awaiting to see this one is dialed in. A bit out of my price range unfortunately. Then again, some say when dealing with the wife it’s better to ask forgiveness than permission…

Actually, a fully divided system with a twin scroll is more efficient because of the scavenging, even at higher RPM. Yes the CFM of a open turbine vs a twin scroll is slightly more, but you loose the scavenging advantage.

 

[jrsavoie]

All I have to say on the subject is, it's certainly nice to have people that know their stuff around here.

 

[Will L.]

I know barely anything on turbos. On my race truck there was a guy who understood them insanely well. He worked with Gale Banks way back and they learned them together. So I learned a couple things drom him but he was like Gale in that he shared enough so you knew he knew his stuff, then gave him your money. I think Gale & him shared with him enough and they split so they both knew they were in competition with each other and would be with others in the future. This guy was a one man show til he died and never did enough volume to become famous, Gale duplicated himself with employees making millions and living 2 decades longer so we all know his name.

To be clear I am trying to learn enough right now to finalize which to go with on my build and hopefully make a location a future 6.5er can find compiled information where they can do the same.

If the two sides were divided the entire way, and done with headers then we could see some scavenging. But without it i don’t think we would get much to speak of.

My twin turbo truck- I built headers. It absolutely made a difference. I never had the two sides connect and never corrected the firing order in-balance.
18726543
One side count the dash - as a pause.

1-7- - 5-31-7- -5-31-7… The other side
-8-26-4- -8-26-4- -8-26..
so a header wont push equally but when tubes at the same length the individually scavenge. In a manifold wether truck or hummer style two cylinders are not happy on each side. A hummer manifold is more efficient by simple distance but log style manifolds amplify one issue: picture a tube next to the head exhaust ports and think of it pushing out playdoh each time and you’ll get the interference. Don’t look at 1 as always first. Look at the middle of the order where the exhaust gets bunched up. 5-31-7 and “see them” exiting through the manifold fighting each other like kids first out.
Same issue for even side, infact worse on hummer log turbo manifold: 8-26-4.
8 escapes easily, 2 goes and maybe is not in the way of 6-4 or maybe it is? 6 firing just before 4 is a “natural scavenge” leaving a negative pressure wave behind that lets 4 flow easier. But # 2 and #1 are busy driving down the hiway and all the others try merging in its path.
Is the hummer log better than the truck? Absolutely. Having the equal length headers are the lanes that stop collisions. So imo building an unneven length header is better than the log. But no scavenging effect is guaranteed like we see in video demonstrations.

! I am an idiot. I can do the sticky note demo on my hummer manifold and see if there is any scavenging. I will make a video and share it asap. Others please do the same with truck manifolds, posting links and write the description here incase YouTube links fail later.


In a single twin scroll one side will see not an even flow but to the turbo shaft it is still a some what constant stream so the turbo spins better divided yes. Take something like a lunch box and set on the table, push it across the hand on the side so it slightly twists as it goes. Not a hand in the middle- make it walk as the example.
Left right left right right left right left left right.
That is the firing order.

More so, that is part of why our center main webs break first. Not just middle of crank flexing more, but those four cylinders fire one after another. 1872 is the opposite corners. Then 6543 all next to each other going rear to front creates a constant pressure in the middle of the crank then the middle relaxes and farthest front fires. Then the two at the rear do a combo punch, then the front area (2) goes out of nowhere. Then the rear to front order innthe middle of the crank again 6543.
Just some engine designers that didn’t analyze physics enough. If they had we would have 9 cylinder engines in a triple delta, The best 6 cylinders are 2/3 the way there. Electricians that work on and test motors understand the traid and it becomes so obvious…but that’s another rant.

Yall know I wanna keep talking but now I’m anxious to do the scavenge test.

 

[Will L.]

Not ours obviously but shows a turbo header properly made vs manifold not proper:

 

[Custom Deluxe]

Although on my 93, there is a lot of room directly behind the intake, kind of a recessed area in the firewall. anyone have any pics of a center mount setup in a truck?

Here’s a pic of my motor with center mount intake manifolds Quadstar custom intake. Going to use a side mount turbo with twin scroll exhaust flange and t4 turbo. Hopefully I can get the custom exhaust manifolds built by the end of next weekend. It will be left and right bank divided all the way. 1-3/4” primaries to 3” log and 3” crossover.

 

[Rockabillyrat]

Here’s a pic of my motor with center mount intake manifolds Quadstar custom intake. Going to use a side mount turbo with twin scroll exhaust flange and t4 turbo. Hopefully I can get the custom exhaust manifolds built by the end of next weekend. It will be left and right bank divided all the way. 1-3/4” primaries to 3” log and 3” crossover.

3" crossover is HUGE. gonna loose a lot of velocity. I wouldn't go over 2.5 personally.

 

[Will L.]

On the van/hummer/hmmwv intake: Did he flow bench it to correct the bad cylinder? I can’t remember which it is off hand but one flows horribly less than the others. The center piece he made looks nice. Normally I would agree with Rockabillyrat on the size- but the center section is insanely bad and small for the gm6 turbo. The opening to the logs and actual log size in these intakes is huge so getting volume flowing from the beginning is probably better to try keeping from having a major pressure differential.

After sending mine in for flow testing and hearing the numbers, I eliminated the option of using it. Either a set of “header” style intake or true log is the only way I was gonna run that design. I went with the truck style heads and intake instead. But if he figured out fixing the flow issue - that’s great news for everyone else still running that intake that starts pushing for bigger power.

If he didn’t look into that or address it- just know that there is some
Power left on the table you can work on. If you are happy with how it runs then don’t worry- every van, turbo hummer and turbo hmmwv are dealing with it. And bumping to a better turbo will help tremendously.

Please post more pics and use the full size instead of thumbnail. That piece looks awesome!