IMO.......ding ding ding! We have a winner!!! Great explanation! I was reading this post thinking the exact same thing you just posted the whole time. I'm actually glad you said it before i did because you worded it about a million times better than i could've.

Zero R obviously knows what he's talking about too being that he's one of the leading rotary performance parts designer/builder.

I like threads like this......good to see some thinking going on

 

Sold my turbo today and I am going to start building my new header. I cant do a good camparison since I never drove the car with the last turbo. So everyone is of the opinion that a primary dia of 2" and a length of 15"-18" will yeild the best results? Dont know what turbo I am going to run "cant get ZeroR to cantact me" but I have it narrowed down to about three. I'll tell you this tough they will all need one hell of a manifold to hold them up.
Thanks again to everyone for all the input, this has been a very good learning expierence.

 

My experienxce has been that TQ, and HP down low really suffer from a cast manifold compared to a proper tubular 12-14" ELR manifold. If you look at mytop end power it is equal to anyone with the same approximate size turbo. OTOH, I am slower to spool. my set-up is a PT67 .81 P trim with an HKS cast, and a 3.5" DP. I can make 400~ @16, and 500+at 22-23, but CARX7s(12" ELR) set-up spooled way faster. Carl

 

I could see tube header spooling faster than a cast manifold but from what everyone is telling me an even longer primary length "longer than 12" would boost sooner and generate more power at a lower rpm without hurting top end power too much.

 

Within the packaging constraints that every particular application might have, the longer the primaries that can be fit, the better will be the scavenging effect that helps make good low down torque before the turbo starts boosting, and on the same token this will lower the RPMs at which the turbo itself will start boosting, too. I guess that the maximum length for the primaries should not exceed the length of the intake runners themselves (you see now that Mazda made them very long to provide strong “wave-pulse supercharging” [Mazda's own wording, it’s like exhaust scavenging but works the other way around and on the intake’s side] to rise VE at low RPMs from the intake side), but then, at more than 2 feet's length on an FD, it might not be easy to fit primaries that long underhood without resorting to tight turns that might spike up back pressure on their own. As soon as the turbo starts making positive boost, which also makes the exhaust track upstream of the turbine get positive backpressure, all these scavenging effects from the long exhaust primaries and wave-pulse supercharging effects from the long intake runners start to disappear, as VE will now be exponentially risen by the positive boost provided by the turbo. At this stage, what you want is to not add to the backpressure that the turbine itself already provides upstream due to it trying to turn the compressor. For this you have to use primaries' cross sections that are equal or larger in area than the turbine's intake ports, and you actually have to use a larger area cross section at least up to where the wastegate is located to provide good “spillway” for it. So, long primaries do not provide lower back pressure, this is a function of their cross section area and the way its turns are made. 2 more cents.

 

Hoy would this effect the ultimate horsepower potential of the engine?

 

The beauty of boost.....just keep turning it up The long runner design won't negatively affect the ultimate power the car will produce unless you make the runners too small. If that happens then it's choked up and all your doing is creating more heat and less power. Or make the bends too sharp which will also create backpressure and heat.

One point i think people are missing is that tuning header lengths is not the easiest job to do. You really need to have access to a fabricator if you're not one already. Also lot's of R&D time. My exhaust manifold has already been modded 3x and the intake 2x from the picture in my sig. It's never just cut and dry. What works for one might not work for another. You could have a car setup perfectly and change one little thing and all of a sudden be back at square one. TRUST ME ON THAT ONE!

Tuning headers is also for the person that's trying to extract every last possible hp from a motor.....not for the common everyday street car. Small displacement motors need BIG turbos to keep up with the bigger motors. With this they need something that'll lessen the need for lots of nitrous to help spool the big ******. Tuning the intake and exhaust manifold help with this considerably.

 

Spent all day looking for materials to build my header. Trying to decide what to go with 2.130 OD 1.964 ID 14 gage (.083") 321 stainless steel, or 2.250 OD 2.084 ID 14 gage (.083") 321 stainless steel. Found a really neat site that does custom bending of all sizes and types of stainless. Their prices on their in stock bends is pretty cheap but I will have to call them and see how much custom bends are. I plan on going with mild steel flanges to keep expansion to a minimum. Also what kind of effect does a single wastegate have on a devided housing turbine, and what diameter tubeing should I use for the wastgate? Thanks guys!


http://www.woolfaircraft.com/elbow.htm

 

Bump, I would alos liek to know the answers to above question.

Also what are you doing for welding? I know everyone says tig is best but why not mig?

 

Tig is the best for stainless steel. You could use a mig but the problem with it is that you bring the base metal from room temp to melting point instantly. This puts alot of stress into the weld because of the expansion rate of stainless where as a tig you bring the part to melting point more slowly and it heats up a larger area as you weld. I think that if you pre heated the part that you are welding and used a good stainless wire with a 75% 25% argon CO2 sheild gas a mig could do a pretty good job. I am by no means a great welder but this is how I understand it.

 

I would like to say this has been one of the most informative threads I have read on this forum. I'm about to start making a custom manifold and this thread has been a great help. I learned a few things I didn't know about runner lengths and spool time. Keep up the good work and thanks!!!

Silvio

 

Got my new turbo in and I am going to start building my new header now. I have a couple more questions before i start tough.


If you had to choose between equal length and smooth large radius bend witch one would choose. I haven't got the materials yet but just from looking at it I can get one or the other, but not both. The turbo is a divided housing if that makes any difference.

The other question is could the primary length be too long? Common consensus is that from 15" to 18" is best. What would happen if you went over 18"? The reason i ask is that it would be easier to get equal length and smooth bends if it was around 20"-22".

Thanks for the input!

 

If you can fit longer it wont hurt you, I would shoot for equal length and longer over unequal length and smooth bends. I've made 20+" manifolds and it will effect you very little. To jump from 18-20"

-S-

 

I'm just learning TIG, so you say I should start with a small arc and gradually bring the amps by pressing more on the pedal? Any other advise you have would be great.

 

Hey, where are you guys getting your exhaust mani flanges?

 

I think i am going to just get a racing beat flange. I think coated mild steel would be better than stainless because it will expand less and there is not a lot of thermal stress on the flange.

 

Well guys...here we are again. Finally hung my turbo where it needs to be and I have been staring at it for over a week now. I never thought it would be that hard to make a header that was equal length, 15"-18" long primaries, and nice smooth bends. I was wrong!

I have the flanges and decided to go with .083" 321 stainless steel. It is probably overkill but I figure that a little extra now will save me a lot in the long run. I am having a hard time figuring how to build my header without having lots of tight radius bends.

My question is would the tight bends cancel out all the benefits of the longer primary length? I know there is a certain percentage of loss for each bend. Is there a point where this loss would overcome the gains of the longer length?

Thanks
Allen

 

You should essentially need only two bends in front runner looking from your positioning of the turbo. They dont even look like they would be too abrupt. And yes isn't it fun!! Try billing yourself a low $60hr for fab time and see where your at

-S-

 

The pic is kinda deceiving. The front port on the engine is lined up with the rear port on the turbo. If I straight shoot it like that the front primary is only about 8 inches and the rear primary ends up about fifteen inches.

Yeah, you couldn't pay me enough to do this on a car that wasn't mine.

 

Hear is a pic of my manifold after a few thousand miles.
It's made from 1.5" schedule 10 304ss butt weld steel fittings (weld els). The ID is 1.68" and the OD is 1.90". The stuff can be had from mcmaster.com for about $5 per weld el fitting. For straight I went to the local steel yard and bought 3" for $15, also bought some 1/2" flat bar to make the flanges for $30.
As you can see from the dyno chart below the boost starts very early with a TD07 turbo and stock ports.
I think the 1.5" is a bit small but the 2" is a bit big (2.157" ID). I wish there was something in between that could be used.
Runners are 13.5" long and equal length.

 

Has anyone seen or got a set up with the runners between 35 and 40 inches long? I'm keen to see how it has performed and am thinking about building a manifold to do a similar set up on mine. If people are thinking "how on earth can you have runners that long?" easy, put the turbo at the LHF of the engine bay with the compressor facing the LH guard/fender

 

Are there any advantages to running the WG on the turbine housing like setzep did?

 

From what I remember thats what he had to do to control his boost creep. He had his wastegate about halfway down the manifold and had bad boost creep.

 

Crusader is right, the advantage is better boost control. But to be honest I still have a little creep as seen in the dyno chart above. I used to have the wastegate runners exit about 2-3" from the exhaust port and I coulden't control boost worth a damn. Even with the 7.25psi spring it would creep to 17psi on some nights. Now with the WG on the turbine housing it hits ~ 11-12psi.

 

Well, after a long wait i finally got all the stainless to start building my header. If everything goes right this weekend i will start construction on it. I will try to take lots of pics and go through a step by step build. I dont plan on finish welding it until everyone can agree that it is built right.