Twin Scroll Turbo Manifold question

[Ghetto_CB7]

Hey guys, a friend of mine had someone in town build him a turbo manifold, well I just saw the first pictures of it mocked up today and I think there may be some problems.

So I am looking for some advice and insight from some of the turbo guys, especially those with fabrication experience.

So it is an h22 manifold for an hx35 using a split flange.

Now I thought the manifold should have runners 1 and 4 together and then runners 2 and 3 together, but he does not.

Another one of my concerns is that none of the runners seem to be the same length, especially number 3 which seems REALLY long.



It looks like runner 3 and 4 are much longer than 1 and 2, Just curious as to what you guys think of it.

[blazenem]

wish i had answeres for you...im sure some of the more knowledgeable member will chime in...i would like to know how much they charged him for the fab work?

[Ghetto_CB7]

Price

I can get a price, I don't think it was a lot, but if the manifold doesn't work its not worth it.

The fab work looks like it will be good though, the guy is a really good welder.

[blazenem]

yeah as long as it works right lol

[h22sparkle]

One thing I have noticed about ram-horn manifolds of equal length will it fit with the clearance of the turbo at the same time pass through the crossbar of the cb7?

I remember when I had this I had fittament issues with it when I ran one from my peakboost manifold?

[Ghetto_CB7]

DC teg

Well, the manifold is going into an HtoB dc teg, and has been mocked up on that car, so I am fairly sure it will fit.

However if it is built wrong its not worth it lol.

[Ghetto_CB7]

bump

Ttyl8r

[98vtec]

the runner pairing is fine. You typiucally run the pipes in the order of the firing order: 1, 3, 4, 2. This creates a "swirl" after the collector if the rest of the manifold is built correctly which increases velocity. The 1 and 4 lengths are pretty weird but im not going to say it wont get the job done.

[Ghetto_CB7]

Explain

Can you explain how, or why running 13 and 24 will create a swirl.

Or do you have any sources that explain it.

To me it doesn't seem like there is much room after the collector to create a swirl, since it goes directly into the turbine housing. Also why wouldn't a 14,23 pairing create a swirl.

To me it makes more sense to have the 14 23 pairing based on what I have read. The separation of the flange is supposed to provide more time for the first exhaust pulse to get out of the way of the next pulse, reducing back pressure and increasing efficiency.

Please if you have any documentation post a link or let me know where I can find it.

[dbsharp]

The manifold will work. I wouldn't build it like that but it will get the job done.

[bruno8747]

Looks like it will crack to be honest. No bevel ends? Cant tell if its pipe or tube

[Gtseviper]

Looks like it will crack to be honest. No bevel ends? Cant tell if its pipe or tube

is it because the welds would not penetrate as good as if there was bevel ends..causing it to crack from weak points

[bruno8747]

is it because the welds would not penetrate as good as if there was bevel ends..causing it to crack from weak points

Yes, If its sch 10 atleast it should be beveled before welding. Butt welds like that will fail over time.

[F22Turbo702]

To me it makes more sense to have the 14 23 pairing based on what I have read. The separation of the flange is supposed to provide more time for the first exhaust pulse to get out of the way of the next pulse, reducing back pressure and increasing efficiency.

I agree, pairing of cylinders should be 1/4 and 2/3. This manifold is not setup correctly, I suppose it won't hurt anything, however it's not going to produce the desired effects.

[Saidaigen8]

As for your questions about the length of runners is concerned...youd have to know the firing order and degrees of difference between each spark. Each time the spark fires and the exhaust valve opens and closes, there is a high pressure "pulse" of exhaust gases that flow through the manifold. Behind each one of these pulses is an area of low pressure. As we all know physical science, high pressure areas will suck towards a low pressure area. An equal length runner simply combines the runners in a way that the low pressure area behind each pulse will pull the next pulse along at a higher speeds. This increases speed exponentially. First, the pulses move faster towards the lower pressure area which increases velocity, then it overtakes the low pressure area slams into the next pulse...thus increasing its velocity even more. This also means that the runners couldnt be equal length. They would have to be spaced where each pulse will reach the next one at a specific time. This is where the money and R&D come into play.

Older turbo F1 and Group B rally cars were really the onle people to ever perfect this design. Now its basically used to keep the gases that are closest in speed together until they are combined in the turbine housing. Because of this, the pairing of cylinders and length of the runners arent as important. Most people just stagger the cylinders by firing order these days. You can still get great results from it, but dont expect the results that F1 cars got. The amount of time and money needed to properly design and build a setup like theirs would be astronomical...like 15-20 times what your car is worth lol

By "closest in speed" i meant that youd want to stagger each runner to each bank on the manifold by firing order. Alot of people will put cyl1 on bank one and cyl2 on bank 2, then cyl3 on bank one and cyl4 on bank two, etc.. You do this to keep the positive pressure between both banks on the manifold equal(at the each collector and entering the turbine), as well as having an equal amount of backpressure at each bank of the motor. You want the pressure to be the same on each bank of runners so that each wg will operate in perfect unison and you wont have boost spikes or erratic transient response. Again, this isnt how it was designed to be done, but its the easiest way to get some of the benefits of twin scroll without all the expensive R&D. Also, when doing this youll want to keep each set of runners as close to the same length as possible. There can, and will be a small difference in length between each bank, but as long as its not a huge difference there shouldnt be any major drawbacks.

Without extensive R&D and some amazing math and physics skills, itll be damn near impossible to make a true twin scroll setup the way it was designed to work. However, its been proven many times that doing it how i mentioned earlier will make a good difference...especially on a larger motor with a large turbo

Pair em 1-3/ 2-4