Alright, in light of Art's new modo of "more tech", i've decided to give my first shot at a real "tech" thread. What will follow is my best effort at describing the theory behind turbo exhaust manifold design. Hopefully this will keep the "DRAG VS. LOVEFAB!?" threads to a minimum. Disclaimer: I am not a professional. Don't be too critical.

ok, so here we go...

<U>1. The Purpose of the Exhaust Manifold:</U>
The purpose of any turbo exhaust manifold is to direct the exhaust gases from the engine into the exhaust side of the turbocharger. These gases flowing into the turbo is what spins the turbine and hence creates boost. Clearly, the way in which gases enter the turbo have a large effect on how efficiently the turbo is spooled up. That is why understanding manifold design is important to anybody hoping to piece together a kit. And that is what will be discussed right now.

<U>2. Exhaust from the Engine</U>
Ok, well... every time a cylinder in an engine fires, there is waste gas left over. These gases flow through the head and out the exhaust ports into the exhaust manifold. Although cylinders are firing very rapidly, there is a pattern to how they fire, and hence there is also a pattern to how the gases enter the manifold. Below is a diagram of the order in which cylinders fire. I know this is the gsr firing order and I think it's the same for all honda 4 cyl. ):



From the image, you can see the order in which exhaust gases are entering the manifold. Keep this is mind for the next sections.

<U>3. Gases in the Manifold</U>
So now the gases are inside the manifold, where our primary concern lies. Our goal is to have the exhaust gases leaving the manifold with as much energy as possible (so it will spool the turbo more efficiently). The way to do this is to let the gas keep its momentum going through the runners. This means no sharp turns and no interference between runners. The reason to avoid sharp turns is obvious, the gas will lose momentum because it will slow down when going around the turn. As for the interference between runners, this is something that isn't so obvious. From the last section, you know that exhaust gases are entering the manifold in each runner at different times. The gases come in "spurts" right after the cylinder fires, it is not a continuous flow in each runner. So knowing this, I think an example will be the best way to describe what is going on:



Pictured above is the Lovefab Shorty exhaust manifold. This is an example of what is called a "log" manifold. From this, it is easy to trace the routes of the exhaust gases from the engine though the manifold. Remember, the gases will come first from the far right runner, then the second from the left, then the far left, and finally the second from the right. Now, as you trace the routes of the gases, pay attention to any interference there might be between "spurts" of gas from different runners. Right off the bat, the far right cylinder fires first, and then the second from the left right after. What happens if the gas from the first firing cylinder gets to the turbocharger right after the second cylinder fires? Interference. The gases from the second cylinder will collide with the gas from the first cylinder and, therefore, both "spurts" of gas will lose momentum (and decrease efficiency). Also, notice the 90 degree turn for the gases to take when leaving the manifold and entering the turbo. This will lose momentum because remember (sharp turns are bad!). Now with this being said, I don't want to make you think that the shorty is a bad manifold. It is a great manifold (especially for the 300 it costs) and will work very well for many setups. This is all just to show what is going on.

Now another example, the lovefab SST:




I realize this one is a little harder to trace through, but with both pictures I think you can manage . Ok, so this mani is quite different from our last example. This is what is called a tubular, equal-length manifold because each of the runners are made to be the exact same length as the others. I hope by tracing through the routes of the gases you can notice the advantage of equal length runners. One advantage is that the gases will have virtually no interference with eachother. This is because the gases from each cylinder will take the same amount of time to reach the flange (exit) of the manifold. Remember, cylinders fire at different times, so if they take the same amount of time to get to the exit, they will arrive at the exit in the same interval as each fires. This means more momentum for each burst of gas (and better spool). Now, you may think "but the gases have to travel further now!?!?". You're right, they do. But think about it. After the first burst of gas, this will not matter because the interval of bursts will be the same. The more efficient design of equal-length heavily outweighs the disadvantage of the very first burst taking a fraction of a second longer to reach the exit. Another thing to notice about this manifold is the "tubular" part. Look at the exit of the manifold where the gases enter the turbo. There is no sharp turn to take like there is in the shorty. This again means more efficient spool because the gases will be "pushed" out with the momentum they have instead of having to turn and lose momentum. The SST is a very sexy manifold and will suite the needs of pretty much any turbo honda.

Alright, well it's finally over . Maybe now you have the magic power guys like Art have to judge a manifold simply on the way it looks. I hope to continue this by discussing wastegate placement and "log vs. equal-length" (which we really already went over, but incase anybody wants specific info on that) sometime later, but for now... I'm going to bed.


Modified by zomart at 12:52 PM 1/31/2004

 

rofl, I just noticed that SideWinder was in the shorty picture. Oh well, new site is due soon!
Good Write-up zomart, explains things in leihman terms

 

very informative write up

 

Awesome post!!! Good for your for sticking your neck out and making an informative post for everyone to bounce ideas around in and brainstorm.

I hope to see more of these in the future from you guys...we want to learn we want to learn!

 

I got a question. I'm not sure if Natural Aspirated Header design can be useful in a turbo application. But if you follow the principle of exhaust gas velocities and inertia, it would be only logical to bring up the infamous scavenging affect of a Naturally Aspirated header. I know that unlike a traditional Naturally Aspirated Header, a Turbo Exhaust Manifold must have some sort of 4-1 collector that the Turbine attaches to. With that said, why not ditch the "Equal Length Design" and instead develop different lengths for different runners. With the engine firing in the 1-3-4-2 setup you can have runners 1 at the shortest length, number 3 with a tad longer length and so on. With this effect, it'll help pull exhaust gases for the next cylinder and thus increase the momentum/inertia of the exhaust energy. Why wouldn't this work in a turbo application?

 

great write up

 

thanks guys! i thought i had embarrased myself after nobody replied for the first couple of days . thanks for the support. wastegate placement should be coming soon .

 

Took a few days to sink in hehe...great post!

 

bump

 

len, this might help answer your questions http://www.turboford.org/cgi-b...17369

 

where the hell did this come from? lol


its 1 3 4 2


Theres a few things missing, but its a good attempt, nice job


just looks like a big lovefab advertisement though

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase &raquo;</TD></TR><TR><TD CLASS="quote">

where the hell did this come from?


its 1 3 4 2
</TD></TR></TABLE>

PWNED!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase &raquo;</TD></TR><TR><TD CLASS="quote">

where the hell did this come from? lol


its 1 3 4 2


Theres a few things missing, but its a good attempt, nice job


just looks like a big lovefab advertisement though </TD></TR></TABLE>

1 3 4 2 is the cylinder numbers from the front of the engine. my image is the order they fire in. cylinder 1 (farthest right) fires first. cylinder 3 (second from left) fires second - that's why i have it labeled two. cylinder 4 (farthest left) fires 3rd - that's why i have it labeled 3. cylinder 2 (second from right) fires 4th - that's why i have it labeled 4. it's right.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by zomart &raquo;</TD></TR><TR><TD CLASS="quote">

1 3 4 2 is the cylinder numbers from the front of the engine. </TD></TR></TABLE>

No, 1 3 4 2 is the firing order.

Cylinder Order (From LEFT to RIGHT ) is 1 2 3 4

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by zomart &raquo;</TD></TR><TR><TD CLASS="quote">
my image is the order they fire in. cylinder 1 (farthest right) fires first. cylinder 3 (second from left) fires second - that's why i have it labeled two. cylinder 4 (farthest left) fires 3rd - that's why i have it labeled 3. cylinder 2 (second from right) fires 4th - that's why i have it labeled 4. it's right. </TD></TR></TABLE>


IMO thats a bad way to explain it, but i get what you are saying now. you're going to confuse people lol

 

i thought cylinders were numbered 1 2 3 4 from right to left... then again, that's according to my haynes manual . so my image is backwards then. when i said 1 3 4 2 is the cylinder numbers from the front of the engine, i meant that's the firing order in terms of the 1 2 3 4 cylinder numbers. my image doesn't use the 1 2 3 4 numbering at all. it's only supposed to show what order they fire in.

edit: read my disclaimer!

 

BLAH!

let me freakin draw it out for you

--------------
| 4 3 2 1 | &lt;----- Engine
--------------
l l
Front of car

Firing Order is Cylinder 1,3,4,2

but hey, i praise you for trying

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase &raquo;</TD></TR><TR><TD CLASS="quote">BLAH!

let me freakin draw it out for you

--------------
| 4 3 2 1 | &lt;----- Engine
--------------
l l
Front of car

Firing Order is Cylinder 1,3,4,2</TD></TR></TABLE>

lol, we're both right. it's just the way that i numbered the cylinders.



i'll try to be clear:
the cylinder labeled 1 means: this cylinder fires 1st.
the cylinder labeled 2 means: this cylinder fires 2nd (even though it is the 3rd cylinder).
the cylinder labeled 3 means: this cylinder fires 3rd (even though it is the 4th cylinder).
the cylinder labeled 4 means: this cylinder fires 4th (even though it is the 2nd cylinder).

so you're saying the same thing i am, just in a different way.

i'm not trying to say "no way am i wrong", but i don't want other people to get confused. no hard feelings man .

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by zomart &raquo;</TD></TR><TR><TD CLASS="quote">

lol, we're both right. it's just the way that i numbered the cylinders.



i'll try to be clear:
the cylinder labeled 1 means: this cylinder fires 1st.
the cylinder labeled 2 means: this cylinder fires 2nd (even though it is the 3rd cylinder).
the cylinder labeled 3 means: this cylinder fires 3rd (even though it is the 4th cylinder).
the cylinder labeled 4 means: this cylinder fires 4th (even though it is the 2nd cylinder).

so you're saying the same thing i am, just in a different way.

i'm not trying to say "no way am i wrong", but i don't want other people to get confused. no hard feelings man .</TD></TR></TABLE>
your both saying the same thing

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by len &raquo;</TD></TR><TR><TD CLASS="quote">I got a question. I'm not sure if Natural Aspirated Header design can be useful in a turbo application. But if you follow the principle of exhaust gas velocities and inertia, it would be only logical to bring up the infamous scavenging affect of a Naturally Aspirated header. I know that unlike a traditional Naturally Aspirated Header, a Turbo Exhaust Manifold must have some sort of 4-1 collector that the Turbine attaches to. With that said, why not ditch the "Equal Length Design" and instead develop different lengths for different runners. With the engine firing in the 1-3-4-2 setup you can have runners 1 at the shortest length, number 3 with a tad longer length and so on. With this effect, it'll help pull exhaust gases for the next cylinder and thus increase the momentum/inertia of the exhaust energy. Why wouldn't this work in a turbo application?</TD></TR></TABLE>

equal-length does what you are suggesting (i think ). the cylinders fire at different times, so there is no need to have the runners for cylinders that fire later be longer because there will still be that time interval between each fire. also, think about when the cycle repeats. the longer runner for the last cylinder to fire might cause problems when the first cylinder fires again as the first runner is shorter.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Sohc Driver &raquo;</TD></TR><TR><TD CLASS="quote">
your both saying the same thing</TD></TR></TABLE>

heh, thanks man .

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase &raquo;</TD></TR><TR><TD CLASS="quote">


just looks like a big lovefab advertisement though </TD></TR></TABLE>
Id like to see a Full-Race log manifold to compare it to!
I think he just used it for easy comparison Mase...

 

If you want to make a good turbo manifold, look at all of tinkers unique manifold designs (yes yes, i kno they are hard to find, so look hard!), then do the exact opposite!

 

I have been breaking my neck trying to find it, but does anyone remember the manifold that was on ebay, that was CNC billet/aluminium, had VERY short, direct runners? It also had a mustang stamped on it. I think the idea behind that design was to make additional use of the exhaust pulses. If anyone can provide a link, I think it would make a nice addition to this thread.
-PHiZ

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase &raquo;</TD></TR><TR><TD CLASS="quote">just looks like a big lovefab advertisement though </TD></TR></TABLE>

Don't get your panties in such a wad Steve. It's a good thread. Very informative.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by len &raquo;</TD></TR><TR><TD CLASS="quote">

Don't get your panties in such a wad Steve. </TD></TR></TABLE>


when it happens over and over again, it gets ******* annoying. thats all.