GI: Replacement exhaust manifold

[StealthWyvern]

looking like that bolt under the short pipe is going to be a PITA now.

ooo didnt think about that... tolorerances look super tight to get bolts through the flange.

thomas, have you tought to check the clearances on putting bolts through that bottom flange? I know you have them so you can actually see how tight everything is compared to just looking at pictures.

 

[speedpx]

Not 100% sure if I like the looks of the new routing to be honest but I want to wait and see how he manages the EWG portion to really comment to much.

+1 I like better the first prototype

 

[thepope540]

So the ewg will be right there on the mani? I know that sounds dumb. But I mean like no pipe off the mani to the ewg? Like to move it right off the mani? Looks good though

The bung on the front is for the O2 sensor. The EWG port doesn't have a tube on it yet, but it comes out of the collector running parallel to the number 1 runner and then makes a 90 degree turn to put the wastegate facing forward almost next to the flange and right above the turbo.

Not 100% sure if I like the looks of the new routing to be honest but I want to wait and see how he manages the EWG portion to really comment to much.

The first prototype is a better looking part - I agree wholeheartedly. The trouble is the debate between form and function. I would love to have equal length runners and the new design is closer to accomplishing that. The only ways to have truly equal length would be to either route the pipes all over each other with a ton of unneeded bends (which will counter act some of the benefit of equal length) or to reposition the turbo. Runners 1-3 on the first manifold aren't too bad, but there isn't any way to get #4 close - it is either half the length of the others or almost double the length and hanging off the side. That's why I rerouted 3 and 4. It isn't as pretty, but it gets all the runners closer to the same length.

So the question is: Do you (the buyers) want a better looking part or a potentially better designed part? I'm going to hold off working on this for a day or two while this question gets answered. I'm not interested in offering two different designs, but I'm happy to move forward with either layout.

looking like that bolt under the short pipe is going to be a PITA now.

The original prototype was laid out with ease of install being a priority, the second iteration was organized for closer to equal length. As a result the #3 runner is going to be a bit of a pain, but it is easily solved with a stud and nut rather than using a bolt. Its hard to tell from the pics, but there is about 3/8" between the runner and the flange so a nut wouldn't be a problem at all.

 

[2.0t03speed]

really you arent too far off with your first iteration. Just loop runner number 4 and bam =D

 

[SeR_Cyclops]

MAM knew how to make some awesome manifolds.....

 

[speedpx]

Just need runner # 4, here some help

 

[highflyin285]

i like both designs personally

 

[thepope540]

The trouble with a lot of the pics people are posting is that the MAM manifolds are filled with unnecessary bends and a lot of extra length. The best manifold will direct air from the head to the turbo using the most direct path. There are several reasons to avoid bends and length:

1. Every bend disturbs the air flow - more bends, more disturbance. This causes flow reversions and eddy currents that will result in the engine having to work harder to push the air out and less energy getting to the turbo.
2. Bends result in hot spots in the manifold. Hot spots form due to the disturbances in air flow mentioned above. Every bit of heat lost is that much less energy being put into the turbo. Hot spots also result in cracking.
3. Unneeded length allows for more heat to be lost as the air has a longer path to take.
4. Extra length also results in higher EGTs which are hard on everything.
5. More manifold means more weight and weight is a bummer.
6. The more involved the manifold is the more difficult it will be to install.

The MAM parts are well made, look great, and have proven to flow well, but they have some short comings I'm not interested in copying. I've been rereading info from my turbo library (books like Maximum Boost, Turbo, and Supercharged!) for real info on the value of true equal length runners. The reality is that equal length runners aren't even mentioned. Conventional wisdom says that they are the way to go, and I would argue for them on an NA setup, but I'm beginning to wonder if they really matter too much with a turbo. The WRX is the only car I can think of where there is practical knowledge on the subject. They have very unequal length runners and this results in the Scooby rumble. After about an hour of reading I found this: Speed Style and Sound Header Comparison There was surprisingly no discernable difference between equal length and unequal and this is on a car where the difference in runner length is measured in feet.

Final thoughts: After the last several hours of research and reading I believe that a difference of ~4" in runner length is completely negligible and if people like the look of the first iteration manifold thats what should be built.

 

[2.0t03speed]

Then its settled good looks it is

 

[StealthWyvern]

Sorry wasn't trying to start a debate. Personally I love the first setup you did plus it looks like it will less likely be a pita to install but I do like how you managed to get the pipes to fit the oval portion of the head flange on the 2nd one. From what you have mentioned it looks like the first one will also be less prone to cracking which is a major plus in my book

 

[SCMP3]

im don for whatever you make as long as its ewg

 

[jdwk]

Just make it as durable as possible. The small difference in runner length is not going to make a big enough difference in response or power with this engine to matter. If my stock manifold does ever crack, I just want something that won't break.

 

[Cleverfrog]

Good info. Now you can really tell it's going to be a great manifold!

 

[jbrewer4639]

I could Cate less what it looks like I just want it to do it's job well and last.

 

[Cleverfrog]

i couldn't care less what it looks like i just want it to do it's job well and last.

 

[chwood]

sub...

 

[jbrewer4639]

thanks that's why I need to post on my computer more.

 

[Cleverfrog]

@ Pope: Could you possibly add a straight pipe piece on #3 to lengthen the runner? Maybe an inch long to push the runner away from the flange and turn the 90-45 whatever it is to compensate?

 

[thepope540]

@ Pope: Could you possibly add a straight pipe piece on #3 to lengthen the runner? Maybe an inch long to push the runner away from the flange and turn the 90-45 whatever it is to compensate?

I would if I could. I've spent 10-15 hours just trying to route that runner for another inch or two - it just can't be done. I can add 10-12 inches and make a mess of it, but a short extension just won't fit. The short ~4" runner is the only way to go.

 

[Cleverfrog]

I would if I could. I've spent 10-15 hours just trying to route that runner for another inch or two - it just can't be done. I can add 10-12 inches and make a mess of it, but a short extension just won't fit. The short ~4" runner is the only way to go.

At least you tried. Can't wait to hear what it sounds like.