2001 S4 sedan TECHNICAL exhaust manifold questions.

[kaplow89]

Hello guys, this is my first official post! I've enjoyed reading but just can't find a answer to a specific question I have. First a little background and why I'm confident in what I'm doing. I have the access, knowledge, cash, and equipment to make my own one of a kind exhaust manifold. I'm an NDE Technician (for those who don't know, which I'm assuming will be the majority of you folks) I use ionizing radiation, sound, penetrant, and magnetism to inspect welds for quality. So I want to make my own exhaust manifolds, from scratch. Inspecting the welds so there perfect, heat treating to relieve tension from the stresses of welding. I want to use Inconel 625 material out of 2" SCH 160. So we talking .343" thick. The I.D. measurement is 1.689" or 42.9mm. which is about 4.5 MM larger than the Awe tuning exhaust manifold. My first question is, how much further from the stock manifolds can I poke out from the block? looks like ill need only 1". Will I hit chassis? The K04 exhaust inlet is 40.3mm. Is the I.D diameter to large? Will it compromise performance? Having a larger diameter exhaust being pinched into a slightly smaller exhaust housing going to create gasket sealing problems? I enjoy working with my hands and just find this little project a fun weekend time killer. My plans are still in the works, but my objective is to create high flow manifolds stronger and more reliable than the stockers. (at a cheaper price than what's on the market). Another turbo choice I'm considering is the JHM RS6-RS turbos. I don't have exhaust housing measurements though. Thanks guys!

[Bordom]

Interesting. If this takes off, I'll buy a pair off you lol

Everything graciously mispelled by Android

[Monty23]

If you are going to take the time to build quality exhaust manifolds, then why not go with a non chinese QC controlled turbos like Garrett, Tial, Xona, BW?

Also, you are much better off taking the measurements on your car with your hardware, as slight differences in engine/trans mounts or the manufacturing tolerance of various parts may make more/less clearance for your car vs. someone else's car.

[QuinnsterKID]

This goes way beyond my knowledge, but I am curious to see what others input will be.

[wbrunner23]

bigger is not always better - exhaust velocity plays a role as well

I'm sure you know this. Your weekend project is going to require you pull your motor in-and-out to mock up and check clearances. Quite an under taking but the challenge will be fun.

I too would like to make my own manifolds one day for some side mount twins (replace ABS w/ prop valve and relocate intake to battery tray like the Audi TT w/ a 2.7t). But I am nowhere near ready to take it on just yet.

[kaplow89]

Interesting. If this takes off, I'll buy a pair off you lol

Everything graciously mispelled by Android

Haha, because I do it for a living I'll get it for free, but the inspection and heat treating alone is the price of cast high flow manifolds. If you wanted to just buy a pair, without doing the math with everything included it would be the price of a nice pair of turbos lol.

[kaplow89]

If you are going to take the time to build quality exhaust manifolds, then why not go with a non chinese QC controlled turbos like Garrett, Tial, Xona, BW?

Also, you are much better off taking the measurements on your car with your hardware, as slight differences in engine/trans mounts or the manufacturing tolerance of various parts may make more/less clearance for your car vs. someone else's car.

I wouldn't mind the idea of a 605 setup. I just don't want that lag, and 400whp is my goal mainly.

[kaplow89]

bigger is not always better - exhaust velocity plays a role as well

I'm sure you know this. Your weekend project is going to require you pull your motor in-and-out to mock up and check clearances. Quite an under taking but the challenge will be fun.

I too would like to make my own manifolds one day for some side mount twins (replace ABS w/ prop valve and relocate intake to battery tray like the Audi TT w/ a 2.7t). But I am nowhere near ready to take it on just yet.

As far as I understand the velocity will be bottlenecked by the turbo so just as long as the piping going to the exhaust turbine housing is smaller than the inlet I should be okay? (Please correct me if I'm wrong)

[JVD]

Best to pull the motor, remove manifolds/turbos, re-install motor and mock up that way.

[Monty23]

I wouldn't mind the idea of a 605 setup. I just don't want that lag, and 400whp is my goal mainly.

400 whp sounds good while your at 275whp (stage 2), but once you get to 400whp you will quickly get bored of it. I completely understand the lag dilema though. However, the stock manifolds are very well built and have been used for 600+whp in many builds. It just seems like a lot work for not much gain over the stock components and at very moderate power levels. But at least you won't have to worry about your block cracking.

[JVD]

I would just go single if you're going to these lengths.

[Monty23]

I would just go single if you're going to these lengths.

I keep mixing you up with J2R...

And I agree, but its slippery slope from a $$$ perspective. But I still thinks its worth it if you can swing it.

[MacDaddy]

Fwiw, the rs4 exhaust ports on the head are smaller than the s4's, reference to rs4 training guide pdf.

I don't think the diameter is the problem but that OEM is basically a log manifold and doesn't flow as smoothly as an equal length header would.

[Audi9]

Fwiw, the rs4 exhaust ports on the head are smaller than the s4's, reference to rs4 training guide pdf.

I don't think the diameter is the problem but that OEM is basically a log manifold and doesn't flow as smoothly as an equal length header would.

If the F1 world has taught us anything, it's that a "log style" manifold is actually quite beneficial in a turbo application where the name of the game is trying to retain as much heat as possible in the exhaust to keep up velocity. In an equal length header you lose some heat because you're separating each cylinders exhaust gasses until the merge.

[jimmer009]

I made my own manifolds. I used blanks from the net and then bent and milled out 2 inch pipe. But the stock manifold is way restricte. But there is a lot of room for headers. But single turbo is cool fyi. There not the best but they work and flow great

[jimmer009]

I'm single turbo so there is a cross over pipe and the turbo sits on there to

[Schtug]

I'm single turbo so there is a cross over pipe and the turbo sits on there to

Is what I'm seeing there for real? Or is this some more of the audi enthusiast humor I'm not quite used to yet?

[jimmer009]

These are on my car and working well. It's all MIG welded. I don't have a tig. They work great. But if you don't like them I'm sorry to hear.

[Schtug]

These are on my car and working well. It's all MIG welded. I don't have a tig. They work great. But if you don't like them I'm sorry to hear.

If you put the time and energy into fabbing those up and they work for you then that's awesome in my book. They're a little unorthodox compared to what most of us are trained to see in terms of motorsports fab work which is what threw me off a little.

Looks like they are constructed from 16 gauge tubing? Are they supporting the weight of the turbo or did you make up some bracketry to take the stress off of them?

[jimmer009]

Thanks I should if done more research first. As 2.8 manis would of got me the same results. The pipe used is very good quality. I'm not sure any more on the gauge. But it holds the hx35 on its own. I'm sure there are people that could do better. But you can't look down on me because I don't want to buy bolt on parts. I like making my own parts. It's a hobby and enjoy it.

Back on topic I should of explained a little better. The frame rails sit way low to the headers. The angle of the heads give you plenty of room in there. And I made my own set up from scratch with out pulling the motor.

[Schtug]

I'm sure there are people that could do better. But you can't look down on me because I don't want to buy bolt on parts. I like making my own parts. It's a hobby and enjoy it.

I'm looking dead eye level with you because even though you didn't have the ideal tools to do the job you damn sure didn't let that get in your way. I'm lucky to have a business that lets me feed the fabrication addiction pretty regularly. Working on a twin gt28rs setup right now and it has been quite a project so far. That's neither here nor there though so I should probably stop with the cluttering up of this thread. Back to the regularly scheduled programming. Lol

[somedude]

I wouldn't mind the idea of a 605 setup. I just don't want that lag, and 400whp is my goal mainly.

what you just described is every stage 3 build out there. throw a set of ko4's at 22-24psi, upgrade your injectors, maf, downpipes, clutch, and BAM 400whp with only a few hundred rpm more lag than stock. The reason you don't see a lot of custom manifold's for these cars is simple. The OEM ones work very well. I am all about seeing a cool project or build but you are talking about a very significant amount of labor for little to no gain. There are quite a few very good aftermarket options for manifolds if you want to go that route. Wagner has a very nice set of cast manifolds. If you are going through the work to make manifolds you should really reconsider having a higher goal for power but just know how quickly that price tag gets once you get over 430 or so whp

[MacDaddy]

If the F1 world has taught us anything, it's that a "log style" manifold is actually quite beneficial in a turbo application where the name of the game is trying to retain as much heat as possible in the exhaust to keep up velocity. In an equal length header you lose some heat because you're separating each cylinders exhaust gasses until the merge.

I haven't seen a single f1 turbo engine, either past era or current, that runs a log style exhaust manifold. I even did a google image search and couldn't find one. Not even the Indianapolis turbo engine.

[Audi9]

I haven't seen a single f1 turbo engine, either past era or current, that runs a log style exhaust manifold. I even did a google image search and couldn't find one. Not even the Indianapolis turbo engine.

After a two second search......

http://www.enginelabs.com/news/merce...he-year-award/

[MacDaddy]

One example out of what may as well be a billion, good job.

[wbrunner23]

One example out of what may as well be a billion, good job.

Log manifold gets the advantage when it comes to space. They can't perform that bad by comparison if they're preferred (at least by some teams) over other options at that level of motorsport.

You're Canadian, MacDaddy, be nice

[Audi9]

One example out of what may as well be a billion, good job.

It is when that example completely dominated every other engine/team on the track

[Corbett]

Didn't burning coals show a loss in spool and no power gain with log manifolds?

[slow ride]

Too large of runner will kill it for spool. 400+ inch v8 guys making 1500-2000 hp have runners around 1.75" in turbo application. Don't get crazy here as the volume of the turbine is still the major choke point. Stick close to the exhaust port size and do a nice merge setup.

In the ls1 world guys have made 1500+ with truck manifolds flipped forward if that tells you anything. I like the stock Audi log manifolds with the air gap design. While not perfect they are damn good at keeping in heat, reliability and spool.

[MacDaddy]

It is when that example completely dominated every other engine/team on the track

And the bmw turbo of the 80's dominated then with equal length manifold, you have an example of one engine in f1 history not a definitive conclusion.

Log manifolds can perform well, but a properly engineered equal length header will perform better. Also f1 has a myriad of regulations and Mercedes was doing well before turbos. To somehow imply all their success hinged on log manifolds is silly.

[Eurotuned_A4]

what you just described is every stage 3 build out there. throw a set of ko4's at 22-24psi, upgrade your injectors, maf, downpipes, clutch, and BAM 400whp with only a few hundred rpm more lag than stock. The reason you don't see a lot of custom manifold's for these cars is simple. The OEM ones work very well. I am all about seeing a cool project or build but you are talking about a very significant amount of labor for little to no gain. There are quite a few very good aftermarket options for manifolds if you want to go that route. Wagner has a very nice set of cast manifolds. If you are going through the work to make manifolds you should really reconsider having a higher goal for power but just know how quickly that price tag gets once you get over 430 or so whp

He has the tools, knowledge, and skill to make his own at what I'm assuming isn't much cost besides material and his time. So the $1750 Wagners don't make much sense for him I'm assuming. Maybe Im wrong, but that's what I get from it. At the stated power goal though, I would just retain stock manifolds.

[kaplow89]

Well sorry for the long delay guys, works got me going pretty good. While I completely agree with you guys with my conservative power goals, what i'm really interested in is having the power I want with STOCK lag, or maybe even better. I have a work truck and a place to store the s4 so ill be in no hurry when the motor is out. If I get little gains, or gains not worth all the effort I'm putting into it that's cool with me. I enjoy fab work, so if i can do something i enjoy and have my s4 benefit from it then why not huh? Plus it would be cool to show all you folks with the finished product is, and maybe do some before and after logs as well.

[Bordom]

updates?