Exhaust

B6 A4
#41

What’s funny is indeed these small things do add up for any car. I’m just an armchair enthusiast and I do not claim in any way to be any sort of expert, but it’s obvious the JHM way is to make sure the small things are right (like X vs H pipe) so when the big things (supercharged/turbo/boost) come along, their full potential can be realised.

For that 10 sec B5, I’m willing to bet there’s a ton of small things, as well as the headline grabbing turbos and tune, that JHM have done that “the others” ignored.

Look at the B6/7 platform and all the well sorted neat little things we can get - LW crank pulley, LW rotors, LWFW and the list goes on. I’m sure the same goodness for the A4 is coming, lots of small things that add up to a lot.

#42

What I don’t think most people realize is 8 small things quickly turns into ONE REAL BIG Result. Most stuff like X pipes and stuff that might be considered smaller really starts to support other systems.

If you build a proper exhaust system. It will make a larger impact on your intake system. As the exhaust can actually help pull air into the motor when built right.

#43

I’d like to sum up specifications for everything to confirm things for myself and anyone else on here that has any questions.

The best setup right now for exhaust would be;

1- Starting at the headers, check to see what size they are, IIRC they would be either the ones off the B5 S4 which are the larger, or they would be a smaller set.
2- JHM downpipes which are 2.5" if I am correct.
3- B6 S4 exhaust which is 2.5"
4- X pipe
5- New rear O2 sensors

Can someone please confirm if these are the correct specifications for a proper 3.0 upgraded exhaust system

#44

1 is the only one that needs to be ommited. The B5 manifolds are turbo manifolds so they won’t work on your car. From what I gathered there are two manifolds for the 3.0 the large port and the small port. Niether one is better then the other one when you consider that you can open up the smaller ones

#45

i dont know why i forgot that the B5 were turbo manifolds. For some reason I thought I read someone say they were same as ones off a B5 and for some reason I stuck S4 with it. lol my bad. I wish I could remember where I read that so I dont feel like such an idiot.

#46

Lol it’s all good. That idea was speculated on here somewhere earlier last year, I recall it too.

That being said… that information above is theoretically correct, but I don’t think it’s confirmed until JHM comes forward with their test results.

#47

rear O2’s are really only used for long term fuel trim adjustments and making sure the cats are functioning properly, the front O2’s are much more critical for calculating mixture and everything else.

#48

http://i1108.photobucket.com/albums/h411/halo549b/Dyno1.jpg

I would like to see it this was the same size pipe or the H pipe was a amaller diameter?

Also I would like to do a volumetric test to see if both are displacing the same ammount of air.
Or does the H pipe test suffer from too much back preasure?

#49

the explanation I’ve always heard is that the H pipes seem to get overwhelmed so to speak at higher RPM, they dont force the scavenging like an X and lose that extra vacuum effect.

I had posted results from a domestic mag that did a test with H, X and no crossover on another site. The X was the clear winner, it was quietest and made the most power, the exhaust was unchanged besides the midpipe and there were no other chnages to the car, just the crossover.

#50

considering these cars are 4.2L of displacement or 3.0 (neither of which is big) you’d think they’d manage, but we can’t forget they rev to 7000 and 8000 rpm…thus beemer’s point about high RPMs is most pertinent (especially compared with older domestic cars that this testing stuff is often from, which often have much lower redlines).

#51

The X pipe is good for high hp/tq big displacment motors. they push a large amount of air and they don’t generally use high rpm. Most domestic cars did well with the H when revved to the lower rpms. say like a 454 that revs to 5500.

if you look the X pipe starts to make its move right at peak Tq. 3500rpm and it becomes more usefull the higher the rpms climb

#52

Has anyone thought of doing ceramic coated exhaust system? Does anyone think it would be worth it to do something like that on a 3.0, Or would it be better to just wrap the headers and DP’s? I was thinking since our cars are V6 it would be twice as benifical to do some kind of heat coated treatment or something to help with that but I’m a newb so i don’t know much about this, anyone?

#53

I will be wrapping my SS headers and downpipes with exhaust wrap, I might check out how much ceramic coating costs, if it isn’t that exspensive I will go that route.

Are you planning on getting a set of headers a43go6mt

#54

I think I’m just going to run DP’s and S4 exhaust for now. I was kinda curious what the measurements on the stock headers were? becuase I dont see any point in doing all 2.5" from DP’s back and having the headers be something different. And I was kinda assuming JHM would make some if it was needed and in that case I probably would depending on what they sounded like. I’m really picky about exhaust tone.

Also I’m wondering if in fact header size changes, then I’m assuming intake would need resize to match??

#55

Thats a very valid way of thinking.

Ok depending on what the build date your car is will determine what exhaust manifolds you have

http://audirevolution.net/addons/albums/images/754448153.jpg

In the picture above are the 3 manifold options for our cars. From the left we have the cast log manifold which appeared after 06/02 build date cars, in the middle we have a collecter style manifold which appeared on the first built cars to 06/02 built cars and on the right we have supersprint headers.

The log manifolds has an output of 1.9", but that is fine cause you can get a dremel to open it up to to 2.2-2.5 inches see here for the JHM Mod. The collector style manifold has an opening of 2.5" and no modifications needed.

If you are going to get the JHM Dp’s they are 2.5" and to get the most out of your car you will want to get a 2.5 inch cat back. The stock S4 exhaust is not much if not the same as our standard exhaust, so probably not really worth going that route.

But 2.5 inch is definitely the way to go, and you wont need to modify anything to the intake as that is fine.

JHM has said that at the moment they wont make any longtube headers for our cars as out manifold are not that restrictive yet. When the SC arrives could be a different question.

#56

Thanks Lout, I’m headed to pick my car up from detail shop so I’ll check my build date.

I’m pretty sure the B6 S4 exhaust is 2.5"

#57

Most ceramic coating companies won’t warranty the work if you wrap them with header wrap after the coating. The header wrap can hold moisture, and if it’s not a good Stainless Steel, then that can lead to rust etc.

On the V8’s the only option for headers is to wrap them pretty much. The debate goes back and forth performance wise on which is best, but the simple fact is, the wrap provides more of a buffer to wires and such near the headers and help keep heat down. The ceramic coating is very effective, but still will melt a wire and radiate heat outwards. The Wrap allows the dissipation to be a bit more gradual.

I went with DIE Titanium Wrap, and it was WELL WELL worth the money over the standard wrap. standard wrap you soak in water to make more pliable as you install it, but the Titanium wrap has more play with it so it makes getting very tight angles much easier and you don’t need to wet it at all. So far it’s held up great and I’m so glad I bought it (I used some of both, and after finishing, I went back and removed the normal wrap and bought more DIE titanium wrap).

#58

Thanks Maddog, very informative. Have a reccomendation on where to get the wrap from? Maybe JHM will order some for us. If I went with the wrap, would you suggust doing just the headers? or the DP’s as well?

Any chance you have some pics that you could share with us to show what it looks like?

#59

http://i1108.photobucket.com/albums/h411/halo549b/Dyno1.jpg

After taking a close look at numbers from this data I would have to say this data is from a 4.2L
with 2.5 full not sure if test pipe or CATS.

All the dyno testing I see on the 4.2L show this same rise of HP at 4.800-5200rpms.
The dyno testing for the NA 3.0L with H or X pipe shows a sharp HP drop off between 4800-5200
regardless of the diamiter or H or X pipe.

Testing on volumetric rates show a larger pulling or vacuum effect with the X pipe but only a small HP gain.

I can’t find enough data to show larger gains with the X pipe on the NA 3.0L.

#60

^I was under the impression that’s a chart from quite a while back and not related directly to the Audi 4.2 at all. Perhaps domestic mustangs etc, as I think they’re using 5,800 as getting close to redline. The concept is still there, but just wanted to clarify (from my understanding/memory).

For the DIE header wrap, I just bought from their website and bought plenty of it.
http://www.designengineering.com/category/catalog/dei-cycle/motorcycle-exhaust-pipe-wrap-kits/titanium-exhaust-wrap-lr-technology

https://www.designengineering.com/sites/default/files/imagecache/product_full/dei-exhaustwrap-titanium.jpg

Here are some pics from my header install and wrap process. I REALLY took my time(~2-3hrs per side probably), but I was proud of the finished product and I used plenty of SS Zip Ties.

First off. . . mmmmm. . . sexy!

http://i278.photobucket.com/albums/kk89/mbgt72/My%20Audi%20S4/Header%20Install/file-18.jpg

http://i278.photobucket.com/albums/kk89/mbgt72/My%20Audi%20S4/Header%20Install/file-28.jpg

http://i278.photobucket.com/albums/kk89/mbgt72/My%20Audi%20S4/Header%20Install/file-26.jpg

http://i278.photobucket.com/albums/kk89/mbgt72/My%20Audi%20S4/Header%20Install/file-30.jpg

http://i278.photobucket.com/albums/kk89/mbgt72/My%20Audi%20S4/Header%20Install/file-29.jpg

http://i278.photobucket.com/albums/kk89/mbgt72/My%20Audi%20S4/Header%20Install/file-46.jpg

http://i278.photobucket.com/albums/kk89/mbgt72/My%20Audi%20S4/Header%20Install/file-24.jpg

http://i278.photobucket.com/albums/kk89/mbgt72/My%20Audi%20S4/Header%20Install/file-22.jpg

^The “grey” part is normal header wrap, I ended up going to buy more “titanium” wrap b/c I’m picky and swapped it out.

Also, a couple pointers from beem & others:
1)The zip ties are your friend
2)Work slow with ~.25" overlap as you work down at a slight angle
3)Start at the top of one primary and work your way all the way down that one and back up the next
4)Wrap each one individually and use the zip ties at the beginning and end
5)KEEP IT TIGHT ALWAYS! You never want it to kink up etc, this is where the titanium stuff is worth it!
6)Take your time and retrace your steps if need be to get it right, you only get once chance once the motor is back in

Also, to answer your question, we wrapped my catless DP’s down to the flex joint when we did my s/c build, but that’s just kinda b/c I had some wrap laying around at the time and figured it wouldn’t hurt anything. It’s not really gonna help much, but keeping the heat where you want it is always good. Count did say there is a limit where it’s useful, and he didn’t want to wrap past the flex joint b/c of a couple reasons.