[urq] Dialynx exhaust maniford (long reply)

[AUDIJIM@aol.com]

Steve and group,

I have heard that they pull studs out of heads and warp. I don't believe this 
if the head and the exhaust manifold have been properly machined prior to 
final installation. I can't speak for others who have installed the Dialynx EM on 
there cyl. heads, but I wonder if they just bolted it on and just started 
running it that way? I preheated my manifold to 500 deg. F and then machined the 
mating surface. When the EM cooled, there was little to no movement of the EM. 
I also machined the surface on the cylinder head so both mating surfaces were 
true. I have not run my EM like this yet and I have a couple more ideas to 
try before I do. The casting between the runners can be cut so there is more 
flexibility and movement when the EM approaches operating temperature. If I do 
cut the casting between the runners, I will reheat and measure on a true surface 
to see if there is any more movement/warping. I will also oversize the 
mounting holes for cylinder 1 and 5 on the EM. I will then use thicker machined 
washers and safety wire drilled nuts on all hardware. The Dialynx EM is a better 
design in my opinion. All exhaust runners go to the turbo. It has been descri
bed as a "log" but it is of a good design. As far a flow, I never ran a flow 
test of the stock EM compared to the Dialynx EM, but my naked eye flow test looks 
like it would flow better than stock. What it would do on a live test is 
anyone guess, unless someone has this information to share? The two piece turbo EM 
is getting to be a rare find these days. Yes, it's an improved design, but 
only to eliminate the cracking problem, but I'm sure there are some better flow 
characteristics as well. Cracked EM's are nothing new to Audi. When I worked 
for Audi, the 2.7 twin turbo S4 were just coming out. My Audi rep at the time 
told me that there was a delay due to every single S4 had cracked EM's right 
off the factory production line and they were waiting at the port this way. Cast 
EM's can be repaired effectively. I have welded a few and find that brazing 
works best. There is also an electrode that works well from www.muggyweld.com 
to be used while SMAW (shielded Metal Arc Welding) It is made just for welding 
cast iron. I haven't tried it yet, but the video on the web site looks 
promising. I have a cracked SQ EM that I repaired by V grooving and then preheating 
to 500 deg F and then brazing. I tried doing the same procedure but GTAW or TIG 
welded using a high nickel rod, but the repair started to show signs of hair 
line cracks at the weld point. I performed an eddy current test at the weld 
point to confirm this. Eddy current testing on a brazed joint showed no signs of 
weld/brazed joint failure. 

Have a great day,


Jim Furdyn
1983 UrQuattro #170 
1987 4000cs Q
1987 Euro 200/5000cs TQ 283,000 miles
1996 A6 Quattro Avant 
1987 Mercedes Benz Truck model 1219