I know me and another member have our cars getting prototype exhausts put on the car.
So far we found out that 2.75 seems to be too big for this motor. The car seemed to loose alittle down low but pick it back up top. with the 2.5 exhaust I found that the lower RPM’s didn’t suffer and the top end seemed just as strong if not stronger.
Any thoughts on this?
That would coincide with the research done on the B6/B7 S4 (2.5" optimal) vs RS4 exhaust (2.75" optimal). Based on the similarities between the S5 engine and the b6s4 engine I would say that is pretty much bang on.
Exactly. Being a S5 guy Im glad to see that the old song and hat of just make some pipes and add a muffler type of mantality isn’t whats going on here with the S5.
Who is doing the exhaust for you
I am glad that they tested that out. I know it took time, but its nice to have real information on what size exhaust is optimal. I am excited about seeing what type of difference it makes.
So I take it since the FSI “comfort” motor doesn’t rev nearly as high as the FSI “sport” motor, you didn’t seen the gains in the 2.75 like the RS4 showed? My understanding was that was really the primary reason for jumping up to 2.75" in the RS4 b/c it Revs so high that the exhaust flow is much greater at 8k then what the S4 produced around 6.5k (what JHM typically agrees is the best shiftpoint for powerband in the 1/4 on the B6/7 S4).
What does the S5 have stock for exhaust diameter?
Are you able to share any info on the prototype units, i.e. what type of muffler, is it the same crossover the S4 uses, any special changes adapted to the S5?
Finally, I would really love to see pics of the S5, I’m a S5 whore and I’d just love to catch a glimpse of a car getting some prototype work done (My S5(afe) Hyden, that applies to you too, we’re all still waiting to see pics of your Audi!)
Makes sense, revs, displacement and effective compression ratio (including boost) are going to be the main determinants of how big an exhaust should be. Since all three motors (S4, RS4, S5) are N/A with 4.2L then the revs becomes the big difference, and the extra 1000RPM of revs for the RS4 would support the bigger pipe.
Plus if you think about it the RS4 is built to make power up higher, its optimized already for power above 5500rpm whereas the S5 and S4 are built to start making good power at 3000rpm. It comes down to how the heads are built and the cams are ground. But the higher end powerband of the RS4 naturally supports selecting a bigger exhaust better optimized for the top end power.
Ill get some pictures of my stock exhaust. The dia is 2.3. Its super tame and super quiet. From a hotrod perspective It makes sense that the 2.5 would be better suted to the comfort FSI cam profile wise and dynamics of the motor seem to point better in that direction
The S5 exhaust is not too bad stock. A little bigger would really help. I like not going to the 2.75. It just seems too much for the RPM and hp.
The only part of the S5 exhaust that bothers me is the passenger side DP At the top it has a big divit that does not need to be there, no clearance issue just kind of a stupid design.
If you have ever seen the exhaust on a S5, the down pipe on the driver side is really not ran well. I don’t know why but the steering arm is right in the way of the exhaust coming off the header, the result is a very odd shape and bend to that pipe. It would be nice to see someone do something with that.
The S5 also just has an exhaust that bends and twists. I think if one could make it more straight that in its own right would be helpful.
From what I remember both the RS4 and the S5 have a 2.3 inch exhaust dia.
I deffinitly started to look at the exhaust system for the next step. The tune is running strong but as I can see from so many other JHM tuned cars the tune will adapt up with a better support field.
I don’t have a hoist but I jacked up the car to get a look under her and it looks like a twisted mess. Any ideas on what is the best way to go. Any new news on the JHM exhaust