Paulm wrote:Exhaust.
Overall the exhaust looks pretty good. double 2.5" system. 5" exhaust is pretty big. I am not big on flow calculations so not sure is 2.5" I enough per side. Again going back to the GTR a Single 4" can flow over 1400bhp. Not sure if that means 2 x 2.5" can flow more. I am sure its not that simple??
Cheap option would be GUT the cats (all 4) and replace the rear boxs. that would give straight through 2.5" system for very little money. Rear box is very poor flow design (you can see how the exhaust flow deadheads again the metalwork then will fill the box before it finds it way out) but good for noise reduction needs changed
Anyway my Plan
3" Catless downpipes. You can buy these separate from Milltek (don't need to buy the 1200 ones or a full system) for 218 each. Wrap them with heat resistant cloth in an attempt to keep engine bay temps down. I did think on getting them coated but there is little research to suggest any real benefit
3" front pipes again catless but will be flanged to allow for easy change when MOT comes round. Local fab shop
Connected to Milltek 2.5" system. I may look for into a fab shop doing me a full twin 3" system
The exhaust setup is the weak point in the RS6, ask a tuner like MRC and they will tell you that the stock system is very restrictive.
I had the full Milltek fitted yesterday and the difference it has made is night and day, I was actually very surprised at the difference it has made, spooling much quicker and punching harder for longer. The noise is superb, I went for the resonated section and glad that I did as it's loud, any louder and I think it would be too much. The videos on YT do not do it justice, the sound in real life and up close is so much better, it sounds like a bloody jet fighter
60hp gains from the exhaust prove that the standard exhaust system is choked with 2 x 2.5 and 4 cats.
Google an image of the standard downpipes, I dont think gutting the primary cats is an option without serious modifications. You would have to cut them open and reweld, not worth it in my opinion. The secondary cats probably a little easier but not convinced it would be worth it. 2 x 2.5' is not the same as 1 x 5, Velocity increases as pressure decreases through a narrower diamater restriction, so through a narrower pipe, velocity will be quicker, but pressure will be lower. EGT temps will therefore be higher being forced through a 2.5 inch downpipe as opposed to a larger diamater pipe. 5 inch pipework I suspect would be quite laggy, too much, turbos need a little back pressure. You need to keep valves in the back boxes for noise control (its very loud and would probably fail trackday noise limits) so straight through pipe back boxes would be a no go if you wanted to keep the RS6 as a comfortable cruiser.
The whole standard system is 2 x 2.5'', The original Milltek system is 2 x 2.75'', the new system now comprises of 2 x 3'' Cerakote coated downpipes flowing through front connecting/2nd cat bypass pipes, again 3 inches and then tapering down to 2.75 inch for the Milltek catback. I'm not sure where you have got your information from Paul reference buying the 3 inch downpipes uncoated and separately but through my own research that is wrong. The 2.75 inch downpipes are uncoated, all 3 inch downpipes are coated. Milltek do not have any 2.5 inch systems?
If you want to go above 750, I would think you would need the 3 inch opening downpipes (for EGT reasons) for Stage 2 power levels upto 750, the 2 x 2.75'' is good enough. The 3 inch downpipes are expensive at around £1350 retail, £1200 discounted. (2.75'' is £450 cheaper than those)
Are you sure on your hybrid figures?
The TTE900 units come in at 12000 Euros for the pair (£8600) for brand new turbos units hybridised. If you remove your units and send them to Simon at TTE, the cost comes down to 7000 euros for the hybrid work (£5k)
I do not know the cost of the TTE800 units but would be mega surprised if he is going to do the hybrid work for £2k (£1k a turbo) - I think he probably means £2k a turbo so £4k? I would get him to clarify that. I know the TTE900 prices are correct so if they are £5k on your used units, TTE800 wouldn't be too far off that? No idea on turnaround time but you would obviously have to remove them, send them, he does the work, sends them back to you and you refit. That process may take a good few weeks with the car being off the road? I think everything is going to be so much more expensive on the RS6 as it was in your GTR, much more captive smaller market.
Not convinced on the intakes, I've not seen anything yet on the 4.0TT that has convinced me to start fiddling around with it.
I look forward to seeing your results though, good luck
