BMW's S63 is a seriously powerful engine when tuned. Actually, the S63 M5 and M6 are so powerful it just about maxes the stock DCT with a tune-only. Following a tune, upgraded downpipes are the next best bolt-on to extract more power. Although, this may push the transmission past it's limits. More on this later. Let's jump in and discuss catless vs catted DP's and the pros and cons of each.
BMW S63 Upgraded Downpipes Performance
Catalytic converters (cats) in the OEM S63 DP's are designed to reduce emissions. They do an excellent job at that. However, they are also highly restrictive and reduce power and performance. Turbochargers rely on a drop in pressure from pre-turbo to post-turbo. This allows turbos to spool and build boost as the exhaust gases look to escape to less dense air. Reducing back-pressure allows the gases to escape faster and more efficiently. Therefore, no exhaust behind the turbos is actually the best exhaust. Likely not too reasonable. This is where catless and high-flow catted DP's come into play.
S63 Catless Downpipes vs High-Flow Catted Downpipes
In basic terms, performance increases as back-pressure decreases. High-flow S63 catted DP's aim to use less restrictive catalytic converters. On the other hand, S63 catless downpipes have absolutely no catalytic converters. As such, they are the less restrictive option and will lead to the best power gains and quickest turbo spool. They do, however, come with their own downside. Catless DP's are unlikely to pass state inspections or emissions testing.
For those not concerned with emissions - we highly recommend opting for catless downpipes on their M5 or M6. They are generally less expensive and provide better performance benefits as compared to catted DP's. Though, high-flow catted DP's remain an excellent option for a balance of performance and cleaner emissions. Depending on the state or country it is possible you still fail emissions testing with high-flow catted downpipes. However, in most cases, the S63 should still be compliant with emissions requirements.
S63tu Upgraded Downpipe Pros
- 40-50whp with catless (15-25whp with high-flow catted)
- 50-60wtq with catless (20-25wtq with high-flow catted)
- Improved turbo spool
- Bigger gains on top-end
- Intoxicating sound
These power gains are truly insane. A JB4 tuned S63tu with catless downpipes is likely to see 650-675 wheel horsepower and 700-725 wheel torque. Let's circle back to our initial comments on the factory DCT. It's upper limits before the clutch packs start slipping seems to be around 675wtq. Therefore, catless DP's may cause the DCT to slip (if this doesn't already happen with a tune-only). You've got a few options here:
- Stick to lower boost maps and keep power/torque down a little
- Upgrade to Dodson or SSP clutch packs
Using a lower boost map may negate some of the potential gains from the DP's. However, there are other benefits such as the quicker turbo spool and better boost and power on the top-end. Otherwise, if you really want to push the S63tu hard you may need upgraded clutch packs. These run in excess of $4,000, not including installation. It's an expensive road to go down, but it's a needed expense for anyone looking to push the S63 to its limits.
S63 Catless Downpipes Sound
One of our favorite benefits to upgraded downpipes are the awesome sounds. S63 catless DP's will make cold starts louder. Additionally, dig into the throttle and the M5/M6 exhaust wakes up with a deeper, aggressive note. Although, while cruising around town or on the highway the exhaust remains relatively quiet. It's not overly invasive inside the car and drone is minimal or non-existent. This is partially why we like downpipes so much. Stock-like sounds when you want to cruise and relax, but a more aggressive exhaust sound when it's time to have fun.
*High-flow catted downpipes will also be louder than stock, but less so than catless options.
BMW S63 Upgraded Downpipe Options
In this section, we'll provide a few popular, quality options on the market for the M5 and M6. This is not an exhaustive list as there are several options we will not list. However, the S63 market is a bit smaller and less crowded as compared to many other turbo BMW's. As such, if you're coming from a different engine you may find the choices a bit more limited.
1) VRSF S63 Catless Downpipes
If you're looking for quality S63tu downpipes that offer the best bang for your buck - look no further. We believe VRSF offers an unmatched balance of price, quality, and performance. They back up their quality claims with a life-time warranty. It's hard to go wrong with the S63tu catless DP's from VRSF. The only drawback: VRSF does not offer high-flow catted DP's so those looking for catted DP's must look elsewhere. Expect the S63 to pick up about 50 wheel horsepower with these DP's.
VRSF S63 DP's Price: $599.99 (or $699.99 with high temp coating)
Buy Here: VRSF 3" S63 Catless Downpipes
2) Active Autowerke S63 Catless Downpipes
Another great, quality S63 catless downpipe option is from Active Autowerke. They've been in the BMW performance parts industry for a while and make excellent products. However, they do come it at twice the price of the VRSF option. Catless downpipes are pretty basic and not much matters outside of fitment and quality. Both use 304 grade stainless steel with quality fitment. As such, we recommend saving the money and opting for VRSF. Nonetheless, Active Autowerke is a great option if you're set on the brand.
Active Autowerke S63 DP's Price: $1,199.99
Buy Here: Active Autowerke S63 Catless Downpipes
3) Agency Power S63 High-Flow Racing Downpipes
Agency power offers both catless and high-flow catted DP options for the S63tu engine. As far as we've seen they're on the lower end of pricing for high-flow catted options...$2,800. Their catless downpipes come in at $1,600. These are a great option if you're looking for high-flow catted DP's. As much as we love upgraded DP's we just don't think high-flow catted downpipes are worth the price. However, if you're set on them then look no further.
Agency Power S63 DP's Price: $1,600 (catless); $2,800 (catted)
BMW S63 Upgraded Downpipes Summary
Aftermarket downpipes are a great way to extract big horsepower gains out of the S63tu. Catless DP's provide the most impressive gains, but come at the cost of increased emissions that may fail testing. Expect to pick up around 40-50whp with catless DP's. However, that raises another issue. A tune and DP's will take the factory S63 M5 and M6 DCT past it's upper limits. Either limit boost to keep power and torque down or opt for upgraded clutch packs for a cool $4,000+. Limiting boost may negate some of the potential power gains from catless downpipes. However, other benefits remain such as better top-end performance and quicker spool.
VRSF offers some of the cheapest S63tu catless DP's on the market with excellent quality and performance. Active Autowerke also offers an attractive option for those wanting catless DP's. On the other hand, Agency Power's high-flow catted DP's come in at a whopping $2,800; one of the cheapest catted options. For the price, we recommend opting for catless DP's or sticking with the factory parts. We would find it hard to justify the price of catted options. Either way, upgraded S63 downpipes are a great mod and the butt-dyno will definitely approve.