[XutvJet]

Last Saturday I installed the HJS Euro 6 300 cell downpipe on my 2016 M235 6MT RWD (basically the same N55 as used in 335/435). The car is currently equipped with the M Performance exhaust, MP LSD, and Dinan Sport which is currently turned off. I went with a catted downpipe because most every review noted a nice increase in noise without it being obtrusive or creating drone; better throttle response; more power, especially in the mid range; and reduced turbo lag. All this sounded exactly like what I was looking for.

I choose the pricey Euro 6 for numerous for numerous reasons:

1) It looks dang near OEM and is a high quality, German made piece. Most other aftermarket DPs look aftermarket and some have inconsistent fitment.

2) It has a high quality 300 cell HJS cat which has 90% of the flow and power of the 200 cell HJS cat used on the Fabspeed DP and it's marginally quieter.

3) Due to the high quality 300 cell cat, there is little to no chance for a CEL and the cat will last longer.


I did the install on 7.5" high car ramps with the car's suspension lifted a bit with jacks to give myself a little more room. I found the install quiet easy. I could easily access the forward-most v-band bolt which was only torqued on with about 15 ft/lbs. I was able to get a small racket up there and then switched over to a gimbal ratchet. I had the OEM cat out in about 30 minutes once the under tray was off. I didn't remove any of the cat mounting brackets that attach to the transmission.

For the install, I used new front and rear OEM v-bands and a new gasket between the turbo and cat. I had the Euro 6 mounted up in about 10 minutes. Fitment was spot on. The new gasket to require a bit of pushing to seat the cat to the turbo. I also had to reach up and use a set of channel locks to squeeze the ears of the turbo/cat v-band because I couldn't quite get the v-band bolt started. It hardly took any force with the channel locks.
Oddly, the most difficult thing I found was those damn O2 sensor to heat shield clips. They are a bit fiddly because they attach in a difficult area to reach.

Once installed, I fired her up. Definitely a louder cold start as to be expected. I'd say it's 15% louder. Once the wastegate closes after the cold start, it's nothing extremely loud and pretty tame. The cat did smoke like a mutha during the first 45 minutes of it's first drive as the oil burned off the body of the cat.

I've driven around for a week now and have put 300 miles on the car and have driven in temps ranging from 0 degrees to 60 degrees. Yes, all in the same week. Welcome to Kansas City in March. I could not be happier with the way the drives and sounds. After about 30 miles of driving, the car really started adapting.

The new sound is intoxicating. It's deeper, more warble, fluid, free of rasp, and more exotic sounding, but without being boy-racer. It's so perfect and seems to be getting better as the days as it breaks in. Of course the overrun burbles are louder too. Yes, it is louder on the inside during all sorts of driving, but nothing terrible and I'm quite picky to what I'll tolerate sound wise plus I routinely take the family around in my car. There is no drone and during a steady cruise, there isn't much increase in noise (5-10%). I can hear more diverter valve noises from the stock intake/air filter as well. That was a surprise.

Throttle response is perfect. It's more responsive, easier to blip the throttle to rev match, and surprising, it's easier to execute a clearer 1-2 shift. That was a welcome improvement. Turbo lag is reduced a bit as well, though I've never found the lag bad.

There is a notable increase in power between 2,500rpms and 5,500rpms and some additional power above that, but it's most notable in that range. My car is currently on Alpin PA4 winter tires which are very grippy in the dry in a straight line. Prior to the cat, I couldn't get them to spin from a 3,500-4,000rpm punch in 2nd. Now it's pretty easy to do consistency. It also barks the Alpin tires on the 1-2 which is something it never did on these tires and hardly ever on the MPSS tires. Fabspeed shows a ~20whp and ~30wtq increase in the low to mid range with their 200 cell DP, so I imagine I'm feeling maybe 90% or so of that. The increase in power feels almost exactly like the Dinan Sport in the Sport setting which is 2-2.5psi. The motor just feels more flexible and willing. I'm curious to see how it will do with the Dinan Sport in Sport setting, but for now, I'm just enjoying the way it drives as is.

Lastly, no CELs.

Provided below is a thread regarding the install of the Euro 6 on an M2. He had a similar take.

https://f87.bimmerpost.com/forums/sh....php?t=1339166

[bqik]

thanks for the nice review.

[EDWYER]

Nice review.

[Jeff@TopGearSolutions]

Great review and information.

[mike@x-ph.com]

Thank you for the review

[TK335iMSPT]

Awesome review! Where did you purchase the downpipe?

[wdeerfield]

its a $1700 USD downpipe

[FastF30]

Originally Posted by wdeerfield

its a $1700 USD downpipe

Fabspeed is a steal when it was on special for $1200.... lol...

[XutvJet]

Originally Posted by TK335iMSPT

Awesome review! Where did you purchase the downpipe?

I purchased it from Jeff at TopGearSolutions. He was great to deal with.

[XutvJet]

Originally Posted by wdeerfield

its a $1700 USD downpipe

The HJS Euro 6 downpipe is way cheaper than that. It's marginally more expensive than the Fabspeed sport cat plus it had OEM build quality and look and a better, longer lasting cat.

[XutvJet]

Originally Posted by FastF30

Fabspeed is a steal when it was on special for $1200.... lol...

They're more expensive now after HJS, their supplier of the cat converters, raised their prices on the cats.