E89 35i Air Intake / Stainless exhausts

[J1mmys]

Hi,

After doing some googling I’m struggling to see many options for performance air intake and exhaust systems? Only really looking from a noise point of view these engines sound amazing I’m sure what a stainless system they would sound even better.

[Smartbear]

Hi,

After doing some googling I’m struggling to see many options for performance air intake and exhaust systems? Only really looking from a noise point of view these engines sound amazing I’m sure what a stainless system they would sound even better.

I’m sure the standard system is stainless?
Rob

[J1mmys]

Do you know what you could be right I haven’t actually checked haha

[R.E92]

There's very little performance increase to be had from the 35i with either an intake or cat-back exhaust.

The big restriction in the exhaust are the primary cats which are quite commonly deleted. I recently installed catless downpipes on my car and the performance gain is sizeable, it almost completely removes turbo lag and makes the car sound a lot more aggressive.

[J1mmys]

What brand of pipes did you use?

[Bombardino]

I'm also considering the downpipes route & would be keen to hear your thoughts, I know there a complete pain in the arse to fit, a local BMW specialist reckon about 6-7 hours labour. to fit.

[enzed4]

There's very little performance increase to be had from the 35i with either an intake or cat-back exhaust.

The big restriction in the exhaust are the primary cats which are quite commonly deleted. I recently installed catless downpipes on my car and the performance gain is sizeable, it almost completely removes turbo lag and makes the car sound a lot more aggressive.

That's good to know, thanks, I might look at that option as well.
The factory air intake was missing from mine when I bought it, I'm looking at replacing it with an AFE stage 2 intake to replace the tired old pods that are there now. I'm thinking this will be cheaper than sourcing a factory filter setup.

[R.E92]

What brand of pipes did you use?

VRSF.
I ordered from here:
https://www.n54tuning.com/vrsf-3-cast-s ... -35is.html

I contacted Mike directly via email ([email protected]) to make the order. He was able to reduce the price including shipping down to $438.50 USD. He agreed to declare the value of the goods at their material cost so that import duties were minimal. Total cost of £360.

The pipes come with the fitting kit included and a replacement bolt for the engine mount so that the DPs don't rub.

The install was a real struggle on jack stands. I installed a new intercooler, adjusted my rear turbo wastegate and replaced all of the o-rings in the charge air pipework while I was under there so the entire job took the entirety of Saturday afternoon and all day Sunday! Just doing the downpipes alone I'd expect it to take 8-10 hours for a first timer. Second time around about 5 hours.

I spent a lot of time reading guides and watching install videos for left-hand drive cars which are useful but access to the rear turbo on the right-hand drive Z4 is completely different, you have to access it from above which makes everything 10 times harder.

Nick9one1 on these forums also did a DIY downpipe install. He gave me a few good tips which probably saved me from giving up on the whole install.

I enjoyed the install but it was certainly a labour of love. For anyone with less patience for working on cars I would suggest getting a garage like Darren Wood in Stockport or Birds to do the install. I'd expect a cost of £300.

[R.E92]

I'm also considering the downpipes route & would be keen to hear your thoughts, I know there a complete pain in the arse to fit, a local BMW specialist reckon about 6-7 hours labour. to fit.

Yes, that's a pretty honest assessment. The big worry with me getting someone else to fit them is that it's very easy to screw the install up and then you have the hassle of remedial work and return trips to the garage. It would have to be a shop with experience in N54 downpipe installs that knows of the most common shortcomings.

The main things to look out for after install are:
- Exhaust leaks from incorrect fittings of the vband clamps (they are seriously hard to re-fit) or poor fitment to the exhaust system.
- Damaged O2 sensors during removal and re-install
- vband clamp on rear turbo obstructing the wastegate arm of the turbo
- Downpipes touching the subframe causing rattles

You also need to code out the catalytic converter monitoring errors in the ECU. MHD will do this for you so not really a big deal.

[Bombardino]

Thanks for the info
Taking to the garage they seemed like they had plenty of knowledge of the n54, they even mentioned that one of the housing bolt either needs changing or grinding down slightly to avoid fouling.
O2 sensors not a problem as I’m running MHD already.
From what I can gather there’s a noticeable improvement on power delivery.

[R.E92]

Thanks for the info
Taking to the garage they seemed like they had plenty of knowledge of the n54, they even mentioned that one of the housing bolt either needs changing or grinding down slightly to avoid fouling.
O2 sensors not a problem as I’m running MHD already.
From what I can gather there’s a noticeable improvement on power delivery.

That's right. The downpipes come with the replacement bolt. I didn't realise the purpose of this bolt until after the install so I removed the existing bolt and took an angle grinder to it.
I'll fit the replacement bolt when I'm under the car next time.

The power delivery improvement is unreal. I didn't expect the spool to be so much faster but it really feels like a NA engine. The power increase is quoted at 20-25bhp which is a nice bonus.

[Bombardino]

May I ask what brand you went with? I know there’s not to many to choose from.

[R.E92]

May I ask what brand you went with? I know there’s not to many to choose from.

VRSF. Check my earlier post for details on the ordering.

You can buy them from MLPerformance in the UK but I'm pretty sure that they also ship them in from the USA so wouldn't be any faster. They also charge £400 whereas I only paid £360 in total from the US.

You can get downpipes cheap from eBay and Aliexpress but they require the flanges to be cut and rewelded to get them to fit. Also not sure if they come with the same fitting hardware that the VRSF ones did.

[J1mmys]

20-25bhp that’s a fair power increase for the money would love to hear yours if you have any vids.

[gadgetJunky72]

Will the car still pass the emissions test at MOT time with a cat delete? thx