CSL intake vs Eventuri + Karbonius plenum (dynos)

[///MBan]

Hi all,

As some of you may know, I had an Eventuri plus the OE-based Karbonius plenum, but I was keen for a bit more CSL-style sound. I had already tried the sound generator mod but it sounds a bit flat to me and I didn't like how Hodge-podge the engine bay was looking with all these bits and pieces.

I emailed Josh from Severn Tuning (aka pokeybritches on the forums) and asked what the latest advice is regarding an alpha-n tune. His advice was that if you're doing it because your hardware requires it (i.e. supercharger or CSL intake), go for it. Suitably reassured, I ordered a race-style CSL intake from Karbonius and all the other bits and pieces required for the installation. For reference, here are the previous threads about my modifications:

Supersprint v1 stepped headers, s-pipe and Severn tune
viewtopic.php?t=128400

Full SS exhaust and Eventuri
viewtopic.php?t=132183

The install of the CSL intake went really smoothly thanks to guides provided by others on this and other forums. As others have experienced, you need to trim about 2cm off the snorkel on the 'race' version. I marked out the section that needed to be removed and took it to a friend who makes orthoses. He works with CF regularly and was able to get a super neat finish with a rounded cut-out.

IMG_4360_SML.jpg (154.21 KiB) Viewed 239 times

IMG_4359_SML.jpg (193.66 KiB) Viewed 239 times

IMG_4327_SML.jpg (120.46 KiB) Viewed 239 times

My previous dynos were done at a workshop that specialises in modifying BMWs. I needed them to install the parts - I'm not skilled enough or setup to do a header install myself. Because I did the CSL intake installation myself, I went to a dyno closer to me. Before the CSL intake installation I re-baselined the car. This was done after removal of the SS x-pipe (too much drone and rasp for me) and with the Karbonius OE-style plenum, so not exactly the same as my last run but unlikely to be very different power/torque wise.

Josh from Severn had sent me an alpha-n tune. Once I'd installed the intake, I flashed on the alpha-n tune using the super-easy new software Severn provides and everything ran really smoothly from the start. I did some data logging, which I sent to josh to refine the tune. The next version of the tune is what I took to the dyno for the 'after' run.

I also rented out the dyno for a few hours and Josh did a few tune revisions to see if there were more gains to be had from Vanos and ignition timing changes. In the end, the tune I had was the best, so Josh obviously has his standard maps pretty sorted already. Apologies for double vertical lines on the chart - the baseline run had rpm on the horizontal axis, but the comparison had speed which is much less useful, so I added the RPM from the previous chart.

This dyno read substantially higher than the last one, but don't get caught up in the absolute numbers.

CSL intake vs SS exhaust Eventuri and Karb plenum - Apr 2024.jpg (121.08 KiB) Viewed 239 times

Peak HP gain is 5% which is more than I was expecting to be honest. While peak torque hasn't changed, it now holds this peak over a wider RPM range and I reckon I can feel this on the road.

Below is a table showing the gains at each stage of my modifications. Each stage is re-baselined, so I feel like it is a reasonable representation of total gains. The final number is a bit over 17%. If you assume my car was making full power when I started (I know, it's a big assumption), the gains are in the order of 40kW at the engine.

Power gains table.jpg (53.07 KiB) Viewed 222 times

(edit: some calculations were wrong in the table)

The sound is really amazing and a substantial step up over my previous setup of Eventuri plus Karbonius plenum. It also looks so much cleaner in the engine bay.

And the tune has been flawless. If anything, it's smoother below 2,000rpm and I haven't noticed any difference from the tune I had before, or from stock.

I am totally stoked and can't recommend Severn Tuning enough. There is genuinely no one else that I know of that provides this level and quality of service for us Z4ers.

[Z4MCoupe86]

Very helpful insight. Just to confirm my own understanding, the dyno without the csl airbox (but with tune) made the same power as the csl airbox with tune (at least as far as the pre-csl tune allowed for as far as revs)?

It looks like the increase in power is only related to the extra couple hundred rpm the motor was allowed to rev with the csl airbox; nearly identical curves up until that point. Or am I misinterpreting?

[///MBan]

Very helpful insight. Just to confirm my own understanding, the dyno without the csl airbox (but with tune) made the same power as the csl airbox with tune (at least as far as the pre-csl tune allowed for as far as revs)?

It looks like the increase in power is only related to the extra couple hundred rpm the motor was allowed to rev with the csl airbox; nearly identical curves up until that point. Or am I misinterpreting?

For the pre-CSL run, the power had pretty much levelled off or was maybe even dropping. I’m not sure why the dyno operator stopped the run at that point, but maybe he could see the curve falling over?

Either way, the gains from the CSL intake are right at the top end (from 7,250rpm). More power wasn’t my purpose, so I’m not really worried but thought others may be interested

[Z4MCoupe86]

No worries. This is great validation showing just how good the stock intake/plenum already is from a performance standpoint and shows that it's not a constraint, even with a supersprint headers /exhaust setup.

Obviously nothing can hold up to the sound the csl airbox provides though. Good for people to have their eyes wide open if /when they go to upgrade.

What are the benefits of getting the race version of the airbox?

[///MBan]

The race version has an integrated snorkel the finishes right where the Z4 air intake is. In theory, it should be better than the normal version at getting a good air feed. I also think it looks neater since it doesn’t just end in space in the engine bay.

Resale would not be as good, though, because you have to cut a piece out of it (E46 M3s don’t need this).

[coldel]

Nice write up. All too often people focus on peak BHP as a measure of the effectiveness of a remap or modifications. When in fact its the area under the curve that is more important, the more area there is under it, the better it is. And of course taking out flat spots and the like.

Somewhat strange the chart only starts at 3000rpm though? Most start around the 1000 mark, it does hide what looks like a very odd low end which is way down on pre mapping? Appreciate this doesn't matter if you are flying around a track and changing at the top of the range but more day to day, the power delivery looks way down on the new map? Apologies if I am reading this wrong!

[///MBan]

I’m no dyno expert, but the suspect the dyno operator just started the pull a bit later? In the dyno chart with just the ‘before’ run, the pull starts much earlier, it just isn’t shown on the chart above. I suppose the display picks its start point where all runs on the chart have started?