S55 Finally some actual log data on CSF heat Exchanger upgrade!

Oct 24, 2016
Scottsdale, AZ
Hey guys, we battled IAT's at Shift Sector on Sunday, so we decided to upgrade the cars heat exchanger with the awesome @CSF unit. I contacted Ravi on Monday and it arrived on Tuesday, talk about service! (We paid for the exchanger, in case you think this is a free product for good review type of deal. We don't roll that way, we like data that is why we are posting this, we would have posted even if it did nothing -and said so)

I had one of our techs install it, and he said it was by the far the easiest one he installed yet, perfect fitment for how large it was compared with others on the market.

We had dynoed the car before the event, at that time the dyno room temps were fluctuating between 80-83F or so depending on the wind blowing through the shop. Today it was about 2 degrees coolers around 78-81 degrees. We use the same fan set up for all our dyno runs so no changes there.

The results were impressive.

Pre-CSF: 125F at the top of the run
Post CSF: 108F at the top of the run

Power stayed almost exactly the same on the dyno (check the correction factors when it was a bit hotter it was adding 1.02 instead of the 1.01 for today so add another 7 to today's power, and power is nearly identical, This is expected as we are in a controlled environment with IAT's not getting into the range where the DME is going to start pulling timing. We expect to see even a larger delta, and real benefits power wise on long multi-gear pulls at an event with high temps. We may try some 4-5-6 pulls tomorrow on the dyno and see how the temps hold.

As for these results. While 17 degrees may not seem like much, it could mean the difference between pulling 1-2 degrees of timing at an event and losing a race or pulling on someone. If you live in a warm climate and are on the fence... this is a worthwhile upgrade for sure!

Mods on the car:
VTT GC turbos
Cary Jordan tune
Catless DP
Injen intake
VTT silicone charge pipes
Evolution of speed manifold with PI
VTT top Mount intercooler
BMS/ACF exhaust
Stock lpfp
Stock hpfp
Stock motor
CSF heat exchanger
Pump E85
MT 285/35/19 SS streets

As always email with any questions!




Last edited:


Mar 10, 2018
European, based in China
Z4 N54 DCT
Just stumbled on this. You claim you saw an 17F improvement in (upto) 5F lower ambient (so perhaps only a 12F improvement really). You are using cooler air to cool what is already cooler air, so the exact ambient temp is important. So is humidity to some extend.

Anyhow, peak was 125F for stock and 108F for CSF, but the starting iat was also below 100F for the CSF and above 120F for the stock one (hard to read precisely from the pictures). I would have expected to see a difference of less than 5F as starting point given the difference in ambient temp?

Another question would be what the difference is in coolant volume compared to stock. Also I would have been curious as to any negative influences on engine coolant temps.
Oct 24, 2016
Scottsdale, AZ
Starting point was both cars warmed up on the dyno, starting temp on CSF was lower because it wouldn't get as warm as the stock one without adding load (idle wouldn't do it on our dyno) despite similar ambient and warmup protocol. While this subtracts a touch from a scientific A/B comparison of coolers themselves, it's also more indicative of what you'd see where it matters -on your car. The truth will be really told when we take her back to the 1/2 and see what temps look like at the end of the track, but from what we see thus far, it's very promising. Not sur on coolant volume differences, that's a question for CSF. Thanks for your comments!