Sorry it took me so long to give the next update, but here we go.
As mentioned previously, I knew that the two main weak points on the car I was going to have to update would be the brakes and the cooling. For the brakes, it was easy enough - I just gave Essex a call and ordered the AP Racing kit. For cooling, it was a bit more tricky. While I think it’s unfair to call the M2 a parts bin car, there are certain areas where it is a strange mix of standard N55 parts as well as bespoke M2 parts. The cooling system is one such area.
Many people say that the M2 does not need increased cooling, but I don’t believe that’s true. The M2 shares almost all of the radiator cores in the car with other N55 engines, and as the highest tuned variant of the N55 it is thusly running the closest to the cooling limits. I have been extensively tracking the N55 since 2013 and have found that with this engine, heat output rises drastically once you start making more power and raising boost.
Before we look at the M2’s cooling system in detail, I just want to say a few words about what I think is a common misconception in the N55 world. Everyone who tracks these cars focuses on oil temperature, but almost entirely ignores coolant temps. This is probably BMWs fault - my old X1 had an oil temp gauge instead of a coolant temp gauge, and the M2 takes a step back by having neither. Further, most N55s tend to run hotter oil temps than many people are used to from other platforms. A typical N55 will cruise between 235 and 255F depending on ambient. This scares people, so they talk about it more.
Oil temperature IS a real problem on track. With my previous car, it was very easy to exceed 300f on the track. This is despite having the full M-sport line of cooling, which includes the passenger side oil cooler. My car was having strange “ghost” limp mode issues where the power was clearly down, but it wasn’t throwing any codes until oil temp hit 300. I went through a lot of time and expense to custom fabricate a dual core system that incorporated two massive Setrab cores with ducting, and it worked great to drop my oil temp to around 200 on cruise, and never above 230f on track. But my car was still pulling throttle, which was driving me insane!
What finally clued me into what was happening was that during a track day in Colorado at Pueblo Motorsports park, iDrive showed a coolant temp related limp mode, not an oil temp limp mode. This made perfect sense that it only happened in Colorado and not in my home area of Cincinnati - the thinner air in Colorado has a lower heat capacity for the same volume as more dense Cincinnati air. If my car was running close enough to coolant temp limp mode that simply a change in elevation caused a full blown overheating limp mode, I reasoned it was probably protectively pulling power before the iDrive warning.
Sure enough, that’s exactly what was happening. Here is a chart to show when the ECU begins pulling throttle based on coolant temps.
Pay attention specifically to the temperature range 117-120. During this coolant temp range, the car will NOT display a warning in iDrive, but beginning at 117 degrees it will begin reducing power output! This is what was happening to me on-track. So from the perspective of maintaining full power output on track, there are two specific temps you will want to keep in mind:
Oil temp needs to be below 270
Coolant temp needs to be below 117 degrees
Even if these temperatures are exceeded for a split second, the engine will reduce power output for a period of time. One example of what was happening to me was in the braking zone after a long straight. The reduced airflow from slowing down right after a 3-4-5 gear pull would cause coolant temps to spike from 111C on average to 117 or 118. Hit the gas coming out of the corner and you would get reduced power.
In short, you really need to address both of these things on any N55 based car if you plan on pushing past stock power. You may not notice you are getting reduced power, but particularly on the coolant side my belief is that it happens to the vast majority of advanced BMW drivers.
Now that we have established the problem parameters in the cooling system, let’s take a look at what the M2’s system is actually made of.
There are five primary radiators in the M2:
1. Main radiator
2. Aux coolant radiator (driver’s side fender)
3. Oil cooler (passenger side fender
4. DCT cooler (mounted in front of the main radiator)
5. Intercooler (front bottom center of the car
I don’t really understand the claim of everyone that the M2 has some sort of “special” cooling system since the part numbers are shared with other N55’s as follows:
1. Part number 17118672103, shared with F22, F87, F30, F32, F36
2. Part number 17118625447, shared with F20, F21, F22, F87, F30, F32, F36
3. Part number 17217853240 - this is technically unique to the M2, but other N55’s have a slightly different shaped core in the exact same location. I think the only difference is in fitment, not performance.
4. Part number 17212409076, this part number is unique due to the fittings and hoses, but it uses the exact same core as the M3/M4
5. Part number 17118672103, shared with F22, F87, F30, F32, F36
Here is what all of these look like pulled out of the car, plus an aftermarket intercooler for comparison:
Besides from the slight differences in the oil cooler, the M2 has absolutely nothing special about the hard parts in the cooling system vs. the standard N55. The superiority of the M2’s cooling system is another victim of Bavarian Marketing Werke, just like the closed deck engine and “the largest tires that can fit from the factory without rubbing are 245 in the front.”
That being said, there is one important difference between DCT equipped cars and standard N55 equipped automatics, at least from the E9x series. The ZF 6 speed auto was cooled by the main automatic radiator, and that thing ran hot. The DCT cars have their own dedicated DCT cooler that is not plumbed to the main radiator. This means that DCT cars will absolutely run cooler than automatic N55 cars. This is where the M2 probably has an advantage.
I have previously worked with CSF Racing to solve coolant temp issues on my old build (old review of the previous gen N55 radiator:
http://www.e90post.com/forums/showthread.php?t=1121751), so Ravi at CSF was one of my first emails when I began kicking around this M2 build. I discovered that Yost Autosport was using a custom CSF DCT cooler which looked just like the stock M2 core with different lines. I reached out and asked if CSF would tweak the S55 DCT cooler to fit my N55 car, and after many emails it eventually turned into a co-development project where I stripped out my entire cooling system and sent it into CSF.
CSF Radiator from my X1 - Similar to M2 Radiator
CSF is quite an impressive outfit to work with. What really separates them from most vendors on the forum is that they are actually a hard-parts manufacturer that owns their own intellectual property; they do not simply contract out everything to some third party company and slap their name on it. As part of the development process, CSF is 3d scanning everything - cores, lines, etc, and will be modeling larger and more efficient cores. I will wait until development is finished and I have the parts back to post some of the most unique innovations we are trying to make work, but at the most basic level we plan on utilizing the efficiency gains from their their proprietary B-tube technology as well as increasing core sizes where possibly to achieve significant gains.
CSF B-Tube Technology - notice the seam in the middle
A typical radiator tube is in the shape of an “O” - we’ve all seen them, they just look like standard pipes. CSF developed a “B” shaped tube that is more difficult to manufacture, but has more surface area and is structurally stronger than an “O” shaped tube. This takes special care to manufacture as instead of just throwing in a prefab tubing section they have to actually form and braze the tubes to seal them, but it pays off by being able to use thinner and lighter aluminum due to higher structural integrity. This directly translates to higher thermal efficiency. Finally, fin specifications are calculated for each individual application and then measured in their wind tunnel lab. This type of commitment to performance development is the reason that you will find their products used in many of the top racing series throughout the sport.
CSF Racing Multi-Lourvered Fin Pack
I can’t wait to get the finished parts in and begin testing, and we look forward to making them available for all M2 owners down the road. It will be nice for enthusiasts to have cooling options that are professionally developed and track tested. I think you will see that as a theme as my build progresses - in a market full of bling, stance, and hard parking, I greatly appreciate companies that put development resources into low-volume, low-margin, professional motorsports products to support our passion.[/QUOTE
your gonna have to help me out here, Coolant temp is map and ecu controled via electric pump. Sport sport plus runs cooler, eco hotter.
The numbers in that chart are in C, not F, so the delta is pretty large, also it is my understanding bmw component protection does not cut power, just accessories (a/c) and may run pump/fans when car is off.
in a short span ( few seconds) for this to be accurate your moving the needle over 13 degrees F (from component protect to emergency)?
I would think you might be getting some fuel starvation, I have had that in similar turns, the way the pump feeds and the tank is divided on 2 series it can starve a bit. There are aftermarket kits and upgraded pumps, pickups. Been on my list but takes below a 1/2 tank to come on, not frequent but once and a while.
235 does not have gauges, but I have the m perf wheel, it is always on oil and coolant at track. I have never have seen the temp above 228 and usualy is 202-212, oil on track is 230-240. I check at least every lap, a habit of endurance racing.
Keep in mind I am usually burning the whole tank of fuel in one stint, not typ. 30 min run groups. I have 18k on the car, 11k are track miles. I only use this car to drive to the track, track it and back to the shop. I run 0w 40 oil with zddp additive (no cat) and 70% distilled water 30% coolant, with water wetter. My car is a manual, not sure where they stick your dct cooler.
Brake ducts good luck, you can see with the bumper off there is just no space in there. I gave up. I just took off my dust shields and cut some more holes in a few plastic trim areas on the 235, still run stock calipers, rotors with Porterfield pads ss lines and SRF Fluid. The calipers turned a weird green from heat very quick. You have more capacity for heat in the new setup, and better cooling veins, so should help a lot, but not in my limited budget.
The meth will keep the iat temps down, and internals clean. The jb4 controller is not that great in integration. I could run larger nozzles and have tried, but the power delivery is too delayed and abrupt from input (think nitrous) which has no benefit on track. 2.5-gallon tank is enough for one stint (tank of fuel on track) without getting low to starve.
I use 2 cm3 nozzles. This delivers pretty good amortization, and keeps iat 15-20 degrees cooler on track ( enough to stop the ecu timing issues when hot) The way mine is setup I end up being slightly rich, which is better for how I use the car. Power increase is nominal, maybe 15 hp with this setup.
I only use meth the track. 50/50 is best option for n55 motor with tune. Pure water has more heat capacity, but can cause other issues in combustion (pressures, detonation). If you would like more detail pm me, happy to share.
M2 Technical Topics >
N55 Engine / Drivetrain / Exhaust / Bolt-ons / Tuning >
Track / SEMA build thread - CSF Racing, Essex AP Racing, MCS Suspension
