So for the past 3 years I did a lot of research on secondary heat exchanger upgrades for the w220 S55 with the m113k and all I was coming across is the w211 heat exchanger, + 2 threads here one from 2011 about a member who installed NPI heat exchanger on the S55 and another who wanted to do so but he was advised not to waste money on that since the S55 comes with 2 from the factory... so I started more research and i found the froozenboost type 101 H-EXchanger vut it was very long (26 inches) which cant fit in where i want it to go. and i found some other brands but all of them either too long or too tall. so i started doing my own experiments. And this tread is the results of my successful attempt so far to solve the high AITs from more boost. On the w220 s55 ( which can apply to the S65 too with the exception of not removing the secondary one since the secondary heat excahanger in the S65 is not actually a heat exchanger it is an oil cooler so it goes under the new one instead of removing like what i did in the S55.



But first a bit of background on my car and what mods it has so you can relate to your setup or at least understand why there is a need for an upgraded secondary heat exchanger. So here we go, my setup is the following:

Boost levels:
- Supercharger pulley: 83mm (stock: 90mm)
- fixed Crank pulley: 185mm (stock: 154mm)
- Boost level: 17.8 psi in 35c ambient temp and 19psi in cold weather (17c ) , stable up to 6500 RPM (drops only ~0.7 psi near redline) ( the stock boost is about 11psi if i remember correctly)

Fuel System: Bosch 630cc injectors (stock: 420cc)

Cooling System:
- Dual Bosch pumps + trunk-mounted 16L ice tank.
- Water path: Trunk tank → pump → HE1 → HE2 → pump → intercooler → back to trunk.

Additional Cooling Aid:
- AEM Methanol Injection – Stage 2 Kit with Dual 500cc nozzles. Triggered by boost (start: 12 psi, full: 17 psi)

Intake & Airflow:
- K&N drop-in filters
- Upgraded throttle body: 83–84mm (stock: 73mm)

Other Supporting Mods:
- Belt wrap kit – minimizes belt slip
- Oil catch can
- Cat delete.

Eurocharged ECU tune for all listed mods

Now after reading this painfully long details, you now have a better idea about the WHY?! Now about the fun part which is HOW?



Well, if you are like me and you want to keep your front pumper untouched and use all the mounting screws like the factory and also use the original mounting bolts to mount the upgraded Heat exchanger, then this thread is for you….

• I measured the front available space between the chassis parallel members, and I found out it is 24 inches…. So if I want to keep my upgraded heat exchanger between these two members and at the same time leave a space for the fitting connections for the rubber hoses while also avoid relocating the ABC pipe mounting bracket that is located on the passenger side ( on a LHD car) , then the heat exchanger has to be 20 inches in length at maximum.
• Also, if you wanna keep the plastic cover beneath the radiator untouched ( meaning no cutting in it ) while also keep the heat exchanger beneath the pumper reinforcement bar , then the heat exchanger must be 5.5 to 6 inches tall at maximum….
• And finally, if you want the secondary heat exchanger that you are trying to install to have a gab between it and the main heat exchanger while not touching the front pumper then the depth of it should not exceed 1.75 inches at maximum…

And from that , I looked for a heat exchanger with a dimension of 20x5.5x1.5 inches and found one locally manufactured with a great quality and a 2 pass one…

So the issue now is getting the coolant from the exit point of the main heat exchanger to the entry point on the secondary upgraded exchanger given the fact the entry for the coolant in any dual pass heat exchanger will be on the same side of each other’s which makes it on the opposite side of the original secondary heat exchanger…

Well to solve that you will need to have the inlet and outlet of your upgraded heat exchanger pointing to the driver side, this way the out of the main heat exchanger can fit directly to the secondary while the out of the secondary heat exchanger goes all the way from the right side of the car to the left side of the car where the inlet to the water pump is located. And as a point of advice , use 150 degrees fitting to direct the water that comes from the secondary heat exchanger towards the IC pump. This way you don’t run into the risk of bending a rubber hose all the way to the point that it restricts coolant flow.

The only thing is remaining now is to fix the heat exchanger in its place. You need to fabricate a bracket that can use the same holes in the back of the ( pumper reinforcement) to use the same bolts which is located there already.

NOW: here is the experience before and after the heat exchanger upgrades with the same boost numbers and at the same speed and in the same road to make sure altitude is the same, with slightly different ambient temps ( due to the tests was done 3 days apart) and methanol is working at the same settings in both tests:

TEST1 before the upgrade:
- ambient temp: 36c
- humidity 68%
- speed: 80km/h @ 2nd gear to 170km/h @ 3rd gear.
- boost levels: 17.1psi dropped to 16.0psi
- AIT: start at 46c and reached 85c at the end of the run.

TEST2 after the upgrade:
- ambient temp: 37c
- humidity 61%
- speed: 80km/h @ 2nd gear to 170km/h @ 3rd gear.
- boost levels: 17.3psi dropped to 16.7psi
- AIT: start at 41c and reached 58c at the end of the run.

all in all i am quite happy with the results and just for long drive reference: at ambient 37c, the AIT is stable at 50c while using cruise control for about 1 hour and 50 minutes highway driving on 138km/h. ( and this is after the upgrade) before the upgrade it takes less time to reach 50c but keep climbing up-to 55c.

I attached a few images to show the current setup with this heat exchanger, the fittings and ow it will look from outside the car. I like the stealth look since it looks more or less like the stock one which is perfect for my purposes.

 

Looks good OP. Nothing positive about high intake air temps.

Care to share manufacturer and part number of the added heat exchanger for those interested in following your lead?

Notes about the AEM water/Methanol injection system?

 

the heat exchanger i installed is made locally ( not US, canada or Europe)

about the AEM , i have 2 nozzles V2 with 500c size. and the methanol kit is stage two which uses boost controlled spray based on the built in MAP sensor.
- the spray start boost is 12psi and the full spray at 17psi
- the nozzles are installed in the surge tanks, about 2 inches from the the rubbers that connect the surge tanks to the supercharger (Y) part.
- the IAT sensor was relocated from the (Y) supercharger port to the passenger side surge tank 3 inches from the throttle body which puts it above the intake valve of cylinder 4 which makes it about 4 inches after the methanol spray to give the mist enough space to fully atomize as i test it outside the engine before installation. and also makes it read the most accurate AIT possible and the highest IAT for a safe ignition timing.

i can provide pictures for the methanol nozzles and the IAT sensor location.

as for the fabricated bracket, i forgot to take photos at the time of installation so i draw a simple diagram to show how it looks and the path of the coolant.

 

Pump shown in stock location? I have long thought is best to deliver pressure to the heat exchangers.... coolant flow the other way. I may not be seeing the rest of plumbing.

Getting all the air out of the charge cooling circuit is a special treat. I suggest a bleeder at highest point in end tank of heat exchanger.

Your arrangement looks very similar to what Brabus did with the K-8.

How much does water/Methanol drop IAT?

Thank you for mentioning the AEM kits. Likely saved me $700.00 over another kit I have considered that looks like it may be using rebranded AEM components. How big of a W/M tank are you using and how many miles does it last? I see AEM offers a five gallon tank ‘for diesels.’

 

i am using two pumps , the stock one is to pump coolant to the supercharger inter-cooler then back to the trunk tank. the second pump is in the trunk ( same bosch pump 110) which is located next to the tank to take coolant from the tank to the heat exchangers.
i already tried using the trunk tank pump to deliver the coolant to the inter-cooler then to the heat exchangers then the front pump then back to the tank , but this route cause the coolant to be hotter in hot weather. it can only be beneficial if you are using ice.

with regards to bleeding the system, the trunk tank is not the highest point , the highest in my system is still the inter-cooler stock bleeding point so i am good there.

about the Brabus K8 , this is interesting , i never knew about those, can you elaborate more about their setup?

How much does water/Methanol drop IAT? ( i will do a test tomorrow without methanol to see the delta between with and without meth and then i will report back) keep in mind that the ambient temp in where i live is 45c in the day light and 35c in the evening so it is going to be high temps.

the v3 nozzles is compatible with the v2 kit you can exchange them if you like.. however i already done that exercise one year ago and replaced the v2 nozzles with the v3 , but from my experience they are much less reliable then the v2. i have this AEM meth KIT since 2017 and it is still working strong. one of the v3 nozzles that i installed a year ago failed and i went back to the v2 nozzles. they are still working.

 

this is the plumbing pass for my system

 

here is the data for the test without methanol:
ambient temp : 32c
start AIT : 40c
end AIT : 67c
test speed: from 80km/h to 157km/h
max boost: 15.6psi

so the delta between both test is 9 degrees but
- the ambient in this test was lower.
- the boost is lower.
- maximum speed is lower too.

the recovery to the temprature in the image (from 67 to 46c happened in less than 15 seconds)

as for the methanol tank i use : its 1 gallon tank which is the small one. it is good for 5 to 6 runs from 80 to 220km/h
this accounted based on starting boost spray at 12psi and full spray at 17psi. so if you reduce the boost full spray , it will last less runs.

 

Brabus added a secondary heat exchanger and up-sized the charge cooling pump. Still one pump in K-8. I may have been looking at how plumbing is routed and have it back wards but it seems the pump should be receiving heated charge coolant from S/C>Heat exchangers in front>(ice box in trunk... what is the point of it if not packed with ice or cooled via A/C heat exchanger?)>pump>S/C.

Recovery time is commendable. I also live in the desert and am looking to find the 150 or more horses that take leave as soon as ambient gets to the nineties. Not much space in front of the stack in my S-65.

When I fit water/Methanol it will get a bigger tank so it doesn’t have to be filled every tank of gas.

 

thanks for the information about brabus.
i understand that most people use the pluming route you descried ( i used to have it the same way you said for 1 year) it is more beneficial for air temps if you are adding ice in the rear tank , but for everyday driving temps, it actually heat up the air charge. the issue is that the temprature of the water in the trunk tank will always be hotter then outside( unless there is ice in there. ) adding to that the external temps ( in the place i live in , it reach 47c in the morning and 39c at night) so i found that the temps of the water in the trunk tank can reach 55c in mid day when the car is parked in the sun and a 35 minutes trip makes it go down to 49c at best ( i already measured the temps of the water in the trunk tank during the day before the trip and after it).

once i changed the rout for the coolant to what i mentioned on my new setup( before installing the new heat exchanger) , i found out that the IATs is around 58c when cruising on 130km/h on the highway, while it used to be 61c on the old route.

so yes the new route is better then the old route specially in hot weather. and on a side note,
meth also will help alot with your temps. and if you are going to use your existing AEM methanol kit, then make sure your V2 nozzles ate clean with no leaks and the pipes are secured in the nozzle without any loose pipes. also if you are going to use the V3 nozzles from AEM then make sure that the pin which hold the parts of the nozzles inside is very very tight , trust me i know from experience, i lost my both nozzles internal component because of this pin was not locked correctly.