Heat Soak = Loss of Power!

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Brabus SL

Active Member
Joined
Oct 10, 2008
Messages
179
Location
London
Car
Brabus SL55 K8
lopes seeing as you have the ultimate in Charge Cooling Systems in your car you may be able to help me with this one!

My engine bay is much to hot which rises my Air Intake Temperature to very high levels, even when stationary it runs at around 55c and at 80 mph almost 70c, I believe I am being robbed of a lot of power due to this,:( from my research at idle my Air intake Temp should be around 28c and at 150 mph it should not rise above 50c (depending on ambient temp) from my research I understand that when the Air Intake Temp raises to high levels the ECU will start to alter the timing (resulting in the reduction of BHP) start dumping fuel into the cylinders in order to cool down the engine and prevent "detonation" also thesuperchargerr can cut out, am thinking of taking my car to CP Racing as they seem to do a lot of work on the 55K engines and they seem to have had a lot of experience, has anyone heard or dealt with them or could arecommendationn be madeelse weree? There is no BRABUS in the UK only "Brabus Body styling fitters!"
my current BRABUS Charge Cooler setup comprises of two Charge Cooler pumps (Bosch and BRABUS)
4561606506_3d84101a14_o.jpg
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and two Charge Coolers, the original AMG and the BRABUS addition.
any help would be appreciated.
 
Sorry for the confusion, bit I meant to ask exactly where is the temperature probe, e.g. air inlet, blower inlet, blower outlet, inlet manifold, etc.?
 
Sorry for the confusion, bit I meant to ask exactly where is the temperature probe, e.g. air inlet, blower inlet, blower outlet, inlet manifold, etc.?

he might not know - if it is a VI monitor on the OBD port it will simply be interrogation of the ECU so the temp will be taken wherever the OE ECU measures it surely?
 
he might not know - if it is a VI monitor on the OBD port it will simply be interrogation of the ECU so the temp will be taken wherever the OE ECU measures it surely?
I agree, but when you are quoting intake temperatures the position of the probe is critical. For example, 70 C at the blower outlet would be quite reasonable but the same temperature after the intercooler means a problem.
 
Sorry for the confusion, bit I meant to ask exactly where is the temperature probe, e.g. air inlet, blower inlet, blower outlet, inlet manifold, etc.?

Sorry but I dont know! could it be located in or close to or in the throttle body?
 
In your vehicle I'm not sure where the throttle body is located in relation to things like the blower and the intercooler. However, if I can make some general comments from my experiences with my Celica.

I think that you're being very optimistic to expect a temperature at idle of 28C. Consider that an intercooler cannot reduce an inlet temperature much below 10 degrees above ambient at the very best due to the need for a reasonable temperature difference to allow heat transfer. When you then take into account the expected temperatures under your bonnet with it being jammed full of hot metal and with its cooling air generally being passed through a hot radiator you can appreciate that 28C seems very low.

I assume that you've checked the coolant level in the intercooler circuits and also checked that the pumps are working.

Can I also assume that the intercooler circuits are filled with the correct coolant. Yes, it does matter due to things like wetting agents in the correct additive giving improved heat transfer.

Are the intercooler pumps on permanently or are they switched? In Celica circles the very first modification to improve charge cooling is to set the pump permanently on.

Are the intercooler radiators clean? Are they mounted so that they get air before any other radiator?

How hot is the intercooler coolant getting after a run? Simply stop the engine and put a thermometer into the intercooler coolant or try it subjectively by just holding an intercooler pipe or radiator. If you can't keep you hand on one of the radiators then you can't expect to have a low intake temperature ( for example, a comfortable shower temperature is around 42C).

I'm sorry that I cannot give you any more specific help but I hope some of the above may have give you some things to think about.
 
I had the ST185 Celica GT-Four and it ditched the water-cooled intercooler for an air-cooled one. Fine whilst you were driving but awful when you came to a stop due to it's location (on top of the engine!!)
 
I had the ST185 Celica GT-Four and it ditched the water-cooled intercooler for an air-cooled one. Fine whilst you were driving but awful when you came to a stop due to it's location (on top of the engine!!)
The works team preferred the water-cooled intercooler because it gave much more stable temperatures.

Of course, they also used a water spray onto the intercooler radiator which really helps in keeping the temperature down.

With my ST205 being a WRC it has this water spray together with the complete turbo anti-lag setup. Fortunately for turbo life these are disabled in the ECU!
 
In your vehicle I'm not sure where the throttle body is located in relation to things like the blower and the intercooler. However, if I can make some general comments from my experiences with my Celica.

I think that you're being very optimistic to expect a temperature at idle of 28C. Consider that an intercooler cannot reduce an inlet temperature much below 10 degrees above ambient at the very best due to the need for a reasonable temperature difference to allow heat transfer. When you then take into account the expected temperatures under your bonnet with it being jammed full of hot metal and with its cooling air generally being passed through a hot radiator you can appreciate that 28C seems very low.

I assume that you've checked the coolant level in the intercooler circuits and also checked that the pumps are working.

Can I also assume that the intercooler circuits are filled with the correct coolant. Yes, it does matter due to things like wetting agents in the correct additive giving improved heat transfer.

Are the intercooler pumps on permanently or are they switched? In Celica circles the very first modification to improve charge cooling is to set the pump permanently on.

Are the intercooler radiators clean? Are they mounted so that they get air before any other radiator?

How hot is the intercooler coolant getting after a run? Simply stop the engine and put a thermometer into the intercooler coolant or try it subjectively by just holding an intercooler pipe or radiator. If you can't keep you hand on one of the radiators then you can't expect to have a low intake temperature ( for example, a comfortable shower temperature is around 42C).

I'm sorry that I cannot give you any more specific help but I hope some of the above may have give you some things to think about.
Hi Norman thanks for your reply.

I agree with you that 28c is optimistic, made a mistake I should have quoted between 38c and 40c

With regards to the location of the throttle body i believe its located at the top rear of the engine close to the bulkhead.

not sue if the pumps are on permanently or switched.

I believe that on the 55K engines the charge cooler and radiator share the same reservoir but different plumbing.

I have had the 2 pumps checked and they are both working, previously (300 miles ago) I had the Bosch pump changed as it was faulty.

The charge coolers are located close to the oil cooler (gearbox I think) at the bottom of the radiator location and in front of the radiator. so they do get air before the rad.

I am not sure how clear the airways are as its not easy to see through the air-scoop opening in the front spoiler, from what I can see it seems clear but its all very dark through the opening.

I will try to measure the temp of a charge cooler hose at the weekend.

Thanks again
 
Are the intercooler pumps on permanently or are they switched? In Celica circles the very first modification to improve charge cooling is to set the pump permanently on.

Do take care with this on an MB. Whilst logical, the intercooler pumps are known to be fragile on the kompressor engined AMGs at the best of times, and especially when always-on.

IIRC there was a recall on the relay, because it was known to fail. When they failed, they failed such that the intercooler pump was permanently on, which resulted in the pump failing leading to lots of fair sized warranty repairs.
 
IAT Sensor (Intake Air Temperature Sensor)

Hi All, I may have found my high IAT problem :bannana:, on Sunday afternoon I decided to check my IAT using my Data Logger, and as soon as I started my engine, immediatley the Data Logger was reading a IAT (Intake Air Temperature) of almost 50C, so my conclusion was that the IAT Sensor must be faulty and therefore sending an incorrect reading to the ECU resulting in my problem of lack of power :(. I tried out my Data Logger in my friends CLS55 AMG and when driving his reading is much, much lower than mine and his car has the standard S/C cooling system! I understand that the temperature is expected to be around 10C above the actual ambient temperature. I have found out that the IAT Sensor is located in the Throttle Body, the cost of the IAT Sensor is under £20 and around £45 labour, I thought I would start with replacing this part as it is a relativly inexpensive part to change, I will also get the cooling system bleed as recomended by Lopes80, just in case this problem also exsists. I will post the outcome.
 
.
How hot is the intercooler coolant getting after a run? Simply stop the engine and put a thermometer into the intercooler coolant or try it subjectively by just holding an intercooler pipe or radiator. If you can't keep you hand on one of the radiators then you can't expect to have a low intake temperature ( for example, a comfortable shower temperature is around 42C).

.
I do not have a seperate expansion tank for the Supercharger cooling system as it shares the radiator expansion tank :eek:, which way would be the best to mesure the Charge cooler Temp? :dk:
 
With my ST205 being a WRC it has this water spray together with the complete turbo anti-lag setup. Fortunately for turbo life these are disabled in the ECU!

My Scooby has auto water spray of intercooler enabled and has anti lag enabled, difference is massive compared to the standard car.:eek:
 
Hi All, I may have found my high IAT problem :bannana:, on Sunday afternoon I decided to check my IAT using my Data Logger, and as soon as I started my engine, immediatley the Data Logger was reading a IAT (Intake Air Temperature) of almost 50C, so my conclusion was that the IAT Sensor must be faulty and therefore sending an incorrect reading to the ECU resulting in my problem of lack of power :(. I tried out my Data Logger in my friends CLS55 AMG and when driving his reading is much, much lower than mine and his car has the standard S/C cooling system! I understand that the temperature is expected to be around 10C above the actual ambient temperature. I have found out that the IAT Sensor is located in the Throttle Body, the cost of the IAT Sensor is under £20 and around £45 labour, I thought I would start with replacing this part as it is a relativly inexpensive part to change, I will also get the cooling system bleed as recomended by Lopes80, just in case this problem also exsists. I will post the outcome.
I must say that changing my IAT Sensor has made no difference :wallbash:, I have to look elsewere, perhaps my problem lies with my MAF!! :(
 
Brabus SL, I do not think 10DegC above ambient is an accurate figure for intake temps on a SC'd engine, there are too many factors involved. Even in a normally aspirated engine you would expect IAT's to be higher than ambient, just from general heat soak, and airflow obstructions.

One of the biggest downsides to a supercharger, are it's low efficiency. This is efficiency in air compression temperatures, nothing to do with mechanical efficiencies (that's another topic for SC's). Lobe type SC's are in the eff range of 50-60% at best. This means that the air gets disproportionately heated up by the compression device.

I take it that the Brabus has a higher drive ratio than standard in order to get the extra power? This means the SC will be turning faster than your friends standard set up, even at idle. But you also need to measure both cars in exactly the same conditions.

I don't know the Brabus set up, but the pictures show what looks like quite a small charge cooler, so it won't be very good at taking heat away. You also need to remember that a chargecooler also has the ability to be a charge heater. This will be in effect when you go for a hard run, the water will heat up. If you then measured the temps at idle, the water will actually be heating the charge up. Bear in mind that charge temps before the cooler could be as high as 100degC at full pelt, and will take the water temps up well above ambiant.

For a full diagnostic if you are interested, you would need to install IA temperature probes both before and after the charge cooler, and also water temp probes in the charge cooler water circuit. All datalogged. :)
 
Hi Nisfan, thank you for your reply.
The BRABUS setup consists of two charge coolers but in the pictures you can't realy see the original AMG one, from the BRABUS blurb they say that with the addition of their charge cooler and additional charge cooler pump the system runs 30% cooler than the standard SL55 charge cooling system, so with that information I compared it to my friends CLS55 which is basically the same engine! But his car seemed to run cooler than mine, even under hard acceleration the IAT reading was lower. I am not exactly sure why I am losing power but I sure am, It seems that when I do a "standing start" my power is there imediatley but by the time I reach around 80 or 90 mph my power seem to ebb away and increase in speed with much less haste, to a point where I am increasing by 10 mph evey 10 seconds (or so it seems) I am trying to get this sorted out, i have taken it to london's largest MB Dealer and they said "we can't find any loss of power" but I know it's power, for example my other friend has a 07 plate SLK350 and sometimes I can't pull away from him, but other times I can smoke him easy,i think my issue is intermittent. Not exactly sure what to do next, I may have to go to CP Racing in order for them to put in on their Dyno and hook it up to their test equipment then see the results.*
 
In that case, yes. A dyno will be the way to go. Better if they can fit additional temperature sensors to see where things are getting hot, as well as manifold pressure. Lambda sensor will pick up overfuelling.

I'm surprised Brabus didn't fit an air-air intercooler? Perhaps a space issue?

If your stuck for a good place with the right dyno, you can't go wrong with Abbeymotorsport in Gillingham. Good guys there, and have dynopack hub dyno. Not MB specialists, but know all about TC's and SC's ;)
 
In that case, yes. A dyno will be the way to go. Better if they can fit additional temperature sensors to see where things are getting hot, as well as manifold pressure. Lambda sensor will pick up overfuelling.

I'm surprised Brabus didn't fit an air-air intercooler? Perhaps a space issue?

If your stuck for a good place with the right dyno, you can't go wrong with Abbeymotorsport in Gillingham. Good guys there, and have dynopack hub dyno. Not MB specialists, but know all about TC's and SC's ;)

I'd second that Abbey Motorsport are a top notch outfit :thumb:
 

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