vrus

At first glance there seems to be a very simple way to cool the engine down... There are 2 plastic trays at the bottom of the car which cover the engine compartment.

The most forward tray has 2 air inlets in it with directional scoops that allow a MINIMUM amount of cool air to be directed into the engine compartment. If you look inside your hood downward just behind the radiator fan, you will be able to see the scoop pointing upward toward the headers.

I realize these 2 trays serve a few purposes:

1) They keep dirt and debris from entering the engine bay from the bottom.

2) They act as an aerodynamic plate to help air flow under the car.

They seem to also help in keeping cool air out of the engine compartment.

I would assume if one removed those trays that a nice amount of cold air would enter the engine compartment and help to cool it down. I've been very close to removing it a couple of times. I have never mentioned it before because I didn't want to say anything unless I was sure it was a good idea.

The reason I am posting now is to get some input.

1) I realize if I remove the trays I will probably adversely affect the aerodynamics of the car.. How much it will be affected... I am not sure.

2) I am concerned about the low placement of the alternator and worry about water splashing on it during rainy days.

Can anyone provide input on my 2 concerns above?

E55 and 993

I can't really speak to the E55, but on my Porsche 993 the same engine covers exist under the car. We all pull them off. It mostly traps hot air underneath.

I anxious to see what the experts say about the E55....

Rafal

Doesn't the front plate (and rear too) act as a light weight sump guard?

vrus

Yup.. That's exactly why it was one of the first things I looked at on my E55.. I have had quite a few 993TT in my time (still have one now) and it is the first thing I always do is remove that tray.

Grumpy666

I wouldn't be too concerned with #1. You will not be seeing speeds where this could be a factor. In fact, it could actually provide a little more downforce at speed. High-speed cars with enclosed underbellies typically have channels designed in to divert the air flow. This helps prevent lift at speed. If you look at the side profile of most cars, what you see resembles an airfoil - similar to the wing of an airplane. Taking the panels off will create some turbulence and disrupt the high pressure area, thus reducing the potential to lift.

For #2 you could fabricate a splash shield of sorts using just about anything that will fit - plastic bowl, bottom half of a milk jug, ect. It won't be pretty, but you always paint or decorate.

I have another thought. Instead of removing the covers, could you alter them to direct more air flow across the engine? Some kind of baffle arrangement or maybe 3"/4" ABS fittings? This way you could focus the cooling effect, rather than relying on random air movement. Also, is there a good exit path for this air? Or are you expecting the removed covers to provide the exit path?

rflow306

Those covers are there for less wind drag. In heads up drag-racing they seal up as much as the rules allow including the entire front grill.

Most high end cars are covered from front to back including the transmission tunnel. The question I have is at what speed are they truly effective ?

Victor just try it what can you lose they aren't hard to remove. Make a few runs at the track with them off and see what happens.

CALBenzo

I was just going to comment that I pulled them off on my 993, especially since these engines are air cooled.

I would think that for 99.9% of the time, pulling them would be beneficial in cooling the engine, but it may increase drag for 0.1% of the time you are at the track.

cte430

I haven't searched for the old posts so I don't know the specifics, but remember the crook from Australia who "designed" a cooling package that he was selling? We know he was a crook, but did his idea make sense from a cooling perspective? I don't remember what was in his "kit", just trying to maybe give you some other ideas on your cooling quest

vrus

I like it!!! Great idea! They already have those directional tubes now but they are pretty small... Maybe they could be removed or enlarged?

I will remove the trays and study them a bit and see if I can come up with something.. I'll post some pics of the general shape of them once I get them removed. I am expecting the underhood temps to drop quite a bit with the increased airflow.

I would guess that having no trays would provide better cooling though.. Don't you think?

Right now there is no air path to exit up top other than the grilles on the hood close to the base of the windshield.

I was thinking that the turbulence caused by the cool air entering the engine compartment from the bottom would be enough.. Do you think I really need to concern myself with an exit path?

vrus

Hey Chris,

I've got that part covered.. I have the EVO cooling upgrade which has the extra heat exchanger and high flow pump for the intercooler.

His name was Steve I believe.. He put together a package similar to what the SL55 had.. I dont think anyone bought a kit but it looked good from what I remember from the pics.

Thanks for trying anyways.

vrus

You know me.. I'll try it once just to see what happens.

I'll know right away if it works or not because my car likes to run hot so I'll notice any change in engine temp.

It's fast as heck, but it likes to operate at 100C +.... Go figure..

Grumpy666

Donno - hard to predict w/o knowing the air flow patterns and pressure deltas. Right now the air flowing through the radiator is passing over the engine and exiting between the engine and firewall to the underside. Right? If the air pressure at the bottom covers is higher than inside the engine compartment, then the air will try to flow up into compartment. If the exit flow is already restricted due to limited space, then there will probably not be much improvement. If, however, the air pressure at the covers is lower and/or there is a venturi effect from the flowing air, then air will flow down and you should be all fat, dumb, and happy. Unless, of course, the air that flows down is air straight from radiator and doesn't see the engine heat.

BTW - how much more air would flow if you removed the engine covers?

Do you have access to a themometer with a remote readout? Some controlled experiments would shed some light.


Since this tends to be a high pressure area at speed (remember cowl-induction hoods?), there probably won't be much venting through the grilles. At lower speeds there might be a little, and when stopped there will be some due to convection flow.


Depends on the conditions as stated above.

E55AMG99

Exactly what I was thinking. Do the vents at the base of the windshield connect to the engine compartment? My W210 doesn't appear to have an exit there.

houston

Victor, I noticed that mine is also running at 100C + ever since I got here to Ontario, I've changed the oil and yet still runs hot even tho the weather has been very cool. From what I remember it used to run at around 80C even while weather was hot. Was driving my sister's 91 E300 tonight and her car was running at 80C. Any suggestions?

vrus

I wish I had some suggestions.. As you can see from my posts I am chasing down anything I can to help lower the heat in this motor. If I figure out why it is running at that temp I will let everyone know..

I do know that the car runs VERY FAST when it is cool outside even though the motor temp is > 100C.. When the weather gets hotter it slows down but engine temp seems to be unaffected.. still at 100C - 105C.

MB Fanatic

Dont you have to create an area of high pressure for air to flow into the area we are talking about? I know my TL breathes from the bottom and there is a lip/spoiler under the car that creates an area of high pressure allowing the air to go into the intake. So if we just remove these panels we really arent doing much are we?

stevebez

From my experience its not abnormal for performance motors to run hot. (e.g. >100deg c), and most modern day cooling systems are pressurised to accomodate this.

In fact hotter motors makes them thermally more effiicient - especially in circumstances when ambient air temps are low. The greater the engine temp the more power you will extract from a power unit - and more so when intake air temps (IAT) are low. The ratio between IAT and engine temp determines how much the air will expand and therefore how much power you will extract. This explains why when IAT rise power drops off as engine temp remains static. The fact that the power unit temp does not rise tells me the engine is being cooled sufficiently and this this should not be a problem.

Having a cold engine is not a good thing power wise (IAT to engine temp ratio drops off). Having cold IAT's is a good thing period. Too hot an engine obviously compromises reliability etc. So its a fine balance.

Formula one motors have managed in the last few years to increase power output dramtically by enabling their engines to run much hotter by using synthetic oils, composite materials etc, raising thermal effiiciency.

In terms of cooling - I would concentrate on cooling the IAT's more than cooling the motor. Cooling the motor should only be a concern if you go well above 100deg c and the motor pulls back on boost often because the electronics start thinking its getting to dangerous levels. This would tell me you been on a track wacking the cr*p out of the car or the cooling system for the motor is under spec. Upgrading the engine cooling should not let it run cooler but let it run at normal opperating temps for longer.

Rgds Steve.

vrus

Hi Steve,

I agree with most of what you are saying.. What you are forgetting is that the E55K motor acts like a big heatsink. Everything under the hood is affected when the motor runs very hot. And that hot air seems to be trapped under there. Have you ever tried to touch the intake tubes on the car after driving it for an hour?? You could cook eggs on them.

You can only do so much to affect IATs (heat wrap, cryo cool, water cool, etc.)... I have covered some of those bases and will be covering the rest (water/meth injection) shortly.

I've heat wrapped fuel rails, spark plug wires & boots, intake tubes, intake boxes, phenolic spacers on intake manifolds, heat exchanger for supercharger, racing coolant (Evans NPG-R). I'm in the process of doing the water/meth injection...

Allowing some of the trapped air to escape and to keep the OUTSIDE of the motor and surrounding areas cool will directly affect the cooling of the air boxes, intake tubes, intake manifolds, etc.. So, if I can get rid of some of the lingering hot air I am also directly lowering IAT temps.

Also, when the car is up to operating temp (70C - 80C) it has considerably more power than when it is running at 100C. I can definitely feel a difference there. Believe me, if you havent done the experiment, try it. Run the car hard (you only get 1 chance at this) at 70C, and then do the same run again at 100C.. You'll notice a big difference.

I've done this experiment several times.. Leave house, drive very gently until motor comes to operating temp.. I wait until it hits 70C.. I run through the gears 2,3,4... Car runs CONSIDERABLY faster.. So, when I am at my normal 100C engine temp I notice a difference in power.

Remember, I keep saying my car is fast as heck.. Well, if I can get it to 70 - 80C where it seems to perform the best, it will be that much faster.

vrus

I guess I need to get some thermocouplers and pyrometers and start doing some hard testing.

Thanks for the input!

Well, I was hoping that the turbulence caused by removing the plastic shield would help evacuate some of the hot air.. At this point, there is only 1 way to find out and that is to remove them.

Looking at them again, I can remove the rearward one which is the biggest one.. No need to remove the front mounted one.

Will let everyone know what I think after I've driven for a couple of days.

Grumpy666

Where are the two covers located wrt engine placement? IOW - can airflow through the radiator pass over the engine before it would exit through the cover opening? Remember, airflow through the radiator will probably be at a higher pressure than air flowing by the covers. You could potentially make cooling worse by removing the cover(s). They might be there for more than aerodynamics and splash protection. Please monitor carefully.

vrus

The front cover sits just under the belt system and covers from the front of the engine forward to the front air dam.

The rearward cover is the big one. It starts just where the forward cover stops and goes all the way back behind the primary cats and just past the transmission bell housing.

I am assuming that airflow through the radiator will hit the front of the engine and then be directed downward..

Here is a pic under the car that shows what the tray looks like... Let me know what you think..

vraa

vrus: Your picture isn't loading bro?

stevebez

Yup if the car runs quicker when at 70-80 deg than at 100deg it has to be the IAT's that are being pushed up ... anyhow I take your point that the heat soak is across the entire engine bay and this affects IAT's - not sure how the electronics control boost with respect to temps (IAT's and motor) but perhaps there is some "engine preservation management" going on here.

So if you could better isolate intake air then we should be in business... the fact that the blower sits right on top of the motor and is metalic does not help at all as the blower itself acts like a hot hair drier on the IAT's -, seems no matter how much u cool IAT's upstream from the blower - it will simply just heat the air up again - although perhaps not to as a high a level as before. But not much you can do about that unless you get some setup where the blower is encased in a water jacket of some sort and independantly cooled by an additional radiator placed somewhere. Don't ask me where !

So intercooler and blower cooling are the best area of attack. How is the blower mounted ? Perhaps it can be better isolated from the engine unit.... I cannot tell as my car only arrives in Jan06!!

In terms of the covers discussed : I think they would create a vacuum just around the area of where the exhaust exits the engine bay ... drawing air from front to under the car away from the engine. Air is therefore being routed right at one of the hottest spots in the bay i.e. the exhaust downpipes. Removing covers may well not add much benefit at all I think - especially when driving at speed - but something that can only be resolved by actual experiment.

Rgds Steve.

Vetluver

Vic, Two thoughts come to mind, first why not find out why your E55 runs normally at 100 degrees. I would think it should be 85, 95 max. You may have a cooling issue. Thermostat? The other is, why not wrap your exhaust and precats with header wrap.

Man, your car's bottom is filthy, you ever pressure wash it?
Just kidding, it just doesn't match the flawless topside.

vrus

Yeah.. I have to get the thermostat and water pump checked on my car.. I've been suspecting that for a while.. Just dont want to bring it in to the service department right now and have them take the car apart. It is running great and I am afraid they will make it worse.

As for the header wrap.. I bought that a long time ago.. I have a 50ft roll just waiting in my garage.. Since I have the EVO headers which are already coated, I decided to use the wrap when I swap out the primary cats for my race cats that I ordered.. At that point, I'll wrap from the cats as far back as I can go.

P.S-> That picture under the car was taken in JANUARY during snow season! I put it up on a hoist because I was investigating building an exhaust system and wanted some pics. It's a little bit cleaner than that now.

P.S.S-> I have no garage queens in my arsenal.. I drive my cars all the time and this one goes through winters and summers so alot of the parts that should look shiny clean don't.. Besides, who the heck will be looking under my car anyways.. The only view anyone should have is the REARWARD ONE!