Engine fan air volume for a 280SL

[TR]

Does anyone have info on the max. air flow volume (hopefully in CFM) that should be delivered  by a properly functioning 280SL cooling fan?

Tom in Boise
'71 280SL 4-spd, signal red w/lt. tan interior, restored/enhanced

[TR]

Perhaps I should add the reason I'm looking for this info.  And that is I'm hoping to be able to do a comparison of CFM delivery between the 280SL's standard fan mechanical fan and electric fans.  I'm looking at a set of electric fans than reportedly deliver 3,000 CFM.  No idea, however, what max. CFM the normal fan delivers.  I guessing it's less than 3,000 CFM though.

Tom in Boise
'71 280SL 4-spd, signal red w/lt. tan interior, restored/enhanced

[Tom]

Tom,

Would you replace the existing fan for the new electric fans or would this supplement your existing fan?

Best,

Tom


1971 280sl Tunis Beige Metallic (restored & enhanced)
1971 280sl Tobacco Brown (low mileage stock)
1970 280sl Deep Red (Project Car)

[TR]

Tom -- We've already pulled the original fan and stored it away, and installed a 3-fan arrangement (electric) that reportedly delivers a collective 3,000 CFM.  I'd really like to know how this compares to the orig. fan's volume.  I'm not certain, but suspect that's more than the orig. fan.

As we've discussed, I'm trying to come up with a cooling arrangement that will allow a late-model 280SL to hold engine temp. under any & all conditions.  And by this I mean in 108 degree weather (which we've been having here) with the top down, the Frigiking A/C compressor running all the time, while setting dead-still at idle for 1/2 hour, or climbing a 7 percent grade (steep!) mountain for miles while running the engine hard (all at 100+ ambient temperature).

Of course, new cars have no problem doing all of this.  But as we all know this is difficult (understatement) with a 280SL / M130 engine loaded down by A/C, which my wife demands run on full cold all the time.

BTW, with the soft top up the Frigiking will freeze you out in 108 degree weather.  However, our objective is to drive the car cross-country in 100 degree weather (or <50 degree weather for that matter) with the top down, and to be comfortable hour after hour (like a CLK500 cabriolet will definitely do).  In other words, we want to drive the car almost all the time with the top down, and not be uncomfortable by my wife's standards (which are, shall we say, "high").  I think I'm pretty close to achieving this...

If anyone has that air flow info for a normal mechanical fan I'd sure like to know what it is.

Thanks.



Tom in Boise
'71 280SL 4-spd, signal red w/lt. tan interior, restored/enhanced

[Tom]

Tom,

Were you able to install ventilated seats and retain the original seats?

1971 280sl Tunis Beige Metallic (restored & enhanced)
1971 280sl Tobacco Brown (low mileage stock)
1970 280sl Deep Red (Project Car)

[TR]

Tom -- Yes, all the new seat mods are now in...and they feel great!  Although I've driven the car very little since the interior work was done.  Part of that effort included the addition of seat heaters, 2 large muffin fans in each cushion (both bottoms & backs) for active ventilation, plus massagers in each seat back.  All of this stuff fits fine within the four new seat cushion pads.  I'd say the old 280SL's seats are now as comfortable as those in a new M-B, and I don't make that claim lightly.  And the only thing that would be obvious to a W113 guru is that the seat pleats are now shallow with a single stitch, and the seat facing surfaces are all perforated…both of which are needed for good air flow from the new in-seat fans.  The new seat controls are hidden inside the ashtray.

This is the proverbial never-ending project.  Since the weather here has been so hot for so long it is an excellent time for the mechanics to experiment with engine cooling ideas.  We thought we had it whipped when it comes to idling for very long periods, but then discovered the car would rise more in temp. that I'd like while aggressively climbing Idaho's mountains (which are significant).  This link will give you an idea of the sort of country-side and steep roads I expect this 280SL to be able to handle during the worst heat of summer (ie. 100+ degrees): http://texas.sierraclub.org/austin/sawtoothfence.jpg

Right now we’re trying a little under-bumper air dam/scoop experiment in order to hold temp. better while climbing those steep and miles-long grades.  These mods are being loosely modeled after the CLK500.  Still have some work to do on that prolonged idling thing though.  Again, I won’t be satisfied until this ’71 280SL will hold temp. at idle for 30 minutes with the A/C working its heart out and everything is hot as a pistol.

That's why I'm so anxious to learn if anyone knows the CFM spec. for the original fan...

Tom in Boise
'71 280SL 4-spd, signal red w/lt. tan interior, restored/enhanced

[JimVillers]

Tom ... I am coming to this discussion way late, it sounds like it has been going for multiple threads.  My two observations are that you will probably need to upgrade your alternator and more to the point, have you looked at higher capacity radiator cores.  When I had my radiator re-cored, there were several options on the number rows of channels.  If I remember correctly, I installed a three row core but I believe that there was also a four row core available.

Jim Villers
190SL, 230SL 5-Speed, 190E 2.3-16 Kompressor

[TR]

Jim -- Thanks for the reply.  Yeah, we've replaced the radiator a few times already.  Reportedly with the heavy-duty units.  Although I think we just might consider giving it one more try.  I'd be pleasantly surprised if anyone can suggest something we haven't already tried (including a new long-block engine from Metric!).

Also, we've upgraded the std. alternator from, what 50 amps(?) to a new 150 amp unit.  We have electrical delivery power to spare now.  Just for kicks I had them add a 750W (1.5KW peak) power inverter in the off-chance I should ever need a little bit of 110VAC while driving down the road.

Any idea as to what the air volume spec of a '71 280SL's standard fan might to be?

Tom in Boise
'71 280SL 4-spd, signal red w/lt. tan interior, restored/enhanced

[JimVillers]

Tom ... From the sounds of it, you are not concerned with "originality".  With that said, you can install a much larger radiator that extends 4 or so inches below the bottom of the current radiator.  If you get serious, try C&R Racing Radiators - http://www.crracing.com/



Jim Villers
190SL, 230SL 5-Speed, 190E 2.3-16 Kompressor

[A Dalton]

If you are looking for sustained cooling at long idle, you may want to use one of the later Benz aux water pump set-ups and do some plumbing from the back of the head like the modification kit they use, except with the force of the extra circulation pump, in-line.


?

[TR]

Jim -- Hmmm...  Extending the radiator downward is not an idea that's come up before.  Thank you; I'll have my mechanics look into that.  There is so little available space in either the Z or X axes, that perhaps some added heat exchange area in the Y-axis might make good sense.

We have tried everything, and I mean everything, of original W113 design and cannot get the engine to hold temperature in those very tough conditions that I've described (e.g., in ambient temperatures of 100+ degrees, with the A/C compressor running flat out all the time (not cycling on & off), for prolonged periods of say 30 minutes, at idle with zero movement, or while climbing steep mountain roads (say a 7 degree grade) for several miles while driving aggressively (say at 5,000+ RPM).

My guidelines to the mechanics are; 1) keep things fundamentally original...meaning it should not be too tough to return to all orig. if & when the mood ever strikes, and 2) save all the parts that come off the car, but 3) for God's sake, give me a car that my wife can stand to be in.  Her idea of a good time is NOT having to suffer with anything less than current standards of creature comfort.  However, she gets it, relative to the rarity & coolness of an excellent vintage W113.  Also, I'm finding it entertaining to add new elements that might even go a little beyond what one can get an a new M-B.  For example, my buddy recently took delivery of a brand new SL65.  Now my 35-year old 280SL has seats that run the same back massagers as his new AMG-version 600SL.  But he doesn't have that in-line heater for windshield fluid that will do a good job of removing bugs because its sprays at 150 degrees ... and came from the same German OEM vendor that supplied his back massagers as well as mine.

I'll keep asking though; anyone know what the air movement volume is supposed to be for a standard 280SL engine fan?

Tom in Boise
'71 280SL 4-spd, signal red w/lt. tan interior, restored/enhanced

[TR]

Dalton -- Thanks, but we've already done exactly that.  I believe both of those mods have helped...but we're still not quite there yet.

Anyone know the volume of the standard fan?

Tom in Boise
'71 280SL 4-spd, signal red w/lt. tan interior, restored/enhanced

[JimVillers]

Tom ... There should be a lot of room below the radiator.  I remove my radiator out the bottom so there is space there.  A high capacity aluminum radiator core should also have more capacity than the standard one.  A fan down low might be difficult but helpful for extended idling.  A "normal" heater blower fan might fit and not be visible.  If not, Electronic equipment cooling fans might move enough air to provide the incremental cooling that you are looking for.  Remember that you would not need to blow air through the A/C heat exchanger so it should be more effective in cooling the engine.

On you question about the capacity of the standard fan, if you are trying to move air through the A/c coil and the radiator, I would keep/use all of the fans available.  My 230SL does not have the viscous hub and it does move some air.


Jim Villers
190SL, 230SL 5-Speed, 190E 2.3-16 Kompressor

[waltklatt]

Tom,
You might want to try a neat little gimmick.
Have a mechanism that will elevate the back of the hood to allow more air to come through the top of the engine and out the rear.
I've seen many police cars and cabbies pop the hood release from inside and drive around the city traffic with the hoods ajar, but still on the safety catch.
Walter
1967 230SL-diesel with W201 radiator and electric fan.
1963 230SL-stock and sitting.

[George Davis]

Tom,

no data in the data book about the fan volume, but here's a guesstimate, based on info for an 18 inch, 8 blade Flex-a-lite electric fan, which operates at 2200 rpm and has 2800 cfm airflow.

Fan airflow curves aren't linear (I think), but for estimation I've assumed they are.  Your car idles at about 1/3 the speed this fan is rated at, therefore a very rough estimate is that the airflow is also about 1/3, so maybe 900-1000 cfm.  In fact, with the viscous coupling, fan speed is probably slightly less than idle speed, and I don't think our fans are 18 inches in diameter; these factors will lower the airflow even more.  I know this is way rough, but I think it's pretty safe to conclude your 3000 cfm setup (is that right?) exceeds the factory fan by quite a lot.

George Davis
'69 280 SL Euro manual

[TR]

Guys -- Thanks for your kind inputs.  Please excuse this lengthy reply.

George – I suspect you won’t be too far off in your rough but educated estimate of CFM for the std. mechanically driven fan.  I've asked the local M-B dealer to dig into an engineering-level answer for this.  I'm sure they'll give it a good effort, and in the event I learn the answer I’ll post it here if anyone is interested.

Jim -- This may take awhile, but we'll check further into your suggestions.  I find them quite interesting.

Walt -- We've tried popping the hood latch, which gives a decent opening at the rear of the hood (what...maybe 1-2 inches?).  Surprisingly though, this didn't seem to do much.

Edited to remove unnecessary banter between members. - Moderator


Tom in Boise
'71 280SL 4-spd, signal red w/lt. tan interior, restored/enhanced

[waltklatt]

Tom,
It's a long shot in the dark here.  
Umm, the whole point of this exercise was suddenly clear to me as your goal is to achieve a cool car while being subjected to the high heat loads while under load with the A/C, under the intense sun and high ambient temparature.  Correct me if I'm worng.  
My next thing is after your exchanging the radiator for a high efficiency one, electric fans and other cooling aids.  I guess it all boils down to the direction of the air flow.  The engine builds up heat and then is transferred to the water/antifreeze and then transferred to the radiator, with me so far?  Now the radiator gets hot and then the electric fans blow cool or ambient temperature air through the fins and then where does this hot air go??  Back to the engine right?  Which brings me to this, after all the mods the heat is being transferred back to the motor again in a big cycle.  
Well maybe a pair of supplementary radiators with fans inside(behind the headlights) the wheel wells might help alleviate some of this heat.  You could modify the headlight housings a bit to allow a flow of cooler air or a set of NACA ducts under the bumper to direct the air up behind the headlight pods.
Go ahead and tar and feather me here for the non-purist idea, I can take it.
Walter
1967 230SL-non-purist diesel conversion
1963 230SL-sitting unloved in the garage

[TR]

Walter – My God…you sir, are a brilliant man!  And you are certainly no nattering neigh-bob of negativity!!

What you are proposing, i.e., a supplementary pair of small radiators with fans inside the wheel wells, is precisely a backup plan that we currently have in our hip pocket.  I always pester my mechanics (friends) with, "so, what's your 2-deep contingency plans if our current approach doesn't work?"  And we've already scoped out this backup approach, almost precisely as you’ve described.  Should we need to use this contingency it might be next summer before we get around to it.  But you got to this idea amazingly quickly…certainly faster than we did.

BTW, my M-B mechs started out saying whimpy things, like, "oh, well, you know these cars were designed for Europe where the summers are cool” ... or, “these cars were never intended to run air conditioning”... or, “these cars are just not capable of taking it".  I'd listen to them as patiently as I could, then ask I’d if they'd ever been to Europe in the summer?  After they worked thru their various excuses of why it couldn’t be done then I'd get around to asking them if they were really that intent on trying to prove to themselves and to me that Mercedes-Benz engineers of the 60s & early-70s were really such a bunch of incompetents.  The worst automotive engineers in the world?  Now that’ll get 'em going!

Well, who knows what the outcome will be?  But I figure it is almost cowardly to not try.  Hey, what's the worst that can happen?

Thanks Walter.  Please keep thinking about this … because I’m sure we need all the positive input we can get.  Of course if we ever do “get ‘er done” then I’ll be happy to share what we’ve learned with anyone who’s interested.  However, we’re still not quite there yet.  Who knows?  Maybe we never will achieve those targets I’ve sat.  But the car is now doing better than it ever has in the 20 years I’ve owned it.

No tar & feathers for you my friend.  If you were here I’d stand up and salute!

Tom in Boise
'71 280SL 4-spd, signal red w/lt. tan interior, restored/enhanced

[norton]

Tom sorry I cant help with the CFM of the stock fan, But it cant be much at idle. Just a couple of ideas here that maybe we discused before , are you using Propylene glycol or Ethylene glycol - Propylene cools better. What water to antifreeze ratio are you using - water transfers heat better than antifreeze, a mix of 25% Propylene 75% water may help. I would guess that your allready using "WaterWetter"
    The extra rads in the wheel well is a great idea, what about just fans or ducting to move the hot air out of the engine compartment. Have you tried heat wrap on the exhaust manifolds to reduce underhood heat.
  I'm also thinking of an old motorcycle trick where you would coat the inside of the exhaust pipes with white heat paint, this would reflect the heat, and keep it in the pipes. (this was used to keep the chrome on the pipes from blueing)
   What about opening up the area behind the grill to allow some air flow into the engine compartment?

Mike Halleck
Chesterfield Mi
71 280SL
68 250SL (parts car)
94 E320 Coupe

[TR]

Mike -- I'm not sure what coolant mixture the guys are running right now.  But I know they've put thought & effort into it.  Initially they put some racing coolent material (expensive!) in it to make sure we didn't get into a boil over problem.  I suspect that move may have saved the new Metric engine, or at least the head.  But I think we're beyond the potential damage point now.

That's an interesting idea you brought up about opening addt'l area behind the grill for more air flow.  If I understand you correctly that would involve some cutting of metal, which to this point we've avoided.  However, I'll pass along your idea that to them as another contingency/back-up plan.  Thank you for that input.  If we did cut, and then later wanted to put it back to original configuration I rather suspect we could (not certain about this though).

Tomorrow they're going to go over it again with an IR gun looking for hot spots.  This is nothing more than intuition on my part, but I have a hunch we still have a radiator issue ... even though it's been replaced/checked, etc.

Tom in Boise
'71 280SL 4-spd, signal red w/lt. tan interior, restored/enhanced

[mdsalemi]

Hey Tom and others,

As anybody given any thought to increased coolant volume and flow?  I see all the information regarding air flow; how about considering coolant volume and increased flow via a different water pump?  You may have to fabricate one but considering all the other things you are doing...

You know in race engines they have a problem with oil volume and flow and thus have dry sump systems; maybe the same kind of logic applied to cooling would be a consideration here.

Oh, and when you've figured out how to reduce the ungodly heat in the passenger compartment let me know!   To me it seems like the heat is always on, but I know it is just radiant heat from the engine.

Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored

[tuultyme]

Since it has been said that Oil is also a means to remove heat from the engine one may try to see what happens with more oil capacity.  Another thing to try would be to move the oil cooler into the fender wells or some other suitable place and away from the radiator so the hot oil heat is not transferred to the engine coolant as readily.  How do the larger cars of the same year; SE & SEL's function in terms of heating up as the A/C is used more in the Hot weather?  Do they possibly function better because of the increased engine space?

Bruce; 268Blaugrun(green) 1970 280SL; IL

[TR]

Mike -- Yeah, my lead mechanic went thru several new M-B water pumps, even making clay impressions of the impellers, in order to select the best performing one.  He reported surprising variability between 4 brand new water pumps.  Then he also installed that special head recirc kit, along with a large re-circ pump with a good deal of extra tubing & piping, which added considerable coolant volume.  In addition, Gernold did a small modification to the throttle body that is supposed to help, although I'm not sure about those details.

All this thoughtful input from you guys is great!  I'll pass it along to my mechanics (friends), one of whom recently came back from maintenance training for the new SLR McClaren.  I only add that last part to indicate he's no dummy, and is skilled on some of the latest high-performance stuff.  Still, this old 280SL cooling issue is a real challenge, that no one out here has dealt with before...not to this level at least.

I really enjoyed our conversation the other day.  Funny that we were visiting the Lewiston mill at about the same time so many years ago.  BTW, I'm still expecting those other 2 wheelcovers.  I'll let you know when they show up.

I'm sorry to hear about your ungodly hot cockpit.  I see no reason why we should be miserable in our cars during the best time of the year to use them.  I suspect I'm not alone in not wanting to be restricted to comfortable use during only the spring & fall.  (probably many of us wouldn't take them out in the dead of winter).  We've added many, many pounds of Dynamat Extreme sound/vibration absortion material through the car; including under the dash, under the carpets, inside the doors, etc.  I'm not certain about this, but have been told that it doesn't hurt when it comes to insulation.  It sure makes the whole car a LOT more quiet, and I suspect a little cooler.  You might consider something like this(?).  I assume you don't have an A/C?

Tom in Boise
'71 280SL 4-spd, signal red w/lt. tan interior, restored/enhanced

[TR]

Bruce -- Thats an interesting thought.  Sounds rational and makes intuitive sense to me.  I'll pass along your idea to the team.

Thanks.

Tom in Boise
'71 280SL 4-spd, signal red w/lt. tan interior, restored/enhanced

[norton]

To add to what Bruce has said, At the 113 Tech Session Joe showed us the newer replacement oil pan. It holds more oil and also has some scraper/diverters cast into it.

Mike Halleck
Chesterfield Mi
71 280SL
68 250SL (parts car)
94 E320 Coupe