Rad blind experiment

[Dieselman]

Originally Posted by maddog

There should be no need for a blind on an modern motor car, not in the UK anyway sounds like someone has been watching Ice Road truckers

How fast are those lorries going then...not fast enough for aerodynamics to have any effect...are they?

As far as no car requiring blinds, why do some manufacturers fit them then...they could save a few pounds if only they listen to maddog...you need to contact them, they need your input..

A low heat output car does benefit from a blind as heat is lost from the engine block, not just the radiator, but if you actually read the post you'll see that not why it's been fitted...the test is to ensure it doesn't overheat, not to assist warming.

[Dieselman]

Originally Posted by lynall

Quick google reveals e300td 97 on rad core size 640x490x40 same core size as my 430, site didnt list e55 and i was to lazy to look any further .

Thanks Lynall.

The 430 must be losing about 250kw or more of heat which is way more than the 300TD can generate, so reducing it's working area should still leave a considerable reserve.

Obviously the grille is designed for the maximum loss required, which is also way too large for this application.

[kth286]

Originally Posted by maddog

There should be no need for a blind on an modern motor car, not in the UK anyway sounds like someone has been watching Ice Road truckers where the purpose of the blinds is to INCREASE underbonnet temps to prevent damage to electrics.

Cue the "I've fitted a starting handle to my car" and "Where can i buy wire spoked wheels for my E class " threads

Dieselman is doing this to a great extent to gauge the aerodynamic effect and whether the car will slip through the air more easily and give more economy, and be quieter etc etc.

I guess he was prompted by the recent articles re the latest Merc bluetec models appearing on the market that give better economy via the use of various aids such as this one and numerous others.

I have considered these myself and the potential for retrofitting various aids to economy, and there are plenty of things we can do.

[Bobby Dazzler]

In the same way that there is a tension between drag and downforce on racing cars - often mentioned in F1 commentary - there is a similar tension between drag and cooling, both on racing cars and on road cars.

Creating downforce by definition creates drag. Similarly cooling the engine by definition creates drag, whether that be via the cooling system or reduction of underbonnet temperatures.

Originally Posted by grober

Does this not mean your underbonnet air temperature will rise---not the engine you understand since its got a direct coupled means of cooling via the "part rad"--- but the air space and with it all those sensitive little sensors/ECU'S which don't like it hot??? Surely a better solution would be to arrange additional "exits" via louvres under the wings or on the bonnet assuming they didn't screw with the aerodynamics??

Underbonnet temperatures may rise slightly, but hot air is drawn out of the engine bay from the low pressure areas, rather than pushed out from high pressure areas. If air is able to exit, then it will draw cool air in through the reduced aperature.

Originally Posted by Dieselman

Something I noticed the other day on the motorway when it was wet, was that there seems to be more air passing over the bonnet, enough for the emblem to make turbulance and spray water droplets backwards.

The blind will create a larger stagnant volume which, is likely to spread up rather than down, and will deflect a little more air over the bonnet than may otherwise be the case.

I wouldn't expect the turbulence to increase significantly though, maybe even reduce. The air passing over the bonnet wouldn't accelerate more than usual, and the greater stagnation would likely smooth the radius and therefore the path of air passing over the bonnet. It would be marginal though.

Might just be more noticeable given the damp/wet conditions of late.

I love driving in the rain, because it opens up a whole new dimension is seeing your car work. You can see things you otherwise wouldn't see - marvel at the airflow around the A-pillar for example.

Originally Posted by Dieselman

As 230k says, don't block the under grille because of the intercooler, but also because that's in a very high pressure, stagnant air area so works very well without creating much drag. The bonnet grille is in an area of faster moving airstream and causes more drag.

Stagnant air at the intake maximises the potential difference between inlet and outlet, and therefore maximises air flow through the engine bay. The stagnant air isn't what's causing the drag though.

The benefits here will come from reducing drag 'inside' the car, rather than 'outside' the car. Drag caused by air passing through the radiator is considerable, and generally significant around the other gubbins found in the engine bay.

[Bobby Dazzler]

I had some airflow diagrams of the W210 estate somewhere. I'll see if I can dig them out - I suspect they went to the tip when I cleared out the garage though.

[Bobby Dazzler]

What have you done DM??!! I appear to be reigniting old flames of interest that I thought had long since been extinguished!!

Whilst it appears to be a HGV powertrain and chassis, there's an interesting CFD sim here, showing airflows related to underbonnet cooling:
http://www.mira.co.uk/Services/Consultancy-Thermal.htm

A little small, and lacking detail, but it's the right car!!



More detail, but a W204 this time - notice that the high pressure area is closer to the lower intake more than the upper grille.

[230K]

Dieselman

While out for a walk this morning i noticed a few cars getting the same treatment.

This one has adjustable flaps.




And this one has been given a whole new look.


Couldnt resist

Dieselman, don't rise to it!!

I would be really interested to hear if it improves fuel consumption.

230k

[popuptoaster]

Tis true most cars here ARE over cooled as standard because its cheaper for a manufacturer to fit the same rad across europe (cold at the top, hot at the bootom) than it is to have to fit bigger or smaller ones. I do lots of engine swops and us lot tend to work on how much BHP a specific rad will cool in this climate, as a general rule its twice as much as the biggest engine fitted to that model, a sierra cossie rad will cool 500bhp for instance, so running the standard 200bhp motor, you could block off over 50% of it and still keep the engine healthy. My 200bhp Cortina had a rad designed for a 140bhp engine in it as it was the biggest one i could get in with cutting metal and it kept it cool even blatting it round a track in the summer, my old W115 Merc rust bucket had nearly all the lil fins missing off the rad but it still kept it cool all last summer, even in traffic, My coupe is having trouble getting up to temp in the snow, the thermostat is working but the temp guage still wont reach its normal postion, even after a 60 mile run, so i've been wahcking the cardboard on the rad during this snowy weather to get that legendary shoe burning power back into my heater.

[Dieselman]

Originally Posted by 230K

And this one has been given a whole new look.


Dieselman, don't rise to it!!

I would be really interested to hear if it improves fuel consumption.

230k

Ohh, why not...nice subtle mod...and the bonnet bra could be good for stopping chips...and look at that aerodynamic wiper delete mod..looks just like a Merc now..

fuel economy...

Just been to fill up..!

At the halfway point of the tank it had covered 370 miles, so was short of my record 405....then I fitted the blind and went for a few miles thrashing to observe temperatures..
Since then It's been normal mixed driving, but I'm sure it's more stable on the motorway.

Ok.
When I achieved 405 to half a tank I got 696 to the tank. There was a bit left but it was pretty empty, so today I filled at 701 miles..

That's a gain of 35miles in under half a tank, including performance testing the mod..

I'll keep a tally and see how it goes.

[Dieselman]

Originally Posted by Bobby Dazzler

What have you done DM??!! I appear to be reigniting old flames of interest that I thought had long since been extinguished!!

Whilst it appears to be a HGV powertrain and chassis, there's an interesting CFD sim here, showing airflows related to underbonnet cooling:
http://www.mira.co.uk/Services/Consultancy-Thermal.htm

I've got the 210 pic..had it as my avatar for a while...

Manufacturers have taken their eye off the ball with respect to aerodynamics, but Mercedes have always been pretty good in that respect, most have gone backwards. If you want a car to go fast safely and quietly it needs good aero.

You need to look at the acomodded forum.. Those guys have got it off to a Tee.

http://ecomodder.com/forum/showthrea...ower-6341.html

[nimishashar]

Hello,

I read with intrigue this post, however there is one thing that concerns me more so, and that it the fact that you would be affecting the performance of the MAF and that as we know does have a significant effect on the performance of diesels. your thoughts on this would be appreciated

[Dieselman]

If I read that right do you mean that due to drawing in warmer air it would reduce performance.
The air intake is to the O/s of the grille so that's why I left that section exposed, in addition the blank is inside the grille so air can still flow through and channel off to the intake unrestricted.
I need to take measurments but the intake could possibly be under greater pressure as the air cannot pass through the blind.

After I had completed a journey I felt the intake ducting just after the MAF and it was stone cold.

[spock500]

What would be cool is if you could make the slats in the front part of the decorative grill open and close similar to a set of window blinds.



That way air should be deflected over the bonnet when they are closed.

PS, and fit some machine guns instead of those headlamp washers

[Number_Cruncher]

>>and that it the fact that you would be affecting the performance of the MAF

Actually, no. The MAF measures Mass Air Flow, and so the air density changes caused by temperature changes are automatically taken into account by this kind of sensor.

Older air flow meters, like those used on K jetronic, L jetronic, and earlier Motronic systems would read in error as air temperature changed.

This automatic compensation for temperature effects, and the quicker response of a small filament compared with the inertia of a flap are the main reasons this type of sensor is now almost universal.

[popuptoaster]

As far as cold air for the intake goes, you only want cold air for max power at full throttle, for good mid range and tractibility you want warm air into the intake anyway, so blocking the feed isnt a massive issue for normal driving.