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Old 07-23-2018, 11:06 PM   #1 (permalink)
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Mercedes w126 300sdl aeromods 2.0



Here's a car with the same chassis as mine with the aerodynamic template overlain.

Some "progress"
https://ibb.co/3Mw5N1r
https://ibb.co/54wNkwR

Feel free to correct me if I set it up wrong.

I built a decklid extension last night. I Was thinking 4 sided box cavity/ psuedo boat tail, but as with most things in life, I may have dove in too soon.

I read a few threads last night whilst half asleep and now feel as if I can actually do something worthwhile now.

The decklid extension stays for now. I'm going to try my hand at rear partial belly pan and get my front air dam sorted.

I removed the rear bumper for a trailer hitch receiver, I may just leave it off. I'm thinking of routing my exhaust between the hitch and body, separate from the under body air.

In my mind I'm building a small diffuser for the bottom side of the pseudo boat tail and the exhaust will vent inside the box.

What I am worried about is poisonous diesel exhaust making its way back into the cabin. Do I need additional air introduced at the same plane? Maybe route the radiator air between the floor pans and under tray?


Last edited by razordave; 12-06-2018 at 02:27 AM..
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Old 07-24-2018, 07:30 AM   #2 (permalink)
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Quote:
Originally Posted by razordave View Post

In my mind I'm building a small diffuser for the bottom side of the pseudo boat tail and the exhaust will vent inside the box.

What I am worried about is poisonous diesel exhaust making its way back into the cabin. Do I need additional air introduced at the same plane? Maybe route the radiator air between the floor pans and under tray?
Aren't all exhaust fumes corrosive?

In any case they contain a lot of moisture, you can sometimes see water or other liquid dripping out the tailpipe.

You do not want to trap or collect this in any way in my opinion.

I did a quick search on this topic, and it looks like one solution is to use the force of the exhaust to induce more airflow along a diffuser plane.

Exhaust Blown Diffuser

Quote:
Blown diffuser on Senna McLaren-Honda MP4/7A during Mexico GP 1991. He suffered a big accident at the high speed Peraltada corner during qualifying, in which the car rolled and landed upside down) but thankfully he emerged unscathed.

Quote:
In recent years, the effect of the exhaust on the centre of pressure, and its variation with throttle opening have led to the true blown diffuser being abandoned,............

Quote:
Effectively the harder the air flows over the diffuser, the more powerful the gurney can be in puling airflow from inside the diffuser; this makes the diffuser act as though the exit is larger and makes more downforce.
You may not have a race car that needs extra down-force, but the examples in that article show that there is more than one way to do things.

And none of them allow exhaust gases to collect in an open ended box.

Maybe this visual below can be used to establish a concept or at least a launching point for one.

http://www.rapid-racer.com/aerodynamic-upgrades.php


I'm assuming that the exhaust will be at both a higher pressure and faster velocity than the rest of the air leaving the underside of the car.

I know that under normal circumstances the faster moving the air the lower the pressure, and the slower the air is moving the higher the pressure.

However, the exhaust has the energy of the entire engine behind it, it's not like the normal air going under, over and around the car, right?

I'm visualizing the exhaust as a continuing firing shot gun blast, just to get my big picture going.

Maybe a fire hose or a waterjet on a jetski are better compatibles?


Rear Diffuser and Exhaust Gases:
http://www.rapid-racer.com/aerodynamic-upgrades.php
Quote:
By incorporating the exhaust system into the rear diffuser, you can also help extract the air from the rear of the car more effectively. The exhaust gasses produced effectively energise the airflow, helping to raise the low pressure air the diffuser creates by amplifying the suction effect. This fast moving air flow returning back to the ambient atmospheric pressure at the exit of the diffuser, reducing drag levels. Hot exhaust gases also aid in expansion, again aiding in the airflow speed transition between fast moving underbody air and slow moving ambient air. Resulting in higher vacuum effect, more downforce and reduced drag.
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Last edited by kach22i; 07-24-2018 at 08:24 AM..
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Old 07-24-2018, 10:23 AM   #3 (permalink)
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Thank you for your well organized thought out response.

I was only looking at land speed cars and would have never thought to look to formula1. I once was reading about college students trying to improve on the radiator shroud on an Indy car and it didn't take long to realize I was in over my head.

I was considering a catamaran style wheel enclosure like aerocivic, my exhaust is currently directly behind my rear wheel and would need moved for that project.
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Old 07-24-2018, 10:28 AM   #4 (permalink)
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No problem, it was fun doing the research and using my mind on a different sort of problem than I normally face.

I got to learn something new in the process.
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1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
1989 Scat II HP Hovercraft

Chin Spoiler:
http://forums.pelicanparts.com/off-t...effective.html

Rear Spoiler Pick Up Truck
http://forums.pelicanparts.com/off-t...xperiment.html

Roof Wing
http://ecomodder.com/forum/showthrea...1-a-19525.html
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Old 07-25-2018, 12:47 PM   #5 (permalink)
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M-b 300

Quote:
Originally Posted by razordave View Post


Here's a car with the same chassis as mine with the aerodynamic template overlain.

Feel free to correct me if I set it up wrong.

I built a decklid extension last night. I Was thinking 4 sided box cavity/ psuedo boat tail, but as with most things in life, I may have dove in too soon.

I read a few threads last night whilst half asleep and now feel as if I can actually do something worthwhile now.

The decklid extension stays for now. I'm going to try my hand at rear partial belly pan and get my front air dam sorted.

I removed the rear bumper for a trailer hitch receiver, I may just leave it off. I'm thinking of routing my exhaust between the hitch and body, separate from the under body air.

In my mind I'm building a small diffuser for the bottom side of the pseudo boat tail and the exhaust will vent inside the box.

What I am worried about is poisonous diesel exhaust making its way back into the cabin. Do I need additional air introduced at the same plane? Maybe route the radiator air between the floor pans and under tray?
Wanted to know if you'd seen the M-B 190 EVO?
*A rooftop deflector,fitted to the template might help manage flow off the top.
*On the 190 EVO,you can see that the base of the rear wing projected back at least as far as the rear bumper did.
*If your deck extension went that far,then,at that length,you could angle it up to reach the template contour.
*You could also do a bi-wing as with the mid-1980s Ford Scorpio/Merkur XR4Ti.
*With the 2013,M-B IAA,you can see how they pushed the rear of the car near the template,for Cd 0.19.And you can see how the little boat tail extension reaches at an angle up to the template contour.
*Your tail could do likewise.
-------------------------------------------------------------------------
*As to the exhaust,it would be good to extend the tailpipe to the side or down through the bottom of the new diffuser to get that area washed by the air stream.You don't want the exhaust to have any chance to find a way into the cabin.
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Last edited by aerohead; 07-25-2018 at 12:49 PM.. Reason: typo
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Old 07-25-2018, 09:23 PM   #6 (permalink)
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Mercedes did a w126 aero concept:



https://wikicars.org/en/Mercedes-Benz_Auto_2000_Concept
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Old 07-25-2018, 09:57 PM   #7 (permalink)
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The evo ii may have some things I could implement, from what I thought of the merkur, those wings would have to be wind tunnel tested and perfect.

Does anyone know where the top of that wing is in relationship to the roof on the evoii? I guess their goal was more downforce, so it's probably higher than the aero template.

That mercedes 2000 is pretty crazy looking.

Here's today's "progress."

Started with a partial grille block


Then drug out the old air dam and made a couple modifications before reinstalling.


Then a little paint


Here's the trunk decklid extension in progress


And some paint back there
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Old 07-26-2018, 10:13 AM   #8 (permalink)
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This one?

MERCEDES BENZ / 190 E 2.5-16 Evolution II
https://www.autoevolution.com/cars/m...ii-1990-25-16v

Quote:
Racing models had a reduced drag coefficient of 0.32, more prominent and aerodynamically shaped wheel arches, lower front and rear bumpers complemented by sporty sidekirts, 6-spoke alloy wheels and a huge rear spoiler for increased stability.
Hey razordave, I'm digging the progress.

Need a cute name for your creation, like hoodwinked or something.
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1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
1989 Scat II HP Hovercraft

Chin Spoiler:
http://forums.pelicanparts.com/off-t...effective.html

Rear Spoiler Pick Up Truck
http://forums.pelicanparts.com/off-t...xperiment.html

Roof Wing
http://ecomodder.com/forum/showthrea...1-a-19525.html
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Old 07-26-2018, 10:40 AM   #9 (permalink)
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That's it.


I've been looking for alumalite sheeting, haven't been able to find it free so I'm considering corrugated roofing or maybe a bed liner for my undertray.

I think I'm going to tackle smooth wheel covers first, then either wheel skirts or under tray next.
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Old 07-28-2018, 01:03 AM   #10 (permalink)
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Quote:
I've been looking for alumalite sheeting, haven't been able to find it free...
Free would be a very good price. Roofing would need deep corrugations to be stiff enough unless you can shingle together scraps to stiffen them and get the area desired.

I've not seen a bed liner that wasn't semiflexible.



I'm looking at that 'fast moving, low pressure air' arrow and wondering if the openings in the airdam are big enough. If you cut out that center bar, you'd have a central jet between some massive wheel spats. With opportunity to add side plates to tie the airdam to the bumper and form an air curtain over the front wheel.

*Which would consist of two pieces — a triangular restrictor plate in front of the tire and a structural flat plate. The restrictor would be spaced an inch, give or take, from the inside of the flat plate. Whether it needs to be under-lapped or over-lapped (slot faces back or out) needs some thought.

With skirts you only need two wheel covers. If it's a 'Turnpike cruiser' style skirt that runs all the way back to the taillight you can control the contour there.

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Last edited by freebeard; 07-28-2018 at 01:21 AM..
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