DIY Diffuser - LotusTalk - The Lotus Cars Community
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post #1 of 37 (permalink) Old 12-06-2014, 01:22 PM Thread Starter
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DIY Diffuser

I have been wanting to learn to tig weld for a long time. So, as an early Christmas present, I ordered the bundled Tig 200 and Plasma 60 from Eastwood. The Tig 200 is an entry level AC/DC inverter unit allowing to weld steel and aluminum. After it arrived, I spent the next few days practicing on thin .063 aluminum; basically the most difficult stuff to weld. After running through an entire 125 cf tank of argon, and finding just the right settings, etc.... I decided to embark on my first welding fabrication project.... A new diffuser.

I had the stock diffuser in place with a few minor mods to help improve performance: https://www.lotustalk.com/forums/f163...o-mods-221297/... but wanted to create a single piece unit, of an optimized design.

The stock and aftermarket diffusers all use a basic flat ramped cross section, which limits the amount of expansion possible (diffuser angle), before the flow separates from the diffuser. I wanted to see if I used a curved gradually increasing cross section, how much air expansion I could get, before I got flow separation. I started by conducting some basic CFD analyses and it turns out, you can get quite aggressive with the ramping. But this type of design certainly creates fabrication challenges. So with my basic design layed out, I got some large sheets of .063 aluminum and went to work. The plasma cutter made cutting the curved pieces a breeze. But again, welding such thin aluminum takes practice, patience, and a good heat sink behind the material you are welding.

I also fab'd up a new low profile exhaust tip. Welding stainless steel is a breeze compared to that aluminum...

This is what I ended up with. I still have to install some black aluminum mesh to cover the exhaust/license plate bracket to give it a finished look...

Fortunately, being a complete novice at tig welding, much can be hidden with a grinder and flat black paint.... but overall I am very pleased with the result.

.













I think the next project will be a new front splitter, incorporating a front diffuser...

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post #2 of 37 (permalink) Old 12-06-2014, 01:50 PM
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I'm learning to weld. TIG is the most difficult.

You did a really good job and have terrific fabrication skills.

I am v impressed.


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post #3 of 37 (permalink) Old 12-06-2014, 03:25 PM
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Love it, well done man!

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post #4 of 37 (permalink) Old 12-06-2014, 04:30 PM
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Impressive work. Should be easy to make the front splitter. Maybe do air foils for the rocker panels to match.
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post #5 of 37 (permalink) Old 12-06-2014, 04:43 PM
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Wow! That looks great, nice work.

Besides increasing the ramp angle, you can also widen at the back, creating more area or volume for expansion. Hard to do inside the limits of the bodywork but possible once outside of the back end of the car.

For the front splitter and diffuser, do you have an idea for where to exhaust the diffuser? The ones I have seen that appear to work exhaust behind the front wheels and vent behind the front tires as well as louvers on the tops of the fenders.
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post #6 of 37 (permalink) Old 12-06-2014, 06:07 PM
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Looks really good
Nice work

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post #7 of 37 (permalink) Old 12-06-2014, 06:53 PM
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Very nice design and fabrication! Kudos.

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post #8 of 37 (permalink) Old 12-06-2014, 07:15 PM
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Thumbs up!
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post #9 of 37 (permalink) Old 12-06-2014, 07:46 PM
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Awesome!..You should make the exhaust come out of the center vent like they did woth the Elise cup R. Either way it looks great
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post #10 of 37 (permalink) Old 12-06-2014, 08:43 PM
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Very nice! What was the final weight?
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post #11 of 37 (permalink) Old 12-07-2014, 12:29 AM
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The exhaust outlet treatment is nice.

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post #12 of 37 (permalink) Old 12-07-2014, 08:18 AM Thread Starter
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Thank you all for the kind comments...

Quote:
Originally Posted by TedR View Post
For the front splitter and diffuser, do you have an idea for where to exhaust the diffuser?
Not sure just yet. But space-wise it looks like the only location is into the wheel well, and then venting.... suggestions are welcome...
.
.

Last edited by da40flyer; 12-07-2014 at 10:00 AM.
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post #13 of 37 (permalink) Old 12-08-2014, 05:53 AM
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Very nice

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post #14 of 37 (permalink) Old 12-08-2014, 07:02 AM
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I love it.
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post #15 of 37 (permalink) Old 12-08-2014, 08:37 AM
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That is horrible, terrible, sooo unacceptable...

Just so you don't have to be reminded of this everday, I can only suggest that you immediately ship it to me (Please include any/all mounting brackets and if you could cut a hole for the stock exhaust exit)

I also like that you covered the thee vents on the engine pan. I never understood why Lotus is trying to do ground effects, and then added holes where you want low pressure


(Just to make sure my silly sense of humor is not misunderstood, I love your design)

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post #16 of 37 (permalink) Old 12-08-2014, 09:33 AM
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I want to make these in carbon fiber!!!!! It's the f****n coolest
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post #17 of 37 (permalink) Old 12-08-2014, 09:59 AM
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** save ~10 lbs gain 1 hp ** EQ: Y=(190*X) / (1984-X) where Y is (HP) and X is (lbs)

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post #18 of 37 (permalink) Old 12-08-2014, 11:03 AM
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That is some beautiful work!
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post #19 of 37 (permalink) Old 12-09-2014, 09:03 AM
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Well Done mate!

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post #20 of 37 (permalink) Old 12-09-2014, 11:24 AM
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Aesthetically, I think your rear diffuser is a huge improvement over stock! Functionally, it is likely to be only a slight improvement -- primarily from better separation of the disturbed air off the rear tires from the central part of the diffuser.

As to the central part of the diffuser, wind tunnel studies have shown the appropriate discharge angle is proportional to the length of the "undisturbed" airflow area ahead of the diffuser deflection point. In other words, the central diffuser exit should be steeper than the sides on our cars. But, package constraints often dictate otherwise so we get what we can.

Because our Eliges have so little front overhang, front diffusers similar to the rear type may not be feasible. Better to raise the center section of the splitter to pump more air to the rear diffuser then decrease the rear wing (drag) to end up with a faster car. At the front, fair in the splitter to body area and you can create a small diffuser effect if you have a deflection point where this fairing meets the flat underbody.

If you want to get really wild, there always are guide vanes and vortex generators (often the same thing) to minimize the high pressure zone ahead of the tires. A DTM Elige, anyone?

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