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Old 05-27-2019, 06:25 PM   #1 (permalink)
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Diffuser for the Fiat 500e!

Hi All, there is finally a custom made diffuser that fits the 500e. In a continuous effort to make the world a better place, I am glad to be supporting people getting the most they can with their EV cars. We need more EV cars for a better environment. I have designed a diffuser to get more miles with the Fiat 500e. The more miles EV cars will do, the less ICE (internal combustion engine) cars will do, the better the world will be. This picture is from my 500e. I've put more than 8000 miles on this prototype and counting, really robust design, maintenance free.

For those who wonders, I have been recording the performance of my Fiat with and without the diffuser installed for the last 6 months. I constantly repeat the same 15 miles commute day after day, which includes about 2/3 of freeway, or 10 miles. When leaving in the morning, the battery is always at 100%. I have also adjusted the tire pressure to be at the same level day after day. I always put the cruise control at 65mph or 70mph on the freeway, so that all measurements can be compared together. However, there are external factors that I cannot control, such as external temperature, rain, humidity, etc., which can significantly influence the energy usage of the car. I have discarded the data collected on rainy days when the road is wet as the effect of water on the road can't be reliably assessed, and for the other days when it's dry, which we get a lot here in Socal, I have plotted the data as a function of external temperature.

After collecting the data over a period of 6 months, I have noticed an upward trend of 0.223 mile per kwh at 65mph freeway speed with the diffuser installed, or just about a 5.1% increase, and 6.4% increase at 70mph.

Let me know what you think!

Thanks for sharing!

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Old 09-13-2019, 11:23 AM   #2 (permalink)
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Apologies, FiatDiffuser....

For some reason something in your above post caused it to be flagged and put in the moderation queue. I just saw it today (usually the queue is just full of spam).

Thanks for posting your experiment - better late than never?
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has launched a forum for the efficient new Mitsubishi Mirage
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Old 09-14-2019, 06:22 AM   #3 (permalink)
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Thanks for that FiatDiffuser! The picture didn't come through on my computer, but the diffuser sounds like a winner. It's good to see someone measuring the effects of modifications. A 5 to 6% increase in efficiency is great!
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Old 09-14-2019, 12:29 PM   #4 (permalink)
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somewhere we've got a dedicated thread on diffusers and belly-pans.
Seems like Carr's research reported that adding a complete bellypan with diffuser would cut drag 7%.If that's correct,then,historically,it would be hard to see more than around 3.5% delta-mpg for the entire underside of the car.We'd need to verify that.My memory is not to be trusted.
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Old 10-16-2019, 12:51 AM   #5 (permalink)
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More updates on this, as i'm considering a variant of the Fiat 500 for my next car.
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Old 10-16-2019, 01:25 AM   #6 (permalink)
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Gone before the thread went live, maybe a Personal Message would get to a working email address.

FiatDiffuser might appreciate knowing.
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Old 10-16-2019, 10:01 AM   #7 (permalink)
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Same post in another forum, but where the image appears intact.


More than one image in the link.

The minor gap that you see was corrected with the new production template we're now using to built the diffuser panels, so the last few batches of diffuser panels that were built are now flush all the way with the bumper. I need to update the pictures, and will post some here too at the same time sometime this weekend.
There are also a couple of Facebook links at the bottom of page one.

From my perspective, I'm disappointed to see Vortex Generators in lieu of rake fence fins used on racing cars and the like.

However, it does seem to follow a very shallow plane angle, so it probably does not need either.

The hex head connections in lieu of something more flush face and less projecting is also a disappointment.

All in all, it looks clean (w/reservations) and promising - I like it in general. Needs some detail development.

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Last edited by kach22i; 10-16-2019 at 10:12 AM..
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