eNV200 aero mods

[vianney]

Hi !

I am new to this forum, a few words about me:
French engineer working in satellites industry near Toulouse.

Recently bought an EV, Nissan eNV200 Evalia (40kwh) to drive all the family (3child) in replacement of a (too small) Toyota Yaris hybrid.

Given the car might probably hit the bottom of the best aerodynamics ranking, I decided to go on with some aero mods, to test how far I could go (and possibly make some mods permanent so that we can go see grandparents at 110km/h instead of 90km/h (400km trip) !.


Up to now, I did:
- rear wheel cover
- rear undertray and diffuser
- side mirror profiled casing

and now about to test boat tail I just completed.


I have some pics and videos from tuft testing (for rear wheel cover and side mirro profiled casing - there is also a Citroen C4 of by brother in law that we tuft tested together to see what was going on on his car), I will find out how to provide them later.

Problem is that by my side there is always wind, and no long flat road, so it is quite hard to assess drag reduction below 5%. and also I don't have long commuting trip so averaged MPG on long distance is not possible.

I got the LeafSpy Pro app and with the LE Link2 adapter I am able to retrieve 5samples/seconds logs of drawn battery power (basically, battery HV volts * amps).
What I do is processing measured battery power and GPS speed data logged by LeafSpyPro with Scilab, and I compute the experimental SCx (CdA) by removing expected rolling resistance, slope effect, wind effect from measured battery power. This allow to get rid from cruise control not being always spot on targeted speed.

I hope I will be able to test boat tail tomorrow. Will do drag reduction assessement as well as tuft testing with a camera-on-stick approach.

Vianney

[vianney]

here are some pics of w/o undertray

and with undertray. purpose of the undertray was to avoid having the large transverse bar facing the flow, so the udnertray is composed of two parts, one kind of deflector in front, and the bottom diffuser.


my plan for this is to perfom tuft testing to check attached flow on the diffuser. (once i will have the boat tail attached to the end of the car this will be even more important!)

[vianney]

and a pic of the boat tail structure (which is fitted on the car by means of bike holder hooks)

[vianney]

I see members are allowed to post links when they have posted more than 12 posts, when this will be done I will put the tuft testing videos, showing the rear wheel cover works quite well, and the profiled side mirror casing also good (altough less than expected).

[freebeard]

Thanks for the pics. They prompt some questions.

Will you seal the edges of that waferboard, if not the surface. Newer product isn't as vulnerable to moisture, but the underbody is a harsh environment.

For an example, BamZipPow's Dark Aero He started with dimensional wood, but gradually replaced it all as it deteriorated.

Will the boat tail lift with the tailgate? Will it underlap the bumper to prevent a step abaft the diffuser?

[vianney]

Originally Posted by freebeard

Thanks for the pics. They prompt some questions.

Will you seal the edges of that waferboard, if not the surface. Newer product isn't as vulnerable to moisture, but the underbody is a harsh environment.

For an example, BamZipPow's Dark Aero. He started with dimensional wood, but gradually replaced it all as it deteriorated.

yes since I took the pic, the board has been covered with varnish both sides and edges. This is OSB3 so baseline water-resistant but yes I added some additional protection.

Originally Posted by freebeard

Will the boat tail lift with the tailgate? Will it underlap the bumper to prevent a step abaft the diffuser?

for prototype: first question, no and the second, yes: in that prototype the boat tail skin front edges needs to be taped to the car body every side. However in this version, since the boat tail joins with the outer car surface it masks the braking lights, which means for a production version I will need to add some repeater lights like in some mods presented in this website.
if I go for a production version, I think I will probably make it not overlap the lights and the bumper so that it is possible to open the tailgate yes, so there would be a step, at least at lights level. but maybe that step could be radiused anyway if the skin is rigid enough (I'm thinking of building the production version using the prototype as a mould and filling some thickness of expansive polyurethane foam inside the skin)

[JulianEdgar]

A few observations.

- The rear diffuser will work only if the floor ahead of it is also smooth. ie the airflow pattern ahead of the diffuser is critical.

- Measuring surface pressures will tell you at least as much as tufting.

- Trying to ascertain Cd accurately by road testing is, I think, impossible. Just go on changes to the total power (A * V), averaged over a long distance in two directions. Also, ensure that when you make a deliberate change to drag (eg by having the windows down), that change is clearly measurable. Otherwise, you may be measuring just noise.

[freebeard]

If you're productizing the result, that's 10x the effort; so good on you, here's hoping....

It's worth following Julian Edgar's advice. I think this is the best 'local' boat tail, I think it's on a different Insight now. Pic title says 'jims tail'.



Would your expected customers have a trailer light socket available? That would reduce rewiring effort.

[kach22i]

Honda Insight Tail Extension Project
https://ecomodder.com/forum/showthre...ect-13533.html


eNV200 aero mods
https://ecomodder.com/forum/showthre...ods-39423.html


Looks like a fun project, good luck.

[vianney]

Originally Posted by JulianEdgar

A few observations.

- The rear diffuser will work only if the floor ahead of it is also smooth. ie the airflow pattern ahead of the diffuser is critical.

- Measuring surface pressures will tell you at least as much as tufting.

- Trying to ascertain Cd accurately by road testing is, I think, impossible. Just go on changes to the total power (A * V), averaged over a long distance in two directions. Also, ensure that when you make a deliberate change to drag (eg by having the windows down), that change is clearly measurable. Otherwise, you may be measuring just noise.

yes actually the rear diffuser goes along with a plate in front of the low hanging transverse bar. the undertray is flat from front bumper to battery end (approx 2/3 of the vehicle length), so this latter plate fills the gap betwen the battery end to the transverse bar, and then the diffuser from that bar to rear bumper.

For the Cd yes I just want to have relative variations of the CdA, not the absolute value one. the thing is on short test tracks if I don't have perfectly the same speed (cruise control is not always spot on) it can very rapidly pollute results. thus this approach allows to get partly rid of this variations (altough I would prefer use relative wind speed instead of gps speed..)