[clett]

Has anyone considered this before? Audi were able to change the aerodynamic coefficient of the A2 from 0.28 for the standard model to 0.25 for the 3L by making some subtle bodywork alterations.

One of these was closing the gap a fair bit at the front grille for engine air intake. They could do this because the engine in the 3L was rated at lower power. Some cheap bits of plastic blanked off half the grille leading to considerably improved aerodynamics.

So how about this for a cheap/easy mod to improve highway mpgs for the Insight?

Run two bicycle brake cables through from the dashboard to the front of the vehicle. Pulling on one closes off the aperture for engine air intake in front of the radiator. Pulling the other one opens it up. This mode could be called ‘Manual Aerodynamic Enhancement’ (MAE)?

If things get too hot, then just open it up (most of the time I think Insight would be fine with half the flow-through air for cooling – it has been designed to work in the desert etc after all). If everything OK and driving at speed, close it up a bit. In future, the opening / closing could be made automatic with a simple engine coolant thermostat (‘Automatic Aerodynamic Enhancement’, AAE?).

Could be a fairly cheap/easy mod! Would be interesting to see if it improves mpgs at highway speeds.

 

[Calpod]

I have a cover that fits over the Bra, and it covers the lower portion of the grill, it takes about 20 seconds to put it in and about 2 seconds to pull it out, I use it in the morning, and when it's cool on the way home I just uncover 1/4 and drive it back like that, if it's over 80 degrees I take it off.

 

[b1shmu63]

I would LOVE to do something like this. Without a way to test the result it would be difficult to know if there is any improvement. The front wheel wells are specifically designed to allow egress of the engine compartment airflow. cutting slots in the hood might acomplish more??? Both IMAS and the new Lotus Exige use this idea. Just thinking out loud.

 

[Dougie]

I'm interested to hear about the cooling air exiting through the wheel wells. Do you think that is why the holes for the steering rods are so big? If this is the case, then the under-engine panel could be redesigned to be much smoother and to cover a bigger area...

 

[Mike Dabrowski 2000]

I would imagine that simply blocking or leaving the air inlet open would not matter much unless the block was pointed and blended into the frontal shape to redirect the air, rather than just presenting a flat blocked hole? A wall with a radiator, or a block, still is a wall.
Interesting idea. What about the camback vs complete teardrop as the solar cars have, or is that just to tuck in more solar cells?

 

[trunkout]

what!?!?!?

lowest drag co in any production vehicle???

I will leave the aero to those japanese scientists.....

 

[Guillermo]

I would not change the front end, they spend a lot of money in wind tunnel testing. But they must have compromised with the side mirrors, so removing those and replacing them with mini CCD cameras located inside the side windows and dash mounted LCD screens would improve aerodynamics for sure. The only other things worth trying is smoothing out the underbody air flow, removing the radio antenna, waxing the car and putting thin clear packing tape on all body panel gaps.

 

[Dougie]

Actually, waxing doesn't help: The boundary layer is so thick that it doesn't matter. There's no attempt made by the designers at maintaining laminar flow, so you can let your car get dirty and it won't change anything.

Unlike solar cars.

 

[flunkysama]

I played around with the idea of the closing the upper radiator opening for winter driving. Since the cover will be sloped, it'll be more aero than a flat cover for the lower grill. Although the hood release could be a problem.

Or you could weld some AL tubing to the bottom of the hood, weld some fins to the top the top and you'll have a radi-hood-ator. :lol: Then you can close off entire front of the car. (except for when you want AC.)

 

[b1shmu63]

Other than making a burn your fingers hot hood, that would probably work just fine. :lol: Race cars have used this idea for body panels. Forget the fins though! :shock:

 

[Double-Trinity]

I would not change the front end, they spend a lot of money in wind tunnel testing. But they must have compromised with the side mirrors, so removing those and replacing them with mini CCD cameras located inside the side windows and dash mounted LCD screens would improve aerodynamics for sure. The only other things worth trying is smoothing out the underbody air flow, removing the radio antenna, waxing the car and putting thin clear packing tape on all body panel gaps.

Well, the idea though of having a variable width radiator opening could definitely show results, but there is no cheap way for Honda to have made a feature like this "idiot proof". It would have to have some sort of temperature feedback to determine if more cooling is needed, then servomotors would be needed to actuate the opening. If it were to get jammed and overheat the engine, it's also something they would need to cover under warranty, as well. Even a partial block however should help in most climates -- radiators are typically designed with excess capacity for worst case scenarios, like climbing up a long hill in the hot desert.

I would imagine that simply blocking or leaving the air inlet open would not matter much unless the block was pointed and blended into the frontal shape to redirect the air, rather than just presenting a flat blocked hole? A wall with a radiator, or a block, still is a wall.

Even a flat wall is still going to be much more aerodynamic than a grill opening, a radiator with multiple sets of fins, and other objects for the air to bump into/generate turbulance against.

What about the camback vs complete teardrop as the solar cars have, or is that just to tuck in more solar cells?

It has always seemed to be that extending the streamlining to a "point" like that would only help if there is no crosswind whatsoever. Imagine however a crosswind at 90 degrees to the car, by extending the back significantly longer to gain a slight drag reduction, you've just increased the total lateral surface area, which would generate a greater resistance in the case of the crosswind. There may also be more unwanted lift at high speeds, solar cars don't go very fast, but an insight might have problems at highway speed.

Another idea I have seen on some extreme concept cars is to have a skirt to cover the front wheels, that is spring loaded and "pushed" out of the way to make room for the wheels to turn. I'm sure this would be a problem however on the insight, as the wheel well is where the engine vents its cooling air.

 

[Dougie]

Are you sure the openings from the wheel well to the engine compartment are to vent the cooling air? Another reason might be to relieve the high pressure area in the wheel well. I have been meaning to mount a camera in there and take a picture of a tuft...

 

[b1shmu63]

Note that the leading edge of the front wheel well is further out than the trailing edge and that the trailing edge has a slight radius to smooth the airflow. One way to verify this would be with a sensitive air pressure meter using a small diameter hose run through the firewall into the cabin of the Insight.

 

[clett]

Regarding the question of how much difference to Cd closing up the radiator would make, I just thought about another couple of vehicles that did similar things.

GMs EV1 electric car obviously had no need for a big opening at the front, so managed a great Cd of 0.19.

Also, during the US Partnership for a New Generation of Vehicles (PNGV), Ford, GM et al were trying their best to come up with fuel efficient designs for ICE powered vehicles.

GM engineers realised that to reach the PNGV targets for their 80 mpg Precept hybrid, they had to improve the aerodynamic coefficient dramatically. To do this, they moved the engine to the rear of the car, and closed up the front radiator grille completely. The engine then received cooling via air intakes at the rear.

The result was a Cd of 0.163, about half that of a normal vehicle. If Insight could also manage 0.163, that would reduce the power (and fuel) required to overcome air resistance by about 35%. Only one way to find out!

 

[ecoangel]

Drag is made ip of a number of factors:

frontal area

skin/surface friction

shape

and where wings are concerned lift/downforce induced/trailing vortex drag


The A2 1.2 TDI has the same 0.25 Cd as the Insight but is a much taller vehicle with a large interior capable of comfortably seating 4 tall adults and significant luggage. I choose it over the A3 and Seat hatchbacks because i could get my guitar amp (Trace Elliot Speed Twin 2x12) in the back and take 4 adults as well. In fact the rear seats can be removed (fold up like breifcases) and then you can fit a dishwasher or spin dryer in there!

Compared to the 1.4TDi and 1.4/1.6 Petrol engined A2s it has the vents closed off but more than that it has better underside profiling and narrower wheel arch extensions plus a longer and thinner rear spoiler. In addition the wheels are 14 inch 4.5J fitted with low rolling resistance (a la Insight) Bridgestones - this time B381 145/80 R14s - so narrower tyres have an impact on frontal area as well.

You could try narrower tyres, a longer rear spoiler, smaller (F1 style) wing mirrors and maybe the variable blacking idea to reduce Cd further.

I still think smooth is better than rough - so polish the front of the car at least!

 

[b1shmu63]

Clett, I do tink that you are onto something there. I don't believe that you have to move the engine to the rear to get a good approximation of the effect. Just route the radiator hoses to the back and modify the rear inner bumper to function as a radiator. Add some ribs to the bumper by welding or find a really long aluminum extrusion for cooling power transistors and bolt it on. Use silicon compound to make a good contact. Weld the ends of the bumper shut with adapters to attach the hoses to. Cut openings in the rear plastic bumper to allow airflow and fit nice louvered grills. (Actually if the fins on the inner bumper are anodized and attractive enough they might serve as decorative grills by themselves). The only remaining challenge is to route the coolant from the front of the Insight to the back. The best solution would probably be to use large diameter stainless steel rigid tubing. Again flexible hoses from the engine would have to be securely fastened to the stainless tubes.

Why doesn’t Honda do this? Well, there is the cost. Standard radiators are obviously cheaper. There is the difficulty of servicing , and there is the possibility of leakage, perhaps from hitting a rock. There is also the necessity of moving air over the radiator while stuck in traffic. Custom small diameter fans would have to be fitted to the rear radiator.

There is also the issue of air conditioning. Now we are into high pressure Freon filled hoses running the length of the car!

If I had a second Insight, (perhaps a salvage title) and some spare time I’d love to try this out.

A final touch would be to rework the front bumper into a real boat prow shape.

In my opinion all of this would only be really effective if the air turbulence under the Insight was addressed by improving the aero panels down there.

 

[Dougie]

Moving the radiator to the back would be interesting, because then you could try to maintain laminar flow over the front of the car. Although it would probably be virtually impossible in reality. Solar car people keep stickers off the front of their cars because the edge of the sticker can trip the flow out of laminar...

Using the surface of the car as a radiator would make it heavy, and I'm not so sure there's enough area...

 

[b1shmu63]

Laminar flow? We definately would have to do something about those windshield wipers. But I digress.

Aluminum is typically used in electronics for heat sinks. (Copper although slightly better at conducing heat is very heavy.)

The rear bumper. The real one, not the plastic cover, is a rather stout aluminum extrusion with a square cross section. The flat surface of the extrusion would make a good contact area for a supplementary finned aluminum extrusion. Tying these aluminum pieces together would make the rear bumper even more robust. Cutting vent openings in the rear bumper would make the Insight more aerodynamic because it would allow air to flow into the area of low pressure behind the car. If it was done artistically it should look quite cool, just as the louvers on the front are both functional and aesthetically pleasing.

I feel a photoshop project coming on.