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Old 07-13-2011, 05:51 PM   #11 (permalink)
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Quote:
Originally Posted by bteck View Post
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There's a few threads on boat-tail construction, and for what I can tell, they all support the idea of an upswept boattail between 4-7 degrees as a preference, while until about 15 degrees in upsweep there is serious Cd increase. If you were conscious about the length of the boat tail, I'd say push 7 degrees in upsweep.

Also, with a small car like yours it might be wisest to focus on weight. Reductions in weight on your car will go farther than deletions on a truck. I had initially suggested conduit for the build because not only is it forgiving, but lightweight. You'd might be interested in switching from steel rims on your car, and increasing air pressure in your tires, also.

I appreciate your ambition, nonetheless. Good luck and happy modding!

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Old 07-13-2011, 05:55 PM   #12 (permalink)
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i eas thinking of refacing mot of the car with a fiberglass body and removing the stock steel body panels because it might do both for me eco. any thoughts on this for a horozontal profile?
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Old 07-13-2011, 06:33 PM   #13 (permalink)
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more going on

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Originally Posted by bteck View Post
so my car is similar size to aerocivic when it started, so why would i not see similar mileage as basjoos gets? just curious if there is more going on with his car than he states on his website?
--Either way, I'm planning on going a bit insane with this car, as I didn't spend much on the car and it is already ugly as sin, so i'm thinking at least I might get some efficiency gains out of it.
also, aerocivic has quite an upsweep on his boat tail, is this ideal? wouldn't it be better to "return the flow" to the level it was at before it was forced over the car? such as on the schor?
I think AeroCivic has a little better Cd going into the mods,and I believe it also has a smaller frontal area.AeroCivic also has the V-tec engine I believe and Mike has been very careful about his choice in tires.Friends had the Honda Civic V-tec and were seeing real world 55-mpg with a bone stock car.So maybe there is a powertrain advantage.
I haven't a clue about gearing but you can bet that it's been highly scrutinized.
The OBD-II tech that he has also allows him real-time data acquisition with respect to lean-burn and he can really optimize his driving for mpgs.
With other than aero mods you most certainly could push beyond the mid-sixties mpg.
I won't be able to tell you anything about the trailer yet as it remains an unknown quantity.Encouraging results so far.
As far as the diffuser angle,it was modeled after an aircraft he's fond of.The steeper angle no doubt protects it from ground-strikes with steep driveways and such,and with the length and top/side camber of the boat-tail the car is realizing really great pressure recovery.
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Old 07-13-2011, 07:11 PM   #14 (permalink)
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That nmakes sense, V-tec is scary cool. I was considering some other potential mods, however my lack of car-specific knowledge makes it difficult for me to assume i would be able to do much to the engine. as far as base line mileage I can get about fifty, driving hyper mile status, but not as good as the magestic V tec. I might do some tire pressure testing, I've only had the car for about a week, which means my absolute baseline is not as good as it could be. I'm really curious about the boat tail angles, i just got a high CFM fan for a mini wind tunnel I want to build, that should help me know what shape might be best. Also just a question, but would weight staging the car only increase mileage in acceleration situations correct? It should have almost no affect on highway, or am I mistaken?
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Old 07-14-2011, 05:02 PM   #15 (permalink)
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Aspire

Quote:
Originally Posted by bteck View Post
That nmakes sense, V-tec is scary cool. I was considering some other potential mods, however my lack of car-specific knowledge makes it difficult for me to assume i would be able to do much to the engine. as far as base line mileage I can get about fifty, driving hyper mile status, but not as good as the magestic V tec. I might do some tire pressure testing, I've only had the car for about a week, which means my absolute baseline is not as good as it could be. I'm really curious about the boat tail angles, i just got a high CFM fan for a mini wind tunnel I want to build, that should help me know what shape might be best. Also just a question, but would weight staging the car only increase mileage in acceleration situations correct? It should have almost no affect on highway, or am I mistaken?
If you'll leave the powertrain alone during the aero mods you won't upset your baseline,and any change to your mpg will have to have come from the streamlining.
You'll also be able to know your new Cd at any point based on your mpg at a given constant speed.
As far as the boat tail 'angles' are concerned,that's been worked out with the 'Aerodynamic Streamlining Template'.If you'll use it with the Aspire it will show you proper curvature for attached flow as far as you dare to go.
You can use it for the sides as well after locating the point of maximum body camber along the sides of the car.It will be the same curvature as for the roof,only it will probably begin in a different location.Don't know where it is on your car.
The thing about the 'Template' is that if you will stay 'on the curve',at a later date,if you want to add more savings,you just extend the curvature from where you left off.
With a very light 1-wheel trailer you could have the entire tail and around Cd 0.12 if you'll fair in all the wheels.
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You'll have to help me out with 'weight staging',it's a term I'm not familiar with.
Weight is kind of a non-issue in purely constant-speed highway travel.I pushed my CRX up to 3,300-pounds ( Ford Taurus ) and still managed 50 mpg.Only a 2-mpg loss from the sub-1,900 lb original weight.
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Minimizing stops will have the greatest affect on your urban driving.My truck will get 39 mpg at a constant 45 mph.But with traffic,and traffic lights it drops to low 20s.Yes,there is a perpetual supply of oil buried beneath every un-synchronized traffic signal.
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Old 07-16-2011, 02:17 PM   #16 (permalink)
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Here's a thread to get you started: AM's '96 Aspire Mod Thread
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Old 07-22-2011, 11:22 AM   #17 (permalink)
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hey all,
quick update on the aspire. I have been working on getting a few things fixed in order to make it registerable. it needs a headlight fix, some new relays (common issue if any of you have aspire/festivas). meanwhile i am trying to get a good baseline mileage. I drove my first tank of gas like a jerk (trying to drive exactly as inefficient traffic does). This yeilded the following results:
297.2 miles
7.4 gallons
40.16 MPG (pretty good for trying to not hyper mile at all)
I am currently testing a tank of gas with tire pressure up (at 44, tires rated at 44) and hypermiling all the way.

The reason for this test, is with the van, I started hypermiling as I did the aero mods, and I think I may have falsely attributed some fuel savings to the aero mods. in the effort of being as scientific as possible I am trying to get some good base idea of what kind of mileage this car is really capable of.

After this tank i'll be doing the following mods this weekend:
smooth wheels
air dam
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Old 07-22-2011, 02:24 PM   #18 (permalink)
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You still don't have enough baseline for meaningful results of mod tests.
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Old 07-27-2011, 01:04 PM   #19 (permalink)
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Today I purchased 2 4'x8' sheets of HDPE for starting some front end aero mods. Should arrive in about five days. has anyone had experience with this material?

Also, it is really hot in utah, around 100 degrees, and the aspire, as nice as it is, does not come with A/C. Any ideas on how I can keep cool in my car without the aero cost of windows down driving?

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