5th generation civic hatchback - improving aerodynamics

[steffen707]

There's also a big gain from having the throttle plate open further at a given speed, because it reduces pumping losses from the engine, I'm not sure how to explain that, but this thread has good info on it.
http://ecomodder.com/forum/showthrea...rence-529.html

[steffen707]

Originally Posted by AndrewJ

I used 2 sheets of 4'x8' 28 gauge galvanized sheet metal. I also ended up using 16-24' of 1"x1/8" steel bar stock for the skeleton.

With paint, caulk, rivets, plexi and lights I'd say it came in at about $150.

I still have a little sorting out to do with the rear taillights/turn-signals, but that shouldn't add more than another $20 to the tab.

Did you weigh all of the additions for the boattail?

[steffen707]

Originally Posted by AndrewJ

Driving back home last night and the damn back plexi blew out agiain. I'm afraid it's going to take a much more permanent method of fastening the next time. I'm thinking a box of pop-rivets ought to hold it on pretty well....

Try Dzus fasteners. Light weight, secure and can be undone relatively quickly to utilize the hatch.

[SiVX]

This thread and site in general are an amazing plethora of great information. I've read this section over quite a few times and have yet to comment. Andrew your work is amazing as well as the creativity. I'm impressed and would like to congratulate everyone here.
*To making a difference*

[GregM]

Originally Posted by steffen707

I wonder how quickly the battery will be depleated without the alternator, I also wonder how fast the alternator can charge the battery back up to full power.

My thought was that on a long road trip, you could disable the alternator for an hour, and then let it run for an hour.

Sure it wouldn't be as big of a gain as no alternator at all, but if what I read about increasing MPG by 10% with alternator delete is true, then perhaps 50% alternator use would gain 5%? Might be worth it without as much hassle as the deep cycle battery and having to charge the car up every night.

How about running a plunger switch to the gas pedal. When coasting (no throttle input) the alternator is allowed to generate. When cruising/acclerating, the alternator is disabled.

Combine this with an override switch for long highway cruising or idling in traffic...

ALTERNATOR SIGNAL WIRE
|
|
3 position switch (1 to pedal switch, one not connected, one grounded for Auto,GENERATE,OFF respectively)
|
|
THROTTLE SWITCH, nomally closed (aka shorted to ground when pedal is depressed)

Thoughts?

[some_other_dave]

I think that might be backwards? I think you would want to "pulse and glide" the alternator, like you would the air conditioning. The idea is that the extra load from the alternator (or AC) isn't much more than the load to accelerate the vehicle, but when you are coasting the extra load is much larger relative to the load to keep the motor running.

The problem with that is that you may not be on the gas hard enough for long enough for it to recharge your battery very much.

Plus there will always be some load or drag on the engine from the belt and pulley, no matter how you disable the alternator.

-soD

[GregM]

Probably makes sense.

I typically drive stoplight to stoplight in heavy traffic and my civic coasts almost too well, so I typically begin braking very early.

I'm mostly just bad at pulse and glide in the city (I still think I'm better than 95% of the the other idiots on the road). Maybe a 3rd switch to sense moderate-hard acceleration or braking?

Also, I believe at least one manufacture (Mazda) is doing something similar - disconnecting the alternator at cruise, and using the alt. to charge a capacitor when braking.
MAZDA:Regenerative Braking System | Environmental Technology

[dave.davis]

Originally Posted by steffen707

I copied your idea and i'm shocked at the in town results. I've gone from around 50-55mpg for accross town 4 mile trips under 35mph speeds with 4-5 traffic light, or stop sign stops, to now a record high of 69mpg for the same trip. Just to make sure I drove all the way back to Autozone and drove the same path home and got 67.93mpg so I know its not a fluke. I need to isolate the modification for testing because i also did a front grill duct tape block at the same time. I know 12-14mpg is a TON, so I want to be scientific about it and do an A-B-A kind of test to know how "true" these mods are. Also just driving a few tanks with and without the mods would help to compare, but when you get 500miles on a tank, one needs to drive a lot to test results.

What I have noticed though is that at 65mph I am still getting the same MPG that I was before these mods, between 45-52mpg highway. I think that not having a belly pan of any kind is filling the engine bay with cold air and causing the intake to suck more volume of air due to more throttle input. I was going to use a wind block on the right side of the exhaust/CAT to block wind from blowing right behind the CAT and into the pipe without flowing past the manifold to warm it up more.

I need to find something to test the incoming air temp with and without the WAI, and with and without the front grill block. It amazed me how fast the car heats up now too. That will pay off huge in winter (WHY DIDN'T I READ THIS LAST NOVEMBER!)

So what kind of car did you mod, Steffan?

Any reason this mod wouldn't help a 7th Gen (2002) VTEC Civic EX coupe?

[mikeyjd]

Originally Posted by AndrewJ

Ok, looks like I gotta re-hijack my thread for a little bit

With my recent relocation so stiflingly hot Missouri, and a subsequent lack of internet access, hence by absence here, I started a little project to keep me busy.

Step 1: Strip everything off the back of the car and throw it in a pile on the garage floor.





Step 2: Get a bunch of 1" x 1/8" steel bar-stock from your local hardware store. (Aluminum would be better, but when you're using 30' of the stuff that could get really pricey.) Once you've got your bar-stock, get all creative with it.











Step 3:
Proceed to get out the arc-welder and stick everything together with really crappy welds.











Step 4:
Get a little piece of plywood to stick on the end to hold the new taillights and license plate and such.









Now all I have left to do really is get the sheet-metal, attach it, and then figure out some way of putting on a bit of plexiglass.

Well, the boattails been done for over a week now, guess it's time to get some pics posted up of the finished product.

It's pretty amazing how much the boattail has helped with coastdown times. I'll look down at the speedo after a good 10-15 seconds of coasting on level ground and I *might* have dropped 5mph (from 65 to 60) on a bad day.

Mileage seems to have been improved at least 10%. I'm now able to consistently hit 55mpg burning 87 octane E10 gasoline. I'm positive that I'd be reliably in the 75mpg range with "real" gasoline.


















I scavenged the key mechanism out of the hatches "tailgate" and with a little copious modification it made a serviceable lock for the new rear window.

Pages 1-26 great read!

[forums123]

Really great photo documentation... I really appreciate all your sharing on this thread. I was wondering, how did you attach and form the sheet metal panels on your boat-tail? Do you experience alot more wind noise from the seams? or did you seal the joints with some kind of sealer?

Thanks
Dave