Modding a Scion Xa
 

Long time lurker here and I'm finally ready to get off my butt and start modding. I hope that starting a thread will help motivate me to continue completing mods and provide some feedback. I have read Neil's thread and plan on incorporating many of his mods to my Scion. The mods will mostly be aero but will include larger tires (probably next year) and maybe a power steering delete.

I deleted my mud flaps and added a ScanGuage a year and a half ago when I got my car.

Mods Completed:
- Upper Grill Block

Looking forward to it! I've been considering replacing my truck with a more eco (and wallet) friendly vehicle, and the Xa is on my shortlist.

Grill Blocks
 

This weekend I worked on a grill block. The pipe insulation has been in place for a few weeks.

The small area of the upper grill that was not yet blocked
http://i15.photobucket.com/albums/a3...k/DSCN1892.jpg

Complete upper grill block with partial lower block and fog light cover. I did only one fog light cover to see how it looked. I'm not 100% sure if I will keep the fog light covers or not. I will probably add an identical lower block to the other side so 2/3 of the lower grill will be blocked. The lower grill block is choroplast connected with zip ties.
http://i15.photobucket.com/albums/a3.../DSCN18990.jpg

Yeah I know the feeling. I have a Jeep Cherokee that gets about 12mpg on my short commute. The Scion Xa is a pretty decent little car. The mileage is pretty good and I live in a mountainous area that is normally fairly windy.

Smooth and flat wheel covers are quite helpful. You can also seal the hood gap with some soft foam gasket that has the adhesive on it.

Do you have the auto or the manual shift? Are you coasting in neutral and/or downshifting to slow down? If you put the front defroster on at all, you get A/C which kills the FE. I just unplug the fuse; but now the coolant has leaked out after a couple of years without any use.

I have sealed the hood gap already. I noticed the defrost increase gallons per hour by almost .10 gallons at idle. So you unplug the fuse to be able to still use the front defrost but without using ac? I wonder if that was done to keep the ac in good working order.

I have the auto so I am limited in terms of hypermiling. I typically will downshift to slow down if its a long enough distance. My techniques could use some improvement as you can see from my average.

Thanks for the comment.

The A/C is used in warmer temperatures to dry out the air before it gets blown on the inside of your wind screen so it will be able to dry off the fog the has formed on it. I was always under the impression that the car knows the outside temp and below 35°F or so it would disable the A/C so only warm air would blow. Air at < 40°F does not have much moisture to begin with, so simply heating it will make a low humidity wind to clear condensation off your window. It's that 30-45°F temperature and high relative humidity that it all kinda goes haywire for me, too cold to need A/C but until the engine warms, it's all you got.

So in short, the A/C aids the deFOG function of your "defroster" at 40-70°F, isn't worth a darn to actually defrost....as your intuition probably told you. I've been contemplating pulling my A/C fuse in the cooler temps since I think they're too conservative in where they have the temperature cut off for that.

I just unplug the A/C fuse and run the windshield defroster without it. Yes, it takes a bit longer to clear moisture in certain situations - but that is what towels are for. There are at least three situations that I see fairly often when A/C definitely hurts the defroster working well: when there is a frost on the outside of the glass and I have not scraped it well, when it is raining and the air temp is close to the dew point (I have had droplets condensing on the inside of the glass) and most critically in an freezing rain storm - you need full heat to stay ahead of the ice forming on the outside.

As I mentioned, you probably should plug the fuse back in at least once or twice during the winter and run the defroster, if you want to avoid losing the refrigerant.

The controls in the xA do not modify the A/C at all in the defrost mode - it should shut off the A/C after a minute or so; and/or it should be manually toggled off (or on). The A/C light should come on when you are in defrost, but it does not; and if it did you should be able to push the A/C switch to toggle it off or on.

Sam, you should be able to coast in neutral (when you want to carry momentum) and get 200-350MPG depending on speed.

Neil I have used neutral coasting a fair amount but have stopped recently due to concerns of hurting the transmission. I might have to try taking the fuse out since we live in a cold climate.

I should also mention that my wife is driving the car most of the time. She will have a 75 mile per day commute for the next three weeks which will be about 65 miles of highway.

I went ahead and put the other side of the lower grill block in and covered the other fog light whole. My wife's first commute was about 33 mpg at 65-70 mph.

http://i15.photobucket.com/albums/a3...k/IMG_5697.jpg

If your car can be flat-towed, then it can coast in neutral.

Have you blocked the "chin" vent area so all the air goes through the radiator?

Actually any car can coast in neutral as long as the engine is running. You should only engine off coast in an automatic if your car is also rated to be flat towed. Although it's mostly not worth the hassle in an automatic car anyway and it adds a lot off wear and tear to your starter since you can't just pop a clutch to restart the engine.

I neutral coasted in the jeep today and it seemed to help a bit. I have not closed the "chin" vent area. I assume you mean the space above the lower grill opening? I tried searching your thread but had no luck.

I want to get a replacement vehicle for the jeep am looking for a vehicle with a manual transmission. We will see if I have any luck.

With the oversized stock grill openings, much of the air is allowed to flow out below the lower spoiler under the front bumper. If you block those off, then all the air that comes in through the (reduced) grill opening goes through the radiator.

Thanks for clarifying that Neil. One and a half hours later I blocked the chin area. I was surprised at the large area there; it was almost 4 inches lower then the radiator!

I think I will move onto a belly pan when I get some coroplast. Hope to do this next week!

Mike

Here is a picture of the chin area blocked off. The far left shows the amount of space covered up.

http://i15.photobucket.com/albums/a3...k/IMG_5700.jpg

My wife was excited to tell me she drove 60 to work and back (75 miles) and she followed a semi on part of the way home. =)

http://i15.photobucket.com/albums/a3...e254674b82.jpg

That is awesome! My girlfriend just looks at me funny when I exclaim to her my achievements. lol. In her defense she does drive an echo, so the numbers I am achieving are her norms. haha

nbleak21, Thanks for the reply. I thought I already responded to this a while ago. She thinks I am a little crazy at times but tolerates it most the time.

I can't believe this thread is already over one month old. This car now has a 5 mile round trip commute for the near future but will see a number of weekend highway trips.

The grill blocks seem to have helped a bit although not a-b-a tested. I just pulled the fuse for the AC in the instrument panel thanks to Neil's suggestion and it has made a difference in the fuel consumption with defrost on. Thanks Neil!

Is there a way to determine the expected fuel economy effect of a kammback to the 30% mark of the template. I think just from the tail lights up and expect it to be about 17" in length total. Picture is from the streamlining template thread.

http://i15.photobucket.com/albums/a3...ps180d2f8c.jpg

30%
 

I don't have my case studies workbook with me,but if memory serves me,the Mercedes Benz Boxfish concept car,with about 28.5% 'Template' aft-body achieves Cd 0.19.
Of course there are a lot of reasons why the Boxfish achieves 0.19,but it's apparent that a car of 30% aft-body could 'go' into this arena.

Well temperatures have dropped here and its no fun working outside. Hopefully I can put something together soon. I have been kicking around the idea of a hitch mounted rack on the back with integrated kammback or an aerodynamic trailer. I have another couple hundred miles of highway in a few weeks so am hoping to finish something. The rear wheel arches are horrifying on this car!

I'm waiting on warmer weather too to start conjuring higher mpgs out of my XA. I have a round trip drive to work of three miles, max mph 25, and am averaging 23.7 one way mpg. My XA stays in open loop 2/3 of the trip. Recently I took a trip of 90 miles round and averaged 42.5 mpg. This was on mildly hilly two lane country blacktop with about 3 miles of town driving. Not too shabby considering I was burning winter grade E10 and the outside temp was around freezing. I never exceeded 52mph and drove with load, coasting on the downgrades. I know it could have been better but I was plagued with tailgaters that messed with the neutral coasting on downgrades. I have a manual trans XA and find the mpg sweet spot at 52mph @ 2250 rpm, usually in the mid 50 mpg range.

So far, the XA is stock with the addition of an Ultragauge and 40 psi in the tires. Possible mods include aero improvements -smooth the nose, drill the rear bumper cover (pure parachute!), air dams, outside mirror delete; mechanical mods - tank heater, battery tender, fuel pump relay toggle switch, warm air / cold air intake, alternator cut out and whatever else looks promising.

I'm looking forward to see what kind of improvements this thread bears.

MTXA, if you have a heated garage, or install a block/coolant heater, you can get that number up higher. I have 1.5mi of city travel prior to hitting the interstate, and have noticed quite a gain from the combination of parking the Acura in my garage (iat approx 65F) as well as the trickle charger overnight. Those two changes alone have brought me up from 17-19mpg to 23-25mpg during that 1.5 mile portion of the trip.

I like your list of proposed mods... I'd include a grill block, which has several possible benefits: slight aero, quicker warm ups, and helps aid in wai applications.

I am curious to the fuel pump relay mod... I've heard of people doing such as an anti-theft device, but have yet to come across reasons for FE... What is the reason behind this?

I am averaging about the same on my 2.5 mile commute. Have you consider a rear underbody panel instead of drilling the bumper?

To answer nbleak21: I garage the XA at home but I don't heat my garage. I'm looking at a 750 watt tank heater at the local Farm & Fleet coupled with a timer for my commute to work. I work second shift and pull the car into the shop a couple of hours before the end of my shift so it is warmed up (if I didn't I'd be almost home before I could defrost the windows).

Some good friends of mine run an automotive upholstery business and I'm going to see if they could sew up a full nose bra that has vents that I can open when the weather gets warmer. I'm also considering building grill shutters controlled with blend door stepper motors. I've been looking for a damaged grill to build it with.

The fuel pump cut out will be a normally closed switch that will control the ground circuit of relay so I can shut off fuel during coasting without shutting off the ignition. That will keep me from potentially locking the steering wheel by using the ignition switch and also keep my short trip data stream alive

Answering Sustainable Sam: I've put the XA up on the shop hoist a couple of times to do an engineering study on a belly pan. If I went that route, I would prefer to use sheet aluminum that has been louvered to dissipate heat. The sheet aluminum I can find easy enough but I don't know of anywhere local that has a louver press though I suppose I slice and peen it. Because most of my driving is non-highway, I'm considering just making an air dam and side skirts out of heavy duty landscaping edging and drilling the rear bumper cover with large holes to vent it. My XA spent its' first seven years in downtown Chicago where they park by feel, so the bumper covers are already pretty dinged up. Right now, I'm mainly seeing what others have done so I can pilfer their good ideas. I've been looking for a decent book on automotive aerodynamics but so far it is pretty slim pickins.

That is an excellent idea!

I have considered the louver idea as well, but ROI just wasn't worth it with the setup I wanted to do.

I would consider a fuel injector cutoff over fuel pump, unless they are on the same circuit.

Cutting the fuel pump alone would cause all the residual pressure to still be released during injector firing, this can cause overly lean firing, fuel pooling, air in the fuel system, etc... Furthermore, for correct operation upon reignition (via bump starting or clutch) the fuel system needs to be at proper PSI, meaning after fuel pump shutoff, the pump will have to re-prime the system, causing the same problems describe above, except under load, which is definitely not good.

Shutting off the fuel pump should result in only a second or two of lean running before the engine stalls. The system should re-pressurize in a second or so when the relay is grounded again. The biggest problem that I would be concerned with is on the restart the 02s would likely command rich so the savings may not be worth it. I could also open the grounds in the injector circuit to maintain fuel pressure but I would be concerned about spiking the ECM from the field collapse.

Go with the air dam and side skirts. The rear bumper actually holds in a high-pressure bubble of air that provides a "phantom" belly pan against the surrounding low-pressure air moving past the car. It's much like the benefits of keeping the tailgate up on a pickup truck.

Drilling out the bumper invites all that low-pressure air to go swirl around the bumper area and creates extra drag. If you're worried about that area, design a partial belly pan that starts at the rear axle and goes back from there (level to the ground for a hatch/wagon profile).

This is the ecomodder's aerodynamics Bible. Aerodynamics of Road Vehicles - SAE BOOKSTORE Whenever someone mentions "Hucho", they're referencing this book.

I don't think the xa would benefit much from an airdam, the front already extends to the lowest point of the car. I picked up two sheets of coroplast today. I think it will be wheel covers and wheel skirts to start and then I will work on reducing the wake with a kammback.

I made a little progress with some wheel covers.

Before:
http://i15.photobucket.com/albums/a3...pse279dbd6.jpg

After:
http://i15.photobucket.com/albums/a3...ps45f9db69.jpg

Overall I think they look pretty good and they are wife approved. I am not sure how many mounting points are needed. I accidentally poked holes for each spoke. I have had no luck finding the image with the effect of wheel covers on cd. Anyone have an idea? I still think the wheel arch gaps are awful on this car especially the back. This will be the next thing I tackle.

What do you guys think?

What do you guys think?

Here is a link to a thread with A-B-A testing of full wheel covers: http://ecomodder.com/forum/showthrea...-6-a-4368.html

I noticed the bumps on the rim between the spokes. They look like an excellent attachment point for the covers if you drill & tap them for screws. It would look a little more hot roddy too.

The rear wheel arches on the XA are going to be difficult to close up. After giving the arches on my XA the scrutinizing squint, I'm inclined to make the rear skirts over a stressed skeleton frame made from light gauge aluminum flat stock. That is the only way I can see to fill the whole arch due to the curvature.

I used an 1/8" steel rod inside the Coroplast channel to for the slight bow need to clear the wheel. Tabs with threaded holes would be the way to avoid the tape that I have been living with for years... They need to come off when the wheels get rotated, etc.

Partial front skirts help a lot as well.

Neil are your front and rear wheel skirts both just taped on? I might cut some front wheel covers this week and tape them on before I leave on my highway trip this weekend. Proper mounts will have to wait a while.