Scion xA aero mods

[Daox]

That doesn't sound like a very friendly commute! But, it certainly sounds like you got it figured out.

[NeilBlanchard]

Hiya,

So far, driving without my rear underpan has gotten better FE! At almost halfway through the next tank, the SGII is sitting at almost 50mpg, which is the best FE that I have ever seen. This is up about 2-3mpg over the most recent tanks with the underpan.

I guess the lesson is, you do really need to worry about parachuting -- and by putting an underpan in the front of the car first, and work your way back; working to exclude air flow from getting on the "wrong" side of the mod...

[Deezler]

Thats funny, I think I am having the same exact problem.

I recently switched fuels to pure bio, which should drop the energy content and subsequently FE by around 6-10 %. Previous fuel switches haven't seen this much variation though. Well this time around I lost 4 mpg; not cool. The other day I leaned under the rear of the car to see that some of my double sided tape had let go on the rear belly pan and it could end up parachuting pretty badly at 70 mph. Just went out to the parking lot here at work and removed it, hopefully I'll get the same effect as you! I think a sturdy rear diffuser is in order now.

Awesome mileage there Neil.

[gargoyle865]

Hey Neil, great work with the Xa. I'm envious.

I was wondering if you've made any mechanical and/or electrical modifications. I'm planning to replace my (rather worn out) battery with deep-cycle ones, possibly a pair of Optima yellow or blue top (only difference is the blue has threaded studs in addition to the standard automotive ones). I'd relocate them to the spare tire well to allow 2 to fit, as well as to improve front/rear weight balance. My spare has been replaced by a tire-plug kit, a small air compressor, and my trusty AAA card for really bad blowouts.

I've picked up a couple of solid-state relays and plan to cut power to the alternator's winding unless the throttle is at idle or I flip a dashboard-mounted "just in case" switch. Then I'd top off the batteries with a smart charger at home.

Theoretically this would allow the alternator to free-wheel unless I'm coasting, decelerating, or stopped, in which case it would use this otherwise wasted energy to charge the batteries. Do you know of any cases where someone has done something similar?

[Xringer]

Originally Posted by gargoyle865

Hey Neil, great work with the Xa. I'm envious.

I was wondering if you've made any mechanical and/or electrical modifications. I'm planning to replace my (rather worn out) battery with deep-cycle ones, possibly a pair of Optima yellow or blue top (only difference is the blue has threaded studs in addition to the standard automotive ones). I'd relocate them to the spare tire well to allow 2 to fit, as well as to improve front/rear weight balance. My spare has been replaced by a tire-plug kit, a small air compressor, and my trusty AAA card for really bad blowouts.

I've picked up a couple of solid-state relays and plan to cut power to the alternator's winding unless the throttle is at idle or I flip a dashboard-mounted "just in case" switch. Then I'd top off the batteries with a smart charger at home.

Theoretically this would allow the alternator to free-wheel unless I'm coasting, decelerating, or stopped, in which case it would use this otherwise wasted energy to charge the batteries. Do you know of any cases where someone has done something similar?

So, you are going to use idle mode sensor to start charging..

Wouldn't that load on the Alt cause it to load up the ICE,
increasing the TPS to maintain idle RPMs??
And use more fuel than a normal idle?


Humm, back when I was thinking about add-on hybrid adapters,
I figured on hooking up something like a good-MPG vacuum switch
so when I was getting over 60 MPG going down a hill etc,
I would charge my pack. Bring that 60 MPG down some,
like maybe to 40 MPG.?.

The good-MPG switch would be ANDed with a low SOC signal
from the pack monitor. Once both were on, the charging would begin.


Based on the idea that it's best to charge when you have outrageously
good MPG, (or in Fuel-cut-off, using zero fuel) but don't
charge so heavily that you drop your MPG down
too much. I wanted it to work like a Hybrid regen system.
Charge up when coasting up to a redlight or going down a steep hill.


I guess you could test the idea by warming up the ICE and see what
turning on your lights (and high beams) does to your engine loading.
Might want to turn on the rear defroster too.
If your idle RPMs and/or TPS goes up, you'll know Alt loading effects your FE.

IIRC, I've given jumps to people and noticed my car start to change RPMs,
the second I hooked up to the dead battery..

[gargoyle865]

Originally Posted by Xringer

So, you are going to use idle mode sensor to start charging..

Wouldn't that load on the Alt cause it to load up the ICE,
increasing the TPS to maintain idle RPMs??
And use more fuel than a normal idle?

I was thinking about that too. Maybe I'll wire the "clutch disengaged when starting" idiot switch in series with the TPS signal to the relay. That way it would only charge when the throttle's at idle AND the clutch is engaged, aka fuel cutoff mode (or when idling in neutral, but one thing at a time). But I think that the reduced drag on the engine when the alt is freewheeling would more than offset the extra drain at idle . I suppose the first step is just to disconnect the alt winding wire and see how many dummy lights come on, and what happens to the RPMs.

Regardless, I'll stop here before I get in trouble for hijacking the thread...

[NeilBlanchard]

Update:

I had to reinstall my stock mirrors in order to get an inspection sticker...

But, the video mirrors are back on. They work better in every situation except bright sunshine: low light and in the rain, the video mirrors are far superior to the optical ones, and the field of view of the video mirrors is much better. I am leaving the small optical mirror on for the bright sunny days -- I get the best of both this way.

The other issue I had with the inspection was the age of my license plate: it is ~32 years old (it is the ONLY plate I have ever had on a car!), and has some cracking and is not as readable as it could be. I've seen far worse, though. If I take the state up on the offer to replace it with new plates with the same number -- I'll have to have a plate on the front of the car...which I don't like for aerodynamic reasons.

[SVOboy]

You could always take the opportunity to get some super sweet vanity plates...I'm planning on it soon!

[NeilBlanchard]

Hi,

Well, yesterday I found a fairly major flaw with my video mirrors: the LCD screens go black when they get too hot! This happened to the left hand one, which is exposed to more direct sunlight. This is probably part of the reason why they get darker in bright sunshine -- again the one on the left is often darker and harder to see than the screen on the right.

I may try to rig up a quiet 120mm fan behind them to try yo keep them cooler. Or, if it gets really hot (today is supposed to be hotter than yesterday) then I may be forced to turn on the A/C and that will test my theory...

Bummer. The screens do generate some heat on their own. After it sat in the shade for a while, the screen started working again.

[elhigh]

Originally Posted by NeilBlanchard

Hi,

Well, yesterday I found a fairly major flaw with my video mirrors: the LCD screens go black when they get too hot!
Bummer. The screens do generate some heat on their own. After it sat in the shade for a while, the screen started working again.

I had that happen with my multimeter while diagnosing a bum rooftop AC unit a couple of weeks ago. No problem, just dangle it under the output of this kitchen ventilator - that flow is air conditioned!

The fan ought to do the job, but geez - you have room?