26.2 mpg Toyota Previa. Go Golden Egg!
 

Just got a record mpg run to Seattle and back with some city driving as well. Was doing average 70mph on the highway as well.

Mods so far:

1) No alternator, running on 2 deep cycle batteries.
2) Electric cooling fan
3) All accessory belts off (no p/s, a/c, fan, alt.)
4) All passenger seats out.

That's it.

Driving habits:

1) Coasting when possible.
2) Drafting at a safe distance
3) Side mirrors in.
4) Windshield wipers vertical when possible.

Lots more mods to come.

I use this van for business. I need a van to move my furniture and supplies.
My alternate transports are the electric motorcycles.

Added: EPA is 20mpg highway giving me 31% over EPA so far.

That's pretty solid. Just wondering... this no-alternator business has me a little skeptical... spark plugs are supposed to work with a 14v feed and you're only giving them 12... do you think maybe if you drop the alt you should re-gap your plugs? I would think the spark is much cooler and it should be adjusted.

Yeah, That's probably right. The spark may be cooler. I have not been able to find out how much difference it makes but my ultimate plan is to have 2 8v deep cycle golf cart batteries in series for 16v (cars are designed to be able to handle a wide voltage range)

The alternator disconnect savings is real though.

"Even more to the point, the U.S. Corporate Average Fleet Efficiency (CAFE) standard prescribes a maximum fuel consumption rate for cars sold in the United States. The Federal government assesses a penalty of US $5 for every 0.1 mile per gallon (0.04 kilometer per liter) below 27.5 mi/gal (8.55 L/100 km) on every car the manufacturer sells. A 200-W electrical load accounts for about 0.4 km/L in the FTP 75 cycle test; so, if a manufacturer is delivering 25-mi/gal (9.41 L/100 km) cars, for example, it can justify spending more per vehicle on components to improve electrical efficiency."

IEEE Spectrum: Automotive Electrical Systems Circa 2005

I could also install a higher voltage aftermarket coil which would take care of the problem right there.

Congratulations! You might need that radiator fan though, eh? Why not convert to electric?

I already got rid of the old clutched fan and installed an electric fan from an 88 Sable V6. It's overkill though. I need to find a speed control or a temperature switch or both. I was hoping to track them down in the sable parts car but no luck so far.

Your Previa mods are awesome to read about. What kind of range do you get with running your electrical off the deep cycle batteries?

I've been thinking of doing a straight EV conversion on my Previa, but removing all the accessories that depend on the SAD shaft seems like an obvious first step. I'm thinking about trying part of what you did and seeing how things work out by just disconnecting the accessories.

Do you still have the SAD shaft connected to the engine or have you been able to remove that too since you're not powering anything off of it?

From my doorstep to downtown Seattle one way is 212km or 132 miles according to google maps. This included about 45 minutes at the border with about 20 starts to avoid idling and some use of the electric fan. when I got there the batts were at about 60% depth of discharge. 50% is about as low as I can go with these batts. Lower shortens the life too much. I guess you could go quite a bit farther with new batts, more batts, or true deep cycle batts like trojans.

I'm itching to take the SAD beast out with all it's cast iron. There must be a couple hundred lbs there. Good bye inertial mass, hello Ferrarevia!

It already revs up quicker now.

It's relatively easy to pop off the belts to try it. Make sure your tires are fully pumped as well as your arms for any parallel parking. Steering is a little harder so be ready.

I'm also hoping to do a conversion or hybrid on mine. This is a stop gap measure in the mean time. Until the right batteries are cheap enough or I win the lottery. The easiest would be an assist motor attached to the accessory drive shaft but of course a lot of losses there through the motor.

Have you heard of any other EV Previas? We are lighter than an S10, can take a bigger payload and are much more aero. There are hundreds of S10 EV's.

My wish list includes a set of LRR tires. Do you know what the OEM tires were? I bet they were LRR.

You should put a diesel engine into your previa.
eBay Motors: JDM Used Toyota Previa Turbo Diesel Engine w/Auto (item 190246359383 end time Aug-29-08 15:28:36 PDT)

132 miles sounds like plenty of range for experimenting with. The only times I usually need my van anymore is on short trips to Home Depot or to move furniture. Although I will be eventually wanting to add back electric A/C since I'm in AZ and that'll be another power drain.

I've got a couple old SAD assemblies that were taken off my van and was able to weigh one of them, and the SAD itself looks like it's only about 20 pounds. I don't know about all its mounting hardware though.

It does seem like this mod would be excellent even for just adding performance to the Previa.

No, You're the first other person I've found who's thinking about it. There don't seem to be a lot of minivan conversions in general. The best minivan conversion I've found online is this guy's Voyager, which he claims can do at least 90mph: Bob Gruenwald's 1987 Plymouth Voyager Speed's going to be important to me when I do my conversion because of all the 75mph speed limits around here.

I used to have another Previa too, and that one still had the original Toyo spare (I always had them check it when I got new tires, and it was still in good condition 15 years later). I'll have to check if my other does and see what type it is.

I can highly recommend switching the fan via the brake light circuit. Someone on a Volvo board recommended that for my e-fan project and I'm very happy with it. It's true there are still ways the coolant can heat up aside from braking events so you'll still need a temp switch or a manual control, but at least for my setup I'm keeping the brake switch circuit installed.

I added a time delay relay to the circuit so when I just tap the brakes the fan stays off. There's a delay again after I come off the brake - fan continues for about 10 sec. That saves a lot of on-off cycling of the fan motor.

You'd have to scope out your brake light circuit and see how you want to tie it in, but I think you can handle that.

The voltage depends on the inductance of the coil and the rate of change of the current, which should both be fixed and independent of the battery voltage up to a point, so I don't think using 12V instead of 14V would change the spark plugs that much since it only takes a few milliseconds for the battery to increase the magnetic field in the coil.

Thank you roflwaffle,

I've been wanting an answer to that coil voltage issue since I started this project.

Anyone who thinks that alternator loads don't affect FE should read this report by several big wig automotive electrical engineers. Lots of good info in it. IEEE Spectrum: Automotive Electrical Systems Circa 2005

Another reason to do this in my vehicle is the belt friction and rotational inertia of all those shafts, pulleys etc.

Thanks.

Np! If there are problems they would likely manifest themselves at higher speeds initially since there's only a half to a quarter of the time available for charging at 6k or 8k rpm compared to the usual ~2-3k rpm seen while cruising.

Is there an internet source with that info on coils? I get that "cooler spark at 12V" all the time an I would love to have something to educate myself as well.

This is pretty good. Since the voltage depends only on the inductance of the coil and the instantaneous rate of change in current, which is due to the speed of the distributor rotor and physical characteristics of the coil, so voltage doesn't seem to play a part provided there's enough to charge the coil. When charging, the energy stored depends only in the current and inductance, so the only problem would be if there wasn't enough time to charge the coil or voltage was so low (less than 9V according to the first link) that it wouldn't charge at all.

Since engines are designed to operate to two or three times the speed we usually drive at, we should see missing at high rpms is there is a problem with enough energy getting to the coil, but given the much longer charging times if your Previa still runs on 12V I think it's safe to say that there's enough voltage at 12V to charge the coil.

Hotter and cooler spark plugs are something that aren't needed unless we're talking about an engine operating outside it's designed range. For instance, changing the ignition coil can lead to higher voltages and a stronger spark so to speak if colder plugs are run in order to minimize issues w/ detonation at higher power outputs w/o having to deal w/ poor running from fouled tips at idle.

"Excellent (rubbing hands together) Smithers, release the hounds!"

29 mpg New Record again! The Golden Egg lays a good one!
 

I believe the correct term here would be... WOOT!

Not much compared to most of you micro car people but I'm dragging 3550 lbs around with a 2.4L four banger with 165,000 miles 266,000 km on it.

Just picked up salt flat discs (moon discs to the VW crowd) so the egg Is looking rather boss IIDSSM (If I do say so myself)

Thanks to everyone who has helped me with advice and encouragement here!

I think I can get 35 highway. I think I can...

Sable parts!
 

Awwa... Your using Bull parts:o Sean and I are pleased!
If you need help tracking down bull parts, just let me know.
Meanwhile, I'll be next door at the Taurus Club

O_O
[oval_overload]

Need recommendations for LRR tires for '93 Previa
 

Hello everyone,

Thank you for all the tips. Since I am not a mechanic, I can't do the disconnect the SAD suggestion, however I would like to optimize as much as possible, anything I can do to reduce my fuel consumption on a '93 Previa LE.
I've removed the middle captain's chairs (those seats were REALLY heavy) and one rear seat, so that there is only one seat in the back. Also, I am going to buy lighter wheels, but am wondering if anyone has a good recommendation for some good low rolling resistance tires? Also, what is the "air dam" you're talking about exactly, and grille block? Are there links you can direct me to?

Thanks to everyone for posting tips. Seems like the "highway" miles are where the mileage really improves, although I boosted my honda about 8-10mpg by putting LRR tires on it. That was a little car though, and they don't make that tire for a van.

Here is the link to my build thread. I'm still looking for LRR tires myself. Do you have the 14" steel rims or the 15" alloys? I think it's easier to find them for the 15" wheels. I've seen them on a Sienna but I can't remember the specs. I'll keep my eyes open though.

http://ecomodder.com/forum/showthrea...ding-5540.html

Thank you. I have the 15" alloys...was thinking about getting Rotas though, in flat black, they weigh 11lb each, just need to find the tires... I've been researching a little, and a few are ELRR but they are loud or reviews say they wear out fast. The tires that are quiet, aren't that low RR...

No AC
 

I consistently get 20mpg city/22-24 highway, with all but one of the rear seats out (the one furthest back, not the boat anchor captain's chair, I keep it tuned up, proper tire inflation and lighter than stock wheels and LRR tires. I couldn't give up my AC and power steering, and all the other stuff for a 3 mpg difference. You must live in a cold part of the country? I drove a Honda civic for three years that got 40mpg. I finally sold it because I was constantly roasting in it, sweating upon arrival at every destination with wet clothes, because it had no AC. I bought the previa because I had one before and mostly to have a car with AC, and the one I had before got the same decent mpg. Its not like the domestic vans which get 16/20 mpg if lucky.
Seems like a lot of extra work, just to save a few mpg. That and if you aren't a mechanic (I'm not, I'm a girl, I wouldn't have a clue how to do any of this stuff), you can't find anyone to do these mods. I'd be more interested in what things I can remove from the body itself (non mechanical) to make the car lighter, cause that seems like it helps a lot. I had that goofy spoiler removed with the plastic tracking and motors for the middle sunroof, holes filled in and spot painted, that took a lot of weight just off the roof and it looks a lot better too, as those spoiler/sunroof combos make the van look top heavy. The body shop sealed up the middle sunroof too.

I live in near vancouver BC so I rarely have to use the AC.

You have probably done all you can for weight reduction. The only other things I would suggest is the spare tire under the rear bumper and the jack and tools under the passenger seat. If you have On-star or AAA then you could risk a flat without a spare. Some people keep their gas tank low to save hauling extra gallons of gas around. Fill the back with helium balloons? Some people also remove all the carpet and panelling but that looks like crap in my opinion. I like my previa so I keep it looking good.

Some kind of fuel efficiency instrumentation can also help a lot.

It's too bad there are no ecomodding shops around. You can bet if the price of gas stays high there will be.

Not to be a "one-upper" but I got 26.48 MPG in the rain, moderate traffic between Federal Way and Olympia today. The only 'mods' I have made are to air the tire up to 44 PSI and remove the two bench seats. I do make sure to go about 1mph slower than the average traffic speed, just to avoid any unnecessary braking.

To be fair though, I used two different gas stations (pre trip was Chevron and post trip was Costco). So possibly the first pump filled a little more than the second (I always let the pump go until it shuts off automatically) which may have skewed my results. Also my trip consisted of approximately 95% freeway travel.

One of these days though I'd like to try sealing over all the unnecesary seams in the body (maybe use a little tape?), and removing the luggage rack from the top of the vehicle. Or maybe try the golf ball dimple effect (seen Mythbusters lately?) except in a plastic thermoformed panel version.

K&N air filter time Automatic 2 MPG at least

On my own Previa, I would probably prefer to have some sort of A/C clutch type mechanism for the alternator, so that I could engage the alternator at will. This would give the batteries a little more range (at the cost of fuel economy, but one could engage it on long downhill sections).

Do you use a battery isolator at all? It seems like you could potentially be in a lot of hurt if your batteries give up while on the road. Maybe even carrying a solar battery charger could help just a little, even though they would add some weight.

I guess you didn't check my fuel log. I usually get about 35 mpg on the highway driving at about 55. 90 day average is currently 27mpg. I live on a very hilly island and most of my trips are short. I used to get 15-17mpg on the island.

One upping is what ecomodder is all about. You highway mileage is darn good for a mostly stock Previa.

Officially referred to as basjoosing. I used foam weather stripping from home depot. Almost invisible. Comes in a bunch of sizes. Luggage rack delete - good.

The A/C clutch idea is oft talked about but I've never seen one done. Would be cool to have. Most people have gone the much simpler route of a switch to the field coils to disable it.

I have a spare battery, amp meter and voltage meter. I have run low a couple of times but only ran out once. My charger unplugged somehow during the night so I only had 30% left to get home. 120Km I had to stop at some point didn't have enough juice to restart. I would have been fine if I didn't have to shut off the van on the ferry. A nice gas station attendant let me charge up with my 25 amp charger for a while and I was on my way in about 20 minutes. Now I have a 50 amp charger so I only need half the time to get enough to get home.

Once you learn about amp hours and get used to your system it becomes just like making sure you have enough gas. I never worry anymore. Just the one accident.

That may be the more "efficient" way to do it-- the clutch system may add much more rotating mass. I guess that's getting all into the deep theoretical here, though. Still, either way it'd be nice to be able to recharge a little. It'd be interesting to have an automatic system monitoring the battery state to override and start charging.

I just finished a cesarean section for previa (I'm on call today); I have to say that's one of the worst names for a car I've ever heard

Does the car look like a placenta sitting on a cervix?

You think THAT'S bad, the '64 Chrysler Epidural probably beats that out.

It is funny when typing into Google it will autosuggest "previa placenta" among the other common searches.

hahaha ok do an image search for 'epidural' and then one for 'previa' and you tell me which one looks nastier. I lost 2000cc of blood with the previa, I don't lose any when i insert an epidural

Chrystler epidural? I'd think that was some japanese car that was lost in translation, but it's chrystler.....

Some manufacturers are using "smart charging" charge as much as possible when decelerating, and at the most efficient times.

I learned pretty quick to add -placenta to any searches on Previa.

Sounds fine If you don't know what it means.

Probably not implemented on the '95 Previa...

I could wire it with the brake light switch-- so when I'm braking, it will activate the alternator.

Granted, that could be somewhat counterproductive when stopped at a light, since the brake pedal is usually held for that. But when letting off the brake and leaving the stoplight, the alternator won't interfere with acceleration.

Orange4boy,
Do you run with that accessories driveshaft hooked up? When we had one I always wondered how much HP that system required. It's great to see a Previa on here, they are my favorite van because they are so innovative. Down right useful too.

The driveshaft is still installed but the belts are off.

Best van evah!

Actually, it would be best to have it hooked up to charge during engine braking, and acceleration. At idle, the engine is at it's most inefficient. Most efficient is at low rpm, large throttle opening.

I have a 96 SC. The Clutched SAD is a very interesting idea. Clutched off the main pulley and that way at steady cruise it would drop both the Power steering and Alternator.

Micro switch on the gas peddle so that when it is fully released it would kick on and recombinant charge. For coasting adjust a slight amount of slack in the throttle cable so you can keep it disengaged if you want but not feeding it any fuel. Wire the A/C so if it is turned on it overrides and keeps the clutch engage.


I think I read you were contemplating trying to EV through the SADS? Sounds good on paper but the couplers are crap and I think you would be replacing them often. If you plant to do that then I think you would have to put a true driver shaft in with conventional CVs or universals.

Why not get a 4x4 truck transmission and transfer case and EV drive via the front output?
I think it would be possible to use a gear drive case with what is know as a "dual shifter" That would allow you to engage 4x4 (or the electric motor in this case) but get the gear box in the case into neutral to disconnect you from the regular transmission.

Prefer Previa or...?
 

Hey there,
This is my first post. You're very ambitious to be making all these changes to your ride. I am thinking of getting a Previa, but the low mpg is a bit discouraging. I guess that is what modding is all about, though. Why settle for less.

That being said, are there any other vehicles similar to the Previa that do get better gas mileage to start with?

Also, have you ever heard of pre-vaporizing fuel to increase efficiency. How about adding a fuel cell to add a little umph? These might be bad ideas from an explosive stand point :(

Anyway, glad to be here :)

Mpg is a factor of weight, gearing,parasidic drag (both mechanical and aerodynamic). The previa is about as clean as it gets for the size. Interestingly the sc models has higher gears 3.73 then the non sc models that make the vehicle turn lower rpm on the hwy. But the sc gets worse mpg. Non sc owners frequently report mid 20's and those with manuals report high 20's. This may be a explained by the engine is in it's sweet spot. But the sc is on the verge of lugging and not disengaging the super charger.
I wonder if putting 4.10 and a manual transmission on a sc would be an improvement.

Modding the engine in the SC to get more low-end torque would help as well, as you'd be able to run lower rpm without lugging, and may actually be able to get better mpg than a non-SC, with the extra power when desired.