26.2 mpg Toyota Previa. Go Golden Egg!

[roflwaffle]

Originally Posted by MazdaMatt

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.

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.

[orange4boy]

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.

[roflwaffle]

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.

[orange4boy]

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.

[roflwaffle]

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.

Originally Posted by Wikipedia

For normal use, the selection of a spark plug heat range is a balance between keeping the tip hot enough at idle to prevent fouling and cold enough at maximum power to prevent pre-ignition leading to engine knocking.

[orange4boy]

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

[orange4boy]

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...

[Oval_Overload]

Originally Posted by orange4boy

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.

Awwa... Your using Bull parts 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]

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.

[orange4boy]

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