Archive for the 'General' Category

Does water injection system improve fuel efficiency?

Edgar’s question:

I’m trying to get better gas mileage in my 99 F 150. I’ve seen those ads for water injection systems in magazines and on the internet. Do those things actually work?”


No, they only work to take your money and can actually harm your engine in the long run. Water injection is a real process in piston engines, BUT only in VERY specialized cases. The later model P 51 Mustang fighter planes in WW II had water injection for short term emergency use. You want as much power as possible when people are shooting 20 mm cannons at you. The water helped cool down the supercharged engines and let them put out more horsepower. But putting a water injection system on a modern car or truck is not a good idea. Modern vehicles, when they are running correctly and have no problems, burn 99 percent of the fuel efficiently. So you really only have the ability to inprove combustion by a measely one percent. And that isn’t much of an improvement (plus it would be nearly impossible to squeeze that last one percent out anyway.) In September 2005 Popular Mechanics tested a water injection system out, and discovered the vehicle they put it in actually got twenty percent worse gas mileage. SO, leave that nonsence alone. The only way to get better gas mileage is to raise the gear ratio in the transmission (so the engine spins slower at a given speed and uses less gas) or lighten the vehicle’s overall weight so the engine has less to pull around. And of course you can make a vehicle a hybrid design, using electrical motors and regenerating brake systems. But changing a vehicle you already have into a hybrid would be an immense task, you’ be better off just buying an already made hybrid.

Car PC INstallation Wiring

Khalid’s question:

I am planning to install a car pc with which i want some wiring advice. for the power supply (90watts output & 6 to 12v input), it needs 3 connections, 1 for 12v, 2 for ground and 3 for ignition. now if i run the 12v and the negative direct from the battery, can i tap into the ignition wire connected to my head unit to run the pc also? in other words i would solder 2 pieces of wire on the ignition wire to run both the head unit and the pc. would that be okay or would the load be too much for the ignition wire? also what amp fuse should i use inline for the 12v connection?”


I personally wouldn’t use the ignition switch for anything other than what it was designed for in the car. I would wire it all direct from the battery, and if you want to put a toggle switch on ones you want to turn on and off (just like the ignition switch turning on and off.) Cars ignition switches get power surges when the car starts and it could mess with your computer. As for the fuse amperage, 90 Watts is a lot of power. I would use a 25 amps fuse for protection.

Steering wheel is shaking like mad when I’m driving under thirty miles an hour

Randy’s question:

My steering wheel is shaking like mad when I’m driving under thirty miles an hour. It gets a little better when I go faster, but it’s driving me nuts. What should I check first?”


Well, the first thing to check is the two front tires. Jack up the car and spin the tires. Odds are you’ve got a bad tire–either with bald sports or out of round parts. Spin the tires and see if they are perfectly round, or have lumps in them. If they have lumps or are going bald, replace them. A really wobbly steering wheel at low speeds is almost always a bad tire or bent tire rim from hitting curbs and such. High speed wobbles can be lots of things, from unballanced tires to worn front end parts. BUT low speed wobbles are almost always just bad tires and or rims. Low speed wobbles are the easiest to repair because the cause is such a large problem that it’s hard to miss when you look.

Does waxing come before polishing?

Jay’s question:

Hi, i am a bit confused about waxing and polishing. For best appearance and protection, do i polish that car with a good polish (meguiers) first and then apply the wax?”


Yes, you hit the nail on the head. Polishing removes imperfections on the paint. All polishes are in reality just very fine abrasives that remove small bits of imperfections. BUT, they also remove the wax when doing this. Hence, you must rewax the car after the polish has dried and has been itself removed. Always use separate towels for polish and wax, so you don’t get the two substances mixed in together.

I am looking to buy a car for which i need some advice, its either a VW PASSAT or a MERCEDES C180

Khalid’s question:

Hi I am looking to buy a car for which i need some advice, its either a VW PASSAT or a MERCEDES C180. I have seen a VW 20V 1.8 PASSAT which has done 89k miles and a R REG MERCEDES C180 which has done 117k. Which do you think is worth buying as i intend to work as a cab driver. Which do you think is a better car overall? “


I personally wouldn’t buy either, they are both rather high maintenace cars with histories of heavy breakdowns. I’d go Toyota if at all possible. BUT, if you have to pick one of your choices, the Passat would be the lesser of two evils.

MAF cleaner results

Jeremie’s question:

” Thanks for saving me a ton. I cleaned out the MAF sensor and the throttle plate with mass airflow sensor cleaner. Just like you’ve said in other posts, I got a can of MAF cleaner that CRC makes at Auto Zone. Now I know how to keep my VW running smoothly. But how often should I do this cleaning?”


Oh, you could clean it out a couple times a year if you want, since it’s such an easy job on your VW to get to those parts. But it probably won’t be necessary to do it that often (unless it starts running poorly again.) Once a year is generally fine in most circumstances.

$3500 Free Voucher to purchase new car

Peter’s question:

“Hi , I was told that an old car not able to pass State Inspection can be stopped and given a voucher for $3500 for purchasing a new car. I have a 23 years old car that may not pass next month. What do I need to do in order to get that voucher? Thanks for your helpful a prompt answers. Regards, Peter”


Well, different states have different laws, so check the laws in your area. Here in Texas it’s a deal that you get a certain amount of money to be credited for buying another car if your personal income is below a certain specified amount. If you contact the DPS through phone or their website. The rules are always changing, so check BEFORE you take a leap. And realize that whoever accepts these vouchers is probably going to hit you pretty heavy on the price they charge for another car (these deals often negate any bargaining over price, so Be Wary.)

How to find ignition wire for car stereo setup

Khalid’s question:

” Hi , can you please tell me how to know which wire is the ignition wire when wiring the stereo and can i use a normal light tester probe to find the ignition wire. Also if i want to wire couple of things to the ignition wire, do i use the same wire to connect all the products or is there another way of doing this.”


Personally, I would never wire anything off the ignition wire, it can mess things up (there are actually more than one wire which get power when you turn the ignition on.) If you do want to find one to use just for that little ignition wire on a modern fancy radio system, just take the plastic off the steering column to access the wires, and when you turn the key on, check them with a test light and when the light comes on, that’s got power. BUT, you really should wire other accessories directly off the battery positive post, using the correct gauge wire and correct fuse for whatever application you’re using. That way you won’t mess up the electrical system by hooking up something where it shouldn’t be (it can really open up a can of worms that you won’t like the results of.)

AC Warm At Low Rpm

Cons Santos’s question:

” Just recently my AC evaporator has a leak and has been replaced by a technician with a new evaporator. However, during engine idle(RPM 1000), cooling is poor while during high RPM 1500 and Up, cooling improved significantly. I hope you have a suggestion on what to do next. Thanks.”


It could be a few things doing that. One, he just might not have put the correct amount of refrigerant in. Two, he may not have changed out the AC drier, in which case the system wouldn’t flow right at low speeds ( ALWAYS change the drier when the system is opened up.) Three, it could be a cheaper aftermarket evaporator which just won’t work as well because the cooling tubes inside it are too small, I see that a lot with cheaper Chinese made replacement evaporators. These are the three most common mistakes people make when working on an AC system that would cause your exact problem. Good Luck,

Piercing electrical test leads

Geff’s question:

“When you use piercing electrical test leads as you mentioned, do you have to tape the wire up after piercing the insulation.”


Not if you’re really careful and use one of those really sharp pin head piercers. They make a REALLY small hole that pretty much seals back up when you removed the test lead. And anyways, tape is kind of weak, anytime you mess with wiring it’s best to use shrink wrap tubing to cover the wiring then melt it with a heat gun (or hair dryer on full blast.) And smaller wiring holes can best be sealed using silicone sealer from a tube.