Unichip, power window and wiggling speedometer needle

by Ferman Lao | Jun 3, 2013

Good day to you, sir Ferman!

I am just going to ask questions regarding our cars: the Mazda 3 1.6 and the Toyota Revo diesel variant. Regarding the Mazda 3 1.6, I read online that this car has a heavy body and its engine is too weak for it, thus making the car a gas-guzzler. I researched on how to counteract this problem, and I found Unichip. Is it true that it will help improve the fuel consumption, or will it just make us spend more on fuel? My father is planning to install one this year, and I just want us to be educated before we buy one. If Unichip can't help, are there any other alternatives out there?

Meanwhile, the driver-side window of our Toyota Revo does not automatically roll up. Based on the sound of the window as it rolls up, it seems the power is insufficient. Is there any do-it-yourself job to fix this? Also, when the Revo's odometer reached 100,000km, the speedometer needle started to wiggle whenever it reached 20kph all the way to 70kph. Is this normal?


I hope to get a reply from you soon. Thank you and God bless!

Perci Calzado

Hi, Perci. It is true that the engine of the Mazda 3 1.6 could use a bit more power. The fact that the choice of transmission (automatic) that comes with it also saps quite a bit of power (and thus fuel economy, particularly in stop-and-go conditions), doesn't mean that you can't do anything about it. You and your dad are on the right path in thinking that getting your car tuned will result in better fuel economy, and using a Unichip is one way to go about it.

The Unichip and low-restriction free-flow air intake and headers will help. Combined, the modifications can improve the efficiency of the engine to a good degree--I've observed a significant improvement in a Mazda 3 that a friend owns. It used to do about 7km/L when it was stock. After the modifications, the car did about 9.2km/L under the same traffic conditions that the owner encounters on a daily basis. The car also felt much lighter and easier to drive after the modifications. It didn't feel heavy. On the dynamometer, the modifications resulted in an improvement of close to 20hp over the stock version.

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Whenever you improve the power across the power band of a vehicle and adjust your driving habits to make the most of the improved power and efficiency, you will usually end up with better fuel consumption. This happens because, for any given rpm and throttle opening combination, there is more power than before it was modified. Consequently, your engine can generate the same power as it did before at either smaller throttle openings or lower rpm. This helps you save fuel.

Regarding your Toyota Revo, it looks to me that its power-window mechanism has a worn gear somewhere in the power-window system. It is likely that it is one or both of the gears that connect the power-window motor to the linkage mechanism that moves the window up and down.

A trip to a qualified service shop that would open and check your door siding should be able to confirm it. Swapping out the entire power-window mechanism is the best way to go about it. It may also be possible to replace the gears if you can get them as spare parts. That should be cheaper and should serve almost as long as replacing the entire mechanism, although it takes a bit more time to fix. The former you can probably do yourself, while the latter is a bit more complicated and may be more difficult to DIY without the proper knowledge, tools and experience.


Your speedometer needle may be the same case as the power window: It has worn-down gears or your speedometer cable needs replacement. Again, I recommend having it checked at a qualified service shop rather than a DIY job if you're not used to DIY or not familiar enough with how the system is put together in a car. Removing it is easy, but putting it back together might be an entirely different thing. Remember, DIY also stands for "destroy it yourself."

Best regards,

Ferman Lao
Technical Editor

Do car problems keep you awake at night? Send questions to topgear@summitmedia.com.ph.

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