Wah bro put so much effort into this. Let me add my 2 cents
Hi Liang95,
Honestly speaking, Vios by stock itself is quite lively, it can keep up to some bigger CC car due to its light weight body. It was never made for highway speed monster. Like most ZTH citizens here recommended, try to make the car handles better and more stable than stock. What you can do:
Handling Part
1.) Stickier tyres
BEST MOD, BEST ROI EVER, 5/5!
15" is the best size, but performance tyres are less and lesser. Still good tyres, PS3, Hankook Ventus V12e2. If you can afford it, go for 17" then you will have a wide range of expensive rubbers.
2.) Lighter rims, more responsive steering wheel, however you might feel lightness in your steering wheel on highway speed
SECOND BEST MOD, STYLE TOO! ROI depends on how much you spend. Don't buy VOLKS lah, too expensive. ROI 4/5 to 1/5 depending on how much you pay.
Advanti DST rims are lightweight, and priced quite comfortably. Even if your stock rims are 15" and you ask, why "upgrade" to aftermarket 15"? The answer is tread width. The rims need to be wide enough to have sufficient contact for the rubbers. Detailed guide here. Lighter rims will also have less unsprung mass, better performance, better braking, better handling.
https://motoiq.com/how-to-properly-select-and-size-tires-for-performance/
3.) Uprated struts and springs, if not, BC Racing V1 or BR Type if you have budget
Done right 4/5, done wrong 0/5. The most common problem is that its "low" for better handling, lower center of gravity. If you determine how low you should go by the looks and not the suspension geometry, most likely its done wrong.
However, for macpherson strut cars like the Vios, you can go too low and impact handling, this page will explain it:
https://motoiq.com/the-ultimate-han...one-unforgivable-sin-overlowering-your-car/3/
Most of the time, it is done wrong, and the best is just stock really.
4.) Install necessary chassis bars, research this properly, you don't want to waste money on those bars you do not need, car needs certain roll to be able to change direction
5/5 when done correctly. The most obvious one is the strut tower bar. And anti-roll bar. Unlike tyres this one don't wear out. Worthwhile but don't go overkill with ALL sorts of bars.
5.) Chassis foam, for better sound proofing and sturdier chassis. Ever wonder why Euro cars are so solid and quiet ? Sturdier chassis and undercarriage is one of those keys. It also adds comfort to reduce NVH. You feel you can drive the car for as long as it could.
Doing this aftermarket, the impact really isn't that great. I've done it, at the most famous and pioneer of foaming. 1/5 for me.
6.) Harder engine mount, reduce engine flex and get the car going off the line faster. May cause discomfort as you feel more engine vibrations
Haha you'll regret it for a street car. For the ROI and pain, 1/5 for a street car.
7.) Better brakes ! Seriously a lot of people thought the factory brakes system is enough, it is NOT ! At least uprate the disc rotor, brake pad, brake hose and DOT4 brake fluid.
Better brake pads, ss braided hose and of course the DOT4 brake fluid (make sure its fresh sealed bottle). 5/5 if you choose good brake pads. Brake rotors of the same size for street driving is 0/5. Brakes stop the car by turning it into heat. More mass can contain more heat. So unless you change to the big brake kit with bigger rotor... changing just the rotor won't make a difference.
Brake pads are rated by temperature. Using race pads on the street would probably end up pretty bad if the driver is unaware of it. Plus race pads squeals like a pig.
Engine Part
8.) Uprated intake system, only helps the car to breath easier but won't gives you 10+ hp like some ads claimed. Especially on a 1.5L N/A engine
If just dropping in aftermarket air filter, just pick K&N. Washable and reusable. 2/5
Changing whole CAI... stuck in jam most of the time.. 1/5, heat soak anyway. And no turbo, what for.
9.) Free flowing exhaust, this one depends, but for me, just decat one of it will do. You won't want noisy exhaust in your DD.
This is the MOST SIGNIFICANT MOD, in terms of, awareness. You will be VERY AWARE of this mod. ROI on a naturally aspirated car? -2/5 for street driving. 2/5 for track driving.
Usually there isn't any increase in mid range torque or horsepower, sometimes there's even a dip. Mid range is where a street car spends 90% of the time. unless you drive pedal to the metal all the time. Just because its louder doesn't mean its more powerful or faster.
10.) E-throttle controller, this can dramatically change the pedal responsiveness but will not add HP
No comment on this. It's just a "feel" thing. I don't pay for feel. I pay for real absolute gains.
11.) Better spark plugs and ignition system, most likely the most obvious power gains for any N/A cars, if you have access to TM Works ignition package, this will be the most obvious power gains you ever invested, however, ITS NOT AFFORDABLE !
Changing to Denso or NGK iridium spark plugs, now most cars come with it anyway. 5/5. Ignition system, ROI 1/5. Very costly, I think spending the money on exhaust and full intake more noticeable in terms of noise and style. 2% on a car with 100hp is 2hp. 2% on an evo with 300 hp is 6hp.... Does TM Works got gains? Got, confirm got. Question is, you pay the same price as the evo owner.. you gain way less.
12.) Larger TB with larger intake pipe. Adds throttle responsiveness and gain power at mid to high RPM. Not usable if you don't rev the crap out of the engine to get its full benefits.
Might mess up your ECU tuning, if the intake of air is out of the range for the stock ECU. Actually even more significant is the intake ports itself are larger. I changed from a YRV head to a Myvi 1.3L lagi best head because the ports and the corresponding valves are physically bigger. No tuning definitely messed things up. ROI is 0/5 for no tuning, 2/5 with tuning on N/A car, 3/5 on a turbo car.
13.) Aftermarket VVTI Valve, enable VVTI opening at lower RPM (Not VTEC like but under normal driving you feel the engine is lighter)
Tak tau.
14.) ECU remap, another obvious power gains but need to find someone that really knows how to tune.
Vios can't remap, will need piggybacks like E-Manage. Not much use unless changes have been done to the intake or exhaust. Problem is 9/10 don't know how to tune. ROI? 0/5.. you find someone who knows how to tune.. with no mods.. 1/5 maybe. with mods.. on N/A.. 2/5..turbo.. tuning.. 5/5 because increase boost yo!
What i suggest, the handling part for now is the best thing you can do, as one once said, power is useless without control. It's 1.5L N/A engine
Correct.
Stuff you can do for free, ROI 5/5:
Remove the rear seats & spare tyre, less weight.
Turn off the air con compressor, free power.
Remove crap in your car.
Get a lighter wife/girlfriend or boyfriend (if that's your thing, I don't care)
Lose weight yourself