How to Modify an Automatic Car?

Back to my roots a bit. Below is a post I made today in Autoworld.com.my. It's about modifying a Proton Waja automatic for better driving, but the general points relate to any car with automatic transmission.

posted on 3-Jun-06 21:24 [edited 0 times] [edit] [delete]
>So, any advice on how we should 'improve' our Waja Auto to make it more
>exciting, in terms of acceleration (from standstill and on the move). My
>Waja EV seems to lack any form of pull, which I think it's because of the
>205/55/R16 wheels.

>Will a budget of RM 3k be sufficient? or should i just keep the money
>until I can fit in a larger cc engine?

If you want my honest opinion, think about doing a manual conversion. I spent a lot of money to get my ex GSR auto to 260+hp because I wanted to keep the autobox and still have 200hp at wheel. Looking back, I'm not sure it was the best thing to do. Doing a manual conversion gets you 10-15% more wheel hp immediately with no engine mods.

IMHO, if you want a fast automatic, you need horsepower. And you'd want lots of it at mid range.

There are only 2 ways to do that. More displacement and turbo. That's it.

Nothing else works as well, not cams, not intakes and exhausts, not ECUs etc. Why? Because these things give power at high end. The only way to get more power from a small capacity engine is to multiply that capacity with more rpm ie. work the engine harder. It's that simple. Besides, for a small and low performance engine like the 4G18, whatever gains made are so small that the autobox's transmission loss will swallow it up.

But, there are a few things that will allow you to get better 'feel' from your autobox. Minimise transmission loss rather than add power.

1. Lose the 16 inch wheels. Unless they are superlight magnesium wheels, dump them. Get a set of light 14" or 15" rims like Volks TE37 or SSR Type C etc. This will make a huge difference in the sluggishness you feel.

Then get some good tyres. Do a brake upgrade like good high temp pads or a twin pot caliper replacement. Why? It allows you to brake later and left foot brake through turns. What this means is that you'll carry more speed through the corner and have high engine rpms at the corner's exit. Don't look down on the effectiveness of this. On my dad's old 1.5A, using left foot braking, I can pull away from Putras going around a roundabout. But after the roundabout, dielah of course.

2. Use synthetic ATF like Redline Oils and make sure you use the correct grade eg. SP or Dexron III or IV. And put in a small ATF cooler. Use a small but high power fan to pull maximum airflow through it to compensate for the small size. Look at an Eterna Twin Turbo V6 and copy the ATF cooler setup. This should overcome that wall you hit near top speed in 4th gear. And gives your autobox some protection from that left foot braking also.

3. The following will improve low-mid response but for a 4G18, I don't think the gains are worth the money. Get a good tuner to screw around with your ignition timing and fuel injection for better low rev response. I used SAFC/SITC so that I can max the low-mid rev settings without jeopardising high rev. These days you can use Greddy Emanage etc as well. A bit of cam timing tuning using an adjustable cam pulley or even a cam change might help low-mid, but only with a master tuner. Lesser tuners might fark up the low-mid & high end balance. For the least expense, instead of fooling with electronics and cams, I would simply change the stock crank pulley or main pulley to a light aluminium one. On a GSR, this takes away almost 2 kgs of rotating mass and makes the engine much lighter or free revving at low to mid. If you want, you can also consider lightening or underdriving the aircond and power steering pulleys.