As with any machine, its heart is the thing that makes it work. Its the center portion of every automotive story since the car was created...everybody always wants to know whats under the hood. The Toyota ae86 chassis came with variants of the "A" series motors that Toyota stuck in most of their smaller, lighter vehicles. First released in 1983, the 3a, 4a and 4ag would set a standard for reliability and endurance unmatched in the automotive world. The 4ag would go on to revolutionize the way that four cylinder internal combustion engines were viewed by the public. Never before had an engine been unleashed to mass circulation that allowed for a 7500rpm redline, especially not in an affordable entry level car. Sure, today this happens frequently with the advent of Vtec, Mivec, VVT/VVTi etc, but 23 years ago it was seen as more or less impossible. The fact that the motor could survive for well over 300,000km makes it seem that much more unlikely, yet these motors were produced in spades and continued to propel the Corolla until 1997 in North America and somewhere about 2002 in Japan. They are still powering the Toyota Formula Atlantic Series open-wheel race cars, with power levels well over 270hp out of a 1.6L motor from 23 years ago.
This is the heart of the ae86...it makes the car fun to drive, and is actually quite impressive in terms of "motivative force". 112hp wasn't shabby for 1983, especially in a car that weighs less than 2300lbs. Yes, it peaked at 6600rpm, and the 97 ft/lbs of torque peaked at something similar...but the car was a joy to drive. It did everything you wanted it to, had nice handling, perfect steering ratio, good brakes etc. Of course, 99% of these cars rolled off the showroom floor and into the garages of starter-families where the wife wanted something sporty-looking to drive, and not straight into a the grubby paws of road racers. Thus, the potential of the car was largely lost in North America.
Because of this, there just weren't a lot of parts available at your local speed shop for this thing. When we first started to mod the car, a lot of it was literally taking what we read in Car Craft and Turbo Magazine and applying it in custom-fashion to the 4ag. All the general rules of motor-dom applied, because that's all we were playing with. There's this misconception out there that an import motor is somehow different from a domestic motor, and a lot of people who understand domestic engines refuse to work on import ones because they're confused and scared. Well, you'll be pleased to know that imports have not bent the laws of physics, and that they respond exactly as predicted to the rules of volumetric efficiency. Naturally, if you open the hood of an ae86 with a 4ag, and you take one look...the first thing to go is the airbox.
The ae86 4ag comes equiped with a plastic air intake system that features a "silencer". Now, this is something familiar to everyone reading this...all cars have these now...but back then, it was kind of a weird thing to have on a car. Essentially, it is there to muffle off the intoxicating intake song of a 4ag at throttle. Unlike on newer motors, its quite restrictive. The silencer piping runs right across the top of the radiator, where it can get heated...which is a good and bad thing. Good because its better for the motor when its cold...but bad the rest of the time. To test the theory that less restriction is better, the intake piping disappeared one afternoon. That was like throwing fuel on a fire...the car was noticeably faster and sounded much, much better. Soon the entire airbox was removed and replaced with a custom K&N cone setup. The filter was purchased at a local speedshop, and attached to the air flow meter via the adapter off a 280zx. The intake piping was then hacked up and replaced with a rubber 90deg pipe adapter. Finally, the intake was supported with a custom bracket from the rad support.
This modification caused the car to lose some fuel economy, but the motor was far happier getting as much air as it wanted, rather than as much as it could get. It makes the 4ag sound quite a bit more powerful and potent, and that alone makes the mod worthwhile in my opinion. Of course, once the car is getting as much air as it wants, the logical move is to alter the exhaust to let it get all that good stuff out, again increasing the efficiency. This was done by taking the car to a custom exhaust place and having them bend a 2.5" pipe with a Dynomax SuperTurbo. At the time, seemed like a semi-good idea, and our doubts about the piping size were confirmed...its too big. In retrospect a 2.25" seems to be ideal, as I've since done a couple of those on other people's cars. At first the exhaust was far too loud, but installing a resonator fixed that in a hurry. Hind sight being 20/20, I'd highly recommend anyone reading this to just go buy an aftermarket exhaust. Its a lot easier to do, they last a long time, are sized to the motor far better with higher craftsmanship, are made of better materials and have less side effects than doing it yourself. A GReddy DD exhaust is prefabbed to fit under or over the axle properly, where as mine kept having to go back to the shop for "adjustments" because it would either hit the axle or the bottom of the car...sometimes both!
The headers/extractors/exhaust manifold (whatever you want to call it) on a ae86 is something of a puzzle. I'd often been told the oem factory piece was the best all-around header unless you were tuning for a specific powerband. I've tried three headers on my ae86 so far, and I believe that the legend is correct. I've never heard of a header doing anything but improving peak power on a 4ag, so there's not really much of a reason to swap it. Various header companies in North America are coming with or leaving with a header design of some kind for the ae86, and the majority of these are similar designs. The ones to avoid are Japanese Domestic Market headers, as they seem like a really good idea on paper but truly only fit right hand drive cars. Don't even try and argue...I have two in my garage to prove you wrong any time you want. So, I guess the moral of the story is don't mess with it unless you have to. My car currently features a Tri-Mil header off a parts car a friend bought. I have yet to find a header in the North American market that will optimize my 4agze project motor, so I'm pretty well stuck.
Before I go further, I'd like to point out two simple mods: Header wrap and tin foil. Now, as you pick yourself up off the floor, regain your breath and stop chuckling...these two things really do work! I highly recommend heat wrapping your header (should you ever have it off and cold) and putting tin foil over as much of your intake and fuel system as possible. Heat is the enemy, and keeping it out of the engine bay is a must. I even went so far as to devise a cold-air box out of a piece of super-dense upholstery foam that sealed off the K&N cone against the hood and front passenger fender, preventing the hot air from the motor from infiltrating the intake charge. All these mods combined can make quite a difference in how the car runs, and they're all quite cheap to perform. Check them out.
I guess the next major modification is the ignition system. I was always told that the 4ag would not benefit from a ignition kit for the simple fact that Toyota ignitions are already quite overbuilt. Well, I monkey'd with it anyway, and found some interesting things. For starters, my 4ag seems to prefer copper spark plugs...but Toyota specifies platinums from the factory. It also really liked having its ignition coil replaced, though no difference should have been noted because the stock coil should have been enough. Lastly, and against all logic, the car loved the NOLOGY Hotwires I put on it, though there were initial hickups when they were grounded improperly. The low end power of the car increased dramatically over stock, to the point where the car would break the tires mildly loose if urged at anything over 2000rpm. I intend to experiment with some resistorless plugs in the future to see what results can be had.
Other modifications to the engine bay include the removal of all emissions equipment. The EGR has been removed and plugged. The oxygen sensor has been torn out and plugged. The charcoal canister also met with the trash. The battery has been swapped out to a group 51R reverse-post Honda Civic batter with custom mounting bracket for lighter weight up front and better overall balance of the car. When we were doing the motor swap, the power steering system wound up in the dumpster next to everything else. This both lightened the car by some silly amount (that stuff is heavy!) up front, but kept the rotating losses of the motor down as well. Yes, the steering is heavier at low speed, but I have no regrets about removing it. The lines for the fluid attached to the steering rack were looped as short as possible and the rack was filled with fuild to keep it lubricated. On the far side, the entire washer system for the front window was removed, including pump, reservoir, nozzles and hosing. The heater core was removed unintentionally due to an accidental snapping, so the rest of the system went with it for good measure. Finally, all the engine wiring was rerouted as well as possible to hide it.
All the exterior panels and guards were removed to "brighten" the engine bay. A major, yet hidden modification is the oil cooler. I noticed a long time ago that the cooler sat right behind the front bumper's rebar where it doesn't get a direct blast of air. While the There are future plans for the engine bay, with the goal that it wind up as clean as possible...i.e.: minimalist. I have a goal for it in mind, but I'm not sure its attainable.