Lightweight and cool is good...

Moto's AE86 Part 6

by Moto-P

After previous talk about the E&E System's Freedom ECU, engine management system, and it's success, we now move onto a more accessible part for everyone.  As we all know, one of the most important advantages of the AE86 is its weight, and by reducing the weight further, we get better braking, cornering and acceleration.  This is a point many drag racers as well as road racers alike, do not deny. The normal off the shelf Japanese spec AE86 weighs in at 1040 kg fully optioned and US models can weigh as much as 1090 kg with options such as power windows, sunroof.  The USA spec models do suffer from 5mph DOT standard bumpers, which add 46 kg to ends of the car, a tradeoff for increased passenger safety and resistance to minor damage. 

While this is a very controversial issue and illegal in all states of the USA, replacement with the Japanese or European specification bumpers add the following attributes to the AE86.   The Japanese bumpers offer more ventilation due to the increased number of ducts integrated into the bumpers, and the absence of the steel reinforcement beams running across the front.  This in turn lowers the operating water temperatures of the engine by roughly 10 degrees, and oils by another 5 degrees Celsius or so.  As a side note, you should always replace damaged or missing engine bay under cover. That plastic sheet under the engine, which covers fore and to the side of the oil pan?  It functionally redirects air in a smooth current and out the back of the engine bay, and does a significant part of the cooling process at speed.  This is especially true for AW11 and SW20 MR2 owners as it serves as an inlet to draw air out of the top of the rear engine bay.

Back to my AE86, another significant part of the cooling process and drawing air positively from engine compartment is additional top vents.  One can achieve this ala Volkswagen trick by using nuts or washers and long screws to prop the hood up at the rear by half an inch or so.  Cutting vent holes and ducts are very effective as well.  When making hole sin the hood, you should always vent directly after the radiator.  In the case of the AE86, it would be above and between the radiator and the timing belt cover.

On the drive to get lighter weight, this time I had the opportunity to install a FRP (fiberglass) hood or bonnet, to the project AE86.  This item weighs 8.2 kg, compared to the steel OEM hood at 15.3 kg.  As you can imagine, with that much reduction in weight at top front of the vehicle, the turn in response becomes noticeably sharp.  The car will exhibit less roll so suspension now must be adjusted to bias the weight in front or replaced with softer front springs.  The hood was ordered from Greddy USA, who deals with Cusco parts in the US.  It is available still, however, is not a stocked item so the wait time is rather lengthy 3-4 months.

Additionally, as yet to be done to the project AE86, a rear hatch made of FRP and Lexan glass area, should reduce the car's weight further by another 20 kg or so.  Removal of the floor insulation results in 4 kg more weight loss as well as rear seats, which reduce the car by 17 kg.  You may not be so enthusiastic about removing so much content from the car but for serious competitors it is a prerequisite.  Easily shaving 100kg or more makes for a car that has equivalent of that much power with the additional benefit of improved braking and cornering.   In autocross, one 80 kg person strapped to the passenger seat costs 1 to 2 seconds with top class driver in most cases and that can translate into lots of loss if the laps add up in a sprint or endurance.