Toyota GT86 CS R3

Since the FA20 engine is quite popular in Australia I want to check if someone already tried to gain some power in NA configuration (so no compressor or turbo)

We have a FIA spec GT86 CS R3 rally car and since homologation is finished we are looking for some extra HP's. (without adding compressor or turbo)

The engine is 100% conform to the 2017 spec (latest available) and has different pistons,cam's, oilpump, inlet, special manifold,.... but due to the FIA R3 regulation the compression ratio is slightly lower compared to a stock engine. (12:1). Has anybody ever tried bigger (single) throttle body? Now it is dia 65mm. We are just looking for 15-20 BHP extra but it looks as there is no room for any gain. We need to keep in mind that we do not loose any torque because it is for a rally application. Today we are 222 BHP and 230Nm torque with a small dip in the torque 4500 revs and 6500 revs (-10Nm), I guess we can flat this out by putting some extra effort in tuning the VVT. I would like to understand if there is still something to gain. It is a super fun car just lacking a few BHP's

I couldn't guess how much room is left to add HP given your setup and unknown calibration, but VVT, ignition timing, fuel all play a roll in the dips and HP/TQ in general so some time should be spent on optimization.

If running out of spec, choose a fuel which is more highly oxygenated. That plus retune could add the power you're wanting.

Larger throttle body and intake do help as well.

The stock throttle body on the FA20D (cold air intake, decatted 3" exhaust) does not have a performance advantage over being opened more than ~85% (dyno tested and backed up by a number of professional drivers in blind testing) so unless you can increase the mass flow through the engine you are not going to get a gain from the larger throttle body, in fact, there can be some driveability losses from going to a larger throttle body.

Is this one of the CS R3 cars with the MoTeC M150 fitted?

No specific recommendations, you're just going to have to go 'old school' and look at the whole thing from start to end - nice cold fresh air, low restriction intake path - maybe with heat shielding, maybe nylon/phenolic (sp? ) plastic intake spacers, optimised valve timing to reduce the flat spot - but intake and exhaust lengths may limit that, on that you may need to address the exhaust system within the CAT' requirement, etc. Maybe look at a lighter flywheel/clutch assembly and see what's available for rear axle gears and whether a CR gearbox is an option - but those may already be in place.

You may be at least as well served by looking at other aspects of the vehicle, like wheel mass and tyres, brakes and suspension, etc, to see if there's something that hasn't already been done.

If it's an electronic throttle you may be able to map the opening to pedal to rpm, as sometimes you can gain power/torque from partially rather than fully opened throttle.

Modern head castings are very good, but there may be some potential benefits there?