--Engine

function Engine()
	--Neutral Gear
	if _CGear==0 then _ClutchOn = false end

	--Car is off
	local revMin = _Tune.IdleRPM
	if not _IsOn then 
		revMin = 0 
		_CGear = 0
		_ClutchOn = false
		_GThrot = _Tune.IdleThrottle
	end
	
	--Determine RPM
	local maxSpin=0
	for i,v in pairs(Drive) do
		if v.RotVelocity.Magnitude>maxSpin then maxSpin = v.RotVelocity.Magnitude end
	end
	if _ClutchOn then
		local aRPM = math.max(math.min(maxSpin*_Tune.Ratios[_CGear+2]*_Tune.FinalDrive*30/math.pi,_Tune.Redline+100),revMin)
		local clutchP = math.min(math.abs(aRPM-_RPM)/_Tune.ClutchTol,.9)
		_RPM = (  (_RPM*2*clutchP)  +  (aRPM*2*(1-clutchP))  )/2
		_HP = (_Tune.Horsepower/2) * math.sin((math.pi/((1+(math.min(10,_Tune.IdleOffset)/100))*_Tune.PeakRPM)) * (_RPM - (((2-(1+(math.min(10,_Tune.IdleOffset)/100)))* _Tune.PeakRPM)/2))) + (_Tune.Horsepower/2)
		_OutTorque = _HP * 5250 / _RPM * _Tune.Ratios[_CGear+2] * _Tune.FinalDrive
	else
		if _GThrot-_Tune.IdleThrottle>0 then
			_RPM = math.min(_RPM+_Tune.RevAccel*_GThrot,_Tune.Redline+100)
		else
			_RPM = math.max(_RPM-_Tune.RevDecay,revMin)
		end
		_OutTorque = 0
	end
	
	--Rev Limiter
	local spLimit = 0
	if _RPM>_Tune.Redline then 
		if _CGear<#_Tune.Ratios-2 then
			_RPM = _RPM-_Tune.RevBounce
			spLimit = 0
		else
			_RPM = _RPM-_Tune.RevBounce*.5
		end
	else
		spLimit = (_Tune.Redline+100)*math.pi/(30*_Tune.Ratios[_CGear+2]*_Tune.FinalDrive)
	end
	
	--Automatic Transmission
	if _TMode == "Auto" and _IsOn then
		_ClutchOn = true
		if _CGear == 0 then _CGear = 1 end
		if _CGear >= 1 then
			if _CGear==1 and _GBrake > 0  and car.DriveSeat.Velocity.Magnitude < 20 then
				_CGear = -1
			else
				if _Tune.AutoShiftMode == "RPM" then
					if _RPM>(_Tune.PeakRPM+_Tune.AutoUpThresh) then
						_CGear=math.min(_CGear+1,#_Tune.Ratios-2) 
					elseif math.max(math.min(maxSpin*_Tune.Ratios[_CGear+1]*_Tune.FinalDrive*30/math.pi,_Tune.Redline+100),_Tune.IdleRPM)<(_Tune.PeakRPM-_Tune.AutoDownThresh) then
						_CGear=math.max(_CGear-1,1)
					end
				else
					if car.DriveSeat.Velocity.Magnitude > math.ceil(wDia*math.pi*(_Tune.PeakRPM+_Tune.AutoUpThresh)/60/_Tune.Ratios[_CGear+2]/_Tune.FinalDrive) then
						_CGear=math.min(_CGear+1,#_Tune.Ratios-2)
					elseif car.DriveSeat.Velocity.Magnitude < math.ceil(wDia*math.pi*(_Tune.PeakRPM-_Tune.AutoDownThresh)/60/_Tune.Ratios[_CGear+1]/_Tune.FinalDrive) then
						_CGear=math.max(_CGear-1,1)
					end
				end
			end
		else
			if _GThrot-_Tune.IdleThrottle > 0 and car.DriveSeat.Velocity.Magnitude < 20 then
				_CGear = 1
			end
		end
	end 
	
	--Differential Stuff
	local fwspeed=0
	local fwcount=0
	local rwspeed=0
	local rwcount=0
	
	for i,v in pairs(car.Wheels:GetChildren()) do
		if v.Name=="FL" or v.Name=="FR" or v.Name == "F" then
			fwspeed=fwspeed+v.RotVelocity.Magnitude
			fwcount=fwcount+1
		elseif v.Name=="RL" or v.Name=="RR" or v.Name == "R" then
			rwspeed=rwspeed+v.RotVelocity.Magnitude
			rwcount=rwcount+1
		end
	end
	fwspeed=fwspeed/fwcount
	rwspeed=rwspeed/rwcount	
	local cwspeed=(fwspeed+rwspeed)/2
	
	--Apply Forces
	for i,v in pairs(car.Wheels:GetChildren()) do
		local Ref=v.Axle.CFrame.lookVector
		local aRef=1
		local diffMult=1
		if v.Name=="FL" or v.Name=="RL" then aRef=-1 end
		
		--Torque Compensation
		if _Tune.Config ~= "AWD" then _OutTorque = _OutTorque*1.3 end
		
		--Differential
		if v.Name=="FL" or v.Name=="FR" then
			diffMult=math.max(0,math.min(1,1+((((v.RotVelocity.Magnitude-fwspeed)/fwspeed)/(math.max(_Tune.FDiffSlipThres,1)/100))*((_Tune.FDiffLockThres-50)/50))))
			if _Tune.Config == "AWD" then
				diffMult=math.max(0,math.min(1,diffMult*(1+((((fwspeed-cwspeed)/cwspeed)/(math.max(_Tune.CDiffSlipThres,1)/100))*((_Tune.CDiffLockThres-50)/50)))))
			end
		elseif v.Name=="RL" or v.Name=="RR" then
			diffMult=math.max(0,math.min(1,1+((((v.RotVelocity.Magnitude-rwspeed)/rwspeed)/(math.max(_Tune.RDiffSlipThres,1)/100))*((_Tune.RDiffLockThres-50)/50))))
			if _Tune.Config == "AWD" then
				diffMult=math.max(0,math.min(1,diffMult*(1+((((rwspeed-cwspeed)/cwspeed)/(math.max(_Tune.CDiffSlipThres,1)/100))*((_Tune.CDiffLockThres-50)/50)))))
			end
		end
		
		--Output
		if _PBrake and ((_Tune.Config ~= "FWD" and (((v.Name=="FL" or v.Name=="FR") and car.DriveSeat.Velocity.Magnitude<20) or ((v.Name=="RR" or v.Name=="RL") and car.DriveSeat.Velocity.Magnitude>=20))) or (_Tune.Config == "FWD" and (v.Name=="RR" or v.Name=="RL"))) then
			v["#AV"].maxTorque=Vector3.new(math.abs(Ref.x),math.abs(Ref.y),math.abs(Ref.z))*_Tune.PBrakeForce
			v["#AV"].angularvelocity=Vector3.new()
		else
			if (_TMode == "Manual" and _GBrake==0) or (_TMode == "Auto" and ((_CGear>-1 and _GBrake==0 ) or (_CGear==-1 and _GThrot-_Tune.IdleThrottle==0 )))then
				local driven = false
				for _,a in pairs(Drive) do if a==v then driven = true end end
				if driven then
					local on=1
					if not script.Parent.IsOn.Value then on=0 end
					local throt = _GThrot
					if _TMode == "Auto" and _CGear==-1 then throt = _GBrake end
					local tqTCS = 1
					if _TCS then
						tqTCS = 1-(math.min(math.max(0,math.abs(v.RotVelocity.Magnitude*(v.Size.x/2) - v.Velocity.Magnitude)-_Tune.TCSThreshold)/_Tune.TCSGradient,1)*(1-_Tune.TCSLimit))
					end
					if tqTCS < 1 then
						_TCSActive = true
					else
						_TCSActive = false
					end
					local dir = 1
					if _CGear==-1 then dir = -1 end
					v["#AV"].maxTorque=Vector3.new(math.abs(Ref.x),math.abs(Ref.y),math.abs(Ref.z))*_OutTorque*(1+(v.RotVelocity.Magnitude/60)^1.15)*throt*tqTCS*diffMult*on
					v["#AV"].angularvelocity=Ref*aRef*spLimit*dir
				else
					v["#AV"].maxTorque=Vector3.new()
					v["#AV"].angularvelocity=Vector3.new()
				end
			else
				local brake = _GBrake
				if _TMode == "Auto" and _CGear==-1 then brake = _GThrot end
				v["#AV"].maxTorque=Vector3.new(math.abs(Ref.x),math.abs(Ref.y),math.abs(Ref.z))*_Tune.BrakeForce*brake
				v["#AV"].angularvelocity=Vector3.new()
			end
		end
	end
end

