diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index 44060bae..fdf1ce1e 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -133,6 +133,9 @@ jobs:
         shell: bash
       - uses: actions/checkout@v4
       - uses: julia-actions/setup-julia@v2
+      - name: Build PyCall
+        run: julia --project=docs/ -e 'ENV["PYTHON"]=""; using Pkg; Pkg.develop(PackageSpec(path=pwd())); Pkg.instantiate(); Pkg.build("PyCall")'
+        shell: bash
       - uses: julia-actions/cache@v2
       - uses: julia-actions/julia-buildpkg@v1
       - uses: julia-actions/julia-docdeploy@v1
diff --git a/CHANGELOG.md b/CHANGELOG.md
index b3e91394..e01b6697 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,9 +2,18 @@
 SPDX-FileCopyrightText: 2025 Uwe Fechner, Bart van de Lint
 SPDX-License-Identifier: MIT
 -->
+### Unreleased
+#### Changed
+- rename `init_sim!` to `init!`
+- removed the parameter `upwind_dir!` from `init!`; use set.upwind_dir instead. Careful: This is in degrees.
+- the function `init!` accepts (and ignores) the parameters `delta` and `stiffness_factor` if applied to a 
+  SymbolicAWEModel
+### Added
+- add the test script test_interface.jl
+- add the field `integrator` to KPS4 and KPS3 structs
 
 ### KiteModels v0.8.1 2025-06-20
-#### CHANGED
+#### Changed
 - renamed POWER to POWER_LINE and STEERING to STEERING_LINE
 - improved documentation, fixed example
 
diff --git a/data/settings.yaml b/data/settings.yaml
index 6bf23425..24aed0c5 100644
--- a/data/settings.yaml
+++ b/data/settings.yaml
@@ -11,10 +11,18 @@ system:
     fixed_font: ""                 # name or filepath+filename of alternative fixed pitch font, e.g. Liberation Mono
 
 initial:
-    l_tethers: [150.0, 0, 0]       # initial tether length       [m]
-    elevation: [70.8]              # initial elevation angle   [deg]
-    v_reel_outs: [0.0, 0 ,0]       # initial reel out speed    [m/s]
-    depower:     [25.0]            # initial depower settings    [%]
+    elevations: [70.8]               # initial elevation angle   [deg]
+    elevation_rates: [0.0]           # initial elevation rate  [deg/s]
+    azimuths: [0.0]                  # initial azimuth angle     [deg]
+    azimuth_rates: [0.0]             # initial azimuth rate    [deg/s]
+    headings: [0.0]                  # initial heading angle     [deg]
+    heading_rates: [0.0]             # initial heading rate    [deg/s]
+    # three values are only needed for RamAirKite, for KPS3 and KPS4 use only the first value
+    l_tethers: [150.0]               # initial tether lengths      [m]
+    kite_distances: [51.0]           # initial kite distances     [m]
+    v_reel_outs: [0.0]               # initial reel out speeds   [m/s]
+    depowers: [25.0]                 # initial depower settings    [%]
+    steerings: [0.0]                 # initial steering settings   [%]
 
 solver:
     abs_tol: 0.0006        # absolute tolerance of the DAE solver [m, m/s]
diff --git a/docs/src/examples_4p.md b/docs/src/examples_4p.md
index 78ed166b..b6a658ab 100644
--- a/docs/src/examples_4p.md
+++ b/docs/src/examples_4p.md
@@ -30,7 +30,7 @@ Then we call the function `find_steady_state` which uses a non-linear solver to
 find_steady_state!(kps, prn=true)
 ```
 Finding the steady state of the 4-point model is difficult and it only works when we artificially reduce the stiffness by a factor
-of 0.035. In the function [`init_sim!`](@ref) this factor is slowly increased to 1.0.
+of 0.035. In the function [`init!`](@ref) this factor is slowly increased to 1.0.
 
 To plot the result in 2D we extract the vectors of the x and z coordinates of the tether particles with a for loop:
 ```julia
diff --git a/docs/src/functions.md b/docs/src/functions.md
index 0d34cda9..4be3c824 100644
--- a/docs/src/functions.md
+++ b/docs/src/functions.md
@@ -55,7 +55,7 @@ SysState
 
 ## High level simulation interface
 ```@docs
-init_sim!
+init!
 next_step!
 ```
 
diff --git a/docs/src/index.md b/docs/src/index.md
index 19ab607e..a92cdacf 100644
--- a/docs/src/index.md
+++ b/docs/src/index.md
@@ -83,7 +83,7 @@ times faster.
 - the documentation was improved
 
 ## Provides
-The types [`KPS3`](@ref), [`KPS4`](@ref) and [`SymbolicAWEModel`](@ref), representing the one point, the four point kite model and the ram air kite model, together with the high level simulation interface consisting of the functions [`init_sim!`](@ref) and [`next_step!`](@ref). Other kite models can be added inside or outside of this package by implementing the non-generic methods required for an AbstractKiteModel.
+The types [`KPS3`](@ref), [`KPS4`](@ref) and [`SymbolicAWEModel`](@ref), representing the one point, the four point kite model and the ram air kite model, together with the high level simulation interface consisting of the functions [`init!`](@ref) and [`next_step!`](@ref). Other kite models can be added inside or outside of this package by implementing the non-generic methods required for an AbstractKiteModel.
 
 Additional functions to provide inputs and outputs of the model on each time step. In particular the constructor [`SysState`](@ref) can be called once per time step to create a SysState struct for
 logging or for displaying the state in a viewer. For the KPS3 and KPS4 model, once per time step the [`residual!`](@ref) function is called as many times as needed to find the solution at the end
diff --git a/docs/src/tutorial_system_structure.md b/docs/src/tutorial_system_structure.md
index 396b661d..73993cd0 100644
--- a/docs/src/tutorial_system_structure.md
+++ b/docs/src/tutorial_system_structure.md
@@ -69,7 +69,7 @@ If the system looks good, we can easily model it, by first creating a [`Symbolic
 ```julia
 sam = SymbolicAWEModel(set, sys_struct)
 
-init_sim!(sam; remake=false)
+init!(sam; remake=false)
 for i in 1:80
     plot(sam, i/set.sample_freq)
     next_step!(sam)
diff --git a/examples/bench.jl b/examples/bench.jl
index 6a0e3ec1..58a1d835 100644
--- a/examples/bench.jl
+++ b/examples/bench.jl
@@ -34,7 +34,7 @@ function simulate(integrator, steps)
     iter / steps
 end
 
-integrator = KiteModels.init_sim!(kps4; delta=0, stiffness_factor=0.5, prn=STATISTIC)
+integrator = KiteModels.init!(kps4; delta=0, stiffness_factor=0.5, prn=STATISTIC)
 
 println("\nStarting simulation...")
 simulate(integrator, 100)
diff --git a/examples/bench_4p.jl b/examples/bench_4p.jl
index 94c53d1c..60806859 100644
--- a/examples/bench_4p.jl
+++ b/examples/bench_4p.jl
@@ -52,7 +52,7 @@ function simulate(integrator, steps, offset=0)
     iter / steps
 end
 
-integrator = KiteModels.init_sim!(kps4, delta=0, stiffness_factor=0.5, prn=STATISTIC)
+integrator = KiteModels.init!(kps4, delta=0, stiffness_factor=0.5, prn=STATISTIC)
 
 println("\nStarting simulation...")
 simulate(integrator, 100, 100)
diff --git a/examples/calc_spectrum.jl b/examples/calc_spectrum.jl
index 7216744e..03c51000 100644
--- a/examples/calc_spectrum.jl
+++ b/examples/calc_spectrum.jl
@@ -100,7 +100,7 @@ function sim_and_plot(set; depower=DEPOWER, f_ex)
     set.elevation = 67.0
     kcu::KCU = KCU(set)
     kps4::KPS4 = KPS4(kcu)
-    integrator = KiteModels.init_sim!(kps4; delta=0.001*0, stiffness_factor=1, prn=STATISTIC)
+    integrator = KiteModels.init!(kps4; delta=0.001*0, stiffness_factor=1, prn=STATISTIC)
     set_depower_steering(kps4.kcu, depower, 0.0)
     simulate(kps4, integrator, logger, STEPS, f_ex)
     save_log(logger, "tmp")
diff --git a/examples/compare_kps3_kps4.jl b/examples/compare_kps3_kps4.jl
index e147da6f..6c942e2c 100644
--- a/examples/compare_kps3_kps4.jl
+++ b/examples/compare_kps3_kps4.jl
@@ -55,7 +55,7 @@ function simulate(s, integrator, steps, plot=false; fig="")
     iter / steps
 end
 
-integrator = KiteModels.init_sim!(kps3, delta=0.001, stiffness_factor=0.5, prn=STATISTIC)
+integrator = KiteModels.init!(kps3, delta=0.001, stiffness_factor=0.5, prn=STATISTIC)
 av_steps = simulate(kps3, integrator, STEPS, true; fig="kps3")
 
 lift, drag = KiteModels.lift_drag(kps3)
@@ -65,7 +65,7 @@ println("winch_force [N]: $(round(winch_force(kps3), digits=2))")
 println("Average number of callbacks per time step: $(round(av_steps, digits=2))")
 
 kps4.set.alpha_zero = ALPHA_ZERO
-integrator = KiteModels.init_sim!(kps4; delta=0.001, stiffness_factor=1, prn=STATISTIC)
+integrator = KiteModels.init!(kps4; delta=0.001, stiffness_factor=1, prn=STATISTIC)
 av_steps = simulate(kps4, integrator, STEPS, true; fig="kps4")
 
 lift, drag = KiteModels.lift_drag(kps4)
diff --git a/examples/initial_reel_out_4p.jl b/examples/initial_reel_out_4p.jl
index 22dbd1d4..60cbbe74 100644
--- a/examples/initial_reel_out_4p.jl
+++ b/examples/initial_reel_out_4p.jl
@@ -69,7 +69,7 @@ function simulate(integrator, steps, plot=false)
     iter / steps
 end
 
-integrator = KiteModels.init_sim!(kps4; delta=0.000, stiffness_factor=0.25, prn=STATISTIC)
+integrator = KiteModels.init!(kps4; delta=0.000, stiffness_factor=0.25, prn=STATISTIC)
 kps4.sync_speed = set.v_reel_out
 
 if PLOT
diff --git a/examples/initial_reel_out_4p_torque_control.jl b/examples/initial_reel_out_4p_torque_control.jl
index 7749acea..16aa231e 100644
--- a/examples/initial_reel_out_4p_torque_control.jl
+++ b/examples/initial_reel_out_4p_torque_control.jl
@@ -89,7 +89,7 @@ end
 
 kps4.sync_speed = set.v_reel_out
 kps4.wm.last_set_speed = set.v_reel_out
-integrator = KiteModels.init_sim!(kps4; delta=0.00015, stiffness_factor=0.8, prn=STATISTIC)
+integrator = KiteModels.init!(kps4; delta=0.00015, stiffness_factor=0.8, prn=STATISTIC)
 
 if PLOT
     av_steps = simulate(integrator, STEPS, true)
diff --git a/examples/lin_ram_model.jl b/examples/lin_ram_model.jl
index 0bfcaa3f..0b844462 100644
--- a/examples/lin_ram_model.jl
+++ b/examples/lin_ram_model.jl
@@ -61,7 +61,7 @@ lin_outputs = @variables heading(t_nounits)[1]
 # Initialize at elevation with linearization outputs
 s.sys_struct.winches[2].tether_length += 0.2
 s.sys_struct.winches[3].tether_length += 0.2
-KiteModels.init_sim!(s; 
+KiteModels.init!(s; 
     remake=false,
     reload=true,
     lin_outputs  # Specify which outputs to track in linear model
diff --git a/examples/plot_alpha2.jl b/examples/plot_alpha2.jl
index d02d45ab..95abae62 100644
--- a/examples/plot_alpha2.jl
+++ b/examples/plot_alpha2.jl
@@ -57,7 +57,7 @@ function simulate(integrator, steps, offset=0)
     iter / steps
 end
 
-integrator = KiteModels.init_sim!(kps4, stiffness_factor=0.5, prn=STATISTIC)
+integrator = KiteModels.init!(kps4, stiffness_factor=0.5, prn=STATISTIC)
 
 println("\nStarting simulation...")
 simulate(integrator, 100, 100)
diff --git a/examples/plot_cl_cd.jl b/examples/plot_cl_cd.jl
index 0c489e08..c3451d53 100644
--- a/examples/plot_cl_cd.jl
+++ b/examples/plot_cl_cd.jl
@@ -97,7 +97,7 @@ for depower in DEPOWER
 
     kcu = KCU(set)
     kps4 = KPS4(kcu)
-    integrator = KiteModels.init_sim!(kps4; delta=0.03, stiffness_factor=0.05, prn=STATISTIC)
+    integrator = KiteModels.init!(kps4; delta=0.03, stiffness_factor=0.05, prn=STATISTIC)
     if ! isnothing(integrator)
         try
             cl, cd = simulate(kps4, integrator, logger, STEPS)
diff --git a/examples/plot_parking_test.jl b/examples/plot_parking_test.jl
index af0a95b9..62d3de4d 100644
--- a/examples/plot_parking_test.jl
+++ b/examples/plot_parking_test.jl
@@ -115,7 +115,7 @@ for depower in DEPOWER
     kps4::KPS4 = KPS4(kcu)
     set.elevation += 5
     set.v_wind = V_WIND_200[i] / 1.348881340489221 * calc_wind_factor(kps4.am, HEIGHT[i])/1.348881340489221
-    integrator = KiteModels.init_sim!(kps4; delta=0.001*0, stiffness_factor=1, prn=STATISTIC)
+    integrator = KiteModels.init!(kps4; delta=0.001*0, stiffness_factor=1, prn=STATISTIC)
     if ! isnothing(integrator)
         try
             cl, cd = simulate(kps4, integrator, logger, STEPS)
diff --git a/examples/plot_pitch_stability.jl b/examples/plot_pitch_stability.jl
index e946035a..05a8d2ec 100644
--- a/examples/plot_pitch_stability.jl
+++ b/examples/plot_pitch_stability.jl
@@ -110,7 +110,7 @@ kcu::KCU = KCU(set)
 kps4::KPS4 = KPS4(kcu)
 set.elevation += 5
 set.v_wind = V_WIND_200
-integrator = KiteModels.init_sim!(kps4; delta=0.001*0, stiffness_factor=1, prn=STATISTIC)
+integrator = KiteModels.init!(kps4; delta=0.001*0, stiffness_factor=1, prn=STATISTIC)
 if ! isnothing(integrator)
     simulate(kps4, integrator, logger, STEPS)
     set_depower_steering(kps4.kcu, depower, 0.0)
diff --git a/examples/plot_side_cl.jl b/examples/plot_side_cl.jl
index 7b42f20f..5583e52f 100644
--- a/examples/plot_side_cl.jl
+++ b/examples/plot_side_cl.jl
@@ -81,10 +81,10 @@ STEERING = zeros(length(SET_STEERING))
 SIDE_CL  = zeros(length(SET_STEERING))
 for (i, set_steering) in pairs(SET_STEERING)
     local side_cl, integrator
-    integrator = KiteModels.init_sim!(kps4;  delta=0.001, stiffness_factor=1, prn=STATISTIC)
+    integrator = KiteModels.init!(kps4;  delta=0.001, stiffness_factor=1, prn=STATISTIC)
     side_cl, steering = simulate(integrator, STEPS, set_steering, plot=false)
     if side_cl == 0.0
-        integrator = KiteModels.init_sim!(kps4;  delta=0.001, stiffness_factor=1, prn=STATISTIC)
+        integrator = KiteModels.init!(kps4;  delta=0.001, stiffness_factor=1, prn=STATISTIC)
         side_cl, steering = simulate(integrator, STEPS, set_steering, plot=false)
     end
     SIDE_CL[i] = side_cl
diff --git a/examples/ram_air_kite.jl b/examples/ram_air_kite.jl
index 5a79e266..5ad10857 100644
--- a/examples/ram_air_kite.jl
+++ b/examples/ram_air_kite.jl
@@ -49,7 +49,7 @@ toc()
 # Initialize at elevation
 set.l_tethers[2] += 0.2
 set.l_tethers[3] += 0.2
-init_sim!(sam; remake=false, reload=false)
+init!(sam; remake=false, reload=false)
 sys = sam.sys
 
 @info "System initialized at:"
diff --git a/examples/reel_out_1p.jl b/examples/reel_out_1p.jl
index ec72d268..271ce53f 100644
--- a/examples/reel_out_1p.jl
+++ b/examples/reel_out_1p.jl
@@ -61,7 +61,7 @@ function simulate(integrator, steps, plot=false)
     iter / steps
 end
 
-integrator = KiteModels.init_sim!(kps3, delta=0, stiffness_factor=0.04, prn=STATISTIC)
+integrator = KiteModels.init!(kps3, delta=0, stiffness_factor=0.04, prn=STATISTIC)
 kps3.sync_speed = 0.0
 
 if PLOT
diff --git a/examples/reel_out_4p.jl b/examples/reel_out_4p.jl
index 7b52fc8c..b97755ce 100644
--- a/examples/reel_out_4p.jl
+++ b/examples/reel_out_4p.jl
@@ -66,7 +66,7 @@ function simulate(integrator, steps, plot=false)
     iter / steps
 end
 
-integrator = KiteModels.init_sim!(kps4; delta=0, stiffness_factor=1, prn=STATISTIC)
+integrator = KiteModels.init!(kps4; delta=0, stiffness_factor=1, prn=STATISTIC)
 kps4.sync_speed = 0.0
 
 if PLOT
diff --git a/examples/reel_out_4p_torque_control.jl b/examples/reel_out_4p_torque_control.jl
index 7fbe997a..3c660f1a 100644
--- a/examples/reel_out_4p_torque_control.jl
+++ b/examples/reel_out_4p_torque_control.jl
@@ -70,7 +70,7 @@ function simulate(integrator, steps, plot=false)
     iter / steps
 end
 
-integrator = KiteModels.init_sim!(kps4; delta=0, stiffness_factor=1, prn=STATISTIC)
+integrator = KiteModels.init!(kps4; delta=0, stiffness_factor=1, prn=STATISTIC)
 kps4.sync_speed = 0.0
 
 if PLOT
diff --git a/examples/simulate_simple.jl b/examples/simulate_simple.jl
index fc6e939e..51161628 100644
--- a/examples/simulate_simple.jl
+++ b/examples/simulate_simple.jl
@@ -62,8 +62,8 @@ function simulate(integrator, steps, plot=false)
     end
     iter / steps
 end
-
-integrator = KiteModels.init_sim!(kps4;  delta=0.0, stiffness_factor=1, upwind_dir=UPWIND_DIR, prn=STATISTIC)
+kps4.set.upwind_dir = rad2deg(UPWIND_DIR)
+integrator = KiteModels.init!(kps4;  delta=0.0, stiffness_factor=1, prn=STATISTIC)
 
 if PLOT
     global flight_log
diff --git a/examples/simulate_steering.jl b/examples/simulate_steering.jl
index 5362814c..7aa6983c 100644
--- a/examples/simulate_steering.jl
+++ b/examples/simulate_steering.jl
@@ -64,7 +64,7 @@ function simulate(integrator, steps, plot=false)
     iter / steps
 end
 
-integrator = KiteModels.init_sim!(kps3; delta=0, stiffness_factor=0.04, prn=STATISTIC)
+integrator = KiteModels.init!(kps3; delta=0, stiffness_factor=0.04, prn=STATISTIC)
 
 if PLOT
     av_steps = simulate(integrator, STEPS, true)
diff --git a/examples/steering_test_1p.jl b/examples/steering_test_1p.jl
index f9698301..beb81ecd 100644
--- a/examples/steering_test_1p.jl
+++ b/examples/steering_test_1p.jl
@@ -99,7 +99,7 @@ function simulate(integrator, steps; plot=false)
     end
 end
 
-integrator = KiteModels.init_sim!(kps3;  delta=0.0, stiffness_factor=1, prn=STATISTIC)
+integrator = KiteModels.init!(kps3;  delta=0.0, stiffness_factor=1, prn=STATISTIC)
 simulate(integrator, STEPS; plot=true)
 
 function delay(x, y, t_max = 10)
diff --git a/examples/steering_test_4p.jl b/examples/steering_test_4p.jl
index 9d74a1ed..78a922ca 100644
--- a/examples/steering_test_4p.jl
+++ b/examples/steering_test_4p.jl
@@ -104,7 +104,7 @@ function simulate(integrator, steps; plot=false)
 end
 
 
-integrator = KiteModels.init_sim!(kps4;  delta=0.0, stiffness_factor=1, prn=STATISTIC)
+integrator = KiteModels.init!(kps4;  delta=0.0, stiffness_factor=1, prn=STATISTIC)
 simulate(integrator, STEPS; plot=true)
 
 function delay(x, y, t_max = 10)
diff --git a/examples/test_init_1p.jl b/examples/test_init_1p.jl
index 266a216b..f10f661a 100644
--- a/examples/test_init_1p.jl
+++ b/examples/test_init_1p.jl
@@ -38,7 +38,7 @@ logger = Logger(set.segments + 1, STEPS)
 
 kcu::KCU = KCU(set)
 kps3::KPS3 = KPS3(kcu)
-integrator = KiteModels.init_sim!(kps3; delta=0.03, stiffness_factor=0.1, prn=STATISTIC)
+integrator = KiteModels.init!(kps3; delta=0.03, stiffness_factor=0.1, prn=STATISTIC)
 lift, drag = lift_drag(kps3)
 sys_state = KiteModels.SysState(kps3)
 log!(logger, sys_state)
diff --git a/examples/test_init_4p.jl b/examples/test_init_4p.jl
index 44546192..e1c06fe0 100644
--- a/examples/test_init_4p.jl
+++ b/examples/test_init_4p.jl
@@ -39,7 +39,7 @@ logger = Logger(set.segments + 5, STEPS)
 
 kcu::KCU = KCU(set)
 kps4::KPS4 = KPS4(kcu)
-integrator = KiteModels.init_sim!(kps4; delta=0.03, stiffness_factor=0.01, upwind_dir=UPWIND_DIR, prn=STATISTIC)
+integrator = KiteModels.init!(kps4; delta=0.03, stiffness_factor=0.01, upwind_dir=UPWIND_DIR, prn=STATISTIC)
 for i=1:80
     next_step!(kps4, integrator; set_speed=kps4.set.v_reel_out, dt)
 end
diff --git a/examples/test_steady_state.jl b/examples/test_steady_state.jl
index e7465b4a..af78aac1 100644
--- a/examples/test_steady_state.jl
+++ b/examples/test_steady_state.jl
@@ -12,7 +12,7 @@ kps4::KPS4 = KPS4(kcu)
 
 clear!(kps4)
 KiteModels.set_depower_steering!(kps4, kps4.set.depower_offset/100.0, 0.0)
-@time KiteModels.init_sim!(kps4; delta=0.001, stiffness_factor=0.5, prn=false)
+@time KiteModels.init!(kps4; delta=0.001, stiffness_factor=0.5, prn=false)
 
 println("\nlift, drag    [N]  : $(KiteModels.lift_drag(kps4))")
 println("\nSpring forces:")
diff --git a/examples/tether.jl b/examples/tether.jl
index e1983659..f74eaef6 100644
--- a/examples/tether.jl
+++ b/examples/tether.jl
@@ -30,7 +30,7 @@ plot(sys_struct, 0.0)
 
 sam = SymbolicAWEModel(set, sys_struct)
 
-init_sim!(sam; remake=false)
+init!(sam; remake=false)
 for i in 1:80
     plot(sam, i/set.sample_freq)
     next_step!(sam)
diff --git a/examples_3d/parking_4p.jl b/examples_3d/parking_4p.jl
index 7c4de90e..e61ea333 100644
--- a/examples_3d/parking_4p.jl
+++ b/examples_3d/parking_4p.jl
@@ -85,7 +85,7 @@ function simulate(integrator, steps, plot=PLOT)
     iter / steps
 end
 
-integrator = KiteModels.init_sim!(kps4, delta=0, stiffness_factor=0.5, prn=STATISTIC)
+integrator = KiteModels.init!(kps4, delta=0, stiffness_factor=0.5, prn=STATISTIC)
 
 println("\nStarting simulation...")
 simulate(integrator, STEPS)
diff --git a/mwes/mwe_01.jl b/mwes/mwe_01.jl
index e1b24c96..8e38aa9e 100644
--- a/mwes/mwe_01.jl
+++ b/mwes/mwe_01.jl
@@ -6,5 +6,5 @@ using KiteModels
 
 kps4::KPS4 = KPS4(KCU(se()))
 
-integrator = KiteModels.init_sim!(kps4; stiffness_factor=0.035, prn=false)
+integrator = KiteModels.init!(kps4; stiffness_factor=0.035, prn=false)
 nothing
\ No newline at end of file
diff --git a/mwes/mwe_02.jl b/mwes/mwe_02.jl
index aef1e1cd..5a9882ab 100644
--- a/mwes/mwe_02.jl
+++ b/mwes/mwe_02.jl
@@ -11,7 +11,7 @@ set.solver="DFBDF"
 kps4::KPS4 = KPS4(KCU(set))
 STEPS = 200
 
-integrator = KiteModels.init_sim!(kps4; stiffness_factor=0.035, prn=false)
+integrator = KiteModels.init!(kps4; stiffness_factor=0.035, prn=false)
 next_step!(kps4, integrator, set_speed = 0, dt=0.05)
 @timev next_step!(kps4, integrator; set_speed = 0, dt=0.05)
 function nsteps(kps4, integrator)
diff --git a/mwes/mwe_10.jl b/mwes/mwe_10.jl
index df16f645..17a9b0cb 100644
--- a/mwes/mwe_10.jl
+++ b/mwes/mwe_10.jl
@@ -6,5 +6,5 @@ using KiteModels
 
 kps4_3L::SymbolicAWEModel = SymbolicAWEModel(KCU(se()))
 
-integrator = KiteModels.init_sim!(kps4_3L; stiffness_factor=0.035, prn=false)
+integrator = KiteModels.init!(kps4_3L; stiffness_factor=0.035, prn=false)
 nothing
\ No newline at end of file
diff --git a/mwes/mwe_11.jl b/mwes/mwe_11.jl
index 5af0c520..0ec1420e 100644
--- a/mwes/mwe_11.jl
+++ b/mwes/mwe_11.jl
@@ -15,5 +15,5 @@ kps3::KPS3 = KPS3(kcu)
 
 
 reltime = 0.0
-integrator = KiteModels.init_sim!(kps3, stiffness_factor=0.04)
+integrator = KiteModels.init!(kps3, stiffness_factor=0.04)
 plot2d(kps3.pos, reltime; zoom=false, front=false, segments=set.segments)
\ No newline at end of file
diff --git a/mwes/mwe_11b.jl b/mwes/mwe_11b.jl
index 02de68e9..836d246c 100644
--- a/mwes/mwe_11b.jl
+++ b/mwes/mwe_11b.jl
@@ -14,5 +14,5 @@ kcu::KCU = KCU(set)
 kps4::KPS4 = KPS4(kcu)
 
 reltime = 0.0
-integrator = KiteModels.init_sim!(kps4, stiffness_factor=0.5)
+integrator = KiteModels.init!(kps4, stiffness_factor=0.5)
 plot2d(kps4.pos, reltime; zoom=true, front=false, segments=set.segments)
\ No newline at end of file
diff --git a/mwes/mwe_12.jl b/mwes/mwe_12.jl
index 2cae0895..14860087 100644
--- a/mwes/mwe_12.jl
+++ b/mwes/mwe_12.jl
@@ -15,5 +15,5 @@ kcu::KCU = KCU(set)
 kps3::KPS3 = KPS3(kcu)
 
 reltime = 0.0
-integrator = KiteModels.init_sim!(kps3, stiffness_factor=0.04)
+integrator = KiteModels.init!(kps3, stiffness_factor=0.04)
 plot2d(kps3.pos, reltime; zoom=false, front=false, segments=set.segments)
\ No newline at end of file
diff --git a/mwes/mwe_12b.jl b/mwes/mwe_12b.jl
index b17bf331..93991bb0 100644
--- a/mwes/mwe_12b.jl
+++ b/mwes/mwe_12b.jl
@@ -15,7 +15,7 @@ kcu::KCU = KCU(set)
 kps4::KPS4 = KPS4(kcu)
 
 reltime = 0.0
-integrator = KiteModels.init_sim!(kps4, stiffness_factor=0.5)
+integrator = KiteModels.init!(kps4, stiffness_factor=0.5)
 
 lines, sc, txt = nothing, nothing, nothing
 plot2d(kps4.pos, reltime; zoom=true, front=false, segments=set.segments, lines, sc, txt)
diff --git a/mwes/mwe_26.jl b/mwes/mwe_26.jl
index a975fd8d..1c5c6414 100644
--- a/mwes/mwe_26.jl
+++ b/mwes/mwe_26.jl
@@ -13,7 +13,7 @@ set.v_wind = 50
 kps4::KPS4 = KPS4(KCU(set))
 STEPS = 200
 
-integrator = KiteModels.init_sim!(kps4; stiffness_factor=0.5, prn=false)
+integrator = KiteModels.init!(kps4; stiffness_factor=0.5, prn=false)
 
 next_step!(kps4, integrator, set_speed = 0, dt=0.05)
 function nsteps(kps4, integrator)
diff --git a/mwes/mwe_27.jl b/mwes/mwe_27.jl
index 399e4d4e..daa4f292 100644
--- a/mwes/mwe_27.jl
+++ b/mwes/mwe_27.jl
@@ -5,4 +5,4 @@ using KiteModels
 
 set = load_settings("system_ram.yaml")
 sam = SymbolicAWEModel(set)
-KiteModels.init_sim!(sam; remake=false, reload=false)
\ No newline at end of file
+KiteModels.init!(sam; remake=false, reload=false)
\ No newline at end of file
diff --git a/src/KPS3.jl b/src/KPS3.jl
index 4abe7c94..c7405418 100644
--- a/src/KPS3.jl
+++ b/src/KPS3.jl
@@ -36,7 +36,7 @@ $(TYPEDFIELDS)
     "Reference to winch model as implemented in the package WinchModels"
     wm::Union{AbstractWinchModel, Nothing} = nothing
     "Integrator, storing the current state"
-    integrator::Union{OrdinaryDiffEqCore.ODEIntegrator, Nothing} = nothing
+    integrator::Union{OrdinaryDiffEqCore.ODEIntegrator, Sundials.IDAIntegrator, Nothing} = nothing
     "Iterations, number of calls to the function residual!"
     iter:: Int64 = 0
     "Function for calculation the lift coefficent, using a spline based on the provided value pairs."
diff --git a/src/KPS4.jl b/src/KPS4.jl
index 88df5603..9918e4b1 100644
--- a/src/KPS4.jl
+++ b/src/KPS4.jl
@@ -69,7 +69,7 @@ $(TYPEDFIELDS)
     "Reference to winch model as implemented in the package WinchModels"
     wm::AbstractWinchModel
     "Integrator, storing the current state"
-    integrator::Union{OrdinaryDiffEqCore.ODEIntegrator, Nothing} = nothing
+    integrator::Union{OrdinaryDiffEqCore.ODEIntegrator, Sundials.IDAIntegrator, Nothing} = nothing
     "Iterations, number of calls to the function residual!"
     iter:: Int64 = 0
     "Function for calculation the lift coefficient, using a spline based on the provided value pairs."
diff --git a/src/KiteModels.jl b/src/KiteModels.jl
index b3f2a452..ae639a06 100644
--- a/src/KiteModels.jl
+++ b/src/KiteModels.jl
@@ -37,9 +37,9 @@ using ADTypes: AutoFiniteDiff
 import ModelingToolkit.SciMLBase: successful_retcode
 
 export KPS3, KPS4, SymbolicAWEModel, KVec3, SimFloat, ProfileLaw, EXP, LOG, EXPLOG     # constants and types
-export calc_set_cl_cd!, copy_examples, copy_bin, update_sys_state!                            # helper functions
-export clear!, find_steady_state!, residual!                                                  # low level workers
-export init_sim!, init!, reinit!, next_step!, init_pos_vel                                    # high level workers
+export calc_set_cl_cd!, copy_examples, copy_bin, update_sys_state!                     # helper functions
+export clear!, find_steady_state!, residual!                                           # low level workers
+export init!, reinit!, next_step!, init_pos_vel                                        # high level workers
 export pos_kite, calc_height, calc_elevation, calc_azimuth, calc_heading, calc_course, calc_orient_quat, calc_aoa  # getters
 export calc_azimuth_north, calc_azimuth_east
 export winch_force, lift_drag, cl_cd, lift_over_drag, unstretched_length, tether_length, v_wind_kite     # getters
@@ -538,7 +538,7 @@ function calc_pre_tension(s::AKM)
 end
 
 """
-    init_sim!(s::AKM; stiffness_factor=0.5, delta=0.0001, upwind_dir=-pi/2, 
+    init!(s::AKM; stiffness_factor=0.5, delta=0.0001,
                       prn=false) -> OrdinaryDiffEqCore.ODEIntegrator
 
 Initializes the integrator of the model (KPS3 and KPS4 only).
@@ -547,15 +547,14 @@ Parameters:
 - s:     an instance of an abstract kite model
 - stiffness_factor: factor applied to the tether stiffness during initialization
 - delta: initial stretch of the tether during the steady state calculation
-- upwind_dir: upwind direction in radians, the direction the wind is coming from. Zero is at north; 
-              clockwise positive. Default: -pi/2, wind from west.
 - prn: if set to true, print the detailed solver results
 
 Returns:
 An instance of an `ODEIntegrator`.
 """
-function init_sim!(s::AKM; stiffness_factor=0.5, delta=0.0001, upwind_dir=-pi/2, prn=false)
+function init!(s::AKM; stiffness_factor=0.5, delta=0.0001, prn=false)
     clear!(s)
+    upwind_dir = deg2rad(s.set.upwind_dir)
     s.stiffness_factor = stiffness_factor
     
     try
@@ -563,7 +562,7 @@ function init_sim!(s::AKM; stiffness_factor=0.5, delta=0.0001, upwind_dir=-pi/2,
     catch e
         if e isa AssertionError
             println("ERROR: Failure to find initial steady state in find_steady_state! function!\n"*
-                    "Try to increase the delta parameter or to decrease the initial_stiffness of the init_sim! function.")
+                    "Try to increase the delta parameter or to decrease the initial_stiffness of the init! function.")
             return nothing
         else
             rethrow(e)
@@ -598,7 +597,7 @@ function init_sim!(s::AKM; stiffness_factor=0.5, delta=0.0001, upwind_dir=-pi/2,
         set_initial_velocity!(s)
     end
     s.v_reel_out = s.set.v_reel_out
-    return integrator
+    s.integrator = integrator
 end
 
 
@@ -610,7 +609,7 @@ Calculates the next simulation step. Either `set_speed` or `set_torque` must be
 
 Parameters:
 - s:            an instance of an abstract kite model
-- integrator:   an integrator instance as returned by the function [`init_sim!`](@ref)
+- integrator:   an integrator instance as returned by the function [`init!`](@ref)
 - set_speed:         set value of reel out speed in m/s or nothing
 - set_torque:   set value of the torque in Nm or nothing
 - set_force:    set value of the force in N or nothing (only for logging, not used otherwise)
diff --git a/src/precompile.jl b/src/precompile.jl
index f7d58509..e716be33 100644
--- a/src/precompile.jl
+++ b/src/precompile.jl
@@ -49,8 +49,8 @@ end
     @compile_workload begin
         # all calls in this block will be precompiled, regardless of whether(
         # they belong to your package or not (on Julia 1.8 and higher)
-        integrator = KiteModels.init_sim!(kps3_; stiffness_factor=0.035, prn=false)
-        integrator = KiteModels.init_sim!(kps4_; delta=0.03, stiffness_factor=0.05, prn=false)
+        integrator = KiteModels.init!(kps3_; stiffness_factor=0.035, prn=false)
+        integrator = KiteModels.init!(kps4_; delta=0.03, stiffness_factor=0.05, prn=false)
 
         sam_set = load_settings("system_ram.yaml")
         sam_set.segments = 3
@@ -87,7 +87,7 @@ end
             s = SymbolicAWEModel(sam_set)
 
             # Initialize at elevation
-            KiteModels.init_sim!(s; prn=false, precompile=true)
+            KiteModels.init!(s; prn=false, precompile=true)
             @info "Copying $output_file to $model_file !"
             cp(output_file, model_file; force=true)
             find_steady_state!(s)
diff --git a/src/symbolic_awe_model.jl b/src/symbolic_awe_model.jl
index afea5f06..08b60488 100644
--- a/src/symbolic_awe_model.jl
+++ b/src/symbolic_awe_model.jl
@@ -113,7 +113,7 @@ The aerodynamic models provide forces and moments acting on wing components.
 - `vsm_solvers::Vector{<:VortexStepMethod.Solver}=VortexStepMethod.Solver[]`: VSM solvers for aerodynamic calculations
 
 # Returns
-- `SymbolicAWEModel`: Model ready for symbolic equation generation via [`init_sim!`](@ref)
+- `SymbolicAWEModel`: Model ready for symbolic equation generation via [`init!`](@ref)
 
 # Example
 ```julia
@@ -158,7 +158,7 @@ This convenience constructor creates a complete AWE model using default configur
 - `set::Settings`: Configuration parameters (see [KiteUtils.Settings](https://ufechner7.github.io/KiteUtils.jl/stable/types/#KiteUtils.Settings))
 
 # Returns
-- `SymbolicAWEModel`: Model ready for symbolic equation generation via [`init_sim!`](@ref)
+- `SymbolicAWEModel`: Model ready for symbolic equation generation via [`init!`](@ref)
 
 # Example
 ```julia
@@ -166,7 +166,7 @@ set = se()  # Load default settings
 model = SymbolicAWEModel(set)
 
 # Initialize and run simulation
-init_sim!(model)
+init!(model)
 for i in 1:1000
     next_step!(model)
 end
@@ -181,7 +181,7 @@ function SymbolicAWEModel(set::Settings)
 end
 
 function update_sys_state!(ss::SysState, s::SymbolicAWEModel, zoom=1.0)
-    isnothing(s.integrator) && error("run init_sim!(s) first")
+    isnothing(s.integrator) && error("run init!(s) first")
     ss.time = s.integrator.t # Use integrator time
 
     # Get the state vectors from the integrator
@@ -262,7 +262,7 @@ function SysState(s::SymbolicAWEModel, zoom=1.0)
 end
 
 """
-    init_sim!(s::SymbolicAWEModel; solver=nothing, adaptive=true, prn=true, 
+    init!(s::SymbolicAWEModel; solver=nothing, adaptive=true, prn=true, 
               precompile=false, remake=false, reload=false, 
               lin_outputs=Num[]) -> OrdinaryDiffEqCore.ODEIntegrator
 
@@ -288,6 +288,8 @@ and only update the state variables. Otherwise, it will create a new model from
 # Keyword arguments
 - `solver`: Solver algorithm to use. If `nothing`, defaults to `FBDF()` or `QNDF()` based on `s.set.solver`.
 - `adaptive::Bool=true`: Whether to use adaptive time stepping.
+- `stiffness_factor=nothing`: ignored, for backwards compatibility
+- `delta=nothing`: ignored, for backwards compatibility
 - `prn::Bool=true`: Whether to print progress information.
 - `precompile::Bool=false`: Whether to build problem for precompilation.
 - `remake::Bool=false`: If true, forces the system to be rebuilt, even if a serialized model exists.
@@ -297,8 +299,8 @@ and only update the state variables. Otherwise, it will create a new model from
 # Returns
 - `integrator::OrdinaryDiffEqCore.ODEIntegrator`: The initialized ODE integrator.
 """
-function init_sim!(s::SymbolicAWEModel; 
-    solver=nothing, adaptive=true, prn=true, 
+function init!(s::SymbolicAWEModel; 
+    solver=nothing, stiffness_factor = nothing, delta = nothing, adaptive=true, prn=true, 
     precompile=false, remake=false, reload=false, 
     lin_outputs=Num[]
 )
@@ -360,7 +362,7 @@ function init_sim!(s::SymbolicAWEModel;
 end
 
 function linearize(s::SymbolicAWEModel; set_values=s.get_set_values(s.integrator))
-    isnothing(s.lin_prob) && error("Run init_sim! with remake=true and lin_outputs=...")
+    isnothing(s.lin_prob) && error("Run init! with remake=true and lin_outputs=...")
     s.set_lin_vsm(s.lin_prob, s.get_vsm(s.integrator))
     s.set_lin_set_values(s.lin_prob, set_values)
     s.set_lin_unknowns(s.lin_prob, s.get_unknowns(s.integrator))
@@ -397,7 +399,7 @@ and only updates the state variables to match the current initial settings.
 - `Nothing`
 
 # Throws
-- `ArgumentError`: If no serialized problem exists (run `init_sim!` first)
+- `ArgumentError`: If no serialized problem exists (run `init!` first)
 """
 function reinit!(
     s::SymbolicAWEModel,
@@ -415,7 +417,7 @@ function reinit!(
     
     if isnothing(s.prob) || reload
         model_path = joinpath(KiteUtils.get_data_path(), get_model_name(s.set; precompile))
-        !ispath(model_path) && error("$model_path not found. Run init_sim!(s::SymbolicAWEModel) first.")
+        !ispath(model_path) && error("$model_path not found. Run init!(s::SymbolicAWEModel) first.")
         try
             s.serialized_model = deserialize(model_path)
         catch e
@@ -441,7 +443,7 @@ function reinit!(
                 adaptive, dt, abstol=s.set.abs_tol, reltol=s.set.rel_tol, save_on=false, save_everystep=false)
             !s.set.quasi_static && (length(s.unknowns_vec) != length(s.integrator.u)) &&
                 error("sam.integrator unknowns of length $(length(s.integrator.u)) should equal sam.unknowns_vec of length $(length(s.unknowns_vec)).
-                    Maybe you forgot to run init_sim!(model; remake=true)?")
+                    Maybe you forgot to run init!(model; remake=true)?")
         end
         prn && @info "Initialized integrator in $t seconds"
     end
diff --git a/test/create_xz_file.jl b/test/create_xz_file.jl
index 4575dd69..2911a08b 100644
--- a/test/create_xz_file.jl
+++ b/test/create_xz_file.jl
@@ -35,7 +35,7 @@ toc()
 # Initialize at elevation
 s.sys_struct.winches[2].tether_length += 0.2
 s.sys_struct.winches[3].tether_length += 0.2
-KiteModels.init_sim!(s; remake=false, reload=true)
+KiteModels.init!(s; remake=false, reload=true)
 sys = s.sys
 
 @info "System initialized at:"
diff --git a/test/test_for_precompile.jl b/test/test_for_precompile.jl
index b98b900e..b71269a9 100644
--- a/test/test_for_precompile.jl
+++ b/test/test_for_precompile.jl
@@ -98,7 +98,7 @@ let
         end
         (integrator.p.iter - start) / steps
     end
-    integrator = KiteModels.init_sim!(kps4, prn=STATISTIC)
+    integrator = KiteModels.init!(kps4, prn=STATISTIC)
     kps4.stiffness_factor = 0.04
     simulate(integrator, 100, true)
 end
@@ -112,7 +112,7 @@ if ! haskey(ENV, "NO_MTK")
     s = SymbolicAWEModel(sam_set)
 
     # Initialize at elevation
-    KiteModels.init_sim!(s; prn=false, precompile=true)
+    KiteModels.init!(s; prn=false, precompile=true)
     find_steady_state!(s)
     steps = Int(round(10 / 0.05))
     logger = Logger(length(s.sys_struct.points), steps)
diff --git a/test/test_interface.jl b/test/test_interface.jl
index 32c6fe83..bf78d62d 100644
--- a/test/test_interface.jl
+++ b/test/test_interface.jl
@@ -2,12 +2,15 @@
 # SPDX-License-Identifier: MIT
 
 using KiteModels, KiteUtils, Test
+# the following line is needed because VortexStepMethod also exports init!
+using KiteModels: init! 
 
-set = load_settings("system.yaml")
+# set_data_path("data") 
+set = deepcopy(load_settings("system.yaml"))
 kps3::KPS3 = KPS3(set)
 kps4::KPS4 = KPS4(set)
-set = load_settings("system_ram.yaml")
-sam::SymbolicAWEModel = SymbolicAWEModel(set)
+set_ram = deepcopy(load_settings("system_ram.yaml"))
+sam::SymbolicAWEModel = SymbolicAWEModel(set_ram)
 
 @testset "KPS3 constructor interface" begin
     @test kps3 isa KiteUtils.AbstractKiteModel
@@ -30,4 +33,25 @@ end
     @test sam.am isa AtmosphericModel
     @test sam.iter isa Int64
 end
-nothing
+
+@testset "KPS3 init! interface" begin
+    kps4.set.upwind_dir = rad2deg(-pi/2)
+    integ = init!(kps3; stiffness_factor=0.5, delta=0.0001, prn=false)
+    @test integ isa KiteModels.OrdinaryDiffEqCore.ODEIntegrator
+    @test kps3.integrator isa KiteModels.OrdinaryDiffEqCore.ODEIntegrator
+end
+
+@testset "KPS4 init! interface" begin
+    kps4.set.upwind_dir = rad2deg(-pi/2)
+    integ = init!(kps4; stiffness_factor=0.5, delta=0.0001, prn=false)
+    @test integ isa KiteModels.OrdinaryDiffEqCore.ODEIntegrator
+    @test kps4.integrator isa KiteModels.OrdinaryDiffEqCore.ODEIntegrator
+end
+
+@testset "SymbolicAWEModel init! interface" begin
+    sam.set.upwind_dir = rad2deg(-pi/2)
+    integ = init!(sam; stiffness_factor=0.5, delta=0.0001, prn=false)
+    @test integ isa KiteModels.OrdinaryDiffEqCore.ODEIntegrator
+    @test kps4.integrator isa KiteModels.OrdinaryDiffEqCore.ODEIntegrator
+end
+nothing
\ No newline at end of file
diff --git a/test/test_kps4.jl b/test/test_kps4.jl
index 904ff8de..42d90915 100644
--- a/test/test_kps4.jl
+++ b/test/test_kps4.jl
@@ -518,7 +518,7 @@ println("--> test_simulate")
     STEPS = 500
     kps4.set.depower = 23.6
     kps4.set.solver = "IDA"
-    integrator = KiteModels.init_sim!(kps4; stiffness_factor=0.5, prn=false)
+    integrator = KiteModels.init!(kps4; stiffness_factor=0.5, prn=false)
     # println("\nStarting simulation...")
     simulate(integrator, 100)
     av_steps = simulate(integrator, STEPS-100)
@@ -548,7 +548,7 @@ println("<-- finished test_simulate")
 
 @testset "Raptures" begin
     kps4_ = KPS4(KCU(set))
-    integrator = KiteModels.init_sim!(kps4_; stiffness_factor=0.035, prn=false)
+    integrator = KiteModels.init!(kps4_; stiffness_factor=0.035, prn=false)
     kps4_.set.version = 2
     kps4_.stiffness_factor = 3
     @test maximum(spring_forces(kps4_; prn=false)) > 9000
diff --git a/test/test_ram_air_kite.jl b/test/test_ram_air_kite.jl
index 6d84958c..a9bca9d8 100644
--- a/test/test_ram_air_kite.jl
+++ b/test/test_ram_air_kite.jl
@@ -27,8 +27,8 @@ const BUILD_SYS = true
     @info "Creating s:"
     @time s = SymbolicAWEModel(set)
 
-    s.set.abs_tol = 1e-2
-    s.set.rel_tol = 1e-2
+    s.set.abs_tol = 1e-4
+    s.set.rel_tol = 1e-4
 
     # Initialize at elevation
     set.elevation = 80.0
@@ -45,7 +45,7 @@ const BUILD_SYS = true
 
         # 1. First time initialization - should create new model
         @info "Testing initial init! (should create new model if it doesn't exist yet)..."
-        @time KiteModels.init_sim!(s; prn=true)
+        @time KiteModels.init!(s; prn=true)
 
         # Check that serialization worked
         @test isfile(model_path)
@@ -62,9 +62,9 @@ const BUILD_SYS = true
         first_integrator_ptr = objectid(s.integrator)
         first_sys_struct_ptr = objectid(s.sys_struct)
 
-        # 2. First init_sim! - should load from serialized file
-        @info "Testing first init_sim! (should load serialized file)..."
-        @time KiteModels.init_sim!(s; prn=true, reload=false)
+        # 2. First init! - should load from serialized file
+        @info "Testing first init! (should load serialized file)..."
+        @time KiteModels.init!(s; prn=true, reload=false)
         next_step!(s)
 
         # Check that it's a new integrator
@@ -73,9 +73,9 @@ const BUILD_SYS = true
         @test first_integrator_ptr != second_integrator_ptr
         @test first_sys_struct_ptr == second_sys_struct_ptr
 
-        # 3. Second init_sim! - should reuse existing integrator
-        @info "Testing second init_sim! (should reuse integrator)..."
-        @time KiteModels.init_sim!(s; prn=true, reload=false)
+        # 3. Second init! - should reuse existing integrator
+        @info "Testing second init! (should reuse integrator)..."
+        @time KiteModels.init!(s; prn=true, reload=false)
 
         # This should create a new point system but reuse the existing integrator
         third_integrator_ptr = objectid(s.integrator)
@@ -108,7 +108,7 @@ const BUILD_SYS = true
     end
 
     @testset "State Consistency" begin
-        KiteModels.init_sim!(s, prn=true, reload=false)
+        KiteModels.init!(s, prn=true, reload=false)
         sys_state_before = KiteModels.SysState(s)
         @test isapprox(norm(s.integrator[s.sys.Q_b_w]), 1.0, atol=TOL)
         @test isapprox(sys_state_before.elevation, deg2rad(set.elevation), atol=1e-2)
@@ -116,7 +116,7 @@ const BUILD_SYS = true
         # Change measurement and reinitialize
         old_elevation = set.elevation
         set.elevation = 85.0
-        KiteModels.init_sim!(s, prn=true, reload=false)
+        KiteModels.init!(s, prn=true, reload=false)
 
         # Get new state using SysState
         sys_state_after = KiteModels.SysState(s)
@@ -166,7 +166,7 @@ const BUILD_SYS = true
 
     function test_step(s, d_set_values=zeros(3); dt=0.05, steps=5)
         s.integrator.ps[s.sys.stabilize] = true
-        for i in 1:1÷dt
+        for i in 1:1÷0.1
             next_step!(s; dt, vsm_interval=1)
         end
         s.integrator.ps[s.sys.stabilize] = false
@@ -202,7 +202,7 @@ const BUILD_SYS = true
 
     @testset "Simulation Step with SysState" begin
         # Basic step and time advancement test
-        KiteModels.init_sim!(s; prn=true, reload=false)
+        KiteModels.init!(s; prn=true, reload=false)
         sys_state_before = KiteModels.SysState(s)
 
         # Run a simulation step with zero set values
@@ -226,7 +226,7 @@ const BUILD_SYS = true
             # Initialize at 60 degrees elevation
             set.elevation = 60.0
 
-            KiteModels.init_sim!(s; prn=true)
+            KiteModels.init!(s; prn=true)
 
             # Verify initial conditions using SysState
             sys_state_init = KiteModels.SysState(s)
@@ -254,35 +254,37 @@ const BUILD_SYS = true
             return diff
         end
 
-        @testset "Steering Response Using SysState" begin
-            # Initialize model at moderate elevation
-            set.elevation = 70.0
-            KiteModels.init_sim!(s; prn=true, reload=false)
-            test_step(s)
-            sys_state_initial = KiteModels.SysState(s)
-
-            # steering right
-            KiteModels.init_sim!(s; prn=true, reload=false)
-            test_step(s, [0, 10, -10]; steps=20)
-            sys_state_right = KiteModels.SysState(s)
-
-            # steering left
-            KiteModels.init_sim!(s; prn=true, reload=false)
-            test_step(s, [0, -10, 10]; steps=20)
-            sys_state_left = KiteModels.SysState(s)
-
-            # Check steering values
-            @info "Steering:" sys_state_right.steering sys_state_left.steering
-            @test sys_state_right.steering > 3.0
-            @test sys_state_left.steering < -3.0
-
-            # Check heading changes
-            right_heading_diff = angle_diff(sys_state_right.heading, sys_state_initial.heading)
-            @test right_heading_diff ≈ 0.9 atol=0.2
-            left_heading_diff = angle_diff(sys_state_left.heading, sys_state_initial.heading)
-            @test left_heading_diff ≈ -0.9 atol=0.2
+        if build_is_production_build
+            @testset "Steering Response Using SysState" begin
+                # Initialize model at moderate elevation
+                set.elevation = 70.0
+                KiteModels.init!(s; prn=true, reload=false)
+                test_step(s)
+                sys_state_initial = KiteModels.SysState(s)
+
+                # steering right
+                KiteModels.init!(s; prn=true, reload=false)
+                test_step(s, [0, 10, -10]; steps=20)
+                sys_state_right = KiteModels.SysState(s)
+
+                # steering left
+                KiteModels.init!(s; prn=true, reload=false)
+                test_step(s, [0, -10, 10]; steps=20)
+                sys_state_left = KiteModels.SysState(s)
+
+                # Check steering values
+                @info "Steering:" sys_state_right.steering sys_state_left.steering
+                @test sys_state_right.steering > 3.0
+                @test sys_state_left.steering < -3.0
+
+                # Check heading changes
+                right_heading_diff = angle_diff(sys_state_right.heading, sys_state_initial.heading)
+                @test right_heading_diff ≈ 0.9 atol=0.2
+                left_heading_diff = angle_diff(sys_state_left.heading, sys_state_initial.heading)
+                @test left_heading_diff ≈ -0.9 atol=0.2
+            end
+            test_plot(s)
         end
-        test_plot(s)
     end
 
     @testset "Just a tether, without winch or kite" begin
@@ -310,7 +312,7 @@ const BUILD_SYS = true
 
         sam = SymbolicAWEModel(set, sys_struct)
         sys = sam.sys
-        init_sim!(sam; remake=false)
+        KiteModels.init!(sam; remake=false)
         @test isapprox(sam.integrator[sam.sys.pos[:, end]], [8.682408883346524, 0.0, 0.7596123493895988], atol=1e-2)
         for i in 1:100
             next_step!(sam)
@@ -325,4 +327,4 @@ end
 # Restore original data path
 set_data_path(old_path)
 
-nothing
\ No newline at end of file
+nothing
diff --git a/test/test_sundials.jl b/test/test_sundials.jl
index 25306fb5..42d06236 100644
--- a/test/test_sundials.jl
+++ b/test/test_sundials.jl
@@ -16,7 +16,7 @@ const kps4 = KPS4{Float64, KVec3, 6+4+1}()
 function residual!(res, yd, y::MVector{S, Float64}, s::KPS4, time) where S
 end
 
-function init_sim!(t_end=1.0)
+function init!(t_end=1.0)
     y0 = MVector{62, Float64}([13.970413450119487, 0.0, 21.238692070636343, 27.65581376097752, 0.0, 42.66213714321849, 40.976226230518435, 0.0, 64.314401166278, 53.87184032029182, 0.0, 86.22231803750196, 66.28915240374937, 0.0, 108.4048292516046, 78.17713830204762, 0.0, 130.87545423106485, 79.56930502428155, 0.0, 135.70836376062155, 80.90383289255747, 0.0, 137.7696816741141, 80.60126812407692, 2.4016533873456325, 135.3023287520457, 80.60126812407692, -2.4016533873456325, 135.3023287520457, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 150.0, 0.0])
     yd0= MVector{62, Float64}([0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, -9.81, 0.0, 0.0, -9.81, 0.0, 0.0, -9.81, 0.0, 0.0, -9.81, 0.0, 0.0, -9.81, 0.0, 0.0, -9.81, 0.0, 0.0, -9.81, 0.0, 0.0, -9.81, 0.0, 0.0, -9.81, 0.0, 0.0, -9.81, 0.0, 0.0])
     differential_vars = ones(Bool, length(y0))
@@ -29,6 +29,6 @@ end
 
 @testset "test_simulate        " begin
     STEPS = 500
-    integrator = init_sim!()
+    integrator = init!()
 end
 nothing