Here is a dump for you when the grenade was thrown from the player:
Code:
Printing out entity #102 variable information...
(variable name = value (meaning))
pev_classname = 66683048 ("grenade")
pev_globalname = 0 ("")
pev_origin = Vector (-1437.0, -707.5, 228.0)
pev_oldorigin = Vector (0.0, 0.0, 0.0)
pev_velocity = Vector (-606.8, 138.8, -146.2) - Length 639.437 - Length2D 622.492
pev_basevelocity = Vector (0.0, 0.0, 0.0) - Length 0.000 - Length2D 0.000
pev_clbasevelocity = Vector (0.0, 0.0, 0.0) - Length 0.000 - Length2D 0.000
pev_movedir = Vector (0.0, 0.0, 0.0)
pev_angles = Vector (4.3, 167.1, 0.0)
pev_avelocity = Vector (0.0, 0.0, 0.0) - Length 0.000 - Length2D 0.000
pev_punchangle = Vector (0.0, 0.0, 0.0)
pev_v_angle = Vector (0.0, 0.0, 0.0)
pev_endpos = Vector (0.0, 0.0, 0.0)
pev_startpos = Vector (0.0, 0.0, 0.0)
pev_impacttime = 0.000
pev_starttime = 0.000
pev_fixangle = 0 (nothing)
pev_idealpitch = 0.000
pev_pitch_speed = 0.000
pev_ideal_yaw = 0.000
pev_yaw_speed = 0.000
pev_modelindex = 177
pev_model = 66686696 ("models/w_hegrenade.mdl")
pev_viewmodel = 0 ("")
pev_weaponmodel = 0 ("")
pev_absmin = Vector (-1438.0, -708.5, 227.0)
pev_absmax = Vector (-1436.0, -706.5, 229.0)
pev_mins = Vector (0.0, 0.0, 0.0)
pev_maxs = Vector (0.0, 0.0, 0.0)
pev_size = Vector (0.0, 0.0, 0.0)
pev_ltime = 0.000 (current time is 69.921)
pev_nextthink = 69.950 (current time is 69.921)
pev_movetype = 10 (MOVETYPE_BOUNCE)
pev_solid = 2 (SOLID_BBOX)
pev_skin = 0 ("")
pev_body = 0 ("")
pev_effects = 0 ()
pev_gravity = 0.550 (fraction /1 of normal)
pev_friction = 0.699
pev_light_level = 0
pev_sequence = 4 ("")
pev_gaitsequence = 1 ("")
pev_frame = 0.000 (position /255 of total in sequence)
pev_animtime = 69.850 (current time is 69.921)
pev_framerate = 1.000 (times normal speed)
pev_controller = {148969728, 148969728, 148969728, 148969728}
pev_blending = {148969728, 148969728}
pev_scale = 0.000
pev_rendermode = 0 (kRenderNormal)
pev_renderamt = 0.000
pev_rendercolor = Vector (0.0, 0.0, 0.0) (RGB)
pev_renderfx = 0 (kRenderFxNone)
pev_health = 0.000
pev_frags = 0.000
pev_weapons = 0 (00000000000000000000000000000000)
pev_takedamage = 0.0 (DAMAGE_NO)
pev_deadflag = 0 (DEAD_NO)
pev_view_ofs = Vector (0.0, 0.0, 0.0)
pev_button = 0 ()
pev_impulse = 0
pev_chain = NULL
pev_dmg_inflictor = NULL
pev_enemy = NULL
pev_aiment = NULL
pev_owner = Entity #1 ("player")
pev_groundentity = Entity #0 ("worldspawn")
pev_spawnflags = 0 (00000000000000000000000000000000)
pev_flags = 0 ()
pev_colormap = 0 (0x0)
pev_team = 0
pev_max_health = 0.000
pev_teleport_time = 0.000
pev_armortype = 0.000
pev_armorvalue = 0.000
pev_waterlevel = 0 (not in water)
pev_watertype = -1
pev_target = 0 ("")
pev_targetname = 0 ("")
pev_netname = 0 ("")
pev_message = 0 ("")
pev_dmg_take = 0.000
pev_dmg_save = 0.000
pev_dmg = 100.000
pev_dmgtime = 70.550 (current time is 69.921)
pev_noise = 0 ("")
pev_noise1 = 0 ("")
pev_noise2 = 0 ("")
pev_noise3 = 0 ("")
pev_speed = 0.000
pev_air_finished = 0.000
pev_pain_finished = 0.000
pev_radsuit_finished = 0.000
pev_pContainingEntity = Entity #102 ("grenade")
pev_playerclass = 0
pev_maxspeed = 0.000
pev_fov = 0.000
pev_weaponanim = 0
pev_pushmsec = 0
pev_bInDuck = 0 (FALSE)
pev_flTimeStepSound = 0 (current time is 69.921)
pev_flSwimTime = 0 (current time is 69.921)
pev_flDuckTime = 0 (current time is 69.921)
pev_iStepLeft = 0
pev_flFallVelocity = 0.000
pev_gamestate = 0
pev_oldbuttons = 0 ()
pev_groupinfo = 0
pev_iuser1 = 0
pev_iuser2 = 0
pev_iuser3 = 0
pev_iuser4 = 0
pev_fuser1 = 0.000
pev_fuser2 = 0.000
pev_fuser3 = 0.000
pev_fuser4 = 0.000
pev_vuser1 = Vector (0.0, 0.0, 0.0)
pev_vuser2 = Vector (0.0, 0.0, 0.0)
pev_vuser3 = Vector (0.0, 0.0, 0.0)
pev_vuser4 = Vector (0.0, 0.0, 0.0)
pev_euser1 = NULL
pev_euser2 = NULL
pev_euser3 = NULL
pev_euser4 = NULL
End of dump.
Hope this helps

I think a key factor is this:
pev_dmgtime = 70.550 (current time is 69.921)
I did a few dumps and it seems like dmgtime is when it explodes.
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