Replace this line to Grenade line in IV WeaponInfo.xml

	<weapon type="GRENADE">
		<data slot="THROWN" firetype="PROJECTILE" damagetype="EXPLOSIVE" group="GRENADE" targetrange="75.0" clipsize="1" ammomax="10">
			<damage networkplayermod="2.0" networkpedmod="1.0"/>

			<aiming accuracy="1.0">
				<offset 				x="0.0" y="1.0" z="0.0"/>
				<crouchedoffset x="0.0" y="1.0" z="0.0"/>
			</aiming>

			<pickup regentime="360000" ammoonstreet="8"/>

			<controller>
				<rumble duration="50" intensity="0.1"/>
			</controller>

			<flags>
				<flag>THROWN</flag>
				<flag>CAN_AIM</flag>
				<flag>CAN_FREE_AIM</flag>
				<flag>ANIM_RELOAD</flag>
				<flag>ANIM_CROUCH_FIRE</flag>
				<flag>EXPLOSION_BASED_ON_IMPACT</flag>
				<flag>EXPLOSION_BASED_ON_EXPLOSION</flag>
				<flag>ADD_SMOKE_ON_EXPLOSION</flag>
				<flag>SILENCED</flag>
				<flag>KEEP_CAMERA_BEHIND</flag>
			</flags>

			<projectile type="FUSE" fusetime="4000">
				<explosion type="EPISODIC_3"/>
				<physics force="70" vehiclevelocity="10.0"/>
			</projectile>
		</data>

		<assets model="w_grenade">
			<anim group="grenade"/>
		</assets>
	</weapon>

Add this new line to IV explosionFx.dat in Effects folder.

EPISODIC_3		500.0		100.0		2.0		1.0		20.0		 150.0		-6.0		5.0		0.0030			0.0		1.5		exp_fireball		exp_fireball_air	5.0		10	30	0.2	30.0	0.9	GRENADE	0		1.0	0.5	0.1	250.0	100.0	2.5	2

If it doesn't work, replace EPISODIC_3 with GRENADE and Explosion Type in WeaponInfo to GRENADE.