Tuning Engine Sound: The 'Thumper Cam' Effect

find out how hard it's going to thump he is honestly that's not as hard as you would think because if you look at exhaust opening right here this is the exhaust valve opening Evo the earlier you open the the valve the more energy is still left in the combustion chamber that energy will be used to make sound so the earlier you move this the louder it's going to thump but then the shape of this changes the tone if you make this shape really fast you'll have a high pitched tone you know like a tinny like a like a imagine a drum head so a guy's a drummer you have a really small if you slow it down you'll get more of a thump it'll be more of a black black imagine it's like a big bass drum instead of that then you have this area under the curve so we look at this overlap area here and this is the overlap area when we look at the overlap duration overlap area the more time these two are connected each other this is the only time your exhaust Port gets to talk back to your intake Port so the header is talking to the intake Port during this time the header however is not set up to be tuned at idle it's actually tuned usually around five six thousand RPM maybe 3 500 on them real long like a 32 inch header maybe a little higher with like a 28 inch header but in here the pressure wave isn't timed at idle to work in here so the more you increase this overlap area and the more you move this Evo the more you get the sound of the thumper so earlier exhaust valve opening with more overlap area this will cause misfire so if you want something that sounds low frequency really loud with a lot of lope to it you want this Evo moved earlier slower and then more overlap but notice that the one thing that I did talk about IVC the intake valve closing won't have anything to do with the sound so I can put that intake valve closing where you need for your street application increase the overlap area change the exhaust opening and I can tune the sound like you would with the stereo Without Really changing where you make Peak power or where you make Peak torque that's the thumper camshafts you know that they sound really cool they sound like they're a race cam but they drive pretty decent you know and how you can do that is by tailoring each of those valve events checking on that exhaust valve opening and the overlap but the IVC for the RPM that you're actually