Originally Posted by LarThaL
I agree that catless/tune will give 25-30 whp. That is not 55hp. However, how much will a 25-30hp gain on top of 414hp make in your actual performance?
Lets look at this.
Firstly, even a stock M3 is traction limited in its low speed performance. Even if your car has 1000hp, it won't get off the line any faster. The first place to spend your money for actual increased performance is to increase the traction of the car so you can get the existing power to the ground better. So, you already need to invest in bigger wheels and wider tires.
Okay...so you argue that you are not into the whole drag strip thing, and that this is a "track car". OK, so in that case, let's see actual track times of otherwise equal cars with the only difference being basic NA mods. ( I say basic, because you are already talking about $4-5k for a good full exhaust and tune...about half the cost of a supercharger) I am willing to bet that all other things being equal, a car with just 25 more hp won't get around a track any faster in a statistically consistent manner. Your extra 25hp may get you a car length or two for all those times you get to an abandoned airstrip and can run your straight up to 150mph.
I reassert my point. By all means, do the NA mods, but do them for the change in subjective feel. Don't look for any meaningful actual performance gain.
And I am not in the least discounting the whole subjective feel thing. In the end, the joy of driving comes from a variety of sensory inputs and speed capability is only one of those.
Just don't kid yourself about what you are actually accomplishing. Believe me, I have done it all in 30 years of playing with cars....carburators, intakes, headers, exhausts, superchargers, turbochargers, standard and custom flashes, bigger and better this and that, etc. etc, etc. If you want clear cut power that you can really feel and use, get a supercharger, do the proper associated mods and be done with it.
Spoken like a man with some experience. Reminds me of the 2011 Shelby GT500. 550 HP and wasn't any faster than the M3 in the quarter mile. Like mentioned above, there are quite a few other factors to consider in order to actually do anything with more power.
I would disagree with spending 4-5k on exhaust and tune however. BMW put a lot of research into the stock exhaust I have no doubt. Paying a several thousand dollar premium over a test pipe for what might net 5 more hp at most is probably not worth it for street and non-competitive track purposes. I would think 2k should get you test pipes installed tune and maybe pullies. Those 3 should be getting you more than 30whp at least from the dyno charts forum members have been posting.
*edit* That said if you are a baller, have several cars, and could care less about the cost then do whatever you want