[Eric@AMS]

Originally Posted by Penn999

Are you sure you dont know of any BMW's making over 750whp? Maybe you meant N54's? Because I have seen quite a few S54's than run about make about that(750whp), and some that are well above that. If not I can provide you with a couple links to videos, with dynos and actual in car runs. Guess what beginning of all of the videos are.....HPF!

Yes, as BrianMN stated, I meant N54's. I am aware of other BMW models making that power and over, but this discussion has clearly been on exhaust for the N54 and the misconception of HP numbers that you can make through a 3inch system. As stated in my prior post and the post by AR design, high horsepower numbers "are" achievable through a 3inch system. There are many vehicles out on the road to prove this. Even the OEM exhaust system found on N54's flows great for mild HP cars. BMW spent a lot of R&D making the exhaust for these vehicles. Now if you are looking to make over 750whp on the N54, yes I would highly recommend stepping up to a larger diameter piping. At this HP level, a 3inch system would be a restriction and not be able to move the airflow fast enough.

As far as HP numbers gained from any cat-back on the market, they are all low numbers. Throw a set of quality downpipes into the equation and a tune and you are looking at a nice gain of both HP and torque.

[Penn999]

Originally Posted by Eric@AMS

Yes, as BrianMN stated, I meant N54's. I am aware of other BMW models making that power and over, but this discussion has clearly been on exhaust for the N54 and the misconception of HP numbers that you can make through a 3inch system. As stated in my prior post and the post by AR design, high horsepower numbers "are" achievable through a 3inch system. There are many vehicles out on the road to prove this. Even the OEM exhaust system found on N54's flows great for mild HP cars. BMW spent a lot of R&D making the exhaust for these vehicles. Now if you are looking to make over 750whp on the N54, yes I would highly recommend stepping up to a larger diameter piping. At this HP level, a 3inch system would be a restriction and not be able to move the airflow fast enough.

As far as HP numbers gained from any cat-back on the market, they are all low numbers. Throw a set of quality downpipes into the equation and a tune and you are looking at a nice gain of both HP and torque.

I agree with you 100%, but I think that catalytic converters are much more of a restriction than the diameter of the piping. When it comes to aftermarket exhaust for the n54's, all of them are capable to handle well over what is available(the highest car I know if is making mid 500'swhp with nitrous) in terms of hp adders. Which is wellll below your 750whp claim that it will handle. So this diameter talk seems rather useless, currently. I hope AR and HPF push the issue...It really comes down to your liking of exhaust note and whether you want to go fully catless or partially.

[fl335i]

So I'm stuck on either the HKS or AMS. HKS is all certified up, and made in japan, flanged etc. the AMS is sick light and super well built with Vband clamps. Uh, I'm going to sleep on it.


3" single has area of 7.068 in^2

Dual 65mm has area of 10.286 in^2

That's about 45% more area of pipe. Proper way to put this issue to bed is do a fluid calc on it. each bend, coefficient of smoothness etc. I found a Dodge Diesel forum where an engineer actually did it for a 2.2L turbo 4cyl Dodge car. He calculated it to a nats arse. At 10psi, 85% VE, his specific exhaust bends etc with 3" pipe his calc gave him .4psi of back pressure at 6,500rpm. I need to find the calc formula and I can run it for our cars. Just can't stamp it.

[ar design]

PM me for a great deal on the AMS

[BrianMN]

Originally Posted by fl335i

So I'm stuck on either the HKS or AMS. HKS is all certified up, and made in japan, flanged etc. the AMS is sick light and super well built with Vband clamps. Uh, I'm going to sleep on it.


3" single has area of 7.068 in^2

Dual 65mm has area of 10.286 in^2

That's about 45% more area of pipe. Proper way to put this issue to bed is do a fluid calc on it. each bend, coefficient of smoothness etc. I found a Dodge Diesel forum where an engineer actually did it for a 2.2L turbo 4cyl Dodge car. He calculated it to a nats arse. At 10psi, 85% VE, his specific exhaust bends etc with 3" pipe his calc gave him .4psi of back pressure at 6,500rpm. I need to find the calc formula and I can run it for our cars. Just can't stamp it.

Seriously, compiling that data is a waste of time. If you're at the 450hp range, you will NOT get more HP from putting a HKS system on as opposed to putting an AMS system. If you're planning on going upwards of 800-1000hp, that'd be awesome! But if not, you should be making a decision on sound, weight and quality and absolutely NOT on percieved HP gains.

[Penn999]

Originally Posted by BrianMN

Seriously, compiling that data is a waste of time. If you're at the 450hp range, you will NOT get more HP from putting a HKS system on as opposed to putting an AMS system. If you're planning on going upwards of 800-1000hp, that'd be awesome! But if not, you should be making a decision on sound, weight and quality and absolutely NOT on percieved HP gains.

LOL, for sure. They were getting WAAAY to technical and theoretical when the decision should be based on a couple of simple variables. I would be more than happy to go over the physics of diameter area of a circle and how it relates to exhaust flow rates when someone cracks the 750whp mark, but until then....keep it simple.

[fl335i]

Well a single 3" is equal to running dual 2.11" Diameter pipe. Single 3.5"(90mm) would be equivilant to dual 2.5" pipe. And dual 65mm pipe is equivilant to a single 3.62" pipe.

[Eric@AMS]

Originally Posted by BrianMN

Seriously, compiling that data is a waste of time. If you're at the 450hp range, you will NOT get more HP from putting a HKS system on as opposed to putting an AMS system. If you're planning on going upwards of 800-1000hp, that'd be awesome! But if not, you should be making a decision on sound, weight and quality and absolutely NOT on percieved HP gains.

Originally Posted by Penn999

LOL, for sure. They were getting WAAAY to technical and theoretical when the decision should be based on a couple of simple variables. I would be more than happy to go over the physics of diameter area of a circle and how it relates to exhaust flow rates when someone cracks the 750whp mark, but until then....keep it simple.

[cocoturkey]

Originally Posted by Eric@AMS

hi Eric, what's the max whp for AMS's single 3" exhaust system?

[Eric@AMS]

Originally Posted by cocoturkey

hi Eric, what's the max whp for AMS's single 3" exhaust system?

I would not recommend going past 750whp with the AMS single 3inch cat-back system matted with catless downpipes on the N54.

[Penn999]

Originally Posted by Eric@AMS

I would not recommend going past 750whp with the AMS single 3inch cat-back system matted with catless downpipes on the N54.

LOL, did he just ask what has been posted 14,000 times in this thread?

[1BAD535]

so what size is the dual stock exhaust system, is it dual 2.25?