horse power is defined by this equation:

T=torque N=RPM

The addition of forced induction only makes the engine more efficient. There is no magical power associated with it. Denser air needs more fuel = more powa.

If you increase either torque or rpm, more power will be made. The issue at higher rpm is the ability to efficiently fill the combustion chambers. FI obviously helps with this, as well as ITBs, intake upgrades, exhaust upgrades (combined with variable valve timing) to help with scavenging.

Also, by taking catalytic converters out, exhaust gas velocity increases through out the powerband. Because this restriction increases torque at low rpm, this causes a power loss. On the other hand though, the elimination of restriction -> higher velocity allows for more exhaust to be emptied out of the combustion chambers, resulting in power gain.

Many people misunderstand Tony's dyno images. (For good reason) Tony shows the gains over test pipes first, showing massive low end gains. How ever, the addition of helmholtz resonators (combined with Tony's badass computing skillz) causes the pressure difference to eliminate most of the low end power loss, as well as add a sizable amount to the top end.

An exhaust is only worth ~5whp higher than stock, how ever a poorly designed exhaust can make you lose as much as 15whp.

I beg your pardon, i have to say i kind of ignored the slight loss at the very low points :}

But everything else is a worthy gain and as you say, the deltas are a great example of actual gains as opposed to just out-right amount made.

It's crazy because you can definitely feel how it gains a good amount of power in the 2.5k range compared to 2k with the ART pipes. I noticed it the first time I put them on.

Oh, looking at the delta's, you'll really feel that, it spikes massively in both power and torque at that point specifically, but is still really good from there on.

I'm looking forward to the ARTs. I've seen Tony's plots of the deltas from stock cats before, and also tended to ignore the losses below 2.3k rpm.

ARTs are a lot better than HFCs right? I mean I have ARTS now but before i had berks hfc, I felt a good amount of torque gain down low but once I get to the higher RPMs, I feel like the car doesnt make that much power than it was before with the Berks. Or is this all in my head. I know TP should be better than HFC and I know its always HFC & TP < ART pipes.

But why am I feeling like I lost highend power?

I have a nismo CBE exhaust paired with a 3'' hr y-pipe (m2performance).

You are correct in your ART > HFC and TP's.

Remember everything is relative, you'll feel the increased tq low down, the ART's will breather better in the top end, but it's all smooth power, before, you were probably feeling the lack of power low down and then noticing the gains up high that the HFC and TP's give you.

In short, you're feeling power all the way through, where as before, you got a large surge at the top compared to the lacking low end.

This just arrived today. Hopefully I'll have it installed this weekend. I'm considering having it modded to move the X closer to the cats to assist in exhaust scavenging, but wanted to know if any more knowledgeable folks think doing that may hurt the low end even more. I'll try to post some clips when I get it on.

The ARTs aren't here yet, but won't go on until I'm ready for an Osiris tune, which will probably a couple of months because work has me traveling a lot.

How do you figure your lowend is going to hurt?

My lowend is hurt due to adding cams and removing my ART pipes in return of increased midrange and top end.

My understanding is that increased flow will increase peak HP, but may end up taking some away on the low end. By moving the merge point, and aiding in scavenging, you are in effect increasing the flow. I'm worried that this will increase peak HP, again at the cost of some low end HP/torque.

Just a thought, happy to hear if I'm wrong.

Did you check out the pics and vids? When are you installing the exhaust?

Yeah, I checked them out. Thanks for sending them, the videos sound great. I'd like to get it installed this weekend, but haven't heard back from MBS yet. Maybe I'll give them a call today. Otherwise it'll be a few weeks.

Are going to add the magnaflow first or are you just looking for somewhere just to install it? If so I know someone who can install the exhaust for you.

How are your gaskets looking do they look beat up?

I think I still probably add the magnaflow and have it installed all at once. My boss has a lift that I was going to use if I wanted to do just the install myself, but I think I'll wait until the shop can get me in. Not sure how the gaskets look, I haven't been under there to check them out.

I meant the gaskets on the Gemini. I bought mine used also and the gaskets needed to be replaced.