Just a quick question. I had a stock header, with NO DOWNPIPE just 3 inch exhaust, no cat, and then a custom 3 inch exhaust with a magnaflow muffler.

Then I switched to the ZZP 3inch header/downpipe/magnaflow cat, with my custom 3 inch exhaust and maganflow muffler. It quited the car down some, thankfully, however it feels as if it does not reach boost as fast in the lower rpms. For example I could be in 5th gear at any reasonable speed before, floor it and automatically hit 10lbs of boost, now I hit like 7 and climb to 10 in like a matter of 1k rpms.

I am going to get the car on the dyno on monday to see if i actually LOST power from the 3 performance mods i did. I added an injen cold air intake, 3inch zzp header, 3inch zzp downpipe, and the maganflow cat. So if I LOST power from those mods, I will be pissed, or I will be deleting the cat lol.

 

Umm...ok. I'm going to touch this I guess because I'm sure it has been explained OVER AND OVER AND OVER AND OVER AND OVER AND OVER AND OVER and no one still gets the point. In fact I'm going to save this post because I think I have made one similar to this at least 30 or 40 times.

BOOST DOES NOT MAKE POWER. Airflow does. Understand that. More boost /= more power. More cfm = more power.

You are opening the exhaust up and allowing more air to flow more freely through your motor, hence the boost (note: boost is a measure of pressure held inside of the engine) will lower because there is a more freely flowing path. Doing those mods you SHOULD see a drop in boost. In fact, if you have a clogged cat your boost will actually RAISE, but the car will make significantly less power.

This style of post is rice math at it's finest. Use the search function first please.

I think a mod should sticky a post with a title that says: Mooding your exhaust will lower your boost but make more power so deal with it.

 

Hey bro, relax. I understand the search button, but I really couldn't find what I was looking for, and I just wanted a quick answer. Instead of me searching for 30 mins to find the exact post I needed, you gave me the correct answer right away. I learned something from you, and the information you provided I can now pass that along to others.

Thank you for the information, I was NOT aware of this. Again, thank you, but please don't take the frustration of multiple posts on the same thing out on me. Because we all do it at times when we can't find what we need via search.

Sorry, but thanks again for the help.

 

Your 3" catback will also most likely result in a lose of power.

 

I thought if you had over X amount of power it was good to go with 3 inches, and if you had under X amount of power its good to go with 2.5inch exhaust.

Isn't this correct or am I mistaking? I am currently looking at over 250whp as it sits now roughly, however I will have dyno sheets to prove more/less and this is WITHOUT the meth. Thanks guys.

I am also getting a professional dyno tune in july.

 

Unless your breaking 300whp, you can get by with a 2.5" catback. If you want more flow then a 2.5" but your still under 300whp, a 2.75" would be your best bet.

You need ~2.2cfm of exhaust flow per peak hp. However, that is in your header and downpipe. You can and should only flow 80~90% of that in your cat back. As your exhaust cools, it will get denser. So a slight step down in max flow in your cat back will help keep exhaust volocity high.

Yes I know my spelling sucks.

 

well since 300whp is going to be achieved then I am fine. Thanks. I do realize I wont be doing this on the 42lbers either.