# Possibly a dumb or overasked question, about backpressure



## Nightmare2003 (Jan 4, 2010)

Hello, and ahead of time I'm going to apologize if this is something that's been asked previously or overdone, however I'm genuinely curious and just came upon a revelation due to my residency. 
I have a '06 Goat, automatic transmission. So far I've done a Livernois Stage 2 cam and heads, Vararam cold air intake, custom 3" back exhaust with an H-pipe and glasspacks out the back, with stock manifolds and cats. I've done the tune and the happy stuff. So far, it's got the horsepower and torque that I'm happy with right now, at the moment. Maybe later I'll do a APS twin turbo or something. 
Alright, to the point. I'm an Alaskan resident currently stationed in California. I'm planning on keeping it that way too. Now this car is just too darn quiet for me to enjoy, it's bothering me. Everyone else says it's loud, but I'm nearly deaf and it doesn't sound as loud as my old 350z. I decided I want to do long tube headers without cats, and get straight pipes exiting out the side in the same place the Spintech side exits do. Am I going to run into any backpressure issues, or is that an old myth? I've heard it's going to be fine, and I've heard I'm going to suck a valve, the world's gonna stop spinning and Hugh Jackman's going to become wolverine and tear off the hood of my car and take a dump in the intake. Any clarification on this subject gents? Thanks a bunch!


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## AlaGreyGoat (Jul 6, 2006)

Add the catless LTs first. It will be a LOT louder than it is now!
I had an Xpipe and bullet glasspacks with orig manifolds and cats and
wasn't loud. I installed catless LTs and had to replace the bullets
with 6"x9" oval galsspacks to quieten it down a little.

Larry


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## svede1212 (Nov 1, 2005)

Back pressure is an urban myth that doesn't ever seem to die. Back pressure is not a good thing. You want gases to leave. What people confuse it with is exhaust velocity. What you don't want is a long system that is too large in diameter and exhaust gases slow down too much from the beginning of the system to the exit point. A properly sized pipe can give you both velocity and little back pressure. 

To your question I'd start with just the LTs and see what you think. LTs add a significant amout of volume. I personally wished mine was quieter. I have 4 mufflers and an X pipe on and it IMHO draws too much attention.


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## dustyminpin (Jun 19, 2006)

You want CATLESS mids and are living in the Peoples' Republic of California, home of CARB :confused


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## GM4life (Mar 18, 2007)

Don't know where your car is registered. If its regestered in Cali and you want loud exhuast good luck not getting cought. Loud exhaust catch the attention of cops too and it will give them the excuse to look under your hood. They look under your hood or under your car be prepared for a stiff penalty if you have LT's and or non CARB stuff. LT's is illegal in Cali, catless mids will be noticed too.


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## motoristx (Apr 27, 2010)

Be sure you check the "laws of the land". 

I was Stationed in ND with a jacked up truck, the law was the rear bumper had to be no higher then 27 inchs from the ground on a flat surface. mine was higher. Truck was registered, titled, plated in Texas, and it didn't matter! I had to modify my truck, like an 18 wheeler with that bar in the back on the trailer. 

My point is, somethings you can get away with, others you can't depending on the state you live in. 

Go to your legal office on base, or where ever your stationed (the same place you get a will and power of atterney), and ask them to help you figure out what you can and can't do if your car is registered in a differant state. 

also, Loudness you can get away with, once they see your Alaska plates... no cats would be a different story. Just like my bumper problem...


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## Nightmare2003 (Jan 4, 2010)

Thanks for the suggestions to all. I am stationed in California, yet my residency and registrations are still within Alaska. I actually have an appointment to get long tube catless mids installed then after reading Motoristx's post, I'm going to cancel. In the midst of my senility that has skipped my mind, I've heard of guys getting slammed over here despite having a out of state registration. Thank you for the reminder. I think I'm going to go ahead and get some JBA shorties and route the exhaust off to the sides. Or just get a louder car!


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## Poncho Dan (Jun 30, 2009)

Catless is violation of federal law, so technically CA could write you a ticket for it either way.

But as per diagnostics, backpressure should really never exceeed .5 PSI or it's considered to be restrictive. And Svede is right about exhaust gas pulse velocity.


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## dustyminpin (Jun 19, 2006)

Poncho Dan said:


> Catless is violation of federal law, so technically CA could write you a ticket for it either way.
> QUOTE]
> 
> But 90-95% of the people seem to do it anyway. I get made fun of at the Friday night cruise ins for my Kooks high-flow catted mids. "You paid an extra $200 for those instead of getting the 'off road' connecting pipes?... Mwa ha ha ha."
> Blow me.


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