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Discussion Starter · #1 ·
Ok after last week i got my jba shorties, jba high flows and i already had my flowmaster system on and they advised to cut the resos out so i agreed to have that done, now my car is running slower then before after dropping about $2000 in the exhaust.
Yes i did the fuse pull and even the battery disconnect i dont know whats going on but on my 0-60 run is slower then before and im pretty pissed off about it. Any ideas from the pros out there with exhaust mods as to why this car is running like crapola.
 

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Ok after last week i got my jba shorties, jba high flows and i already had my flowmaster system on and they advised to cut the resos out so i agreed to have that done, now my car is running slower then before after dropping about $2000 in the exhaust.
Yes i did the fuse pull and even the battery disconnect i dont know whats going on but on my 0-60 run is slower then before and im pretty pissed off about it. Any ideas from the pros out there with exhaust mods as to why this car is running like crapola.

When you pull that fuse, it takes a little while for your car to re-learn itself. How long did you drive to test it?
 

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I did that like 5 days ago and did the battery cable pull 2 days ago.
It will take a few hundred miles for the car to adjust. Be patient, you'll be happy with it soon enough
 

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It will take a few hundred miles for the car to adjust. Be patient, you'll be happy with it soon enough
X2. I drive about 100 miles a day, it took about a week and a half to see any gains after a fuse full. Sometimes I wonder if it is necessary.
 

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do you guys think his slow 0-60 is because of low back pressure?
 

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Discussion Starter · #8 ·
thats what my friend maybe thought but hes not like a big exhaust person but if it was because of that how do i fix it?
 

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Having a free flowing exhaust can possibly reduce your 0-60 times. With all exhausts, there is a trade off with regards to HP and RPM's. I bet you gained in the 1/4 mile times.

Here is an interesting article......

"You want zero backpressure not some backpressure as you may sometimes hear from a salesman or an oldtimer domestic V8 hot rodder.

Stock backpressure is around 16 psi in a GSR. Good aftermarket exhausts yield 2-5 psi backpressure. "Bolt-ons only" engine packages, in the past, used exhausts with some backpressure, since there is this incorrect belief that having a little backpressure prevents the fresh air/fuel from shooting into the header at cam overlap (when both the opening intake valve & the closing exhaust valve are simultaneously, partially open). The backpressure supposedly "pushed" the fresh air/fuel back into the combustion chamber rather than having it go into the header. This shooting of fresh air/fuel from the intake manifold and intake port into the header cannot happen at cam overlap, since the pressure inside the header is already much higher than on the intake side , even when there is zero backpressure.

In reality, having more backpressure reduces the difference between the higher pressure in the head's exhaust port and lower pressure in the header and cat. You need this difference in pressure going from the head to the exhaust system or "pressure gradient" to keep the exhaust flow speed or energy at a high level. Having some backpressure during cam overlap and the exhaust stroke means that the exhaust gas must now push against something and therefore, this backwards force slows exhaust gas down.


This need for backpressure no longer exists when you have a properly tuned (timed) engine and a good stepped header. In fact, increased backpressure may lead to backwards flow or "reversion", where the exhaust gas travels backwards into the combustion chamber and dilutes the fresh intake charge at cam overlap. At the very least, it slows exhaust flow velocity or energy and prevents the creation of a vacuum for scavenging.

So please ignore the obsolete "you should have at least some backpressure" sales pitch. It's all about the creating high exhaust flow velocity/speed or energy leaving the exhaust port, in order for the header-cat-exhaust SYSTEM to do it's job properly (i.e. remove all the burnt exhaust gases and help pull in fresh intake charge by scavenging at cam overlap) and make power for you.

Regarding the backpressure issue:

Many people use backpressure to get midrange driveability at the sacrifice of lower power potential at the upper powerband rpms. Using back pressure is the wrong way to build a high performance exhaust system. The exhaust system should extract the exhaust gas from the header, to minimize parasitic pumping pressures. (Note: I think Zoomers states their design does this)

The proper way to make an exhaust system that will act as an extractor is to properly size the tubing so that the the exhaust gas' flow velocity creates a "vacuum" behind the header.

Also, you have to realize that making a sytem which provides the best performance at all throttle positions and all powerband rpm ranges is next to impossible. There's always going to be a compromise and giving up some optimal power potential in one area of the rpm range.

You must tune the exhaust size/length for the throttle positions and rpm ranges where you want the most performance knowing that you'll sacrifice performance at the other end of the rpm range.
 

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Im starting to think that this whole fuse pull thing is crap. I think the fuse pull makes your car run like garbage for a while, and then gradually brings it back to normal so you think "Man, this baby sure is runnin better now than it was when I first pulled the fuse about two weeks ago!" Im still not buying into it one bit....

However, I know how you are feeling. I never did the fuse pull whne I put on my CAI (didnt know about it yet) and I was like whatever. Car seemed to pull a little better and the sound the engine makes was worth it enough. But by the time I bought my exhaust, I had heard about all the fuse pull business so I figured Id give it a shot because people claimed that the difference was "night and day" to before and after the fuse pull..... Yeah right!

Plenty of time has passedsince the fuse pull and the car seems to finally have settled in back where it was when I started (i.e. pre-CAI and pre-catback exhaust system). I dont believe in this fuse pull crap one bit.... not one bit I tell you!

Maybe it's something with the 2007 model year that it just doesnt work the same?

Maybe its a Sublime Daytona thing?

I don't know what it is, but it aint workin for me!

-Pat
 

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Discussion Starter · #14 · (Edited)
Hahaha..i do that everytime i hit a red light now..Can i get a tire fund going on here..LOL..
Thanks Crow for the awesome write up. Im taking my ride to the track next week, weather permitting, and well see what my girl can do.

Again thanks for evereones help here!

Oh TBY you were right that diablo is pulling me in the back seat just about. Best money i spent!
 
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