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Discussion Starter · #1 ·
How’s it going forum, I recently bought a Fast Intentions (FI) Catted Downpipe (DP) that I plan to install on my stock exhaust. I do have a few questions and any bits or pieces of information would be greatly appreciated.
1. What hp gain can I expect from DP on stock exhaust?
2. How much louder would DP be on stock exhaust? Videos?
3. FI shows a 43 hp increase with DP and stock exhaust, is that with a tune?
4. Any other information about downpipes and exhaust?
Thank you to everyone helping out.
 

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How’s it going forum, I recently bought a Fast Intentions (FI) Catted Downpipe (DP) that I plan to install on my stock exhaust.
I'm going to ask the obvious question - why go through the trouble and expense with installing these freer-flowing DPs, and then essentially keeping a cork in the downstream exhaust flow?
 

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I'm going to ask the obvious question - why go through the trouble and expense with installing these freer-flowing DPs, and then essentially keeping a cork in the downstream exhaust flow?
Because you are still uncorking the most restrictive part of the exhaust and get a very nice tone. I love the sound a stock muffler with full exhaust otherwise.
 

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Discussion Starter · #4 ·
Only thing I can afford right now, maybe later I’ll piece together the rest of the cat back but for now all I’m doing is downpipes on stock exhaust
 

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How’s it going forum, I recently bought a Fast Intentions (FI) Catted Downpipe (DP) that I plan to install on my stock exhaust. I do have a few questions and any bits or pieces of information would be greatly appreciated.
1. What hp gain can I expect from DP on stock exhaust?
2. How much louder would DP be on stock exhaust? Videos?
3. FI shows a 43 hp increase with DP and stock exhaust, is that with a tune?
4. Any other information about downpipes and exhaust?
Thank you to everyone helping out.
1. very little. you will build boost faster in the bottom range but the top end will be mostly the same. i dont have dyno proof but i have went down this route myself in preparation for a Greddy exhaust (that's on the way). again, its not a significant improvement. it feels like the difference between driving your car when its 60 degrees out vs when its 95 and heat soaked, around 15-20hp/tq if i had to guesstimate.

2. i barely noticed a difference at all. very slight additional increase in the midrange but nothing worth mentioning. sounds same as stock for normal driving.

3. the tune is the vast majority of the increase, lower DPs on a stock exhaust doesn't help much. disregard, i misread. yes, that sounds about right for a low boost VR30. i would put it in a range from roughly 25-40hp/tq, with lower numbers being due to heat soak.

4. stay away from systems that use a steel braided flex section, ALL of them will leak eventually. it doesnt matter who makes them, its just a byproduct of the design. 2.5" exhaust will be fine if you stay under 450rwhp. above that, it will become a restriction as HP and rpm increases. 3" exhaust is significantly louder than 2.5" exhaust. systems with longer/larger resonators and mufflers will be more quiet than smaller/shorter ones. exhaust systems are the second worst dollar per hp mod you can do to your car, air intakes are the worst.

last note, complete street performance website lists the Greddy exhaust for $1155.99 and they have a code for 5% off, making it $1098.20 with no sales tax and free shipping. That makes it the least expensive system available for a Q50 that doesn't suck.
 
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