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Discussion Starter #1
What's the difference between the catted full vs lower down pipe? Isn't that the same thing as stock primary cats with lower down pipes? Or is because the catted full has a higher flowing cat over stock?
I also heard that with full, you may have to worry about boost spikes. I also heard with the RS model you may not have to worry about it because it has extra turbo sensors protecting it. Would a BOV help with this?
I also read that a full down pipe had 20hp gains over the lower down pipe. How much gains do you think would catted full down pipes be over lowers?
 

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I had FI LDPs, and then graduated to FI Full Catted DPs. I noticed the difference "seat of the pants" immediately with an increase in torque in the lower rpms. I didn't have much experience with Full DPs w/o a tune, however, as FI installed the Full DPs, and later in the week Seb @ SpecialtyZ installed the Ecutek tune. FWIW, on 93 pump gas, my Q60 Red Sport put up 437 WHP & 502 WTQ on a DynoJet AWD Dyno.

Seb tuned my car to 1.3 bar on 93 pump gas, which he considers a "safe" tune, realizing I could experience 2-3 psi boost upon throttle closure, which would equate to a max of 22 psi. Ecutek programming apparently softens the throttle plate closure rate to mimimize boost spikes.

I've been using this tune for over one year, and my car has 23k miles on it - w/no BOVs. Oil & filter changes every 5k miles with no oil consumed between changes.

My guess is your torque #'s will improve with Full 3" Catted DPs. In the case of FI, the Catted DPs produce slightly better torque #'s than the Full 3" Straight DPs, likely due some beneficial backpressure from the cats at lower rpms. FI sources Vibrant Performance GESi cats for its Catted DPs, which are rated for 500 HP/bank, so they are a low-restriction design.
 

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LDP's eliminate the secondary cats which are the biggest "choke point" in the OEM system while retaining the OEM large primary cat. The secondary cats are ONLY 1.5" at their tightest diameter.
Full downpipes eliminate the primary and secondary cats and open the first part of your exhaust system up to 2.5"-3" depending on the brand.

A CBE retains the choke point of the secondary cats and as a result yeilds very low power gains.

Just LDP's make a huge difference. Not a whole lot more power gains than full downpipes. Streight downpipes eliminate all 4 cats and are not road legal. The reason I got the Fast Intentions full catted downpipes as they are 48 state CARB legal. Expensive yes, but for me worth the $.
LDP's are easy to install a LOT less $ and yeild very good results. Best bang for the buck.

Eliminating the secondary cats is the key to opening up the OEM exhaust system.
Fast Intentions has dynos showing just how much power the secondary cats cut out. LDP's and a CBE is the way to go and still run cats.

My catted downpipes replace the primary cats with a high flow cats and larger tubing.

I was confused when I first got my car and did not understand the system and it's problems. Kevin at FI explained it all to me.

I have no regrets getting my FI exhaust system. Big power, pleasant sound, and superb quality.

I hope this helps some.
 

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LDP's eliminate the secondary cats which are the biggest "choke point" in the OEM system while retaining the OEM large primary cat. The secondary cats are ONLY 1.5" at their tightest diameter.
Full downpipes eliminate the primary and secondary cats and open the first part of your exhaust system up to 2.5"-3" depending on the brand.

A CBE retains the choke point of the secondary cats and as a result yeilds very low power gains.

Just LDP's make a huge difference. Not a whole lot more power gains than full downpipes. Streight downpipes eliminate all 4 cats and are not road legal. The reason I got the Fast Intentions full catted downpipes as they are 48 state CARB legal. Expensive yes, but for me worth the $.
LDP's are easy to install a LOT less $ and yeild very good results. Best bang for the buck.

Eliminating the secondary cats is the key to opening up the OEM exhaust system.
Fast Intentions has dynos showing just how much power the secondary cats cut out. LDP's and a CBE is the way to go and still run cats.

My catted downpipes replace the primary cats with a high flow cats and larger tubing.

I was confused when I first got my car and did not understand the system and it's problems. Kevin at FI explained it all to me.

I have no regrets getting my FI exhaust system. Big power, pleasant sound, and superb quality.

I hope this helps some.
Thank you! This was very helpful as I have been bouncing between full downpipes and LDP's.
 

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Discussion Starter #9
So how much HP gains do you think a catted full down pipe will be over a lower down pipe?

Are there any HP limiting factors with the catted full down pipe? Ex. anything over 500hp it will deteriorate or performance suffers vs. a full non-catted down pipe.

How much louder do you think a full vs catted full will be?

What about the smell? Do you think a full will be unbearable because it already stinks with just my lowers.
 

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You will probably be about the same as you are now with lower downpipes with regard to smell with full, catted downpipes. It won't be so much the horsepower, as it is the torque. Z1 Motorsports got 608 lb-ft at the wheels with their downpipes and a tune. I think theirs were catless.

 

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Exhaust restriction costs power....even more so on a turbo car due to back pressure. Anything you can do to uncork the exhaust will A) decrease spool, B) increase efficiency, C) increase power/torque. The more power you make the more the restriction matters. Yes you can smell the exhaust and it smokes, but it never really bothered me.
 

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So how much HP gains do you think a catted full down pipe will be over a lower down pipe?

Are there any HP limiting factors with the catted full down pipe? Ex. anything over 500hp it will deteriorate or performance suffers vs. a full non-catted down pipe.

How much louder do you think a full vs catted full will be?

What about the smell? Do you think a full will be unbearable because it already stinks with just my lowers.
According to FI, their full downpipes with high flow cats coupled with their CBE and a EcuTek tune gained 65 HP and 149 ft-lbs of torque at 16 PSI on 91 octane gas. Without the EcuTek tune, the gain was 42 HP and 76 ft-lbs of torque at 14 PSI on 91 octane gas. The numbers on their full downpipe with no cats are the same.

Their LDP combined with their CBE gained 36 HP and 46 ft-lbs of torque on stock tune.

Their CBE alone gained 16 HP and 30 ft-lbs of torque on stock tune.
 

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...

Just LDP's make a huge difference. Not a whole lot more power gains than full downpipes. Streight downpipes eliminate all 4 cats and are not road legal. The reason I got the Fast Intentions full catted downpipes as they are 48 state CARB legal. Expensive yes, but for me worth the $.
LDP's are easy to install a LOT less $ and yeild very good results. Best bang for the buck.

...
Is CARB (California Air Resources Board) used outside of CA?
 

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Is CARB (California Air Resources Board) used outside of CA?
Yes, CARB standards for criteria pollutants and greenhouse gases for low emission vehicles have been adopted by 13 other states so far. Even the province of Quebec adopted CARB standards in 2010.
 

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What's the expected gain of ONLY doing LDP's? (Exclude any tune or JB4, exclude any CBE)
 

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What's the expected gain of ONLY doing LDP's? (Exclude any tune or JB4, exclude any CBE)
I haven't seen anyone dyno an otherwise stock car with only LDPs. Personally I wouldn't bother if that's literally the only mod you'll do.

So this requires some speculation but this may come close to answering your question.
Here is a dyno for the CZP (resonated) LDPs. It doesn't state what any other mods are but, because the HP is under 300 and the HP Gain is modest, I'm going to assume this is a non Red Sport and there are no other mods. If it's true that there are no other mods, then LDPs by themselves appear to give +4 WHP and +12 WTQ.

Link
 

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Discussion Starter #17
Z1 replied and said a catted full is around 10hp over LDP untuned. AMS says their full is 20hp over LDP. So estimate 4hp ldp (untuned), 14hp catted downpipe (untuned), 24hp full downpipe (not sure if tuned or untuned)
 

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I had FI LDPs, and then graduated to FI Full Catted DPs. I noticed the difference "seat of the pants" immediately with an increase in torque in the lower rpms. I didn't have much experience with Full DPs w/o a tune, however, as FI installed the Full DPs, and later in the week Seb @ SpecialtyZ installed the Ecutek tune. FWIW, on 93 pump gas, my Q60 Red Sport put up 437 WHP & 502 WTQ on a DynoJet AWD Dyno.

Seb tuned my car to 1.3 bar on 93 pump gas, which he considers a "safe" tune, realizing I could experience 2-3 psi boost upon throttle closure, which would equate to a max of 22 psi. Ecutek programming apparently softens the throttle plate closure rate to mimimize boost spikes.

I've been using this tune for over one year, and my car has 23k miles on it - w/no BOVs. Oil & filter changes every 5k miles with no oil consumed between changes.

My guess is your torque #'s will improve with Full 3" Catted DPs. In the case of FI, the Catted DPs produce slightly better torque #'s than the Full 3" Straight DPs, likely due some beneficial backpressure from the cats at lower rpms. FI sources Vibrant Performance GESi cats for its Catted DPs, which are rated for 500 HP/bank, so they are a low-restriction design.
LDP's eliminate the secondary cats which are the biggest "choke point" in the OEM system while retaining the OEM large primary cat. The secondary cats are ONLY 1.5" at their tightest diameter.
Full downpipes eliminate the primary and secondary cats and open the first part of your exhaust system up to 2.5"-3" depending on the brand.

A CBE retains the choke point of the secondary cats and as a result yeilds very low power gains.

Just LDP's make a huge difference. Not a whole lot more power gains than full downpipes. Streight downpipes eliminate all 4 cats and are not road legal. The reason I got the Fast Intentions full catted downpipes as they are 48 state CARB legal. Expensive yes, but for me worth the $.
LDP's are easy to install a LOT less $ and yeild very good results. Best bang for the buck.

Eliminating the secondary cats is the key to opening up the OEM exhaust system.
Fast Intentions has dynos showing just how much power the secondary cats cut out. LDP's and a CBE is the way to go and still run cats.

My catted downpipes replace the primary cats with a high flow cats and larger tubing.

I was confused when I first got my car and did not understand the system and it's problems. Kevin at FI explained it all to me.

I have no regrets getting my FI exhaust system. Big power, pleasant sound, and superb quality.

I couldn't have explained this any better myself. Thank you both for answering the question and glad that you're both enjoying your parts years later. ;)

- Kevin
 

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Are there any companies that make a HFC upper downpipe? I don’t recall ever seeing. With so many of us buying ldp’s and not wanting to shell out $1500 plus for a full catted downpipe all at once, it’s seems like a smart market opportunity to offer an aftermarket catted upper downpipe upgrade.
 
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