Does a Catted Downpipe really do anything??

[Fastlax16]

Absolutely false lol. The downpipe is actually a mod that doesn't really need a tune to show its gains.

The downpipe does a LOT on this car, the stock one is extremely restrictive. The thing that most people don't realize is that they just look at peak gains and say it only adds a little bit. The downpipes main function in reducing restriction is to increase turbo spool and reduce how hard the turbo has to work to create boost and subsequently greatly increase the area under the curve of both tq and hp. No tuning is necessary to see the majority of these increases.

It is generally suggested to get a tune with a downpipe to turn off the CEL

The main reason aftermarket pipe designs are this beneficial is pipe design, diameter and smooth transitions in the curves. Aftermarket catless downpipes show next to 0 increase over catted versions, so don't cheap out and get one with a good cat.

Are there some gains sure, are they perceptible? I don’t think so having driven an untuned car with one for a bit. How much time have you spent driving a car with a downpipe and no tune?

I actually don’t have a tune now, just a jb4. Next time I’m out in the country I’ll set it to stock and do some dragy runs, see how they compare to the bone stock runs I did before putting any parts on. Not expecting a huge difference.

you don’t really need a tune to cancel out the cel. 5 dollar Amazon spacer has done the trick on multiple mk7s I’ve owned.

 

[Keehs360]

Absolutely false lol. The downpipe is actually a mod that doesn't really need a tune to show its gains.

The downpipe does a LOT on this car, the stock one is extremely restrictive. The thing that most people don't realize is that they just look at peak gains and say it only adds a little bit. The downpipes main function in reducing restriction is to increase turbo spool and reduce how hard the turbo has to work to create boost and subsequently greatly increase the area under the curve of both tq and hp. No tuning is necessary to see the majority of these increases.

It is generally suggested to get a tune with a downpipe to turn off the CEL

The main reason aftermarket pipe designs are this beneficial is pipe design, diameter and smooth transitions in the curves. Aftermarket catless downpipes show next to 0 increase over catted versions, so don't cheap out and get one with a good cat.

Totally correct. Peak gains won’t tell the story. But to maximize its gains, shutting of cel’s and playing with the boost map will yield great results.

 

[Keehs360]

Are there some gains sure, are they perceptible? I don’t think so having driven an untuned car with one for a bit. How much time have you spent driving a car with a downpipe and no tune?

I actually don’t have a tune now, just a jb4. Next time I’m out the the country I’ll set it to stock and do some dragy runs, see how they compare to the bone stock runs I did before putting any parts on. Not expecting a huge difference.

you don’t really need a tune to cancel out the cel. 5 dollar Amazon spacer has done the trick on multiple mk7s I’ve owned.

Untuned you’d probably gain some power. Not anything to celebrate but there will be a gain. With less restrictions now one can add a more aggressive boost map. That’s where the power gains from a downpipe lie

 

[Al_in_Philly]

So I have a custom exhaust guy wanting to make a DP for me, he says he can use 3" pipe but the flange has to be 2.5" just like the stock DP. Seems to me like there will still be a substantial restriction with that flange, has anyone actually done a before and after Dyno run to show if Downpipes add any power? I have Unitronic Stage 1+ btw.

Does your "exhaust guy" know that an IS38 has a 3" flange, not 2.5"?

 

[Fastlax16]

Untuned you’d probably gain some power. Not anything to celebrate but there will be a gain. With less restrictions now one can add a more aggressive boost map. That’s where the power gains from a downpipe lie

that’s what I said... youll gain power but nothing to write home about.

 

[emichel6888]

It adds about 30-40 HP and will knock 3-4 tenths off your 0-60 and 1/4 mile. It is noticeable but not as big a difference as a tune. I run a JB4 and did some consistent testing as I modified the car. Stock I ran 0-60 around 4.6 and 13 @105, JB4 ran around 0-60 4.0 and 12.3 @112, That was a very noticeable improvement seat of the pants. With the DP (IE) I managed a 0-60 3.7 and 11.9 @ 115. A definite increase in power but not as big a jump as the initial tune.
Is it worth it? Depends, but for most just wanting an added thrill on the street probably not, because then you also have to do something about O2 CEL and it is not exactly cheap.
Initial improvements are relatively cheap and easy, and give the biggest improvement. From there things get more expensive for ever smaller gains.
As to whether you need a tune or not for a DP the answer is yes and no. The DP definitely improves flow and turbo response, what I found is that in the summer I can run the DP without the JB4 and it works okay although adding fuel helps make more power for sure. However, if i try to run the DP without the JB4 controlling the boost and adding fuel when it gets cold the stock ECU with the improved flow will cause over boost conditions and put the car into a limp mode where you have to switch the ignition on and off to clear it.
Other DP's or cars might not do this depending on several factors, but regardless yes you can get away with running a DP without some sort of tune but it is not recommended. You will be running lean (increased risk of detonation) and you can get over boost conditions.

 

[jimlloyd40]

It adds about 30-40 HP and will knock 3-4 tenths off your 0-60 and 1/4 mile. It is noticeable but not as big a difference as a tune. I run a JB4 and did some consistent testing as I modified the car. Stock I ran 0-60 around 4.6 and 13 @105, JB4 ran around 0-60 4.0 and 12.3 @112, That was a very noticeable improvement seat of the pants. With the DP (IE) I managed a 0-60 3.7 and 11.9 @ 115. A definite increase in power but not as big a jump as the initial tune.
Is it worth it? Depends, but for most just wanting an added thrill on the street probably not, because then you also have to do something about O2 CEL and it is not exactly cheap.
Initial improvements are relatively cheap and easy, and give the biggest improvement. From there things get more expensive for ever smaller gains.
As to whether you need a tune or not for a DP the answer is yes and no. The DP definitely improves flow and turbo response, what I found is that in the summer I can run the DP without the JB4 and it works okay although adding fuel helps make more power for sure. However, if i try to run the DP without the JB4 controlling the boost and adding fuel when it gets cold the stock ECU with the improved flow will cause over boost conditions and put the car into a limp mode where you have to switch the ignition on and off to clear it.
Other DP's or cars might not do this depending on several factors, but regardless yes you can get away with running a DP without some sort of tune but it is not recommended. You will be running lean (increased risk of detonation) and you can get over boost conditions.

A high flow catted DP might give you 10-15 HP and a catless DP 20-25 HP.

 

[Lager_Ace]

emichel6888 Was considering a DP. Good to know, I just added a JB4 map 1. I've ran stock for 3 years with just a drop in filter and guard removed. Good enough bump for someone not interested in track or drag times.

 

[uberdot]

If anyone here is overtly concerned with the environment and driving a VW they’re either uninformed or misinformed. Or just plain delusional.

 

[emichel6888]

A high flow catted DP might give you 10-15 HP and a catless DP 20-25 HP.

Without a tune? That could be, I did adjust the JB4 for the DP (was able to run more boost and added fuel). But the DP does more than just improve flow, it also causes the car to make more boost, That can vary on the DP, the IE seems to flow extremely well. I raced a guy with a cat less DP and all else more or less the same, there was nothing in it, we were neck and neck on the highway and whoever jumped first...