[Nado]

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Hello,

Just ran across the video from WYF and saw that with his car with the MAD catless DP lost power when dyno'ed. Granted he is running a RaceChip setup and not a JB4. But, did anyone else lose whp and torque when adding DPs?

I have never ran across a turbo application that lost a bit of power by adding larger DPs.

Thanks.
Nathan

[Sbm007]

I've always understood that larger catless DPs are a must if you upgrade turbos, but the stock DPs are actually pretty good and work well with stock turbos.

I can see why you would lose some power as the cats probably help maintain a level of backpressure which helps torque lower in the rev range.

There was a similar video recently that I saw by someone in the Audi scene (S4 B9 platform) where catless DP actually lost around 10 hp:

[Nado]

Originally Posted by Sbm007

I've always understood that larger catless DPs are a must if you upgrade turbos, but the stock DPs are actually pretty good and work well with stock turbos.

I can see why you would lose some power as the cats probably help maintain a level of backpressure which helps torque lower in the rev range.

There was a similar video recently that I saw by someone in the Audi scene (S4 B9 platform) where catless DP actually lost around 10 hp:

I can see where with an actual tune that this can be resolved. But, I still cant imagine that even with a JB4 that aftermarket DP would lose power. Perhaps the DME is closing the throttle a bit? Im not sure, as I have a set, new that I was going to install. But, I might sell and just pop a mid pipe on for some sound. Not going to waste time and money to lose performance

Hoping others will chime in, especially MAD themselves.

[mike@x-ph.com]

The catless downpipes reduce backpressure from the turbos, allowing them to spool easier.

If you do not change the boost, your turbos can reach the target PSI with less work. You will get some power increase from the better airflow, but not that significant.

You can significantly increase power if you take advantage of the better airflow and increase your boost.

In either case, you won't lose any power by eliminating backpressure.

Note: The brand of the downpipe does not make any difference.

[Nado]

Originally Posted by mike@x-ph.com

The catless downpipes reduce backpressure from the turbos, allowing them to spool easier.

If you do not change the boost, your turbos can reach the target PSI with less work. You will get some power increase from the better airflow, but not that significant.

You can significantly increase power if you take advantage of the better airflow and increase your boost.

In either case, you won't lose any power by eliminating backpressure.

Note: The brand of the downpipe does not make any difference.

Understandable. But, you are essentially saying that you will lose peak power with DPs and no tune or piggyback. Because its reaching peak boost faster.

But if you have a JB4/Racechip, etc... that is upping the boost, then does the same philosophy apply? You hit boost quicker, and may lose a bit of peak power as boost is achieved earlier? If that is the case, then the only real advantage for larger DPs is with an actual tune. Or that you might hit peak numbers a bit quicker/earlier in the powerband.

Correct?

[Info@mad-us.com]

Hi,

The issue he was having has nothing to do with the downpipes per se its more the vehicles factory tuning. Since he removed the restriction the vehicle thinks its now over producing hp and lowered the boost slightly to make up for it. Unfortunately the racechip at least at the time of the dyno required a recalibration to work properly which I believe he did but, im not 100% the racechip was able to overcome the issue with the sensors it connects to.

[Nado]

Originally Posted by Info@mad-us.com

Hi,

The issue he was having has nothing to do with the downpipes per se its more the vehicles factory tuning. Since he removed the restriction the vehicle thinks its now over producing hp and lowered the boost slightly to make up for it. Unfortunately the racechip at least at the time of the dyno required a recalibration to work properly which I believe he did but, im not 100% the racechip was able to overcome the issue with the sensors it connects to.

Hello,
Thanks for chiming in! Can you comment with your experience with your DPs and JB4s? Was an actual gain or was it a bit of a loss as well?

Appreciate your feedback.

[Info@mad-us.com]

Originally Posted by Sbm007

I've always understood that larger catless DPs are a must if you upgrade turbos, but the stock DPs are actually pretty good and work well with stock turbos.

I can see why you would lose some power as the cats probably help maintain a level of backpressure which helps torque lower in the rev range.

There was a similar video recently that I saw by someone in the Audi scene (S4 B9 platform) where catless DP actually lost around 10 hp:

Here are actual logs between the highest quality sport cat vs our catless downpipe on the same vehicle. The engine is a b58 but still pretty comparable.

https://f30.bimmerpost.com/forums/sh....php?t=1982680

[Info@mad-us.com]

Originally Posted by Nado

Hello,
Thanks for chiming in! Can you comment with your experience with your DPs and JB4s? Was an actual gain or was it a bit of a loss as well?

Appreciate your feedback.

Jb4's have much more control than the racechip which in my opinion is a lower tech style boost controller just adding boost by rpm. Don't get me wrong it works great for people who want a easy to install tuning solution but when it comes to overriding the ecu the Jb4 or better yet Flash is the way to go.

We have seen some crazy hp numbers with the jb4 and flash platform using our downpipes.

[Indo Rider]

I don't have direct experience on a dyno, but I've seen several posts on this topic saying that if you dyno immediately after installing catless downpipes you might see a slight power loss due to throttle closures, lower boost, or the ECU otherwise trying to achieve the same target power level with less restrictve exhaust. But if you drive the car a bit and give the ECU some time to adapt this "loss" goes away. But then there is also no real gain, because the ECU has figured out the adjustments to achieve the same target power output, likely at lower boost. Then you tune with whatever tune you want and make power more efficiently than if you still had the stock downpipes. Bolt on parts alone just don't make more power like they did on older turbo platforms without tuning to take advantage, but the fundamental physics still apply, so you can increase you ceiling or just make the same power more efficiently.

[Nado]

Originally Posted by Indo Rider

I don't have direct experience on a dyno, but I've seen several posts on this topic saying that if you dyno immediately after installing catless downpipes you might see a slight power loss due to throttle closures, lower boost, or the ECU otherwise trying to achieve the same target power level with less restrictve exhaust. But if you drive the car a bit and give the ECU some time to adapt this "loss" goes away. But then there is also no real gain, because the ECU has figured out the adjustments to achieve the same target power output, likely at lower boost. Then you tune with whatever tune you want and make power more efficiently than if you still had the stock downpipes. Bolt on parts alone just don't make more power like they did on older turbo platforms without tuning to take advantage, but the fundamental physics still apply, so you can increase you ceiling or just make the same power more efficiently.

That is sort of my take. I was planning on adding a JB4. But if the catless DPs dont really offer any gains, Im going to wait and apply that money else where. Then if I unlock I can put on some DPs. Id rather have a midpipe for sound vs a DP for sound with no results.

Again, just trying to make good use of my monies. No reason to put a DP on if it doesnt really offer any gains (same reason why Im not spending $500 on intakes).

[Indo Rider]

Originally Posted by Nado

That is sort of my take. I was planning on adding a JB4. But if the catless DPs dont really offer any gains, Im going to wait and apply that money else where. Then if I unlock I can put on some DPs. Id rather have a midpipe for sound vs a DP for sound with no results.

Again, just trying to make good use of my monies. No reason to put a DP on if it doesnt really offer any gains (same reason why Im not spending $500 on intakes).

Yeah, I think the stock downpipes are really not that terribly restrictive on this car. When you look at the the diameter of the cat section, its huge compared the rest of the pipe, much more so than lots of other stock downpipes.

[Nado]

Originally Posted by Info@mad-us.com

Here are actual logs between the highest quality sport cat vs our catless downpipe on the same vehicle. The engine is a b58 but still pretty comparable.

https://f30.bimmerpost.com/forums/sh....php?t=1982680

Thank you. But, the only difference is that the subject car has an actual tune, and not a piggyback? I have no doubt that with an actual tune DP will yield great gains.

[Nado]

Originally Posted by Info@mad-us.com

Jb4's have much more control than the racechip which in my opinion is a lower tech style boost controller just adding boost by rpm. Don't get me wrong it works great for people who want a easy to install tuning solution but when it comes to overriding the ecu the Jb4 or better yet Flash is the way to go.

We have seen some crazy hp numbers with the jb4 and flash platform using our downpipes.

Well....the good part is I have them already. So maybe Ill just pop a JB4 on, run it for a week or so. Then add the DPs and do some comparisons. Worse case, I remove them and grab your midpipe

[Nado]

Originally Posted by Indo Rider

Yeah, I think the stock downpipes are really not that terribly restrictive on this car. When you look at the the diameter of the cat section, its huge compared the rest of the pipe, much more so than lots of other stock downpipes.

True.

I think Ill pop on a JB4 first and run it for a bit. Then will decide if I sell the DP and grab a mid pipe for better sound. I can always grab the DPs if I ever unlock the DME.

[Hit_Apex]

I can't help but think the OEM S58 tune level is an important piece of this equation. That the benefit of a piggyback w/catless downpipes likely vary among base/comp/CSL as the higher OEM tunes allow for more fueling and timing.

I definitely would not draw any conclusions based on a B9 S4 datapoint.

[Fugazii]

Originally Posted by Nado

Hello,

Just ran across the video from WYF and saw that with his car with the MAD catless DP lost power when dyno'ed. Granted he is running a RaceChip setup and not a JB4. But, did anyone else lose whp and torque when adding DPs?

I have never ran across a turbo application that lost a bit of power by adding larger DPs.

Thanks.
Nathan

Great thread you just answered my question!

[Info@mad-us.com]

Originally Posted by Indo Rider

I don't have direct experience on a dyno, but I've seen several posts on this topic saying that if you dyno immediately after installing catless downpipes you might see a slight power loss due to throttle closures, lower boost, or the ECU otherwise trying to achieve the same target power level with less restrictve exhaust. But if you drive the car a bit and give the ECU some time to adapt this "loss" goes away. But then there is also no real gain, because the ECU has figured out the adjustments to achieve the same target power output, likely at lower boost. Then you tune with whatever tune you want and make power more efficiently than if you still had the stock downpipes. Bolt on parts alone just don't make more power like they did on older turbo platforms without tuning to take advantage, but the fundamental physics still apply, so you can increase you ceiling or just make the same power more efficiently.

This is correct. Same goes for the good ole days when it was cold and you would make more power. Now the ecu would just lower boost to achieve that same programmed power.

However on a hot day it will raise the boost to hit the same power so it's a trade off with new technology.

[Info@mad-us.com]

Originally Posted by Nado

Thank you. But, the only difference is that the subject car has an actual tune, and not a piggyback? I have no doubt that with an actual tune DP will yield great gains.

Correct I was just trying to show the difference between catless and the best aftermarket catalytic converters made. Logs are an excellent way to compare.

[31shifter]

Many of the Ferrari guys wire their exhaust valves open or use a controller for the sound all the time, don’t blame them. But a few have proven on a dyno that their car made less TQ at lower rpm’s with valves open.

It’s a system with a lot of variables.

[Mcc420]

I did 11.2@124 stock and 10.9@126 with just dp’s.

[Fugazii]

Originally Posted by Mcc420

I did 11.2@124 stock and 10.9@126 with just dp’s.

Mine did a 00.00 @ 0 collecting dust until they crack it!