02-23-2023, 08:23 AM | #1 |
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Catless DP = loss in whp/tq??
Featured on BIMMERPOST.com 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 |
02-23-2023, 08:38 AM | #2 |
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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:
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02-23-2023, 08:51 AM | #3 | |
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Hoping others will chime in, especially MAD themselves. |
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02-23-2023, 09:14 AM | #4 |
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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.
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02-23-2023, 10:16 AM | #5 | |
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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? |
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02-23-2023, 11:32 AM | #6 |
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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.
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02-23-2023, 11:40 AM | #7 | |
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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. |
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02-23-2023, 11:42 AM | #8 | |
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https://f30.bimmerpost.com/forums/sh....php?t=1982680
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Last edited by Info@mad-us.com; 02-23-2023 at 11:48 AM.. |
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02-23-2023, 11:48 AM | #9 | |
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We have seen some crazy hp numbers with the jb4 and flash platform using our downpipes.
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02-23-2023, 08:32 PM | #10 |
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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.
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02-24-2023, 08:33 AM | #11 | |
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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). |
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02-24-2023, 09:42 AM | #12 | |
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02-24-2023, 10:04 AM | #13 | |
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02-24-2023, 10:05 AM | #14 | |
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02-24-2023, 10:07 AM | #15 | |
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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. |
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02-24-2023, 10:42 AM | #16 |
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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.
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02-24-2023, 11:41 AM | #17 | |
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02-24-2023, 01:08 PM | #18 | |
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However on a hot day it will raise the boost to hit the same power so it's a trade off with new technology.
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02-24-2023, 01:10 PM | #19 |
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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.
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Last edited by Info@mad-us.com; 03-02-2023 at 10:03 PM.. |
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02-24-2023, 07:30 PM | #20 |
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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. |
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02-24-2023, 09:17 PM | #21 |
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I did 11.2@124 stock and 10.9@126 with just dp’s.
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