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      10-06-2017, 08:15 AM   #1
epiphanyray
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Catless Downpipes - With and Without Tune

So here are two questions. My Stock F10 M5 with just carbon filter delete and OEM downpipes roughly yields 509WHP and about 500WTQ after taking to dyno.

1)

If you then add downpipes (catless) with no tune and leave it as it, should it make a difference in WHP? I feel turbo spool in 2nd and 3rd Gear (low end) is faster and more responsive, without a doubt (or maybe its just that intoxicating sound of the turbo whistling and downshift cracking ). But ON a dyno - should this thing yield more WHP than stock?

2)

If I have a stage two flash (this was when I had OEM downpipes), should tuning company tweak this flash to account for Catless Downpipes now? What I mean is, does a flash tune take into account the fact that the car has Catless DP, and as a result yield even more power?

Everyone says Catless DP should probably increase your WHP by 20-35whp but I am assuming this is via tune, or should that happen naturally without tune?

thanks
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      10-06-2017, 12:18 PM   #2
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yeilds a small difference, i think 35whp is a stretch...

almost all the flash tuning guys will accommodate for the dp's
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      10-06-2017, 12:30 PM   #3
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Thanks Trevor. I only did one pull with catless downpipes, and it yielded 511 WHP (2 whp above 509WHP. Granted I did not even let the car cool down before using it in 95 degree weather and humidity at 99% lol.

So WHP did not vary with just Catless DP and NO TUNE.
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      10-07-2017, 09:53 AM   #4
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Quote:
Originally Posted by epiphanyray View Post
Thanks Trevor. I only did one pull with catless downpipes, and it yielded 511 WHP (2 whp above 509WHP. Granted I did not even let the car cool down before using it in 95 degree weather and humidity at 99% lol.

So WHP did not vary with just Catless DP and NO TUNE.
I think catless offers more power in the midrange because of more efficient turbo spool (area under the curve). I think tuners adjust the tune for secondary cat purposes, so you won't get a CEL.

To me, catless is more for sound (a glorious sound, undoubtedly) and a supporting mod for for turbos operating at max output.
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      10-07-2017, 09:55 AM   #5
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Quote:
Originally Posted by TheHouseWon View Post
Quote:
Originally Posted by epiphanyray View Post
Thanks Trevor. I only did one pull with catless downpipes, and it yielded 511 WHP (2 whp above 509WHP. Granted I did not even let the car cool down before using it in 95 degree weather and humidity at 99% lol.

So WHP did not vary with just Catless DP and NO TUNE.
I think catless offers more power in the midrange because of more efficient turbo spool (area under the curve). I think tuners adjust the tune for secondary cat purposes, so you won't get a CEL.

To me, catless is more for sound (a glorious sound, undoubtedly) and a supporting mod for for turbos operating at max output.
Agreed. However turbo spool and throttle responde in low-midrange is def. noticeable.
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      10-07-2017, 01:36 PM   #6
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Apples to oranges comparison for ya. The new 650 hp Zo6 Corvette only gains ~6 rwhp with the main cats deleted. Not a decent comparison, but it does show a rough trend.
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      10-07-2017, 02:29 PM   #7
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I just don't like the CEL with catless DP as stock the power is plenty. The car can barely get traction 1-3.

I am getting a CEL with my bms intakes too but the sound is just so intoxicating.

Do you guys think the downpipe help the turbo since they flow better? On my old 335s I always do the downpipes since they say it helps the turbo. Can this be considered a "reliability" mod for the s63tu turbos too you know....trying to justify buying them.
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      10-07-2017, 02:49 PM   #8
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Quote:
Originally Posted by E63amg View Post
I just don't like the CEL with catless DP as stock the power is plenty. The car can barely get traction 1-3.

I am getting a CEL with my bms intakes too but the sound is just so intoxicating.

Do you guys think the downpipe help the turbo since they flow better? On my old 335s I always do the downpipes since they say it helps the turbo. Can this be considered a "reliability" mod for the s63tu turbos too you know....trying to justify buying them.
The sound and fast spool response should be enough in my opinion.
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      10-07-2017, 02:52 PM   #9
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Quote:
Originally Posted by epiphanyray View Post
The sound and fast spool response should be enough in my opinion.
Do u hear the turbo whistle more ?

I just dont bother with tune because always you have some sort of problems. I am going to change my plugs and coils anyway but with tunes then misfires start that is not for me...I already played that game with the n54.

Btw do u hear the waste gates rattle more ?
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      10-07-2017, 02:59 PM   #10
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Quote:
Originally Posted by E63amg View Post
Do u hear the turbo whistle more ?

I just dont bother with tune because always you have some sort of problems. I am going to change my plugs and coils anyway but with tunes then misfires start that is not for me...I already played that game with the n54.

Btw do u hear the waste gates rattle more ?
Whistles like crazy. Before downpipes, I did not hear any whistle. After downpipes, the cracking, downshift burbles and overall sound is just intoxicating.

Get some headphones or speakers with bass and play this quick video. This was simply recorded with my iphone, and you can still hear the spooling whistle. It is much louder in person.

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      10-08-2017, 12:41 AM   #11
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Will definitely have an increase - but the increase is greater when tuned.

A tuned car with stock DPs will destroy a stock car with Catless DPs.

Basically the DPs are a complimentary modification to the tune. Think of the engine as an air pump, air goes in and out. With stock software, you’re pushing less air - so the restriction on the back side is less than it would be if you were forcing more air in.
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      11-13-2018, 04:58 AM   #12
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Reviving an old thread I guess...

I just got catless DPs on my F10 M5 (VRSF DPs) and I felt the power increase when the car adapted to the DPs.

I can safely say the car gained 30 WHP with stock tune and stock everything else. It is my first mod at the moment.

As everyone else said, the spool sound, pops and the burble are intoxicating!
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      11-13-2018, 10:15 AM   #13
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^get a stage 2 tune. It gets even better
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      11-13-2018, 11:59 AM   #14
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The difference between a proper tune on a stock car and a proper tune on a car with catless downpipes is minimal. Our stg1 tune alone get you 630-650whp on 93oct. Adding down pipes and a tune that defeats emissions diagnostics won’t get you much more than noxious stink and a lot more noise.

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      11-13-2018, 12:43 PM   #15
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Quote:
Originally Posted by OpenFlash View Post
The difference between a proper tune on a stock car and a proper tune on a car with catless downpipes is minimal. Our stg1 tune alone get you 630-650whp on 93oct. Adding down pipes and a tune that defeats emissions diagnostics won’t get you much more than noxious stink and a lot more noise.

Cheers
Shiv
Is your office in CA or something?
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      11-13-2018, 01:27 PM   #16
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Is your office in CA or something?
It certainly is. However, my statements are equally valid in other geographical regions as well
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      11-13-2018, 06:35 PM   #17
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Quote:
Originally Posted by OpenFlash View Post
It certainly is. However, my statements are equally valid in other geographical regions as well
More like an opinion
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      11-13-2018, 07:23 PM   #18
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653whp with only a 93oct tune (no other mods): https://f10.m5post.com/forums/showthread.php?t=1554578

The only real advantage of running cat-less downpipes is for racing applications where you can disable all the ECU's catalyst protection strategies that would otherwise drop boost and enrich AFR when calculated catalyst temps get high (ie, sustained top speed runs or hot lapping at the track). But for 99% of us, this doesn't apply. On the street, the s63tu can make as much peak power as you can reasonably want with stock DPs.

Catless DPs, in other smaller displacement platforms, can be useful since they speed up turbo response time and improve low end/midrange torque. But in the case of the s63tu, boost response is already excellent and most competent tuners will already be limiting low end/midrange torque anyway to preserve transmission/engine integrity. So I fail to see where running cat-less downpipes provide any real advantage for most of us.

But if you like the extra noise, expense, stink and the thrill of breaking the law and polluting the air we breathe, who am I to say otherwise?

I'm just trying to provide realistic expectations as to what to expect in terms of actual performance gains.

Cheers
Shiv
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      11-14-2018, 12:05 AM   #19
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Don't mean to hijack the thread but to give you more info on this topic. Here are my Dyno Charts for my car (DP with stock tune)
https://f10.m5post.com/forums/showthread.php?t=1555049
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      11-14-2018, 09:50 AM   #20
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Quote:
Originally Posted by OpenFlash View Post
653whp with only a 93oct tune (no other mods): https://f10.m5post.com/forums/showthread.php?t=1554578

The only real advantage of running cat-less downpipes is for racing applications where you can disable all the ECU's catalyst protection strategies that would otherwise drop boost and enrich AFR when calculated catalyst temps get high (ie, sustained top speed runs or hot lapping at the track). But for 99% of us, this doesn't apply. On the street, the s63tu can make as much peak power as you can reasonably want with stock DPs.

Catless DPs, in other smaller displacement platforms, can be useful since they speed up turbo response time and improve low end/midrange torque. But in the case of the s63tu, boost response is already excellent and most competent tuners will already be limiting low end/midrange torque anyway to preserve transmission/engine integrity. So I fail to see where running cat-less downpipes provide any real advantage for most of us.

But if you like the extra noise, expense, stink and the thrill of breaking the law and polluting the air we breathe, who am I to say otherwise?

I'm just trying to provide realistic expectations as to what to expect in terms of actual performance gains.

Cheers
Shiv
Slippery slope. Comes down to preference and choice--and opinion. Dyno numbers of stage 2 vs. Stage 1 are well-documented. You're saying stage 1 is adequate for most m5 owners, I'm saying I prefer more power and more noise (otherwise, what's the point of aftermarket exhaust?). If we cared about adequate performance we would have left the car stock.

Do dp's give a ton of power? No. Do they contribute to the longevity of the turbos? Most likely. Does the turbo whistle sound cool? Definitely.

If you're concerned about the environment make sure to call out those polluters at the next car meet. When you were at Burger Tuning** no one ever criticised the polluters and promoted the CEL bypass capability like there was no tomorrow. After you left and set up shop in CA and BMS was fined, all of a sudden "dp's are a waste of time and money." Just look at the tone over at n54 tech.

**Correct me if you weren't at BMS, I will retract my comment about that.
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      11-14-2018, 10:20 AM   #21
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Originally Posted by TheHouseWon View Post
Slippery slope. Comes down to preference and choice--and opinion. Dyno numbers of stage 2 vs. Stage 1 are well-documented. You're saying stage 1 is adequate for most m5 owners, I'm saying I prefer more power and more noise (otherwise, what's the point of aftermarket exhaust?). If we cared about adequate performance we would have left the car stock.

Do dp's give a ton of power? No. Do they contribute to the longevity of the turbos? Most likely. Does the turbo whistle sound cool? Definitely.

If you're concerned about the environment make sure to call out those polluters at the next car meet. When you were at Burger Tuning** no one ever criticised the polluters and promoted the CEL bypass capability like there was no tomorrow. After you left and set up shop in CA and BMS was fined, all of a sudden "dp's are a waste of time and money." Just look at the tone over at n54 tech.

**Correct me if you weren't at BMS, I will retract my comment about that.
You are mistaken. We have nothing to do with BMS. I don’t even understand what you are referring to. What makes you think that anyone here has worked there? All of us here have been in the tuning business for longer than that company has been around

Last edited by OpenFlash; 11-14-2018 at 03:15 PM..
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      06-26-2020, 04:37 AM   #22
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Quote:
Originally Posted by RAFiK - BMWClubUAE View Post
Reviving an old thread I guess...

I just got catless DPs on my F10 M5 (VRSF DPs) and I felt the power increase when the car adapted to the DPs.

I can safely say the car gained 30 WHP with stock tune and stock everything else. It is my first mod at the moment.

As everyone else said, the spool sound, pops and the burble are intoxicating!

Did you get a check engine light on with the catless downpipes?
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