[RyderSU]

Hey guys, I was wondering, would I be able to get a downpipe in July/August and not tune it until March/April? Would this affect my car at all?

Or should I wait till I'm ready for a tune?

EDIT: The downpipe is the fabspeed Sport Cat Downpipe (catted obv), and also the Muffler Bypass by Fabspeed

[SeanWRT]

Short answer: no negatives other than emission none compliance which you may or may not care.

Long answer: short term trim will be adapting until long term one settle. You will have significantly louder exhaust note and improved turbo spool up for increased toque at low down and a bit mid range as well. At top end DME will adjust to pre set air filling to maintain peak output, so no power gained there.

Last word - down pipe power gain on stock tune is massively exaggerated by vendor. Even on flash it doesn't yield you a delta anywhere close to these claims, provided you're not modding crazily enough.

Good luck!

[eeyang92]

Originally Posted by SeanWRT

Short answer: no negatives other than emission none compliance which you may or may not care.

Long answer: short term trim will be adapting until long term one settle. You will have significantly louder exhaust note and improved turbo spool up for increased toque at low down and a bit mid range as well. At top end DME will adjust to pre set air filling to maintain peak output, so no power gained there.

Last word - down pipe power gain on stock tune is massively exaggerated by vendor. Even on flash it doesn't yield you a delta anywhere close to these claims, provided you're not modding crazily enough.

Good luck!

So a DP alone won't give me +20-30 HP/TQ? Is that mostly the flash/tune?

[No Boost]

Originally Posted by eeyang92

So a DP alone won't give me +20-30 HP/TQ? Is that mostly the flash/tune?

Fabspeed dynoed a stock M2 on their in-house dyno. 332/378 was acheived. With sport cat DP (and muffler bypass), 348/418 was acheived. Those are serious gains generated by a simple bolt-on exhaust component. Check out their website. I'm unable to copy the image on my shitty tablet. Anyone who has this DP highly recommends it, regardless of any subsequent tuning.

Keep in mind, you're running 91 CA fuel so the gains won't be as dramatic.

[PackPride85]

Any gains from just a DP is a result of a small increase in airflow or decrease in pumping losses at a given rpm. A 3-5 g/s increase over the rpm range wouldn't be unheard of depending on how restrictive the stock one is. Its a bit of inexact science to relate airflow g/s and hp but generally more airflow = more fuel = more power combustion at a given point.

The other effects are quicker spooling of the turbo and lower EGTs. These factors allow for more aggressive tuning.

I don't doubt the fabspeed graphs and I haven't looked at the details, but you have to take into account the ambient conditions between the two runs, as well as other factors in the DME such as: was it running max timing advance both runs? was overboost enabled on both?

[SeanWRT]

With all due respect, do not spread misinformation.

The 'air flow' as you mentioned is a pre turbo parameter measured by MAF sensor. Instead, our DME is really adjusting load by keeping MAP reading (measured post throttle) in check, which is completely irrelevant to turbo back design. To do that, wastegate, diverter valve and throttle plate are used at different times and different levels.

DP makes power by 1) improving VE with lower back pressure, which with our platform is only noticeable when power goes way beyond stock, 2) early spooling up, so turbo makes boost or power earlier than it would without dp.

When load target is hit (from 4k+rpm on stock tune) and DME starts to control power, DP isn't really helping, unless turbo couldn't achieve desired boost without DP, for example at elevation, or other kinds of bad condition.

I will stop going deeper, English skill is my restriction

[akkando]

Originally Posted by SeanWRT

With all due respect, do not spread misinformation.

The 'air flow' as you mentioned is a pre turbo parameter measured by MAF sensor. Instead, our DME is really adjusting load by keeping MAP reading (measured post throttle) in check, which is completely irrelevant to turbo back design. To do that, wastegate, diverter valve and throttle plate are used at different times and different levels.

DP makes power by 1) improving VE with lower back pressure, which with our platform is only noticeable when power goes way beyond stock, 2) early spooling up, so turbo makes boost or power earlier than it would without dp.

When load target is hit (from 4k+rpm on stock tune) and DME starts to control power, DP isn't really helping, unless turbo couldn't achieve desired boost without DP, for example at elevation, or other kinds of bad condition.

I will stop going deeper, English skill is my restriction

Is it worth getting one then if you plan to get a stage 1 tune? I assumed I would want DP and CP along with a stage 1 tune? But perhaps the DP isn't worth it.

[SeanWRT]

Originally Posted by akkando

Is it worth getting one then if you plan to get a stage 1 tune? I assumed I would want DP and CP along with a stage 1 tune? But perhaps the DP isn't worth it.

For just how much we care about turbo lag and exhaust note, I'd say downpipe is a worthy modification. In addition, it increases tuning headroom and improves durability (by reducing exhaust temperature).

The downside is the smell and emission which can be minimized by using HJS core, something I personally would and have done.

At the end of day cost is 1k+ USD, for a little more you can do a STG1 turbo OMG...

[akkando]

Originally Posted by SeanWRT

For just how much we care about turbo lag and exhaust note, I'd say downpipe is a worthy modification. In addition, it increases tuning headroom and improves durability (by reducing exhaust temperature).

The downside is the smell and emission which can be minimized by using HJS core, something I personally would and have done.

At the end of day cost is 1k+ USD, for a little more you can do a STG1 turbo OMG...

improves durability and turbo lag... those are big ones for me! Sound is bonus.

[Who?]

Originally Posted by SeanWRT

Last word - down pipe power gain on stock tune is massively exaggerated by vendor. Even on flash it doesn't yield you a delta anywhere close to these claims, provided you're not modding crazily enough.

have you got dynos to prove otherwise?

[Dav3]

Originally Posted by Who?

have you got dynos to prove otherwise?

Do you really need dynos when the same vendors claim Hp/Tq increase with their own aftermarket Air Filters or Charge Pipes?

It's just marketing that takes advantage of buyer ignorance and the placebo effect

This said, DP does indeed offer some benefits but the extent of the improvement to performance it provides is significantly tied to your other mods, primarily a flash tune/piggyback.

[Bee Pee]

Originally Posted by SeanWRT

With all due respect, do not spread misinformation.

The 'air flow' as you mentioned is a pre turbo parameter measured by MAF sensor. Instead, our DME is really adjusting load by keeping MAP reading (measured post throttle) in check, which is completely irrelevant to turbo back design. To do that, wastegate, diverter valve and throttle plate are used at different times and different levels.

DP makes power by 1) improving VE with lower back pressure, which with our platform is only noticeable when power goes way beyond stock, 2) early spooling up, so turbo makes boost or power earlier than it would without dp.

When load target is hit (from 4k+rpm on stock tune) and DME starts to control power, DP isn't really helping, unless turbo couldn't achieve desired boost without DP, for example at elevation, or other kinds of bad condition.

I will stop going deeper, English skill is my restriction

This post makes interesting reading

1st dyno stock 369/400 @ crank

2nd dyno DP upgrade stock tune 393/420 @ crank

3rd dyno more bolt ons stock tune 424/440 @ crank


http://www.babybmw.net/forum/posting.php?mode=quote&f=86&p=1405241

[SeanWRT]

I knew that thread long back. I think you misinterpreted the results.

Their stock baseline was 308ps on E30, uncorrected. And with a little heat soak as they say because that's the last run without DP.

On HJS 300 cell, the best they managed to get is 318ps, or a 10ps bump which is partially thanks to better IAT.

This link works better
http://www.babybmw.net/forum/viewtopic.php?t=84130

Originally Posted by Bee Pee

This post makes interesting reading

1st dyno stock 369/400 @ crank

2nd dyno DP upgrade stock tune 393/420 @ crank

3rd dyno more bolt ons stock tune 424/440 @ crank


http://www.babybmw.net/forum/posting...f=86&p=1405241

[Peasley]

Couldn't agree more with the above post.

I've just got home from having an HJS 300 cell DP fitted and there was a VERY noticeable improvement in throttle response and power on the drive back. It just seems to rev out more freely. This is coming from someone who didn't expect much at all.

[Peasley]

Originally Posted by GreatWhiteM2

Im assuming you experienced the following "gains"....

Low/mid range torque increase....Increased throttle response...Quicker spool up when getting back on the power....Better sounding exhaust?

All of the above

Although the exhaust noise was more subtle than I was expecting. Currently got the standard exhaust on there so a Milltek system may be next on the list.

[Bee Pee]

Originally Posted by SeanWRT

I knew that thread long back. I think you misinterpreted the results.

Their stock baseline was 308ps on E30, uncorrected. And with a little heat soak as they say because that's the last run without DP.

On HJS 300 cell, the best they managed to get is 318ps, or a 10ps bump which is partially thanks to better IAT.

This link works better
http://www.babybmw.net/forum/viewtopic.php?t=84130

Sean - different thread - yours refers to an m235i, the thread in my post is more recent and from an m2 owner - and different DP - m235i with 300cpi HJS DP v m2 with fab speed 200cpi DP- so I've not misinterpreted any of the following as its in plain speak....

I’ve attached my graphs,

first stock,



second DP+MPE+ITG Panel Filter,



third is with Wagner IC, HiFlow charge pipes, hi flow pure turbo inlet pipe.



All on same dyno.

Car has had zero ECU work, all the work/mods are just about breathing, it goes to show how good the N55 can run when it’s not restricted by a small IC, air filter, 600/800cel DP (cant quite remember stock) and skinny plastic pipes all of which have a tendency to crush under boost pressure.

The dyno in question is at Surrey Rolling Road here in the UK with very good rep.

This proves beyond doubt that m2 on stock tune responds well with the right combination of bolt ons......

BP

[SeanWRT]

I'm speechless. Are you trying to tell us M2 gains 54hp crank power out of just full Bolt-Ons?

Have you ever doubt a bit its legitimacy? It's exactly threads and people like these that is why all the marketing hypes have been going on and on.

I can show you a delta of 30whp on same day same car dyno, with no modification at all. What would that make you believe?

I can imagine how true tuners laugh out loud reading thread like this. Why am I even responding like I have a dog in this debate...why have I been consistent sharing anything technical at all...

Originally Posted by Bee Pee

Sean - different thread - yours refers to an m235i, the thread in my post is more recent and from an m2 owner - and different DP - m235i with 300cpi HJS DP v m2 with fab speed 200cpi DP- so I've not misinterpreted any of the following as its in plain speak....



The dyno in question is at Surrey Rolling Road here in the UK with very good rep.

This proves beyond doubt that m2 on stock tune responds well with the right combination of bolt ons......

BP

[Who?]

Originally Posted by SeanWRT

I'm speechless. Are you trying to tell us M2 gains 54hp crank power out of just full Bolt-Ons?

Have you ever doubt a bit its legitimacy? It's exactly threads and people like these that is why all the marketing hypes have been going on and on.

I can show you a delta of 30whp on same day same car dyno, with no modification at all. What would that make you believe?

I can imagine how true tuners laugh out loud reading thread like this. Why am I even responding like I have a dog in this debate...why have I been consistent sharing anything technical at all...

please do enlighten us with your dynos, until then, your word really holds no weight compared to the 'evil vendors' who provide these graphs

[SeanWRT]

Originally Posted by Who?

please do enlighten us with your dynos, until then, your word really holds no weight compared to the 'evil vendors' who provide these graphs

My words certainly don't hold same weight as yours. And my apologies man, I won't be repeatedly running with and without DP just to prove you guys gains or the lack thereof.

These days log is even a better tool to determine the power 'difference' than dyno sheet if you read and compare them many enough.

Move on and just be happy with what you believe, as we all do in our life.

All the best

[Who?]

Originally Posted by SeanWRT

My words certainly don't hold same weight as yours. And my apologies man, I won't be repeatedly running with and without DP just to prove you guys gains or the lack thereof.

These days log is even a better tool to determine the power 'difference' than dyno sheet if you read and compare them many enough.

Move on and just be happy with what you believe, as we all do in our life.

All the best

ofcourse my word doesn't hold weight, i'm not the one claiming and doubting without concrete evidence

[RyderSU]

So it's okay to do? Damn lots of people but it won't hurt me at all right with stock tune?

[PackPride85]

Originally Posted by GreatWhiteM2

Wow, just wow Sean!

This will be my last post on this because time and time again you simple cannot except others have achieved something you haven't in a certain way.

I was actually talking to a highly experienced engine builder/tuner yesterday about greater, sustained air flow on forced induction cars. It CAN make a huge difference on power results without mapping and YOU should know this given you preach tech data 24/7 on here.

As your posts seem to dictate you are technically minded, so my one point to make is these cars can actually OVERBOOST as a result of greater airflow, therefor resulting in a power increase!! I have seen it with my own eyes on my own car during the mapping stages when the airflow was increased without increasing the boost on the given map.

We can clearly see where the power has increased and for what duration, obviously the duration across the rev range is not as long compared to an actually remap but fact of the matter is, the power increased. Even when the final power run was done at the end of the session with greater intake temps.

Just because YOU haven't achieved said results it doesn't mean others cannot. Remember, "the stop watch never lies" Steve Sutcliffe. evo magazine

None of those dyno charts showed timing advance, boost, mass air flow, or IAT. Hard to I compare what the DME was doing w/o that data. On my last car (mazdaspeed 3) I saw about a 6 g/s increase throughout the rev but the dyno results were inconclusive other than the area where I saw boost spike (15-20whp). The real gains came when I was able to jack up the boost (under control) in the mid/upper rpm range.

Also, boost spikes can cause damage. It should be tuned out immediately.