[Redrckt135]

been debating whether i wanted to do this or not. are the gains noticable, does it sound better? i also have a jb4 tune on it as well. any input is appreciated.

[FenixMike]

There are a few guys on N54tech running full setups, unfortunately the consensus (personally discovered as well) is that the single turbo on the N55 is just maxed out from the factory. You will get it to spool quicker with a downpipe and might pick up a few hp up top, but the only way guys are really making power with those is big exhaust and downpipe, intake, JB4 or similar, E85 mix and some of the guys have gone to larger intercooler setups and charge pipes, and even then the gains are VERY minimal up top where you need the power, most of it is just down low where you dont.

If you wanted to invest your money wisely though, get one of the upgraded turbos that have the larger impeller wheels in them, a good custom tune and a downpipe. You will make some SERIOUS power on that car and actually get your moneys worth instead of investing 4K in mods to gain 30-40 horsepower if youre lucky (almost ALL of the power gained on the N55 is below 4500 rpm, which is the point the factory turbo starts to run out of air and fall on its face, this is also completely useless power as youre out of 1st gear in under 2 seconds and never go below 5500 rpm again)

[Redrckt135]

Originally Posted by FenixMike

There are a few guys on N54tech running full setups, unfortunately the consensus (personally discovered as well) is that the single turbo on the N55 is just maxed out from the factory. You will get it to spool quicker with a downpipe and might pick up a few hp up top, but the only way guys are really making power with those is big exhaust and downpipe, intake, JB4 or similar, E85 mix and some of the guys have gone to larger intercooler setups and charge pipes, and even then the gains are VERY minimal up top where you need the power, most of it is just down low where you dont.

If you wanted to invest your money wisely though, get one of the upgraded turbos that have the larger impeller wheels in them, a good custom tune and a downpipe. You will make some SERIOUS power on that car and actually get your moneys worth instead of investing 4K in mods to gain 30-40 horsepower if youre lucky (almost ALL of the power gained on the N55 is below 4500 rpm, which is the point the factory turbo starts to run out of air and fall on its face, this is also completely useless power as youre out of 1st gear in under 2 seconds and never go below 5500 rpm again)

perfect answer, thank you for talking me out of a completely useless mod lol.

[lsturbointeg]

Originally Posted by FenixMike

There are a few guys on N54tech running full setups, unfortunately the consensus (personally discovered as well) is that the single turbo on the N55 is just maxed out from the factory. You will get it to spool quicker with a downpipe and might pick up a few hp up top, but the only way guys are really making power with those is big exhaust and downpipe, intake, JB4 or similar, E85 mix and some of the guys have gone to larger intercooler setups and charge pipes, and even then the gains are VERY minimal up top where you need the power, most of it is just down low where you dont.

If you wanted to invest your money wisely though, get one of the upgraded turbos that have the larger impeller wheels in them, a good custom tune and a downpipe. You will make some SERIOUS power on that car and actually get your moneys worth instead of investing 4K in mods to gain 30-40 horsepower if youre lucky (almost ALL of the power gained on the N55 is below 4500 rpm, which is the point the factory turbo starts to run out of air and fall on its face, this is also completely useless power as youre out of 1st gear in under 2 seconds and never go below 5500 rpm again)

Nice! Appreciate the info!

[Jayphil]

From the research and dyno I have seen, actually a downpipe over just Jb4 can result around 20 peak whp more which is not bad for the cost of it.

Stock car dyno around 265whp
Jb4 Stage 1 around 285-290whp
JB4 Stage 2 with cat less downpipe around 305-310whp.

Also based on dyno I have seen and gear ratio on a stage 2 optimal ship point are

Gear / Gear Ratio / RPM Start after shift / RPM shift
1 4,71 2500 6750
2 3,14 4500 6750
3 2,11 4535 6250
4 1,67 4946 6250
5 1,29 4827 6250
6 1 4844 6000
7 0,84 5040 6250
8 0,67 4985 6000


The result of JB4 and downpipe if you shift correctly based on the new lower RPM reality is you have around 40-45 more whp at any time during the acceleration. Much less than N54 but still very good for a around 1000$ of upgrade.

After that if you want a bit more next logical update is Pure or VTT stage 1 upgrade which is another 1000$ + 5-10hours of labor and will probably give you another 45whp and gain back your 6000+ rpms.

I will install JB4 and ER downpipe next month so I will update you about it and if my expectation were met.

[lsturbointeg]

Definitely let us know when I do!

[FenixMike]

Originally Posted by Jayphil

From the research and dyno I have seen, actually a downpipe over just Jb4 can result around 20 peak whp more which is not bad for the cost of it.

Stock car dyno around 265whp
Jb4 Stage 1 around 285-290whp
JB4 Stage 2 with cat less downpipe around 305-310whp.

Also based on dyno I have seen and gear ratio on a stage 2 optimal ship point are

Gear / Gear Ratio / RPM Start after shift / RPM shift
1 4,71 2500 6750
2 3,14 4500 6750
3 2,11 4535 6250
4 1,67 4946 6250
5 1,29 4827 6250
6 1 4844 6000
7 0,84 5040 6250
8 0,67 4985 6000


The result of JB4 and downpipe if you shift correctly based on the new lower RPM reality is you have around 40-45 more whp at any time during the acceleration. Much less than N54 but still very good for a around 1000$ of upgrade.

After that if you want a bit more next logical update is Pure or VTT stage 1 upgrade which is another 1000$ + 5-10hours of labor and will probably give you another 45whp and gain back your 6000+ rpms.

I will install JB4 and ER downpipe next month so I will update you about it and if my expectation were met.

Do you have the dynos to show that? Ive seen the 3 series and lower pick up decent power, but almost every 5 series (yes they are much different) pick up significantly less with the engine just checking out after 5K rpm. I dont know how much fun it would be knowing any time you wanted to go fast that you had to manually shift at a certain rpm to get your power, but it wasnt worth it to me so after the AFE Scorcher, I decided its get a 550 to mod, or leave my 535 with just the AFE.

[Jayphil]

Edit, just realized was in this forum
http://f10.5post.com/forums/showthread.php?t=595275

Originally Posted by jaekeem

I just wanted to share my personal experience now with this new downpipe from RSi Tuning. At the moment this is the only available downpipe for our N55 motors found on our F10 5-series. I must say this is just a remarkable mod for our cars given the amount of power gained all throughout the powerband.

Current mileage on car: 14,032 miles (JB has been on since 2,000miles)

Current power mods:
RSi downpipe
JB Stage 1 set at +4.5psi over stock
MXP prototype exhaust from e9x M3
K&N drop in panel air filter
91oct pump gas from Chevron

Stock vs. Current power mods


Dyno graph before and after RSi downpipe with the same boost setting


Power
The power gain is remarkable and if you take a close look at the RPM range the power increased its just too much fun to drive. We have the opportunity now to obtain comparable power goals the 135 and 335 owners have.

Torque
Net gain vs Stock: 64tq
Net gain with and without downpipe: 18tq

Horsepower
Net gain vs Stock: 46hp
Net gain with and without downpipe: 19hp

The total power gained from these modifications have increased my driving enjoyment easily ten fold. The peak power that was available with a stock motor is now available from 4300RPM and just continues to climb and hold steady all the way through redline. As for the available torque all I can say is that the car can now spin my BBS LM-R through first gear and a bit of second. I can definitely say that compared to stock this car really can get moving quickly.

Driveability & Sound levels
The driveability of the car remains untouched, I feel that the car is not loud at all with my current exhaust setup. If anything the downpipe is now letting my car breath which allows you to hear the turbo spool, and also gain that throaty/raspy sound. Its definitely got a much more aggressive exhaust note and does not drone at all. When cruising at freeway speeds its actually just a touch louder than stock.

I also had the opportunity to see, hear, and drive Alex's car (78mao) with the same downpipe and with a stock exhaust system, his car is pretty amazing as well. You can definitely hear the turbo spool better and has a similar sound to a 135i and a 335i. So this downpipe definitely does wonders even for those of you that are not interested in getting an exhaust system.

Future power mods:
Custom FMIC
Reinstallation of Meth injection kit
Increase JB Stage 1 boost to +6.0psi w/ Meth injection as advised by Terry
MXP Production exhaust system in full titanium

Final Thoughts
I have been on a quest for power since I first bought this car, and now I can finally say that I am satisfied with the gains this downpipe has provided. If anything this mod finally put good use to the other power mods I have installed and is just...awesome.

My short term goal is to reach 340hp with meth and the production MXP exhaust
Then when I get the chance I am going to try and reach 350hp with an FMIC

Shoutouts go out to the following people:
Daniel @ RSi Tuning
Steve & Tom @ EAS (European Auto Source)
Terry @ Burger Tuning
Alex for introducing me to Daniel
Jsyang15 for making me spend too much money on this car

[paul223]

Get the cat less downpipe. I have one. It will make a big difference in performance coupled with jb4 2. Some posts are simply not true here. lol

[FenixMike]

Originally Posted by Jayphil

Edit, just realized was in this forum
http://f10.5post.com/forums/showthread.php?t=595275

That one is a bit extreme... on top of all the mods and 93 octane, hes also running meth and 6 lbs more of boost! (where the turbo is able to make it) Most guys run 3-4 lbs tops on 93 and 3 on 91.

[FenixMike]

Originally Posted by paul223

Get the cat less downpipe. I have one. It will make a big difference in performance coupled with jb4 2. Some posts are simply not true here. lol

99% of BMW owners go off "feeling fast" to gauge power gains, so unless you have a dyno graph or some 1/4 mile slips to show gains, im just going by those who have actually supplied them and trying to save the guy some money.

[r33_RGSport]

Came across this thread. Here I share my F15 sDrive35i with JB4 Stage 2, Air Intake, ER prototype catless downpipe, ER Chargepipe, and RG Sport prototype muffler dyno result before and after the catless downpipe.

My mods portfolio http://f15.bimmerpost.com/forums/sho...d.php?t=967383

[Jayphil]

Originally Posted by FenixMike

That one is a bit extreme... on top of all the mods and 93 octane, hes also running meth and 6 lbs more of boost! (where the turbo is able to make it) Most guys run 3-4 lbs tops on 93 and 3 on 91.

If you read back his post you will see that for the dyno he was running

JB Stage 1
Downpipe
Exhaust
Drop in K&N...
91oct pump gas

So nothing extreme there... Not even JB4 (JB stage 1 only with more boost), no meth...

Originally Posted by r33_RGSport

Came across this thread. Here I share my F15 sDrive35i with JB4 Stage 2, Air Intake, ER prototype catless downpipe, ER Chargepipe, and RG Sport prototype muffler dyno result before and after the catless downpipe.

My mods portfolio http://f15.bimmerpost.com/forums/sho...d.php?t=967383

Thanks for your input, very impressive numbers. JB4 tune seems to have improved because early adopters have never achieved more than 310whp from dyno I have seen from 2011-2012. Maybe Burger started to work more on the maps when the F30 335I came in 2012 and now we are able to get similar gains like in the F30 body.

[FenixMike]

Originally Posted by Jayphil

So nothing extreme there... Not even JB4 (JB stage 1 only with more boost)

Out of curiosity, do you understand the difference?

[Jayphil]

Originally Posted by FenixMike

Out of curiosity, do you understand the difference?

It depends by to what extend your asking my understanding.

JB is a old version of the processor (called JB3) and is connected to less sensors. Generally JB stage 1 is less smooth and you have less control compared to JB4. In fact only have one map and you cannot upgrade it (except boost adjustments).

JB4 is the latest processor and connect to more sensor making a smoother power curve and generally able to gain a bit more HP. Also JB4 have specific MAP depending on modification (Map 1 for JB4 only, Map 2 for exhaust modification and 94 oct... So JB4 will give more power for car with Exhaust, intake mods etc.

So technically if the guy I posted his dyno would have been using JB4 on map 2 or map 5 he could have gained more whp over JB stage 1.

Make sense?

[FenixMike]

Originally Posted by Jayphil

It depends by to what extend your asking my understanding.

JB is a old version of the processor (called JB3) and is connected to less sensors. Generally JB stage 1 is less smooth and you have less control compared to JB4. In fact only have one map and you cannot upgrade it (except boost adjustments).

JB4 is the latest processor and connect to more sensor making a smoother power curve and generally able to gain a bit more HP. Also JB4 have specific MAP depending on modification (Map 1 for JB4 only, Map 2 for exhaust modification and 94 oct... So JB4 will give more power for car with Exhaust, intake mods etc.

So technically if the guy I posted his dyno would have been using JB4 on map 2 or map 5 he could have gained more whp over JB stage 1.

Make sense?

I understand them completely, I just find that many on this board dont understand that boost is boost (with respect to bringing timing into the equation, but lets keep this simple for now) and think automatically because someone has piggyback A, that piggyback B will add more power, or waiting for the magical piggyback C to come out that will offer even more magical horsepower somehow.

In this case, the stage 1 runs at 2.5-3 lbs as factory setup per Burger. The one in the link is running 4.5 lbs, which is usually what the JB4s run in factory form and really pushing it for 91 octane. Therefore, "not even JB4" may not even make much of a difference in power output, albeit there will be a difference in how the car responds with the abilities of other sensor interference.

What im trying to get at here is bench racing based on dyno numbers you found somewhere with the expectations that "well if he added XX parts, he would be even faster!" doesnt work. What does work is doing the parts yourself, strapping your car on a dyno (or going to the track for before and after results) and posting your results if you want a solid argument with me. 91 octane varies in content state by state with ethanol content, in addition elevation and temperatures make a huge difference. One guy picking up 30 with Combo A may yield a 10 horsepower loss on another car.

Whether or not he buys the downpipes wont affect my life in the slightest, im just trying to prepare him for the simple fact that he may (and likely) wont see significant gains for the investment hes going to put into it. If he wants a super loud race car and is looking forward to spending $3,000+ (more if hes not doing the labor) with the hopes of 30-40 horsepower, then more power to him. Ive always learned to never expect what the top guy gets, and sometimes more than the bottom guy, and in the end if thats still satisfactory, then make the investment.

Now what you also have to understand is the turbo on the 535s is severely limited by how much air it can physically push. Better fuels allow for more timing and/or boost where available, but overspinning a turbo out of its efficiency range isnt exactly the best idea if you want everything to last a long time, in addition without E85 or methanol, you are going to skyrocket intake air temperatures to where you not only lose power, but you make it dangerous. Things like downpipes and intakes do help for efficiency to get that last horsepower out of the turbo, but it still has limits.

Anyway, these parts typically never hurt, just make sure the payoff is worth the investment.

[superbuick]

One of the biggest drawbacks to a catless downpipe on an N55 is that the motor won't idle for very long before it stalls. You have to hit the gas slightly to bring the idle up or it stalls. This is a common issue if you do a little searching.

I have a DP on my 535, and I like the way it feels (I have dynoed it - was around 15hp max gain, I believe below 4500rpms but i'll have to dig out the graph. Video of one of the dyno runs is on youtube) but the stalling issue is a minor aggravation. I can't imagine how the guys with an automatic or whatever the other option is, wannabe F1 or whatever its called (smg? dct?), can run the downpipe and not have the stalling thing drive them crazy.

[paul223]

My 535i has never stalled. I put on down pipe and jb4 at 1200 miles, car has 21000 miles, not a single issue. I have flex fuel wires installed as well, run 50/50 gas & ethanol on map 7 for about 8k miles with no issue at all. Only issue I have rear tires burning up quicker.

[mike@x-ph.com]

N55 is maxed out from the factory ? What ?? !!!
Here is a dyno with the same engine. You can see stock power, versus map1 on a stock car versus map 2 with a car running catless DP versus map 7 on a car running catless DP and E85

[///M5Driver]

Originally Posted by mike@x-ph.com

N55 is maxed out from the factory ? What ?? !!!

Mike's right guys. Tons of misinformation here lol

[Jayphil]

Originally Posted by mike@x-ph.com

N55 is maxed out from the factory ? What ?? !!!
Here is a dyno with the same engine. You can see stock power, versus map1 on a stock car versus map 2 with a car running catless DP versus map 7 on a car running catless DP and E85
]

Mike, how would you compare power of a F30 vs F10 N55 (same transmission let say 8spd) do you believe we are able to achieve similar dyno results.

For some reasons 335I or 435I N55 dyno always show much higher number vs the F10 where we rarely see anything above 310whp.

Also from what I see from the dyno you posted is that once you have a tune nothing will be added past 6k rpm but you are still gaining peak HP but at much lower RPM vs stock curve (between 4.7K to 5.5K RPMs).

[mike@x-ph.com]

Originally Posted by Jayphil

Mike, how would you compare power of a F30 vs F10 N55 (same transmission let say 8spd) do you believe we are able to achieve similar dyno results.

For some reasons 335I or 435I N55 dyno always show much higher number vs the F10 where we rarely see anything above 310whp.

Also from what I see from the dyno you posted is that once you have a tune nothing will be added past 6k rpm but you are still gaining peak HP but at much lower RPM vs stock curve (between 4.7K to 5.5K RPMs).

Same engine and mods, dyno figures should be very similar for all 3