[Juiced46]

Went to the dyno yesterday to see what type of gains I got with the N55 AR downpipe. The results were very surprising to say the least. Obviously this was not done on the same day which will affect results slightly.

Mods before AR DP:
JB3 Beta Tune
AMS 3" Catback

Only thing added was the AR Downpipe from the previous dyno session. Also, dont mind on the graph where it says MAP 5, its MAP 1 as the JB3 for the N55 only has one MAP.

Here are the results.



Only a 3whp gain PEAK and a 9wtq loss. However as you can see the car picks up a good 10-25whp above 5500 RPMs, where as before it would fall, but it did nothing for peak #s. All in all, not depressed with the #s, but alittle surprised with the outcome. I absolutely love the sound, and the fact I have more power above 5500, I just wish it would have given more power across the board. IMO I think the 4" DP is just to large for this small of a turbo. I think a 3" or 3.5" (catless) would be perfect to get the TQ #s up and still be able to make more power up top without it falling.

[Mike@N54Tuning.com]

Did you only do one run on each?

Mike

[Juiced46]

No, we did 3 pulls stock with catback, then 3 pulls with jb3 and catback, then 3 pulls with the jb3 , catback and dp. Pre dp #s were all within 5hp/tq of each other, first pull with the Ar dp was 281/315. I posted the best runs of each

[secretsquirrel]

Huh? I don't know much about n55 dps (like everyone) but im very very surprised to see this. Also, I'm not sure how a dp could be too big on a turbo car.

[Mike@N54Tuning.com]

Can you post all the curves? I am just trying to get an idea of run to run variance as this is a little surprising.

Mike

[tscdennab]

So the N55 stock catalytic converter is not that restrictive. This can be good but mostly bad for squeezing the most power out of the engine...

[jblackwell]

I'm not surprised at all. It's pretty, but I didn't expect much at all. Running higher boost and meth with the stock downpipe and then the AR would likely show a more dramatic increase.

[ar design]

Originally Posted by Juiced46

Went to the dyno yesterday to see what type of gains I got with the N55 AR downpipe. The results were very surprising to say the least. Obviously this was not done on the same day which will affect results slightly.

Mods before AR DP:
JB3 Beta Tune
AMS 3" Catback

Only thing added was the AR Downpipe from the previous dyno session. Also, dont mind on the graph where it says MAP 5, its MAP 1 as the JB3 for the N55 only has one MAP.

Here are the results.i



Only a 3whp gain PEAK and a 9wtq loss. However as you can see the car picks up a good 10-25whp above 5500 RPMs, where as before it would fall, but it did nothing for peak #s. All in all, not depressed with the #s, but alittle surprised with the outcome. I absolutely love the sound, and the fact I have more power above 5500, I just wish it would have given more power across the board. IMO I think the 4" DP is just to large for this small of a turbo. I think a 3" or 3.5" (catless) would be perfect to get the TQ #s up and still be able to make more power up top without it falling.

As with the n54, tune needs to be adjusted to make use of headroom provided by downpipes. I know Terry will be looking into this as we are sending him a pipe to test.

[cn555ic]

Wow gains seemed to be not as much as the N54 DPs.

[Juiced46]

Originally Posted by secretsquirrel

Huh? I don't know much about n55 dps (like everyone) but im very very surprised to see this. Also, I'm not sure how a dp could be too big on a turbo car.

Well, bigger is not always better. Obviously backpressure and exhaust size plays a HUGE role in turbo spool up, power etc. On this small of a turbo IMO I think is to large.

To put it into perspective for you. I run a 76mm turbo on my mustang (which dwarfs the turbo on the BMW). If it still had the 6spd in it, it would put down approx 900-950rwhp. I still run a 3" DP. I would benefit from a 4" DP alittle, I would sacrafice a little spool but I will pick up power up top, but peak TQ would drop. Ive tested this previously on a car with the same setup. Another example, on this same 76mm turbo. I used to run a .81 exhaust housing on the turbo. This setup produced 730rwhp/800rwtq. I wanted the .81 housing to help spool up, but power was dropping above 6000rpms. I then switched to a .96 housing on the turbo (bigger) The car still peaked 730rwhp, however I lost 100ftlbs which dropped me to 700rwtq, but the power falling off up top now held to 7000rpms instead of falling @ 6000.

With the 4" DP on the N55 I think it is creating to much of a loss in backpressure causing the TQ #s to drop and not come on as hard. I think a 3-3.5" would be a happy medium.

Originally Posted by Mike@N54Tuning.com

Can you post all the curves? I am just trying to get an idea of run to run variance as this is a little surprising.

Mike

Mike. I do not have all of the curves on the database. I only have 1 stock pull, 2 pulls with the JB3/AMS, and 1 JB3/AMS/AR DP. However the pulls are all on the dyno computer which would need to be uploaded to the database online so I can get them all. As far as run to run variance, there isnt much. The 315wtq pull was actually with no load on the dyno. (forgot to turn it on) However all other pulls, including the stock pulls, and AR DP pulls were done loaded.

Originally Posted by maxnix

Thanks for posting. Might be more informative if you had done pulls with stock tune also.

I did pulls with the stock tune vs JB3, I have those on record. I didnt do stock w/o JB3 and with the AR DP though. Didnt feel a need for that.

Originally Posted by tscdennab

So the N55 stock catalytic converter is not that restrictive. This can be good but mostly bad for squeezing the most power out of the engine...

Well I wouldnt say its not that restrictive. Its not picking up PEAK power, however after 5500 you can see it picks up from 15 to almost 30whp where power used to drop with the catted DP, which is a good gain. However that doesnt show up on the peak #s though

Originally Posted by jblackwell

I'm not surprised at all. It's pretty, but I didn't expect much at all. Running higher boost and meth with the stock downpipe and then the AR would likely show a more dramatic increase.

I agree, running higher boost may show more of a gain, it all depends on what boost level the stock DP REALLY starts becoming a restriction.

Originally Posted by ar design

As with the n54, tune needs to be adjusted to make use of headroom provided by downpipes. I know Terry will be looking into this as we are sending him a pipe to test.

How much more of adjustment are you guys doing on the N54 with DPs? More timing/af adjustments? AF compared to pre DP was very close in most of the pull, the biggest variance was .5 richer with the AR DP in a few spots compared to the stock DP, mainly above 5500rpms.

[shockin330i]

subscribing

[e93WhiteonRed]

Originally Posted by ar design

As with the n54, tune needs to be adjusted to make use of headroom provided by downpipes. I know Terry will be looking into this as we are sending him a pipe to test.

Too bad you weren't running with a tune that autotunes. It would have been interesting to see what it could have squeezed out of it.

[shockin330i]

Here are my two dp runs. I know I fail for not getting a baseline.

[BrianMN]

Originally Posted by shockin330i

Here are my two dp runs. I know I fail for not getting a baseline.

What in the world is going on with that torque curve?

[shockin330i]

Originally Posted by BrianMN

What in the world is going on with that torque curve?

I have no idea, but its super gay. And not homosexual gay, but your parents are chaperoning your school dance gay.

Shiv had the same problem with his baseline...

[BrianMN]

Originally Posted by shockin330i

I have no idea, but its super gay.

Do you feel that while driving? What tune was that with? Or was it stock?

Edit: Also, those A/F ratios are in the 15:1 range, finally getting lower than 14:1 at 4500!

[shockin330i]

Originally Posted by BrianMN

Do you feel that while driving? What tune was that with? Or was it stock?

Edit: Also, those A/F ratios are in the 15:1 range, finally getting lower than 14:1 at 4500!

Stock no tune.

[shockin330i]

terry has the same dip..

[BrianMN]

Originally Posted by shockin330i

Stock no tune.

Ok yeah I wasn't sure if your new car was an xi on a mustang or what the deal was...

Anyways, that seems very strange for a stock car to run that tq curve and that A/F ratio....

Are you able to feel that 50tq drop in power for all of the 3,000-4,000 range?

[shockin330i]

Originally Posted by BrianMN

Ok yeah I wasn't sure if your new car was an xi on a mustang or what the deal was...

Anyways, that seems very strange for a stock car to run that tq curve and that A/F ratio....

Are you able to feel that 50tq drop in power for all of the 3,000-4,000 range?

I'm never really in that rpm range under full throttle. The car seemed to run very lean. I mean they run lean, but damn..

Here are my Procede map 1 runs. Car was literally on the dyno back to back to back runs.
93 exxon(which I'm coming to the conclusion that my car hates) Car hadn't fully adapted yet, at least I think...

[themyst]

So basically we can conclude that downpipes aren't worth the money on an N55. I am really disappointed in the power potential on this platform in comparison to what the N54 guys accomplish.

[BrianMN]

Wow, yeah lean is mean but not at the cost of burning thing up, haha. Hopefully the tuned AFR's looked better? I mean 15:1 under full boost (even if stock 7-8psi) just doesn't seem right.

The tune dyno still shows that sag in the 3-4k range... Now is this engine the Valvetronic engine? (No throttle body) Perhaps that will need a bit of tuning to allow it to deviate from stock logic, which is generally based on emissions and fuel economy.