[Phil@BPC]

I know Bob has already posted this in another thread but wanted to create a separate one with more photos. This is a really cool E91 thats a 6 spd and had us swap the intake manifold to a 3 stage and replace the stock air box with a european air box with our tune. With each modification we saw horsepower and torque gains across the whole rpm range.

[Bufalo]

A 2WD wagon??? I was unaware such a creature existed on these shores...

[Phil@BPC]

Yep 2wd, 6spd with manual seats at that too!

[6ixSpd]

Yup, only in the US! Canada only got XDrive wagons.

Great gains across the power band. The car must feel noticeably faster to drive, that low-end torque boost is ridiculous.

You didn't do a run with the 3SM/airbox and without the tune, did you?

[W37V]

That's a beautiful e91. Almost makes me wish I got it than my e92.

But you know, 92>91 - am I doing this right?

[CobraMarty]

Very nice.

3IM+EURO+BPC Tune = +23.5HP and +34TQ.

229.7HP and 225.1TQ. Great numbers!

Next year- headers+PE+MILVs ?? 250+HP

[Eddiee07]

How much do the European air box and bpc tune cost? Just purchased the 3SIM but want to do everything at once

[E91Swagger]

Thanks for sharing, very nice manual RWD E91, rare bird indeed

[Phil@BPC]

Originally Posted by 6ixSpd

You didn't do a run with the 3SM/airbox and without the tune, did you?

We didnt dyno without the tune. You will need a tune to effectively use the 3 stage intake manifold. If you don't tune it you will just be making a lot of noise and no power.

[Phil@BPC]

Originally Posted by Eddiee07

How much do the European air box and bpc tune cost? Just purchased the 3SIM but want to do everything at once

Right now we have the tune on sale, on our webstore. Check it out because today is the last day for it!

https://bimmerperformancecenter.com/...i-n51-n52-tune

[atmosphericM]

Is it just me? I was expecting more. Honestly I thought a tune alone was producing these results for our car.. and was under the impression that the 3SIM alone provided pretty good gains (10 hp?). Now that I'm thinking about it though.. I'm wondering if practically every "tuned" car dyno I've seen also had a 3SIM bolted up. So is a tune only worth about 15hp and 3SIM another 10 (if tuned)?? I guess that isn't an awful $$-to-HP ratio, after all (about a grand for 25hp.. a lot better than my BMW PE lol!).

Also, what's up with the big drops in TQ/HP, post-tune, around 3200 and 4400 RPM?

I'm not trying to hate on BPC, obviously they are well-regarded among the community; however those curves leave a lot to be desired IMO due to how non-linear they are. I am no pro though so please take this for what it's worth. Again, not hating.

Originally Posted by Phil@BPC

We didnt dyno without the tune. You will need a tune to effectively use the 3 stage intake manifold. If you don't tune it you will just be making a lot of noise and no power.

What if you used some sort of "OE N51" tune? Or are you saying that my N51 does not use my 3SIM at all? Sorry, I am still trying to understand the whole idea. I'm guessing that there are too many other factors that would disallow one from using an N51 tune on an N52 motor though...

[Phil@BPC]

Originally Posted by atmosphericM

Is it just me? I was expecting more. Honestly I thought a tune alone was producing these results for our car.. and was under the impression that the 3SIM alone provided pretty good gains (10 hp?).

Also, what's up with the big drops in TQ/HP, post-tune, around 3200 and 4400 RPM?

I'm not trying to hate on BPC, obviously they are well-regarded among the community; however those curves leave a lot to be desired IMO due to how non-linear they are. I am no pro though so please take this for what it's worth. Again, not hating.



What if you used some sort of "OE N51" tune? Or are you saying that my N51 does not use my 3SIM at all? Sorry, I am still trying to understand the whole idea. I'm guessing that there are too many other factors that would disallow one from using an N51 tune on an N52 motor though...

Its ok

A tune alone will net about 16 hp and 15 ftlbs at the rear wheels. The euro intake and 3 stage intake will net the rest of the power made.

The dips in the graph are the normal characteristics of the 3 stage intake manifold. Each dip is the DISA valve opening allowing more air to enter the manifold.

[atmosphericM]

Thanks for the clarification! Can you comment at all on how the N51 utilizes (or doesn't utilize) the 3SIM? IIRC, my stock N51 did not produce such noticeable dips, but I could be wrong. *goes to look at plots*

[atmosphericM]

Ok sorry if this is a thread-jack but can you guys comment on how exactly the 3SIM works? I find the dips interesting and wonder why the 3SIM is the culprit. If it is simply a valve opening or an intake manifolds runner *lengthening*, why would a loss in power result, even if only momentary? Is the phenomena more like graph 1 or 2 below? Obviously 1 is a much better and more desirable situation. (Yellow line = tune only and Purple line = tune plus 3SIM)

BTW, grats to the owner. Definitely a sweet car and certainly respectable numbers especially for a station wagon.

[Phil@BPC]

Double post

[Bob@BPC]

Originally Posted by atmosphericM

Ok sorry if this is a thread-jack but can you guys comment on how exactly the 3SIM works? I find the dips interesting and wonder why the 3SIM is the culprit. If it is simply a valve opening or an intake manifolds runner *lengthening*, why would a loss in power result, even if only momentary? Is the phenomena more like graph 1 or 2 below? Obviously 1 is a much better and more desirable situation. (Yellow line = tune only and Purple line = tune plus 3SIM)

BTW, grats to the owner. Definitely a sweet car and certainly respectable numbers especially for a station wagon.

Its because the way the valves open and close, its an off / on switch.

Here's a stock 2006 330i (came with the 3 stage already installed) vs tuned. As you can see, even with the stock tune it still has those large bumps, unlike the vanos units where it has a variable adjustment so it can smooth out the power curve overtime. It looks similar to a honda b20, when the "vtec kicks in" you can see a large bump, since its just an on / off shift of the extra cam lobes.

[atmosphericM]

Thanks for the further clarification, BPC. To be clear, I wasn't trying to accuse your tune of creating the dips, just trying to wrap my head around what physically creates them. Thanks for being a part of the community and for all you guys do over there!

So what I am hearing is that the 3SIM has, obviously, 3 stages. And that the "dip" occurs when the IM adjust from one stage to the next. I am assuming that BMW's engineers have found that a smaller amount of air produces better results at low RPMs, and that as the RPM's rise, gradually (albeit only two graduations here lol) more air allowed into the motor can produce more power. So am I right in assuming that the dips in power are actually a result of, for at least a moment, *too much* air being allowed into the engine? I'm surprised that the engine's computer couldn't immediately make other adjustments (more fuel? VANOS? forgive me, I'm no expert when it comes to the more advanced features utilized today), therefore eliminating the "dip" and simply further increasing power. It almost looks to me like the engine's computer is having to "catch-up" once it realizes more air is present.. which of course I find quite odd given how fast computers are these days. Oh well, I'm sure there is a host of things going on here which are above my level of knowledge.

Again, thanks a ton for digging out that graph, Bob. Much appreciated.

[Bufalo]

The three stage IM works based on resonant induction, not necessarily by increased flow. By changing the effective length of the intake runners (by opening and closing DISA flaps) the resonant frequency of that intake runner also changes. By matching those resonances to the engine's rotation speed, a "ram air" effect is created, which aids in maximizing the volume of air entering the combustion chamber. The dips are based on changes in optimal resonance at those engine speeds compared to the resonance of the effective intake length.

Check this under the "Pressurisation" section - https://en.wikipedia.org/wiki/Variab...ntake_manifold

[6ixSpd]

Originally Posted by Phil@BPC

We didnt dyno without the tune. You will need a tune to effectively use the 3 stage intake manifold. If you don't tune it you will just be making a lot of noise and no power.

Oh yeah, durr. Total brain fart on my part.

[FlaPatsFan]

I also have a E91 2wd non-xdrive, manual seats. Unfortunately it’s automatic. Jealous of that beautiful 6spd!

[PhaseP]

Take a look at here at the picture especially at post #76

http://www.e90post.com/forums/showth...re+wave&page=4

And then here is my old post #92 where I tried to explain how I understand they are working:

http://www.e90post.com/forums/showth...e#post21858750

And see later in the thread CobraMarty's post #102 on the internal differences single stage and 3 stage manifolds. The perforated plate in the middle on singe stage is a "resistive, i.e. damping" element against air pressure wave.

Also I later noticed the length of the "runners" (if I am using the correct terminology) are chosen to optimize high RPM range. What I mean notice how each tube coming off the head are all same length and connect to a relative large volume horizontal plenum. The sudden transition from that tube to this relatively large volume would also cause a wave reflection. And being close to the intake valve this reflected wave will arrive back quickly. So at high RPMs this would/could be the helping resonance, and is same between the single and 3 stage.

Looks like a lot of thought, design, simulation looks like went into that manifold design to optimize performance. 3 stage optimized for max performance, single one detuned version but they opted for smoother engine curve since performance was being lost anyway.

[AWSB328iM]

Was there any exhaust on this car?