One of the pillars of internal combustion engine tuning is improving flow on both sides of the valvetrain. Whether it’s getting more cool air in or pushing exhaust out as effectively as possible, both boost efficiency, and more efficiency means more horsepower.
When it comes to intake modification, not much beats individual throttle bodies (ITBs) on a naturally aspirated engine to get more air in as efficiently as possible and to boost overall theatrics—who can deny this design’s deeper and more pronounced intake sound? However, these are a typically costly aftermarket modification, and then tuning the engine’s ECU to work with them takes a lot of effort.
However, modern BMWs that are equipped with Valvetronic intake technology play by a different rulebook. In fact, thanks to Washington-based aftermarket tuning company 22RPD, taking advantage of this induction system that doesn’t rely on a throttle body means Valvetronic owners can achieve a setup that should offer many of the advantages of ITBs (a smaller air path into each cylinder), yet for far less money and in a much more convenient way. Let’s dive into exactly how.
What is Valvetronic?
Many BMWs produced since 2006 sport this fascinating technology: In a quick sentence, air flow is regulated by the valves themselves, not the throttle body—though, a single throttle body for all cylinders is still there in case the Valvetronic system malfunctions. This means there’s a lot more going on under the valve cover, which Jason Fenske of Engineering Explained does a great job at laying out in this video.
The BMW N52 is a naturally aspirated 3.0-liter inline-six that sports Valvetronic, which lives under the hood of my beloved 2011 BMW 128i. Thomas Hundal’s also got it under the hood of his E90 325i, too; we’ve nerded out over this aluminum-magnesium lump of German excellence quite a bit over the years.
It’s a torquey, rev-happy six that produces around 230 horsepower and 200 pound-feet of torque from the factory. In fact, its rev-happiness is thanks in part to Valvetronic: Instead of waiting for air to enter the intake ports when the throttle body opens up, it’s already there, rarin’ to get sucked in.
Raimund on YouTube
How This Offers Many Advantages Associated With ITBs
So, because Valvetronic doesn’t need a throttle body, it can theoretically be completely deleted from the equation via aftermarket tune. Not only that, but it’s possible to delete the mass airflow (MAF) sensor as well, and run it like factory BMWs do in Europe. As Thomas Hundal explains in solid detail, “Euro-spec N52s measure air density using the differential between manifold pressure and atmospheric pressure. The intake air temperature (IAT) sensor is one component the ECU uses for fueling, but much of the heavy lifting is done via differential pressure (with a MAP sensor in the manifold) and closed-loop oxygen sensor operation.”
Thus, fewer components between the intake ports and the outside world.
Which is similar to an ITB setup, except there are no throttle body valves at all. Enter 22RPD,out of Renton, WA — a shop that has designed an intake manifold consisting of open intake runners—dubbed velocity stacks in this instance—for each cylinder that resemble ITB trumpets. Check it out:
Before you take off down to the comments and condemn this design for lacking a filtration element and being bathed in engine heat, don’t fret, the pictured setup is just a prototype—the company says the final product will include a filter and proper housing to draw in cool air.
Its design is more than just throwing some tubes over the intake ports, too. The runners have been optimized for flow, and actually looks quite similar to a turbocharged BMW N54 engine’s intake runners. That’s another modification that the N52 crowd’s taken a shine to: Modifying and fitting the intake manifold from the N54 for its shorter runners, which gives the naturally aspirated fare a decent bump in peak horsepower, though reduces output low in the rev band.
The Upsides and Downsides
Depending on aftermarket ECU (er, DME because its a BMW) tuning, 22RPD’s trumpets could result in a very healthy power increase, especially when combined with aftermarket exhaust headers and MILVs (modified intake lift Valvetronic support), which increase intake lift and duration like an aftermarket camshaft. Since 22RPD specializes in remapping stock MSV70 and MSV80 DMEs, running this assortment of hardware won’t require aftermarket engine management hardware, saving interested owners some serious coin.
With just this selection of mods, 261 wheel-horsepower and 231 wheel-torque is allegedly possible. Not bad, not bad at all.
This intake arrangement boosts throttle response, the engine’s ability to rev up even quicker, as well as make for an excellent intake soundtrack. Who doesn’t love a deep-breathing NA engine, especially of the inline-six BMW variety?
There could certainly be some downsides of this throttle body-less intake (which has been discussed for years; see e90post forum post above). Remember: The engine still has a throttle body there from the factory in case the Valvetronic system malfunctions … so what happens if it malfunctions and there’s no backup? Once again, N52 technical wizard Thomas Hundal points out that “if the eccentric shaft locks at full lift without the throttle body in place, the engine will just bounce off the rev limiter until the ignition’s switched off. While there is some possibility of sudden unintended acceleration, most people who are in deep enough to consider this mod will have the skills to diffuse a situation like that.” We reached out to 22RPD, and the tuning company responded that “the fail safe is now controlled by the Valvetronic sensor,” meaning that the Valvetronic system’s own monitoring equipment should act as a failsafe.
[Ed Note: This actually sounds potentially dangerous, though I’m curious what mitigation strategy 22RPD has in mind; I’ve sent an email asking, and will update this article if I hear back. In the meantime, here’s a look at the company’s Feb 17, 2024 blog post titled “THE FUTURE OF NA N52 : NO THROTTLE BODY [BONUS: BETA TESTING SIGN-UP]“:
The BMW N51 and N52 engines, renowned for their reliability and perhaps weight but lets be honest, have long been overlooked among enthusiasts and professionals alike. However, every engine has untapped potential waiting to be discovered. It is with great excitement that we introduce this untapped potential, this new new intake and tune from 22RPD. A product that not only redefines performance capabilities, but also ushers in a new era of N5X performance.
Innovation is at the heart of the 22RPD, and it’s what sets us apart from everyone else on the market. The choice to develop this package to operate without a throttle body, is substantially innovative. This innovative design leverages the full potential of BMW’s Valvetronic system in a new way, using it exclusively to manage engine breathing. Without the throttle body, we have removed a significant restriction in the intake tract. The result? Substantial gains.
This design doesn’t stop at just removing restrictions. It introduces a meticulously engineered trumpet design that surpasses the popular N54 intake and three-stage (3IM) intake in both average and peak power output. Through comprehensive engineering and testing we have developed an improved runner shape and optimized length. Thus enhancing the engine’s ability to breathe effortlessly at higher RPMs while optimizing resonance for midrange power improvements. This design not only optimizes performance but also eradicates common failure points associated with the 3IM intakes and DISA’s, ensuring reliability and longevity. Also, as a small bonus the trumpets save 30lbs or so off the nose of the car, optimally.
The revolutionary design behind the 22RPD intake owes its genesis to the extensive groundwork laid with the recent S65 and S85 intakes design by 22RPD prior, combined with sophisticated flow modeling (CFD) techniques. These runners are the culmination of all our efforts across various platforms, representing an evolution in our approach to intake design. We began with fundamental calculations for resonance and runner length. This was followed by 3D scanning the OEM N52 intakes to serve as our baseline reference. With this foundation, we determined an optimal taper figure and initiated modeling of the base geometry. Through several iterations, guided by both modeling insights and CFD analyses, we refined our design before advancing to real-world testing and iterative design on multiple cars.
The proof, as they say, is in the pudding-or, in this case, the dyno tests. Rigorous testing has demonstrated that the 22RPD package delivers significant performance gains everywhere that counts. These gains are not just numbers on a chart; they translate to real-world enhancements in acceleration, throttle response, sound, and overall engine efficiency. For BMW N51 and N52 engine owners, this means experiencing a new level of performance and sound that was previously thought to be unattainable by the little brother of the n54. See the dyno graph below showing the gains with the Bavautoparts 330i.
The 22RPD custom intake and tune package represents more than just an increase in horsepower and torque. It embodies a philosophy of innovation, reliability, and performance. By removing the throttle body and optimizing the Valvetronic system, 22RPD not only enhances power but also reduces complexity and potential failure points within the engine. This approach ensures that your BMW’s heart is not only more powerful but also more robust and dependable.
For the discerning BMW enthusiast looking to extract the maximum potential of sound and performance from their N51 or N52 engine, the 22RPD custom intake and tune package offers an unrivaled solution. Its innovative design, backed by solid engineering and real-world testing, sets a new benchmark in N52/N51 performance tuning.
What is Party Mode? Why do you keep saying it?
The “Party Mode” Intake by 22RPD where we throw caution to the wind, filters out the window, and let your engine run wild and free, just as nature (or the automotive gods) intended. Picture this: an intake so raw, so untamed, it scoffs at the mere thought of air filtration and laughs in the face of safeties, all in the noble pursuit of substantial gains. But, dear thrill-seeker, let’s not forget that with great power comes great responsibility. While embarking on this euphoric journey of unfiltered performance, remember that every party has its end, and not all engines enjoy the hangover. So, consider this your cool yet cautionary tale: embrace the exhilaration of “Party Mode,” but be mindful of the morning after. Here’s to living fast, but maintaining enough sense to ensure your ride can keep up with the pace. And let’s remember, 22RPD is not responsible for the aftermath; you take full risk, stepping into the party with both eyes open to the wild ride ahead.
What’s on the Horizon? Upcoming Milestones:
PARTY MODE Beta test Phase: March 1 – April 1
Cold Air Feed/Filter Design Period: February 21 – March 14
Public Release of PARTY MODE INTAKE: April 1
Testing of Fitment on Filter Design: March 14 – April 14
Anticipated Release of Filter and CAI Design: May 1
Anticipated pricing for BETA trumpets and tune is $995. If we make any changes for a final product, exchange towards the final product will be allowed. Exchange towards a filtered unit will be allowed.
Ready to join the Evolution? Sign up for our beta program below and be the first to experience the raw, unfiltered bliss of 22RPD’s “Party Mode” intake. It’s not just about making your engine louder; it’s about making your heart race faster. So, strap in, turn up the volume, and let’s make some noise.
The short of that blog post: The setup promises to reduce weight, improve reliability, and increase engine response thanks to reduced restriction and optimized runner design (optimized, specifically, for mid-range RPM (read this to learn more about how velocity stack length affects performance at different RPMs). I myself have concerns about pulling hot underhood air into the engine, and I wonder about that loss of a throttle body failsafe, but maybe there are plans for those. -DT].
[Editor’s note: 22RPD responded to our inquiry on intake air temperature with its findings, and the open trumpets reportedly make less of a difference than you’d expect. As per 22RPD: “not that we have seen, both Dyno and street testing has shown similar AIT and even slightly lower due to the lack of an airbox that the “cold/fresh” air needs to travel through, and we are using the N54 ducts to get that air to the stacks.” — TH]
I’m quite excited to see what 22RPD comes up with for a finished project, and it’s clear a lot of you are, too:
It’s so cool that one can exploit the well-flowing N52 like this, and hopefully the bump in horsepower—and overall soundtrack—will be substantial and awesome.
36 thoughts on “A Tuner Is Working On A ‘Velocity Stack’ Mod For Modern BMWs And Lots Of People Are Pumped”
22RPD is pretty legit, PO of my ’83 533i with a ’91 M30B35 swap had them dyno tune it and with nothing more than an exhaust and “cold air” intake they pulled 22 hp out of it and even more torque.
I’m torn on this-on one hand super cool and will sound rad but on the other hand that’s a big investment of time and money to make 15 extra hp at 7100 rpm with a tiny bit of a smoother fatter curve in the midrange will be barely (if at all) noticeable in normal driving since there’s only a 4 lb/ft increase. And it looks like those gains were on top of engine that already had headers and exhaust plus you’re getting a dyno tune to make any of it add anything which at least at RPD iiirc is right around $1K. Honestly the baseline pull at 255 hp at the wheels on an engine that was rated in everything but the Z4 3.0 SI at 235 flywheel is the real story here.
This reads a bit too much like you copy pasted an ad – how is recreating what was sold on the exact same chassis in other markets a decade ago “substantially innovative”, italic emphasis theirs? Did you really need to copy all that over?
Seems like Valvetronic could use a short feature article of its own, I’d never heard of varying intake valve lift instead of using a throttle butterfly. That sounds very cool and also very fussy.
Would be interesting to touch on why the US version added a MAF. I can guess (EPA compliant limp-mode) but it could prompt some fun insight into differences between US and EU approaches to safety and cleanliness.
I’m quite aware of VVT technologies which operate on a limited range of lift/phasing changes, often just in a couple of settings.
Continually varying valve lift from 0-100% to meter intake fuel/air is rather more dramatic, and is new to me. I’d only expect to see that on a camless engine.
Why mod a normal BMW engine, when you just get a proper ///M which already has individual throttle bodies, rather trust BMW engineering vs a knockoff assembly and all the other complication. BMW ITB’s are a thing of beauty.
The famous saying of the “M tax”. The cars are more expensive and so are their parts. There are exceptions to rule but most of the time that statement is on point.
The S88 / S38 / S54 are notoriously fiddly to maintain (albeit fantastic bits of engineering) and are a PITA due to all the electronics changes necessitated to add an older engine / DME to a newer car, the S50 / S52 is less fiddly, but not really a performance gain over the N52 unless you get the Euro-spec engine, and it still has the DME issue of the other inline S-motors, while the S65 is both fiddly (when compared to the E39 S62) and more extensive amount of work to swap due to all the changes necessitated by I6 –> V8 form factor.
Anything post E-series chassis is forced-induction, which IMO, is where the M-Division lost the plot.
Also, for the E8x, there was no NA M-car – the 1M used the N55 since it was a skunkworks car.
I mean this is cool and a bit more practical but have ya seen the guy on insta building the stacks with the yellow Mercedes v12? Oh wee that’s one sweet piece of kit.
So it’s been a bit since I’ve been in the N52 game, so this might be a bit outdated. But, this isn’t a totally new idea. There’s been an adapter plate for the S54 itbs for years. Finding a set of S54 itbs for a grand could be challenging, so there’s that. People have been running off stock ECU. This has mainly been in the race/drift cars, where a certain degree of failure can be accepted. Trying this for a street car, gets interesting. Mainly, because they are trying to make it doable for a stock exhaust. It seems like they are going to keep running into back pressure issues causing pre-mature cat failures. Only work around is going catless. Which 22rpd makes, so not a huge problem. Exhaust is really your main bottleneck on a N52. A 3disa and pushing the motor past 7.2k will get that cat up to solar level temps. With true straight pipes, MILV it’s not unheard of to bring the motor around 8k and up to 8.7k. Tends to land around 300whp depending on injector sizing and the motor you start with. Really past the point of a street car though, sucker is going to be loud. Price-wise too, your pushing up to some of the new plug and play turbo kits. Which you can push into the 500 area depending on your local fuel options and if one of those is starts with E.
I used to drive behind a stock 268bhp N52 in my E86. I loved that engine, it made up for the terrible numb steering.
Given that it was 268bhp from the factory with all the factory spec filter and intake system I think this system getting a peak 269bhp (on a tuner dyno) is underwhelming.
Also I don’t buy in to their assertion that having the safety throttle valve is a restriction, as it can be sized to be far larger than a traditional throttle because it only has to operate either fully open or fully shut/limp home.
They seem certain that the driver will “have the skills to diffuse” an unintended full power event, but that means punching it into neutral or getting the clutch down and letting it bang off the limiter until you’ve stopped the vehicle. I’d rather have a fail safe that doesn’t involve me doing the right thing immediately, especially as there is no convincing reason to delete the throttle valve.
Is the factory 268bhp measured at the crank, or at the wheels? It looks like they used a chassis dyno for the velocity stacks.
If the kit can increase power so that the new output at the wheels equals the original factory power at the crankshaft, that would be a bump of 25-30HP. Which would probably be a noticeable improvement.
Of course, if the factory HP is measured at the wheels, that 1 HP is well within measurement errors.
I work for OEMs designing engines. All our power figures are at the crank, what the transmission guys lose on the way to the wheels is their problem. Also we have to certify using crank numbers for homologation.
Tuners in the UK use rolling road dynos to measure power at the wheels, which is then “corrected” for transmission losses to give a crank power figure very few people actually believe.
I knew that most OEMs use crankshaft numbers, I just wasn’t sure that it was all of them. Or if possibly you had got that number from a chassis dyno.
Looking closer at that dyno sheet, they had a comparison to the un-modded car which tested at 254HP vs 269 for the velocity stacks, presumably on the exact same dyno so a solid comparison.
BMW made that 3.0 engine with outputs from 215 to 268bhp, all constrained by having a throttle and intake ducting. If the concept is effective it should be tested on the high output engine, otherwise it’s not really proving its better than a traditional intake.
In the dyno sheet shown above, the before dyno already had an n54 intake manifold, headers, 3″ exhaust, milvs, and tune. The only change on the second run was adding the velocity stacks and retuning it.
The dyno from 22RPD is measured in WHP. Your figure from the factory rating is in HP. Assuming a 15% drivetrain loss for an automatic RWD drivetrain, 269whp= 317HP.
I just got back from Goodwood MM. There were some (a lot) of these , none of them involved fuel injection, or hoods. Have look at Shadow Cam/Am cars, They knew what an intake trumpet is. Small hint,do not try this with an engine you wish to use in the future.
Nothing wrong with an S52. I daily one in an e36 M3. It sounds glorious already from the factory. With an M50 intake manifold with a light tune it will put down numbers similar to what this N52 is putting out.
Good news, the S52 is a better engine than any N52 could ever be. It’s significantly simpler, doesn’t rely on an expensive, failure-prone water pump and electronic thermostat, isn’t made of a fragile magnesium (S52 is iron like a proper engine), can handle being overheated, and with an M50 manifold it sounds a hell of a lot better than any N52, even with this ITB mod. The Vanos in the S52 is also extremely simple and not failure-prone like the N52 Vanos (there’s currently a big TSB for N52 Vanos bolts backing out/breaking off and throwing timing).
There are several companies that sell ITB kits for the S52 as well, so you can also have ITB action, but with real ITB’s and not this Valvetronic malarkey.
I’m about to drop in a replacement motor after I spun the oil pump nut off the original. Installed a high-volume water pump, lower thermostat & electric fan switch so I can delete the mechanical fan with an eye towards an S54 radiator & oil cooler. Basically setting it up for a supercharger after my finances recover from this expenditure. Won’t sound as cool as ITBs, but an extra 120ish hp/100 torques sounds like good fun 🙂
No need to crap on the N52, it’s a fantastic engine.
N52 is aluminum / magnesium composite with Alusil cylinder liners. Not pure magnesium. It is not considered fragile – in fact, it is considered very reliable.
Yes, because BMW has not historically had problems with mechanical water pumps and thermostats (oh, wait, recommended preventative maintenance schedule for the M50/52/54/S50/52 is replace the pump and t-stat every 60,000 miles). The electronic thermostat / water pump used in the N52 has a significantly longer maintenance schedule (plus when either is starting to go bad, it will throw fault codes – something mechanical versions cannot do).
You are 100% correct on the N52 VANOS bolt issue, but thankfully, this only affects some N52 engines, not all of them (at least based on the recall). Unfortunately, I’m waiting for BMW NA to get their thumb out of their ass and replace my VANOS bolts as I am part of that unlucky cadre.
Valve-cover gasket and oil filter housing gasket (OFHG) leaking are one of the more annoying issues with N52 engines, but then again, to quote Sreten, all BMWs leak oil. That being said, if you do have an N52 engine and you notice oil leaking from your OFHG, get on it quickly as in rare occasions, this causes the accessory belt to fail (and bits of belt can get sucked into the crankcase through the front main bearing).
I’m not 100% sold on the 100% Valvetronic throttle design. Luckily, someone does make an S54 to N52 ITB adapter plate if you wanted to go that route (you’d still have to adapt the electronic throttle actuator to the S54 ITB linkage, of course).
I mean, if your car already has an N52, fine. But I specifically choose older BMW’s so I can have an M50 or M52. The water pump/thermostat is also significantly cheaper in the M5x motors, and much easier to do. I’ve worked on hundreds of BMW motors, this is just the conclusion I’ve come to.
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22RPD is pretty legit, PO of my ’83 533i with a ’91 M30B35 swap had them dyno tune it and with nothing more than an exhaust and “cold air” intake they pulled 22 hp out of it and even more torque.
I’m torn on this-on one hand super cool and will sound rad but on the other hand that’s a big investment of time and money to make 15 extra hp at 7100 rpm with a tiny bit of a smoother fatter curve in the midrange will be barely (if at all) noticeable in normal driving since there’s only a 4 lb/ft increase. And it looks like those gains were on top of engine that already had headers and exhaust plus you’re getting a dyno tune to make any of it add anything which at least at RPD iiirc is right around $1K. Honestly the baseline pull at 255 hp at the wheels on an engine that was rated in everything but the Z4 3.0 SI at 235 flywheel is the real story here.
This reads a bit too much like you copy pasted an ad – how is recreating what was sold on the exact same chassis in other markets a decade ago “substantially innovative”, italic emphasis theirs? Did you really need to copy all that over?
Seems like Valvetronic could use a short feature article of its own, I’d never heard of varying intake valve lift instead of using a throttle butterfly. That sounds very cool and also very fussy.
Would be interesting to touch on why the US version added a MAF. I can guess (EPA compliant limp-mode) but it could prompt some fun insight into differences between US and EU approaches to safety and cleanliness.
Variable lift goes back to Honda’s Variable Valve Timing & Lift Electronic Control (VTEC) of the late ’80s, and Porsche’s VarioCam of the early ’90s.
I’m quite aware of VVT technologies which operate on a limited range of lift/phasing changes, often just in a couple of settings.
Continually varying valve lift from 0-100% to meter intake fuel/air is rather more dramatic, and is new to me. I’d only expect to see that on a camless engine.
I assume the mitigation strategy in the event of a failure is the tried and true disclaimer “For Offroad Use Only”
Why mod a normal BMW engine, when you just get a proper ///M which already has individual throttle bodies, rather trust BMW engineering vs a knockoff assembly and all the other complication. BMW ITB’s are a thing of beauty.
M expensive.
Some people want to upgrade their mid-level cars to get a bit more performance and sound but don’t need the full-fat M.
LOL, then they should just put a $10 ebay ///M badge on it.
The famous saying of the “M tax”. The cars are more expensive and so are their parts. There are exceptions to rule but most of the time that statement is on point.
Yeah just pay the tax and accept it, no reason to reinvent the wheel.
The S88 / S38 / S54 are notoriously fiddly to maintain (albeit fantastic bits of engineering) and are a PITA due to all the electronics changes necessitated to add an older engine / DME to a newer car, the S50 / S52 is less fiddly, but not really a performance gain over the N52 unless you get the Euro-spec engine, and it still has the DME issue of the other inline S-motors, while the S65 is both fiddly (when compared to the E39 S62) and more extensive amount of work to swap due to all the changes necessitated by I6 –> V8 form factor.
Anything post E-series chassis is forced-induction, which IMO, is where the M-Division lost the plot.
Also, for the E8x, there was no NA M-car – the 1M used the N55 since it was a skunkworks car.
The 1M actually used the N54. The 1M, 335iS, and the Z4 35i and 35iS all kept the N54 while the other models had already moved on to the N55.
Thanks for the accuracy check.
For clarity, when you say E8x, your not including the E85/86 Z4 models correct? Because there’s was the Z4M which used the S54.
Dammit, I always forget about the Z4. Was strictly speaking of the E81/82/87/88 models.
I mean this is cool and a bit more practical but have ya seen the guy on insta building the stacks with the yellow Mercedes v12? Oh wee that’s one sweet piece of kit.
damn the machining, the photography… this project is probably the one that’s really caught my eye. https://www.youtube.com/watch?v=blHuloYXc4o
So it’s been a bit since I’ve been in the N52 game, so this might be a bit outdated. But, this isn’t a totally new idea. There’s been an adapter plate for the S54 itbs for years. Finding a set of S54 itbs for a grand could be challenging, so there’s that. People have been running off stock ECU. This has mainly been in the race/drift cars, where a certain degree of failure can be accepted. Trying this for a street car, gets interesting. Mainly, because they are trying to make it doable for a stock exhaust. It seems like they are going to keep running into back pressure issues causing pre-mature cat failures. Only work around is going catless. Which 22rpd makes, so not a huge problem. Exhaust is really your main bottleneck on a N52. A 3disa and pushing the motor past 7.2k will get that cat up to solar level temps. With true straight pipes, MILV it’s not unheard of to bring the motor around 8k and up to 8.7k. Tends to land around 300whp depending on injector sizing and the motor you start with. Really past the point of a street car though, sucker is going to be loud. Price-wise too, your pushing up to some of the new plug and play turbo kits. Which you can push into the 500 area depending on your local fuel options and if one of those is starts with E.
I used to drive behind a stock 268bhp N52 in my E86. I loved that engine, it made up for the terrible numb steering.
Given that it was 268bhp from the factory with all the factory spec filter and intake system I think this system getting a peak 269bhp (on a tuner dyno) is underwhelming.
Also I don’t buy in to their assertion that having the safety throttle valve is a restriction, as it can be sized to be far larger than a traditional throttle because it only has to operate either fully open or fully shut/limp home.
They seem certain that the driver will “have the skills to diffuse” an unintended full power event, but that means punching it into neutral or getting the clutch down and letting it bang off the limiter until you’ve stopped the vehicle. I’d rather have a fail safe that doesn’t involve me doing the right thing immediately, especially as there is no convincing reason to delete the throttle valve.
Is the factory 268bhp measured at the crank, or at the wheels? It looks like they used a chassis dyno for the velocity stacks.
If the kit can increase power so that the new output at the wheels equals the original factory power at the crankshaft, that would be a bump of 25-30HP. Which would probably be a noticeable improvement.
Of course, if the factory HP is measured at the wheels, that 1 HP is well within measurement errors.
I have never heard of factory ratings being done at the wheels (with the exception of the ridiculous GMC Hummer “11,000 lb-ft of torque” lie)
268 hp is definitely at the crank.
Stock 330i N52 usually lands around 215 whp.
I work for OEMs designing engines. All our power figures are at the crank, what the transmission guys lose on the way to the wheels is their problem. Also we have to certify using crank numbers for homologation.
Tuners in the UK use rolling road dynos to measure power at the wheels, which is then “corrected” for transmission losses to give a crank power figure very few people actually believe.
I knew that most OEMs use crankshaft numbers, I just wasn’t sure that it was all of them. Or if possibly you had got that number from a chassis dyno.
Looking closer at that dyno sheet, they had a comparison to the un-modded car which tested at 254HP vs 269 for the velocity stacks, presumably on the exact same dyno so a solid comparison.
BMW made that 3.0 engine with outputs from 215 to 268bhp, all constrained by having a throttle and intake ducting. If the concept is effective it should be tested on the high output engine, otherwise it’s not really proving its better than a traditional intake.
In the dyno sheet shown above, the before dyno already had an n54 intake manifold, headers, 3″ exhaust, milvs, and tune. The only change on the second run was adding the velocity stacks and retuning it.
The dyno from 22RPD is measured in WHP. Your figure from the factory rating is in HP. Assuming a 15% drivetrain loss for an automatic RWD drivetrain, 269whp= 317HP.
I have a stock N52 in 255hp trim, it’s pretty fast. The lag is something that bothers me. I’d like to drive this to see the improvement.
I just got back from Goodwood MM. There were some (a lot) of these , none of them involved fuel injection, or hoods. Have look at Shadow Cam/Am cars, They knew what an intake trumpet is. Small hint,do not try this with an engine you wish to use in the future.
Ah, the siren call of intake (s)trumpets at full chat
Sadly, I’m playing with an S52 (hangs head, hands in pockets, nudges dirt with worn sneaker)
Nothing wrong with an S52. I daily one in an e36 M3. It sounds glorious already from the factory. With an M50 intake manifold with a light tune it will put down numbers similar to what this N52 is putting out.
Good news, the S52 is a better engine than any N52 could ever be. It’s significantly simpler, doesn’t rely on an expensive, failure-prone water pump and electronic thermostat, isn’t made of a fragile magnesium (S52 is iron like a proper engine), can handle being overheated, and with an M50 manifold it sounds a hell of a lot better than any N52, even with this ITB mod. The Vanos in the S52 is also extremely simple and not failure-prone like the N52 Vanos (there’s currently a big TSB for N52 Vanos bolts backing out/breaking off and throwing timing).
There are several companies that sell ITB kits for the S52 as well, so you can also have ITB action, but with real ITB’s and not this Valvetronic malarkey.
I’m about to drop in a replacement motor after I spun the oil pump nut off the original. Installed a high-volume water pump, lower thermostat & electric fan switch so I can delete the mechanical fan with an eye towards an S54 radiator & oil cooler. Basically setting it up for a supercharger after my finances recover from this expenditure. Won’t sound as cool as ITBs, but an extra 120ish hp/100 torques sounds like good fun 🙂
No need to crap on the N52, it’s a fantastic engine.
I mean, if your car already has an N52, fine. But I specifically choose older BMW’s so I can have an M50 or M52. The water pump/thermostat is also significantly cheaper in the M5x motors, and much easier to do. I’ve worked on hundreds of BMW motors, this is just the conclusion I’ve come to.