I highly suggest watching the 5-10 seconds videos I will link because it demonstrates a bit better and helps to understand the simulations a bit better.
Even tho I’m not super active on my build thread or on social media in general, my car has been running since September. I have touched, modified, optimized everything on the car. I do believe that some stuff can be done by hand/eye but some other do require proper work and simulations. I’ll update more thoroughly my build thread when I have more time.
READ THE CONCLUSION OF MY FINDINGS AND WHAT IS MY HYPOTHESIS
The last piece of my puzzle is my intake manifold! After seeing how my exhaust manifold changed my car, intake manifold was inevitable.
Took some time to learn proper CAD work/design, bought myself all the equipment needed and here I am
KEEP IN MIND THAT THOSE ARE SIMULATIONS THAT ARE RAN INDEPENDETELY AND THAT REAL LIFE EFFECTS CAN’T BE REPRODUCED UNLESS I HAVE A TEAM OF ENGINEERS ON IT FOR A COUPLE WEEKS/MONTS
However, to see that the manifold on its own is that flawed just shows how much power is robbed from our platform, can you imagine how much more power we are actually losing after considering the turbo piping, the intercooler design, the silicone couplers, the heat, etc. I took the time to scan my OEM manifold, measure all the sizes, lengths, thicknesses, etc using a digital caliper. Here is the final 1:1 replica of the stock OEM manifold. FLANGE AND THROTTLE BODY ARE NOT USUALLY PLUGGED, IT IS DONE SO I CAN RUN THE SIMULATIONS AND HAVE EVERYTHING WATERTIGHT.
ALL SIMULATIONS HAVE BEEN MADE USING AVERAGES OF REAL LIFE DATALOGGING FROM A 2006 M66 V70R
Mod list :
Car is in pristine condition and amazing maintenance done on it
Snabb full intercooler kit and piping
Snabb catless downpipe
Straight pipe exhaust
Snabb intake
Snabb airbox
Audi RS4/S4 MAF
One step colder spark plugs
Do88 Radiator
Hybrid K24 Turbo
950cc injectors
340LPH fuel pump
What I include are the visualization of the simulations but the real calculations take a long time and would take ages to compile. It is not rocket science but I do understand if people are not familiar with it so feel free to ask questions / details.
So here are my findings :
It’s important to understand that it is not in every case, every condition and every runner that we see those differences. What I’ve done to simulate as close to real life conditions, I’ve used real dataloggings during WOT (wide open throttle) pulls. Outside temperatures were around 70-76*F (21-24*C) with little to no humidity.
– DENSITY wise, we can see an average drop/difference of 12% per runner (from plenum to runner x5). At max we can see a 21% difference in some cases and goes as low as 3% difference (only the 4th cylinder).
–Cyl 1 : Density becomes low just after the plenum for a short distance then becomes low again just before the head ports. Important to know that most of the density is seen on the walls of the runners and the inside/middle of it is very low/empty. In that runner we see an average of 8-9% difference from the whole length and width.
–Cyl 2 : Very close to what is happening in the Cyl 1 BUT we can see an even lower density at some times. Averaging a 10-11% difference from the whole length and width.
–Cyl 3 : This one is probably the most problematic and disturbing to see HOW BAD ITS CONDITIONS ARE……. (keep that in mind for the pressure and velocity simulations as well. We see an average drop/difference of 27%!! I don’t even know what to say to that lol. Just imagine how much the car cuts on power or how more prone we are to knocking in those conditions.
–Cyl 4 : This runner is the least problematic and honestly very good in every single condition and simulation. It succeeds very well when it comes to density, velocity and pressure simulations. Nearly no drop/difference of density (average of 3% and a minimum of 1.1%)
–Cyl 5 : Now this runner is the second worst one (after the Cyl 3). The walls pretty much hold all the density and the inside is nearly empty. Average density difference of 17% difference.
- PRESSURE wise, we can see an average drop/difference of 23% (from plenum to runner x5). At max we can see a 36% difference in some cases and goes as low as 11% difference. This leaves a lot of power on the table and is again something else in the design of our cars that robs potential. Weirdly enough the cylinder 3 is the one that has the least issues/drop/difference. And again, weirdly enough cylinder 4 is the one that suffers the most. However, all around it is very lacking and not ideal. Keep in mind that when designing the intake manifold for a performance turbocharged car, the choice between long and short runners and the design of the plenum are crucial for optimizing engine performance. Our OEM design has pretty long runners and is not ideal for high performance goals but is great for everyday driving. The plenum seems to be well design shape wise but is lacking dimension/scale wise as in it should have been bigger (BUT NOT TOO BIG).
- SHORT RUNNERS : beneficial for high RPM performance because they allow the air to travel quickly into the cylinders. This design helps to maximize horsepower at higher engine speeds, making it suitable for racing or high-speed driving. In a turbocharged engine, short runners can help improve the response of the turbocharger by reducing the volume of air that needs to be pressurized, leading to quicker boost build-up.
- LONG RUNNERS : better for low to mid-range RPMs. They utilize the principle of resonance, where the air pulses can enhance cylinder filling at these lower engine speeds. This results in better torque and drivability at lower RPMs, which is advantageous for street driving and improving overall engine efficiency.
- PLENUM DESIGN : is crucial for balancing the airflow and optimizing performance. The size of the plenum should be balanced. A larger plenum can store more air, which can be beneficial for maintaining consistent air pressure and improving throttle response, especially in turbocharged engines. However, it should not be excessively large, as this can lead to slower airflow dynamics. The shape of the plenum should promote even air distribution to all cylinders. Smooth transitions and tapered shapes can help reduce turbulence and ensure that each cylinder receives an equal amount of air. The plenum should be designed to equalize the pressure across all runners. This can help in achieving a balanced air-fuel mixture and consistent performance across all cylinders. The position of the throttle body on the plenum can influence airflow dynamics. Center placement can help distribute air more evenly, whereas side placement may require careful design to avoid flow bias towards certain cylinders.
- VELOCITY wise…. where to start. We can see an average drop/difference of 56% (from plenum to runner x5). At max we can see a 87% difference in some cases and goes as low as 18% difference. THIS IS UNACCEPTABLE AND HAS TO BE ONE OF THE MAIN REASONS AS TO WHY OUR CARS HAVE SUCH SLOPPY THROTTLE RESPONSE. This is personally what I was looking the most forward to discover. After seeing some very high end performance shop prove how fundamental velocity efficiency in manifolds is, it kind of sealed the deal in my head and was my main target when designing my own intake manifold (more on that later).
- Cyl 1 : Here we can see that the velocity is NOT straight which does not directly mean that it is a flawed discovery. However, considering the pressure and density findings, it’s not a great one… Even tho that velocity is not slowed that much in the runner itself, just before it (in the plenum) we can see a huge amount of turbulence and shows that the air does not directly go into the runner which leads to a slower throttle response and worst top end performance.
- Cyl 2 : IDEM as Cyl 1 however velocity is more lacking than Cyl 1.
- Cyl 3 : Now here….. it reaches a maximum of 87% velocity drop. 87 F…ing pourcent. This is happening because of 2 reasons. First, the flow design of the plenum does not allow a good a direct flow. Second, Cyl 4 is taking nearly all all of it which creates a ”suction” effect.
- Cyl 4 : No comment other than its velocity is very very good.
- Cyl 5 : PLEASE WATCH THE VIDEO WHICH HELPS TREMENDOUSLY TO UNDERSTAND WHAT IS HAPPENING. If you look at the top (plenum) you can see a ”tornado” forming which then ”blocks” the air coming from the throttle body and then to the runner. Velocity is greatly reduced in that runner as well (second worst after Cyl 3).
CONCLUSION AND RECOMMANDATIONS (that I took into consideration when designing my own manifold):
I do think those are the reasons why the MAJORITY of cracked blocks as seen on the cylinder 2-3 and 5 (which lacks uniformity in all simulations). Or at least a HUGE contributing factor to that…. For any mechanic that worked a lot of this platform over the years, this also explains the reasons as to why the Cyl 2, 3 and 5 are the ones that suffer most from burnt exhaust valves and lower compression over the years.
- Plenum design : Increase the size of the plenum to improve airflow consistency and throttle response, but avoid making it excessively large. Redesign the plenum shape to promote even air distribution and reduce turbulence. Consider central placement of the throttle body to ensure more even airflow distribution. (if possible and if not, it is possible to add a redirecting fin just like rally start central manifolds)
- Runner design : Opt for shorter runners for high RPM performance to improve horsepower and turbo response. Alternatively, if maintaining long runners for low to mid-range RPM benefits, optimize the internal design to reduce density and velocity losses. Implement smooth transitions and tapered shapes in the runners to minimize turbulence and ensure consistent airflow. I personally opted for internal velocity stacks which was the best results when doing simulations.
- Flow dynamics optimization : Conduct detailed CFD (Computational Fluid Dynamics) simulations to identify and rectify specific areas of turbulence and uneven airflow. Use flow straighteners or velocity stacks to enhance airflow uniformity entering each runner.
- Pressure equalization : Design modifications to balance pressure across all cylinders, potentially through internal plenum baffles or staged runner entries. Ensure that each runner receives a consistent air-fuel mixture by equalizing pressure, which can improve overall engine performance and reliability.
- Velocity enhancement : Improve the internal surface finish of runners to reduce friction and enhance velocity. Modify the plenum entry to reduce turbulence and improve the direct flow of air into the runners. Address specific issues in Cylinder 3 and Cylinder 5 by redesigning the runner entries and flow paths to minimize velocity drops and eliminate blockages.
By implementing these design improvements, the intake manifold can achieve better density, pressure, and velocity characteristics, leading to enhanced engine performance, better throttle response, and increased overall efficiency.
I have decided to make mine in 2 pieces and everything will be done using T-6061 aluminum and CNC machined from one uniform block of material.
Thanks for coming to my TED talk… feel free to ask questions
HERE ARE ALL 3 VIDEOS :