500HP K24 Turbo Intake Manifold Testing

Purpose:

We recently conducted an intake manifold test on a stock naturally aspirated Honda K24 engine and received a good amount of positive feedback from you all. Along with that, we had several people request that we replicate that same test but in a turbocharged application so we did just that. We reached for some of the popular options when building the turbo kit around the K24, and selected what you would most commonly use for a 5-600hp setup that can still have room to grow in the future. Before we dive into the test process, i'll make a list of the turbo kit parts we used so you can take those into consideration for your build. Since the Intercooler we used was a large core suspended above the engine dyno and not a chassis specific one, I included a common intercooler used in most swapped chassis with FWD K Series engines.

Intentional Starting Variables:

• Test 1: Skunk 2 Pro Series Intake Manifold w/ 74mm TB
• Test 2: Skunk 2 Ultra Street Intake Manifold w/ 74mm TB
• Test 3: Skunk 2 Ultra Race Intake Manifold + 2 Liter Plenum Spacer w/ 90mm TB

Contants:

• Engine: 2.4L K24A (RBB-2 JDM Engine) Stock Internals
  
• Turbo: 6466 Gen 2 1.05 ar
  
• Fuel: Gasoline 93 octane
  
• Lambda Target: .75
  
• Dyno:  Superflow SF-Powermark
  
• Engine Acceleration Rate:  600rpm/sec 
  
• Start RPM:  4,000rpm

Unintentional Starting Variables:

• Engine Coolant Temperature: [T1: 180°F, T2: 184°F, T3: 180°F]
  
• Engine Oil Temperature: [T1: 201°F, T2: 195°F, T3: 197°F]
  
• Ambient Air Temperature: [T1: 88.2°F, T2: 87.6°F, T3: 89.5°F]
  
• Density Altitude: [T1: 2262ft, T2: 2198ft, T3: 2310ft]

Test 1: Skunk 2 Pro Series Intake Manifold w/ 74mm TB

Results:

• Peak Horsepower: 530.7hp @ 7800rpm
• Peak Torque: 406.8tq @ 5600rpm

This manifold is a popular go to for its OEM style footprint, as well as being the most affordable of today's 3 manifolds. Paired along with this Skunk 2 Pro Series intake manifold was their 74mm throttle body as well. We ran this combo at the 17.5 psi target and established our baseline. Next to do was change the manifold over to the ultra street while retaining the same 74mm throttle body.

Test 2: Skunk 2 Ultra Street Intake Manifold w/ 74mm TB

Results:

• Peak Horsepower: 537.3hp @ 7480rpm (↑ 1.24% from test one)
• Peak Torque: 403.5tq @ 5700rpm (↓ 0.81% from test one)
  
  

Once switched over to the Ultra Street intake manifold we went back to preform the same run also at the same boost target of 17.5psi. The results were very similar between this manifold and the Pro Series, and the powerband was close as well. One of the good things about this Ultra Street intake manifold is it's removable plenum making it possible to add plenum spacers, or port the runners if you choose to do so. I'll add a couple dyno graphs down below, first this solo run with the Ultra Street and then a graph showing both runs laid on one another. For this manifold and the rest of them moving forward, we need to run an additional coolant port off to the front right of the head. This is so that we can run this "K20" style intake manifold. 

For a few spots in the run, we see the Pro Series make more torque and until roughly 5700rom even more HP, but thats not the case throughout the whole run. We see from that point forward, the Ultra Street begins to be the winner, even showing a larger increase in power above 7000rpm.

Test 3: Skunk 2 Ultra Race Intake Manifold  + 2 Liter Plenum Spacer w/ 90mm TB

Results:

• Peak Horsepower: 538.1hp @ 7900rpm (↑ 1.39% from test one)
• Peak Torque: 380.7tq @ 6600rpm (↓ 6.41% from test one)

This third and last test was with the Ultra Race manifold, their 2 liter spacer, and a 90mm throttle body. Given the different bolt pattern on this larger plenum, you cannot run an OEM style throttle body. This might be something that will play a roll in choosing your manifold as you might not want to step to a larger thorttle body for your build. The results we got on this run were interesting. We immediately dropped torque, low end HP, while making very similar power to the ultra street up top. There was a small section where the Ultra Race made more HP than the Ultra Street and Pro Series manifolds, but that was only for a very small window. Like the previous two runs, we still stayed on that 17.5psi target throughout the run. 

Conclusion:

What did we learn here? At face value you could see these tests and say that since the Ultra Race made the highest peak HP, even if only for a short window, that may be "the best" option, but the take away is not that simple. Being able to load the engine with our desired boost even at low RPM and then run out our tests allow us to clearly see how the engine is reacting to these changes. We noticed that at this power level, both the Pro Series and the Ultra Street perform very similiarly, and if you're happy spending a little more then the Ultra Street is a great choice. The Pro Series manifold isn't a bad option, but there is HP left on the table if you choose to go with that option. The Ultra Race really wasn't working well down low in this application and will likely have perfomed much better on a higher HP aimed application given it's short runner, big plenum design. Once again, this is a STOCK K24a engine turbocharged and at different HP levels, we would likely have different outcomes. 

I think the big take away from this should be that bigger isn't always better at this level. Down the line we will replicate this test at a higher HP range and come back to compare these graphs as we may have some different findings. 

What did you find most interesting about this test, and what would you like to see us do next? Reach out to us and we’ll make it happen.

Thanks for reading along, and we hope this information was helpful to you!