ITB Plenum Dyno Testing!
(27 April 2022)
In order to design the perfect ITB airbox we've had to do some research. This article tells you all about it!
Hummelink-Modifications is currently working on a plenum for individual throttlebodies. This airbox will work as a perfect solution for retracting cold air from outside the enginebay. 
This photo shows the first 4A-GE design, which will work on the Hummelink-modifications 4A-GE adapter and 4A-GE Toyotas.
Optional ventury spacers will be designed aswell, to get the perfect runner lenght for your setup.
This design allows for different baseplates, which makes it very interesting to offer baseplates for different makes and models.
In order to test and fit this plenum in real life, a prototype had to be made;
The most important information needed for this plenum, aswell as for the development of our current ITB kits, was the effect of runner lenght and shape. We've tested a variety of different velocity stacks to see what runner lenght will work best for the carbon intake plenum.
The runner lenght has a big influence on the torque/hp curve and there's definitely a bit more potential to gain with changing to a other lenght.
Theoretically, a longer stack will result in a lower powerband, which means more torque in the lower rpm's and a bit of power falling of up top. And that's exactly what happened.
130mm seems to be the best compromise for both torque and hp. It doesn't fall off up top but has a lot more bottom end torque. 130 stacks with a Hummelink-Modification ITB kit add up to a total intake lenght of 330mm (valve to end of ventury).
Glad to see this engine is capable of 172HP, aswell as 180nm with different velocity stacks. Not bad for a naturally aspirated 1.6 Miata!
Take a look at the next dyno graphs:
- the first one compares a 130mm cone to a 160mm cone. The torque is way higher on the long cone. I managed to make 7hp more with the 130mm cone than with my current 70mm setup.
- The second graph compares 4 different lengths. It's just with aluminum pipes without ventury shape. That's why the power is a bit lower. It's just for comparison.
- Graph 3 compares a 130mm cone to a 130mm pipe. It's very clear that a well designed ventury makes a difference aswell
- Graph 4 shows a few high rpm pulls. The revlimit was set at 8500rpm. This engine is capable to remain the same horsepowers all the way up to 8.5k!
- Graph 5 shows the plenum baseplate compared to the baseplate with airbox. Both without runners, which results in less torque.
The airbox needs a bit more volume, since it loses a slight bit of power, even with a huge 100mm inlet.
Eventhough it makes less power with the airbox, this would probably be a more consistent choice with the hood closed after a few laps on track. Since a lot colder air can be sucked in from the bumper instead of the hot engine bay air.
Loads of information to improve the airbox/intake. Let's get to work!
Expect it on the webshop in 2023!