BNR Engine Spacer Tech Talk

Engine Spacers. What do they do? how? do I need one?

Engine spacers like throttle body, intake manifold, carburetor, and more have been around ever since people started modifying cars.  Carburetor spacers typically worked by getting the air/fuel mix further away from the hot engine and letting it atomize further before going into the cylinder head, resulting in "potentially" more power. This was subjective. Some engines gained power, some didn't.  We've come a long way since then and spacers have more use than just trying to add some power.  BNR throttle body spacers for example may add a couple HP, may not, depending on your build, but they're not advertised for that purpose. We sell them as a way to add a boost gauge, meth injection, nitrous, or the most popular option; a PCV fix kit.  

But what about intake manifold spacers? Intake manifold spacers are proven to add power by adding volume to the air entering your cylinder head. This has been shown to aide in cylinder filling at lower RPM, smooth out throttle response, build boost sooner, and lengthen the effective wave pulse of the intake charge. In the dyno shown above, you can see the charts of an intake manifold spacer. Over 30 ft lbs of torque gained and a significant change in the horsepower curve, while sacrificing very little power on the top end. (Img. credit to Boomba Racing, inc.)

One of the most important aspects of spacer design is the diameter of the holes the air flows through. This is why BNR uses files obtained from the engine manufacturer themselves or by using our own 3d scanning techniques and using drafting software to design spacers that are matched perfectly to the engine they will be going on. 

It's important to consider both sides of the spacer. Some spacers need to taper down or up to smooth the airflow going from the throttle body into the intake manifold, for example the GM LTG 2.0 Turbo engine. See below how the BNR spacer tapers to make a better transition than stock. It's not good to have oversized or unmatched areas as they can disrupt airflow negatively and actually rob you of power.  

On the GM LE2 1.4T found in the Gen 2 Cruze, which uses these same parts as the LFV 1.5T for example, BNR specifically matched the spacers to their counter parts. See the measurements below.

The back of the throttle body on the LE2 is 43.77mm in diameter.

The throttle body inlet on the intake manifold is 44.82mm in diameter, almost a full millimeter larger than the throttle body opening. Not enough to require the spacer to taper up, but enough that you wouldn't want to go larger, as it's already larger than the throttle body itself. 

Next let's take a look at the intake runners on the cylinder head.

The intake runner on the cylinder head is 44.03mm wide and 26.14mm tall.

Next, let's take a look at the stock intake manifold port size.

You can see that this particular intake manifold measures at 43.10mm wide, and 26.34mm tall. 

Again, we do not need to taper anything, or go any wider as the intake manifold is already matched perfectly to the intake runners on the head. Going larger would yield zero gain in power, and might even hurt power due to disrupting airflow with a drastic size change. In some cases going larger is as bad or worse than going smaller. 

So as you can see above, spacers can absolutely add power if done right, and are also a great way to add extra ports or taps for different use cases. 

For any questions relating to BNR spacers, feel free to message us on Facebook, Instagram, the live chat function on this site, by email at [email protected], or you can call us at 561-600-5543.

Add Comment