Max Spacer

For that amount of money I believe I would give Darren at DMPE the exact size and shape of the bottom of the hat and the opening in the top o the blower and have him custom make one to fit my application. It is so important to not have any ridges or ledges inside that will disturb the incoming airflow. It needs to be a perfect match.

 

Having an injector hat larger than the inlet of the blower is probably the worst kind of mismatch. The largest percent of air that matters going down the throat of an injector hat follows the back wall of the hat aiming towards the back of the sides of the two rotors so a mismatch disrupts this airflow and creates max turbulence. Airflow is reduced which results in loss of boost and CFM of air into the motor. What happens when you stick your hand out of the car window at 60mph? Imagine the velocity of that air rushing down the inside of the hat and hitting the ridge made by the mismatch. Now we also know that boost is gained some by matching the front of the injector opening and front of the blower opening, not as much as the back but it is still boost. That match is also important. The other thing a spacer does is move the hat forward so the angle the air has to turn is reduced. So if you open the butterflies and take a flashlight and look to the back of the rotors that should be the straightess smoothest shot. Any turn in airflow reduces the amount of airflow. For example turning the airflow by an abrupt 90* will reduce the airflow by 50%. If the hat is slightly smaller than the opening then you can grind some and make it a smooth transition but having the hat larger than the blower opening is BAD. So be very careful in paying big $$$$ for a generic spacer that does not allow for smooth airflow by a smooth transition. Maybe a little grinding can match it better. If it is a large mismatch then don't buy it or return it. Darren Meyer at DMPE and Mike Janis at Jan-Cen can custom make you a spacer that matches the hat opening and the blower opening. You can tape a piece of paper over both openings and rub a pencil over the paper and outline the openings and send it to him and he will match the two. Anybody that can make one like this is giving you more flow for the $$$$. Paying a little more can in this case give you more airflow and more value for the $$$$$.

 

If the injector hat is slightly smaller than the opening the yes you can grind the hat if it is thick enough to match the opening. If the injector is too big then how do you match the openings? A lot of hats have a 10.5"-11" bottom opening sitting on a 9.5" blower opening. And yes raising the hat up and moving it forward does help straighten out the airflow and makes more power. There is no point is spending $3000 for a hat on top of a $7500+ supercharger if they are not matched.