Power Increase with just a Hat Change?

Ok, here I go with my two cents. I was on the road and didn’t want to type this all in on my BlackBerry.
Thanks Fastavenger, your post saying you could turn the hat around backwards and not see a difference really had me rolling on the floor laughing. If that was so then a jet fighter would get off the ground or a Dyson vacuum cleaner wouldn’t work. I would like to see you go your 242 MPH with your Big and Ugly turned backwards (lol). Here is a little experiment. Get in the bed of a pickup truck and have somebody drive you down the road at 30 mph. Now facing forward raise your head above the cab roof into the airflow and open your mouth wide like it was the inlet of an injector hat. Now what do you feel in your mouth and lungs….I bet you feel a lot of air pressure. That is RAM AIR. Now go up to 50 or 60 MPH and try it again……more pressure in your lungs because the velocity of the pickup increased and so did the RAM AIR. Now turn around backwards so the wind is hitting the back of your head and open your mouth. Now you have no RAM AIR and the rushing air is actually sucking the air out of your lungs. That RAM AIR is there all the time if you have forward velocity. The faster you go the more the RAM AIR. With the injector hat sitting up in the airflow facing forwards this RAM AIR increases the CFM and boost and is horsepower for nothing and we use it and that is why a hat makes a difference.
One of the problems is duplicating that RAM AIR in a dyno room. You just can’t so the only thing you are really testing if swapping hats on the motor during a dyno run is the flow of the air internal to the hat. I think what is confusing people is that if your put a large hat on a small motor such as a 400 cubic inch motor that has a 6-71 or an 8-71 at a very low OD and the max RPM is not very high then the CFM being sucked into the top of that blower is probably way less that the hat is capable of passing so no restrictions at wide open throttle so can swap hats all day long on a motor like that and never see a difference and you can save your money. Now let’s go to the extreme and put a max’d out DMPE or a CFH 14-71 HH blower at a high percentage OD and take the motor up to 10,000 RPM. Now the CFM going into the top of that blower opening is restricted by the CFM flow of the hat. Getting the highest flowing hat in this case can help and does make a difference.
We know that the shape of the opening in front of the butterflies makes a difference as we also know the angle of the air coming into the blower from the front of the hat makes a difference. That angle needs to be as straight as possible. A single 90* turn in a hat can reduce the air flow by up to 50% but again if your motor is getting all the air it can handle then it doesn’t make much difference if you lose 50% of the airflow because of the design of the hat. The other thing that is important is matching the outlet of the hat to the inlet of the blower. If you hat outlet is longer than the blower inlet the incoming air will hit that ledge created by the blower and will go crazy and reduce the air flow. This is why buying a spacer to match these two openings and moving the hat forward to straighten out that airflow can make a BIG difference. If the holes match then not so big difference.
I know the engineer that designs John Force’s injector hats. This guy is an aerodynamisist with seven degrees and we both worked at the same aerospace company. He spent a couple of hours with me talking about the two hole hat he designed for JFR and all the little secrets to make it flow more. There is a lot more to a well designed hat than what we all think. I do agree that if you are not pushing the envelope with your motor then maybe some of these expensive hats are not for you but some of these old out dated hats are not either. For those guys pushing the limit then the hat does make a difference but you can lose that difference by not having it match the blower so it will all be wasted and you will never see a gain or by not changing your GPM to match the increase flow of air.

 

Well the air doesn't drop straight down into the blower. It is actually sucked in close to the steep angle it blows out. My guess is that it is somewhere between a 30 and a 45 degree angle toward the back of the blower top opening. Even in tractor pulling you have to have a smooth flowing hat that can give you the max CFM you need.