View Full Version : Eaton supercharger mod from the Eaton board discussions

07-28-10, 01:16 PM
When it comes to modification of these superchargers, the common areas of modification are:

Porting of the inlet portion of the housing
Porting of the internal housing
Porting of the outlet plate of the housing
Porting or Plugging of the "holes" on the outlet plate
Running a smaller pulley
Heat reduction, supporting modifications

The basic idea here is to increase CFM without raising IAT's. These basic principles can be carried over to any other application using an M-Series blower. It should be noted, that the M-series superchargers are effectively air pumps. They do not internally compress the air themselves, but push it into the lower intake manifold. It is in the lower intake manifold that positive pressure emerges. Most folks think Eaton's roots-type units are actually squeezing the air like a screw unit. This is not the truth. No air passes between the rotors, the air is guided by the rotors along the sides of the housing; hence, no internal compression of air.

Porting the M-Series Supercharger:

It is not a good idea to remove too much material from any portion of the blower. Extreme porting of the blower will disrupt the air and will reduce efficiency greatly. A light porting of the inlet housing will help increase intake CFM of the pump. Typically, if a TB (throttle-body) upgrade is available, it helps to match the TB port size to the inlet port for a smooth intake of air with minimal disruption. Smoothing this opening up and enlarging it slightly will help introduce more air into the rotor housing which can then be "pushed" into the lower intake manifold. The inside of the housing can also be lightly ported to increase internal surface area. It is important to note, that internal porting of the rotor housing should be very minimal. Basically, remove any and all casting flashes and ensure complete symmetry while removing as little material as possible. Removing too much material will interfere with air flow and the functionality of the rotors. The output plate at the base of the M62 housing is what can be modified the most. This plate has one large triangular and two small oval passages in it. Right now, we'll focus on the large triangle. This is the passage that air is pushed through by the rotors to create a positive pressure in the lower intake manifold. This passage can be opened up slightly and smoothed out for best flow. Opening it up too much will also disrupt airflow. This is the most porting that should be performed on an Eaton M-Series blower to maintain efficiency.

Air Leakage Ports:

The two oval slots on the output plate are air leakage ports. Their only purpose is to decrease operational noise from the blower. Arnie, from Eaton Corp., explains their function like this, "When you stomp on the gas, the boost shoots up and the air flow goes supersonic. The air then slams back into the output plate and through the leakage slots, which reduces the hammering of the air into the housing causing less noise. The OEM can not have such loud NVH, that’s why we put them in the housing. The 2 small ports are not there to feed air, only to reduce noise." Basically, for the best flow and most efficiency, these ports can be blocked off, making the outlet port (triangle slot) the only port on the outlet plate of the housing. Closing these ports will not increase IAT's; however, it will make the supercharger much louder when in boost. As an example, aftermarket supercharger companies, such as Harrop, Roush and Magnuson do not use these slots in their blowers. It should be re-stated, that you should consult professionals regarding closing these ports; and do not, for any reason, plug them with JB Weld. Improper closure could eventually lead to pieces coming apart and loose debris destroying the rotors and housing. Opening up these ports will only have a negative effect on efficiency. Do not port them.

Originally Posted by TVS_SS 


while it is beneficial to have these holes closed, by welding you will distort the rotor bores and change the heat treat on the aluminum.

do not WELD on a finish machined housing anywhere near the rotor bores!!!!!

you will end up with rotor contact issues or large gaps.. these are precision machined bores.. it would be like welding on your cylinder bores.. NOT A GOOD IDEA!

Please take TVS_SS' comment into consideration while modifying your Eaton Supercharger. If you choose to close the leakage ports, do so knowing the risks and consult professionals like Magnuson, Harrop or Eaton before making final decisions...( I think for our board we can add D3 on to this list)

From D3:We have spoken with Arnie on several occasions a few years ago when we were doing all of the development work for the LC3 engine. There is certainly more to that conversation than what is shown. The expected HP gains to be had by sealing up those pre-charge ports are about 10HP and a bunch of noise. This would have to be done off the car with the rotor/bearing pack removed from the assembly.

We experimented with this, but did not feel it would be prudent to introduce to the market.

Cadillac at the time wanted to have the NVH levels as low as possible, thinking that the average STS-V owner would not want to hear the supercharger whine, thus the pre-charge slits and the intake mufflers.

The problem still persists, the supercharger hits its limit fairly quickly when adding additional boost. Dont get me wrong, there is power to be gained. But if you are looking for major power, the blower has to go. No porting, fabrication, extrude hone, etc.. will be able to bring that blower back into an operational range when overboosted to make big power. This is why we are working on a new customer blower for this application.

Thank you,

Dr. Design
D3 Cadillac

Arnie, as mentioned earlier, is Eaton's Performance Products Training Instructor and has made himself and his team available for questions regarding their product and modifying it for best performance. Please visit http://www.eatonperformance.com and you will see an area "Ask the Experts." Any questions will be answered as best as possible as time permits (they receive 100's of questions a day).

Running a smaller pulley:

Reducing the size of the pulley increases both response time and maximum RPM of the supercharger. The stock pulley sets the blower at maximum efficiency and reducing pulley sizes does reduce efficiency. Porting the supercharger and using supporting heat-reduction modifications can help negate these negative effects of increasing boost by using the smaller pulley. While they do help reduce the negative effects of increased IAT's, these supporting modifications can only help so much. The increased IAT's produced by using any smaller than a 2.8" pulley will most likely not be able to be reversed by these supporting modifications. It is not recommended to run pulleys smaller than 2.8”; however, all cooling modifications with methanol injection may make it possible to see benefits from a 2.7” pulley. 2.5” and 2.6” pulleys bring the supercharger way past its maximum RPM range and will significantly reduce the life of the supercharger. Keep that in mind.

Heat Reduction, Supporting Modifications:

The increased IAT's created by running smaller supercharger pulleys can be prevented by using several available heat reduction modifications. These modifications are the dual-pass endplate for the lower intake manifold, secondary heat exchanger, and methanol/alcohol injection. At the very least, increased cooling by running the dual-pass endplate and a secondary heat exchanger should be used when running pulleys smaller than stock. These cooling modifications will help reduce higher IAT's that may cause detonation and possible serious outcomes like blown engines. It is important to use an AFR (Air/Fuel Ratio) gauge when modifying the supercharger to make sure you maintain proper AFR and do not go too rich/lean. It is also highly recommended that you get a dyno tune after any modification to the engine to optimize performance and ensure safety.

pulley information:

12 psi
bypass mod pointless
you need to upgrade
Blower speed 14,000 rpms at 7,500+rpms

3" Pulley
14+ psi
10 hp and 15 ft/lb gains**
Stock belt/idler pulley OK
no engine management required
bypass mod OK - good for additional 10 hp
Blower speed 14,000 rpms at 6,700 rpms

2.8" Pulley
16+ psi
15 hp and 25 ft/lbs gains**
belt or idler pulley modification required
engine management recomended
bypass mod OK with engine management, good for additional 10 hp
Blower speed 14,000 rpms at 6,250 rpms

2.6" Pulley
18+ psi
gains depend on tune**
belt or idler pulley modification required
engine management required
fuel injectors required

07-28-10, 01:39 PM
I came across this article prior to doing any modifications to my car. The snakebite with stage 5 porting that Steggy does takes care of the following:

Porting of the inlet portion of the housing
Porting of the internal housing
Porting of the outlet plate of the housing
Porting or Plugging of the "holes" on the outlet plate
Running a smaller pulley

The heat reduction or cooling modification can be done either using D3 products or when STS_Chiller finishes the superchiller it will be available. I am also going to be installing a front mount heat exchanger this weekend that I will post pics up. It should completely cover the entire lower grill. People can use Meth injection kit as well for additional cooling.

Obviously air intake, heads, headers, cams where not discussed in the article but they are other avenues of increasing hp. My area of interest currently is how much hp gains can be seen by swapping cams. I have read where the old northstar engines seen as much as 100hp by doing this but no one has ventured into this endeavor with our engine.

07-28-10, 01:56 PM
Its a sticky on the Eaton board so I am sure alot of people have read it. I figured it might be useful to some other people on the board who are just getting started and it is relevant to other threads on ths board, and plus its in a condensed form so you dont have to read 20 pages to see whats going on. I am sure alot of people will be interested to see how the Cam swap goes . If you decide to do it please post some pics and share the info. I am also trying to get some good info and some pics on meth injection kits and what they look like installed, how well they are hidden and the nozzle placement etc....

07-28-10, 02:51 PM
If I decide to have the rear air intake piece before the throttle body fabricated I will probably install a meth kit. I want to put two nozzles in the rear Y intake going into the throttle body. I like keeping them towards the back of the engine since it will be harder to see them (more stealthy). I don't want to weld bungs into the stock intake piece in case I return to stock for dealer visits. I like having everything available to return to stock appearance quickly and easily.

07-28-10, 03:01 PM
I believe there is a rubber coupler back there where the pipes attach to the TB. Could you just install a new one and have the nozzles installed in the rubber coupler? I realize you have alot of work done to your car so your options might differ from many of us, but have you decided on the manufacturer and or model you would use?

07-28-10, 03:36 PM
I haven't decided on the kit. I didn't want to use the rubber coupler because you need a sturdy material to put the nozzle in and the thin rubber would not hold it tightly. It is also suggested that the nozzle be placed at a 90 degree angle to the airflow path. I am not that far along with the idea of putting the meth kit on the car so I haven't really priced out the various companies. Most of the parts and extras that companies have available are interchangeable so it would just be a matter of cost vs. kit amenities.

I probably won't look further into the meth kit until I have finished the upgraded heat exchanger (planned this weekend). I think headers would be a better performance mod for my setup but the price and availability are holding me back on that one. I figure I might wait another 2-3 months before I install the kit if the new front mount heat exchanger does a good job at reducing IAT's.