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Cats out of the bag, Supercharging the L20b.


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I've been working on this project for over a year now (work and such slows down progress)


My setup is getting close to being a possibility now, but i'm beginning to be hesitant. or even borderline confused on tubing size needed. I think I WAY over did my intake so far.


I'll copy and paste some questions I posted to a supercharger forum as well. but I plan to run a 1.75in single SU into my eaton m62 charger, then into my l20b 30 over with a open chamber a87 head, 1mm oversized intake valves, and mild port work.




there is a TON of numbers and math, and possibly some voodoo in this next part. (will add to the next post as I can't seem to copy and paste on here these last couple weeks)



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ive been toying with picking up a Mazda millennia ihi supercharger to play with. I'm interested to see where this goes.


Are other pulleys available for this supercharger? Since its an Eaton, can you use Pontiac pulleys?

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not sure if I can use Pontiac pulleys or not, but yes there is other options. i'll stick with my pulley setup and see where I actually land, but i'm sure i'll want a bit more. and 3.44psi is if things are perfect, obviously that won't be the case, so it'll likely be lower than that.


I expect I need to cut off my 4in "log" and go from the SC to the runners with something smaller, in the range of 2in. but i'll see if someone can chime in here with more knowledge.

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Being as that is a Mercedes M62, no, none of the aftermarket pulleys will fit. Also the clutch burns up easy and is about 300 bucks to replace...that's the reason a lot of those chargers end up on eBay.


The 4 inch plenum is just fine. Nothing to worry about there. The 1.75" SU will probably be ok at 3.5 psi, but the Eaton charger is not designed for draw through and performance with suffer.


Get that boost up into the sweet spot for the Eaton. Minimum 5psi, target 8psi or you may end up making less than stock power...for the M62, 10 psi "wide open" takes 35hp to spin the supercharger. 32hp to make 6psi, 30 to make 3hp. Going over 10psi starts to turn your Eaton into a Heaton, and intake temps will go up.


Also you will need to incorporate the blower bypass valve or the blower will get HOT at idle...even with the draw-through, trying to suck 62 cubic inches of air every supercharger revolution through a 1.75" carb will cause the blower to heat up. The fuel flow will be enough at mid-rpm and higher, but please probably won't cool the rotors at idle.


For reference, an M62 on a 3800SC Pontiac will overheat and seize at idle in 9-10 minutes if you lock the bypass valve closed...

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I ran an air to water intercooler inside my 7M blower build.







And a Greddy bov for a bypass valve.


Mine was an M90 from a Ford Super Coupe.

Threw the clutch away, and ordered a custom snout from Magnason (the people who sell the Eaton here in the states).


If your blower has the mechanical coupling between the input shaft and the rotors, replace it with an aftermarket polyurethane couplings.



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This guy outlines swapping a Pontiac snout on to an mb supercharger. Cuts pulley diameter nearly in half and opens up the aftermarket. Hopefully this is helpful to you.



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that air/water cooler is beautiful!


why is the eaton not designed for draw through?


I am basing some of my projects theory on a friend (Datsun guy) who is using an m90 on a jeep 4.0 and a 2in su.


are you saying if I use a bypass valve, it will alleviate the possibility of overheating?


I have toyed with the idea of water/meth injection as well. but i'm attempting to keep things simple to start.


I agree I need to get the boost up to 8-10psi. not looking for any more.


it isn't to late for me to switch SC's just means fabbing up a new mounting bracket (which I could do better than I did the first time anyways)

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The Eaton blower has coated rotors that do not like fuel or alcohol, the coatings sludge off. Doesn't hurt the blower for draw through but what does is the restriction on the blower. You want it to pull air from the least restriction possible,or it's adiabatic efficiency drops rapidly.

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The diameter doesn't matter directly, it is the cross sectional area and minimum cross sectional area that matter. They need to be correctly sized for the engine displacement and cylinder head flow-too big and the engine is slow to respond, sluggish to rev and just generally "floppy". For an l20b with no port work, 1.5 inch diameter runners are the largest recommended. However, positive displacement blowers, like the Eaton, generally respond well to larger port volumes-so 1.75 inch ports would be too big, but not unworkable.

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Velocity of airflow. One of my links explains size of tubing for a "charge pipe" and how size and speed effects effiecency.


Also! Just reran some figures. My crank pulley size was incorrect. It's more in the realm of 6.25" which changes my boost PSI to 4.55@6k rpms. Still not optimal, but better.

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