mhuppertz

i'm going to go get my 4BT from storage and see if the bolt layout on the head and block are the same as on my 6BT. If they are I can mock up my blower mounts on that dude.

TRENDZ

You need to turbocharge your supercharger, not supercharge your turbo.
The blower will only ingest the amount of air the pulleys allow for. It is a positive displacement pump. This means that engine rpm dictates airflow.
If you agree with that, than ask yourself what good a turbo would do AFTER the blower. The turbo would only act as a restriction on inlet and outlet. The turbo can not output more air than it is fed, and since the turbo is fed by the blower(no more/ no less) it will just be along for the ride.
If you plumb the blower AFTER the turbo, you still get the low rpm air flow you want, because the blower can pull air through a turbocharger, plus the benefit of being able to compress the air entering the blower, effectively making it "bigger".

mhuppertz

The main reason I am not doing it the way you state is because of rotor deformation at high boost levels. The rotors were not designed to handle as much boost as they would see if they were being pressurized by the turbo, and they tend to deform and sometimes break. I do appriciate yout insight, and I think if I was using a screw type or centrifical supercharger I would agree, but roots type just don't like that setup. I will bypass the blower as soon as a vacuum starts to form in the downtube to the turbo, so I will have the best of both.

JQmile

You can only get away with about 15psi into the supercharger before the rotors start flexing and the blower starts leaking oil....also, when blowers have to produce a lot of boost, they take huge power to drive. 30psi at 4000rpm might take 200-300hp just to drive the blower.

mhuppertz

Yea, that's why I am just using the super to light the turbo. Like I said, having boost before the turbo lights should really make for a fun (and hopefully more efficient) ride!

Also, I might actually be able to fuel more than I am now without smoking like a coal train. The more I think about this setup, the more I think it will work really well. On top of it all, I have yet to install my Snow Water/Meth injector system.

JQmile

It'll be interesting to see how it works......from what TURBOLVR told me, you should see the turbo spool 300-500rpm sooner.

mhuppertz

I am hoping this smallish Supercharger will be really efficient at lower spin rates so I can light my turbo even sooner than that. I'm shooting for 600-700.

mhuppertz

Honestly though, I don't care about the RPM's as much as the sheet time it takes to spool. If I am on the freeway going 65 in 5th and floor it, the turbo takes 4 -5 seconds to light, and it is smoking like crazy until then, which is a tremendous waste of energy.

TRENDZ

In a situation where there is a HUGE differential pressure between blower inlet and blower outlet, you may be right about rotor flex. In This application, not so.
Here is what will happen when you put this supercharger first:
Depending on pulley ratio, you will get to a point where the blower isn't flowing enough air to keep this engine happy.This blower moves 90cu inches of air per revolution. your engine displaces 180 cu inches per revolution. a pulley ratio of 2:1 would be needed just to make it flow enough air to make N/A power. A pulley ratio of 4:1 would get you around 15psi. I'm assuming you agree with this since you believe the turbo will take over at some point. The problem is the turbo is not going to "produce" air if the blower cant supply it more air. The engine will be ultimately limited to what the engine would make for power with only the small blower.
If you run the turbo before the blower, you get an unlimited atmosphere for your turbo to draw from. The blower will not limit you in power because it is no longer working to pull in air, it is being somewhat driven by the turbo (less differential pressure between in and out).
I cant comment on oil leaks with this supercharger. I know you can do it with an original detroit/roots, with sealing technology from the 1940s.
Take a look at the truck in the vid. It is working.

mhuppertz

Not trying to be continuous, but roots cases were not designed to handle being pressurized to that level. I have personally seen them leak just from over driving them too much, and that’s without pressure in the inlet side. If the pressures blowing into the supercharger never exceeded about 20 PSI, then I agree there would not be a problem, but I am running 40PSI at this moment, probably a lot higher with water/meth, and that will grenade a roots type supercharger.

It is true that my turbo will outstrip the small roots I am using at higher RPM, and that is why I am going to install a spring loaded vacuum flap that will allow clean air from the BHAF to be drawn in to supplement as needed. I think this is going to be a hot little setup, but the proof is in the numbers, so we’ll see.

TRENDZ

I sincerely hope it works for you. You have a nice truck there, and it would be great if this succeeds. Sorry for my ongoing pessimism...

mhuppertz

Don't be sorry! You are forcing me to re-evaluate and that is good! I appreciate your input.

12v85k30

And make sure you do some math for your pulley btw there are OE pulleys for cummins engines (not 6bta) that are 8 and 9 inches wide but heavy cast iron 8 rib only nice becaujse they are cheaper. If you under pulley your super, your turbo and engine arent happy. Mine is ATM-turbo-super-ic, on a ve pump

mhuppertz

Did your super make a big difference in power?

12v85k30

im planning on swapping pulleys today or monday then ill get back with you, right now its a pig! ive got a 66/19 under it and with the super spinning so slow it is a huge restriction