Superchared diesel inside here...

[seawalkersee]

And for the pix of the tensioner. From these, you can see that it is too far forward. Aparently, while measuring by thumb, my thumb shrank and I am about a half of a rib measure off...So is the belt.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

SWS

 

[MUDKICKR]

the reason you have no boost is due the the supercharger not spinning fast enough, the reason for the supercharger not spinning fast enough is due to the belt routing, you need to separate the belt system like it is on the factory. that way you will know that the supercharger is spinning fast enough.

 

[seawalkersee]

Not true. I can speed up the pulley the same way as the routing I have now. I just need a smaller pulley. Even if you separate the belts, you will have to have a step up pulley (AKA Jackshaft) so it can speed up the SC. I know I need to spin it faster, but with time being short and a few other things, I will hopefully get to it this month.

I am in the process of doing some other stuff too. I am adding some support to the floor and fixing the rear access panel, as well as adding some sound deadening to quiet it down. Making new door panels and getting the same done there.

I have to go back and lower move the pulley or whatever you want to call it, to put the pulley closer to the mount so the belt is on it correctly. Probably today.

SWS

 

[seawalkersee]

FWIW, I got with my grinder and weldor today and lowered/cut the manuel tensioner down. I needed to lower it about 1/8". I ground down the mount and put it back together. THAT portion of the belt setup is now complete.

SWS

 

[MUDKICKR]

Not true. I can speed up the pulley the same way as the routing I have now. I just need a smaller pulley. Even if you separate the belts, you will have to have a step up pulley (AKA Jackshaft) so it can speed up the SC. I know I need to spin it faster, but with time being short and a few other things, I will hopefully get to it this month.

I am in the process of doing some other stuff too. I am adding some support to the floor and fixing the rear access panel, as well as adding some sound deadening to quiet it down. Making new door panels and getting the same done there.

I have to go back and lower move the pulley or whatever you want to call it, to put the pulley closer to the mount so the belt is on it correctly. Probably today.

SWS

i didnt say it was impossible to get the right speed out of the system as is, but you would be better off doing it as the factory had it. it would be simpler, easier to work with, and be much better to adjust pulley size.

 

[seawalkersee]

Okay, but I am neck deep in this project. There is nothing off of which I have to work here as far as the placement of the pullies and such. I am not sure where I will be able to put the pulley though. The only way I can think of doing it now is to add a front pulley to the alt and move the blower forward. Not really sure what I am going to do right now...I want to get a different setup for the blower pulley and see if I can get PSI.

SWS

 

[MUDKICKR]

your doing a good job, no complaints here, but id see if you could mount a similar sized supercoupe crank pulley to your existing crank pulley, then move the supercharger forward. then run a jackshaft pulley under your alt, and see what happens. i dont think id try to mount a pulley to the water pump due the the stress it would add. but if you could use all the factory pulleys i think you would be a lot closer to your goal. if using the factory pulleys and factory setup you would def. know where you need to go with this project.

and i do think your doing a good job. just have to tinker with it and see what happens.

 

[88 Ford]

SWS, what size of pulley is on there right now? I can't remember. Lol

 

[88 Ford]

Here is some math the 429idi did a while back when I asked him how to calculate cfm and also boost for my M112. Maybe this can help you.

"The math is pretty simple.

420 cubic inches
3300rpm. (use 1650 since it's a four stroke)
1728 to convert cubic inches per minute to cubic feet per minute.
.85 estimated ve

420x1650=693000/1728=401cfmx.85= 340actual cfm@3300rpm

The m90 is called that because it moves 90 cubic inches of air per revolution, so you just figure it like an engine. Of course superchargers, like engines, are not 100% volumetric efficient.

90x12000=1080000/1728=625cfm An m90 has an actual flow at 12000rpm of 535cfm@10psi and ~550cfm@5psi

None of these figure for thermal expansion due to temperature increase, but they will give you an idea."

Here is the info for boost on the M112:

"The actual flow was not calculated, I have the blower maps on my computer.

To make 10 psi at 3300rpm you will need ~40lbs/min of air flow. 40/.075=533cfm. (a cubic foot of air weighs .075lbs at 70 degrees)

An m112 needs to spin ~9800rpm to flow that.

9800/3300=2.96

7/2.96~2.35" pulley

The crank pulley is 7", 2.96 is your sc to engine ratio.

2.96x112=332 cubic inches per engine revolution
332/210(half of 420)=1.578 pressure ratio
1.578x14.7(atmospheric pressure at sea level)=23.2psia
23.2-14.7=8.5psi boost without figuring for temp increase, and the s/c has a higher ve than the engine, so boost would be higher. In a real world setting, it would be 10-11 psi boost.

The unfortunate thing, is that you probably can't get a pulley that small. The smallest one I have seen is 2.7", which will give you ~8psi."

 

[88 Ford]

So this is how I understand it for a M90. The max rpm on the M90 is 12000 rpm. So the SC to engine ratio is:
12000/3300=3.64
So if your crank is 6"
6/3.64=1.65" pulley Which is really small!

3.64x90=327 cubic inches per engine revolution
327/210(half of 420)=1.557 pressure ratio
1.557x14.7(atmospheric pressure at sea level)=22.9psia
22.9-14.7=8.2psi with a 1.65 pulley

Does that sound about right? And with a pulley that small would you run into slippage issues?

Edit: I think that also means that at max blower rpm the M90 will only hit 8.2 psi depending on temperature and different factors like air density correct?

 

[88 Ford]

Also here is the flow map of a M90:

 

[seawalkersee]

I can't use the factory SC crank pulley. The bolt pattern and the hub are different size. I was going to get a large front crank pulley, but there is not one that I can find that is much larger than the factory one. Now, I have one for a 5.0 CV/GM that has a fairly large front crank, but again, there is a different crank and hub size.

The pulley size is only a little bit different than those of the SC. If I would have been thinking, I would have checked it against the crank pulley and seen that I needed to increase the speed.

SWS

 

[88 Ford]

Was my math correct? Even if you used say a 1.65" pulley or say a bigger crank pulley, wouldn't the M90 only be able to produce 8.2psi on a 7.3? Cus that is calculated at max blower speed... idk there are different factors involved as well but 8.2 will still make a lil power and isn't too far off of the 10psi that you originally wanted too...

 

[seawalkersee]

The problem is that those sheets are not totally correct for all applications. Remember that boost is a measure of restriction. So, technically, if you have a blower that pushes out 10 psi and a lot of work gets done on the engine and exhaust and that same blower at that same speed only produces 6 psi. (remember this is in theory only), the engine is going to make more power even though it shows less psi. I am not sure how much I can increase the size of the crank pulley. I know it will not be a lot becaus of how close it is to the waterpump pulley. So, I am going to run a shrunkin SC pulley when I have a chance to figure out how to get it together....but as for now, I have an idea that I think will work...and that is more than I had a week ago.

SWS

 

[Fordman75]

I was afraid you'd have issues making much of any boost with the M90 on the 6.9L. I've seen guys struggle to make 5lbs of boost with them on the 300's.

I don't know if you'll be able to go with a small enough pulley on the Eaton to make it work. It might be time for a jackshaft. Or maybe a gear drive set up like some of the centrifugal superchargers have.

I'd like to see someone try a Shelby GT500 H122 Eaton on a IDI.