If anyone wants to know why I am doing this refer to the post "Supercharging on the cheap".
To that I will add that I believe I will prefer the low end power potential of a roots type blower.

I have an 87 S4 Auto.

My question to those experts mentioned and anyone that can answer is:
Where in the system can I place the Eaton M90, a fixed displacement blower? Specifically can I place it before the MAF? Can I place it before the throttle? I am not going for a lot of boost here. My goal is about 50 horsies for about 1000 Washingtons. A great bang for the buck for our cars.

I have the book Supercharged! by Corky Bell, Bentley Publishers, 2001. Below are the only 2 paragraphs on the subject of throttle placement with roots blowers in the book, by which I am confused.

"Throttle Placement
Because the Roots is a fixed-displacement supercharger, the throttle is customarily mounted at the compressor inlet. Without the design complexity of a bypass valve this becomes a necessity. If the throttle were down stream, closing it would cause a buildup of pressure between it and the supercharger, forcing it to stop and wreak havoc on the belts. A technique for blowing into the throttle with fixed displacement superchargers has been developed but is not yet available in the aftermarket.
Certainly, in many circumstances, including a bypass valve will be easier than relocating the throttle. However, the closer the throttle is to the intake valves, the more crisply and responsively an engine will run. It is currently popular to use the bypass valve yet leave the throttle in front of the blower."

He seems to say that you can use a bypass valve and put the blower in front of the throttle. He seems to contradict himself though. What are your thoughts?

As for the MAF, I see that the centrifugal kits place the blower before the MAF, but I realize this may be different for a fixed-displacement.
Your facts or thoughts are needed here.

For those interested:
As far as drive and mounting goes, I will have to modify the hood. I have a good portion of a bracket template made. It mainly uses the engine lift point bolt holes on front and back of either head. I’ll probably use cold rolled steel. It will be driven off of the power steering pulley or the smog pump with custom pulleys made depending on the side of the engine it goes.

Thanks in advance for your help.

Andy K
<img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

 

Andy,

You can place the blower before your MAF. Make sure you have the bloww-off valve before the maf though. If you don't, the engine management system will have already counted the air coming in and adjust the fuel to meet the air creating an overly rich situation that could wash the oil for your cylinder walls and ruin your engine. I would add a rising rate boost sensitive fuel pressure regulator to richen the fuel system. I bought one form these guys <a href="http://saabperformanceparts.com/prod014.htm" target="_blank">http://saabperformanceparts.com/prod014.htm</a> and the thing is absolutely beautiful. Their new model is all billet aluminum.

You should have picked-up an Eaton M112 blower instead of the M90. The M112 is made for the larger displacement engines. If you spin that M90 too fast, you will create too much heat or your teflon seals will separate and grenade your engine. DON'T SPIN IT TOO FAST! Before the M112 many larger displacement engines actually used two of the M90s. I know Eaton rates this to handle a 5.0L engine but it will not be as efficient as a larger unit spinning slower.

A 50 horsepower gain is a bit modest. You should pick-up an additional 100 to 125 horsepower with little problems and as long as you keep the boost below 7 psi you shouldn't need an intercooler. You could mount the unit on its side in your engine bay and fabricate the intake and outlet to fit.

Good luck,

Jim

 

Thank You Jim. Your comments are in line with what I wanted to hear. I'll take a look at that BSRRFPR.
The thing about the M90 is that it is easy to find and cheap. There were 5 at the 1st salvage yard I went to. If I get this working well I can later convert to the M112. Or maybe I'll just put another M90 on the other side of the engine .
I will be taking my bracket templates to the machine shop and hope to dry test the mount by this weekend. As you suggest the blower will sit brobably tilted to it's side and above the passenger's valve cover. I anticipate a 4" buldge on the hood if I proceed.

<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

 

Hi,
This all ounds interesting...
Would this work on my 82 Euro S CIS system
How and will the mounting be different to how you explained?

will i need any other mods?

 

Sparky,

I really don't know much about any other 928 besides the 86.5 and 87. I don't know a lot about those either. A fellow by the name of Quick Carl put a centrifugal blower on an older car w/ CIS. Some details are posted in a thread started by him. Try searching Carl and Supercharger. If I recall Jim Nowak mentioned in that or another post that you can not blow through CIS with a fixed displacement blower.
HTH
Andy <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

 

Andy,

After further research and blower applications first hand, I will reverse what I said in earlier posts about the positive displacement blowers and CIS. I now feel with a large enough blow-off valve, may take two, you could place a positive displacement blower on a CIS.

I was worried the CIS metering plate would pegged down with the positive pressure. However, I know that even with 3 to 6 lbs of boost in the intake at low rpms the blow-off valve will vent enough so the CIS plate will not be pinned. I know this because I have adapted a supercharger system to my 560 SEC, with CIS, and I run in excess of 10 psi of boost. The car is a absolute monster compared to stock.

 

Andy,

How about sending me your email. I would like to have my supercharger installed and operational by the end of Jan, actually X-Mass. (It's my X-mass present to myself)

I have a few questions. I have been in contact with Jim as of today. Any help would be appreciated. If, anybody else has suggestions here that would be great as well.

Prior to SC my engine, what should I ensure about my engine? I have less than 2500 miles on new timing belt and water pump. Should I have any head work? I have a person willing to machine my brackets for me.


John D.

 

Sparky,
With Jim's added comments on the CIS system it may be something for you to consider. Again I have no experience w/ the 82 Euro.
The only cars that I think the mounting would be very diferent on is the 85 and 86. They have the very wide intake that covers the valve covers. I have thought that it may be easier with the spider intake of the older cars because you may be able to put the blower directly under it.Huntley Racing is making a kit that does this. And there seems to be atleast as much if not more room under the hood of pre 85 cars.
I don't know if you will need other mods.

Jim,
Is there a difference between Bypass Valve and Blow Off valve? If so can you explain? In my readings Bypass seems to go with SC and Blowoff seems to go w/ Turbo.

Dozman,
The kits I have read about seem to make me think the only things that really have to be done are larger injectors and an adjustable FPR or Boost sensative FPR as Jim suggests. This is assuming that the car is up to maintainence spec. with no issues.
In my case the car is up to maint spec. and has almost no issues at 112k mi and is strong. Before I start driving it with the blower I will have someone look over the car and my work though. I don't know who yet.
Where should I send My e-mail address to?

Andy
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

 

My email is PSI_101@hotmail.com

I think your right about room. I have removed my smog pump, and I will be installing an electric pusher fan. I hope by some chance that will create some much needed room.

Does anyone know that by reducing the sizes of the air boxes for an '85 will hinder the performance of the engine?

John D.

 

Not that I have any experience with the superchargers, but my car does run 8.5 psig of boost with an intercooler and two IHI turbochargers.

My air flow meter is on the pressurized side and I have a microfueler piggy-pack enrichment system blowing through two additional injectors under boost. Fuel pressure is stock as are all 8 engine injectors....Callaway installed high flows, but it was too rich!!!

If you need more info on fuel system mods, just let me know. I also have installed an adjustable, pressure sensitive fuel pressure regulator. With the supercharger, you can probably use higher flow injectors at all 8 ports, snd jack around with the pressure a bit to get it close. With a turbo it is different, because it doesn't make boost all the time like a blower can.

My car makes about 400 HP at the crank on 8.5 psig.

 

Thank you for the reply John. I will call on your knowledge here and now.
My thoughts on the fuel system are as follows. Jump in if you see anything wrong. Others are welcomed to jump in too.
I guess the first things I should install after I get the blower mounted and working are an air fuel meter and a boost guage. I plan to use a V-belt to turn it at first, as I have heard from a very reliable source that a V-belt will work fine with good wrap and tennsion up to 4psi on the M90. If at 4psi the misture is not good I will add the Adj and/or Boost sensative FPR. If mixture is too lean after that I will go to larger injectors, ala motorsport at $25 per each.
If the fuel sys requires more than that I will sell blower and brackets and call it quits.
Thanks for your help.
Andy K <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

 

Andy,

Blow-off valve and bypass-valve are the same in my book. If there was a difference, the bypass valve would dump the air back into the plumbing and the blow-off valve would vent to the atmosphere; however, functionally they operate the same. I tried both on my supercharged SEC and thought venting to the atmosphere was the way to go. I didn't see any difference in the two set-ups but venting to the atmosphere makes the plumbing easier.

 

Thanks Jim.
Yep, I guess I just figured that out tonight.

Here is my quandry now. A tech from Magnuson says not to blow into the throttle as it could (will) damage the throttle. I don't see moving the throttle on the S4 as easy thing. What if I used 1 or more blow off valves that could adjust down to 4psi after the blower and just before the MAF sensor and throttle in their stock placement? It is hard for me to believe that a 4 psi build-up before a closed throttle could damage it. Don't the centrifugal blowers have some major pressure build up before the throttle durring deceleration? What are your thoughts?
Thanks,
Andy K
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

 

Andy,

If you are worried about pressure build-up, run two blow-off valves. I'm running 10+ psi in my system and I havent had any problems with damaging the throttle body......and I don't drive like a grandma either. Now, I have had the CIS air bellows literally blow-off the throttle body and had to bolt the CIS to the intake but no throttle body issues.

 

Thanks Jim.
That will be my plan then, using 2 blow-off valves. If that dosent work I have one more cheap trick up my sleve.
Andy