Supercharging non-FI engines: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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July 27, 2010 3:01 p.m. mrwillie Reader

I understand the thousand foot view of whats needed to add a turbo to a non-FI car, but how do you go about adding a supercharger? Aside from custom work, how do you make pulleys, intake manifold fit if you're going from a supercharger from a larger engine down to a 4cyl? Reason for asking, I found this, and it has me thinking.....

http://raleigh.craigslist.org/pts/1865760975.html

This is just hypothetical, but would this work on say.... an 8v vw engine? Is it as simple as grabbing brackets off of an g60( vw's attempt at supercharging ) and plug and play? Like I said, this is simply bench-modifying at this point.

What say you, GRM???
July 27, 2010 3:04 p.m. 93celicaGT2 SuperDork

That supercharger would be a bit too big.... I'd say you should be looking at an M62 at most.

As for the rest? I'm not really 100% positive, i've only just started reading on this stuff myself.
July 27, 2010 3:19 p.m. pres589 HalfDork
1. Why are you wanting to mix carbs and forced induction? Is this for street use or drag racing?
2. You either put the carb in front of the blower and have it suck air & fuel through but that doesn't really do anything good for pulling liquid out of the air/fuel mix, but it does let the fuel cool the air charge so that's kind of nice. Or you put the carb after the blower and you get to do stuff like pressurize the float bowls and try to seal the thing as best you can OR put it in a sealed box so it's encases in pressurized air.
3. I would either try to recreate the G60 setup as much as possible but with a Megasquirt for control, or else full custom setup and use a Megasquirt for control. I don't think you could really use much G60 hardware unless you were trying to recreate everything the factory did.
July 27, 2010 3:21 p.m. Streetwiseguy Reader

Dunno whether there is an issue with running fuel/air through a blower designed for air only. I doubt it, though. I've got a B&M 142 blower on my Camaro, which is designed for a spreadbore carb to bolt right on. I use an adapter plate and a square bore Holley, and I often thought about practicing my aluminum welding skills by modifying a Volvo B23 intake manifold to accept it. As set up, it makes about 7psi on a 350 with poor heads. With forged pistons, I could change the pulley ratio to get up around 12psi. With all else being equal, it would produce about 3 times that boost on an engine thats about 1/3 the size. I think it would be fast. For a very short time, probably.

The fuel map and ignition advance are critical on a blown engine, and when working with a carb and mechanical advance, you've got to creep up on it, starting out rich and conservative on the timing. Hopefully it just melts the electrodes off the plugs when you go one step too far.
July 27, 2010 4:13 p.m. mrwillie Reader

I'm sorry. My orig. post was confusing. I meant non-force induction( should have said NA, my fault ). The engine in the example uses the old CIS fuel system( mechanical fuel injection ). I guess sizing would be the biggest deterant here??
July 27, 2010 4:51 p.m. njansenv HalfDork

You could turn it slower.
July 27, 2010 5:00 p.m. mad_machine SuperDork

I know the Lancia Volumex cars used a pull through carb before the surpercharger.

I also know of an E30 325 with an M90 on it
July 27, 2010 6:13 p.m. turboswede SuperDork

Well, with CIS, you could simply plumb the outlet of the CIS to the inlet of the supercharger and then into an intercooler or the intake. Just make sure to know whether the supercharger requires fuel running through it to protect the seals from excessive heat.

The CIS should adjust (within its range) to the added vacuum.

If you look at the CIS system used on the S1 924 turbo's you can see what they did to get that to work from the factory on the Audi 8V 2.0L.

Since superchargers are more linear in their power delivery, in some ways they are slightly easier to tune for since you'll know what boost you'll be running at a specific RPM.