what does the doghouse fan suck at ~3000RPM (CFM)?

For starters, here's a related link:

http://www.offroadvw.net/tech/wes/fan.html

The info Scott linked to is the only data on fan airflow vs engine speed that I've ever come across. I don't recall ever seeing any thing from VW (or Bentley), but that doesn't mean it isn't out there.

According to the 2nd chart, fan (doghouse 34mm) output at 3000 engine rpm is about 1000 cfm. What I found interesting is the (approx) 15% difference between the min and max figures, depending on the number of adjustment shims used. I also noticed that the 34mm fan/power pulley combo gives the same cfm as the 28mm fan/full size pulley... With the superior running characteristics (using Porsche low tension ring packs) and heat shedding capabilities of Nickies... 

awesome - exactly what i was looking for.

i might need two bilge blowers for this project.

If you're thinking of trying to convert to electric fans to cool the engine, on something that will be used more than a 1/4 mile at a time, don't bother. Those bilge blowers (and most fans) are CFM rated in open air. They won't produce anywhere near the CFM necessary to properly cool the engine when forced to push the air through the head/cylinder fins and oil cooler. They just can't create the air pressure needed.

And a squirrel cage fan would need about a 5 HP electric motor to push the equivalent of stock, and there's no way you'll supply that much power with the electrical system (over 300 amps).

What if Paul's 'bilge blowers' were meant to introduce a quantity of cooler outside air into the engine compartment mix? 

Certainly a more viable use, but I'm not sure how much better they'd be over plain ducts. Would depend on existing flow paths and relative pressures. The fan and engine are already moving the air, unless the ducts are long and narrow or have significant bends, adding an additional fan along the same path won't add a great deal. And in the worst case even act as a restriction. If you're ducting from the front, the natural air flow and pressure from driving should be more than enough, without needing extra fans.

Justin's right.

I installed ducting from the horn grill in the front to the firewall, directly in front of the fan. I put a bilge blower in line. There is no difference in air flow or cooling whether the blower is on or off.

I do notice a difference with the ducting, however, as the cooler air from the front of the car is sucked into the engine bay.

carl is right.

i have a DTM - it works well enough.  i don't have over heating issues, but i did notice that when it's cold out (~10-15 degrees C) my car feels A LOT more powerful.  A LOT.  it has to be the dense cold air

i want cooler air in the engine compartment.  i bought an inline Tstat that is triggered at 180 degrees.

perfect for traffic.

Heck and I thought it was me. I've always felt Blackie felt more frisky when it was chillier out.

I also ran a 4" duct from under the right "b" pillar to the fan inlet. I guess it helps some. I have an EMPI screen over the fan intake, too as said duct scoops up a few leaves in the fall.

~WB

Mango- Does your car seem more powerful before it's fully warmed up? If you haven't tuned the motor with a wideband it could be a little on the rich side.

i subbed out the tuning of those bloody IDF's.  i am not sure if he tuned it with a wideband.

to spare myself the embarrassment - how does tuning with a wideband work?  is that the tailpipe sniffer?

i have an O2 sensor and digital mixture gauge and i *know* it's running rich.

There are 2 types of O2 sensor, narrowband or wideband. Does your gauge give a proper range like 10.0 - 20.0 or is it one of the lean/rich only indicators? If the first, then it's a wideband, if the second then it's likely a narrowband. With a wideband it's easy to take your target air/fuel ratio and compare it to what the sensor says and then adjust jetting from there with no guesswork. Narrowband sensors are basically useless for tuning because they only work in a very narrow region around 14.7:1 AFR and are usually used for idle and light cruise trim, verifying the operation of the cat, and warning about engine problems/component failure.

I used 3" neoprene brake duct hose and some 3" PVC fittings along with a length of 3" PVC drain pipe.

I installed a 3" dryer vent to the firewall with a 90 PVC elbow. Then a short length of hose to a bilge blower followed by a longer length of hose up and around the inside of the left rear wheel well behind the splash guard. At the rocker panel I ran the hose into another 90 elbow attached to a section of drainage pipe. The pipe is tucked the between the rocker panel and the pan edge. Fits like a glove. At the edge of the front wheel the pipe is joined to a 45 then a length of hose that wraps around the fender well. 

Behind the horn grill I used a 3" square to round drainage fitting and epoxied the square end to the fiberglass. I glued a 45 onto the round end and attached the duct hose to that. I used heavy-duty zip ties and some bracing to attach everything.

All materials are available at Home Depot with the exception of the brake ducting hose. You can find that on Ebay or auto racing supply sites.

it's a narrow band.  it has 10 LED's that show how rich it is.a buddy in the local VW club has a wideband.  i'll chat with him.  thanks for the idea.