How to wire a small fan that cools my supercharger?

[HCStymie]

I have a 2Amp fan that will pump air to cool my supercharger. Need to find out how to wire it. Instructions say to wire it to the radiator fan. But that fan is not always on. So, I'd like to tie it in so it runs when the engine is running. Or in the very least so it runs when the accessories are on. Any idea what wire to tie it into?
Car is a '95 m3 with a 3.2ltr engine swap and OBD1.

https://928motorsports.com/parts/forced_air_cooler.php

[tjm3]

It's only 2 amps but I would wire it through a relay and find a switched circuit in the fuse panel and tie into one of those. It usually takes only about 100ma or less to switch a relay so it shouldn't affect anything you tap into. Get a good relay with a clamping diode or resistor, usually shown on the relay case. And make sure the circuit is fused.

[pbonsalb]

I agree with the above. Splice into a switched wire as the relay trigger if you want the fan to run when the ignition is on.

[HCStymie]

I didn't really know what all that means. So, while looking into it I found the option to add a fuse tap and figure I could tap into some accessory related fuse. Although I might have to learn more about the relay wiring anyway since nothing is straight forward in the fuse box with all the control modules crap. I've seen fuses effect multiple things even when not everything was listed for it.

[pbonsalb]

Fuse tap is an easy option. The ones I have used don’t fit our fuse box very well and you will still need to get out of the fuse box. Fuse box would at least be close. I ran a power dyne for a year. Then a couple of different vortechs for a few years. Turbo since 2010.

[HCStymie]

Good choice getting rid of the powerdyne. They suck, but that's what I have. Car's been a money pit so don't want to put out for another supercharger, or even more for a turbo. This extra air cooling for the powerdyne should help keep the bearings going.

When I looked at the fuses, it looked like my best bet would be to run the wire down where the relays are and come out the bottom. Haven't tested the clearence in the box yet for the rap. But no matter what, would still be better than rebuilding the powerdyne again...

[pbonsalb]

I assume you have the Dinan with the drilled vent holes and chicken wire mesh? And are using ceramic bearings? And not over tensioning the belt. Also consider running 2 bypass valves — the plastic Bosch ones.

[Braymond141]

I assume you have the Dinan with the drilled vent holes and chicken wire mesh? And are using ceramic bearings? And not over tensioning the belt. Also consider running 2 bypass valves — the plastic Bosch ones.

Two? They don’t even come with one! Good idea though.

[pbonsalb]

Dinan ran such low boost it said the bypass valve was not needed. Others say not having one is harder on the bearings. The Bosch ones are small. One company years ago ran two. I ran 2. Plumbing was a pain.

[NeilM]

I have difficulty imagining that a such a small fan (2 amps at 12 volts) is going to deliver meaningful cooling to the SC. There’s already plenty of air movement under the hood — the problem is that it’s hot air. I’d look at ducting fresh air to it instead, similarly to how BMW cools the alternator.

The 3” flexible duct that’s often used for brake cooling may be a bit bulky for engine compartment use, but the same stuff also comes in a 2” size.

Neil

[pbonsalb]

Dinan ran a 1 inch hose to the blower and relied on the blower spinning to such air in for cooling and vented the top of the case. Even a low power fan helping get air in would be useful. Keep the blower rpm low (low boost) and it should be ok. But if you like power you will want more. Centrifugal are so predictable you will soon want more. And the powerdyne can’t drliver it. Better to go turbo sooner rather than later or buy a different car.

[Braymond141]

I have difficulty imagining that a such a small fan (2 amps at 12 volts) is going to deliver meaningful cooling to the SC. There’s already plenty of air movement under the hood — the problem is that it’s hot air. I’d look at ducting fresh air to it instead, similarly to how BMW cools the alternator.

The 3” flexible duct that’s often used for brake cooling may be a bit bulky for engine compartment use, but the same stuff also comes in a 2” size.

Neil

He’s trying to cool the transfer case of the supercharger. As long as he has the vents that Dinan did, this should work out better than no active cooling.



Dinan’s cooling method here

[HCStymie]

My powerdyne is from an E.R.T. kit. Similar to the Dinan one but not quite the same. Mine does come vented with two 1/2" NPT threaded holes.

Since I drive on the highway consistently around 80mph (About 3400rpm) or get stuck in NJ traffic, I figure it couldn't hurt to get some extra cooling to keep the bearings from crapping out. Already rebuilt mine twice (first rebuild had defective bearings). The cooling fan I am going to mount in front of the radiator fan (behind the kidneys) so it will pull in the cool outside air. The 5/8" hose fits around the radiator without crimping so that will go to an elbow on the supercharger like the Dinan picture above.

Originally I thought my bearings were dying a 3rd time since the impeller was scraping just a little on the scroll. Figured out it was from the #%*&@ Jersey City mechanics not putting the supercharger back on correctly and having to pull on it to get the hose between it and the intake manifold. Moved the scroll out of alignment just enough to cause some light scraping.

Reason I said before that powerdynes suck...
1. Everyone else uses thrust bearings, where powerdyne uses ball bearings.
2. Has a low pique and constant rpm compared to others. (just driving 80 on the highway was more than the constant rpm rating for the stock supercharger)
3. Their machining tolerances weren't very good at times.
4. The guy who started powerdyne wanted to prove that a belt driven supercharger was as good as (maybe better) than no belts. Turned out to be wrong.

I have the super powerdyne rebuild if any one is curious.
https://928motorsports.com/parts/superpowerdyne.php

This is the fan link again.
https://928motorsports.com/parts/forced_air_cooler.php

[pbonsalb]

I’d be curious to see what one actually will do in terms of power on an S52. You would need a bigger crank pulley so your blower pulley does not have to be tiny.

[HCStymie]

The pulley on the supercharger is 2.93". They make other sizes but the main issue is the bearings they use can't handle the higher rpms. I should still have room but not going to risk another failure. On the original supercharger set up it had ( with some additional mods like highflow exhaust) I had 308 rwhp. Which comes to 352 to 375 hp from the engine when accounting for powertrain loss. That was before 2002 when I bought the car.

The claim is that the superpowerdyne rebuild can add up to 20% more boost.

With intercooler, High flow throttle body, bigger crank pully and/or smaller charger pully, higher octane gas, etc, I'm sure you could get rwhp over 400.

[pbonsalb]

It will slip if you go smaller. You need to run a bigger crank pulley. You can do that only if you gave a dedicated blower drive on the crank pulley.

[HCStymie]

The supercharger has it's own crank pully. I forget what size it was off hand. I want to say 7" but not sure without looking. Don't want to go bigger. Would rather not have to deal with issues in the future than have more power. Besides still have a few more things to do after the supercharger is back on...

You might find this interesting. I think the powerdyne max rpms is the pique number. I believe the nominal is 36K on their original bearings in the BD-11A. But don't quote me on that. Maybe that is for the BD-10 that is not listed? Can't find full specs on their stuff. I think the SKF upgrade was 42K nominal and 60 Pique. 928 Motorsports custom bearings say 46K so I assume that is nominal.

http://www.superchargersonline.com/i...page=page&id=9
http://www.superchargersonline.com/i...page=page&id=8

[pbonsalb]

You are smart to stay conservative with the powerdyne. Despite your upgrades, it probably won’t be reliable if asked to make anywhere near the claimed 1200 cfm airflow or operate anywhere near the claimed 46k rpm. Plus you should run an intercooler if you want much more boost than 6-7 psi and you should be running a compressor bypass valve.

Your crank pulley is probably in the 5-6 inch range. The math is (crank pulley diameter divided by blower pulley diameter) times 3.05 times engine rpm. 3.05 is the internal step up ratio. With a 7” crank pulley, you would be a 51k blower rpm at 7000 engine rpm.

[NeilM]

He’s trying to cool the transfer case of the supercharger. As long as he has the vents that Dinan did, this should work out better than no active cooling.

Yeah I understand that, but hadn't followed the link. The OP had referred to it as a fan, but that's a fully ducted blower setup that should help.

Just keep the hose run as short as feasible and make sure the blower inhales outside air, not engine compartment air.

Neil

[HCStymie]

Responding to a few posts...
The fan will be mounted behind the grill and the hose fits through around the radiator. Getting cool air to the Powerdyne case.
I checked, my crank pulley for the supercharger is not near 7" like I thought for some reason. (I had done the correct calculation years ago but forgot). The pulley is around 4.25" give or take. Hard to get an exact measurement since my calipers aren't long enough to fit around it.

Here's what I want to do about the wiring for the fan. Use an empty fuse slot in the fuse box and wire it to there. Have had a heck of a time trying to find the right connector for it. I think I need #5 in the link below. I think the number range is for the diameter of the wire it holds. AG/SN is silver or tin plated. I have some 14 guage wire which is about 2.6mm with insulation. So any 1.5-2.5mm one should work.....I hope.

https://www.realoem.com/bmw/enUS/sho...diagId=61_4907

[1000hp]

My Powerdyne broke over and over. I don't think there's anything that you can do that will keep it alive long enough between rebuilds to be worth the effort.

I hate to jump on the bandwagon, but I suggest you start saving for a Vortech and never look back.