Electric fan for cooling? Options

[teamgravy]

We are building a track car for endurance racing in Lemons/Chump Car series from a 74 914-4 1.8/carb converted. Rules state we have to spend no more than $500 on the car minus the safety equipment (seat, cage, tires, wheels, brakes, etc..)

I am thinking of leaving off the 914 cooling system and much of the engine tins and running a electric fan to cool the motor. The fans are cheap $70 for 2100 CFM fan and I can also use some big ducting to cool motor at speed. Elec is free (no night racing) right and no HP drain. Just loosing the 50lbs of fan/ducting on the front of the motor seems worth it.

I would build a shroud and use some of the existing tins push air across the jugs and heads. I would relocate the alternator above the oil fill/breather and run it off the small AC pulley that was behind the fan. Would love to buy a DTM or Fat 911 conversion kit but not allowed in budget.

I was wondering what the peanut gallery thinks of this.

Is this going to give me cooling issues?
Will ALT function from smaller pulley?

Thanks!

[teamgravy]

Plus the motor looks much cooler without all the ducting, heat exchanges and tins.

[SirAndy]

Elec is free (no night racing) right and no HP drain.

There's this pesky little thing called "Physics" that disagrees with your statement above.

Unless you have an extra battery that can power the fan for 24 hours without an alternator to recharge it.
As soon as an alternator is used to generate the electricity to run the fan, it ain't "free" no more.


I have seen electric fans work OK on AX cars where you usually run for less than two minutes.
I would be very nervous using an electric fan for a 24 hour run.

Plus, the ducting and sheetmetal on a T4 is also used to separate the hot air under the car from the cooler intake air.
Removing the tin will rob you of HP since you're sucking in hotter intake air.

(IMG:style_emoticons/default/shades.gif)

[ThePaintedMan]

Elec is free (no night racing) right and no HP drain.

There's this pesky little thing called "Physics" that disagrees with your statement above.

Unless you have an extra battery that can power the fan for 24 hours without an alternator to recharge it.
As soon as an alternator is used to generate the electricity to run the fan, it ain't "free" no more.


I have seen electric fans work OK on AX cars where you usually run for less than two minutes.
I would be very nervous using an electric fan for a 24 hour run.

Plus, the ducting and sheetmetal on a T4 is also used to separate the hot air under the car from the cooler intake air.
Removing the tin will rob you of HP since you're sucking in hotter intake air.

(IMG:style_emoticons/default/shades.gif)

(IMG:style_emoticons/default/agree.gif) I'm no Andy, and I don't have the experience that most of these guys do but we're planning on entering Chumpcar this season too. I think if you remove all of the cooling that VW/Porsche worked so tirelessly to design, you might as well (IMG:style_emoticons/default/boom.gif) your car and don't even bother trailering it to the track. Worry less about going fast and more about safety, then reliability. Besides, I've already done a Chumpcar race in a well-prepared, FAST Mustang and even a stripped down 914 isn't going to have a chance in the world. I would suggest you do as we do - build the car for reliability and have fun, get some experience then come back with a different engine (Suby, V8, whatever) once you are comfortable with how the race and car works.

[teamgravy]

So we race off road as well with a Type I motor but have some friends in another class that race with a Type IV motor. I thought the Fat kit converts over to what is basically a 911 style fan and Alt. So if we built something like this with a electric fan being fed from air ducts cut through the roof. Oh and also an external oil cooler.
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In our Off/Road racing we are running 6-9 hours at a time like the typical Lemons racing (only one race a year is 24hrs and we prob won't enter that one).

I guess I am better off with where it is and blocking off all the heater stuff and use the fan over the heads/jugs.

Do we need all the other engine tins/metal work tho? Can I cut the end of the main top tins (over the pistons and heads) so that we can check/adjust valves without removing the engine.

And I hear ya ThePaintedMan, I am already thinking of a Type 1, subi, or some other conversion.

[McMark]

I agree. The benefits you're looking for don't exist and you're adding more risk of unreliability in exchange for dubious benefits. Bad tradeoff in a racecar.

But it sounds like you've decided to go this direction and you just wanted us to pat you on the back. (IMG:style_emoticons/default/sad.gif)

Give it a go and report back. We learn from success as much as failure. And I mean that in an honestly respectful way. Try it out, and let us know what you find so we can all learn. (IMG:style_emoticons/default/beerchug.gif)

[ChrisFoley]

If you go without a fan based cooling system you'll need two 6" ducts from the front of the car to the engine compartment. I don't think there's another way to supply enough pressurized air to the heads/cylinders for road racing, or you'll cook the engine.
Electric fans would probably be sufficient for cooling around the paddock.

[ArtechnikA]

...The fans are cheap $70 for 2100 CFM fan and I can also use some big ducting to cool motor at speed.

...Will ALT function from smaller pulley?

The Little Spec Book rates the stock coaxial fan at 800 liters/sec at 4600 rpm which is 1695 cubic_feet_per_minute - so you're in the ballpark on airflow.

But - how many amps does it take to make 2100 cfm, and Watts (pardon the pun...) that in HP ?

Keeping in mind that there are coupling loses in the alternator drive the coaxial fan doesn't have. The alternator will run with any size pulley, and it's a common racer's trick to run them with small(er) pulleys on high-revving engines. But it's gotta rev fast enough to make the power you need (plus stuff like ignition, fuel pump, cool suits? Helmet blowers? ...).

You may be able to pick up some airflow efficiency with an external oil cooler, at some cost in drag. And weight, due to the hoses and fittings, although the tradeoff is you can move the weight to where it helps you. And the downside is more risk of damage due to contact or debris.

The upside of the coaxial fan is it only draws power (roughly) proportional to your need for cooling.

[ChrisFoley]

The Little Spec Book rates the stock coaxial fan at 800 liters/sec at 4600 rpm which is 1695 cubic_feet_per_minute - so you're in the ballpark on airflow.

That would be good if CFM was the important measure of a fan's ability to push air through the cooling fins of the engine.
Electric fans designed for moving air volume typically don't produce much head pressure, and stall easily when backpressure increases.

[ArtechnikA]

Electric fans designed for moving air volume typically don't produce much head pressure, and stall easily when backpressure increases.

Yup - I agree.
However, I believe the engine-mounted coaxial fan also stalls at high revs - not coincidentally when backpressure reaches 'some point.'

It'd take a dyno setup or more CFD than I have access to in order to measure or model what 'some point' is. But I believe this is one of the several reasons 'some number' of vanes are removed from the fan for high-rev operation. And I'd expect you'd consider that number more than a little proprietary, so I won't ask ;-)

But I do know that 935's completely removed all the upper cylinder fins and improved cooling as a result...

[teamgravy]

I agree. The benefits you're looking for don't exist and you're adding more risk of unreliability in exchange for dubious benefits. Bad tradeoff in a racecar.

But it sounds like you've decided to go this direction and you just wanted us to pat you on the back. :(

Give it a go and report back. We learn from success as much as failure. And I mean that in an honestly respectful way. Try it out, and let us know what you find so we can all learn. :beer2:

Guess the admin role and 16K in posts means you have seen it all and type people pretty quick. I was actually asking since I have the motor torn down and deciding if going a different route is worth it. The benefits I see (still haven't been convinced they aren't there) are worth exploring so exploring.

1. Room to work on the motor in the car. From experience I assume we will be dealing with oil pumps failing, valve adjustment, Ign/electrical issues so room around the motor without removing it would be huge.

2. If the belt to run Alt takes 5HP to run from the motor and a fan (5LB of spinning mass + air resistance) takes another 3HP, wouldn't getting that 3HP back since I have to run ALT to keep batt charged for coil regardless of the elec fan or not.

3. Stock air shroud is 40-50lbs with all that heater hardware maybe more. Putting the air box back on may be only adding 30lbs back so maybe I close up the heater ports and use it with stock fan

#1 is probably most important to us in the long run.

...The fans are cheap $70 for 2100 CFM fan and I can also use some big ducting to cool motor at speed.

...Will ALT function from smaller pulley?

The Little Spec Book rates the stock coaxial fan at 800 liters/sec at 4600 rpm which is 1695 cubic_feet_per_minute - so you're in the ballpark on airflow.

But - how many amps does it take to make 2100 cfm, and Watts (pardon the pun...) that in HP ?

Keeping in mind that there are coupling loses in the alternator drive the coaxial fan doesn't have. The alternator will run with any size pulley, and it's a common racer's trick to run them with small(er) pulleys on high-revving engines. But it's gotta rev fast enough to make the power you need (plus stuff like ignition, fuel pump, cool suits? Helmet blowers? ...).

You may be able to pick up some airflow efficiency with an external oil cooler, at some cost in drag. And weight, due to the hoses and fittings, although the tradeoff is you can move the weight to where it helps you. And the downside is more risk of damage due to contact or debris.

The upside of the coaxial fan is it only draws power (roughly) proportional to your need for cooling.

Fan is 8-9 amps so should be plenty left over to charge batt and power coil. I was thinking of external oil cooler in back window or below mesh above motor. May plumb it further if we can get more air to it.

Adding to the e-fan we would put ducting into the motor for additional airflow at speed tho not sure how to run this with the fan, into same fan opening?

[euro911]

Removing the cylinder head tins won't gain you any additional accessibility for valve adjustments, however, removing the tin around the exhaust pipes, as you have already have done, will.

I don't think you'll have a problem with the oil pump, but if keeping the stock fan housing arrangement, an oil pump replacement would typically require an engine drop.

Try this experiment: With the engine you already have out, reinstall the fan housing and remove the front engine crossbar/mount to see if you have enough clearance to remove the pump.

If that works, when the engine is in the car (and if the pump needs replaced), jack the engine up, remove the rear shift rod and engine crossbar and perform the change-out (IMG:style_emoticons/default/confused24.gif)

[McMark]

Do it. Prove us wrong. I love to learn.

And there really is no sarcasm there. I'll never build an electric fan cooled Type 4, so people like you are the ones who will teach me something.

[ThePaintedMan]

I agree. The benefits you're looking for don't exist and you're adding more risk of unreliability in exchange for dubious benefits. Bad tradeoff in a racecar.

But it sounds like you've decided to go this direction and you just wanted us to pat you on the back. (IMG:style_emoticons/default/sad.gif)

Give it a go and report back. We learn from success as much as failure. And I mean that in an honestly respectful way. Try it out, and let us know what you find so we can all learn. (IMG:style_emoticons/default/beerchug.gif)

Guess the admin role and 16K in posts means you have seen it all and type people pretty quick. I was actually asking since I have the motor torn down and deciding if going a different route is worth it. The benefits I see (still haven't been convinced they aren't there) are worth exploring so exploring.

1. Room to work on the motor in the car. From experience I assume we will be dealing with oil pumps failing, valve adjustment, Ign/electrical issues so room around the motor without removing it would be huge.

2. If the belt to run Alt takes 5HP to run from the motor and a fan (5LB of spinning mass + air resistance) takes another 3HP, wouldn't getting that 3HP back since I have to run ALT to keep batt charged for coil regardless of the elec fan or not.

3. Stock air shroud is 40-50lbs with all that heater hardware maybe more. Putting the air box back on may be only adding 30lbs back so maybe I close up the heater ports and use it with stock fan

#1 is probably most important to us in the long run.

...The fans are cheap $70 for 2100 CFM fan and I can also use some big ducting to cool motor at speed.

...Will ALT function from smaller pulley?

The Little Spec Book rates the stock coaxial fan at 800 liters/sec at 4600 rpm which is 1695 cubic_feet_per_minute - so you're in the ballpark on airflow.

But - how many amps does it take to make 2100 cfm, and Watts (pardon the pun...) that in HP ?

Keeping in mind that there are coupling loses in the alternator drive the coaxial fan doesn't have. The alternator will run with any size pulley, and it's a common racer's trick to run them with small(er) pulleys on high-revving engines. But it's gotta rev fast enough to make the power you need (plus stuff like ignition, fuel pump, cool suits? Helmet blowers? ...).

You may be able to pick up some airflow efficiency with an external oil cooler, at some cost in drag. And weight, due to the hoses and fittings, although the tradeoff is you can move the weight to where it helps you. And the downside is more risk of damage due to contact or debris.

The upside of the coaxial fan is it only draws power (roughly) proportional to your need for cooling.

Fan is 8-9 amps so should be plenty left over to charge batt and power coil. I was thinking of external oil cooler in back window or below mesh above motor. May plumb it further if we can get more air to it.

Adding to the e-fan we would put ducting into the motor for additional airflow at speed tho not sure how to run this with the fan, into same fan opening?

Its not that anyone wants to see you fail, trust me. Its just that these engines have now been around for 40+ years and everyone from Porsche and Volkswagen engineers to weekend racers have explored most other options, and usually with a larger budget than those of us trying to make it through a Chumpcar/Le Mons race. Racer Chris is a great example of someone who has already learned it all the hard way but has developed reliable, high quality alternatives for the rest of us. If he hasn't come up with an electric setup, I don't know who would have.

Personally, again, as another Chumpcar hopeful, I think that keeping it simple is the way to go. I've seen multiple aircooled cars run these races with good success using the stock cooling setups (plus maybe an external oil cooler). Two Beetles ran Sebring last year, and one of them ran the whole race on the same engine. I don't know what the rules say for Le Mons, but in Chumpcar, if you're betting on getting the car in without any penalties as a bone-stock car, they will allow all 914s. Again, assuming its bone stock. Adding an electric fan will mean that your car then has to go through the Average Internet Value (AIV) process and the burden will be upon you to prove that there are 10, running 914s across the country that are worth $500 or less. At that point, any additional engineering you do to the car will be assessed based on its value. Thats why we've decided to run the car as close to stock as possible and just have fun.

But as McMark said, no one has made it work yet, so you guys might be the first. Give it a shot!

[brant]

Jake, Chris, AJRS, and others did a lot of work on overhead fan and electric fan cooling.

it is much more complicated that just dumping the air onto the motor

you have to try and keep the temperature consistent across all 4 of the cylinders and heads. So the duct work under your electric/overhead fan is the truly important part

this was tested on the dyno extensively
I have seen electric cooled 914's
they work for short sprint races

the AJRS ones were total loss systems and running no alternator, or a transmission driven alternator.

the oil pump won't fail
and you probably won't be touching the valves hot

the front shroud is magnesium... all of the duct work together is probably closer to 20lbs total.

I run a 914 race car without the chassis side shelves
but its a sprint car

brant

[ChrisFoley]

However, I believe the engine-mounted coaxial fan also stalls at high revs - not coincidentally when backpressure reaches 'some point.'

I've run tests on 4 different cooling systems.
Head pressure increased somewhat linearly with RPM.
Even at 5000 rpm there was no evidence of cavitation on any of the systems.
I'm sure an electric fan that draws less than 10 amps is incapable of producing even half the head pressure of the 4 most popular mechanical blower systems - Stock, 911 style (FAT), Type 1 (DTM), Horizontal (Tangerine).

The level of air pressure required to cool the engine is roughly equivalent to air speeds of 60-90 mph.
You would need efficient ducting with the same crossection as the top of the heads & cylinders to rely on vehicle velocity to provide the necessary pressure for cooling.

[Randal]

Chris Hamilton's Dad (and company) have been running a fan cooled 914 for years, but it only runs autox's.

Maybe Chris will jump on this posting and tell us his experience. (IMG:style_emoticons/default/biggrin.gif)

[ChrisFoley]

I run a 914 race car without the chassis side shelves
but its a sprint car

Removing the side tin and engine shelves won't adversely affect engine temp through a long race - as long as the car is in motion most of the time.
However,this won't make topside access much better for parts swapping or valve adjustments. Its still easier to work from below on most engine maintenance.
It does improve visibility however.

[brant]

I agree.

the shelf only seperates the rising heat from the headers when the car is sitting still.

probably its biggest effect is that the fan now has access to a tiny bit warmer under motor air, and road dust with the front chassis shelf removed.

[teamgravy]

However, I believe the engine-mounted coaxial fan also stalls at high revs - not coincidentally when backpressure reaches 'some point.'

I've run tests on 4 different cooling systems.
Head pressure increased somewhat linearly with RPM.
Even at 5000 rpm there was no evidence of cavitation on any of the systems.
I'm sure an electric fan that draws less than 10 amps is incapable of producing even half the head pressure of the 4 most popular mechanical blower systems - Stock, 911 style (FAT), Type 1 (DTM), Horizontal (Tangerine).

The level of air pressure required to cool the engine is roughly equivalent to air speeds of 60-90 mph.
You would need efficient ducting with the same crossection as the top of the heads & cylinders to rely on vehicle velocity to provide the necessary pressure for cooling.

This is getting way more complicated that I expected and I trust you guys know what your talking about. I realize the oil/engine cooling is all we have going for these motors so not ready to risk it since we won't have ability to truly test before the race. Just thought the T1 in our O/R racecar is simple and thought I could replicate that with the T4 motor.

So forgetting the e-fan option, what I am hearing it's not advisable to alter any of the engine tins to add additional cooling as that will effect pressure across the cyl/heads?

I run a 914 race car without the chassis side shelves
but its a sprint car

Removing the side tin and engine shelves won't adversely affect engine temp through a long race - as long as the car is in motion most of the time.
However,this won't make topside access much better for parts swapping or valve adjustments. Its still easier to work from below on most engine maintenance.
It does improve visibility however.

I hope to remove some of the shelves and tins. I think I will still do this to keep us from having more work at the track if(when) we have issues and need to drop the motor.

Is this a decent solution for external oil cooler?
Sandwich Oil Cooler Adapter
We are already over budget (see my parts for sale in FS forum...) so I am looking for a cheap solution for external oil cooler.

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