Adding a electric fan that stays on for 15-30 min too cool the engine bay

[Infinitiguy19]

I remember at least one topic on this where Qship96 posted saying that the 280ZX has a fan that stays on after the car has been shut off to cool the engine bay. I also remember mike (Goody94Q45) saying that it would beneficial to say the least, But I can't find that topic.

So I was wondering has anyone with a G50 Q45 ever attempted this?

If not what would be required to do such a feat?

Where could we mount the fan in this cramped engine bay?

Or would the existing Aux electric fan used in overheats and for the A/C be sufficient enough and could it be wired to do so?

[MinisterofDOOM]

I wonder how effective that would really be...

Not trying to shoot down the idea, just thinking outloud. The car's not moving, fans can only be located at the radiator...not really anywhere for the heat to go. Fans work at a stop when the car is running thanks to the fluid coolant system with radiator. Coolant is not flowing with the car off, so the fan would basically have the job of cooling off a giant block of aluminum. If you had a way to draw air OUT OF (rather than just into) the engine bay, you might see some kind of useful benefit. But just turning on a fan after shutting down the car doesn't seem like it would be effective. Might have been kind of effective in the Z with its much more open engine bay, but even then the same issues apply.

[maxnix]

Put fan on top of hood to draw air out when stopped. When not stopped, could be a problem.
Modified by maxnix at 5:06 PM 8/18/2009

[chicos240]

You could just use a turbo timer. It will keep your engine running and the fans going for 5-10 minutes while everything cools down. In turbo world we use it so the oil doesn't SIT super hot in the turbo. If the TURBO is super HOT and the oils SITS because the engine has stopped it becomes cooked in there and can seize your turbo.

[Q45tech]

Why not just create a time delay relay so when you push a bitton [in summer] the condenser fan comes on for an adjustable 3-5-10 minutes?

On low speed it probably only consumes 15 amps? Make sure battery is good and check frequently.

A pop up vent in hood would be interesting.

[Infinitiguy19]

Put fan on top of hood to draw air wout when stopped. When not stopped, could be a problem.

You mean cut a hole in the hood?

You could just use a turbo timer. It will keep your engine running and the fans going for 5-10 minutes while everything cools down. In turbo world we use it so the oil doesn't SIT super hot in the turbo. If the TURBO is super HOT and the oils SITS because the engine has stopped it becomes cooked in there and can seize your turbo.

I have thought of that, but I can do that my self. I am just extra paranoid with my car, I lock the doors when going inside the gas station.

I wonder how effective that would really be...

Not trying to shoot down the idea, just thinking out loud. The car's not moving, fans can only be located at the radiator...not really anywhere for the heat to go. Fans work at a stop when the car is running thanks to the fluid coolant system with radiator. Coolant is not flowing with the car off, so the fan would basically have the job of cooling off a giant block of aluminum. If you had a way to draw air OUT OF (rather than just into) the engine bay, you might see some kind of useful benefit. But just turning on a fan after shutting down the car doesn't seem like it would be effective. Might have been kind of effective in the Z with its much more open engine bay, but even then the same issues apply.

I thanks you for posting, I haven't considered that my self but I am looking for the technical answers.

Why not just create a time delay relay so when you push a button [in summer] the condenser fan comes on for an adjustable 3-5-10 minutes?

On low speed it probably only consumes 15 amps? Make sure battery is good and check frequently.

A pop up vent in hood would be interesting.

See that's what I was wondering. I am just concerned about airflow and if the air blowing through the condenser fan can actually make it to the plenum and the hoses and harness' under it.

A pop up vent would have been cool when I owned the 1991 Q45 (When I was less enlightened) And when I actually liked this: http://picasaweb.google.com/lh...tlink.

[goody90q45]

.....I also remember mike (Goody94Q45) saying that it would beneficial to say the least, But I can't find that topic.......

I've noticed that the 94-96 under-plenum hoses are a lot more supple than the 90-93 hoses. More brittle and broken connectors on the 90-93 too. The 94-96 grill let's a lot more air to the upper engine area than the badged and grillless 90-93.

I think there would be enough room with the center shroud removed to mount a 2 1/2" to 3" electric fan between FI 1 and 2 near the front of the plenum. The problem with this is it blows more hot air from the top of the engine under the plenum. You need cooler air while driving more than about 10-15 minutes and a hood scoop is probably the best solution. Few of us will jump on that option.

I think Tech has said there's little to no vacuum pressure even under full load below the air filter so how about teeing in to the lower airbox with a 3" duct run under the airtube to the plenum....Driven by a 3" electric fan with a thermocouple mounted in the upper engine compartment.

All this seems like a lot of work. I'll pull the plenum every 10 years and replace hoses.

[SleepinTXQ45]

i was just thinking... would if u take the fan we have & make it suck instead of blow......lol u guys r thinking of taking a fan & bring more hot air into the engine area via the hot radiator & condenser area....but really take the inside air & remove it out.... somewhat though the front. this will also draw cooler air up & out to the front grill. im not saying this is the best &or great idea,just something different from the blowing in

[Q45tech]

Why would you imagine that a grill makes any difference in air flow into engine compartment?I suggest a few course in thermodynamics.

[Q451990]

I vaguely remember a post from a long time ago... maybe even on the yahoo board, about sending a ground pulse to a pin on the ECU that would keep the AUX fan on for a period of time after the car was turned off. It only worked for that one time, so you would have to have some way of grounding that pin each time you turned the car off...

Like I said, it was a long time ago... maybe this will jog someone's memory...

If you didn't want to use the auxilary fan, you might be able to rig something up in the active cooler space in front of the left wheel well.

Heath

[Infinitiguy19]

I vaguely remember a post from a long time ago... maybe even on the yahoo board, about sending a ground pulse to a pin on the ECU that would keep the AUX fan on for a period of time after the car was turned off. It only worked for that one time, so you would have to have some way of grounding that pin each time you turned the car off...

Like I said, it was a long time ago... maybe this will jog someone's memory...

After looking at the FSM and going by what you say about the ECU. I have concluded that it is 2X times as hard to do this on a 1994-1996 Q45 rather than on a 1990-1993 Q45.

Does the ECU still get power even if its off?

It would make sense that it does other wise it would forget the "Self Learn" stuff.

If you didn't want to use the auxilary fan, you might be able to rig something up in the active cooler space in front of the left wheel well.

Heath

Weird I thought about the same thing as I was taking a wizz. I want to see where exactly the active fan is and if any air could possibly get in there.

Maybe I will put the fan backwards so its sucks the air out. But then again put it so it pushes the air into the engine bay would push the hot air out right?

Maybe have the active fan and condensor fan working together for 15 min.

[elwesso]

if you really are concerned about it you should just open the hood... Making timers and stuff that run off the battery while the car is off makes me nervous, I dont like dead batteries...

Would be kinda nifty to rig something up that would prop the hood up a little from the back (closer to the windshield) to let hot air out...

Even on a 94, all you have to do to get the fan to come on is jump the fan relay.. I believe it is hot all the time (meaning IGN doesnt have to be on)...

The ECU relay powers off after about 5 seconds of the IGN being turned to off. Any "learn" features are in the internal memory, which I dont think theres any such thing. only thing that are stored in the internal memory is DTC's...

I've noticed that the 94-96 under-plenum hoses are a lot more supple than the 90-93 hoses. More brittle and broken connectors on the 90-93 too. The 94-96 grill let's a lot more air to the upper engine area than the badged and grillless 90-93.

I agree totally... on the one 94 Ive done a plenum on only the hoses I cut really needed to be replaced.

[maxnix]

if you really are concerned about it you should just open the hood...

I agree totally... on the one 94 Ive done a plenum on only the hoses I cut really needed to be replaced.

Yes, open the hood when in the garage, and the heat "magically" rises and leaves the engine bay!

One cannot tell from the exterior is a hose needs replacement or not, especially cooant hoses. The latter especially can be pliable and look fine on the exterior and be totally rotten where they attach on the interior. Just a fact of life that one needs to inspect the interior of all hoses when under the plenum.

[SleepinTXQ45]

Why would you imagine that a grill makes any difference in air flow into engine compartment?I suggest a few course in thermodynamics.

well give me a lesson then. were u understanding what i said.... im sure u did that would just be silly. so what was it i missing then. grill or not its right there thats all. so im all about learning things so teach me something.there really must not be a reason for grills or airdams then...good to know...... thermo what??

[Skibane]

Several years ago, I had a home-brew radiator fan thermostat installed on my small pickup which had the ability to run for an adjustable amount of time after the engine was shut off. I had it set to run on for around 10 minutes, IIRC.

On several occasions, I noticed that the battery was nearly dead - apparently due to a combination of short trips and hot weather. The fan usually ran for the full 10 minutes after even a very short drive, and the alternator didn't have time to replenish the amount of charge being drained by the fan. Shortening the run-on time (or installing it in a vehicle with a less-wimpy alternator) probably would have cured the problem.

One other consideration is that after the fan has run for 10-15 minutes beyond engine shutoff, the coolant inside the radiator will be much cooler than the engine - which means that the engine will get a slug of cold coolant if you restart it. This is a thermal shock to the engine. Generally, sudden changes in temperature are undesirable.

[Q45tech]

We will be happy to point you to appropriate colleges that teach mechanical engineering and the math that is a prerequisite;

Here is a good place to start to refresh:http://hyperphysics.phy-astr.g....html

[qship96]

Engines get a slug of ICE COLD coolant {sometimes below 0 degrees in the north} every day when one starts their car on a winter morning and the block heats up enough to open the thermostat and allow the still ice cold coolant from the radiator to flow into the now hot block!!!!!!

[Skibane]

Engines get a slug of ICE COLD coolant {sometimes below 0 degrees in the north} every day when one starts their car on a winter morning and the block heats up enough to open the thermostat and allow the still ice cold coolant from the radiator to flow into the now hot block!!!!!!

That's a good point. The thermostat opens gradually (so it's not like all of the cold coolant flows into the engine at once) - but still, there has to be a pretty major temperature swing in freezing weather.