I put in a Greddy SMIC, and it works well. I also made a nice duct for it. However, when under high boost, and not rolling fast, not much air through the IC.

So I got a small, aftermarket fan, and a pressure switch. Installed it today,

Here is a shot through the duct and I am happy I can see the ground, makes getting air through it easier, this is a two piece duct, not the final product, but a work in progress.


Here is the Ebay fan on the SMIC. With a little massaging it fits. Had to mod the duct a little bit, since I made mine from tin, it was easy.


So I installed everything, Here is a shot of the SMIC and duct work, with the fan installed.


Here is the pressure switch, barb adapter, and vibration bushing. The switch is for an air brake system where air pressure actuates the brake lights. I tested it and it closes at 3 PSI. The fan comes on at 3 PSI and pushes air through the SMIC even at low speed, at least that is how I hope it works out.


Here is a closer shot if you want to see the PNs


Made a bracket and mounted the switch, on the passenger side near teh fan relays.

Another Shot


A little blurry but here is where I am picking up my pressure signal.


Hope someone finds it helpful.

 

Any IAT recordings? does it help any? Been wondering about making something similar.

 

Interesting idea. I've always though a switch based on speed and a floor temperature would be best though.

 

I used to run a 10" e-fan on my large SMIC. I had it rigged up to work with my factory fog light switch since I ditched the fogs themselves. I noticed a difference in traffic-driving IATs but the fan was so damn loud. I also took it off once summer was over.

Cool idea though.

Also, what in god's name is in your brake fluid res? Sludge?

 

I'm wondering what the "lag" is on the fan. How long does it take to get to full speed?

 

i'd prefer a temp operated fan same as your cooling system, except obviously turned on by IAT.

 

Yea but wouldn't it be a waste to turn on the fan if your IATs are high and you are at high speed?

 

My thoughts are this is for low speed scenarios when no air is flowing thru intercooler. If your pressure switch trips at 4 lbs, then you are in boost and obviously moving unless you are on a dyno. I could imagine a speed switch or on with ignition would work better. Just my .02 good work getting creative.

 

with the pressure switch it will come on regardless. at least while moving you have the benefit of less heat soak and likely not tripping the fan when additional air isn't needed.

at any rate, the SMIC and even most V-mounts do not get as much air directed at them as the radiator does and i would bet a fan would be beneficial even at freeway speeds. i plan on setting up my FC v-mount twin charged setup with an IC fan that i can hopefully setup based off IAT levels. however i run water injection so it usually will be off.

 

I suppose a speed-based switch would work well...fan on under 15mph or something...

 

It would work better than a 3psi pressure switch.

Roughing out some numbers, 3psi of dynamic pressure develops when the incoming air approaches 410 miles per hour. So it would always be on.

Intake air temperature would be another interesting metric to base this on.

I have a couple of 12v electric fans that I picked up to try this type of thing. Haven't gotten round to it yet. I was selective to get a fan that could handle significant backpressure since the intercooler fins create a fair amount of resistance. For autocross it would be fabulous to cool the intake air after each run, saves using icebags on the manifold or spraying water into the intercooler. (One less thing to carry to the events)

David

 

^

"Roughing out some numbers, 3psi of dynamic pressure develops when the incoming air approaches 410 miles per hour. So it would always be on." dgeesaman

I believe the OP has the pressure switch connected into the y-pipe, not in the duct. Is that what you meant by dynamic pressure?



Also, IMO, This is kind-of useless because you want the SMIC cool before the boost is built. I agree that It should be based on IAT and not the actual boost pressure in the manifold. I think, like arghx alluded to, the fan has to take time to speed up when it is triggered. In addition to this, I would want to be able to run the fan longer than just when I am in boost, because of heatsoak.


John

 

you can always watch the IAT curve and set it to a point in the middle so that the fan has caught up by the time the IATs just begin to climb and hold it off a bit to cool it after the run.

 

Hang on while I smack my forehead, as the OP clearly stated that he was concerned with high boost at low speeds. A 3psi switch on the intake charge would address that quite cleanly.

In my experience, you would want the fan on more than that, as there are many other times when the intake charge is very hot and you want to maximize intake cooling. My autocross example is one case; traffic is another, etc. But changing the sensor approach is secondary to the primary task of developing a fan system that does the job when it's active.

 

to me it just seems like overkill on cool days when the IATs are not going to be that high.

 

I think a fan is more useful at stoplights and when you are not under boost to prevent heat soak from the radiator
if your car has boost, then the car is moving and when the car is at speed a fan is not going to help much
I understand you have a thick greddy SMIC
try setting the fan to come on when you have less than 3psi then go putz around and touch the intercooler in a parking lot and see if it helped

 

Does any one know how many lbs are these after market SMIC good up to prior to becoming inneficcient.

 

Summary thoughts:

1) There is enough airflow at speed that a fan on the IC is not needed. RX7's running in SCCA ITS class and up have *NO FANS* on the radiator - it's not necessary. And if they do it's only to keep the car cool in the pits and right before the start.

2) The IC acts like a heat sink. Even if the fans come on when air intake temp starts to rise the effect of the fan pulling more air through the IC will have a significant time delay (relatively speaking) - or at least a time delay that before it starts to have an effect oin the IAT you will be doing 150mph+ (given an FD can get there in a matter of seconds under full boost). So a boost activated switch is pointless.

3) The only time an IC fan is going to be of any benefit is when there is no or very little airflow through the IC (which is when all the heatsoak occurs). That being when the cars is stationary or being driven very slowly. Hence why a **speed related switch*** might work or simply wire it through a relay that connects to the neutral safety switch on the transmission. When you pull to a stop or with the car idling and the (manual) transmission in neutral the fan will come on. Simple.

4) oh and you could have an override "OFF" switch for times during colder winter months when it really isn't necessary.

FWIW,
Crispy

 

i think the air delay cooling effect is being overthought, we're talking 1-2 seconds for the fan to come to speed and IATs to start cooling. i do like the neutral switch idea though, similar to telling the car to get ready to be moving soon when in gear.

i think most people are having a hard time getting beyond the comparison of fluid filled cooling systems versus air to air cooled where the effects are much more instantaneous.

i do however not like to think of the contact wear that the relay is going to be subjected to during each shift. thinking of that as a light switch constantly being flicked on and off, causing the bulb to burn out dramatically faster, something is going to give, although probably not critical as say losing a wastegate pressure line.

 

Agree but I think the key is what you said..."to *start* cooling." It take a good 10-15 seconds of driving at highway speeds after sitting at rest with a heat soaked IC to see any appreciable drop in the IAT, or at least enough to make difference in power generation capability. The same would apply with an IC fan running at full blast.

Indeed but although it will be more instantaneous it will certainly not be instantaneous.

Ooo....very good point. Does the neutral safety switch engage every time the shifter travels through neutral or is it activated in conjunction with the depression of the clutch? Still a valid point though. Damn...thought I was on to something there.

Regards,
crispy

 

^ The contacts on the neutral saftey switch do close every time you depress the clutch, however, there is no current running through the contacts during normal driving, just when starting. That is why the contatcs do not wear out quickly (no spark).


John

 

1) Space the fan off the IC by at least 3/4" and fab a fan shroud to envelop all of the IC! This will substantially improve the fan's capacity, efficiency and reduce its noise.

2) Turn the IC fan on whenever the cooling fans are on. This will counteract the tendency for the cooling fans to push [hot] air back out through the IC when the vehicle is not moving. (V mount setups should always run the cooling fans and IC fans together to prevent recirculation.)

3) Operating the fan while moving will improve airflow through the IC regardless of speed. (Whether added cooling is needed or not is another matter.) Operating the fans with a pressure switch does give them a head start and will help reduce IC heatsoak and improve capacity.

4) I've played with an IC mounted thermal switch (in lieu of IAT)--my results being inconclusive--but it might be useful on your SMIC application.

 

Wow, didn’t expect this much of a response, so sorry to get back to this so late, and I will try to answer some questions. And comment as well.

OyvindRX7, Sorry No temp readings, I have driven it around and made sure it came on, but I haven’t been out driving much.

Supernaut, You may be right, However I was looking for something easy to implement and simple in execution. Not sure how I would base it on speed and even so , I was just looking to increase airflow at low speed while under boost, and it couldn’t hurt at speed either.

It might be unnecessary to run the fan when IAT is low and you are at speed, however, under boost I don’t think there would be too much air flow through the SMIC to make it too cool, but I don’t have any numbers to back it up.

Theorie, This fan isn’t very loud but it does push a substantial amount of air. Speed switch might work, But I want it on under boost as well. I guess if I used both I could get the fan to come on before boost unless I was launching hard.

Arghx, in bench testing it is nearly immediately up to speed, after installation I can’t see it so I can’t measure it, however it sounds the same, I don’t know about when driving but I don’t know why it would be different.

Karack, Interesting and while I thought of that and it would likely be a better solution, likely more stable, I fall back to looking for something easy to implement and simple in execution it would probably be better using IAT more stable maybe.
I didn’t think of the heat soak issue, I will think about it and see if I can find a way to easily trigger off the IAT, along with PSI.
It may be over kill and I may need to change it but this is just the start.

Goalguy, Your thoughts are correct, However the fan comes on at 3 PSI and under load 3 PSI happens pretty quick, and the SMIC doesn’t get a lot of air movement at low speed, say accelerating out of a corner.

Dgeesaman, I always enjoy your comments. even this one. I do like the auto cross comment.
I do think there are times other than what I described, that the fan could help, however I’m not trying to eat the whole elephant at once, starting with more air at low boost. I’ll work on the rest once I am sure the fan will hold up and it works.

RenesisFD, That is an interesting point, and cooling before building boost, would be good, however I have to believe that the fan on at boost is not useless as it will push more air through the SMIC, especially at low speed, as was the goal. As to heat sink I have been thinking a timer might be a good thing, such as run for a minute after boost drops.

CrispyRX7, Thanks for the "Summary thoughts": input. Interesting, however, I am not tracking the car so I don't feel it all applies. Still working on keeping it simple. And I am sure that more air over the SMIC at any time, is better than less. I may work on a more efficient system after I prove the fan and location are good.

There were lots of comments and suggestions that I will be thinking about while I continue to play.

Thanks

 

I like the idea of activating the SMIC fan when the cooling fans come on, seems like a valid way to help reduce heat soak (something I didn't consider) so I need to do a little research, I know dgeesaman did a fan write up so I plan to start there. Once that is working, I may consider adding an activation by the IAT sender. My IAT is still in the stock location, and from reading this is not the most accurate.

I will, however, try to get some IAT data. I will disconnect the SMIC fan and see if I can get some data from my DataLogIt. I know that the info will be skewed a little based on the fan being in the way, but I don't think it will be that big of a deal, and I will do it on the same day after warming up. Just some zero to about 50, and if I can find a good spot some hard cornering, because the idea is low speed high boost. By the way my boost is provided by the twins sequentially at 12 PSI.

It might take a little while, I don't drive it everyday and I don't live in a area conducive to testing. :-) I go out a little way to test.

I'll post the data when I get it done.
If there are suggestions on the best way to get the SMIC fan to activate with the cooling fans, please post them.

Thanks again for the comments and suggestion.

 

Where credit is due: I have offered little to explain the cooling system. On the other hand, DaleClark, Scotty305, and Arghx7 have very good threads worth looking into.