Brentis

Can someone share their opinions/anecdotes about using a fan with an intercooler? Other cars have frequently endorsed using a fan on a stock intercooler to improve performance. MR2 for example says they drop the charge 20 degrees with use of a 9" SPAL fan.

Using 2 Mechatronics F1238 120mm fans placed next to each other as in the bottom of this link http://www.scuderiaciriani.com/rx7/intercoolers.html, should improve heat spikes and detonation on a lightly modded vehicle to some extent. From my perspective the most likely time you will detonate is when you are accelarating from a start, where your car has been heating up and you are placing the most stress on the engine.

Using these fans, I calculate that I can get the equivalent of a 10mph air charge through the intercooler. I calculate that I can get 256cfm pulled through the intercooler. This assumes that the ducting of the SMIC is 100% efficient (i.e. 10mph yields 10mph worth of intake charge to the intercooler). This is not likely and the fans may even provide greater than a 10mph equivalent. Furthermore, the air from the ducting is not forced to enter into the intercooler and may further decrease cooling effectiveness.

So needless to say I bought a couple of these fans for $7.99 each to give it a try. I know this isn't going to obviate the need for a better IC, but this approach is letting me be more comfortable getting a PFC rather than an IC first.

My mods include:

CB, DP, Modified stock intake w/ K&N, and radiator shield.

Thanks for your thoughts!

Kento

MR2 for example says they drop the charge 20 degrees with use of a 9" SPAL fan.

I've got a SPAL fan on my Greddy SMIC, and while I'm sure it helps with heat soak when you're stuck muddling around in traffic, it doesn't do a whole lot after a while; but I think in those situations, it's better than nothing. I've popped my hood after 30 minutes of driving in 80 degree city traffic with the SPAL fan running the whole time, and the IC was still pretty damn hot on the output side (the top heading toward the IM throttle body). I put my hand behind the IC to see how much heat it was putting off, and it was quite a bit, but it didn't feel like there was a whole lot of CFM being pushed through. I'm wondering if there are more powerful fans out there of the same size.

ZeroBanger

well the link doesn't work. But heres my story. I have a blitz smic, and when I had one radiator fan (waiting to get the other repaired) I got major heatsoak, so I hooked up 2 5 inch fans to my intercooler. These fans were DC powered heavy duty computer fans, I think they were only like 110 CFM each or something like that.

Its hard for me to tell if they were good or not, I can say my best time I ever ran at the track was when I had used the fan while I was moving up in the lanes.

I don't think it can hurt.

rynberg

you can read about Max's experience with his M2 medium SMIC here:

http://www.maxcooper.com/rx7/how-to/ic_fan/index.html

Brentis

Think the comma got in the way of the link.

Here it is again

http://www.scuderiaciriani.com/rx7/intercoolers.html

about 80% down see the post by Spencer


I read the Max Cooper story, but doesn't say much in terms of butt dyno, or intake temps, etc.

spurvo

I placed a thermosensor into the fins of my stock IC. It's pretty cold these days, but I've found some things out:

1) The IC prety much holds whatever temp it was at last until the car is moving.

2) even 10 mph is enough to cool it down quickly (but notice it's cold outside, so in warmer weather this may not hold true.

3) Just sitting and ideling raises the IC temp to about 17 C (63F)

4) turning on the fan causes the IC temp to rise immediately and drammatically, typically to 32 C (90F) on a 40F ambient temp day.

5) popping the hood but not opening it fully doesn't change this heat rise, nor does opening it fully.

6) Running the fans after engine shutoff with the hood closed keeps the IC nice and warm (the temp just sits at 32 C) Popping the hood results in the IC cooling down with the radiator fans on, from 32 to 25C. Opening the hood fully makes this happen faster.

So it would seem that running the radiator fans while not moving (traffic or waiting in line to go fast in a straight line for 1/4 of a mile and abuse the whole machine terribly.. oops!) will heat the IC, and running an IC fan WHILE running the rad fans will not help this much. Turning off the rad fans and running an IC fan at 10 mph virtual should help. For traffic, this is probably the best you can do. For racing, pop the hood (but don't open it all the way) while creeping forward with the fans on. Close it before you pull into the trap, turn off the rad fan as you stage, turn on the IC fan to cool it off, tune off the IC fan before you go.

That's all I know so far...

Brentis

but - I think the heating caused by the radiator is indirect vs. using an IC fan that pulls air from the outside duct. Also I think the backside of the IC may be getting heatsoaked from what you describe. With the IC fans, they will be on the back blowing any of the warm air that would've soaked the IC away from it...

make sense?

spurvo

Yes, as long as the ducting for the IC that sits right on top of the rad isn't being heated? But this is plastic, so probably doesn't heat it too much. Obviously, an intake temp gauge is the only real arbiter here, huh?

rallimike

iTrader: (1)

I have a 10" fan on my PFS smic, which I switch manually. There is no question it keeps the IC cool. The problem is, the UIM heatsoaks. The last time I was at the drag races, my Commander showed intake temps in the 50s after a run. I was surprised it was not coming down with the fan on, so I felt the outlet pipe, and it was cool. The UIM was VERY hot, so I sprayed it with water, and the temps came down immediately. The more I sprayed, the lower the temps got.
As a seperate thought, I have searched the boards to see if anyone had ever posted on the heatsoaked UIM subject, and found nothing.

Brentis

ok - UIM / LIM - what are they?

Brentis

Assuming UIM means upper intake manifold. That is interesting. The little bit of good news is that the UIM is optimized for flow vs. cooling thus hopefully won't have as adverse affect to being heatsoaked..

TeamChin

iTrader: (1)

what if you re-routed the AC to a small coiling coil..that is placed between the fan and the intercooler??? this would blow cold air right into the intercooler....and all you would loose is a little cabin comfort....

Kento

This is related to my previous post about bypassing the coolant feed tubes to the throttle body. The throttle body gets fed coolant (a misnomer in this case, as it heats up the TB excessively; its only function is to keep the TB from freezing over in extreme cold conditions), and since that turns it into a heat exchanger, it transfers some of that heat to the UIM (which I was calling the intake plenum in my post). It will be interesting to see if bypassing the coolant flow tubes-- a fairly easy procedure once you remove the TB, supposedly-- will have a positive effect on UIM heat soak. I imagine it will.

rallimike

iTrader: (1)

Sounds like a good use for a thermostat of some kind. I'm not sure the UIM isn't just heat soaking. I finally ordered a pyrometer; when I get it, I intend to do some experimenting, and I'll post my findings

Brentis

hard to EVER imagine the TB freezing ????? I read somewhere that its purpose was for something else - not that I recall. Maybe for rough idle at startup??

spurvo

TB coolant line to heat up TB on cold start to reduce ubburned hydrocarbons in that heated intake air = heated engine = more complete combustion & hotter pre-cats = less start up emissions. The coolant line heating up the TB will also melt the thermo-wax in the double throttle actuator at 177F, allowing boost to be applied to the engine through the secondaries. Once warm, though, the TB coolant line heats up the TB to the same temp the engine temp is at. Heat soak in the UIM maaayyyy be related to high exhaust temp heating the lower intake manifold (LIM) which in turn heats the UIM. At 450C, the exhaust is going to increase these components much more than the coolant, which shouldn't be much over 98C 208F. I'm not saying the coolant (heatant?) temps don't contribute, just think the exhaust probably contributes more...

But what the hell do I know?

Brentis

It's unfortunate we don't have a thermal engineer here, or an automotive thermal engineer, or better yet an rx7 engine engineer..

maxcooper

A whisp of hot exhaust in the LIM isn't going to heat the UIM nearly as much as a constant flow of hot water. Even if the water is much cooler than the exhaust, it carries far more heat in there because of its mass. That's my guess, anyway.

I never cared before, but I think I will bypass my TB coolant line one of these days. It does seem to get darn hot, and I had been thinking of having it coated or placing a heat sheild underneath the UIM for a while. The TB coolant line bypass would likely be much easier as a first step, and just as effective.

-Max

radkins

If you going to spend your time mounting and wiring up IC fans, do youself a favor and dont use a $8 fan. I used the same type fan Max uses, a Perma Cool High Performance. It's about a $75 fan but it REALLY pulls air through the IC. Its also much higher speed than most fans. When I an sitting at a stoplight and I cut it on you can hear it whiring over the sound of the engine. Once you install one of these and see how much air it pulls through you will imediately feel justified for going through the truble of doing it. But a computer fan just wont cut it.

dclin

iTrader: (4)

Max - how do you have the IC fan switched on?

I was thinking of having a relay tripped by the radiator fan, with the relay wired to a second 'trip' by a manual switch in the cabin.

The idea is that the IC fan would likely need to come on under the same condition as the rad fans, but have a manual switch to have more control when needed.

Brentis

The fans I have ordered will have a tighter fit (well actually the SPAL-type won't fit) on the stock IC. Likewise, with the computer fans, I am going to fabricate a gasket to force the air induction through the IC.

As far as having the IC fan come on at the same time as the rad fan - I disagree. I want them on whenever the car is started, not just when the engine is overly hot.

RX7SpiritR

iTrader: (1)

Here, this should picture will let everyone see that it works, can be done, and wouldn't hurt to do so! ^_^

maxcooper

I tried to wire it up so that it would turn on whenever the radiator fans come on at any speed with a pair of diodes to keep the signals separated. However, one of the signals (one of two, from the fan relay pack) is too low voltage to trip the relay. It turns on when I run the AC, but I don't think it turns on otherwise. I am thinking of using the external output on my SPA digital gauge to turn it on. Either at some set water temp, or perhaps when the fuel pressure goes over some point (as it will do whenever I am on boost). Anyway, I don't have any good tips on grabbing the signal from the radiator fans beyond "I tried it, and I didn't get the circuit right".

I haven't done enough testing to know if/how well it works. I have tried turning it on and watching the air temps on the PFC, but it doesn't seem to make much difference. It might be that I have to turn the radiator fans to run it and that counteracts the effects. Or it might be pulling hot air through the core from the engine bay and then out the fan. The temps don't go up, but they don't seem to drop quickly, either. More testing is needed to explain my observations.

We hardwired the fan on for dyno testing, and it did keep the temps from going too high, but they still seemed to rise to 50C or so (which it pretty high). They were going higher before we wired the fan on.

One issue to consider is that the fan may block "natural" air flow at high speeds, which wouldn't be so great. On the other hand, a shroud over the whole back of the core might be needed to maximize flow and eliminate the possibility of pulling hot engine air through the uncovered areas. I don't know the answers here, but these are some issues worth considering.

I did a lot of research and bought three fans before I decided on the one that I ended up using. There is a wide range of flow capabilities for fans of the same size. The High Performance Perma-Cool was the highest flowing one that I could fit, and it is 1250 CFM, IIRC. I just did a quick Google search ("electric fan CFM") and found 10" fans that flow 650 CFM, 900 CFM, etc. Not all fans are created equal.

-Max

dclin

iTrader: (4)

Hmmm, ok - I guess the best 'switch' is one that actually uses the air temp as the gauge. Did some poking around, and found the temp switch at Mcmaster-Carr http://www.mcmaster.com/ . Search for 'Cartridge Temperature Switch' . (sorry Mcmaster uses frames so cannot give direct link).

The switch is tube shaped and is available in 1/2"X2" 'bulbs'. It's adjustable for temperature (-100 thru +600F) via little set screw on the end. There is a 'close on rise' and a 'open on rise' style, which I take to mean 'complete circuit on temp rise' and 'break circuit on temp rise'.

I was thinking of threading one on the exit side IC endtank, on the end farthermost from the air outlet (to keep it out of the airflow as much as possible.)

I'm assuming it can provide a 12v (or Vb) once it closes (complete a circuit) and trigger a relay, in the 'close on rise' type switch. What do you guys think?

KevinK2

The best control would be 'on' by way of relay off main fan relay, with a manual off switch, and do fan mod-switch.

for low speed, staging use, no ac, use fan-mod switch. for hiway with ac on, turn off ic fan.

I think as max found, ic fan use only will loop hot air back thru rad for hotter air into ic duct.