I am considering venting the hood behind the radiator and fan to improve cooling and lower operating temperatures. Something like this:

Proposed Evo Vent in FC Hood

Has anyone done something similar? If so, did you see cooler operating temperatures?

TIA,

 

what mods if any are done? what kind of driving are you doing? the factory cooling system works well with all the pieces still intact

 

I myself ,am getting a na hood and getting a fiberglass vmaxx style vents. Cutting the hood, reinforce the cut area and mold the vents on the hood. My car is a t2 with a fmic, by the way.

 

I have experience with similar systems on aircraft. It will work, but it will require custom ducting to work well.

Your car has been running fine for... 14 years is it? I'm thinking that a hood vent is not necessary unless you just like the looks. Have you recently changed anything that caused the over-heating problem to manifest, or did the engine just start over-heating for unknown reasons? Also, is the over-heating problem at low speed or high speed?

It would be easier for him to list what is not modified, lol.

 

your idea is similar to the shine hood

https://www.rx7club.com/shineautopro...d-hood-842889/

look at POST#28.

or this:https://www.rx7club.com/2nd-generati...npipe-1061356/

 

Its a 3-rotor convertible.

 

People have done something similar with the mustang vent. http://media.caranddriver.com/images...s-1280x782.jpg
I've seen it used on many turbo hondas and is very functional with no ducting needing to be added

 

I've got the sexy style vent hood and it drops my water temps by 10 degrees with no extra ducting around it. Shine Auto makes a replica of it.

I have a taurus efan and it blows 50/50 in the engine bay and some out the vents themselves.

Make sure the vent has a RAISED LEADING EDGE. This causes the vent to extract air from the engine bay.
here's some pics for reference to location and raised lip. Sorry if they're big. Old pics I found from old posts.

 

The RXX-7 Homepage

 

lol i got it. i know the car, didnt put 2 and 2 together. dat unicorn doh!

 

I re-installed the stock A/C system. As a result the operating temperatures have gone up by 20+ degrees. The problem occurs at highway speeds. At idle, it's usually OK--about 185 degrees, which I could live with. Before you ask, the higher temperatures occur WITHOUT the A/C on.

Thanks for the feedback. Any suggestions on the configuration of the ducting?

 

Thanks. It's good to see that I'm not out in left field with my idea.

 

I love it, when you use the word "functional".

 

Thanks. The Evo hood has the raised leading edge, which is why I though using it was a good idea. I am delighted to hear about the 10 degree drop in temps.

 

So the condenser is blocking airflow to the radiator? Why don't you just mount it somewhere else? A modern aftermarket parallel condenser may work better anyway. An AC shop should be able to recommend a good solution.

- Divergent inlet duct(s), 1/4 to 1/3 the cross-sectional area of the heat exchanger core(s).
- Convergent outlet duct(s), 15% larger cross-sectional area than the inlet duct.
- Try to avoid placing the heat exchangers in-line, stagger them if needed.
- If you don't run a duct to the hood vent, then be careful when driving the car at high speed until you are sure that no strange aerodynamic effects are trying to rip off the hood or lighten the front end to the point that steering or stability is affected. In theory, the front lip should help keep the front of the car planted and create a nice suction zone over the vent. However, if theory always worked, then there would be no such thing as test drivers or crash test dummies.

 

Yes.

I really don't have any room to play with.

I had never heard of a "parallel condenser". After a couple of minutes with Google, I think that might be a good solution. I'll go consult some experts. Thanks


First of all, thanks for the specs and the picture. There's no room for a duct to the hood vent. (Sometimes, it's almost like the engine is too big.) I completely agree about theory. My working plan is to mount the hood, then drive it for a couple of weeks to see if all works well. If that all seems OK, I'll try to see when they'll have a track day at VIR.

 

George,

I have the same issue and I have a vented hood, my car has the complete Tamon designs front end on it.
It's stacked as such: FMIC, stock oil cooler, stock A/C coil, Koyo rad. It runs plenty cool at sustained speeds but as soon as. I get on the highway and the car gets hot from getting on it good, it stays hot. I think part of it is due to the e-fan I have not turning off and free spinning and highway speed, if I turn the ignition off and coast then cut the car back on it will cool down. Does your e-fan shut off at speed?

I think I'm going to try temporarily wiring a switch into the relay power circuit to cut the fan off on the highway and see how it affects things. If it works I would like to look into figuring out a way to wire the fan relay power into some sort of speed activated switch.


Also, did you sell Fritz a GT35R turbo kit years ago? If you did I'm pretty sure it's on my Vert!

 

This experiment makes no sense but could be interesting to try, I guess.
Where is your fan trigger/switch located and what is its threshold temp?

 

It's a black magic fan, it's set around 190-195 and the t-stat probe for the relay is up around the inlet. I want to switch things up down the road if I get around to changing ECU's and fixing things the PO did. I haven't had as much time to wrench as I would like.

 

I've never thought highly of that fan or the "probe" style of temp sensor and would guess that's half your problem right there.

 

Why is that? The fan doesn't turn off and free wheel, I think at highway speed it is blocking airflow causing it to cavitate, but I am no physicist.

Here's a dirty pic of the hood/front.

 

Try this:

In the driveway and from a cold start, let her idle a few minutes (2-3) then rev to 3Krpm and hold it till the fan comes on. Confirm it comes on at 195°, then let off the gas and let it return to idle.
How long does it take for the fan to go off and at what temp?

If the fan stays on but your gauge shows the temp falling, you need a better switch, preferably one in direct contact with the coolant.

If the fan stays on and the temp does not fall, your fan ain't pulling enough air.

I do this with the hood up because it'll cool down faster.

All you're doing is confirming the basic function of the system by removing the intake airflow variable.

 

im just glad to hear you have AC that works, how cold is it?

 

most fan switches will have a built in hysteresis. the fan might turn on at 195*, but won't turn off until 180*, this is to prevent rapid switching off and on between 194 and 195*...

that being said, I have my fans controlled by me ECU based on the oem temp sensor.

the fan I use also has rubber flaps that blow open at high way speeds to bypass the shroud

 

Attila, check John Huijben's build thread, he put a nice hood duct into his 4 rotor FC, he moved the top of the radiator forward to give a bit more room:

https://www.rx7club.com/build-thread...-build-974831/