Functional Fender Venting

[Bartman]

So I've been having ongoing problems with cooling on my Z. I've made several changes over the years and it works fairly well until it gets really hot (over 90 degrees or so) and I use my A/C. The other day I test drove my car around my neighborhood on a hot day with the A/C on and sure enough it eventually starting running hot. I pulled into my driveway and kept it running with the A/C on and the hood opened. It started cooling down almost immediately and went back to normal operating temperature, so I figured that I need to find a way to get the air out of my engine compartment. I don't have a vented hood, but I do have vents in my fenders, so I'm thinking I should hook up fans and make them functional.

 

So I pulled one of my fenders and am looking at a couple of fans I already have laying around. It would take considerable amount of work to make these fit, or maybe I can find some smaller ones. So I'm just throwing this idea out there to see if anyone has any input on. Here's a few pic's:

[cygnusx1]

Venting the inspection lids made quite a difference in my car.   I am not sure if it's something you want to do but it works.

 

 

 

[bjhines]

I'm not sure thats the best approach. Have you looked at the threads about sealing the radiator to the front clip, and keeping air from getting under the hood in the first place?

 

The open inspection lids help but things like cowl induction hoods hurt.

Edited September 22, 2010 by bjhines

[hoov100]

You're best bet is to make an air box to the radiator, then make a air box to the fender wells or hood to vent the air after the radiator. Atleast that is my conclusion after all the reading I have been doing on it. You can also tilt the radiator forward a fair amount if you have clearance issues between the water pump pulley and the radiator.

[Bartman]

I have an airbox to the radiator and it doesn't seem to make much difference. I seem to have plenty of air getting through the radiator, but not enough hot air leaving the engine bay. I've thought about inspection lid venting, but since I have fender vents already it seems to make sense to try and use them to rid the engine bay of heat.

[hoov100]

I have an airbox to the radiator and it doesn't seem to make much difference. I seem to have plenty of air getting through the radiator, but not enough hot air leaving the engine bay. I've thought about inspection lid venting, but since I have fender vents already it seems to make sense to try and use them to rid the engine bay of heat.

 

Did you connect the fender vents to the engine bay? The problem with most street setups is that once the air enters the radiator and into the engine bay is has nowhere to go, but under the car which would create and area of low pressure (?) which would cause the high pressure air (?) going around the car to be sucked into the engine bay.

Edited September 22, 2010 by hoov100

[260DET]

Have you looked here http://forums.hybridz.org/index.php?showforum=47

[cygnusx1]

 My Z has trouble maintaining a steady temp on the gauge.  It's almost as if the thermostat is lazy or slow to react.  So when I cruise steady state on the highway, she cools down to just below half on the gauge.  When I drive it in traffic it sits just above the half mark.  After I vented the lids, I did a highway drive and the gauge dropped down to below 1/4 on the sweep.  I had never seen the needle so low on the gauge.  I thought I had run out of coolant so I kept my eye on the head temp reading in megasquirt which maintained about its normal 190F.  The inspection vents really affected the highway cooling efficiency greatly as far as I can tell. 

Edited September 22, 2010 by cygnusx1

[Bartman]

Have you looked here http://forums.hybridz.org/index.php?showforum=47

Yes, I have and I've even posted my radiator ducting with pictures...but no reply. I'm looking for specific information regarding venting hot air out of the engine bay like what cygnusx1 posted (thanks cygnusx1). I'll probably just move forward with this experiment, it's just a matter of determining the best size fans to use.

[GOTHALOSISM]

Why not use some 120mm Computer fans? They should be small enough to fit inside and yet still move enough air.

[Pharaohabq]

Another more stealthy option is to make firewall vents to your cowel area. This way the air is pulled from the top of the engion and out across your windshield. It helps lower the pressure in your engine compartment too. All without affecting that beautiful paint job you have. YOU might also consider opening up the vent holes in your wheel well to the fender vents, since those look pretty small to me. Think about the volume of air you need to exhaust, then the size of your vent holes. Now do you see your trouble? Holes about the size of his inspection lid vents would really help. I'd recommend the Cowel Vents tho they might affect your AC when not on Recirc since the Cabin air intake is also in the cowel.

 

Phar

[Bartman]

Computer fans may work, in fact I seem to remember a post on some other site that did just that - but don't they need to be changed to run on 12V?

 

Venting out the cowl may work, but my cowl panel isn't vented and my outer fender already is, so all I should need to do is add more venting and a fan to the inner fender to move lots of air. I won't be messing with my exterior at all.

[Bartman]

Why not use some 120mm Computer fans? They should be small enough to fit inside and yet still move enough air.

I guess computer fans actually use 12V, so this may be a great solution. I've even found 250mm fans that move over 105 CFM! 250mm fan. I think your correct with the 120mm fans being easier to fit, so I'll probably give them a try. Edited September 22, 2010 by Bartman

[Pharaohabq]

Wow, no Cowel vents, that's interresting... So yeah okay, out the side then... You'll need to make sure you get waterproof fans like these since regular computer fans won't hold up. you should also include a fuse on that circuit just in case.

 

Nice Side vents btw, Were they expensive to have put in?

[Bartman]

My cowl panel is fiberglass with a carbon fiber layer on top and I installed the fender vents myself.

 

This Spal fan may just be the ticket since it is small, moves a good amount of air, and is waterproof: Spal 4" fan

[260DET]

Hood vents like the later S30 OE ones work well, if they are opened out and a small kickup located in front of them. Friend has a similar setup S30 with a big power RB30ET engine used for motorsport and it never overheats, never. Vents through the inner fenders will work too but thats a structural area and should be strengthened if holes are cut in them. But hood vents are best because they take advantage of the tendancy of hot air to rise, info over at the aero section on my cars including S30 and S130 pics.

[Bartman]

So I got the Spal 4" fans I mentioned in my last post and went ahead and set one in place. I think I will fill in the couple of vent holes I made previously, but here's a couple of pic's showing what I'm planning. I also added a piece of wire mesh to the inside to prevent debris from getting kicked by the tire into the fan blade.

[cygnusx1]

 That should flow plenty of air judging by the size of the hole.  It will at least cool the engine bay, hopefully even help the radiator. 

Edited September 26, 2010 by cygnusx1

[Tony D]

Another more stealthy option is to make firewall vents to your cowel area. This way the air is pulled from the top of the engion and out across your windshield. It helps lower the pressure in your engine compartment too. All without affecting that beautiful paint job you have. YOU might also consider opening up the vent holes in your wheel well to the fender vents, since those look pretty small to me. Think about the volume of air you need to exhaust, then the size of your vent holes. Now do you see your trouble? Holes about the size of his inspection lid vents would really help. I'd recommend the Cowel Vents tho they might affect your AC when not on Recirc since the Cabin air intake is also in the cowel.

 

Phar

This is a spurious suggestion based solely on presumption by the suggestor. It's known and been functionally proven that cowl area is the highest pressure region on the car's body up front. This is the WORST place to vent the engine bay...and think about where the S30's INTERIOR FRESH AIR PICKUP is located: the cowl area. (This provides motive force behind flow-through ventilation, there is so much pressure there!)

 

If you vent your engine bay to the cowl, you will have HOT ENGINE BAY AIR pumped into your FRESH AIR INLET FOR THE CABIN.

 

Guys, theories are great, please couch them as such rather than suggestions from a point that looks like you tried it and it works. Venting to the cowl (along with a cowl induction hood) are TERRIBLE ideas for letting air OUT. It's the source of air IN!

 

Duct your intake plenum there, duct your turbo intake there. But for god's sake DON'T EVEN CONSIDER IT AS A VENT! The pressure there even at low speeds is astronomical in terms of water column.

 

 

I endorse the 12V Computer fans over 3" holes under the MC and Battery. The wheel wells are low pressure at speed, and the fans can make a real difference when in slow traffic. Seal the radiator correctly and put the fans on a temp switch that turns them on when above the ambient engine bay temperature on the hottest day of the year driving down the road at 30mph in 5th gear. You don't want them trying to run when going down the road, they will hinder the flow. Likely your fan bearings will take a beating and fail the motors in short order if they are sealed tightly over the holes. If found standing them off with some circuit board standoffs around 50mm allows the air at higher speeds to escape and had my fans lasting. When I made it so it was ducted on the fans out, I was failing a fan or two every couple of months. The only conclusion I came to was that the fans were overspeeding when I was going down the road at 60+ mph and they just couldn't handle the airflow over the fan blades when ALL the air possible went over them. Standing them off seemed to have little or no effect on underhood temperatures at low speed---simply blowing air 'in the direction of the hole' seemed to work well enough. The big payoff from the standoffs was the fans weren't coming apart. I used a Hayden electric fan controller with the probe on the firewall set around 140F (with a 160F thermostat). It seemed to work fine venting to the wheel wells.

 

Good Luck

[Bartman]

So the fans seem to be working well when the car is stopped or moving slow. It was till running a little hot at speed, so I finally completed some aluminum ducting forcing air through the radiator. Although it hasn't been too hot yet, I think I may finally have this issue resolved!