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After doing some reading.. I blocked off the upper grill *pics*


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Check on page one and 2 for pictures.

 

With a smaller front opening wouldnt there be less pressure infront of the radiator and therefore less air flow through the radiator?

 

I think the biggest thing is determining if the pocket of high pressure in the radiator opening diverts air flow around the front of the car. If it does then leaving it the same size and only controling the air flow to go in to the radiator is the only problem. If not then you need to find a way to make the opening smaller. (possibly my grill block off plate thing.)

 

The smaller the opening on something the greater the pressure but the lower the volume. The object is to create the most correct balance you can between the two. If the opening is to small you will have to much pressure and not enough volume which will cause overheating due to lack of heat transfer. If the opening is to large you will have to much volume and not enough pressure so the air will dam up in front of the radiator pushing cool air around the car while becoming heated by convection and stagnant by lack of flow, of course this causes overheating as well.

 

In the old days to remedy the above problems they put a fan on the front of the engine right behind the radiator to pull the air through the radiator (any time the engine was on), over time they added shrouds to make the fan more effecient. Now in this day and age they have done away with the engine driven fan on virtualy all cars and instead rely on a better design in front of the radiator to get the most use out of the air. The fans on these newer cars are electric and only turn on when truly needed, as you may notice the only time the fan comes on in a new car is when the car is in very heavy slow (or stopped) traffic or when the car is under an unusualy heavy load.

 

Dragonfly

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I haven't had time to grab pics from the front of the car yet, but just to clarify a bit, the IC sits in the opening in the radiator support panel, and there is a gap below the bottom tank of ~ 2cm.

 

I'm thinking 2D CFD to look at the interaction of the front bumper, ducting, IC & radiator. Maybe even create a 2D CAD of the centreline of the car to play with front panel work etc. Linux -> Blender (CAD) -> Gerris Solver & Viewer.

 

Here is a pic of the engine bay...

dcp_0002a_205_thumb.jpg

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Id suggest not doing much on a computer. If you just get out there and do It, it works alot better. Theres so many things that are variables that you really cant do with a computer (without it taking forever).

 

I "planned" my parts out for months and built templates and bought things and ended up not doing what I planned. It works good to just get out there with scissors and some posterboard and make real templates.

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I'm sure I could waste a lot more time building things which don't work... If I had known the Z had such a problem with trapped air in the engine bay, I would have used an air/water cooler instead of sticking the IC in front of the radiator. Or had the engine moved back to the firewall and routed the pipes differently so I had clearance for the factory fan. Hindsight...

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I had problems with some of my previous Z with vapor locking, 240 & 280. This only ocurred while pulling a long hill in slow traffic. I would only think of cutting off air flow if I had a LARGE electric cooling Fan and duct the air opening into the radiator.

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You know, I think I've read pretty much every post in the windtunnel section, and I've been following it since day one, and I love all that's gone on.

 

But there isn't much talk about something that i think about quite often with S30 engine bay/radiator air.

 

We know that there's quite a bit of lift being gererated by air that wants to leave via the bottom of the engine bay. If you block of more and more of the bottom of the engine bay, that air is gonna have to work harder and harder to escape. I know some guys have done, and plan on doing fender area air exists, but why doesn't it seem like anyone talks about hood venting? If you persuade the air to go upwards you'll be creating downforce instead of lift, and if it's engineered well the air traveling over the hood might create a scavenging effect won't it? This might even help pull air through the radiator, lowering coolant and air temps even more.

 

You'd probably create a little more drag than if you exited air via the fenders, but I'd imagine it'd be minimal, like going to a wider tire. Reducing drag seems much easier to do at the back of the car, and on a few other problem areas.

 

 

I just can't stop thinking about this every time I come over here and read more updates in this thread. It just seems like a logical part of this discussion to me. With how much room most people have in the front of their engine you could create a duct to bring air in, or block off areas for air to escape, but then create a duct on the back side of the radiator to push air upwards through the hood. If the entire bay was sealed off well enough you might not even need duct work.

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If you block of more and more of the bottom of the engine bay, that air is gonna have to work harder and harder to escape.

 

Not sure where you got this idea from - we're talking about restricting airflow into the nose of the car (efficiently, otherwise the full radiator area won't be used). Yes, bonnet vents can work - but look at the air entry size and then think about how big the vents would have to be to vent that much airflow. At best, it's part of the solution. Ducting from the rad to bonnet vents is, I think, unlrealistic - there just isn't enough space to build proper ducts (certainly not in MY engine bay).

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Not sure where you got this idea from

 

The fact that we've seen plenty S30 cars with fiberglass or carbon hoods that flex like crazy at speed. The air in the engine bay DEFINATELY, without a doubt in my mind, has a hard time escaping that engine bay. Just look at how much the figures changed on the wind tunnel data on tests #26-28. They blocked off the fender vents, hood vents, then uncovered the hood vents, then uncovered the fender vents, and blocked up the front end opening.

 

Keeping air from getting into the front end reduces lift dramatically. If you want to keep temps as low as possible, you're gonna need to vent that air out of the engine bay somehow, otherwise you're creating tons of lift.

 

If you block off the air's main escape, the bottom, then the air will have nowhere to go, and you'll build up pressure in front of the radiator because of the pressure area behind the radiator.

 

 

And yes in most cases ducting won't really be an option for many people, but simple venting should help quite a bit. I really do believe that if you want to maximize your efford in front of the radiator, you HAVE to take into account what's happening behind the radiator. If you're just gonne leave the belly stock, then fine, the air will just push the nose up at speed. Otherwise you need to figure out how to get the air out of the engine bay somewhere else other than downwards.

 

There's a whole thread discussing hood vents, and I believe we've only scratched the surface of solutions at this point.

 

http://forums.hybridz.org/showthread.php?t=122509

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No plan at this point. Car is coming off the road shortly for some new parts - diff, gearbox, flywheel, turbo, possibly some GTR cams. While the engine is out (broken exhaust stud), I'll R&R the rad and IC, seal all of the openings, then pull out the cardboard for a mock-up. Still trying to find the time to do a CAD/CFD mockup. There was also a good article in a recent Racecar Engineering mag showing differences in flow and pressure distribution through a radiator with ducting - the radius on the entry is very important...

 

And yes - cobwebs. It's summer and the spiders are in full swing. There's a redback (black widow for you guys) or two under the spoiler as well.

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The FMIC on my S130 is having diffuser sections welded to it front and back, when its done I may be able to put up a pic if anyone is interested. It sits in front of the radiator so this has influenced the design.

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  • 4 weeks later...
  • 4 weeks later...

Now that I have a S30 I'm gonna be thinking about blocking off parts of my front end.

 

Though I'm worried about in traffic temps since I'm running a unshrowded fan. Maybe I should keep my electric fan sitting at home handy. Didn't really like having to put the sensor in the radiator fins, I'd probably just wire up a switch.

 

I'll post pics once I start of course. Will probably be a month or so. First order of buisness is to get the air dam to fit correctly, and possible warp it back to normal shape.

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  • 3 months later...

Here's my version. I mocked it up kind of quick and didn't put too much thought into it so i'm open on any sugestions. I used to have a problem with my radiator cooling too fast but, now my water temps are much more stable at 75-85 celcius so I know i'm reducing the amount of air flow from the front.

 

I used a 3x6 sheet of .06 aluminum and rivited it all together. I still need to seal everything up and finish the brake ducting before I do actual testing but here it is:

 

IMG_1680.JPG

 

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IMG_1682.JPG

 

IMG_16841.JPG

 

IMG_1689.JPG

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