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


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Dragonfly have you noticed any improvement in cooling/downforce?

 

I can not feel a difference in downforce but I can see that my hood no longer bulges up at triple digit speeds any more. The temp stays rock solid when moving (and air being pushed into the radiator) but when stopped or in nasty bumber to bumper traffic it will start to come up fairly quick because the opening for the air is so restricted. That is not a problem though because I have an electric fan... when I turn it on it pulls the temp back down to normal in less than a minute.

 

As a side note on the cooling I run a 3.0L stroker with 200 to 210 psi static pressure on each cylinder and at the same time I am running a 1" thick and slightly smaller than stock aluminum radiator (with a 2 speed fan). In the past I had heating issues but not anymore.

 

Dragonfly

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  • 2 weeks later...
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I don't know if this has been asked yet, I didn't see anything about it, but what about blocking off the bottom instead of the top? Is there a reason why I haven't seen that here yet? What I'm thinking is that it might be easier to build a channel to divert the air over the entire radiator from the smaller opening and also since the air is coming from higher up that it would be slightly cooler helping the radiator in that aspect. I want to say it would help the front splitter get more air over the top but in my head I see the air traveling up, then hitting the bumper, and just going across the sides instead.

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Another thought I had a while back ago for creating front end downforce was to put tiny wings as the grill. What I was thinking there is that wings create downforce so put multiple wings up front in front of the radiator, you can add and take away wings as need. I just would like some input on that idea as well.

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I got the hardest punch i've ever had (Gave me a black eye BTW) from my HOOD. Years ago I stopped on the side of the road to check something under the engine bay (Think I was confirming that the oil cap was on) and the hood hit me at the temple on the left side... knocked me DOWN... I forgot to put the prop rod up, and I'd removed those springs... Talk about a wakeup call!

 

Mike

 

Thanks. I guess I have some nightmare scenario in my head where I'm halfway in the engine bay and some clueless neighbor comes over and somehow dislodges the prop rod. I'm not usually that paranoid...........really.
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Another thought I had a while back ago for creating front end downforce was to put tiny wings as the grill. What I was thinking there is that wings create downforce so put multiple wings up front in front of the radiator, you can add and take away wings as need. I just would like some input on that idea as well.

I think it's assumed that the bottom will be blocked off, and then they are working on the top. Doing the bottom only makes a lot more sense than doing the top only, but doing both keeps all the air heading through the radiator and that's what you're after.

 

I don't think your tiny wing idea will work because the air inside the grill (if ducted) is moving very slowly. It's a high pressure area and the radiator effectively keeps the air from flowing through at high velocity. The thing that makes wings work is air flowing over them. That high pressure area won't allow the air to flow over the wing, and so it won't produce much if any lift (downforce).

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I'm looking at doing the reduced air intake, and a couple of thoughts. Any angle greater than 15 degrees on the duct is going to cause turbulent flow, which will reduce the effective size of the radiator as the turbulent air around the edges will have trouble going through the rad (actually, intercooler in my case). Given the space limitations, the best solution would appear to be to have two ducts, one feeding from above the front bumper, and one below, both tapered at a max of 15 degrees, and feeding the upper and lower halves of the intercooler/radiator. That way I can have the smallest air inlets without losing out on intercooler/radiator area due to turbulent flow. Thoughts?

 

Note : this is just from eyeballing the front end, I still need to check angles from above/below the front bumper.

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Personally I think mine/Zr8ed's design would be the simplest to do and still do the job, there arent any complex curves, or bends. But it doesnt mean anything if its easy to make if it doesnt work so Ill have to wait awhile to see.

 

Im not sure on what your duct, or the 15 degrees is refering to. Also the need for 2 ducts.

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Well I decided that I wont be using the grill and block off piece I made. Anyone want it? $15 + shipping will take it.... Its painted with undercoating and looks nice.

 

How come the change of heart? Although mine is a little different than yours it works quite well and I would think your design would also work well.

 

 

I'm looking at doing the reduced air intake, and a couple of thoughts. Any angle greater than 15 degrees on the duct is going to cause turbulent flow, which will reduce the effective size of the radiator as the turbulent air around the edges will have trouble going through the rad (actually, intercooler in my case). Given the space limitations, the best solution would appear to be to have two ducts, one feeding from above the front bumper, and one below, both tapered at a max of 15 degrees, and feeding the upper and lower halves of the intercooler/radiator. That way I can have the smallest air inlets without losing out on intercooler/radiator area due to turbulent flow. Thoughts?

 

Note : this is just from eyeballing the front end, I still need to check angles from above/below the front bumper.

 

I personaly don't think seperation of the air getting into the radiator/intercooler is going to be a big deal since they are such a huge obstruction to airflow, using hypathetical numbers off the top of my head lets just say that you are getting airflow into the radiator at 50 mph your downstream side will probably only see about 15 mph so with that much air getting stopped by the radiator you are going to have turbulent air no matter how much you manage to streamline the flow. That is part of the purpose of blocking off so much of the open area in front of the radiator, if you can reduce the volume you can reduce the amount blocked which in turn reduces air wall in front of the radiator so more air is able to push through rather than requiring a fan to pull stagnant convectionaly heated air through.

 

The idea of using two ducts to me would not yield any improvements unless you mounted your radiator and intercooler in a V configuration and had one duct feeding the radiator and the other duct feeding the intercooler. All the above is my opinion, you are more than welcome to prove me wrong but I'm feeling fairly confident.

 

One last comment... I watched this car run several laps racing and he never overheated and I know he's got some crazy angles going on there.

S1010035.jpg BTW thats an oil cooler you see in the duct on the right hand side back by the drivers seat.

 

Dragonfly

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Personally I think mine/Zr8ed's design would be the simplest to do and still do the job, there arent any complex curves, or bends. But it doesnt mean anything if its easy to make if it doesnt work so Ill have to wait awhile to see.

 

Im not sure on what your duct, or the 15 degrees is refering to. Also the need for 2 ducts.

 

A duct is an enclosed entryway to the radiator/intercooler, and in the case of what we are all looking at, needs to be smaller at the entry than the exit so that the air inlet area is reduced at the nose of the car but air still flows evenly through the core.

 

Both your and Zr8ed's work aren't ducts, they are just blanking plates around the nose area to stop air leakage. Dragonfly has built an actual duct, but had the angles too steep with the first version and had overheating issues, so had to make the entry larger. 15 degrees is about the maximum divergence angle before flow separates on the walls... ten degrees is supposed to be safer. Two ducts with 15 degrees divergence in the walls will allow an overall smaller air entry area than one duct with the same divergence.

 

I think you should look up the P51 radiator design and the Meredith effect if this is confusing.

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The idea of using two ducts to me would not yield any improvements unless you mounted your radiator and intercooler in a V configuration and had one duct feeding the radiator and the other duct feeding the intercooler. All the above is my opinion, you are more than welcome to prove me wrong but I'm feeling fairly confident.

 

No space for a V-config without removing the rad support panel and a major rework of the coolers. My thinking on the two ducts is that it will a smaller overall entry path into the intercooler/radiator than a single duct with only a slightly smaller entry than the intercooler size anyway. Besides which, the bumper sits right the middle and must cause turbulent flow anyway. Less air in a diverging duct should slow the air and make it work more effectively - shouldn't it? And reduce the pressure build up in the engine bay (with appropriate undertray).

 

As background - my car overheats once air temp goes over 32C. Was 28C before I moved the number plate down onto the front spoiler and removed the grill. Main problem is I only have space for thermofans, and they just can't flow enough air. Two years ago I did water manometer testing and the only high-pressure areas were in front of the intercooler and the 2cm gap in front of the radiator below the intercooler. I've been sitting on the issue for two years, because I haven't had time to do anything constructive about it, and didn't want to blow $1KAu on a custom alloy rad. And I cycle to work in summer anyway...

 

I'll dig some pics out later...

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I just didnt like how far the grill went down. The other grill I have is only 4 bars tall compared to 6 or 7.

 

My opinion is that the air going into the radiator opening will be slowed down considerably. (your 50mph and 15mph analogy) But at a certain point their is so much pressure in the front of the radiator opening that the most of the air that is headed for the opening is diverted around because of the pocket of high pressure air. Only the amount of air that makes it through the radiator in a second is going into the opening. (kinda like a exhaust cutout that has a cap on it. The pipe with the cap will fill up with exhaust gases and so the gases will continue to flow out the back of the exhaust.)

 

Seems logical but might not be right.

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mopar69, I think that you are right about the air building up in front of the radiator and that is why I refered to that air as stagnant and heated by convection, the only real way to get it through the radiator is with a fan and IMHO the only time you should use a fan is when you are stopped. That is why you should reduce the opening in front to a much smaller size so all (or most) of the air that goes in goes through the radiator.

 

mjfawke, I'm looking forward to seeing the pics you were talking about. I also have an idea in my head that would probably cause you a ton of work if you decided to try it. You said you have a 2cm gap between your intercooler and your radiator (high pressure area) and I am guessing that the radiator is on the engine side of the support and the intercooler is on the opposite side of the support. You also mentioned the bumper and using that as a dividing line for the two air intakes... So here's my idea...

 

leave the bottom of the intercooler where it is at but rotate the top towards the front of the car until it gets within a cm or two of the front bumper, mount it in that position, from the bumper down build your air intake for the intercooler, then from the bumper up build your intake for the radiator (provideing you with a modified V). The upper intake floor is also the lower intake roof and should start at the top of the bumper and go upwards at 10* until it contacts the radiator (use foam weather stripping to protect the radiator from the end of the metal sheet). It sounds like you have two fans "thermofans" so try to place them so one is above and one is below the division point of the air intakes.

 

The lower half of your radiator will receive hotter air due to the intercooler but no more so than the entire radiator is in the current configuration, the upper part of the radiator will receive only cool air that has not passed through the intercooler which should help to lower the engine temp. The space between the intercooler and the radiator will allow plenty of room for the air to pass through the intercooler but will not provide a whole lot of pressure to push the air on through the radiator at that point, that is why you should put one of the fans there, not only will the fan suck the air through the radiator but it will also leave a low pressure area behind the intercooler for the air from the lower air intake to try to fill.

 

I hope all that makes sense and I know that it would require modifying your intercooler piping which would be a huge PIA but at the same time it could be worth it.

 

Dragonfly

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My block off plates can be categorized into 6 main parts.

 

1. I have a belly pan that is attached at the lower edge of the air dam and is level, and goes back to the cross member, and is as wide as possible. It has a curved cutout for each wheel to move and turn fully.

 

2. There is a small block off plate that goes from the top of the airdam (mouth of the car for the rad) It goes back to the Rad.

 

3. The top plate which sits atop the grill, and goes back to the upper rad support (attaches to the underside of the rad support)

 

4. and 5. Vertical blockoff plates that touch the underside of the top plate (#3) and travel down inside of the frame rails, where the bumper mounts attach to (same bumper mounting part as the 280 with the large bumpers)

 

6. Rad support on the inside, has a large aluminum plate that covers the entire rad support, and has a cutout for the rad and i/c pipes only.

 

In the summer, I do not require the use of my electric fan (it is manually switched) unless i'm in traffic or sitting at lights. My hood used to flutter slightly when on the highway. (it fluttered worse when I removed the torsion springs). It no longer flutters at all with the block off plates.

 

Lastly, I built it all to be relatively easy to remove with simple tools, on the side of the road if needed.

 

I have no plans to do anymore work to it other than maybe redo some to make it look nicer...no I did not say ricer!!

 

The belly pan is one that could use some rework. I have had it on the car for almost 10 years with no issues, but is getting a bit scraped up over the years. I may experiment first and block off more of the bottom of the engine bay, by extending the pan on either side of the oil pan, possibly back to the firewall, but thats about it. I choose not to modify the car for ONLY function. I will blend what works, as best as I can with what I like the looks of. I'm not going to cut off the huge fat a$$ off the car for better aero if you catch my meaning.

 

Scott.

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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.)

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