I can verify that. I've owned two Fieros. Length might be a concern if you were trying to adapt them to a 68 Fbod though. The straight parts are relatively short.

 

I'm not adapting Fiero cooling lines to my 68, but I think I will go with aluminum. Drain plug in the lines sounds like a great idea.

Hunter

 

There's a rule of thumb for radiator size in relation to inlet size. IIRC, it was around 3:1. This slows down the air, and increases the pressure differential across the radiator, helping to push it through the core. If ya have a 28x20 rad core, the 3:1 ratio works out to be about 186 in^2. You'd need the equivalent of fourteen round 4" ducts. Maybe the ratio is slightly more, but that's the general principal. As for the front ground effects, you'll want the pan under the nose to have a few degrees of nose-down to generate downforce. Somewhere I've got it written down what we use for the GroupA Racing TransAm car, but that's a nice way of increasing front downforce on a closed wheel car.

Is it worth it to move the radiator to the rear of the car? Figure out how much the associated weight of the 20' of -20 hose would be. Getting an extra percent or two of rear weight might not be worth the 50 lb (WAG) penalty of carrying the extra water and hose, especially if you've already got ducting/shrouding in place for the intercooler.

 

I agree with andris, unless you need to do it for room for the turbos( in 68 I would think not ) I wouldn't mess with it..

 

Andris, I’ve never heard of as high as a 3:1 ratio, but the ratio depends on fin density, core thickness and entry airspeed anyway.

You left out 2 other important factors. That expansion has to be a fairly smooth curve, if you suddenly expand to a chamber with 2 or 3x the cross section of the tubes feeding it all you’ll accomplish is cause turbulent flow without the pressure increase that you’re looking for. For that matter, multiple tubes will each have a boundary layer along the walls, the more tubes you have the larger the relative cross section you need to feed the same amount of air. Mostly, this means that you’ll never get this working great with lots of smaller inlets feeding a chamber that holds the radiator. Second, you need a nozzle for the outlet to reaccelerate the airflow back up to the speed that the vehicle is moving at. If you release it behind the car traveling slower then the speed you’re moving at you will just cause turbulence which will probably result in more drag then what you’ve cleaned up by installing the full pan. Worse, you will disturb the down force that you will want to produce at the back of the car if you intend it to be stable at any significant speeds. That nozzle should probably be adjustable so that it could be properly tuned to accelerate the airflow but not be a restriction at higher temps/airflows.

There has been an assortment of cars built with rear mounted radiators (on purpose built race cars you’re usually talking turbocharged cars that use the original radiator location to mount intercoolers), but they were all designed with rather large, smooth and properly shaped openings in the rear bodywork.

WRT to the weight: assuming that you use aluminum tube at a reasonable gauge (I figure that anything under 12ga, roughly .1” thick would not be durable enough) you’re looking at 10-20lbs for 2 6’ lengths (I figure that that would be the bare minimum that you would add to the car, assuming perfect routing…), and it would be full of about 25# worth of coolant. Really, not that bad. Braded steel lines would weigh more, though you might be able to get away with 18ga stainless which would come in at about 7lbs.

 

Alright well for now I am gonna put the rad problem on the back burner. All this hot air under my hood is just gonna lift the nose up, so I wanna find a way to get it outta there.

So the 67-68 SS's had two rectangular induction stacks, taht were merely there for looks. I was thinking if I cut out the two, and had them open and close with some kinda motor, maybe a wiper motor, I could vent hot air outta the hood when I need to, and when it rains or its parked, they would close to protect from rain, ect.

Would these be big enough to vent properly, and would they need help venting, from say a small fan, or would the hot air just leave itself since its rising anyway?

Anyone have any suggestions? I don't wanna do the fender vents, I hate the look of them after i did some messing around in photoshop.

Hunter

 

At speeds above 110 or so, the front end of the Z28tt gets floaty (straights at Memphis, LimeRock, Watkins Glen, etc), due to the huge front mount intercooler and sealed ducting. I'm going to duct the hot air from the intercooler/radiator up through the hood, and have been looking at the C5R, Vipers, etc for inspiration. I'm not a body person, so this is going to be a real challenge for me.

 

Andris… before cutting a hole in the hood, have you played with blocking part of the front end of the car off? Really, I doubt that even with the turbos you need all the open area that camaros have up front to keep it cool at speed. Firebirds have significantly less and don’t have any problems.

If you’re going to cut the hood for a heat extractor setup, you’ really need to duct things to get them to work right. Basically you need a pan that comes up from the lower radiator support, across the front of the engine to the hood. I’ve seen some nice setups done in mustangs, but haven’t seen it done in an F-body (shouldn’t’ be that big a deal, f-bodies have more room in the right places, if it can be made to fit in a mustang…).

 

I think he meant all of this front is sealed off, so that leaves nowhere for the hot air to go. That is what my problem is going to be, as the lower valance will be all intercooler, and the front grill will have to large scoops for the front brakes. The rest will be sealed up. Air won't be coming up from under that car into the engine compartment because of the underbody pan.

As I said above, I think using the 'induction stacks' on the SS first gen's as a good way to vent hot air. I was looking at computer fans today, and found single ones that flow about 114 CFM. Four in a line on each stack, for a total of 8 fans * 114 CFM each is about 900 CFM. Route these all to a power supply and then into a cig lighter adapter.....well see if that works.
Is 900 CFM enough? I would think so seeing that hot air will be rising anyway, so this woudl just help.


Hunter

 

Man, don’t take this the wrong way, but you need to do a lot of reading/learning before taking on this project. Just about everything that you’ve posted about it has been roughly backwards or unmanageable, and although there are a lot of knowledgeable people here catching most of it, there is no way that we’re going to catch it all before it starts costing you. Without either enlisting full time help from someone knowledgeable about high end car builds or learning a hell of a lot more yourself you’re just going to end up with a strange conglomeration of cool ideas that won’t really work together.

WRT to the latest here… You’ve pretty much got it backwards. Most street cars take in air in front of the radiators, and it comes out underneath the engine bay. In most cases, if you opened anything on the back half of the hood you’d get airflow in, not out, caused by the relative high pressure area at the front of the windshield. The way hood mounted heat extractors work is that they are usually mounted toward the front of the hood and usually have a spoiler at their front edge that deflects air traveling over the hood upward creating a low pressure pocket behind it that sucks hot air leaving the radiator out through the hood. They also had duct work which would accelerate the air flow before it left the heat extractor.

 

Of corse I need ot learn, that is what I am doing, and doing the asking and learning before I do anyting, so I dont do lots of mistakes that cost me.
But no I didnt take that the wrong way, its kinda hard to **** me off

Now, I do know that farther u get back on the hood, air starts to get high pressure, and will force into the engine comprtment if an opening is present. Now that I think of it, the vents I was talking about would be far enough back to work backwards....crap.

WS6 TA- How do you suggest I vent hot air? You seem to know lots about this, so pour your knowledge on me. I am thinking of not putting a pan under the engine compartment, so maybe that is my best bet, to vent hot air from under the engine. But lemme know what you think.

As for air rom the outside to the radiator, do the NACA ducts on the quarter windows sound feasiable? Two each side? Ducting and removing the air will be a different story.

Hunter

 

That depends on how much you’re willing to ‘ruin’ those classic bodylines. I know of someone that did something like you’re talking about to a ’68 mustang (with what looked like an aluminum, supercharged 427 side oiler, but actually mostly aftermarket and somewhere north of 500ci) and after carefully measuring everything, decided that he had to lengthen the car 8.5” to fit everything that he wanted in the car, the way he wanted it.

If you want to keep the stock lines, I’d probably play with a partial bellypan, probably from the front air dam to maybe the back of the K-member, then open to the firewall, then closed again.

If you shape things well, and size the opening to keep the airflow coming out at a higher velocity then what came in, maybe you could control lift under the car. I’m just guessing here on if it would work, but if you kept the velocity higher then what is flowing over the top of the car you’ll actually create relative downforce (not as much as completely preventing airflow under the car), which might be possible without significantly restricting the cooling.

Again, how much are you willing to change the lines? If it’s quite a bit, maybe something like fender bulges at the back of the fenders (basically your fenders would stick out an inch or two past the doors) to vent out air from under the hood. Again, you’d have to size it correctly… ore maybe a heat extractor towards the front of the hood?

I think I’ve pretty much responded to that already. I don’t think that you can get nearly big enough intakes to get a rear mounted radiator working right without significantly changing bodylines. I’m fairly certain that they’d have to be bigger then the rear quarter windows, and you’d have to create some reason for air to go in them (in most cases we’re talking about a scoop of sorts that would stick out past the boundary layer of air on the body). The shape of NACA ducts does induce airflow, but they’d have to be huge (and in my opinion tacky) to get you enough air flow).

Lets be realistic, are you trying to build an optimum performance machine, or are you trying to get the best performance possible in a ’68 Camaro envelope? Will form follow function, or will form follow GM’s basic styling? For that matter, will you need the cooling necessary to run this thing lap after lap on a road course, or just enough that it doesn’t overheat tooling around town and at the dragstrip?

One way you end up with a ’68 camaro that has some cool work done to it, the other way you end up with something that is a cross between a ’68 camaro and a viper with a little testarosa/Diablo/(whatever else) built into it…

 

Being realistic, I want form to follow function in almost all aspects. Body lines being changed, would have to be tasteful, but I would be open to them.

For the body pan idea, wouldn't putting the hot air out under the floor pan defeat the purpose as this would lift the body? Though it would be better than the hot air just stayin under the hood, I like the idea of hot air venting out of the rear of the fenders. I do not think that having two inches of space betwen the fender and the door hinge would hurt the appreance.

If I used fender vents, the body pan running the full length of the car would be appropriate right? This would keep any air that gets under the car away from the aero 'dirty' parts like the suspension and such. Also venturi tunnels could be molded to accel the air and cause downforce. Also an adjustable spoiler would be used to aid more in downforce.

I am thinking if I went that route, leaving the radiator up front would be the best bet, just because I wouldn't have to worry about getting rid of the radiator air in the back, I could just use the fender vents and be done with it.
I agree that it would take a large scoop, and probably at least 3-4 inches away from the body to get good airflow. Do you know how to calculate that thickness of the boundary layer at speed? It would change with speed obvisouly. Maybe there isn't even a calulation now that I think of it, probably just need to work with testing to figure out what works.

Have you done any work with rear diffusers? Can you point me in any direction to sites or books for information on them. I have a few books about aerodynamics, but most say little or nothing about rear diffusers.

Hunter

 

more then if you blocked it completely, less then without the air dam and belly pan if things are designed correctly.

it will not just stay under the hood… If you manage that you’ll overheat a bunch of stuff.

that happens to be my favorite also, probably make ‘glass fenders that sorta blend the original ’68 lines into the back of the fender vents, sorta like a viper, and then keep the rad in front…

sounds good… remember downforce usually = drag, so you basically want to find a happy medium.

There standards, but it really depends on what the general body shape is doing in that area. It can be tested fairly easily using tufts of yarn taped to the body and just watching them.

Do a search… we’ve had discussions of this here before and I know that OldsSStroker and I (and others) put out extensive lists of good reading (I think that the 2 of us have read almost the same list of books ). For some not to too technical evaluations of this (but technically correct) I’d probably start with “tune to win” there’s a reasonable discussion of aerodynamics and proper heat exchanger ducting (check the others in the series, there is a continuation in just about all of them, that will make sense if you see the books, if I remember right “engineer to win” picks it up the most).

 

Listen to Mark (WS6TA). He's telling you good stuff.


Here's a replay of my earlier post:

"I strongly recommend Race Car Aerodynamics: Designing for Speed by Joseph Katz, and published by Bentley Publishers to you. It's worth way more than it's $35 price, and will help you immensely in this project."

Just about everything that's been brought up here, and a lot more, is covered in this book. There's a minimal amount of math, but loads of graphs, diagrams and excellent explanations. There are also hundreds of other references if you need more data.

Pg. 214 - 224 on Internal Flow will answer virtually all the questions discussed here.