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914World.com _ 914World Garage _ Thinking of a different way to duct a radiator
Posted by: Dr. Roger May 29 2005, 10:57 PM
I was thinking of using two smaller radiators and two fans and ducting not only the intake but the exhaust through the fenders.
This would allow more usable trunk space....
Posted by: skline May 29 2005, 11:06 PM
Try it, take lots of pictures of how you are doing it. When it is done, test it out real good, drive in some heavy traffic, stop and go, and drive up some steep hills or up to the mountains and let us know how it works. I thought about all different kinds of ways to do it, when it was all said and done, the only way to go is a Renegade system. Thats just my opinion though.
Posted by: McMark May 29 2005, 11:17 PM
IMHO, we need more people thinking "outside the box" and trying out new ideas. There's a lot of hear-say that is passed around. Do it Roger.
I'm not clear on where exactly you're thinking of placing the radiators. Care to modify a picture?
Posted by: neo914-6 May 29 2005, 11:24 PM
Roger,
This is what I plan for my V6 conversion to save the trunk space. I don't know if it will work for a V8...
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Posted by: Type 4 May 29 2005, 11:39 PM
If you use finned tubing you get about 170 sq in per ft of tubing cooling surface.
That will pulls alot of heat out before and after the radiators.
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Posted by: JB 914 May 29 2005, 11:54 PM
are you thinking the rear fender wells for the radiators?
Posted by: Dr. Roger May 30 2005, 12:09 AM
Hmm, I hadn't thought of the rear fender wells but that's an interesting proposition.
I don't have the rear flares to duct from. Did you have some thoughts on that? Draw air from where?
No I was thinking almost exactly what Felix's pic shows. Only from the existing light openings in front bumper.
You guys are great for bouncing ideas by.
Finned tubing?? Who would have thunk it?
Any and all ideas are greatly appreciated.. 
Posted by: Dr. Roger May 30 2005, 12:23 AM
ok, this is a very lame pic but i kinda' shows what i'm thinking...
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Posted by: JB 914 May 30 2005, 12:35 AM
if you were going to use two small radiators why not attached them to the rear engine lid w/ a fan underneath?
I think you could use some modified fab like Scott T. did on his suby conversion to draw air upwards then thru the fans onto the radiator and out the lid grills. kindof a scoop?
Posted by: Dr. Roger May 30 2005, 12:37 AM
wouldn't that draw air from around the headers/engine area??? pre-heated air trying to "cool" the radiator water?
Posted by: redshift May 30 2005, 12:43 AM
| QUOTE (rogergrubb @ May 30 2005, 02:23 AM) |
| ok, this is a very lame pic but i kinda' shows what i'm thinking... |
Oh Jeesus! Did http://www.914world.com/bbs2/index.php?act=ST&f=2&t=16519&hl= ask for a diagram?
M
Posted by: JB 914 May 30 2005, 12:45 AM
| QUOTE (rogergrubb @ May 29 2005, 10:37 PM) |
| wouldn't that draw air from around the headers/engine area??? pre-heated air trying to "cool" the radiator water? |
Probably some.
But, everyone told Scott T. his way wouldn't work and he drove it cross country with no problems. He did some fabrication to draw air from under the car into his radiator which fit in front of his subaru engine. why couldn't you do it in a similar fashion and draw the air up further?
I'm just throwing some alternatives. The Renegade system is proven and works great. But, you loose the trunk and have to cut the wheel wells.
i was thinking out loud.
Posted by: Dr. Roger May 30 2005, 12:52 AM
very interesting on that Subaru idea.....
so he ducted from underneath the car for the fresh air source?
as you all know, having the radiators up front allow for the ram effect at cruising speed. no fans.
was the subaru setup for "no fans" operation at cruising speed?
Posted by: Dr. Roger May 30 2005, 12:54 AM
| QUOTE (joe buckle @ May 29 2005, 10:45 PM) | ||
Probably some. But, everyone told Scott T. his way wouldn't work and he drove it cross country with no problems. He did some fabrication to draw air from under the car into his radiator which fit in front of his subaru engine. why couldn't you do it in a similar fashion and draw the air up further? I'm just throwing some alternatives. The Renegade system is proven and works great. But, you loose the trunk and have to cut the wheel wells. i was thinking out loud. |
all of the front radiator solutions i've seen so far are sooo intrusive.
i think the aluminum ducting would work and it would look cool. i just want to impress the tough crowds at the next IHOP breakfast......
Posted by: JB 914 May 30 2005, 12:55 AM
| QUOTE (rogergrubb @ May 29 2005, 10:52 PM) |
| very interesting on that Subaru idea..... so he ducted from underneath the car for the fresh air source? as you all know, having the radiators up front allow for the ram effect at cruising speed. no fans. was the subaru setup for "no fans" operation at cruising speed? |
it's Scott Thatcher. look up his posts. i'm sure he has put some pictures of it up here. i don't remember if he had a fan or not
Posted by: redshift May 30 2005, 01:00 AM
What about 2x what Felix has there, that... new thing...
One on each side? Make sure you cage the crap out of the inside of the wheel house... you don't want her paddling a rock through yonder..
M
Posted by: Dr. Roger May 30 2005, 01:22 AM
| QUOTE (redshift @ May 29 2005, 11:00 PM) |
| What about 2x what Felix has there, that... new thing... One on each side? Make sure you cage the crap out of the inside of the wheel house... you don't want her paddling a rock through yonder.. M |
yea', i'm wondering how the boxster protects it's radiators...
i'm thinking more towards the inner fenders for the exhaust. just ducted in.
NOT inline of a potentially fatal thrown rock.
Posted by: redshift May 30 2005, 01:26 AM
Oh I was totally thinking the same kind of thing... but I couldn't think of an elegant way to carry it on out the side, and away from the brakes..
M
Posted by: Dr. Roger May 30 2005, 01:33 AM
exhaust hot air like this???
Posted by: redshift May 30 2005, 01:37 AM
The only thing I could think of would look silly on a teener... a BMW 507 type exit, or God help us... gills.. I mean there isn't enough room, width wise, to pull a 935 trick..
No, no... and NO!
M
Posted by: neo914-6 May 30 2005, 02:28 AM
Roger,
There's been discussion about this many times before, I don't have the links right now. Besides the front common trunk configuration I know of no other successful solutions in the 914. The problem as you've noted is air flow.
Toyopet developed one for a 911 housed under a large turbo tail.
I've seen a large oil cooler mounted between the tail lights, large air to air intercoolers in the rear trunk but these wont exchange enough heat to cool a V8.
If you read the jaide link you'll see they layed their radiator low enough to still package the spare tire and tools. Prior to that they tried to mount twin vw radiators in the engine bay sides but abandoned that design for the conventional front mount.
If you had large enough side scoops and AIR type flares you may be able to mount radiators at the intake.
When I first built my V8 20 years ago, a guy followed and stopped me because he knew I had converted it. He claimed he successfully mounted a radiator in the engine lid with several fans in his 914 before he sold it.
With newer technology and materials you have a better chance of developing a new system that works. An electric pump and speed controller will give you flow control. The finned tube idea may work if you made the rockers the heat exhanger. Just remember you need to find the "right" heat exchange rate, volume of liquid, and air management. Of course you would have to make it look good too... 
Posted by: neo914-6 May 30 2005, 02:48 AM
| QUOTE (rogergrubb @ May 29 2005, 10:09 PM) |
| I was thinking almost exactly what Felix's pic shows. Only from the existing light openings in front bumper. |
I was trying to convince Bill P to use these opening on JLO but he decided to cut the nice chrome bumper's center for the Renegade rad...
Posted by: d914 May 30 2005, 08:02 AM
not sure if it would be large enough but they make double and triple pass AL radiators for the jeep cherokee. the dimensions are like 10x30. The shrouding would be more like the gt oil cooler, bottom exit and most of your trunk would be available...
Posted by: brant May 30 2005, 11:24 AM
Roger,
I've done it with oil coolers and it works well.
and there are some other vintage 914 race cars out there that have also done it with oil.
you will have to give up the headlights entirely, so it my not be workable for a street car.
here is a pic:
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Posted by: brant May 30 2005, 11:24 AM
and exit:
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Posted by: neo914-6 May 30 2005, 11:45 AM
Brant,
I always love seeing that work! What are the dimensions of the heat exchangers? If I use the Boxster rads, I will surely need to cut the longitudinal bracing...
Posted by: brant May 30 2005, 11:50 AM
they are the twin pass models.
14 3/4 by 9 1/4 by 3
Here is the link:http://www.fluidyne.com/pl_theoc.html
Posted by: davesprinkle May 30 2005, 10:00 PM
Here's something to keep in mind if you decide to run 2 rads. If possible, you should plumb the rads in parallel rather than in series. A parallel approach will be a bit more difficult to fabricate, because you'll need two Y-connections, but it will cool better than will a series setup. This is because thermal systems transfer heat more efficiently with greater delta-T (difference in temperature). If you plumb two rads in parallel, the coolant entering each rad will be at engine-out temp; however, if you plumb both rads in series, then only the first rad will have coolant entering at engine-out temp. Because the second rad will have a lower delta-T (difference between coolant temp and air temp), it will be less efficient at further removing thermal energy from the coolant.
To get an intuitive sense of this, consider the following thought experiment -- you have a quart of water at 70'F and the assignment to heat it to 100'F in the least amount of time possible. Which will be the fastest method: by placing the water on a 100'F hot-plate, or by placing the water on a 200'F hot-plate? (If you chose the first option, then I'd suggest you stick with air-cooled engines...)
The other advantage to running the rads in parallel is that such a setup will have approximately 1/4 the flow resistance of a series setup.
Posted by: Dr. Roger May 30 2005, 11:05 PM
Damn, this is such good information. =-)
I was at Blockbuster tonight waiting in line and noticed this.... The new Lotus Exige. Check out the hood..... Wow.
Hey Andyrew...... wadda' U think?
Posted by: neo914-6 May 30 2005, 11:22 PM
| QUOTE (davesprinkle @ May 30 2005, 08:00 PM) |
| Here's something to keep in mind if you decide to run 2 rads. If possible, you should plumb the rads in parallel rather than in series. A parallel approach will be a bit more difficult to fabricate, because you'll need two Y-connections, but it will cool better than will a series setup. This is because thermal systems transfer heat more efficiently with greater delta-T (difference in temperature). If you plumb two rads in parallel, the coolant entering each rad will be at engine-out temp; however, if you plumb both rads in series, then only the first rad will have coolant entering at engine-out temp. Because the second rad will have a lower delta-T (difference between coolant temp and air temp), it will be less efficient at further removing thermal energy from the coolant. To get an intuitive sense of this, consider the following thought experiment -- you have a quart of water at 70'F and the assignment to heat it to 100'F in the least amount of time possible. Which will be the fastest method: by placing the water on a 100'F hot-plate, or by placing the water on a 200'F hot-plate? (If you chose the first option, then I'd suggest you stick with air-cooled engines...) The other advantage to running the rads in parallel is that such a setup will have approximately 1/4 the flow resistance of a series setup. |
Dave,
Good points, we used to do this with thermoelectric heat exchanger designs. Personally I'm just trying to adapt existing technology, not reinvent it. I need to get more details on the Boxster system...
Posted by: scott thacher May 31 2005, 12:42 PM
hello guys, i have been too busy to get on here for a few days and i missed this thread
to cool a v8 with out loosing the front trunk might be difficult but the 2 ways i might try it are
a 2 radiator set up... a gt oil cooler and an engine bay radiator under the engine lid, i would make the front one the primary or first one
or i would just lay radiator flat on the floor with a reverse scoop to pull air out under the car and a opening on the front to get air in
my opinion on doing to radiators would be to make the in series.. doing a parallel set up would work better but it would be very difficult to get it balanced
and in my car i have 2 fans on the radiator i can shut one off on the highway and the temp stays good, i might be able to shut both off but i only have control of one off them from inside the car
Posted by: Dr. Roger May 31 2005, 01:14 PM
A really clean cooling setup towards the rear would be ideal but I haven't seen anything I would like...
Anyone ever seen anything, keeping the radiator in th rear half of the car, that is well engineered??????????? Practical?
An oil cooler is definately going to be installed. That, again, is another subjective topic as to the best location/solution. I'm lovin' the oil cooling solution that Brant did.
Posted by: brant May 31 2005, 01:40 PM
Roger,
just my opinion....
but the rear idea really screws with the weight distribution and it also doesn't have the benefit of efficiency like a front cooler does....
frontal air being rammed through, just has to be more efficient I would think?
brant
Posted by: lapuwali May 31 2005, 02:19 PM
Tell that to Scott Thacher...
I think making a center mounted rad work (as Scott has) is the best of all possible setups. No long coolant lines, far fewer problems with bleeding, both trunks are retained, and the weight is still more or less centered within the wheelbase.
Making this work with a V8 would be a big challenge, not only due to lack of space in the engine bay for rads, but also the cooling requirements. A V6 would also have space problems.
A rotary MIGHT be able to do this, as long as you don't go gaga with tuning the engine (no turbo). You'd need more rad area than with the Soob, but from Scott's photos, there looks to be room for a much bigger rad than he used. With some clever ducting, you might even be able to exploit the chimney effect.
An inline four would have a lot more space to stick rads in the engine bay, perhaps running them more or less flat next to the engine with cool air ducted from below.
Posted by: brant May 31 2005, 02:50 PM
I wonder if scott has played with a set of corner balancing scales though...........
brant
Posted by: 914GT May 31 2005, 03:01 PM
What hasn't been brought up here to use alternative radiator designs is what can be done to reduce the heat losses from the engine. You can get by with a smaller or less-efficient cooling system if you can make the engine more efficient and get more waste heat out through the exhaust gases rather than the water jacket. Frictional losses can be lowered by using moly coatings on bearings and crank/rod journals and using roller lifters and rockers. Heat loss from combustion can be lowered by reflective barrier coatings on the piston, valves, and head. There are also some thermal dispersant coatings that could improve heat transfer from the block to surrounding air. A couple years ago I thought these coatings were mostly snake oil, but I had some of this done to my 350 and I think it made a big difference. Here are some http://www.techlinecoatings.com/TechnicalInformation.htm by Tech Line Coatings that discusses some of the things that can be done. A recent edition of Performance Engine magazine (engine rebuilder/machine shop trade mag) also had a good article on these coatings.
Posted by: Dr. Roger May 31 2005, 03:05 PM
| QUOTE (lapuwali @ May 31 2005, 12:19 PM) |
| Tell that to Scott Thacher... I think making a center mounted rad work (as Scott has) is the best of all possible setups. No long coolant lines, far fewer problems with bleeding, both trunks are retained, and the weight is still more or less centered within the wheelbase. Making this work with a V8 would be a big challenge, not only due to lack of space in the engine bay for rads, but also the cooling requirements. A V6 would also have space problems. A rotary MIGHT be able to do this, as long as you don't go gaga with tuning the engine (no turbo). You'd need more rad area than with the Soob, but from Scott's photos, there looks to be room for a much bigger rad than he used. With some clever ducting, you might even be able to exploit the chimney effect. An inline four would have a lot more space to stick rads in the engine bay, perhaps running them more or less flat next to the engine with cool air ducted from below. |
Do you have a link to his radiator pictures???
Im not afraid of "clever ducting". The racers do it all the time....
Posted by: scott thacher May 31 2005, 03:10 PM
| QUOTE (brant @ May 31 2005, 12:50 PM) |
| I wonder if scott has played with a set of corner balancing scales though........... brant |
no i have not, but why, the suby engine weighs less than a complete type 4. the radiator weighs about 20 lbs full of water, heck the whole cooling system only takes about 1.7 gallons. water which weighs about 8.5 lbs pergallon thats only 13 lbs or so of water.
the big difference in weight is no engine shelf, no cooling tin, etc. my engine bar weighs a bit less than a stock bar, my whole exhaust is probably 5 lbs ( if not 10) lighter than a stock type 4 HE and muffler set up
edit for roger: http://www.914world.com/bbs2/index.php?act=ST&f=2&t=24791&hl=radiator for a link to my pics of the radiator
Posted by: brant May 31 2005, 03:22 PM
Scott,
I think I should have look before I lept.
or read my comments before I hit send.
What I was getting at is balance.
not totals but balance.
even a -4 is rear heavy and needs all the weight moved forward that possibly can for a track car.
I guess I'm just thinking from the mindset that even If I could reduce the total weight, I would want to move as much of it as possible to the front of the car.
plus I played with 3 different oil cooler set ups on my old race car before I learned my lesson about having direct frontal air and clean cooler exit on an undersized and barely adequate cooler (needed maximum efficiency)
So I guess I'm saying that for maximum efficiency and optimum weight distribution, I still think frontal coolers have an advantage theoretically.
I hope that you don't take any offense to my comments, and I assure you that none was meant.
brant
Posted by: lapuwali May 31 2005, 03:53 PM
Theoretically, a front mounted cooler would have some advantage, if only because more high-pressure air is available. However, if the airflow is adequate to keep things cool, then it's adequate. No more airflow required, and any more is wasted.
As for balance, the 20-25lbs of rad and water in Scott's setup are roughly where the fan housing resides on the Type IV, or the front pair of cylinders are on a Six, so I'd be willing to bet the balance is just as good as it is with those engines. Theoretically speaking, keeping the weight centered near the middle of the wheelbase (which this would do), will help some aspects of handling.
Posted by: brant May 31 2005, 04:02 PM
| QUOTE (lapuwali @ May 31 2005, 02:53 PM) |
| Theoretically, a front mounted cooler would have some advantage, if only because more high-pressure air is available. However, if the airflow is adequate to keep things cool, then it's adequate. No more airflow required, and any more is wasted. As for balance, the 20-25lbs of rad and water in Scott's setup are roughly where the fan housing resides on the Type IV, or the front pair of cylinders are on a Six, so I'd be willing to bet the balance is just as good as it is with those engines. Theoretically speaking, keeping the weight centered near the middle of the wheelbase (which this would do), will help some aspects of handling. |
On a set of corner scales, you will find that putting a person in the cockpit is not forward enough to shift the front to rear percentages as much as optimum. (I think the foot well would be near optimum, for trying to shift polar weight)
the center of the car is around the drivers butt, and not the engine bay. I'm guessing that the stock jack point is rear of the car's balance point to compensate for the rear bias of a stock car.
I fully believe that scotts set up could be lighter than stock and thus his car has better rear balance than stock....... but wouldn't a car be even more balanced and lighter by using the smallest most effiecient size as possible and putting all of the weight forward for balance purposes?
that was more my point than anything negative about Scott's car
Posted by: Hydra May 31 2005, 04:25 PM
Here is a quick scetch of what i'll be doing for my eg33 conversion (flat 6 3.3 liters subaru engine). my drawing talents still need refining 
i don't know if it'll fit a V8. but it's just my idea, and if you guys think it won't work please chime in.
Nick
p.s./no highjack intended: Scott, i really really could need those scoop pics, if available, pleaaase (i've looked up all your porscharu posts and couldn't find any pic of it)
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Posted by: scott thacher May 31 2005, 04:36 PM
sorry for the high jack but i am going to post a few pics for nick here on the scoop
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Posted by: lapuwali May 31 2005, 04:37 PM
I think you'll find once you have all the bits in place that you won't be able to angle the rad all that much from vertical. The firewall angles back, and the trailing edge of the engine lid is about 2/3rds of the way back along the engine, not at the nose of the engine.
If anything, it would probably be easier to angle the rad back, opposite what you've drawn. However, I don't think you'd gain much airflow from this. Having a scoop below that directs air into an enclosed area on one side of the rad (using the scooped-out area of the firewall) will generate the pressure you need to force air through the rad. You can leave the other side of the rad open, dumping into the engine bay. However, more ducting that directed the air upwards would provide some amount of chimney effect, as the hot air would want to rise out of the duct, lowering the pressure in the duct, creating a stronger pressure differential across the rad.
Posted by: scott thacher May 31 2005, 04:37 PM
next
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Posted by: scott thacher May 31 2005, 04:38 PM
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Posted by: scott thacher May 31 2005, 04:47 PM
| QUOTE (lapuwali @ May 31 2005, 02:37 PM) |
| However, I don't think you'd gain much airflow from this. Having a scoop below that directs air into an enclosed area on one side of the rad (using the scooped-out area of the firewall) will generate the pressure you need to force air through the rad. You can leave the other side of the rad open, dumping into the engine bay. |
exactly what i did, i have the radiator vertical and i use the dish in the firewall to get the air as far up as possible. i think have the fans not running, just sitting there is a very large restriction, thats why i have them running all of the time.
nick ( hyrdra ) i think you would have more luck mounting the radiator on the engine lid, with the lid being a gt style lid. then use a scoop to send air in to the engine bay at speed. i dont thing unless you move the engine back ( renagade style ) you will have enough room.
Posted by: Hydra May 31 2005, 04:48 PM
Thanks for the pics scott 
I guess the radiator's angle in the drawing isn't accurate, but the top section is to force the air out the engine lid, since you would want the coolest air possible for the engine air intake....
edit: scott, i'll be using the subaru gearbox, which alone, will give me an extra 5 inches clearance, plus i'm fabricating mounts that will give even more room for the radiator.
Posted by: lapuwali May 31 2005, 04:59 PM
| QUOTE (Hydra @ May 31 2005, 02:48 PM) |
| Thanks for the pics scott I guess the radiator's angle in the drawing isn't accurate, but the top section is to force the air out the engine lid, since you would want the coolest air possible for the engine air intake.... |
True, but you can duct air to the airbox from the wheel well a lot easier than you can duct all of the rad air out of the engine bay.
Scott, now that you know the system works, you might try removing one of the fans and run it that way for a bit to see how the temps go. You might only need one fan at low speeds, and you've already determined you don't need both at speed.
Mounting the rad completely above the engine has some promise. Is there enough vertical clearance above the intake stuff for that?
Posted by: scott thacher May 31 2005, 05:06 PM
i did try to one fan at first and the temp would climb to about 200 if i was in stop and go traffic. unless it is night time and cool out i just run both fans. also there is about 4 inches of sapce to the ran tray so figure 7 to the lid it self.
nick you can only probably go back about 3 inches in my car till the engine would hit the rear trunk
Posted by: Hydra May 31 2005, 05:19 PM
| QUOTE |
| nick you can only probably go back about 3 inches in my car till the engine would hit the rear trunk |
i didn;t know that, but on the other hand, I forgot to mention i'll have a trick custom air intake that will sit lower in the engine with independent intake runners, and it'll most probably be fed through the back to avoid getting hot air sucked into the engine. i'm still working on it...
Posted by: neo914-6 May 31 2005, 07:40 PM
| QUOTE (Hydra @ May 31 2005, 02:25 PM) |
| Here is a quick scetch of what i'll be doing for my eg33 conversion (flat 6 3.3 liters subaru engine). my drawing talents still need refining i don't know if it'll fit a V8. but it's just my idea, and if you guys think it won't work please chime in. Nick p.s./no highjack intended: Scott, i really really could need those scoop pics, if available, pleaaase (i've looked up all your porscharu posts and couldn't find any pic of it) |
Nick,
Use grid paper and measure the car to draw a scaled layout. If you already have the radiator, it's a matter of trial fitting and using card board to mock it up.
I've posted prior about the radiator in the engine lid, it may work but I'm still concerned it would be the highest point for water fill and air entrapment.
BTW, did you know "914helo" is converting to 3.3 SVX also?
Posted by: scott thacher May 31 2005, 08:47 PM
| QUOTE (Neo914 @ May 31 2005, 05:40 PM) |
| I've posted prior about the radiator in the engine lid, it may work but I'm still concerned it would be the highest point for water fill and air entrapment. BTW, did you know "914helo" is converting to 3.3 SVX also? |
well as far as air intrapment ... you want the air to go to the high point which is where you put your pressure cap as long as it is not in the engine a small air pocket is okay it will work its way out.
the suby 3.3 is the engine i wanted in the begining, it can hit 300 hp NA easily and i saw one on the web that was turboed at 14 psi and was doing 550 hp
Posted by: Dr. Roger May 31 2005, 11:11 PM
I'm really liking this idea. Kinda like Scott's solution but different. 
These fans are the right size and pullers, and are reversable.
What do you guys think about two twin-pass aluminum radiators. Maybe three cored. One on each side and are shrouded. Perhaps some "helper" shrouding from below.
This would also allow room for the air filter/intake system.
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Posted by: Dr. Roger May 31 2005, 11:14 PM
Fan depth...
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Posted by: Reiche May 31 2005, 11:23 PM
| QUOTE (Hydra @ May 31 2005, 03:48 PM) |
| the top section is to force the air out the engine lid, since you would want the coolest air possible for the engine air intake |
I would think the coolest air would come from the top side of the car, not off the road surface. However, it can work, as Scott showed, and as long as it cools sufficiently, that is good enough.
I am more concerned that you will be fighting the natural airflow around the car instead of using it. Some of the air coming off the back of the roof creates an eddy, and flows forward to the engine lid area. That's why the lid curves up slightly higher than the trunk lid just behind it, to catch that airflow. Even with an underneath scoop like Scott's, I would think you will need some powerful fans to overcome that, especially at high speed.
Posted by: redshift May 31 2005, 11:27 PM
With engine tin in, the rear ends want to fly around 120, with a little surface wind...
hmm...
I dunno.
M
Posted by: Dr. Roger May 31 2005, 11:51 PM
Maybe I'm off but I thought there was a vacuum behind the cockpit which would lend to the sucking effect on the radiators. No?
Posted by: Mueller May 31 2005, 11:58 PM
roger, your carb is going to be hitting the engine lid, or be pretty darn close to it with that high rise manifold....
a few people have installed oil coolers in that location and most have removed them and installed them in a better location
Posted by: Reiche May 31 2005, 11:59 PM
| QUOTE (rogergrubb @ May 31 2005, 10:51 PM) |
| Maybe I'm off but I thought there was a vacuum behind the cockpit which would lend to the sucking effect on the radiators. No? |
It's actually a sewing machine...
You could be right, but it would be strange to put the engine intake there if that were so.
I don't know how the air would flow without the engine tin and lower air diverters in place. Maybe that would change everything...
Posted by: scott thacher Jun 1 2005, 09:58 AM
okay as we all know i dont have engine tin, and i have a trashed front seal on the engine lid... so for the wcc i put a peice of electric tape on the seal to hid it a little. well about half way up the east coast on the way home the tape came loose to about the middle of the car. so i got to watch a peice of tape flap on the the engine lid for 400 miles. the tape was secured at the rear window.
so what the tape did was it was plastered to the front part of the engine lid ( solid ) and the rear part flapped in a circlular motion, it was not blown of off the lid nor was it held down.
so i would say it is a pretty good airflow area that really did not blow in or out, but i would say that the turbulance would be slightly pulling air out of the engine bay
Posted by: flat_iv Jun 2 2006, 09:29 PM
Roger,
If you are still looking at 2 radiator up front, look at the 95 Dodge Neon (5sp, no air. The radiator is approx 13 x 13 x 1 1/4 thick. I am planning using the 2 radiator set up in my 74 Ghia.
Richard
Posted by: roadster fan Jun 3 2006, 03:17 AM
I know I am coming into this discussion a little late, but how about this.....
The Boxster S models came with a third radiator set in the middle of the front bumper between the two front wheel well rads. What if you used 1 or 2 long skinny radiators (jeep cherokee?) mounted inside a fiberglass front bumper (like fiberwerks for example). The rads could be mounted similiar to a turbo intercooler (ie way out front). Air could be ducted to the wheel wells or underneath GT style. This would allow you to maintain all/most of the front trunk.
If you supplemented this approach with finned tubing in the rockers or a small rad in the engine lid it may work. 
Also, the Boxster rads are plumbed in parallel to maximize efficiency using two aluminum tubes with Y's (W's for S) in the front. I have pics but can't find right now will try to post tomorrow.
Posted by: J P Stein Jun 3 2006, 08:11 AM
The job of any radiator (including oil coolers) is to keep an engine within its proper opperational temperature. "Other" considerations lead to the tail wagging the dog.
An excess of cooling capacity is gud.....that can be modulated.
A lack thereof and you are fucked. At best, a redo is in order, at worst, your motor suffers damage then you get to redo that also.
Do it once, do it right.....then consider the peripheral BS. With a 914/SBC, after the cooling capacity is settled, I would more concerned with venting the heat without structuraly weakening the chassis....which is the tail & which is the dog here?
Posted by: marks914 Jun 4 2006, 05:54 AM
Good luck!
I too thought of doing something like this but abandoned it after talking to some thermodynamic engineers at work when I was doing some work in our wind tunnel a few years ago.
When cooling it comes down to 2 things, air flow and heat transfer.
I ended upgoing with the rad in front.
Mark
Posted by: Two914s Jun 4 2006, 03:42 PM
I have been working on an aluminum fuel injected V8 conversion for some time. I have it driveable now, but with no radiators. The car weighs 1878 lbs on the corner scales right now. The inlet and outlet of the engine are just connected together with an in-line radiator cap. I can drive it for about 3 minutes before needing to shut it down. Fun 3 minutes!
I have been working on a duel inside-the-engine-bay radiator setup this spring.
I am committed to not cutting either trunk at all. I am willing to do some major modification to the engine lid, because that can always be changed. Engine lids are cheap. I want the powerplant to be able to change between chassis without more cutting.
My latest idea is to use a Subaru WRX top mount intercooler as a radiator. They are very often for sale on Ebay and are beautiful. They, of course, are made for air-to-air heat transfer, but they look like they would work for water. They are thick, which is just what we want. Lots of fin area without being big in external dimensions. I plan to modify them and have the TIG welding facilities to do so.
They are a good size to mount two of them under the engine lids with PULLER fans. It is much better to pull the air through a heat exchanger because the air is less turbulent that way. Have you even noticed that you can feel a fan blowing on one blown side but not sucking side? The laminar flow across the fins is what you want.
I certainly agree that it is better to plumb them in parallel and not series. You want to slow the water down as it goes through the exchanger. Pumping it through too fast doesnt help. The parallel radiators help with that.
There are several companies that make the finned tubing that was mentioned earlier. I would try to use that if using a small radiator up front..
Basically an engine only converts 1/3 of its gasoline energy into horsepower. So if you have a 300 horsepower engine, the fuel going into the intake manifold has the equivalent of 900 horsepower!! 300 horsepower is converted into heat that must be disipated through the block and radiators and oil coolers. 300 horsepower goes right out the tailpipe in the form of hot exhaust gas, and then 300 goes out through the flywheel and into the transmission. Yikes!
But remember, you dont drive around at 300 horsepower very long, especially in a 914. I would guess that it takes about 25 horsepower to cruise at 60 miles and hour in a 914. So the radiators must only dissapate 25 horsepower under those circumstances.
So, I am going to try two radiators in the engine compartment and then mount an OIL cooler up front in the GT style...maybe with a fiberglass bumper with the GT opening. Any heat that I get rid of with the oil cooler with subtract from the amount of heat that the radiators must transfer to the air. I may modify the engine lid extensively as this part is easy to obtain another.
Good OIL cooling is one major reason that the 911 and 914 air cooled engines work. These engines are both air AND oil cooled.
You can help the situation as well with the coatings mentioned before on the pistons and cylinder heads. That will blow more of the heat out the tailpipe and into flywheel horsepower, and less into the block which must be dissipated through the radiators and oil coolers. Retarding the timing slightly, running the engine a little rich, using water or methanol injection would also help, but those things are against the whole point...
If the radiators are under the engine lid, you can always have your significant other dump some of their bottled water over the rear window if you get caught with some overheating. This is passenger-assisted evaporative cooling.
OK, I have said enough....
Posted by: Dr. Roger Jun 4 2006, 04:08 PM
yep,
i'm aware of the Y but wasn't aware of the W setup for the vasser cooled P cars.
Porsche, once again, already does what i'll probably end up doing for mine. =-)
i'd like to see your end product pics with tubing specs, the intercooler functioning, and some performance statistics when your done.
actually many people on this site would be interested in your outcome as i rekkun there's a bunch of fabricators/do-it-yourselfers around these parts....
thanks for you input! 
Posted by: drive-ability Jun 4 2006, 05:30 PM
I love to see all the innovation going on. I too like the idea of having a trunk as a practical matter. I am sure there is a way to consolidate a system using available space. I will say it was over 90 degrees today in Ca. and I drove around in stop and go traffic sprinting from stop sign to stop sign and never saw 195 degrees. In fact if I were to just over-ride my thermo switch the car would have run in the 160 range. I would just hate to have a car that runs on the hot side, I am now looking into an oil cooler as my coolant temps are low my oil can get hot.
I think you guys are on to something splitting up the radiators keep us informed.
Posted by: TonyAKAVW Jun 4 2006, 07:20 PM
In my Subaru conversion thread I go into some detail about how I am going to pull air into the engine bay from the top and suck it out the bottom with the assistance of a venturi generator under the car. I'm guessing that this same generator would work well for other engine bay mounted radiator setups. It will be at least a couple months before I get the engine in the car and can start testing, but I'm planning on building up a mold for making fiberglass panels for this purpose. If others are interested in this, it would give me more motivation to spend the time building up the rather large mold.
-Tony
Posted by: Rand Jun 4 2006, 07:21 PM
I had posted a question like this in January (in thread http://www.914world.com/bbs2/index.php?showtopic=44856&hl=modern).
I thought it would be feasible to put ducts between doors and rear fenders (just like most modern mid-engine cars) to pull air in (naca style if not flared much), use a sealed duct/shroud system to force air through radiators positioned next to the v8 block (surprising amount of room there on the conversions) and out through the bottom or rear (again with well-designed ducting I think you could get a lot of good flow through the rad - naturally at speed, or assisted with fans when needed).
Keep pushing on this Roger. I know it can be done. Borrow from what's been done and put some ingenuity into the rest.
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Posted by: banksyinoz Jun 5 2006, 04:28 AM
this maybe a brainless idea butr here i go
just thought as i have not done any research as yet ,
would it be possible ( or even wise ) to allow air to flow ( force at speed ) through the sills where the original equiptment once blew hot air for the heater,
this would allow engine compartment radiators greater air flow,
i have removed the heater/ fan box from below the screen and was considering using this opening for this purpose as well as a similar scoop as scott, i have 2x dual pass radiators to mount infront of my ej20t & auto
pplease give a 
if this is a no go
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