briannutter

Extreme budget here for a c-4 with unconventional radiator location. Factory junk radiator is about 29x18 for a total of 522 square inches. Looking at 16 x 31 and 19 x 31 griffen aluminum 3" dual core for about $195 from summit. Ducting, shroud, and fans will be good. How small have you been able to go without overheating. Please no "as big as you can make it" and "my stock one works" replies...I need some advice from someone who's pushed it a bit. Thanks for your help!

Also, Anybody ever tried bar and plate intercoolers or other types of cores?

davidfarmer

Brian, I don't have any heavy science for you, but in my experience, a 3-core replacement in more-or-less OEM sizes will have a difficult time keeping a 500hp engine cool, yet alone a 600hp engine.

I think you are going to need more size, and extreme airflow through it...thinking front-breather with louvered hood for extraction.

Along these lines, I'm extremely anxious to see how the new ZR1 handles heat. The Z06 cooling is marginal, and another 100hp, especially under boost, is going to be hard to chill.

Good luck.

0Louis @ LG Motorsports

Theres more to it than just size. I would go with a double pass regardless. Airflow and air management is more important than pure size.

ProgGod

Also depends on the weather where you plan to track. Us arizonians have alot more problem then michiginians

briannutter

Thanks for the help guys!

0Randy@DRM

Kinda of the rule of thumb is the opening has to be 1/3 the size of the core. The C4 and C5 had this rule in place. The C6 doesn't but I think the design engneers had there way.

Where is the radiator anyways???

Randy

BrianCunningham

How unconventional?

Do you plan on venting the hood? Good for both cooling and downforce.

If so, then check this out:
http://s64.photobucket.com/albums/h167/Tazio_Nuvolari

briannutter

Thanks for the grill opening number Randy...that's very handy.

I spoke with Griffen and they have a nice dual-pass with those dimensions and they think it will support the power.

As for the "unconventional" radiator location...I have to explain what happened. This a little like being in a confessional...and you'll see why in a minute.

I spent a day in the Aerodyn 2 windtunnel in North Carolina with a buddies car on the way down to the Maxton Mile a couple months ago. As an armchair aerodynamicist, it was an incredible experience. I saw things that shouldn't have occurred according to popular wisdom. When I got back, I started having visions of the original 60's grandsport convertible and the new Lotus 211. Then one weekend, I sent my wife off on and errand and proceeded to chop the top off my '94. The windshield, a pillar, b pillar, rear glass, and targa top.....all gone. Then I removed the rear inner-trunk fiberglass for good measure. Don't worry, the car was a rat to start with.

The money I saved from buying plexiglass windows bought aluminum sheet, bracing, a bead roller, a tubing notcher, sawzall blades, quarter turn fasteners, and a 6 pack of beer. I'm not finished yet, but the new aluminum sheet deck will cover the perimeter of the opening (wish I'd started with a convertible). The only thing above the body line now is my rollcage and my head.

I estimate about 160 lbs of weight savings off the top of the car, maybe 6 square feet of frontal area...and the wake it produces. To get rid of the grill opening and seal up the front end (and reduce the polar moment of inertia)-I considered putting two small radiators (wired in series) behind the front wheels. Then, taking inspiration from Rick Gifford's (baldturbofreak in the forced induction forum) Big Red , I decided to go rear mount on the radiator.

For those who've never cut your the inner trunk away, there is 36" of space between the frame rails. This is enough room for a longitudenally mounted fuel cell and a 16" wide radiator. The leading edge of the radiator will be at trunk floor height starting roughly 15" behind the drivers seat. It will lay back at 60 degrees..with the top most portion under the rear deck. The duct serving it (now 1/3 the core area-thanks Randy) has no frontal area. I'm hoping for a 15 degree angle of divergence down from the body line. This opening has suction from the fans and should serve to suck down the wake that my head and seat creates...hopefully re-attaching the air to the deck before hitting the rear spoiler. The duct leaving the radiator will go to a hole in the rear bumper (roughly 1/3 the area of the core). This should pump air into the negative pressure area and move the wake further backward. If all goes according to plan it will reduce CD and lift...especially when used in conjunction with a home-made diffuser. It also moves the car's CG back (and lower since I've moved the fuel tank) and will balance it better. Weights over the rear wheels-so it will help traction and braking. If I get a front end from Bob Finlayson some day, I'm hoping to get the cd into the low 20's and the resulting drop in CDA will help as well. For now, I'm thinking about a sheetmetal airdamn and some sort of splittler.

A trip to the tunnel may happen again...if my wife doesn't send me to the looney bin first.

VetteDrmr

I'd have to go to the rulebook, but I think these mods have bumped you out of SCCA Stock!

What a project! Sounds similar to DF's Corvetteamino.

Have fun with it!
Mike

mwvettec5

PICTURES !!!

FastZR1

Yea... post some pictures of this project. I have an idea what you have going there from your description, but pictures are worth a thousand words.

AU N EGL

Brian. that thing is

briannutter

Thanks for the support fellas. This thing is about as anti-goldchain as it gets... I'm dreading the first time I take it out and some idiot talks trash about ruining it's future collectibility Maybe I'll laminate the tank sticker to the panels or something to show him how much I care

I will post photos, but it will be a few weeks. It looks pretty scary at the moment...even to me. I've got some events to attend to for Wiseco over the next few weekends. I'm ordering the Griffen on Wed. though and will get to work.

for now: http://www.caradvice.com.au/wp-conte...en_entry01.jpg

http://www.corvetteblog.com/GrandSportRear.jpg

0Bobby @ LG Motorsports

A2 is cheap for the first few hours for a first timer

Slalom4me

Some theory

• 1 HP/hr = 2,546.4 Btu/hr (= 42.44 Btu/min)
  .
  Therefore: 600 HP = 1,527,840 Btu/hr (25,464 BTU/min)
  .
• As a rule of thumb, 25%-35% of the fuel energy produced
  passes to the coolent.
  .
  Therefore: Required coolent heat exchanger capacity
  = 35% x 1,527,840 BTU/hr = 534,744 Btu/hr or 8,912 Btu/min
  
  

To validate the reasonableness of this, consider a real life example.

The FORD GT's supercharged 5.4L engine is rated at 550 HP &
500 LBS/FT. Cooling design parameters called for a max outlet temp
of 245°F at 200 MPH at 110°F ambiant and 0.075 lbm/ft³ air density.

Using the same approach as above:

• 1 HP/hr = 2,546.4 Btu/hr (= 42.44 Btu/min)
  .
  Therefore: 550 HP = 140,0520 Btu/hr (=23,342 Btu/min)
  .
• Of this total Btu produced, assume 35% is sent into the coolent
  .
  Therefore: Required coolent heat exchanger capacity
  = 35% x 140,0520 Btu/hr = 490,182 Btu/hr or 8,169.7 Btu/min.
  
  This value of 8,169.7 Btu/min compares closely with the value of
  8,000 Btu/min that FORD & Roush used in their design study for the GT.
  
  SAE #2004-01-1257 - "2005 Ford GT- Maintaining Your Cool at 200 MPH"

The GT's aluminum radiator core has the following dimensions
Incidently, the GT cooling study also determines that roughly 12%
of the total fuel energy passses to the oil cooler, this meant another
2,800 Btu/min of heat load to be addressed. In addition to the
coolent and oil exchangers, the GT also has an intercooler and an
A/C condensor to provide for. Total design heat load: 13,400 Btu/min.

Also, the authors write about establishing minimum coolent flow through
the engine at 100 g/min. This supports arguements I've made here in
the past against using 55 g/min electric pumps for track cars.

Regarding the plan to mount the cooling package for a 600 HP engine in
the rear of a C4. My vote is that succeeding at this will prove to be
a sorely vexing challenge. Any changes made to accomplish the plan
ought not be irreversible in case it proves necessary to reposition the
cooling package to the front of the vehicle.

.

73-84 IMSA Widebody

Wew...........thank goodness we have engineers

We run 650+ hp BB and are running an alumunum dual pass, core is 27.5X16. Front body in vented to engine compartment with dual electric spals.
we are 8/10 ( under 120 ) racers and have not had overheating problems.

What series/class are you thinking of running?

briannutter

NOW,we're really getting into the nitty gritty....thanks slalom4me... I should have remembered to look at the SAE papers for info. I have papers on a couple other subjects. Love 'em.

I will end up having a bit more area than the ford radiator, so that bodes well. I also have guestimated 20 feet of thinwall aluminum tubing area and the resulting extra coolant capacity to offset btu spikes. I should also have some very high speed airflow considering the negative pressure behind the car will be pulling air through. Although I doubt this negative pressure is greater than the positive pressure seen at conventional grill openings. If you have a chance, do a search under "cfd flow visualization racing" in google images. excellent stuff. I've also looked at Porsche Boxter, Cayman, 911t, Ferrari Modena and Lambo cooling systems. They move their CG forward by running a small pair of radiators in front. Porsches do it with two small ones in front of each of the front wheels. Funny how that works.

Thanks Imsa, that's excellent info as well. Most track racers aren't using full throttle all the time around the track...except superspeedway guys. The ford GT engineers had to plan on the car running at the Autobahn for extended periods...I will not be so lucky unless I run the Silver State classic. I've been keeping it wrapped around the rules for various venues to maintain legality. Scca IT, Nasa ST1, ECTA, and Bonneville are all potential sites exploration. Will I be lumped in with $200k tube frame race cars, yes. Will I win "in class"?-probably not. Will I be faster than I would have been with a more conventional car?--Definitely!