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Thread: The hydrodynamic conundrum

  1. #1
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    The hydrodynamic conundrum

    As some of you know, I added a second engine in the back of my shadow. I'm having some rear engine cooling system problems when on the free way. Temperatures are close to 230, and I would like to lower that about 15 degrees.

    I know the issue is airflow through the radiator, and I know cutting up the body and adding scoops and the like will help direct ambient air to the radiator, but I don't want to add scoops and cut the body to take away any of the stock appearance.

    So I thought I could add a small radiator to the upper rad hose in parallel, to help get rid of that little bit more heat. I found a small rad from a motorcycle that uses 3/4" inlet and outlet and has a rad cap so it can be bled fairly easily. It has a 10x10 cooling surface area and that's going to fill up about all the space I have available. It will draw fresh air from the right rear wheel well and it has a small fan to help it cool.

    Now onto the tricky part, I need to know what you think is the best way to get enough coolant flow through the motorcycle rad without restricting the water pump too much.



    These are 5 ideas how to plumb it in. In all pictures, the upper rad pipe is 1.5" OD and the radiator inlet and outlet are 3/4" ID.

    The reason for 1.5" rad hoses are because they're made from exhaust pipes and that's the smallest diameter the exhaust shop had. I think it necks down to 1.25" at the thermostat housing, water pump inlet and the radiator inlet and outlet.

    Picture 1 is pretty straight forward, but I don;t know it would direct enough coolant to the rad.
    Picture 2 is similar, but adds the motorcycle rad hoses into the coolant path,
    Picture 3 is the same as 2, but changes the angle of the cut on the tubes.
    Picture 4 is like 3, but adds a washer acting as a restrictor to help direct more coolant to the motorcycle rad.
    Picture 5 is similar to 4, but doesn't have the motorcycle hoses in the coolant flow. It's also easier to weld straight on.

    So what do you think??

  2. #2
    Supporting Member Turbo Mopar Contributor
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    Re: The hydrodynamic conundrum

    Someday I am going to have to drop by and see this beast!

    Diagrams 1-3 have a very small pressure drop from inlet to outlet, therefore there will be little flow through the motorcycle rad.
    Diagrams 4 and 5 you have increased the pressure drop which will increase the flow through the motorcycle rad but decrease the over all coolant flow.

    I don't believe 1-3 will help at all, 4 and 5 will be tough to dial in unless you use a variable restrictor rather than a washer. Perhaps a ball valve?

    In your setup, is it possible to incorporate countercurrent cooling design? I use it in my day job.....Just a thought.
    https://en.wikipedia.org/wiki/Countercurrent_exchange
    Last edited by chromguy; 07-24-2016 at 02:20 PM.
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
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  3. #3
    Supporting Member Turbo Mopar Contributor 2.216VTurbo's Avatar
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    Re: The hydrodynamic conundrum

    Would a 4th cylinder head coolant mod that A Cannell sells divert enough flow to supply your 3rd radiator?

    AJ (no More Alan) 84 Rampage RT TIII/568 Quaife 87 GLHS dealer optioned Red 16V Masi/568/Quaife
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  4. #4
    boostaholic bfarroo's Avatar
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    Re: The hydrodynamic conundrum

    How about using the heater core feed/return for the suplimental radiator?

  5. #5
    Hybrid booster
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    Re: The hydrodynamic conundrum

    ^ I was going to suggest this. Run it off the nipple on the water pump for the heater core, and the return at the thermostat neck. Or enclose and tuck a second radiator behind the engine, add a big heat shield around it, and plumb air from the wheel wells up into the cabin. Have the air vent under the car via ducts where the spare tire would sit. I would think the pressure differential would pull the air through the system rather quickly. Add some sick NACA ducts for flair.

  6. #6
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    Re: The hydrodynamic conundrum

    I can't find any pics of what you have right now for cooling. The FB links don't work, says content is unavailable.

    If you're running two radiators, one being in the rear of the car, have you considered running a larger & thicker radiator up front and running coolant lines to the back?
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  7. #7
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    Re: The hydrodynamic conundrum

    I'd say run the thing in series just the way it is. Necking down to 3/4" and the internal restriction of the radiator itself should be enough.

  8. #8
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    Re: The hydrodynamic conundrum

    Thanks for the replies!!

    First off, sorry, I have no idea why pictures from FB aren't working. I have it set to public.

    Trying to do this in order, Chromguy, great idea with a ball valve, I did the math and the area of the original pipe (1.76"2) minus the area of the motorcycle rad inlet and outlet (.441"2) equals, 1.319"2 so 1.25" pipe is 1.226"2, so it's pretty close as a starting point. While the rad pipe is off, I'm considering adding some fins to assist even a little.

    Alan, Benji, I have already added a heater core from a tractor inline with the pipes that should go to the heater core. This one could use a better fan, and it will receive one from another motorcycle. Ironically, a honda shadow. Better ducting will be added if there's room.

    Turismo lover, A second radiator couldn't fit. There's much less room available than you may think. Add in ducting and also exhausting the hot air, and it's even less possible. I can't just add 40 fans because I have 1 alternator on the front engine only and I can't max it out and expect a decent life expectancy. The way how I did this, a second alternator simply wouldn't fit, but it was part of the original plan.

    86 Shelby. Here's what I have.



    The space behind the rad is almost nothing as the exhaust is there.

    Also, there's a plate that sits about 3 inches above the rad in the picture. This is where the fuel tank is mounted. It's ducted to pretty much dump the hot air behind the rad, past the exhaust pipe.

    You can't see the heater core that plumbs off the head and into the water pump, but you can sort of see the available space in the right rear wheel well to get some cooler air to help with the motorcycle radiator.

    A good friend of mine has suggested teeing the front and rear cooling systems together. I asked him to draw out what he means and he hasn't got back to me. If you have a design in mind, please put pencil to paper and post it up for me. I just might try it, but the time to make it happen would set me back a long time.

    Reaper1, I thought that would be too much of a restriction forcing a decent volume of coolant into that tiny rad. I may end up doing something like that , but more likely accomplishing that using the ball valve Chromguy suggested.

    Any other ideas or drawings, PLEASE post them up!!! You guys are such a great bunch.

  9. #9
    Supporting Member Turbo Mopar Contributor 2.216VTurbo's Avatar
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    Re: The hydrodynamic conundrum

    I had seen some earlier mock up pics of your build somewhere shadow but I don't think I knew that it was up and running now. Since I don't go on FB anymore (AKA the Marriage Destroyer) can you put a few current pics here? I don't think it was as runner in that last pics as there is no throttle cable or intake piping evident.

    AJ (no More Alan) 84 Rampage RT TIII/568 Quaife 87 GLHS dealer optioned Red 16V Masi/568/Quaife
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  10. #10
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    Re: The hydrodynamic conundrum

    I'm real curious how well #3 would work with the opposing 45 degree deals. I'm sure something would get through there, but what will the gauge say..
    MinivanRider

  11. #11
    Supporting Member Turbo Mopar Contributor zin's Avatar
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    Re: The hydrodynamic conundrum

    Jamie, I'm going to suggest a "none of the above" approach, mostly because the the plumbing will be SO much simpler and more reliable.

    My suggestion is to use just one large radiator, modify the end-tanks to have two inlet/outlets per side, and add a divider between them. This gives you effectively two radiators in the stock location so air flow will not be an issue, will save weight by eliminating the extra radiator as well as simplifying the plumbing.

    The only thing that's even mildly challenging will be running the piping from the back to the front, which really shouldn't be all that difficult, Fieros did it that way (but with just one engine!).

    What do you think?

    Mike
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  12. #12
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    Re: The hydrodynamic conundrum

    Alan, it's been running for a little over a year. I took it to work last year three times and although there weren't any breakdowns, there was need for further refinements. Rear bump steer, better insulation and noise reduction, passing an emission test last October, and as always, the rear engine getting too hot. I should get more pictures up shortly.

    Mike, I don't think it's as difficult as it may seem to do a dual front radiator. Pipes are just pipes after all, right? This is even the idea Jackson mentioned to me for his plans to cool his dual engine project, and I thought, the same thing as I do now. That's this. I've never seen a single radiator made for that purpose, with basically two rads in one. It's simpler, for sure, but if I have to make the rad myself, from 2 existing rads, I don't think I've seen radiators available that would be so wide and short (assuming cross flow design.) Custom made rad from a company like griffin, maybe?

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    Super Moderator Turbo Mopar Staff contraption22's Avatar
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    Re: The hydrodynamic conundrum

    DO you have oil coolers on the engines? A nice sized oil cooler can really bring down the coolant temperature as well.

    - - - Updated - - -

    Quote Originally Posted by shadow88 View Post
    Alan, it's been running for a little over a year. I took it to work last year three times and although there weren't any breakdowns, there was need for further refinements. Rear bump steer, better insulation and noise reduction, passing an emission test last October, and as always, the rear engine getting too hot. I should get more pictures up shortly.

    Mike, I don't think it's as difficult as it may seem to do a dual front radiator. Pipes are just pipes after all, right? This is even the idea Jackson mentioned to me for his plans to cool his dual engine project, and I thought, the same thing as I do now. That's this. I've never seen a single radiator made for that purpose, with basically two rads in one. It's simpler, for sure, but if I have to make the rad myself, from 2 existing rads, I don't think I've seen radiators available that would be so wide and short (assuming cross flow design.) Custom made rad from a company like griffin, maybe?

    Even simpler would be one giant custom radiator with plumbing for two engines.
    Mike Marra
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  14. #14
    Supporting Member Turbo Mopar Contributor zin's Avatar
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    Re: The hydrodynamic conundrum

    Quote Originally Posted by shadow88 View Post
    Mike, I don't think it's as difficult as it may seem to do a dual front radiator. Pipes are just pipes after all, right? This is even the idea Jackson mentioned to me for his plans to cool his dual engine project, and I thought, the same thing as I do now. That's this. I've never seen a single radiator made for that purpose, with basically two rads in one. It's simpler, for sure, but if I have to make the rad myself, from 2 existing rads, I don't think I've seen radiators available that would be so wide and short (assuming cross flow design.) Custom made rad from a company like griffin, maybe?
    My plan would be to get the heaviest duty stock radiator (with metal tanks) and have a radiator shop braze a divider into the tank breaking it into two tanks (top and bottom) and add an additional "nipple" (for lack of a better term) on each side, giving you two flow paths with one core. With proper fans, I think you'd be in good shape, as higher velocity air will make a small radiator act bigger, which is how F1 cars are able to get away with what seem like tiny radiators.

    At least that's where I'd start. If it didn't get the job done, a custom radiator would be the next step.

    Mike
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  15. #15
    Super Moderator Turbo Mopar Staff contraption22's Avatar
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    Re: The hydrodynamic conundrum

    I don't see the need to devide the tanks. But I also cannot see any stock type radiator being able to cool two engines.
    Mike Marra
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  16. #16
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    Re: The hydrodynamic conundrum

    there is a space to add an extra radiator in most of our cars - except omni's , mini vans and K cars

    lay it flat in the nose of the car in front of the rad cradle

    first you have to get past the standard thought the rad should be upright as bottom feeder rads actually cool better than front feeder rads
    - because of the air pressure under the nose of the car

    (this I learned from reading a 20 year subscription of ACJ automotive cooling journal = from NARSA national automotive service assn- dad was a member)

    granted if the bottom of the nose in enclosed like most of our cars it will need a big hole cut into it and a nice deflector along the bottom of the rad cradle to help deflect air up into the secondary rad

    that plus the reserve volume of coolant in the plumbing run from front to back should add considerably to your car's cooling

    this is how I've intended to add the radiator for an air to water intercooler when I build my charger so as not to block the rad as it is

  17. #17
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    Re: The hydrodynamic conundrum

    A double pass, single radiator (at least double row, triple would be better) with a good fan and proper ducting would probably solve this issue.

    As Mr. Marra pointed out...oil coolers will also help a bit. Again, proper ducting is needed here.

  18. #18
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    Re: The hydrodynamic conundrum

    Mr, Marra. The rear engine has an oil cooler from an srt-4 or PT GT, using the oil filter as part of the cooler.
    A giant rad to handle both engines sounds good on paper, but fitting it is another story. What's in the front right now is a TBI rad for an 88 shadow. It takes up most of the space available.

    Dr, Johny, There's currently a big intercooler sitting in front of the radiator that would need to be removed in order for another radiator to fit in that spot. Then, the "exhaust" from the forward radiator would really hurt the cooling capability of the second radiator, wouldn't you think? I know what you mean regarding top breathing and bottom breathing cooling systems, and I feel these cars are top breathing. I also don't see much extra space to lie a radiator on much of an angle before resting on the bumper structure. Unless it was placed well out front where the intercooler currently is.

    Mr. Marra. I have to agree that under racing conditions, there simply won't be enough cooling system surface area to keep 2 engines cool.

    Reaper. Do you mean the dual pass rad for the rear engine? If so, I can tell you it's a mishimoto aluminum rad for a 95-99 neon and unless you're on the free way, it works just fine. Normal around town temperatures is usually 180-190.

    Yesterday, I purchased a 1.5" ball valve rated to 360F and 150 psi, so that shouldn't cause any issues after installation. I'm kinda going ahead with the another radiator idea to help take the bite off.

    IF I end up running the cooling system to the front, I'll need to see some drawings, sketches or ideas to help me design it before getting started.

  19. #19
    Garrett booster
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    Re: The hydrodynamic conundrum

    seems the issue could be fixed with ducting.. similar to the formula 1 solutions..

    looks like the fans are circulating hot air off the turbo to the radiator, and the key is to get cold air to the fan -- don't care about the exhaust

    what about creating a fan shroud that connects to duct to pull air infront/under the rear engine... i'd probably move the fan's to the other side of the radiator too..

  20. #20
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    Re: The hydrodynamic conundrum

    The fans are pulling air up. I guess I didn't specify that, but they're pulling ambient air from below

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