Dual Radiators

I have been thinking about running dual motorcycle radiators in the front of my Ghia. I have approx. 15" x 15" x 10" deep of room in each front fender well. For air flow I was going to remove the front turnsignals and use the front nostrils for air flow. There is a ton of information about aircraft and suby engines and they are using dual radiators. The main issue that I have is most motorcycle radiators have 7/8" to 1" water inlets and outlets and the Suby has 1 1/2" inlet and outlet. Every site that I have read said the the Suby runs fine with 7/8" radiator line. Which seems very small to me. But I realize that the radiators are closer to their engines that in a VW. Someone talk me out of this madness.

Richard

I would think that aircraft operate in an environment with more airflow and cooler air than a motor car. That may be a factor to think about as well.

I do agree with you with airplanes having a higher pressure. I think that I can get better air flow in and out from the fender wells than in the spare tire well. I am still concerned that if you use 1 1/2" tubing front to rear and that the 2nd radiator would open up from 1" to 1 1/2". Would there be enough pressure to fill the 1 1/2" line back to the engine? The water outlet sits 23" from the ground. The top of the radiators would sit approx. 28-30" from the ground. I was still planning on using a burp tank in the engine compartment fed from the heater lines. I still have to so some research on wether it is better to bleed the system in the rear or front where the rad's are becaues the rad's will be at the highest point.

Richard

That is a pretty big reduction in tube size. It could cause all sorts of unforseen issues. You are already complicating the situation by have the water run to the front (which is the best place for the rads 👍 ). Reducing the water lines to that size means the flow inside them needs to more than double. That will make the pump work harder than it already is, and it's already pushing close to double the amount of coolent around. I'm also guessing, and it's just a guess, that the smaller the pipe, the harder it is to bleed all the air out of it. I really think you are better off leaving as much of the setup as close to standard as possible.

Also, why dual radiators? A single one will work fine provided the radiator is sealed in and ducted correctly, and yes, from what other people have mananged, the nostrils should give you enough airflow for it.

I agree. Those hoses do look a little too small.. Consider the water pressure at 7300 RPM. Your looking at a possible water pump failure there...

flat_iv wrote:Someone talk me out of this madness.

M. Poiseuille (1797 - 1869) can.

Poiseuille was interested in the flow of a fluid, actually blood, in narrow tubes, and found that the flow rate Q was related to the pressure difference Δp by Q = ( pi*r4/8Lμ ) Δp. Here, r is the radius of the tube, and L its length and μ is the absolute viscosity of the liquid in poise. pi is itself.

This is hard to reproduce on this forum, but that "r4" above is actually r raised to the power 4. Thus, for a given flow rate, we can conclude that e.g. pressure drop is proportional to the length of the tube - which makes perfect sense. We can also conclude that pressure drop is inversely proportional to the fourth power of tube radius (or diameter) for a given flow rate. This means that, for a given flow rate, halving the radius (or diameter) of a tube will increase the pressure drop by a factor of 16! (or , to look at it in the way the equation was presented, the flow rate achievable for a given pressure drop will fall be a factor of 16).

Now, Poiseuille's law only holds true for laminar flow in relatively small tubes, and for high speed flow and larger tubes life becomes more complex, but flow rates through cooling water systems are generally quite low, and the imprecision of partly turbulent flow doesn't let you escape from the generalities of M. P's law: small pipes suck.

On motorcycles the "L" part of the equation is tiny, and the designers are very concerned about weight and aerodynamics, so they are probably using relatively high pressure pumps to keep tube diameters down for low aero drag and low weight.

hth

[ Edited on 16-1-06 by modulus ]

So what you are saying Modulus, is that it's a bad idea. Besides, how much stuffing around would it be to change the pipe fittings to the 7/8 size. Better to stick with 1.5inch, it's a very common size. Make some templates for the pipes out of thick wire, like coathanger stuff, with the bends in the right places. Then you go down the local muffler shop and get him to bend up the pipes to match the tmplates. He can make it up out of mild steel (antifreeze means it won't rust), or stainless if you're feeling rich. Cheap and cheerful. :thumb

Or aluminium if you want to keep weight down. Or rubber water suction hose if you want to flex it a bit. $35 per metre

what sort of fans do you intend to run?

If I attempt the dual radiators I was going to use the largest fan possible. 8 or 10". I was in a junk yard a few weeks ago and ran across a Dodge Neon had a radiator that was approx. 15" x 15" and had 1 1/4 or 1 1/2" water inlet/outlet. I am not sure if the radiator belonged to the car because it was in the back seat. I am going to go there tomorrow after work to check it out again. I hope that the radiator is still there. I have found sever motorcycle radiators that have a 1" inlet/outlet. If I use the cycle ones I was going to plum 1 1/4" pipe front to rear and use a 1" to 1 1/4" adapters in the front and 1 1/4" to 1 1/2" in the rear.

I was thinking dual radiators because I do not want to cut up the tire well or the front of the car. I do not think that one radiator in the fender will cool the engine.

[ Edited on 17/1/2006 by flat_iv ]

in each front fender well

The radiators could br prone to damage from rocks and any mud thrown on to the radiators would quickly stop all air flow.

couldnt you have some sort of mesh protection it? not too small meshing. decent size, big enough to stop any largish rocks....wouldnt interupt air flow too much i shouldnt think?

and could even chroms the mesh and make it nice and thick if you still wanted the car to look good from all angles.


this is what i was thinking of doing maybe. (except with one intercooler in each fender.



Anthony

I have just picked up a KR1 radiator for the water to air intercooler....really light, although the pipes look way too small for the engine. How about mini radiators. In the moke, they sit on the side and draw air through louvers...no direct flow. they are tiny, and easliy accessible.

The back of any radiator will have a fan and depending on the choice a shroud as well. This would protect from stones etc and the front would be as vunerable as any other radiator set up, without some mesh or grille.

The 996 has twin radiators, one under each gaurd!!!

Matt

I was going to box in the radiator inside of the fender well so rocks wouldnt hit it and vent the air out through some mesh.
996 rad's are approx. 16 W x 14 3/4 H.

[ Edited on 17/1/2006 by flat_iv ]

I'm using dual series connected radiators in my engine conversion set-up, but that's in the back of a Eureka kit car. see this post. http://forums.aussieveedubbers.com/viewtopic.php?tid=42102

I believe I have found the perfect radiators. It is out of a 95 Dodge Neon. The radiator is 14" x 16" with 2 1/4" inlet/outlet. I cut some cardboard as a template and it fitted very well. I will have to still cut the fresh air duct work in the fender well that runs from the nostrils to inside the car.