Just how big does a radiator hose need to be?

OK here's the situation. My parents went away for a weeks vaca......uh...hmm. Sidetracked already.

So I finally relocated the radiator on the fiat to the front of the car. I ended up running 1" EMT conduit to the front of the car. To get the water there and back.

So After all this work I am left with 2 issues. The first is the volume of coolant is just too large. It takes almost 45 minutes on a 90 degree day for the engine temp to stabilize at 180F. The second is less ground clearance even though I tried my best to tuck it up as high as possible. It scrapes over speedbumps and on the gravel pulling into my driveway.

So after thinking about it I am beginning to feel that the diameter is overkill. The hole in the thermostat that all the water going to the radiator through is maybe 1/2" at the most when fully open. That transitions to a 1 inch hose that runs 6 or 7 feet to the radiator and then another one that runs all the way to the back of the car and enters the suction side of the Meziere electric water pump which is.....you guessed it, just over 1/2".

Now I just happen to have a 20 foot spool of 5/8" ID stainless steel braided teflon tubing laying around. Why wouldn't this be a perfectly fine and sensible solution?

smaller radiator?

Little civic radiator. One of the smallest I could find.

I'm not sure. But I bet this calculator may tell you something interesting about changing the diameter of those lengths...

where is your thermostat?

Thermostat is in the stock location right on top of the cylinder head at the water outlet.

The gates calculator tells me I will see a 20 psi pressure loss. What that means in this scenario I am unsure.

Everything is working correctly and you can watch the tstat open and close by monitoring the clt readings in tunerstudio but what used to be a under 1 gallon coolant system is now almost 3 and it takes my tiny motor quite a while to heat all that up, particularly now that there is airflow over the radiator.

Ah man, his is my area of expertise (heat transfer and fluid mechanics). I made some estimates and I think you'll be Ok with the smaller diameter hose. But, if it were me, I'd double it up if possible. (run 2 of those smaller hoses up to the radiator and run 2 of them back to the engine) By doing this you'll cut down on pumping losses and pressure drop which will get you a little more hp (maybe 1 hp) and will generally keep the cooling system and water pump happier.

With a relatively low power engine (I'm assuming you're not over 120 bhp) you shouldn't need a very large radiator, if you have good fans on it (a small civic one like ditchdigger suggested is fine).

Also, as mad_machine brought up, the slow warm-up time sounds like a problem with the thermostat opening too early. The extra coolant volume doesn't make that much difference.

Just read your last post - if your t-stat is opening at the correct temp, then the radiator is just a little over sized. How big is the one you have in there?

It is just a little civic radiator

The same one that was mounted in the rear of the car. It just now has 16 feet of tubing between it and the motor. By the time the tstat opens, the motor takes in a big slug of cold coolant and closes the hot water hasn't made it to the radiator yet. After 2 or 3 cycles the rad will start to heat up but if the car is moving that is already being rapidly cooled.

The water pump is electric 20gpm with -12AN fittings and is probably a tad bit overkill. I purchased it from a guy who was using it on an LS1.

This was all working beautifully before but I was having space issues with a fan large enough to keep air moving over the radiator. In the stock location there is no natural air flow, just what is blown over it by the fan.

Is that an OEM civic radiator - it looks like it's much thicker (maybe a twin core)? This is the one I was thinking of: rad pic I'd say both that, and the water pump are WAY over-sized for an engine putting out around 120 bhp.

Is the cooling fan on all the time? If so, that's going to make things much worse too. You can get a relay with a temp. sensitive probe from a local parts store that will only turn on the cooling fan when the temp goes over a certain point. I picked one up for my Datsun for <$20. Depending on how your MS is set up you can do it with that too.

If you already have a controller for the fan (or use MS), then maybe the easiest way to solve this is to reduce the voltage to the water pump. You'll use less energy and pump less water that way and your system should heat up a lot quicker. You can just stick a big resistor or potentiometer in there and drop down the pump voltage to throttle the water flow rate.

If you don't mind loosing a few 10ths of a hp to the water pump the next best thing is just to restrict the water flow (just use single 5/8" lines up and back).

The fan is controlled by a thermo switch and rarely comes on.

The radiator is a double row unit as that was the only one I could find that had aluminum tanks I could weld on to modify.

what about a motorcycle radiator, say 1 liter or so.

cover up half of the radiator with some cardboard, like we do up Noahth

The problem you are having is ALL that cold water beyond the radiator. I would remove the stock thermostat and install a remote one with a bypass.. like a fiat 124 or a BMW E30. Something that will allow your engine to circulate most of the new water around through the engine and heat it up BEFORE it opens the radiator up to the flow.

With all that cold water on the other side of the Tstat like you have it now.. as soon as it opens, it almost immediatly closes

In reply to mad_machine:

or like this?:

http://cgi.ebay.com/ebaymotors/YAMAHA-FZR1000-FZR-1000-THERMOSTAT-HOUSING-COOLANT-TEMP-/110677518964?pt=Motorcycles_Parts_Accessories&hash=item19c4e4ea74#ht_1108wt_954

If someone buys that... PLEASE get measurements for me. This could be a kill eighty three birds with half a stone thing for eg33 swapped imprezas.

this is what I was thinking. They were used on the BMW M10 engine (2002, e21, e30)

Here is a drawing of the fiat with diameters

If you use any of these.. all you would need then is a T placed in the return line. Water would naturally bypass the more restrictive radiator, but would still flow around to warm up in the engine

You could eliminate the thermostat all togehter, and use a vairable speed electric water pump.

You want to keep the pipe as big as possible so you don't cavatate the pump.
I use a $60 stock Civic rad in my dwarf. 130HP GSXR 1000cc motor. It's a good rad and cheap too, looks like you got the $80 E-bay unit in the pict.

Mad Machine if I am understanding you correctly you are saying mount the thermostat up front with the radiator?

That Davies Craig electric water pump controller is a nice looking piece of kit but I don't think I want to go that route, and if it doesn't work with the Meziere it would be a $500 solution to a problem that can be fixed for $40 if I go with the smaller lines.

What you need to do is generate more heat.

Boost it. A lot.

You are welcome.

that's what I am thinking. All that cold water beyond your thermostat instantly cools your engine when it the stat opens.. it might take longer to open, but this way the only cold water is in the radiator.

alfadriver wrote: What you need to do is generate more heat. Boost it. A lot. You are welcome.

18psi not enough?

I did hit 20psi a few times but decided to turn it down for now.

In reply to ditchdigger:

Clearly not, with the cooling problems you hare having. I'd suggest closer to 30. Or 33, since that's a multiple of 11.