cooling

mopar373 said:

Bypass is not suction side, it is pressure because it is designed to blow bubbles off of cylinders and heads.
With a restrictor and no t-stat the bypass should be more of a hinderance than an asset ???

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I disagree....

Without the bypass hose there is no way for coolant to circulate when the engine is cold and could possibly cause localized hot spot, or worse.. serious warpage/damage could occur.. I personally believe plugging the by-pass gains nothing except the chance to damage your engine.. Stagnant water in a running engine is NOT your friend.. and with alum heads, a deathwish..

EDIT I also think without a bypass hose,, the impeller would tend to cavitate when the thermostat is closed,, because of the inability to move any coolant,, and that would lead to other problems,,


The bypass hose sucks warming coolant from below the closed thermostat,, thru the bypass hose to the water pump inlet,,which is the forward chamber of the pump,, where you'll note, in pix,, the return heater hose and the bottom rad hose,, you know ,, the big hose that goes from the bottom of the rad that has the cooled coolant, (that gets sucked up to the pump when the t/stat is open),, into the same forward chamber of the pump where the bypass and heater hose enter... The centrifugal force of the turning impeller, pulls (sucks) coolant from the forward chamber, the impeller vanes throws coolant outward creating positive pressure pushing coolant into the outer passages of the waterpump/timing cover , again see pix, thru the cover it enters into the engine at the front of each cylinder bank,, see pix.. the coolant circulates thru the engine in the normal manner till it gets to the closed t/stat,, where it Bypasses and returns warmer coolant to the suction side of the pump (forward chamber)..

In the Pix - Note the pieces of white wire I inserted to help visualize..

EDIT::

The last 2 pix demonstrate how to fashion a tool to insert down the bypass INLET, snag the impeller, then turn the fan, to eliminate a slipping impeller as a possible source of overheating,, saves taking the pump off,, as many do..

hope it helps

The function of the bypass is also to help keep the temperature of the WHOLE engine closer to the same, as well as help during warm-up as Inertia explained above.

If you have a fast temperature gauge and plug the bypass you can actually watch the thermostat open/close as the gauge needle wiggles along with it. That's no bueno. Keeping the entire block at the same temperature (or as close as possible) helps with longevity and power production and as a result also helps fuel consumption.

Running without a thermostat does nothing but increase the time it takes to warm up. Having no thermostat also reduces the effectiveness of the bypass. Removing or plugging the bypass in a system with no stat is going to have relatively little effect on anything.

Modern engines augment the cooling system with a dual-acting thermostat which blocks the bypass when it opens. The result is a system that is better able to deal with temperature spikes by allowing fully cooled coolant into the block when the stat is wide-open, versus a conventional which still mixes some preheated coolant (Bypass) all the time.

Inertia, that is a great use for 14-2 wire! Just pull it out before installation....LOL

Cool tool idea too.

You gotta remember the coolant entering the engine from the rad should be 40, 50*s or more.. cooler than the coolant leaving the engine,, so by sucking warm coolant from the bypass, I would think, helps mitigate the "shock" of cold water entering the engine.. (just thunkin here)

I believe the bypass also gives the coolant somewhere to go at hi rpm with a partially open stat..

nm9.. I better go do it now before I forget.. lol .. thnx

BTW, as for electic fans working or not, if done right, no problemo. The Mitsubishi Station/Chrysler Conquest had nothing but electric fans for cooling ever, and those HP turbo cars survived fine ..... as long at the thermal switches worked. One fan turned on at around 200F and the other a bit higher.

I rallied a Starion, and even increasing the boost and CR to get somewhere in the 275 HP crank range out of 2.6L at 14-15 psi boost, the stock electric fan system worked fine, even in 90 temps floogging the car hard on long rally stages.

The 1st pix shows the whole setup, with the main (larger) cooling fan on the far side, and the smaller secondary fan on the near side. Notice that there is still clear area in the rad for high speed cooling air flow; they did not foolishly block the areas where the fans did not draw and thus preserved good highway speed cooling. The failing setups where the rad areas are all blocked where electric fans are not pulling are a losing attempt to make up for the wrong blade design in a lot of the cheap electric fans that you can buy... and that don't work. The blocked areas may make these crappy fan blades work sorta-kinda in low speed situations but will screw the cooling to all to hxxx at highway speeds.

The 2nd pix shows the secondary fan up close, to show the thick, wide fans blades. The thin balded cheap fans that folks try to use just won't pull with ANY pressure drop across the fan; a thick bladed one will. A lot of the success people experience when they pull out the cheap thin balded electric fans and put in a stock fan is just due to the blade design, nothing else.

And yeah, that rad core is about 1.25-1.5" thick.... cooling a 275 HP engine just fine with these fans, even at night with 4 8" rally lights across the front of the car.

inertia said:

You gotta remember the coolant entering the engine from the rad should be 40, 50*s or more.. cooler than the coolant leaving the engine,, so by sucking warm coolant from the bypass, I would think, helps mitigate the "shock" of cold water entering the engine.. (just thunkin here)

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Yup. This too. Otherwise the constant expansion/contraction of the block and heads would cause the headgaskets to shift too much and could eventually cause a gasket failure. Much like romping on an aircooled engine before its warmed up.

inertia said:

I believe the bypass also gives the coolant somewhere to go at hi rpm with a partially open stat..

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Yup. Or when it's fully closed too. Otherwise you get hot spots, as several have suggested. Water will boil rapidly on a hot surface and thermal control runs away in that area. Keep it moving, and it carries the heat away without boiling and causing a runaway situation.

Thanx - nm9stheham,,

Your's may have been one of the few successfull OEM users I had read about,,

Hopefully your post will help guide those who do some research on how to used elec fans ,, and get it right the first time.., "search" being the keyword.. lol

cheers

Thanks Phraekish. You answered my initial question in block#27. My fans are set at 180* on and 160* off. I'm trying to keep the temp close to that mostly for longevity. In cool weather it stays between 160* and 175*, but when it's hot & humid is when it acts up. Fans pull 2000 CFM, I'm thinking that I need more like 3000. 500 HP aint easy to keep cool at traffic lights. I've been around Mopars for over 6 decades and still learning. If you need anything just let me know. And thanks to all you other guys helping. AL

don't use a thermostat if you plug the bypass ,when its cold and thermostat is closed your heater core will take full pressure unless you keep the heater control valve closed and in the winter I would want as much heat as fast as I could get it, and i don't like changing out blown cores, just a thought.

mopar373 said:

Thanks Phraekish. You answered my initial question in block#27. My fans are set at 180* on and 160* off. I'm trying to keep the temp close to that mostly for longevity. In cool weather it stays between 160* and 175*, but when it's hot & humid is when it acts up. Fans pull 2000 CFM, I'm thinking that I need more like 3000. 500 HP aint easy to keep cool at traffic lights. I've been around Mopars for over 6 decades and still learning. If you need anything just let me know. And thanks to all you other guys helping. AL

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Do they really pull 2000 cfm or are they 'rated' at 2000 cfm? If 'rated', you might be shocked to see to how low the actual flow drops with any amount of pressure drop; there is always significant pressure drop through a rad so fan blade design has a big influence in auto cooling systems. Can you share the fan models and makes?

IMO, running less than 180F will likely cause less longevity. The internals may not be getting to full temp and proper expansion, and oil cleaning needs some heat.

^^You are right about the fans CFM, But a motor should be run at the temp that you brake it in. In 60 years i've never heard of running a motor below 180 will cause longevity problems unless it was broken in at a different temp.

i also went the mystique/contour dual fans with 22" 3 core.. Car cools to around 120 with both fans running very quickly. going to have to mod the temp sensor or setup a switch cause the fans always run at key on..

Followed install directions for the Hayden to the letter..maybe a bad switch??

pics are on my build thread.

kybatman said:

Followed install directions for the Hayden to the letter..maybe a bad switch??

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Could be. Such wide ranging temps are not good for the motor's internals. Piston skirt design is such that they tend to stabilize across a certain range of temps, and those temps are the 'typical' engine operating temps of 180-220F or so. Hypereutectics help that, but it they still have their stable shape and size across a certain temp range. Below that temp range, they get loose, and when you barely exceed the hot end, the skirts' shape and dimensions distort totally out of whack. You can see this by very gradually heating a piston in an oven and checking the dimensions at various temps... I did this 30+ years ago and it was very educational!

nm9stheham said:

Do they really pull 2000 cfm or are they 'rated' at 2000 cfm? If 'rated', you might be shocked to see to how low the actual flow drops with any amount of pressure drop; there is always significant pressure drop through a rad so fan blade design has a big influence in auto cooling systems. Can you share the fan models and makes?
IMO, running less than 180F will likely cause less longevity. The internals may not be getting to full temp and proper expansion, and oil cleaning needs some heat.

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Agreed. Take any ducted fan and let it work in open air, then restrict the intake side, and see the difference.

I've been running my 360 at VERY HOT (very scientific, I know) for 16 years/125,000miles. The stat is a late operating 195. The IR gun reports a minimum running temp of 205.She likes it. Mind you, my engine is about 70hp less than yours. But around town,or stopped, that means very little. Mine has run 11.2Scr with exactly the same results; no problem.
I can't tell you what the exact temperature varies to, (or for that matter;what the actual oil pressure is), cuz I'm such a tightwad that I'm still running the factory rally cluster with the ssslow needles, and no calibration. Fancy gauges to me are just one more thing to worry about.
Ok, so.............. I do have a tach,tho.
My rad is an 26"A/C unit from a 73 teener-Dart.It's pushing 43 years old and well over 250,000 miles.
FWIW; you couldn't pay me to run electrics. I have enough torque to annihilate the 295s to somewhere near the top of second gear.(3.55s). I can break them loose at 50mph in the same gear. She went 93 in the 1/8th and the start-line workers were reporting tiresmoke with 325/50DRs all the way down the track. I know, I know, street suspension. Nice soft speed-bump eating springs.
I totally don't care about any lost horsepower to the big 7-blade fan.....