nobrakes

I've been advised in another thread that I should pose my questions to this esteemed group. Thanks in advance!

What temperatures should we be running our LS1, mounted in an off-road car?

We're idling and cruising at about 200 degrees, but the temp spikes to 240 when we start loading the engine. We back out of it, temp quickly returns to 200.

What size restrictor would you use in place of the thermostat?

The builder of our engine installed a restrictor with just a 5/16" hole in it. Seems too small to me. I'm thinking more like 5/8" to bring the flow up a bit.

Your comments are appreciated.

DONAIMIAN

iTrader: (18)

I would experiment with the differnet sizes to see what worked better, like I said in the other thread, you should be around 200 or not much over that.

H8 LUZN

Thats why a thermostat works better than a plain restricor....

The thermostat becomes a larger orifice when it requires more flow and smaller when it doesnt.

DONAIMIAN

iTrader: (18)

Its better on a street car, but for a track ***** (he has plans to road race) I wouldnt even run one (I live in teaxas), its just one more part to fail.

andereck

I'd be more worried about losing a belt then have a modern thermostat fail. You can't regulate temperature with a fixed orifice as mentioned. All a restrictor does in a race car is keep pressure in the block to collapse air bubbles/pockets. I'd run a 180 thermostat and not think twice about it, but that's just my opinion.

nobrakes

In fact, we won't even be using this motor on pavement, let alone a track.
It's in an off-road car, the same one we raced in the Baja 1000. The car generally runs in ambient temps from 70 to 120.

So we're trying to minimize possible failures. We've been told a lot of sand car builders are using just a 5/16 hole. But they tend to have short bursts of throttle.

OTOH, we race uphill in sand washes, run high rpms at relatively low speeds, and race across dry lakes for miles at 100+mph.

And, no, we don't have a heater core.

white2001s10

iTrader: (4)

I recommend not running a tstat or a restrictor and you should be fine.

One VERY key point in running without the tstat is that you absolutely MUST block off the bypass passage straight under the tstat housing, or you'll end up running hotter than with a stock tstat in place.

white2001s10

iTrader: (4)

I thought some pictures might help.

Here's a pic from a corvette with the tstat removed.
One of the heater hoses had to be moved since that area was completely blocked with hardening epoxy.

http://memimage.cardomain.net/member...217306_622.jpg


Here's a pic from a V6 with the bypass being directly below where the tstat once sat. You can see the bypass hole is completely filled with epoxy.

http://memimage.cardomain.net/member.../217306_37.jpg


Normally a heater hose has to be moved to another location. Often the factory puts one of the heater hose fittings right next to the bypass. I think on most vehicles it's normally the input side of the heater core that feeds from this fitting.

On some vehicles I move the fitting to an unblocked area to feed from, delete the heater operation (for race vehicles), or in the case of some I can drill through the epoxy so that the bypass is still blocked from backfeeding back into the pump, but the heater can still feed coolant from this area.

I hope this helps some more.
Dan

MSURacing

iTrader: (1)

No Brakes, I think you are mistaken by saying that your truck builder put a 5/16" restrictor in there. I think you mean he put a plug in the area between the front and back passages in the pump and drilled a bleed hole in this plug.
If he did put a 5/16" restrictor in to replace your thermostat, you need to get a new builder, because he doesn't know what he is doing!!!!
I need to make this clear, if your engine needs maximum cooling potential, never install a restrictor. Some people believe that a cooling system needs backpressure. This is wrong. You never want to make your water pump work harder than it already has to, so let it flow freely. Think about it, the more water you are flowing, the more cooling potential you have.

johnpate01

iTrader: (3)

True, but water at 14.7 psi (normal atmospheric pressure) boils at 212 (285? for antifreeze). As pressure goes up, so does the boiling point. Simple physics and thermodynamics. At 29.4 psi (2 bar) the boiling point is about ~23% higher. Why do you think that cars use pressurized radiator caps and cooling systems? Google a phase diagram for water and you can see what I mean. That higher boiling point will help minimize any localized boiling at hot spots. Do what you want, in your case, small diameter hoses may create enough resistance to build pressure, you may have to run a bigger restrictor, a high volume pump will work to build pressure, or something else entirely. Also remember that the more heat that can be contained WITHIN the cylinders, the more efficient the engine is, within reason. A cold engine also pollutes more, with unburned hydrocarbons and oxides due to its lower efficiency.

http://www.ch.cam.ac.uk/magnus/boil.html

HALLZ

iTrader: (1)

Also,....if there is no restriction at all to slow the flow at average speeds of 70+mph and rpm over 2k all the time when and how does the coolant have time to cool before entering back into the block?

Now if the coolant never slows down and spends any time in the heat exchanger (radiator) would'nt that be just like having a long coolant tube for a return route?

How efficient would that be and how would that cool at all???

BTW,
Both cars I ran with out a T stat or restrictor plate over heated and took forever to get to optimal operating tempatures. I would also just use a 180* or shim a old Tstat open as a restrictor, if noting else just give it a try and see.

andereck

No sir, you are incorrect. The water jackets need to have pressure to cool effectively. Pressure collapses air pockets and bubbles allowing more surface contact with the coolant. Without the pressure localized hot spots will occur around the inevitable air pockets and can lead to detonation and other trouble. Pump cavitation from higher rpm operation will create steam bubbles in the coolant as well contributing to the problem.

joecar

Regarding blocking off the heater passage behind the TS:

I'm trying to understand the cooling passages better, how is coolant routed when the TS is in place, and how is it routed when the TS is removed (with and without the passage blocked off)...?

TIA

MSURacing

iTrader: (1)

Do you know how an engine even works? You do not get pressure from the thermostat or a restrictor!!!! You get pressure from water the expansion from being heated!!!!!!!!!!!! And, you can capture this benifit of a higher boiling point by running a 30 psi radiator cap. So, if it doesn't get high enough, you can pressurize the system.

All a thermostat does is open when the engine is warm enough to need cooling. In fact, if you new what the heck you were saying, you would realize that the LS1 has the thermostat on the suction side and there is nothing keeping the pressure localy in the block.

Plus, in the statement, I said if "if your engine needs maximum cooling potential, never install a restrictor." I was not refering to any on the road vehicles. This is for race engines where they need maximum cooling efficiency. I always believe in running a thermostat whenever the situation allows. It is easier on the engine because it stays out of warmup mode and gets to closed loop quicker. But, if the situation calls for max cooling, run it open with no restrictor.

If you don't believe the stuff that I am saying, maybe we could ask Katech how they run the C5-R race engines!!!!

nobrakes

MSUracing said: "I think you mean he put a plug in the area between the front and back passages in the pump and drilled a bleed hole in this plug."

After talking to the car owner last evening (I'm hundreds of miles away), I would say, "You are correct, sir!" in my best Ed McMahon.

Turns out there is no thermostat or restrictor in place. But the symptoms remain:
engine runs 200 at idle and cruise, spikes to 240 when under load. I think it may still have air in the system.

But I remain confused on the necessity of a restriction in the water flow. Do the symptoms mean the coolant isn't staying in the radiator long enough, or that there is inadequate radiator surface?

Thanks for your input,
NBD

nobrakes

MSU, just saw your latest post. How does katech prep motors? They built the Dakar and 24 hr powerplants, correct?

white2001s10

iTrader: (4)

MSURacing speaks the truth. This is how it works in real-life, not in-theory.
The speculations about the pressure and coolant speed being problems is just wrong.


After a cold-start, coolant is pulled through this bottom (bypass) passage which includes the heater-core feed line as well. When the tstat is closed, the bypass valve (extra thing hanging off the bottom of the tstat) is wide open. With the bypass open the pump will be recirculating the coolant from the block right back into the block to speed up the warm-up cycle.
As the tstat opens, the bypass valve closes off the bypass passage. The heater-core feed still gets hot coolant from the block which makes its way through the heater core. Everything else (coolant) from the block must get pumped through the radiator before getting back to the tstat housing and being pumped back into the block again.

Key point here AGAIN:
If you remove the tstat, you are also removing the bypass-valve which leaves the bypass passage WIDE open. This will allow at least 30% of your coolant to get pumped back into the block without ever seeing the radiator. This WILL make you run hotter.

For those of you that removed the tstat and/or tried a restrictor, try again!
This time block the bypass passage so you don't overheat.

What you will find is that you will run MUCH cooler than you did with a tstat in place.
You can start a 1/4 mile pass at 150*F and end your pass at 150*F, NOT at 200*F like the tstat will force. It will make your cool-down cycle MUCH quicker too.

MSURacing

iTrader: (1)

NBD,
I think you are correct with thinking that you have air in the system. How do you have your overflow canister positioned and routed. Also, what accessory drive are you running? Is it an underdrive system? Also, how far is your radiator from the engine? Is this in a Class 1 car? If so I know that the builders don't do a very good job of getting fresh air into the radiator.

But it does sound like air in the system and check out the overflow canister.

nobrakes

MSU,
The engine is rear mounted to a transaxle, so the water pump is at the rear of the vehicle. Coolant tubing comes up and over the engine, trans and fuel cell to a Taurus SHO V-6 radiator with fan mounted high behind the driver and co-driver. There's no windshield, but lots of turbulence in cockpit. The engine vent is plumbed to the filler neck below the overflow. The overflow canister is mounted at about the same level as the bottom of the radiator. We are running with the truck style serpentine layout to get the alternator up out of the dust. No underdrive pulley. It's probably four feet or more from the water pump to rad.

Yes, it's a Class 1 car.

Thanks.

white2001s10

iTrader: (4)

I would think the overflow may need to be up at least even with the filler-neck, or the highest point in the system, otherwise air will have a hard time finding its way out of the system.
Corvettes are bad for this due to the different overflow design.
Fbodies and trucks work very well.