MONZORA redux: ‘65 Corvair + ‘94 Corvette mashup for 2019 Challenge

AngryCorvair (Forum Supporter) said:

wvumtnbkr said:

Once it's open it's just open.  As if it wasn't there.

 

If the coolant system can't get rid of the heat, the engine will get hot no matter the thermostat temp.

 

Thermostats only keep the fluid in the engine HOT so that everything heats up.  Once it opens, it's like it isn't there.  

Unless the return from the heat exchange system is at a lower temp than the thermostat transition point, in which case the thermostat will close, at least partially, yes? 

I gotta agree with AC here.  The thermostat will cycle as long as the radiator can remove more heat than the engine produces.

Dusterbd13-michael said:

he has to drive it to worry about the rain....

Dude!  

 

love ya angy!

Edited to add: Nice work on the louvers, especially welding when it's hot and gross out.  Looks great!

Stampie said:

AngryCorvair (Forum Supporter) said:

wvumtnbkr said:

Once it's open it's just open.  As if it wasn't there.

 

If the coolant system can't get rid of the heat, the engine will get hot no matter the thermostat temp.

 

Thermostats only keep the fluid in the engine HOT so that everything heats up.  Once it opens, it's like it isn't there.  

Unless the return from the heat exchange system is at a lower temp than the thermostat transition point, in which case the thermostat will close, at least partially, yes? 

I gotta agree with AC here.  The thermostat will cycle as long as the radiator can remove more heat than the engine produces.

I mean, that's the very definition of a closed-loop control system, isn't it?

Those louvers look great! Be careful when fully welding them so you don't warp those big flat sections. Lots of tacks, go slow, and grind easy with fresh flap discs.

In reply to AngryCorvair (Forum Supporter) :

Why you gotta add fancy engineering terms to my redneck explanation?

I would think, if nothing else, getting coolant started circulating at a lower temp should give a bit more run time before things get overly hot.  So for quick blasts around a track this should be useful at a minimum. 

I think the louvers look good and I'm curious how they will end up being finished, like if they'll be painted or left raw looking or what.  Hopefully they help a bit with the heat.

pres589 (djronnebaum) said:

 

I'm curious how they will end up being finished, like if they'll be painted. 

berkeleying guy can't even wash his car, self admitted, you think he's gonna paint them?

Just kidding Patrick, you do you. I got your 6. Love this build.

Stampie said:

AngryCorvair (Forum Supporter) said:

wvumtnbkr said:

Once it's open it's just open.  As if it wasn't there.

 

If the coolant system can't get rid of the heat, the engine will get hot no matter the thermostat temp.

 

Thermostats only keep the fluid in the engine HOT so that everything heats up.  Once it opens, it's like it isn't there.  

Unless the return from the heat exchange system is at a lower temp than the thermostat transition point, in which case the thermostat will close, at least partially, yes? 

I gotta agree with AC here.  The thermostat will cycle as long as the radiator can remove more heat than the engine produces.

That is true.  But if the system balances at 210 f, it doesn't matter what temp the thermostat is (if less than a 210 thermostat).

https://help.summitracing.com/app/answers/detail/a_id/5284/~/should-i-run-a-colder-thermostat%3F#:~:text=If%20you%20want%20your%20engine,will%20NOT%20solve%20overheating%20problems.

AngryCorvair (Forum Supporter) said:

759NRNG said:

well I must admit this came out well beyond my expectations.....well done 

just don't look too close at the welds.

ziiiiiiiiiiing! 

Oh don't worry I can see em from here .....chop shot into the net 

Somehow I missed the overheating that the last 3 pages are alluding to. How hot? How long to get hot? How much total coolant volume measured on first fill up? How and where do you bleed the top points in the system? Does it need steam lines like an LS?  Does it push coolant out the overflow? All front radiator rear engine cars have their issues. 

In reply to wvumtnbkr :

i do not accept their explanation. there is no way an OE vehicle manufacturer is using the cooling system's capacity to maintain a consistent operating temperature.  if this was true, you'd see the temp needle moving around pretty much all the time within a drive.  accelerating vs steady speed vs decelerating, increasing vs decreasing grade, high elevation vs low elevation, headwind vs tailwind, etc.  and you'd certainly not have the same reading winter vs summer.  the cooling system is sized for worst-case operating conditions, and the thermostat regulates flow to keep the operating temperature within a few degrees of the target.

TurnerX19 said:

Somehow I missed the overheating that the last 3 pages are alluding to. How hot? How long to get hot? How much total coolant volume measured on first fill up? How and where do you bleed the top points in the system? Does it need steam lines like an LS?  Does it push coolant out the overflow? All front radiator rear engine cars have their issues. 

the car has not overheated the cooling system per se, but there's a lot of heat hanging around in the engine box due to the header packaging.  recent efforts with plumbing from front cowl to center duct, boxing and forcing air through header heat shields, and venting rear deck, are designed to move that hot air out of the engine box.

I have two pressurized coolant bottles, both of which are the local high points.  one is in engine box, which connects to both heater hoses from water pump, as well steam tube from rear of cylinder heads.  the other is in frunk, and T's into upper radiator hose as well as tube from top of radiator.  radiator does not have filler cap, hence the need for second pressurized bottle.

there is also a bleeder in the top of the inlet housing on water pump.

Agreed, my understanding is the thermostat is the thing that should control coolant temperature. (And then to some extent the fans).

Too cold is just as bad as too hot! So the thermostat is only partially open most of the time. 

A lower degree rated thermostat can make an engine appear to not overheat because it can be "more open" at operating temp than a higher rated thermostat. But if this is the case, the whole cooling system is on the ragged edge of operational parameters!

AC wrote: " there is no way an OE vehicle manufacturer is using the cooling system's capacity to maintain a consistent operating temperature" and I completely agree with this.  Assuming the pump, rad, fans, and general airflow is in good shape the system should work properly.  

The fun is engineering this using a car that wasn't meant for water cooling of the engine and an engine & cooling system that was engineered for a car that is extremely different from a Corvair.  And doing it on a shoestring budget.

AngryCorvair (Forum Supporter) said:

In reply to wvumtnbkr :

i do not accept their explanation. there is no way an OE vehicle manufacturer is using the cooling system's capacity to maintain a consistent operating temperature.  if this was true, you'd see the temp needle moving around pretty much all the time within a drive.  accelerating vs steady speed vs decelerating, increasing vs decreasing grade, high elevation vs low elevation, headwind vs tailwind, etc.  and you'd certainly not have the same reading winter vs summer.  the cooling system is sized for worst-case operating conditions, and the thermostat regulates flow to keep the operating temperature within a few degrees of the target.

I do see that when looking at actual temp readings.  That's also why the fans on newer cars starts and stops.

What I'm saying is that a thermostat temperature change (to a lower temp thermostat) will NOT lower the engine operating temp while under normal load.

I've been down this road with various racecars and project cars.  

If you want it to run cooler, work on airflow and ducting.

If it's not too difficult to change on an lt1, try it as an experiment.  Swap out a 160 and a 195 and see if the temp goes down with the 160.

Edit.  I think I now see where you are coming from.  If the system is large enough (too large), yes, the system will just run at thermostat temp.  High performance vehicles that can run under load much more use more of that capacity.  

If your system is sufficiently large, yes, the system will run at thermostat temp.  I do agree with that.

I have not come across a system like this in motorsports.  Usually getting temps down is done with proper ducting and airflow through the system.  This has a WAY bigger impact on operating temp than when the thermostat opens.

You're all right in different ways. There are two parts to the problem here: steady-state and transient

At steady-state, if the cooling capacity is large enough, the engine will stabilize at the thermostat temp. wvumtnbkr  is right about this. If the car is overheating at idle or on the highway, the capacity is definitely not enough. Need to add fans, ducting, radiator size, etc. 

Most racing engine loads are not steady-state, but transient. Full throttle drag run for 12 seconds (15+ in AC's case), then back to low load. Or full throttle out of the turn, then braking zone. The cooling system has "thermal inertia". Think of a classic physics problem with a body being accelerated. The change in speed is directly proportional to change in momentum. If you start at a lower initial speed, you need more momentum to get to the same final speed. Same thing with heat. If your engine is stabilized at a lower temp, but then you put the hammer down, you have more time until the engine begins to overheat. This is why some people find a lower t-stat temp fixes their overheating. They didn't change ultimate heat capacity, just changed the momentum (time) needed to overheat by starting at a lower temp. 

So yes, a lower t-stat temp might fix AC's problems depending on how they happened, and so would better cooling capacity. 

maschinenbau said:

Most racing engine loads are not steady-state, but transient. Full throttle drag run for 12 seconds (15+ in AC's case), then back to low load.

that stealth smack.  i like it.

also, to those of you with questions or concerns or interest in how the decklid will be metal-finished: it already is.

AngryCorvair (Forum Supporter) said:

also, to those of you with questions or concerns or interest in how the decklid will be metal-finished: it already is.

That deck lid is hawt.

I love this car soooo much!  Keep going.

maschinenbau said:

You're all right in different ways. There are two parts to the problem here: steady-state and transient

At steady-state, if the cooling capacity is large enough, the engine will stabilize at the thermostat temp. wvumtnbkr  is right about this. If the car is overheating at idle or on the highway, the capacity is definitely not enough. Need to add fans, ducting, radiator size, etc. 

Most racing engine loads are not steady-state, but transient. Full throttle drag run for 12 seconds (15+ in AC's case), then back to low load. Or full throttle out of the turn, then braking zone. The cooling system has "thermal inertia". Think of a classic physics problem with a body being accelerated. The change in speed is directly proportional to change in momentum. If you start at a lower initial speed, you need more momentum to get to the same final speed. Same thing with heat. If your engine is stabilized at a lower temp, but then you put the hammer down, you have more time until the engine begins to overheat. This is why some people find a lower t-stat temp fixes their overheating. They didn't change ultimate heat capacity, just changed the momentum (time) needed to overheat by starting at a lower temp. 

So yes, a lower t-stat temp might fix AC's problems depending on how they happened, and so would better cooling capacity. 

I agree with all of that.

My experience is with endurance racing.  Basically a very high very prolonged load.  Unless the system is optimized for airflow, you would need a YUGE radiator.  Even then, if you don't have the airflow it will get hot (eventually)

At the end of the day, you need enough coolant and airflow running around in the system to be slightly higher than the heat generated by the engine.  If it isn't enough capacity, or it's marginal, I don't care what thermostat you put in.

wvumtnbkr said:

At the end of the day, you need enough coolant and airflow running around in the system to be slightly higher than the heat generated by the engine.  If it isn't enough capacity, or it's marginal, I don't care what thermostat you put in.

OK, so it took us a minute but we have finally both said the same thing. Your endurance racing scenario is what I would call worst-case operating conditions, and in that case it is indeed system capacity, not thermostat, which determines operating temp.

So, why did the car not want to run the last couple of runs at the autocross?  I assumed it was overheating.  To be clear, this is mostly unrelated to the last page or 2 of discussion.

Just curious is all.

I'm still trying to figure out how he managed to go that slow in the drags.

wvumtnbkr said:

So, why did the car not want to run the last couple of runs at the autocross?  I assumed it was overheating.  To be clear, this is mostly unrelated to the last page or 2 of discussion.

there was no airflow through the engine box, and the header shields were only as long as the valve covers, so the engine box was really hot. the fuel lines are above the intake, so i suspect (but have nothing but circumstantial evidence) that i may have been boiling fuel in the lines?  i found several places where the split loom on engine harness was melted, so i'm currently hoping that no wires got melted.

remember though, when i got home i found all spark plugs were only finger tight, so i'm sure that had something to do with it.

and i haven't logged any data other than idle, so i don't know how far off my VE table might be. with a larger cam, higher ratio rockers, and long-tube headers (and relocated o2 sensors), i've got some tuning work to do.

i had to get all the heat management stuff in place before i could reliably run the car longer, so i can get the idle and off-idle tuning done, so i can go log some data and get it running right.

good news is that in all the idling i've done recently, the car hasn't set any DTCs.

maschinenbau said:

I'm still trying to figure out how he managed to go that slow in the drags.

a good comedian tells more than one joke.