Cooling Question

[Hog]

Originally Posted by Dynomite

That is the pressure required to push the Coolant through the engine block and Radiator (and associated hoses including the Thermostat). That is a Hydraulic term describing the pressure required to push fluid through a pipe. The more pressure you apply the greater the fluid flow.

Or if you google Head Loss To move a given volume of liquid through a pipe requires a certain amount of energy. An energy or pressure difference must exist to cause the liquid to move. A portion of that energy is lost to the resistance to flow. This resistance to flow is called head loss due to friction.

The First set of Calculations is for The Pressure Drop in Oil Lines and is a bit complex but the same calcluations can be done with Coolant Flow. In the Second set of Calculations below we already know the flow characteristics of the Coolant Pump and Marc suggested the block resistance at 100 gpm is approximately 20 psi (which is the Head Loss at 100 gpm Coolant Flow) ...so a lot simpler as we really do not need the pressure drop unless we want to calculate flow rates (which we already have by measurements). In Marc's suggestion above the Head Loss is 20 psi.

Tech Info - LT5 Pressure Drop In Oil Lines Calculations
Tech Info - LT5 Coolant Flow Calculations

Thanks, I didn't want to appear critical in case it was a typo.

Looks like increasing w/p speed is the "correct" way to tackle this. The 1st world issues that we have. The ZF trans combined with high rear gears, coupled with a high rpm LT5 all combine to give us non-optimal off idle cooling.

[KFoster]

I think I've installed over 50 sets of underdrive pulleys in my life, maybe many more than that. The percentage reduction has little effect with cooling at high RPM, but at lower RPM and idle it is more noticeable. Alternator and cooling can be greatly impacted at idle. So, if you are underdriven by 25%, at the 15 gpm flow rate listed by Dynomite at 800 rpm, your waterpump is seeing only 600 rpm equivalent. That would be around 11.25 gpm. Underdrive pulleys are great for a small increase in HP as long as cooling and charging is not impacted.

[XfireZ51]

The previous thermo had 4 holes drilled. I'm going to drop the coolant and put 2 small holes in the stock 180. We'll see if that mitigates the effect of under drive pulleys at idle and slow cruise.

[XfireZ51]

Ok, coolant is back in the car. We put 2 holes in the thermo. Previous therm had 4. Haven't driven it yet, but I started it to get coolant back through the system and burp it. Temps got to 104C and then stabilized. I was able to then put another 3 quarts in. I'll let it sit overnight to burp it further, then maybe get a chance for a run later this week after the rain. Maybe a pizza run.

[Dynomite]

Originally Posted by XfireZ51

Ok, coolant is back in the car. We put 2 holes in the thermo. Previous therm had 4. Haven't driven it yet, but I started it to get coolant back through the system and burp it. Temps got to 104C and then stabilized. I was able to then put another 3 quarts in. I'll let it sit overnight to burp it further, then maybe get a chance for a run later this week after the rain. Maybe a pizza run.

Drive 55-60 mph in sixth for a while to see where the Temp goes....Use the HVAC display for Coolant Temp in deg Centigrade readout (Convert to Deg F for us as you like). Then shift to fifth (55-60 mph) and see where the Temperature goes. Wait until Fri (Close to 70 deg in Chicago) or Sat (in 60s) to take your run. Report back Speeds, Outside Air Temperature, Gearing (fifth or sixth), HVAC Display Temperature, and Vehicle Modifications. We are assuming Stock Differential.

Let us know what happened. My experience is just a bit over 200 deg F in sixth and drops to less than 190 deg F in fifth on relatively cool days such as you will have in Chicago on Fri or Sat but will run that experiment again on Thur and Fri here in South Dakota.

I will run an identical experiment in SD on Thur or Fri (will be very close to 70 deg F) and report back to you using a relatively stock 90' with Haibeck Chip, Multi Core Aluminum Radiator, and Stock DIfferential. I will report Speed, Outside Air Temperature, HVAC Coolant Temperature (Go to #16), Gear, and assuming no wind that may effect Air Flow one way or other. I wil also report the approximate time Coolant Temperature re-stabilizes after shifting from sixth to fifth gear. Again......this experiment will be done at 70 deg F Outside Air Temperature within a couple degrees.

In CA at 100 deg F outside Air Temperature it is quite obvious the differences in cooling running moderate speed (55-60 mph) in sixth gear vrs fifth gear except the Coolant Temperatures do run a bit over 200 deg F even in fifth Gear and approach 215-220 deg F in sixth gear. This using a 90' ZR-1 with Haibeck Chip and Multi Core Aluminum Radiator.

Oh.....I run with Debree Screen Clean Radiator, Clean Oil Cooler, and Clean Air Condensor and Green Antifreeze good to minus 20 degrees F in all vehicles. One 90' I am running is good to 0 deg F which I may add some antifreeze

[XfireZ51]

That's part of my plan. I'll do some idle testing today, then the FBI is having a Pizza Night Friday for our Corvette Challenge victory (again).
BTW, the 92 has a direct Coolant readout, along w other gauges, on the Speedo display.

[Dynomite]

Originally Posted by XfireZ51

That's part of my plan. I'll do some idle testing today, then the FBI is having a Pizza Night Friday for our Corvette Challenge victory (again).
BTW, the 92 has a direct Coolant readout, along w other gauges, on the Speedo display.

50 deg F - 70 deg F outside Air Temperature.
Ron Davis Radiator.
Haibeck Chip (fans ON 205 deg F, OFF 200 deg F).
1990 ZR-1 #72 (40,000 miles).
Stock Exhaust.
180 deg F Thermostat.
Green Antifreeze down to -10 deg F.

6th Gear
65 mph
1,500 rpm
207 deg F Engine Coolant Temperature

5th Gear
65 mph
2,200 rpm
190 deg F Engine Coolant Temperature

17 deg F cooler running 65 mph in 5th Gear rather than running 65 mph in 6th Gear.
Did the cycle several times with identical results. Coolant Temperatures moved from min to max and back in a minute or two after shifting Gears.

Idle at 850 rpm 203 deg F.

Got this Alternator diagnosed on this run and it turns out the Rectifier was burned/shorted....New Rectifier on Ebay for $68.
This Alternator will go into 1990 #72 later on (130 amp Alternator)

[XfireZ51]

Ok so today, first try

Ambient Intake Temp 53F/12C
Idle condition 850-900rpm
Coolant Temps 86C Stable
Fan 1 operating

[Dynomite]

Originally Posted by XfireZ51

Ok so today, first try

Ambient Intake Temp 53F/12C
Idle condition 850-900rpm
Coolant Temps 86C Stable
Fan 1 operating

Do you have a Chip?
You have a fan running at 187 deg F???

When do your fans come on and off?
My fans with Haibeck Chip (fans ON 205 deg F, OFF 200 deg F).

What Radiator are you using?
I will do some idle tests tomorrow also at 70 deg F outside Air Temperatures

I am assuming you have stock Differential and would run same RPMs at 65 mph as I noted.
I just observed my Speedometer and RPMs so could be off a bit but think I am pretty close to speed vrs rpms.

[XfireZ51]

I do my own calibrations. Fan 1 comes on at 83C, Fan 2 @ 89C
I am using a Fluidyne rad and 180 Thermo.
Diff is 4.10 BUT w 19" Z06 wheels/tires. So overall ratio is more
like a 3.55.