Correct engine coolant temperature

[salvatore1]

Originally Posted by secondchance

One thing you can try is find a high pressure washer car wash. Then secure the fan so that washer wouldn't run the fan blade and pressure wash between the fan blade blowing out. You can only hit limited area but typically it's the same area where build up was when I pulled the radiator.

http://www.zr1specialist.com/HAT%20W...librations.pdf

Page 12 of this presentation talks about factory fan strategy verses his chip.

Hey thanks for your idea - I think I'll give it a try.

[secondchance]

For reference, today it was 80 degrees here in Northern Virginia. On the highway my Z was running at 201 degrees and it represented 1/6 below half point on analog gauge.
For stop and go traffic, between 203 and 207 (1/8th below half way point on analog). Never saw 210. This is w/ Marc's chip.

[QB93Z]

I am convinced that the cooling problem with the ZR-1 is related to the bypass flow around the radiator. In both my 1990 ZR-1 and my 1993 ZR-1, I have brand new high capacity radiators (a DeWitt and a Ron Davis) and Haibeck chips.

In both cars when cruising at about 55 mph in sixth gear (about 1600 to 1800 rpm, the coolant temperature will rise to around 225. If I shift to fifth gear, (>2000 rpm) the temperature immediately drops to around 203-205. The drop is rapid (you can see the needle move). This indicates to me that there is plenty of cooling capicity available (ie air flow and heat transfer from the radiator) but that at low rpm most of the water pump output flow is bypassing the radiator through the radiator bypass line.

Under higher engine load, such as running at 80-85 mph the coolant temperature is stable at around 195.

My next research attempt is going to be replacing the thermostat (which also has the bypass flow valve built into it. I may even try to block off all the low rpm bypass flow just to see what happens.

Jim

[salvatore1]

Originally Posted by QB93Z

I am convinced that the cooling problem with the ZR-1 is related to the bypass flow around the radiator. In both my 1990 ZR-1 and my 1993 ZR-1, I have brand new high capacity radiators (a DeWitt and a Ron Davis) and Haibeck chips.

In both cars when cruising at about 55 mph in sixth gear (about 1600 to 1800 rpm, the coolant temperature will rise to around 225. If I shift to fifth gear, (>2000 rpm) the temperature immediately drops to around 203-205. The drop is rapid (you can see the needle move). This indicates to me that there is plenty of cooling capicity available (ie air flow and heat transfer from the radiator) but that at low rpm most of the water pump output flow is bypassing the radiator through the radiator bypass line.

Under higher engine load, such as running at 80-85 mph the coolant temperature is stable at around 195.

My next research attempt is going to be replacing the thermostat (which also has the bypass flow valve built into it. I may even try to block off all the low rpm bypass flow just to see what happens.

Jim

I know what your saying because I do notice a change in engine speed does affect the temperature almost immediately. But with that said, I'd be very careful about defeating the bypass feature as this may send too much water presure through the radiator and possibly blow it out.

[secondchance]

Originally Posted by QB93Z

I am convinced that the cooling problem with the ZR-1 is related to the bypass flow around the radiator. In both my 1990 ZR-1 and my 1993 ZR-1, I have brand new high capacity radiators (a DeWitt and a Ron Davis) and Haibeck chips.

In both cars when cruising at about 55 mph in sixth gear (about 1600 to 1800 rpm, the coolant temperature will rise to around 225. If I shift to fifth gear, (>2000 rpm) the temperature immediately drops to around 203-205. The drop is rapid (you can see the needle move). This indicates to me that there is plenty of cooling capicity available (ie air flow and heat transfer from the radiator) but that at low rpm most of the water pump output flow is bypassing the radiator through the radiator bypass line.

Under higher engine load, such as running at 80-85 mph the coolant temperature is stable at around 195.

My next research attempt is going to be replacing the thermostat (which also has the bypass flow valve built into it. I may even try to block off all the low rpm bypass flow just to see what happens.

Jim

That is unusual! I never noticed anything similar on 91 nor 94.
Maybe, I just didn't notice? I will duplicate your description later today.

[tomtom72]

Originally Posted by secondchance

That is unusual! I never noticed anything similar on 91 nor 94.
Maybe, I just didn't notice? I will duplicate your description later today.

I agree, I think. It appears to me that my 90 will become more heated if I spend much time in the lower gears, like doing road work where 3rd & 2nd & 4th are used alot....specially if I slow down and cease playing and drive normally. At that point it appears that I heat soak for a good while till the cooling system calms down or catches up to the heat load that I just generated by my sophomoric behavior......it appears that the higher I go in the rev band, and the longer I stay higher in the revs, the more by-passing takes place in my 90's cooling system? It appears if I insist in living up past the 4k mark that after a good while the oil & coolant temps start to spike even if my velocity is at a good clip. I seem to get my best cooling performance when I can keep to about 2k or below in 5th or 6th with a constant speed. Maybe I have something malfunctioning?

[QB93Z]

Originally Posted by tomtom72

I agree, I think. It appears to me that my 90 will become more heated if I spend much time in the lower gears, like doing road work where 3rd & 2nd & 4th are used alot....specially if I slow down and cease playing and drive normally. At that point it appears that I heat soak for a good while till the cooling system calms down or catches up to the heat load that I just generated by my sophomoric behavior......it appears that the higher I go in the rev band, and the longer I stay higher in the revs, the more by-passing takes place in my 90's cooling system? It appears if I insist in living up past the 4k mark that after a good while the oil & coolant temps start to spike even if my velocity is at a good clip. I seem to get my best cooling performance when I can keep to about 2k or below in 5th or 6th with a constant speed. Maybe I have something malfunctioning?

Tom,

I think you are seeing two effects.

1. If after a period of spirited driving (increased engine heat load), the temperature is high, you may have a radiator fouling problem. But if the temps are not way high, then the fouling problem is not too severe.

2. The worst cooling capability for my LT5 occurs at light load (5-10% throttle) and low rpm (< 2000 rpm). Because of the notches in the bypass flow valve there is barely sufficient water flowing through the radiator to remove the heat load. At these conditions, even with a perfectly clean radiator and perfect air flow (both fans running) the temperature of the coolant will rise way above the desired temperature.

Jim

[tomtom72]

Sal, yes the two relays that you find on the left side of the radiator shroud are the fan relays. It sounds like one of the motors has a bearing issue if it wouldn't turn freely. I'd keep an eye on that one.


Jim, thanks for your advice. I will have to admit that when I was trying to clean my OE radiator that after a while I gave up on the sand particles....I didn't get them all for sure!

Oh well, I guess it's time to start shopping for a new radiator as I'm very OCD about the coolant dump & flush & t-stat R&R every two yrs. Perhaps a Marc Haibeck EPROM is in order also.

[USAFPILOT]

At what temp would damage to the engine occur? That seems to be more important than who's car runs the coolest and why?

[Tyler Townsley]

Originally Posted by USAFPILOT

At what temp would damage to the engine occur? That seems to be more important than who's car runs the coolest and why?

You get over 260 for any length of time and depending on the age/miles of the engine bad things begin to happen. The location of the water temp pickup can result in a misleading temp on the guage if there is low water in the motor. It is one of the first locations to see steam vic water which results lower temp reading. You need to watch oil temperature reading too.

Tyler