Discussion
Right, am having some hassle keeping all that metal in the back cool.
Do you find that once the fans kick in (at idle in traffic), they stay on? Or do they kick in and out?
Mine come in at 85 degress and then stay on, but it can only hold constant temp. (94 degrees) with the canopy open - which isn't really ideal. Have added Water Wetter but the temperature will creep up slowly with the canopy locked down.
Do you find that once the fans kick in (at idle in traffic), they stay on? Or do they kick in and out?
Mine come in at 85 degress and then stay on, but it can only hold constant temp. (94 degrees) with the canopy open - which isn't really ideal. Have added Water Wetter but the temperature will creep up slowly with the canopy locked down.
Although mine has not hit open road yet, looks like I have a similar problem (with only 415 hp), although dropping idle to 700 rpm just about allows the fans to kick in and out with temp in the 95-100 deg range (and this in Scotland in spring)!
My water temp sender is into the LH cyl head below headers rather than into manifold so maybe this is reading a bit high due to proximity to the hot bits. Does appear to be hard work to keep this thing cool when idling though. Haven't put the water wetter in yet, but am using some red ready mix coolant from Comma which allegedly improves cooling (or maybe just raises boiling point). Next move is switch to H2O + WW to see if it is better. Stig, have you removed thermostat to remove the flow restriction? (not ideal I know). Or maybe need gruntier fans? Cooling seems OK when on the move.
My water temp sender is into the LH cyl head below headers rather than into manifold so maybe this is reading a bit high due to proximity to the hot bits. Does appear to be hard work to keep this thing cool when idling though. Haven't put the water wetter in yet, but am using some red ready mix coolant from Comma which allegedly improves cooling (or maybe just raises boiling point). Next move is switch to H2O + WW to see if it is better. Stig, have you removed thermostat to remove the flow restriction? (not ideal I know). Or maybe need gruntier fans? Cooling seems OK when on the move.
Cooling fine on the move.
Have the uprated rad.
Have a 650-700rpm idle.
However, my water temp sender is situated in a relatively dead area at the top of the block in the supercharger manifold. I've been advised that this area doesn't get as much water flow as the rest of the block so maybe it's over-reading?.
I might put the sender back into the water pump to see if it's any lower.
Either way, the fans come on and stay on, so don't appear to be able to get rid of enough heat to bring the temperatures down??
Have the uprated rad.
Have a 650-700rpm idle.
However, my water temp sender is situated in a relatively dead area at the top of the block in the supercharger manifold. I've been advised that this area doesn't get as much water flow as the rest of the block so maybe it's over-reading?.
I might put the sender back into the water pump to see if it's any lower.
Either way, the fans come on and stay on, so don't appear to be able to get rid of enough heat to bring the temperatures down??
Don't think that'll help gdr as they're a big as they get. Any larger and you wouldn't be able to shut the bonnet.
Have spoken to the factory who expressed concern about the lagging that I have around the coolant pipes which run along the cockpit sides. Will be removing this to see if it makes any difference (will not be a happy bunny if it doesn't, as I can't put it back on again once it's off and it's not bloody cheap!!).
Have spoken to the factory who expressed concern about the lagging that I have around the coolant pipes which run along the cockpit sides. Will be removing this to see if it makes any difference (will not be a happy bunny if it doesn't, as I can't put it back on again once it's off and it's not bloody cheap!!).
Not bigger fans, but faster motor (more amps) or more efficient vanes - dunno if such things exist.
The other thing I was wondering about was the pulley size on the water pump. Could you change the gearing to get some more flow at low revs? Will eat some HP at high revs but I suspect you have some to spare. The racing type pumps I believe are low geared for opposite reason, but not ideal for sitting in traffic.
The other thing I was wondering about was the pulley size on the water pump. Could you change the gearing to get some more flow at low revs? Will eat some HP at high revs but I suspect you have some to spare. The racing type pumps I believe are low geared for opposite reason, but not ideal for sitting in traffic.
Stig
I hark back to an earlier comment when you were posting about the idle speed changing with the back shut. It may help to have one or more radiator type fans installed in the rear grill. this would help pull air in to the side grills, improving the oil cooling (the highest disipator of heat in an engine) and generally reducing the temperature in the engine bay. This may be enough to make the difference. It is also relativly easy to achieve bearing in mind that there is little more you can do up front to improve cooling there.
Steve
I hark back to an earlier comment when you were posting about the idle speed changing with the back shut. It may help to have one or more radiator type fans installed in the rear grill. this would help pull air in to the side grills, improving the oil cooling (the highest disipator of heat in an engine) and generally reducing the temperature in the engine bay. This may be enough to make the difference. It is also relativly easy to achieve bearing in mind that there is little more you can do up front to improve cooling there.
Steve
Steve : had a look at this but came to the conclusion that the fans would just suck air from around the gearbox and not from high up. Path of least resistance and all that. The supercharger accounts for a lot of space compared to a normal installation so there's not a great deal of space for air to move around in. Am considering a fan on the oil cooler rad which will help things a fair bit.
Dave : Definitely working the right way round!!!
Certainly exhausting more air from the canopy will help, but even with it open, the fans can't get the temp below 95 degs.
What about if I fit an oil cooler fan and run it with the aircon? This will not only help cool the oil, but will effectively ram air into the engine bay whilst stationary?
Dave : Definitely working the right way round!!!
Certainly exhausting more air from the canopy will help, but even with it open, the fans can't get the temp below 95 degs.
What about if I fit an oil cooler fan and run it with the aircon? This will not only help cool the oil, but will effectively ram air into the engine bay whilst stationary?
Chris:
I have experienced the same trouble at early runs. After a lot of job looking for the solution these are the points that I have changed and now it goes OK.
1.- Usually, people trends to fix iddle at low speeds because everybody likes smooth iddle. Most of our modified V8´s have rough iddle. I fixed mine at 1000-1100 rpm and the problem started to go better.
2.- I replaced the thermostat with a 75º unit (much better) close but "not cigar".
3.- More searching.....The water pump was wrong. I purchased a high speed pump not good for "daily" use these pumps work fine with little power loss but over 2500 rpm. Then I replaced it for a Stewart Components unit and one of their "tuned" thermostats and now things are going perfect.
4.- I have changed the fan thermo switch for a lower unit and fit a manual switch for hard traffic. No problems.......(at this moment)
Hope this can help.
Be prepared for Le Mans previsions say sun and hot..
Cheers, Javier
I have experienced the same trouble at early runs. After a lot of job looking for the solution these are the points that I have changed and now it goes OK.
1.- Usually, people trends to fix iddle at low speeds because everybody likes smooth iddle. Most of our modified V8´s have rough iddle. I fixed mine at 1000-1100 rpm and the problem started to go better.
2.- I replaced the thermostat with a 75º unit (much better) close but "not cigar".
3.- More searching.....The water pump was wrong. I purchased a high speed pump not good for "daily" use these pumps work fine with little power loss but over 2500 rpm. Then I replaced it for a Stewart Components unit and one of their "tuned" thermostats and now things are going perfect.
4.- I have changed the fan thermo switch for a lower unit and fit a manual switch for hard traffic. No problems.......(at this moment)
Hope this can help.
Be prepared for Le Mans previsions say sun and hot..
Cheers, Javier
I could come round and cut some holes for you. I'm good at that 
)
As you know, I had quite a bit of trouble with getting rid of heat on my car, so here is the benefit of my experience of a season fighting against engine temperature.
The first thing I would do is to move the temp sensor to a position where you can be sure that you're getting an accurate temperature. There's no point going to all this trouble if there isn't actually a problem. Remember, at low engine speeds there won't be an awful lot of water movement around the engine anyway, so if you're measuring temp in a low flow area, it'll increase the problem.
Anyway. On with the solutions.....
The fan on the oil cooler is a very good idea, if you're getting the overheating under load (as I was). However, if your oil temp is staying within reasonable limits on tickeover, the cooling effect won't be great (the oil pump works at a slower speed at tickover, just like the water pump. Probably worth fitting one anyway though, as it might come in handy on the track.
As your problem is when you're stationary, there isn't going to be any point in fitting additional ducting (unless you always stop facing into a strong headwind
).
Your rad is going to be fine. If it wasn't, it would be when you're monstering it that you would get the problems.
One thing to consider is an option that I know we discussed before. Fitting an electric water pump in parallel with the mechanical one. You could run it from the same thermostat that the fans run on, so that it only comes on when you need it. That will give you the increased flow at tickover, and not have any power sapping side effects when you're giving it full welly.
James
) As you know, I had quite a bit of trouble with getting rid of heat on my car, so here is the benefit of my experience of a season fighting against engine temperature.
The first thing I would do is to move the temp sensor to a position where you can be sure that you're getting an accurate temperature. There's no point going to all this trouble if there isn't actually a problem. Remember, at low engine speeds there won't be an awful lot of water movement around the engine anyway, so if you're measuring temp in a low flow area, it'll increase the problem.
Anyway. On with the solutions.....
The fan on the oil cooler is a very good idea, if you're getting the overheating under load (as I was). However, if your oil temp is staying within reasonable limits on tickeover, the cooling effect won't be great (the oil pump works at a slower speed at tickover, just like the water pump. Probably worth fitting one anyway though, as it might come in handy on the track.
As your problem is when you're stationary, there isn't going to be any point in fitting additional ducting (unless you always stop facing into a strong headwind
). Your rad is going to be fine. If it wasn't, it would be when you're monstering it that you would get the problems.
One thing to consider is an option that I know we discussed before. Fitting an electric water pump in parallel with the mechanical one. You could run it from the same thermostat that the fans run on, so that it only comes on when you need it. That will give you the increased flow at tickover, and not have any power sapping side effects when you're giving it full welly.
James
Thanks Slappy. Intersting reading. Moreso after I had read this on the Steward Components website:
Thicker radiators do have slightly more airflow resistance than thinner radiators but the difference is minimal. A 4" radiator has only approximately 10% more airflow resistance than a 2" radiator.
In past years, hot rodders and racers would sometimes install a thicker radiator and actually notice decreased cooling. They erroneously came to the conclusion that the air could not flow adequately through the thick radiator, and therefore became fully heat-saturated before exiting the rear of the radiator core. The actual explanation for the decreased cooling was not the air flow, but the coolant flow. The older radiators used the narrow tube design with larger cross section. Coolant must flow through a radiator tube at a velocity adequate to create turbulence.
The turbulence allows the water in the center of the tube to be forced against the outside of the tube, which allows for better thermal transfer between the coolant and the tube surface. The coolant velocity actually decreases, and subsequently its ability to create the required turbulence, in direct relation to the increase in thickness. If the thickness of the core is doubled, the coolant velocity is halved. Modern radiators, using wide tubes and less cross section area, require less velocity to achieve optimum thermal transfer. The older radiators benefited from baffling inside the tanks and forcing the coolant through a serpentine configuration. This increased velocity and thus the required turbulence was restored.
Radiators with a higher number of fins will cool better than a comparable radiator with less fins, assuming it is clean. However, a higher fin count is very difficult to keep clean. Determining the best compromise depends on the actual conditions of operation.
Double pass radiators require 16x more pressure to flow the same volume of coolant through them, as compared to a single pass radiator. Triple pass radiators require 64x more pressure to maintain the same volume. Automotive water pumps are a centrifugal design, not positive displacement, so with a double pass radiator, the pressure is doubled and flow is reduced by approximately 33%. Modern radiator designs, using wide/thin cross sections tubes, seldom benefit from multiple pass configurations. The decrease in flow caused by multiple passes offsets any benefits of a high-flow water pump.
Gross flow radiators are superior to upright radiators because the radiator cap is positioned on the low pressure (suction) side of the system. This prevents the pressure created by a high-flow water pump from forcing coolant past the radiator cap at high RPM. As mentioned in the radiator cap section, an upright radiator should be equipped with radiator cap with the highest pressure rating recommended by the manufacturer. The system will still force coolant past the cap at sustained high RPM.
>So, as I'm running with the thick rad, it doesn't seem unreasonable to assume that an boost to the flow rate would help matters? I have to say, I was surprised at just how cool (well, not hot) the air was that was being blown back by the fans. This endorses the view that there's not enough thermal transfer taking place in the rad.
Thicker radiators do have slightly more airflow resistance than thinner radiators but the difference is minimal. A 4" radiator has only approximately 10% more airflow resistance than a 2" radiator.
In past years, hot rodders and racers would sometimes install a thicker radiator and actually notice decreased cooling. They erroneously came to the conclusion that the air could not flow adequately through the thick radiator, and therefore became fully heat-saturated before exiting the rear of the radiator core. The actual explanation for the decreased cooling was not the air flow, but the coolant flow. The older radiators used the narrow tube design with larger cross section. Coolant must flow through a radiator tube at a velocity adequate to create turbulence.
The turbulence allows the water in the center of the tube to be forced against the outside of the tube, which allows for better thermal transfer between the coolant and the tube surface. The coolant velocity actually decreases, and subsequently its ability to create the required turbulence, in direct relation to the increase in thickness. If the thickness of the core is doubled, the coolant velocity is halved. Modern radiators, using wide tubes and less cross section area, require less velocity to achieve optimum thermal transfer. The older radiators benefited from baffling inside the tanks and forcing the coolant through a serpentine configuration. This increased velocity and thus the required turbulence was restored.
Radiators with a higher number of fins will cool better than a comparable radiator with less fins, assuming it is clean. However, a higher fin count is very difficult to keep clean. Determining the best compromise depends on the actual conditions of operation.
Double pass radiators require 16x more pressure to flow the same volume of coolant through them, as compared to a single pass radiator. Triple pass radiators require 64x more pressure to maintain the same volume. Automotive water pumps are a centrifugal design, not positive displacement, so with a double pass radiator, the pressure is doubled and flow is reduced by approximately 33%. Modern radiator designs, using wide/thin cross sections tubes, seldom benefit from multiple pass configurations. The decrease in flow caused by multiple passes offsets any benefits of a high-flow water pump.
Gross flow radiators are superior to upright radiators because the radiator cap is positioned on the low pressure (suction) side of the system. This prevents the pressure created by a high-flow water pump from forcing coolant past the radiator cap at high RPM. As mentioned in the radiator cap section, an upright radiator should be equipped with radiator cap with the highest pressure rating recommended by the manufacturer. The system will still force coolant past the cap at sustained high RPM.
>So, as I'm running with the thick rad, it doesn't seem unreasonable to assume that an boost to the flow rate would help matters? I have to say, I was surprised at just how cool (well, not hot) the air was that was being blown back by the fans. This endorses the view that there's not enough thermal transfer taking place in the rad.
Stig
That electric pump sounds the way forward.
I think you want to try that before taking off all that insulation cos as you say there's no going back.
Have you spoken to the suppliers about putting the new pump in line with the mechanical? Can't help thinking they will restrict each other.
I agree with your 'line of least resistance' reply and agree that running a fan on the oil cooler coupled with the fan on the A/C.
Steve
That electric pump sounds the way forward.
I think you want to try that before taking off all that insulation cos as you say there's no going back.
Have you spoken to the suppliers about putting the new pump in line with the mechanical? Can't help thinking they will restrict each other.
I agree with your 'line of least resistance' reply and agree that running a fan on the oil cooler coupled with the fan on the A/C.
Steve
There are a couple of manufacturers of electric pumps that are a direct fit replacement for the SBC mechanical pump - one of these would be a logical thing to try, not the easiest thing to fit with the engine in situ though.
Don't be tempted by any of the schemes for junking the thermostat and controlling the temperature by altering the speed of coolant flow - just run the electric pump at full tilt (around 50-70 liters/min) and retain the mechanical thermostat and bypass circuits in place. If you are feeling paranoid then add a current sensor to the circuit to check that the pump is still running - imho reliability is not an issue.
Don't be tempted by any of the schemes for junking the thermostat and controlling the temperature by altering the speed of coolant flow - just run the electric pump at full tilt (around 50-70 liters/min) and retain the mechanical thermostat and bypass circuits in place. If you are feeling paranoid then add a current sensor to the circuit to check that the pump is still running - imho reliability is not an issue.
Stig I have 11" Tripac Fans (the factory use 10" Tripac the same make) they flow about 500CFM more. I did not have to modifie the front bonnet at all.
Fitment of temp sender :- do not put the sender in the water pump as you are not measuing the engine temp but the returning water temp from the rad, the ideal place is in the Cylinder heads as that is where the most damage happens if overheating occurs. As to the inlet manifold for the Charger I'm not sure wether overheating would be worse for the heads or the charger, but I know that boiling of the water causes air pockets in the heads and then you don't want to know...
Question do you have a High flow water pump ??
Answer I would fit a CSI electric pump just for piece of mind, and if it's getting alittle hot turn the engine off and leave the pump on, ploblem solved for traffic Jams.
Had the same problem in my GT40, the electric pump was great if the only problem you have is in traffic.
Good luck Mate.
>> Edited by GTRCLIVE on Tuesday 20th May 19:58
Fitment of temp sender :- do not put the sender in the water pump as you are not measuing the engine temp but the returning water temp from the rad, the ideal place is in the Cylinder heads as that is where the most damage happens if overheating occurs. As to the inlet manifold for the Charger I'm not sure wether overheating would be worse for the heads or the charger, but I know that boiling of the water causes air pockets in the heads and then you don't want to know...
Question do you have a High flow water pump ??
Answer I would fit a CSI electric pump just for piece of mind, and if it's getting alittle hot turn the engine off and leave the pump on, ploblem solved for traffic Jams.
Had the same problem in my GT40, the electric pump was great if the only problem you have is in traffic.
Good luck Mate.
>> Edited by GTRCLIVE on Tuesday 20th May 19:58
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