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.
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!!).
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?
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.
Many thanks for all your replies. It's good to know that the forum's there as an invaluable source of collective knowledge!
Spoke to Real Steel who supply the CSI electric pumps, as well as Pete Master Motorsport who are running the GT Ultima. Incidently, they run two electric pumps, a send and a return and have had no problems to date. The length of the pipes compounds the problem - especially if you've insulated them like I have!
Want to avoid replacing the mechanical pump if possible and Stewart Components do an in-line 'booster' that they claim increases flow by 300%!
Sounds as if it's the way to go.
I think it will probably end up being a case of being several small solutions rather than one sure-all.
Anyway, it gives me something to write about
Thanks again all
Spoke to Real Steel who supply the CSI electric pumps, as well as Pete Master Motorsport who are running the GT Ultima. Incidently, they run two electric pumps, a send and a return and have had no problems to date. The length of the pipes compounds the problem - especially if you've insulated them like I have!
Want to avoid replacing the mechanical pump if possible and Stewart Components do an in-line 'booster' that they claim increases flow by 300%!
Sounds as if it's the way to go.
I think it will probably end up being a case of being several small solutions rather than one sure-all.
Anyway, it gives me something to write about
Thanks again all
ultimapaul said:
Stig - How long have you been letting the car sit there for before the temp rises to uncomfortable numbers? And in what ambient temp?
I had a problem at Le Mans last year where we sat in 25-30deg heat for nearly an hour, with the tick-over set at about 1050!
I found that fuel evaporation was a bigger problem before the car finally boiled. I had to keep re-starting after it kept stalling and I was more worried about running the battery flat, it became increasingly hard to start.
I'm hoping some water wetter will help and turning the tick-over down a tad.
How easy would an over-ride switch be to install? Any chance of a schematic of some one? I believe that having the fans cut in earlier would be a big help!
Paul
Hi mate,
The car is ticking over at about 700rpm with a smooth idle. Will richen it up a bit to make sure it's not too lean (but I'm sure it isn't because it was running mega-rich before and did the same thing)
I'd guess that it takes about 10 mins for the temp to rise to an uncomfortable level from normal operating temp which is about 82 degs.
Already have a fan override fitted. Testing has been done with fans cutting in of their own accord. Will try with fans overridden to see if I can keep it cool before it gets beyond their control. There's a wire pair in place on the loom already, just for this purpose.
Emailed Gail at AS who reckons that I already have a hi-flow pump 'none better' in his words. So leccy pump may not help (but the Stewart Components in-line booster seems like a good idea).
The search continues.....
>> Edited by Stig (moderator) on Wednesday 21st May 10:20
k wright said: Probably not going to be well received but: cover the exhaust headers and mufflers with nomex insulation. This has been very beneficial on my other cars with over-heating problems. It is a shame to cover all that perfect stainless with nomex cloth but may necessary. Wouldn't reccomend the tape, would recommend the exhaust sleeving sold by Thermo Tec.
Good point. Funnily enough I've got a good supply of the tape running along the coolant pipes ready for removal!!!
ultimaandy said: CJ
IMHO your problem is the rather large thing on top of your engine.
My advice would be to contact that guy from the US with the twin turbo set up as he must have had to deal with this problem.
I have to say (and will get hate mail for this) I agree with the factory and didn't lag my rad pipes but instead lagged the cockpit panels. It works on my car but I obviously don't have your heat exchanger
another alternative would be to fit a bigger oil cooler with a temp sensor. The factory demo car has(had?) a larger one fitted but they covered half of it because quote "it was too efficient and was running to cold".
Worth a thought.
Andy
LOL! Don't worry, hindsight is a wonderful thing and I did go a bit mad with the insulation thing. Still, it was in reaction to owners bemoaning high cockpit temps. so it's six of one and half a dozen of the other. Boil the occupants or boil the engine
I have also got insulation on the cockpit panels, luggage bins and heater pipes so I think I'm pretty well covered!
However, whilst the pipes will radiate a couple of degrees. What then? There's no airflow through the sidepods (especially when stationery or in slow traffic) so once the ambient temperature goes up in the sidepods, I wouldn't have thought they'd help much?
Anyway, I'm going to try a few things out and see where that gets me before resorting to more drastic measures.
GreenV8S said:
Stig said: The car is ticking over at about 700rpm with a smooth idle.
Ordinary mechanical water pumps are very speed sensitive and pump almost no water at low RPM. If your engine is overheating in traffic you may find it helps (or at least delays the inevitable) if you raise the revs to 1500 rpm or so. In conventional systems this also reduces the pressure in the top hose so postpones any boil-over.
Pete,
The engine has a high-flow pump fitted but I agree about the low rpm efficiency. I tried raising the revs, but it was a law of diminishing returns as the ratio of heat generated by the engine vs. heat dissapated stayed about the same.
The nett result was that the temperature crept up again.
Am angling towards fitting a secondary electric pump on the rad inlet which is switchable with my fan override switch. This should help maintain a decent flow rate (20-80 litres per min) and help create turbulence in the rad.
brammo said: As an alternative water pump device, we have had others use the Davies Craig unit, which is lightweight and easily slipped in line and even has a controller.
The irony of many of the aftermarket waterpumps like the the Stewart is that they are designed for more RPMS of race engines, rather than slow speed idle cooling. Though AS has the best their is, that will not solve your issue of moving water at idle to the exchanger in any quanity to let the electric fan do its work.
Came to the same conclusion Craig and have gone ahead and ordered the Davies Craig EWP.
Will run this in series with the existing pump and it will come on with my fan override switch (as well as anytime the fans are running).
In addition (because I always err on the side of caution!), I added an 8" Profan for the oil cooler. I may run this from a seperate switch, but it should aid the engine idle temp, as well as drawing fresh air (slightly warmed through the oil cooler) into the engine bay.
Fingers crossed!
GreenV8S said:
Stig said:I tried raising the revs, but it was a law of diminishing returns as the ratio of heat generated by the engine vs. heat dissapated stayed about the same.
In theory that shouldn't be the case - the heat output only varies a little bit with revs and a bit more with torque, while the water flow varies very dramatically at low revs. Might suggest that low water flow rate is not your problem and you need more air, or colder air, going through the radiator. Is all the air going through the rad cold fresh air, or is there any possibility of air recirculation when stationary?
Well, obviously theory and practical application don't always agree!
The air is drawn through the rad with two fans which account for about 90% of the total radiator surface area.
The air is drawn from the front scoop and deflected up and over the bonnet. Recirculation in that environment was very unlikely. As I mentioned before, I was actually surprised at how warm (ie not hot) the air was.
The radiator itself is fully ducted and was drawing air from inside the workshop on a reasonably cool day.
Put it this way, it wasn't nearly as hot as being stuck in traffic in the centre of France!
brammo said: Stig,
Would love to see some photos of the DC motor install and hope that does it. Fan on the oil cooler is probably a good idea anyway. There are oil thermostats that will kick on only when the oil temp on the engine side reaches the appropriate temperature, as you dont want the car engine to warm up too slowly! Mocal and a few other have units and have a simple wiring to turn on and off the fan.
Can point you to a part if needed.
Craig
Thanks Craig,
As I mentioned, I'm only going to run the oil cooler manually as oil temp has been fine when the car is on the move.
The EWP mod will be covered in gory detail on the website. I swear I'm only getting these issues as motivation to keep updating it
GTRCLIVE said: The Davis Craig pump is what i fitted and it's cheapest at Real Steal, was only £90 2years ago. Ripspeed wanted £130 at the time.
I fitted it down by the radiator and had it on a switch as well, the controler they try and sell you does not work very well for our V8's so don't be tempted as it's a waste of money.
Have fun...
Real Steel don't sell them any more. They only do the CSI pumps which are about 250 but are direct replacements for the mech pump.
Not using a controller as I'm wiring it to come on with my fan override.
ultiman said: Like Ultimapaul, I suffered overheating at Le Mans last year and in convoy with Paul and we both hit 115 f at the same time and simultaneously decided enough was enough. We were advised to turn down the idle speed to about 800 which we both did and no longer suffered severe overheating that weekend. The engine water temp still remained higher than I was prepared to accept so I have since fitted a fan over the oil cooler which comes on when the main fans do along with an over ride switch to bring the fans in early in traffic. This dealt with all but the most extreme situations.
The oil cooler fan draws a fair amount of air through the side vent to the extent that it will hold a ten Euro note to the side of the grill. The other advantage is that it helps keep down the under bonnet air temp which builds up. I have had no further problems but also looked at the Davies Craig unit, ordering one from Demon Tweeks. The pump was far too small and the inlet and outlet pipes about 15mm in diameter. I sent it back. Reading the above, I assume there are better ones. Any recommendations? (I am going for the belt and braces approach).
By the way Stig, don’t remove that lagging from the flow and return pipes. When I built my car there was no recommendation to lag these so I didn’t. A retro fit requires long rubber arms and a lot of luck. Without this lagging your air con will fight a loosing battle with this unintentional cockpit heater system. OK in winter but no fun in hot climates as passengers rarely see the amusing side after a few hours. I have an air temp gauge in the car which has hit 70 C in the past, such is the greenhouse effect…..
Seems like there's a pattern forming here eh!
Removing the lagging is a last resort (as it's a pain and was put there for the reasons you describe). Hence the other 'solutions'.
I may never find out what effect unlagging them will have, so can't really quantify the cooling effect they have on the system. There's now another supercharged car out there (was almost finished at the factory open day) so would be interesting to hear their experiences first hand - but have no contact info for the chap who built it despite meeting him there.
As I mentioned, I've also gone for 'belt-and-braces' (love that expression) and am fitting an 8" ProFan to the oil cooler to pull cool air into the engine bay.
The EWP has been updated for 2003 to provide 18% more flow (allegedly). Regarding the inlet/outlet sizes, well, as long as it flows what they claim then it's irrelevant. As you know, it comes with a load of adaptors for the 38mm ID silicon hoses that the factory supply.
ultiman said: Stig you say "The EWP has been updated for 2003 to provide 18% more flow (allegedly). Regarding the inlet/outlet sizes, well, as long as it flows what they claim then it's irrelevant. As you know, it comes with a load of adaptors for the 38mm ID silicon hoses that the factory supply."
The pump l recieved had no possibility of conversion to 38mm pipes, in fact the body of the pump was only just about that. l spoke to the factory who had tried this option and they confirmed my concerns that it restricted flow, not enhanced it. Have others found something bigger and better as l am keen to finalise my cooling quest with something effective.
I've got the pump sat in front of me. The inlet/outlet are actually 27mm and it comes with 4 adaptors for larger ID pipes. I emailed Davies Craig expressing concern that the pump would restrict flow as the revs increased (and therefore the mechanical pump starts working) and their MD responded saying that it would be fine when installed in series. If you have a look at the technical research on their site you'll see that beyond a threshold at higher revs, increased flow makes no difference.
At the end of the day, there's so much contradictory advice that the only way of finding out for sure is to try it. If it makes no difference (or is worse!), then c'est la vie. I'll put it on my race car instead and will have to look for a solution elsewhere.
At the end of the day, it's hard to compare with other Ultima's because of the supercharger (more to do with physical space that it takes up in the engine bay rather than it's thermal properties).
adequatespeed said: The plastic pump is totlly unsuitable for big engines
I suggest (as before) you try the CSI pump
www.csiperformance.com/water_pump3.html
Why's that then Mark as pretty much every review of the EWP that I've seen says otherwise? The product was developed primarily for 3.9L V6's but was also tested with a 5.0 V8.
See here: www.daviescraig.com.au/trade.html
The CSI is still an option and (as you know) would replace the existing mechanical pump. However, this way I've got one pump backing the other up in case of failure.
We shall see
srreck said:
Stig said:
adequatespeed said: The plastic pump is totlly unsuitable for big engines
I suggest (as before) you try the CSI pump
www.csiperformance.com/water_pump3.html
Why's that then Mark as pretty much every review of the EWP that I've seen says otherwise? The product was developed primarily for 3.9L V6's but was also tested with a 5.0 V8.
See here: www.daviescraig.com.au/trade.html
The CSI is still an option and (as you know) would replace the existing mechanical pump. However, this way I've got one pump backing the other up in case of failure.
We shall see
Chris:
I ordered the CSI too. Look at the 925 model. It is a remote unit which you can fit inline.
Gah! Why didn't I spot that before. Thanks Javier - just need to find a supplier in the UK!
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