The reason that you are outside of the design limits or at least at the high side of them is that you are making more HP. More fuel is being consumed creating more HP and more waste heat. This is a mathematical relation. There is always a percentage of fuel that is not converted to HP and is lost as heat. More fuel, more heat. If you were not generating additional heat with the additional HP, you would have created a super efficient, never before achieved engineering miracle.

The designers of the car built a cooling capacity based upon usual load, peak load for the usual (passenger car, non-competition use) amount of time and reserve capacity. To explain, the car is driven at European speed limits for a sustained amount of time, at expected ambient temperatures, in traffic stop and go, accelerated from stops to highway speed, passing, hill climbing, etc. The reserve capacity could be an hour on a winding road uphill with higher RPM, very hot climate and city traffic for a sustained period of time. The manufacturers are smart enough now to build in the reserve cooling capacity due to different markets such as Mexico and hard driving and traffic. They do not however automatically build in enough capacity for competition where peak load is for prolonged periods of time. Your modifications have worked out ok as you do not generate peak HP for a significant amount of time. Most engines are not used this way. Combine a temperate climate and the lack of competition and you are safe. Other than the acceleration benefits, starting and passing situations, you are not using the full capacity of your mods for a sustained amount of time. If you start using the full HP of the engine doing something like road racing, hill climbing or winding roads, you will notice that it is running hotter and you come closer to reaching the high limit where the cooling system cannot keep up with the heat lost by the engine. Already you are seeing a slightly higher temperature under some conditions; this is the warning. Since I have not done the calculations, I am assuming that Jaguar's engineers did a good thing and built a lot of extra reserve capacity. I torture tested my car during a heat wave with high humidity in traffic, very steep hills, AC on full, you name it as I was taking a trip and did not want to find out the hard way. The temp was perfect even with high RPM sustained. This tells me that there is a lot of reserve capacity built in to the XK8 model. However, I am at stock HP; you are more than double and the waste heat increases accordingly. Go find a track and run for an hour at high speed where you are high in the power band and tell me how it works out. I do not feel like doing the math, but if you know the cooling capacity of the system, you can run the numbers from your engine output. There is a point where you will exceed the cooling capacity if you either calculate it or test it, guaranteed. The reason that it works out is that the system has a chance to catch up when you are not at high HP output such as reaching cruising speed, downhill or light traffic. Those twin screws are more often than not doing not much.

This issue is seen when some cars are used for track days or other competition even in stock form as the designers never intended this use. Many times a larger capacity radiator is required for this use. My E-Type needed a larger capacity radiator as the car could only cool itself with cruising airflow. Traffic and high temp and humidity were not good for it. There was not enough reserve capacity built in from the start. The better radiator made it a very reliable car.

Regarding your hose burst concern as opposed to something else. When a hose bursts, it is usually noticeable and early actionable. A low pressure drain from a failed hose or connection might go unnoticed and the loss of cooling fluid might defeat the temperature sensor reading. This is a really outside discussion and the best thing is to replace old and worn stuff before it breaks.

 

I fully agree, it’s also one of the reasons I always asked twin-screw users on how much they want in power and how they want to use it. For street you have much more room, but anything beyond more work on cooling/lowering power would be required for longevity.

There is indeed a lot of capacity in the cooling system, more than I expected actually, but not unlimited pending the conditions. Worst are the low speed conditions, where you don’t have the airflow to support transferring heat away from the system.

To increase the airflow I have already changed my stock bumper to the later version (from 2005 iirc), but if you would be starting racing, you better also add a good splitter to increase the flow even more. Racing is not my intention, and as said if I would then I would lower the power as I don’t believe there is much reserve in the engine for these long sustained power levels, at least I am not willing to try ;-).

Next steps would probably be a bigger oil cooler carefully placed and maybe setting up a separate cooling system for the gearbox (not sure as you would need extra space somewhere), and ideally an electric cooling pump, that can take advantage of low rpm speed amongst others.

But for now with my driving conditions I am not reaching the max capacity of the cooling system, and have the added benefits as mentioned from evans.

With regards to leaks, maybe relatively new hoses will give you some room to maneuver your car to the side of the street, but the older they get the bigger the chance of more dramtics bursts, but your still stranded.

It will be very hard to mis any leak, as said I had some previous leaks, and you either see a very small puddle, or you smell it. You could always check the coolant level every other 6 months or so.

 

It is probably safe to assume that you have added something like Real Gauge with the oil pressure option. Another thing to consider would be an oil temperature monitor along with one for the trans. Years ago, I saw one that inserted into the engine oil dipstick tube, talk about easy. It only had to be removed to check the oil level.

The reason is that your oil temp might be fine in both engine and trans and the extra effort and expense are not needed. You can use the car, explore new limits or activities and if you see something starting to move out of acceptable range, you can now make a decision. With modern synthetic engine oils in the 30 viscosity performance extends into higher temperatures. A simple web search or telephone call to a good Amsoil rep will get you the temperature service range. Actually if you find you car going higher than that acceptable range for the oil, which would be unlikely, it might be as simple as raising the upper viscosity to 40.

Electric cooling pumps are used by a lot of competitive cars both track and drag. The reasons are to prevent HP loss from the drive belts and to keep temp from becoming too low. Many engines including ours take a long time to get fully warmed. If you are using an oil pressure gauge or something more direct such as an oil temp gauge, you will notice that it takes a long time for the oil to get to full temperature.

 

So far I haven’t reached the limits from both engine oil/gearbox oil, and gearbox oil can be monitored with the Jaguar IDS tool. I had planned to do once the oil temp/pressure, but it never materialized, and is so far not on my planning. Maybe when I have time to get the cam timing to an optimal state, I may push for a new dyno run as there is more power left to be had, but after so many years constantly pioneering in the top power range I am more than happy if someone else takes over the frontier ;-).

For oil I normally only use M1 04w0, and in the summer actually use Castrol 10ws60, also for just in case.

Am not so sure if you gain much HP with an electrical pump top end wise, there it needs to run full power, but for fuel economics it could be interesting as it only runs when you need flow. With a thermostat less setup (so pwm pump control based on temp of course) you increase the flow capabilities and as mentioned it can work on low rpm range areas where still cooling is required. Its not on the list though to do.

I liked the CWA400 pump (good head capabilities) with this controller I recently stumbled upon http://www.tecomotive.com/en/products/tinycwa.html

 

Real world test using electric coolant pumps show a new savings of ~1HP, not worth the effort.

 

Everything depends on the pumps/original design itself, but I take it our more modern cars have better designed pumps that have less power consumption.
However in a thermostat less system there is less head, thus the electrical pump has to draw less amps. Next to that with good conditions (ie cold outside and good airflow) you also need a little less flow again for the same cooling capacity, so again less amps required, and with that added up I would expect to see some better gains.

But I agree, that alone would not be the reason to swap to an electrical pump.

 

the one thing that i would caution is that too much flow rate can defeat the cooling effect of the radiator and electric pumps are used for control in many cases.

i am curious as to your oil selections. the upper limit of 60 viscosity even in summer seems a little high with modern synthetics and can cost you HP and cause wear.

 

The key is understanding how much the stock belt driven pumps draw- this number is far less than most people are led to believe.

 

That's what I like about the electric (controlled) pumps, flow is controlled based on needs.

Although oil might be better for another thread and it’s not something I would recommend, it was also temperature related as the viscosity is direct related to the temp, and at higher temps it comes closer to the 40 weight. As there is plenty of power, I am not concerned it will cost me some, and I never use full power when the oil isn’t warm enough. It was/(is) a pure guess to get as much protection for my particular engine. I wish I had the bearing clearances from the Aston Martin AMV8 as that one uses 60 weight oil, and it could give me a bit more insight.

 

This is so interesting I am still debating whether waterless or Hoses, or maybe even both?

 

The waterless has a lot going for it and will definitely do you no harm. I would still do the hoses for insurance. Taking everything apart will make it easier to get all of the existing coolant out anyway.

 

I can see the 40, especially if you cannot maintain the minimum pressure at idle when at highest operating temperature, but 60 is way too high for our tolerances. Perhaps if you were using a conventional 20-50 oil it would be ok to be above 40. The Aston Martin might have much higher temperatures and greater clearances and uses a broad range product to limit startup issues. i would check oil temp as it does not get as hot as you might think even with mods. Oil is also a coolant and higher viscosity limits flow reducing this benefit.

 

The 5w40 is within the recommended range from Jaguar, but hanks for the warning, it has been some time ago that I dug into oil weight/temp (some was based on BMW engines as well), will do it again.

 

That is why I recommended that as a top limit. They probably allow us to go that high for sustained hot climate and performance use. Perhaps if oil consumption gets a little high. 60 is just crazy thick; cannot imagine you getting the engine oil that hot. It is increased flow rate that provides better parts separation and flow decreases with viscosity.

It would be great to find that dipstick oil temp setup again; it looked to be very well engineered.

 

Well, assuming the oil temps would be about 10c higher than normal (considering my setup with the amount of power and evans), the difference isn’t that much anymore. Below some average figures:
5w40 at 80c has a viscosity of 23.48 whereas 10w60 at 90c 30,13.

But without common engine temp data and those of mine it just stays my guess of course. I would be interested in that dipstick if you find it again.

 

I have used Evans coolant for four years with absolutely no issues whatsoever. Before I installed Evans I hooked up a ScanGauge to measure coolant temperature. Normal operating temperature was about 200F more or less. With Evans no material temperature changes.
I too was concerned about the lesser specific heat with Evans compared to conventional coolants, hence my informal A/B testing.
In my opinion, the Jaguar cooling system components appear to be more "delicate" than typical American/Asian. Hence, a waterless system without pressure will enhance the life of coolant seals and hoses.

 

Of course not. The thermostat regulates coolant temps accordingly, no different than HVAC in a house.

The problem is that the system must now work harder to shed heat leaving a reduced 'margin', all induced by filling the system with a produuct with known inferior heat rejection properties.

The premise that engine hoses and seals will last longer despite the acknowledged unchanged volume of heat under the hood is quite a stretch. I think of time, heat and pressure, the two former factors are a bigger concern.

 

Just a thought, since Evans has a known thermal transfer deficiency is there any danger of this happening between the engine structure, the coolant and the temperature sensor resulting in incorrect reading at the gauge?
In other words can the head be hot, the coolant not so hot and the sensor a little cooler again all because of less efficient transfer.

 

There was nothing out of the ordinary when I measured my cylinder head temps with Evans, but I didn’t have any reference data from before I went to Evans so don’t know the difference. Actually with Evans you have a much wider temperature margin as it’s able to deal with hotspots and much higher temps then standard water/coolant based systems.

 

At the level of inefficiency inherent to waterless coolants like Evans it's not a practical concern.

It is an interesting thought though as efficiency drops a coolant would become more of an insulator than a transfer medium.