Assuming you have the engine undertray fitted, and the bonnet shut, how many minutes idling at standstill would it take to warm up the SC casing to thaw out frost accumulation?

 

It just took me a minute to figure out the complexities. I wrote it with the glass of ice water as a reference point for others. Until I thought about it that way I just couldn't get the idea through my head. I believed it but couldn't visualize the process.

Any thoughts on a turbo timer? They allow an engine to idle to cool down a turbo for a set amount of time. They should be ideal in this situation. There is usually a switch or something similar to disable it under normal (above 0 degree Fahrenheit) conditions. I would think 10 minutes at idle would equalize temps and avoid the whole situation. I just don't know if there is a universal one. These cars aren't exactly what you'd normally find such devices on.

 

We've yet to understand why letting the engine sit at idle would melt the ice but driving wouldn't.

I'm having a tough time imagining ice forming inside a hot, running engine in the first place.

 

In my mind it's the condensation like I was explaining above. When the engine isn't running it can then run down into the cylinders and freeze as the temps fall. I think letting it run at idle and not compressing the air in the supercharger will equalize the temps and get rid of the condensation.

 

The inside of the manifold when off-boost is not far from the ambient temperature. The manifold only warms up (and melts the ice) after the engine shuts off, or the engine idles at a standstill when incoming airflow is low and freezing air isn't bathing the underhood area.

Mike

 

Thousands of STRs were made yet none appear to suffer this. Odd, if it's really the explanation. Well, a lot more than odd.

The small amount of water vapour that can supposedly condense out and cause this... really? I don't see it.

 

One: Noodlearm; 2011 https://www.jaguarforums.com/forum/s...e8/#post911978

 

Agreed- but why would moisture accumulate on the surface in the first place? If the theory is true, then all sub-freezing surfaces exposed to air should accumulate moisture. It hasn't been above freezing here in a few months yet there's no accumulation on any surface.

In one of the examples above, the poster states that OAT was 3*F. Let's presume that there was approx. 60% relative humidity which is typical this time of year. For moisture to condense and appear, the surface would have to be chilled to -8F*. Given that the air passing through the supercharger is always warmer than ambient this lessens/eliminates chances that condensation will occur, not increase.

I'm still stumped.

We need to remember that the air here is extremely dry- the amount of suspended moisture is equivalent to that of a hot desert.

 

Mikey, you are getting snagged on the actual temps. I don't think it is that cut and dried when it comes to condensation.

If the outside air temp is 3 degrees F, then the moisture in the air is actually in the form of tiny ice crystals. But, as you pointed out, the moisture is still there, even in below freezing temps. Now, take this frozen air and run it through the SC...you now get warm air, and the ice crystals have become water vapor. As the water vapor moves back into a "relatively" colder duct and IC on the way to the engine valves, it will condense on the cold surfaces...becoming water, or ice if the duct is cold enough.

So, in very cold air, with every surface very cold...you get no ice or condensation. But, with very cold surfaces with warmer air, you get frost.

I fly the MD-80. At altitude we are flying in -56 degree C air, and the fuel is in the wings, getting super cooled. We land after 4 hours, and on a 95 degree day on the ground, we get frost on the wing surfaces from the super cooled wings condensing ice on the surface of the wings. This was a major problem for many years on the plane, as the frost (and sometimes clear ice) would break off during the next takeoff and trash the engines. Several planes barely made it back down safely with both engines damaged from the ice. All of these cases were during summer day temps. We eventually had to add heaters to the top of the wings...we still, to this day, get frost under the wings after a long flight. Luckily this frost does not damage the engines, though. The best engineers in the business did not forsee the possibility of ice on the wings. The reason is that the MD-80 was designed to fly long legs at high altitude, vs the original DC-9 only flew short hops in lower altitudes. The longer legs allowed the fuel to cool below freezing...which was never a problem before, although the basic plane design was over 20 years old with no problems!

Yesterday I flew into Detroit, with light snow and a ground temp of 21 degrees F. We got no ice on the wings. Why? Because the moisture in the air was frozen, and the wings were frozen. The condensation only works if the moisture is water vapor...not ice crystals. So, if you can visualize, the SC in the car sets the perfect condition for condensation and ice in the intake tract. It's pretty academic when, or how, it eventually works its way into the engine as water. If you have ice and water in the ducts...it is inevitable it will eventually end up in the engine.

 

That one is contentious, at the least.

 

cjd - yes, but it's sooo very different to the SC and its tubing etc.

 

And this is were we get caught going in circles.

If the supercharger is doing work and raising the temperature of the air enough to melt the ice crystals, this heat is also warming the inside surface of the supercharger. No ice will accumulate under these conditions.

If the supercharger is NOT doing work, then the air does not rise in temperature enough to melt it and again no ice accumulation.



Remember that we have the statement from the dealer in Minnesota about frost forming inside the supercharger itself, no mention of the intercooler being involved. If we bring the IC back into the mix and presume that there is water accumulation there, we're back at square one explaining how it gets into the engine after shutdown.

If we give up trying to explain why it's happening, we still don't have a sound method of prevention for the future. The moisture needs to be cleared before shutting down the engine. Letting it sit at idle is not going to produce any method of melting the ice and shifting the water that I can follow.

I can relate to your experience with flying and potential for engine damage from ice. I spent 30+ years at that company with the eagle inside the round blue and gold logo.

 

five things to remember, consider, extrapolate from:

1) adiabatic cooling

2) rate of airflow at idle versus cruise

3) rate of heat transfer

4) carburetor icing

5) the upstream side of the supercharger is at vacuum

history repeats itself ... learn from the past.

 

Thank you Plums.

Mikey, regardless what you write, it IS happening. Until someone sticks temp probes in these ducts, any talk about intake temps is entirely academic.

Jag, my latest example is exactly the same. The air has absolutely no idea whether it is in a duct or not. If warm air contacts a frozen surface, ice will accumulate. One can argue all day that the air is too hot from the blower, or the IC is too hot or...or...or... In the end, the fact remains that water is condensing in these engines.

I have given examples of water and ice condensing in carbs, air compressors, plane wings, air conditioning ducts. You guys are too busy staring at the dirt on the window to see what's right outside. I realize there are differences in the examples from an XJ8 intake...but quit nit picking the differences and look at the similarities instead!

It took a heating blanket to fix the wing...it takes more heat in an AC duct to blow the ice out...we need more heat in the intake tract to fix this issue too.

 

I was just thinking the same thing. It is happening. Instead of arguing about the science maybe we should collectively work on a solution. The people experiencing this need a solution not bickering.

 

I agree that a solution is what's required, but I believe what's been proposed so far will do nothing to avoid the problem and could possibly make it worse. Two possible locations for the ice have been proposed

1) inside the supercharger
2) inside the intercooler

Unfortunately the two explanations contradict and conflict. Makes it that much more to find a fix. To move forward, lets not argue how or why. Let's accept that it is.

I believe that stopping the engine and allow the ice to subsequently melt will just lead to more hydrolocking. The additional danger is that if the water is drawn into the engine from upstream as a 'slug' while it's rotating- let's say from the IC or ducting. This has been known to bend connecting rods on other engines where the liquid is fuel and not water.

If the ice is forming in the supercharger and it slowly dribbles into the combustion chamber as it melts, again a bent connecting rod is possible. Remember that the inlet valve would need to be open to allow the water in and that the piston is still descending. The piston still needs to go through BDC and rise on the compression stroke for the hydrolocking to occur. The rotating mass of the engine will be sufficient to bend the rod. A friend that restores '60s vintage fuel injection units displays one at his vendor's booth as an example.

So far the OP's have gotten off lightly with just a bent plug electrode.

If the engine is allowed to idle for an extended period- this will not melt the ice as the cold air passing through the engine will not allow it to. The heat normally induced by the boost is now gone, and as has been argued above, the cold surfaces of the supercharger and/or IC are the cause of the ice accumulation in the first place. If we accept the examples of the ice on the wing or the glass of ice water, even more ice will accumulate instead.

What's left?

If the car is taken back out on the road and given a good thrashing to 'clear it', there'll be plenty of heat inside the supercharger, but the forward speed of the car will cause this heat to be lost in the IC and possibly more moisture will condense.

I suppose the engine could be raced at idle for an extended period - a moderate amount of heat will be produced by the supercharger and there will be no air flow through the IC. Might work.

Possibly a page can be taken from the link I gave way up above where the IC was partially blocked off to reduce it's efficiency. Maybe Ford has a better idea.

 

Perhaps doing like the big rigs do...block most of the air passing through the radiator/intercooler? It would raise the temps under the hood and the intercooler. All it would take is a piece of cardboard behind the grill.

Another option might be to disconnect the cold air intake scoop so the air drawn into the intake comes from the warmer engine area?

Just thinking out loud...

 

But is it happening? We've no reliable evidence that it is, seems to me.

And if it is, why is it so incredibly rare? There are tens of thousands of SC jags running for 10+ years.

 

Yes, it's happening. Can we move on?

I was thinking about blocking airflow as well. Raising underhood temps. I didn't suggest because the idea of sticking a piece of cardboard behind a radiator on Jaguar just seemed unappealing. I think it would work though. The extremely low temps would certainly keep the car cool enough and possibly stop the condensation problem. It still seems wrong though.

 

I'm not suggesting blocking airflow to the radiator or attempting to raise coolant or underhood temps.