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-   -   The KTM Duke 390 Ownership Experience Thread (https://www.team-bhp.com/forum/motorbikes/138082-ktm-duke-390-ownership-experience-thread-201.html)

Dr, hardly you get a situation to test this. For the heat bar is already approaching the max and the fan is going to be on till it reaches the minimum and thats going to take a lot of time.

But i did notice this behavior in short runs where the fan auto cuts off after few minutes. Buts once you drive over 4-5 kms the engine is already super hot and standing still only increases heat for the first 10 minutes before the cooling cycle starts.

The fastest way to cool was riding it and the moment you stopped with lack of natural air the fan can only do like 25% efficient cooling compared to when the bike is on the move.

The additional 75% is the time taken for the bike to enter cooling phase and by that time you are already back on move.

While riding if the heat bar is at mid point, the moment you stop it goes up to top notch point before starting to cool down.

Simply put, the fan and radiator are incapable of cooling the bike down at standstill. They just about keep the temperature constant steady state. The 390 needs moving air for the cooling to work. I believe it needs a bigger radiator than the one it already has been given over the 200 .....

I thought you where concerned about switching the engine off, under electrical load.

If we look at it in a different angle, isn't the high temperature good for the effeciency of the engine. My thermodynamics is rusty, but I think it has something to do with Carnot's theorem.

And also colder engine will affect the fuel mixture, though O2 sensor and temp sensor, theoretically compensates.

So when we continue from a stand still, for instance, from a red light, then if the engine temp is maintained, then the out put of the engine will remain the same which is needed for a race engine.

I agree that if the temp shoots up, it is bad for other systems like cooling, lubricating etc

My point is may be KTM, has decided to maintain the heat of the engine for the 390 at max possible, in stand still, so that it will zip away at the slightest hint of throtle release, as it is a racing machine.

Sorry for not being clear. By efficiency, I meant thermodynamic effeciency, not the mileage part.

MODS, please excuse me for multiple posts on the same topic.

Any theory can be tested by extrapolating to extreme conditions.

If cooling the engine is so important, other than the sole purpose of over heating, then why not put large capacity exhaust fans in vehicles???

I stick to my point. As we can all observe, engine temp is maintained at around 80% of the temp range allowed by the cooling systems in any engines. Why don't the designers put a large size exhaust to bring down the temperature, below 50%.

One arguement might be the electrical load exerted by large exhaust. But then, there are superchargers which put high load on the engine, which is compensated with the additional power produced by charging.

As manofsteel posted earlier, someone has managed to put a higher capacity fan in place of the stock fan. I think it is not warranted in case of a high comp ratio petrol engine.

Please do explain why putting a bigger fan will not aid in better cooling.

And by 'bigger exhaust', did you mean bigger radiator fan?

In WOT, on any bikes, it is normal that the weight transfer occurs to the rear wheel and the rear suspension sqats. The front end will be having little or no grip depending on the amount of acceleration as it will be 'almost' off the ground. I guess you might have been holding on to the handlebar tightly. Loosen your grip so that you wont put any unwanted steering inputs while accelerating.

PS: move back and anchor your bottom to the rear seat's hump. This will extremely useful and you wont need to hold on to the handlebar tightly.

I completely agree what mithunvvijayan is saying on the engine heat.

Let me put in simple words on what the confusion is by asking this question -
What is the task/joq of an engine radiator ?

1. A. Is it to keep the engine cool by trying to bring down the temperature ?
2. B. Or is it to keep the engine without getting over-heated by trying to maintain the temperature within a specified threshold temperauture ?

If I am correct in understanding what ebonho has said, his concern is based on point#A. mithunvijayan's point is in the context of point#B. Please let me know if I have misunderstood your thoughts.

In real world scenario Both point A and B means the same thing. Let me put forward my understanding.

The basic task of a cooling system is to transfer the heat from the engine block to the atmosphere. In case of liquid cooled engines, engine heat is first transferred to a fluid(coolant) and then dispersed into ambient air through a radiator.

And no cooling system is capable enough to transfer the complete heat produced by the engine to the ambient temperature while the engine is operational. Thats why you will always see even an idling engine hovering at 60-80deg C even while the ambient temperature will be 25-35deg C. And due to that practical limitation all engines works best (or atleast designed to work) at an optimum operating temperature and the cooling system (radiator is an inccorect term) will be able to bring down the temperature to only that optimum operating temperature with sufficient flow of air around the radiator.

I agree to one point that the 390 could have used a heavier cooling system (bigger capacity radiator and fans). But there is always electrical load, engine load, weight and even climate of even other countries to be considered.

Lots of engineers here. I'm just a doctor. Who rides. :)

Call me paranoid, but if a bike heats up to just shy of its max threshold limit, and then stays there under load (running hard), but then refuses to budge even a bar even after more than 10-15 minutes of idling (no load), with the radiator fan on full blast, and then as has been claimed by one of the members here, still shows essentially the same high temperature 3 hours later to the motor being shut off, I would at the very least SUSPECT that something is not right.

Of course I could choose to be an optimist and believe that the company designed it this way. For fast thermodynamically efficient getaways ... after periods of inactivity or rest.

However, for a variety of reasons, I do not have that luxury.

Fact of the matter - on the Duke 200, as with all radiator cooled vehicles, after a hard ride/drive the fan comes on, stays on for some time (either with the engine on or not), and then shuts off. Max a couple of minutes.

Not so on the 390? Why? Whats different? Whats special?

If you are referring to my earlier post, it was not showing the same temp bar after 3 hours. What I meant was that even after 3 hours of switch off period, it was still showing one bar(the very first bar) of the gauge.

I think you have answered it yourself in one of your previous posts. Although the radiator is bigger than the 200's, its simply not big enough to keep the temp gauge at mid point of the temp gauge. But it has been designed to keep the temp at the last but one bar constantly even in heavy traffic with the motor running. The moment we switch off the engine, the temp gauge will shoot up another 1 or 2 bars.

Oh ok. My bad. That's not abnormal. Especially on a hot or even warm day with not much breeze/moving air. Worse in basement parkings.

I understand your point. I was trying to understand the concern put forward by ebonho and so I raised those questions. To clear my own confusion, I once again went through his posts. His point is - if D390 has a bigger radiator+fan, then there is no chance for the fan to run for an extended period. KTM might have had two design options - Either have a bigger radiator/fan or have a smaller one but with the fan running for extended periods or run much faster. The decided to go with the latter one to keep the weight and the price down. One of the posts was pointing about the D390 fan speed being higher than that of D200. Of course I am not a thermodynamic engineering expert to say which among the two is the best.

How about the case with other performance bikes ?

If that's the case, the 390's are running on a very fine knife edge. Where the engine dpends wholly on the el cheapo fan to prevent catastrophic failure. Because the radiator system on its own just does not have any extra flex. Forget extra flex - it needs a fan to over-compensate under normal operating conditions.

Yes it could be a weight thing, or a money thing. Don't know about you guys, butI would just be more comfortable with a bike that quickly cooled down, versus on that's always on the edge of boiling over.

If you are talking about the Indian bikes, almost all others (even 200) has good cooling characterisics. And I think CBR250R has one of the best in business.

GUYS PLEASE HELP

At what rate does your bike tire lose pressure ?

mine on day of delivery read 28 F , 30 R
after 40/50km it went down to 25F , 23 R

Re-inflated them back to 25F , 35 R .

After 40/50km again it is - 18F , 28R

Re-inflated to 25/30 right now , Solo only ride so theoretically that is correct right ? Should I over inflate by 5 PSI right now to compensate for the loss of pressure (assuming it is some weird characteristic of new tire , yes I am clutching at straws stupid: ).

That is alarmingly fast imo , tire guy says no puncture visible either from a cursory visual check . Tire guy says in event of a puncture , it will deflate completely within 10/15km of riding , it will also lose significant pressure just standing still overnight , is he correct ?

Also after shutting off the bike , it makes clanking sounds like small pebbles hitting/echoing off steel , I assume that is normal right ? :) It seems to come from the exhaust system .

Did you reinflate the tire after riding it for quite a bit?

Dont worry, thats the cat-con cooling down.

As a layman, I feel your concern is very much valid and that is the reason why I put some effort to understand in my earlier posts. It may well turn out to be a design by intent with some valid technical reason, but right now, we don't have an answer for that.

Since this is a genuine concern, is there a way or channel through which we can get this clarified from KTM ?