Not sure what you mean by this. The temp sensor is definitely screwed directly into the cylinder head, not the cylinder. It takes the reading in the general vicinity of the intake valve.




I would guess that the engine temp is calculated off the head sensor and the intake sensor, but I don't know that. Just a guess based on what makes sense to me.
Edit: nope, that's wrong. Engine temp is the sensor and Head temp is calculated.

 

I've had my head temp hit 360, that was over 20k miles ago. I've stop watching them since.

 

The sensor on the intake port is considered the engine temperature By HD.. From the pro street tuner.








Temp readings are shown in the upper left.. Cool night, short run, head temp reaches almost 300 deg.

 

Those of you that have PV, what Head temps, not engine temps, do you normally see?

If the Dakota displays the head temp only, then 320 seems to be normal.

 

Harley has done a fantastic job of keeping the engines running, and not burning oil, even when the cylinders go out of round. So most folks don't even realize damage has occurred, in great part due to the drop in power occurring over a period of time.

So, you are not going to see them breaking down very often from overheating. What does happen is a drop in performance and efficiency.




260 is not extreme, but it is getting very close to where accelerated engine wear occurs (270 & higher), and 260 is Past where the ECM begins retarding the timing in an attempt to cool the engine down.

And you are correct, on a warm day, most every '07-up TC (that has not had some help) is going to hit, and go past, 260...so it is "normal", but it is far from ideal.




Although 95% of HD dealerships will tell you 300* is normal, and they are correct, it is normal, 300* is definitely a number you don't want to be hitting.

At 250* (ET) is when the HD ECM begins retarding timing. 250* is too hot for the engine. That is why the bike is programmed to retard the timing...it is a self-protection mechanism.

At 250* and higher the power gets sluggish, MPG go down. Around the 270* is when accelerated wear (faster than normal wear, or what I would call damage) is occurring.

Sustained riding, 5-15K miles at, or around 300*, will put the cylinders out of round and the valves unable to seal properly.

I know, for many, this is a hard pill to swallow, and frequently when I share this information I get a variety of comments that all boil down to, this information is inaccurate.

It is really simple to test if one thinks I am off base.

Put any air cooled Twin Cam or M8 on a Dyno. Get it warmed up to 220-230*, do some dyno pulls.

Then let the temp creep up above 250* and do the same dyno pulls.

The difference will be apparent.


Heat is a bit of a complicated subject, not made any easier to discuss because of the unique nomenclature used.

Power is generated by heat, so obviously you need heat to get power out of the engine. Not enough and it won't run right, but too much and metal starts expanding at different rates, tolerances get loose, and more.

A bit on the nomenclature-

Head Temperature as displayed on the PV is NOT CHT. Head Temperature is an algorithm derived number.

This algorithm is based partially on the ET sensor, partially on the IAT (Intake Air Temperature) sensor, partially on the MAP (manifold air pressure) and some other factors which HD-Delphi uses.

ET as displayed on the PV is a direct readout of the sensor located on the back left of the front cylinder head. This is a hard number.

What is confusing is that it is reading the cylinder head temperature, but it is called ET (engine temperature). The reading that is call a head temperature is NOT the head temperature, but an algorithm based number.

Why are these numbers important?

Besides letting you know how your engine is doing temperature wise, they are BOTH used Differently to adjust your tune...both the fuel and the spark.

The ET is used for most of the lookup tables including the fuel tables and multipliers.

The Head Temperature is used primarily for spark temp correction.

Final couple of comments-

Once the engine is warmed up, the HT will almost always be substantially higher than the ET.

While I said above that the ECM retards the timing when the ET gets to 250*, the fact is that the ECM retards timing based on the HT...BUT, it is easier to monitor the ET (it is much more stable than the HT), and 99% of the time that the ET is at 250*, it has pushed the HT to the point where the ECM has retarded the timing and the bike begins feeling sluggish.


lol, that was a book...probably more info than most want, but hopefully some will find it useful.

 

Max, I think I see what you are saying. Take a look at this log I ran. It looks like as the vehicle speed increases the HT increased even though the ET stays flat.

Another thing I'm curious about. Your spread between the two temps are 23 degrees. I know you have a M8 and are reading the rear cylinder. I have a twin cam and am reading the front. My spread between the two is 80 - 100 degrees. Any idea why the difference?

 

320F for an oil temp is too high. You are literally "cooking" the additive package out of the base stock oil.

 

Max, take a look at this log. This one is after I put LJ cooling fans on the bike. It is at idle at a stop light. I cut a bunch of time out of it, showing only the drops in HT. The ET stayed at a consistant 253 but the HT reading dropped from 340 to 329. I can only guess that the HT reading on the PV is the actual reading at the head sensor. I'm guessing it decreased because of the air blown across it by the LJ fans. What do you think?

 

While I'd admit that I'm a newb as far as Dephi systems go, I would say there are a number of reasons. You mention 1, location.. Location itself can become very complex in estimation of chamber temps which is what they are shooting for. Remember the Dephi EFI systems is all about getting the right amount of fuel and timing to burn everything in the combustion chambers except the motor itself.. Between the M8 and TC, a whole bunch has changed.. Dual plugs, chamber shape, valves etc..

 

What do you think about the second log I posted? I figured the HT reading on the PV was the actual temp at the head and the ET was some sort of calculation. I know the new tuner software indicates the reverse, but it doesn't look like that from that log I ran. It looks like my HT decreased when I was stopped due to the LJ fans. I wonder why my ET didn't also decrease. If I have time tomorrow, I am going to run a log without the fans on to see what happens at idle at a stoplight. I will post.