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'13 Dodge Challenger SXT
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Discussion Starter #1
Good evening all,
Maybe I'm just being a little paranoid as usual... In my 2013 SXT, I feel like climbing steep hills it slows down and struggles to speed up. I also own a Dodge Nitro with less HP that doesn't seem to struggle as much. I've had my fuel pumps replaced recently as well as my motor mounts, and a CAI put in. Any ideas or is this what a 4,000 lb 6 cylinder vehicle feels like going uphill? Thank you!!
 

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Depends upon the hill and altitude.

In some areas of the country there are "roller" which refer to hills. The road is not cut through hill but goes up and over and down the other side then repeat. These hills can be rather steep.

When I worked north of I-70 just north of Grain Valley MO there was a road that ran in front my my employer that had a series of rollers -- in the west direction. The elevation change was not much IIRC around 200 feet but the grade was damn steep. I don't remember any of my cars: Mustang GT V8 (approx. 215hp), Porsche Boxster (flat 6 and 217hp), VW Golf TDi (straight 4 with 90hp); having any real problems. But all cars were equipped with a manual and picking the right gear was important. Given the speed limit no way I could attempt to climb these in high gear. Besides the road crested then dropped back down the side pretty sharply. Even though I was familiar the road as the car crested the hill I invariably as I could see nothing but air in front of the car I lifted off the throttle. At speed one would have launched car like in the movie Bullit on those steep SF hills. About as steep as the hills I'm talking about.

I'm sure I got no higher than 3rd gear when I pulled out of the parking lot and headed west on that road.

Now with those same cars on mountain roads -- mainly freeways -- rather steep grades can be taken in high gear -- all were 5 speed transmissions -- and at the speed limit -- most of the time 75mph. And this even when the elevation was around 7500 feet above sea level. But in other areas -- Copper Mountain CO at around 9000 feet above sea level the Mustang and Boxster "struggled a bit". I had to down shift for nearly any up grade. The VW Golf was turbo charged and it handled even higher elevations with no real problems. And going over Eisenhower Pass (CO on I-70) the Mustang and the Boxster really struggled. They had very little pickup. The VW Golf took that pass like a billy goat on meth. No problem. I monitoring the level of boost the turbo was making. IIRC it was around 60psi. That's 4.1 bar. By way of comparison my 996 Porsche Turbo nominally made 0.7 bar (max) at sea level. In Wyoming at around 9K feet above sea level it made a max of 0.9 bar.

In the case of your car if it is a manual you need to be darn sure you downshift to keep the RPMs up and the engine in the fatter part of its power band. My Boxster with 220hp could climb pretty steep grades at speed in top gear but the car only weight 2800lbs (the same as the VW Golf and believe it or not the same as my MINI JCW).

I would hazard a guess a much heavier car: The SXT weighs in around 3961 lbs could struggle a bit if the incline was steep enough.

With 292hp the car has 13.56lbs per one HP. But my Boxster for example with 217hp and 2800lbs has "just" 12.92lbs per one HP.

Bottom line is there may not be anything wrong with the car it is just encountering some pretty steep hills. That is unless you tell me this is a recent phenomenon. If this is the case then there could be something "wrong" with the engine that accounts for this behavior.
 

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Normal temps on the dash, but it's about 110 out lately.
I use 89, recommended in the manual.
Have to mention I have driven various cars in temperatures up to 119F and if there was some impact on performance it was not to the point I could feel it. Really the biggest impact on engine performance I have found is from elevation.
 

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'13 Dodge Challenger SXT
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Discussion Starter #6
Depends upon the hill and altitude.

In some areas of the country there are "roller" which refer to hills. The road is not cut through hill but goes up and over and down the other side then repeat. These hills can be rather steep.

When I worked north of I-70 just north of Grain Valley MO there was a road that ran in front my my employer that had a series of rollers -- in the west direction. The elevation change was not much IIRC around 200 feet but the grade was damn steep. I don't remember any of my cars: Mustang GT V8 (approx. 215hp), Porsche Boxster (flat 6 and 217hp), VW Golf TDi (straight 4 with 90hp); having any real problems. But all cars were equipped with a manual and picking the right gear was important. Given the speed limit no way I could attempt to climb these in high gear. Besides the road crested then dropped back down the side pretty sharply. Even though I was familiar the road as the car crested the hill I invariably as I could see nothing but air in front of the car I lifted off the throttle. At speed one would have launched car like in the movie Bullit on those steep SF hills. About as steep as the hills I'm talking about.

I'm sure I got no higher than 3rd gear when I pulled out of the parking lot and headed west on that road.

Now with those same cars on mountain roads -- mainly freeways -- rather steep grades can be taken in high gear -- all were 5 speed transmissions -- and at the speed limit -- most of the time 75mph. And this even when the elevation was around 7500 feet above sea level. But in other areas -- Copper Mountain CO at around 9000 feet above sea level the Mustang and Boxster "struggled a bit". I had to down shift for nearly any up grade. The VW Golf was turbo charged and it handled even higher elevations with no real problems. And going over Eisenhower Pass (CO on I-70) the Mustang and the Boxster really struggled. They had very little pickup. The VW Golf took that pass like a billy goat on meth. No problem. I monitoring the level of boost the turbo was making. IIRC it was around 60psi. That's 4.1 bar. By way of comparison my 996 Porsche Turbo nominally made 0.7 bar (max) at sea level. In Wyoming at around 9K feet above sea level it made a max of 0.9 bar.

In the case of your car if it is a manual you need to be darn sure you downshift to keep the RPMs up and the engine in the fatter part of its power band. My Boxster with 220hp could climb pretty steep grades at speed in top gear but the car only weight 2800lbs (the same as the VW Golf and believe it or not the same as my MINI JCW).

I would hazard a guess a much heavier car: The SXT weighs in around 3961 lbs could struggle a bit if the incline was steep enough.

With 292hp the car has 13.56lbs per one HP. But my Boxster for example with 217hp and 2800lbs has "just" 12.92lbs per one HP.

Bottom line is there may not be anything wrong with the car it is just encountering some pretty steep hills. That is unless you tell me this is a recent phenomenon. If this is the case then there could be something "wrong" with the engine that accounts for this behavior.
Wow, that was a very informative answer... Thank you so much, seriously!
Maybe it is just my imagination. Mine is an automatic and I've never taken it up a steep highway ramp such as this one before, and it's always at slow speeds. Again, I appreciate your response.
Btw, quite the impressive collection of cars!!
 

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Wow, that was a very informative answer... Thank you so much, seriously!
Maybe it is just my imagination. Mine is an automatic and I've never taken it up a steep highway ramp such as this one before, and it's always at slow speeds. Again, I appreciate your response.
Btw, quite the impressive collection of cars!!
What you might be encountering is the automatic's "reluctance" to downshift. It might hold a higher gear which would seem to make the car feel sluggish and unresponsive to the throttle.

I have experienced this to a small degree with my Hellcat. My work commute has (well had) me heading west on i-580 out of Livermore CA to the SF Bay area. There is a hill (mountain range) that the freeway crosses. The road rises from around 300 feet above sea level to around 1000 feet above sea level and does so over the span of several miles.

If I leave the automatic in D mode the transmission is in 8th gear at around 65mph by the time I reach this section of road. The road before the incline is very flat. The speed limit is 65mph. In some cases traffic runs a bit under the limit and this causes me to lift off the gas pedal a bit. But the transmission may not down shift. In this case believe it or not the Hellcat can feel a bit sluggish as I ease back on the gas pedal to increase speed to keep up with traffic. I am loathe to press it very hard for various reasons.

The sluggish feeling has me manually downshift to 7th gear. The engine becomes much more responsive to the gas pedal without the abruptness that arises when one presses down the pedal hard enough to cause the transmission to downshift on its own.

In fact most of the time I would have the Hellcat automatic in M mode and in either direction of my work commute take this hill in 7th gear. I pretty much reserve 8th gear for steady highway speed cruising on relatively flat terrain.
 

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What I think is happening is that since the engine is under heavier load up hill and you are running the recommended octane (although I think minimum is 87), the engine is experiencing knock on account of the extreme ambient temps. Timing is pulled by the PCM to reduce/remove knock which also causes a reduction in torque. On hot days higher octane can help in minimizing knock even further. On my 2013 the recommended octane is 89 but when I am towing I run 93 otherwise I get a fair amount of knock with the extra load.
 

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What I think is happening is that since the engine is under heavier load up hill and you are running the recommended octane (although I think minimum is 87), the engine is experiencing knock on account of the extreme ambient temps. Timing is pulled by the PCM to reduce/remove knock which also causes a reduction in torque. On hot days higher octane can help in minimizing knock even further. On my 2013 the recommended octane is 89 but when I am towing I run 93 otherwise I get a fair amount of knock with the extra load.
Interesting. Easy enough for the OP to "test". Just fill up with a higher grade of octane and hit the road and see if the engine reacts any better.
 

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Interesting. Easy enough for the OP to "test". Just fill up with a higher grade of octane and hit the road and see if the engine reacts any better.
Well, technically should be tested with similar ambients and the battery should be pulled so any learned LT adaptives will be reset.
 

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Well, technically should be tested with similar ambients and the battery should be pulled so any learned LT adaptives will be reset.
Didn't mention the ambient temperatures should be similar. Figured that was a given. As for resetting LTFTs they'll adapt quick enough unless the driver faces the test section of road just out of the driveway.

Added:

Probably should add that it is better to be safe than sorry so your mention of the temperatures was you being your typical thorough self. And appreciated.

I'm loathe to mess with the battery for anything unless absolutely necessary. If the LTFTs want to be reset to their defaults my preferred method is using a code reader to clear error codes.

Even if there are no active codes this resets the LTFTs to their defaults.
 

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Not aware of any long term knock adaptation. Can't recall coming across in the OBD2 references I have of any PID to obtain long term knock adaptive values. (But I might have missed it.)

At any rate that seems contradictory. Knock is a power stroke to power stroke variable. Why would the PCM need to have a long term memory of this?
 

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LT knock is learned by the PCM (and is a PID that can be monitored via OBD2 using alfaobd, diablo, hptuners and probably other scan tools)....why because if it consistently sees knock it can adjust timing to avoid it.



BTW the GPEC2A engine controllers also have a means to control knock by adding fuel rather than pulling timing but on the N/A hemis it appears to be zero'ed out.

If you still don't belive there is such a thing as LT Knock, here is the table limiting the maximum amount of retard it can apply to the engine on a HC.
998131
 

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Ok. I'll take your word for it. But first I heard of long term knock adaptation. In this case then a procedure to reset these to their defaults is probably a good idea.

Because an error code clear -- even if one is not active -- resets long term fuel adaptation back to their factory defaults I would like to believe it would have the same effect on long term knock. course, reading of this before and after a code clear would likely confirm this was the case unless the long term knock was for some reason already at the factory default.
 
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