[Rockster]

So I’m seeing around 500hp on my Hellcat Durango and curious if this is low? The Tq is also higher than HP which I figured would be the other way around. Just trying to figure out if something is going on. Really doesn’t feel that powerful once you get moving. Not trying to complain, but want my ducks in a row before I go back to my dealer again. Attached is a 0-90 pull, 8XX alt, 50* temp. Looking at Trackhawk graphs they’re showing Hp above 600
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The 707 number came from the engine being run on a dyno under I dare say "ideal" conditions.

Remember HP is derived from torque and RPM. If the RPMs are not high enough you'll never see the factory "HP". And in the case of the torque being displayed it too is a derived value possibly derived in part at least from the OBD2 "engine load" parameter.

Even if you managed to see 707 on the HP gauge given the engine is in the car accelerating considerable mass (approx. 4600lbs) and pushing "tons' of air and then there is the drive train loss the 707 number has to be derived and tweaked a bit -- some "correction" added -- to arrive at the 707hp number.

After break in I tried a few hard pulls with my Hellcat and never saw "707" hp. This does not mean the engine was performing sub par only that I just didn't have -- possibly -- the right conditions. Not sure even with the right or best conditions I could have managed to see 707.

With another car, fitted with (from the factory) turbos, nominal boost was 0.7 bar. Gave the car a few hard pulls and only managed to see 0.6 bar. Talked to the senior techs. They told me the engine controller seeks to produce the amount of torque demanded by the driver as signaled through the electronic throttle. If all it takes is 0.6 bar of boost that's all you will see.

Armed with this I picked a "better" location to try for 0.7 bar boost. An uphill grade with several miles of no freeway on/off ramps and no place for a CHP to hide. Also, I had a V1 in the car.

In 4th gear I floored -- and I mean floored -- the gas pedal. Speed built up very quickly but as RPMs rose I saw a solid 0.7 bar. But as RPMs got higher boost fell off a bit. Maybe because the factory called for 93 octane gasoline with 91 being ok but 93 was not available where I lived.

With the Hellcat there just wasn't enough room/road to subject it to the same "test". The turbo charged engine produced 420hp and the car began to eat up road at an alarming rate. The Hellcat and its 707hp would have gobbled up that section of road -- and it did -- with ease.

It is very rare for an engine to have a problem that limits its total output below that of what it should produce and not manifest other signs of this problem.

That I never saw 707hp from my Hellcat didn't bother me. I could tell -- butt dyno -- it had all the power it was supposed to have.

 

[Rockster]

Great info, thank you. It makes sense what you posted. I just figured/hope I was down on power due to lack of "wow" factor. This is my first Hellcat motor, I'm coming from 3 SRT Jeeps (6.4l). I was always figured it was snap your neck power.

Part of my issue is my butt dyno is very underwhelmed. Maybe a turbo vehicle would have impressed me more. At the current moment I haven't been happy with the power since I took delivery. I'm just trying to cover all bases and gather as much information as I can. I was expecting a lot more "thrown into the seat" feeling and I'm just not getting it! Dead stop launch it isn't terrible, but I'm seeing only a few tenths better than my 6.4 was (disappointing). Once I get anywhere above 30mph and hit it, it's just not impressive to me one bit. Oh well....

I didn't push my Hellcat early on. I adhered to the break in and also wanted to give myself time to adjust to the vehicle. Moving from a 420hp vehicle to a 707hp vehicle (the 2 months I spent with my 2018 Scat Pack prior to buying the Hellcat didn't really count since it was in break in for much of that time) is quite a step up.

Don't recall when I started pushing the Hellcat more. It was past the nominal break in probably in the 4K to 5K mile range. With this number of miles under my belt I was more comfortable with the car -- which I used mainly for my 30 mile work commute and this didn't afford me with any opportunity to explore the car's limits.

When I did once in a while push the car it was not from a dead stop. It was clear to me without judicious throttle I'd fry the rear tires in no time.

But from a roll...I recall one time as I was going up an on ramp to the freeway, a ramp I had driven up uncounted times before in other cars, and after having gotten the Hellcat moving at a reasonable speed "nailed" the pedal to the floor. I got pushed back in the seat big time and at some speed the car got light. There was a slight hump/rise in the road that I never noticed before with other cars but with the Hellcat it could reach speeds only dreamed about by other cars.

There were other times, too. Quite the experience to hammer down a car even at some speed and with the A8 downshifting have the rear tires break loose.

I will point out the Hellcat has good (understatement of the year) power but to really get the most from it just pushing down on the gas pedal is not the way. Under normal circumstances yeah this is quite sufficient. But to really experience the acceleration the car is capable of I found using the -paddle to downshift the transmission to the "ideal" gear concurrent with flooring the gas pedal delivered acceleration that was damn near plaid...

 

[Rockster]

So from what I'm gathering there is no break in mode. The second your vehicle comes off the dealer line, you have access to full power. You however don't have access to the launch control until 500miles.

Not to put too fine a point on it while you have access to full power -- theoretically that is there is no limiter -- the engine is new (obviously) and a new engine has considerable friction. This is one reason why break in generally requires one keep RPMs low and avoid sustained operation at higher RPMs. What this friction does is sap power.

With a number of cars over the years my experience has been the engine really needs some miles beyond the nominal break in miles to really get "loose" enough to operate up to its full potential. This is not a new discovery but something that car makers have known for years. Lab and field studies have found break in continues past nominal break miles for in some cases thousands of miles. Sure the added break in miles no longer provides any benefit one can feel in the seat of his pants but it still happens.

My advice to you is just adhere to the factory break in guidelines. If not forbidden in the owners manual change the oil early a few times -- with my Hellcat I had the oil changed at around 500 miles, 2K miles then again at 5K miles. The engine will break in and the friction losses will go way down and then you can begin to experience more of the engine's potential.

 

[Rockster]

Is this the circular one?

if so, mine has only displayed 500 as the max under full acceleration to 90. Could be a scaling issue I guess. Going to dealer on Monday to make sure

You will not see max HP -- whatever that number is -- unless you take the engine to near red line. HP is derived from torque and RPMs.

HP = torque * RPMs / 5252

Torque peaks at something less than red line but it is the RPMs over this torque peak RPM threshold that adds to the HP.