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Old 11-30-2011, 06:04 AM
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Hemi - Sometimes fast, sometimes slow?

I know this sounds insane. Today I jumped in the jeep (hemi) and it flew off the mark. It was responsiveness, peppy and accelerated willingly throughout the rev range.

Other days it feels downright sluggish and slow. You put your foot down and wait a second or two before you get a response or there is quote a flat spot between 2000 and 3000 rpm. Mine is a may 2011 hemi v8. It seems worse in the heat or I traffic when engine is warmer. And I am only talking moderate temps.

I've tred to assess my mood and make sure I wasn't having my period, but all seems normal from day to day.

Am I insane or do you guys notice some variability in performance.?
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Old 11-30-2011, 06:46 AM
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Re: Hemi - Sometimes fast, sometimes slow?

No power after warming up! 5.7 HEMI
mb the same trouble?
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Old 11-30-2011, 11:17 AM
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Quote:
Originally Posted by wardy View Post
I've tred to assess my mood and make sure I wasn't having my period, but all seems normal from day to day.
LOL!

What about temperature differences? On cool crisp my cars always feel better than on warm days due to intake air temp.



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Old 12-01-2011, 03:23 AM
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Re: Hemi - Sometimes fast, sometimes slow?

Yes, I agree with the cool vs hot days. Cooler days always feel better, especially with my turbo cars, they hammer on cold days with all that dense air... But this is on any day, it will feel responsive for the first 10-15 min, but after say 45-60 when oil and engine temps are over 100 C it's starts to get sluggish.
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Old 12-02-2011, 11:23 AM
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Re: Hemi - Sometimes fast, sometimes slow?

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Originally Posted by wardy View Post
Yes, I agree with the cool vs hot days. Cooler days always feel better, especially with my turbo cars, they hammer on cold days with all that dense air... But this is on any day, it will feel responsive for the first 10-15 min, but after say 45-60 when oil and engine temps are over 100 C it's starts to get sluggish.
Our Jeep feels the same way, I was just telling my wife this the other day. Some days it has the power a Hemi should then some days it barely gets out of its own way.
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Old 12-04-2011, 02:29 PM
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Re: Hemi - Sometimes fast, sometimes slow?

Heat soak.....timing retard due to IATs plus knock retard because you're either running 87 or 89....
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Old 12-05-2011, 01:30 PM
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Re: Hemi - Sometimes fast, sometimes slow?

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Originally Posted by FlyinRyan View Post
Heat soak.....timing retard due to IATs plus knock retard because you're either running 87 or 89....
I think what people are feeling is the car in Open Loop.. I'm pretty sure these engine stick in Openloop while warming up which makes the engine run like a horse... Once it warms up, and starts going Closed Loop'd, the engine tames itself a lot -- goes into a much more conservative tune.. Then Heatsoak and what not kicks in as well.

Wonder if Terminator see this too.. Might be able to get him to grab some logs.
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Old 12-05-2011, 02:32 PM
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Re: Hemi - Sometimes fast, sometimes slow?

Doubt it. The stock tune is too mild to gsin from OL operation...
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Old 12-08-2011, 01:24 PM
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Re: Hemi - Sometimes fast, sometimes slow?

Mine does the same thing, but every car I've had has been peppier and more aggressive prior to the operating temp being reached. What made a difference on my JK was a stg II jet chip, nothing substantial but it made things more responsive. Same on my old 1.8t, then again it upped the boost a bit.
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