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Revving the engine and RPM's

Hemogoblin

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Not sure if anyone has posted this but how ANNOYING are the Hemi's when you try and rev the engine? I recently installed a new muffler and while it sounds great (MBRP), when friends ask me to rev the engine, the damn thing rev's and hangs high and slowly comes down. Like it doesn't just run up and down quickly, like my old Trans Am used to. I get it, this thing is drive by wire but WTF is going on? Super embarassing.
 

tidefan1967

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Every Hemi I’ve had revved like that so it’s completely normal. I honestly never gave it much thought.
 

Raydar

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It's an emissions thing. Revving it up and then dropping the throttle quickly causes all sorts of nastiness (thinking NOx, maybe?)
If it slows down gradually, that puff of whatever-the-hell-it-is is eliminated.
 

Hemogoblin

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Thanks guys, I was actually thinking it was something off with the computer but looks like it's a Hemi thing. My old LT1 was a very different beast. And yes, my neighbours (well, one in particular) hated me when I had that thing. Apart from the mods internally, it was running 1 3/4" headers/Y-pipe, punched out cat, and straight through, bypassing the Borla muffler. That thing was SO LOUD and sounded incredible. SO much fun. Wish I had kept it......

Anyway.....
 

Ramjack

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@Raydar is right; it's an emissions thing. It's not a hemi thing. This has been normal ever since mass air-flow sensors have been introduced. I remember when I got my first 5.0 Mustang in 1989. I was pissed because it would rev like you describe whereas my friend's 1987 Mustang GT would rev up and down quickly. Turns out 1989 was the first model year they switched the 5.0 from speed density to mass air flow. Not sure how I figured that out so long ago without the internet.
 

Raydar

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@Raydar is right; it's an emissions thing. It's not a hemi thing. This has been normal ever since mass air-flow sensors have been introduced.

It really started way before that. I had a friend who had a mid-70s Toyota Corolla, with a 4 speed. If you tried to down-gear to slow down, the d@mned thing would try (poorly) to rev match whatever speed and gear you were doing. When you finally got to a stop, it would idle the engine down. Annoying AF. And they did it all with solenoids and vacuum hoses. I hated driving that car.
 

d19r93

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Mine does that if I rev it right after starting up. If it's been running awhile, it revs just fine. Limits at 4k but doesn't hang like it does when you first start. And to be clear, I don't rev it when it's cold. It will do that right after a startup no matter what the temp is. It has to be running for a few to be able to rev it like you're wanting.
 

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