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Throttle Surging

Mike2500HD

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Mike2500HD Enthusiast

Mike2500HD

Posted
Posted

When I excelerate gently, I feel the engine surging as it builds revs. It feels like it wants to go faster for a second then it backs off and so on. If I give it more gas or floor it it just builds revs normally. Also it feels like at around 2500 rpm or so it suddenly has way more power. Its the 6.o in a 2007 2500HD, 6spd tranny. It either feels like the throttle position sensor is irratic. or the injection works better at larger throttle openings. Ive ridden motorcycles where the power band was peaky and it "came on" at a certain rpm. Doesnt seem likely in a tourqy truck engine though. Its not bothersome. Im very sensative to such things and its likely other people wouldnt even notice. I was just wondering if anyone else felt this.

robertbick Enthusiast

robertbick

Posted
Posted

I have felt this. It's only for a brief second or less but I feel/hear it surge a bit then go back down. I never checked the RPM's but it is at low RPMs. I only get it when it's a light touch on the gas pedal.

wilkes65 Enthusiast

wilkes65

Posted
Posted

My 07 has this feeling as well. Also the powerband on these 6.0's are very strange to me. At about 4000 RPM it feels like you hit a nitrous button or something.

wlvrn1215 Senior Enthusiast

wlvrn1215

Posted
Posted

I have a tune and run premium gas too....it still does it... At real light throttle\ TC lockup it does it...cant see it in the rpm gauge but sounds like its surging

builderpaul Enthusiast

builderpaul

Posted
Posted

I always thought it was do to the sensitivity of the fly by wire throttle. Seems at light pedal applications any little bump etc will cause your foot pressure to change. At light throttle the pedel seems very sensitive to any change of pedal pressure. This can cause small changes in acceleration that can be felt by some of us sensitive types.

landryd Enthusiast

landryd

Posted
Posted

Bob,

 

Owner's manual for my 2007 6.0 calls for premium fuel 91 octane or better. If lower octane is used then "slower acceleration" and "heavy knocking" will result.

Kodiak450 Senior Enthusiast

Kodiak450

Posted
Posted

Two questions. The 07 you are talking about, is it the classic 2500? 6 speed tranny?

 

Other question, does it really say to use premium? I know for years GM designed all their V8's with the exception of some muscle car engines to run on 87 grade. I'm kinda dumb founded to hear you say that they recommend 91 grade for the 6.0 engine. I can see the 8.1 maybe needing 91, but the 6.0 in the 2500's??

Genuinefine409 Enthusiast

Genuinefine409

Posted
Posted
Two questions. The 07 you are talking about, is it the classic 2500? 6 speed tranny?

 

Other question, does it really say to use premium? I know for years GM designed all their V8's with the exception of some muscle car engines to run on 87 grade. I'm kinda dumb founded to hear you say that they recommend 91 grade for the 6.0 engine. I can see the 8.1 maybe needing 91, but the 6.0 in the 2500's??

 

 

The 6.0 has too high of compression not to use 93 when tuned to how they should be. however, they are tuned from factory to be able to run fine on 87 octane. pre-computer cars would have 8:1 compression for 87 octane, 9.5:1 with 87 octane wouldn't work too good. i run premuim on my 6.0 and get better mpg, espcially when towing. and while having a snap-on mt2500 hooked up, i notice it doesn't pull the timing back at all on 93 octane versus 89 or even 87. for the extra $.30 per gallon, when gas is over $4 gallon, whats it matter.

 

Anyone who builds/tunes engines knows you don't need premuim fuel but you can benfit from it. you'll never notice having too much octane, but you'll always notice when its too low.

landryd Enthusiast

landryd

Posted
Posted

Right from the owners manual on my 2007 Classic 2500HD. All engines use regular unleaded except the 6.0 - 91 octane or better.

irengineer Enthusiast

irengineer

Posted
Posted

Don't think you'll find the 91 octane or better suggestion in the GMT900 (NBS) 2500 HD LY6/MYD (6.0L/6L90E 6Spd) owner's manual. In fact I'm sure of it, but I'll leave some wiggle room just in case someone wants to look it up and finds that I am wrong.

 

For the guys who've noticed the surge, keeping in mind we may or may not all be talking about the same "surge"..........Do you notice this surge after an extended idle? Do you notice this surge during cooler ambient temperature?

 

Hot intake air temperature causes spark to be retarded to prevent knock. After extended idles it takes a few seconds to get rid of the hot underhood temps, once cooler air is present spark is ramped back in and there is a noticeable change in performance.

Roofer Senior Enthusiast

Roofer

Posted
Posted

The engines are made to run on 87 octane.

 

There are 9.9:1 engines that run fine on 87. Running premium is just to run a little cooler to reduce pinging on older engines.

  • 3 months later...
Mike2500HD Enthusiast

Mike2500HD

Posted
  • Author
Posted
My 07 has this feeling as well. Also the powerband on these 6.0's are very strange to me. At about 4000 RPM it feels like you hit a nitrous button or something.

 

I dont know if anyone still reads these posts. I just come back every once in a while when I'm bored. But yes mine runs the same way. Almost like there is variable valve timing that opens up the H.P. at certain throttle openings. It runs like and sounds like a nascar engine at high rpm/throttle. That huge garbage can of a muffler sounds great suprisingly enough. Even at idle.

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