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Old 02-07-2013, 09:13 AM
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New to diesels. Throttle question

Bought my 1st diesel completely stock exactly 1 month ago. Not exactly sure whats normal and what isn't. About the throttle, it doesnt seem that the progression between how much I push down on it and how much it accelerates is consistent. Is that because of the drive by wire or tranny? Before this I drove a 5 spd fully built 01 Mustang GT, so I'm used to getting out of it however much I step on the pedal.

Is this just something I need to get used to?
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Old 02-07-2013, 10:05 AM
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If your at a dead stop and you floor it, you wont go anywhere. Its called turbo lag where your truck needs to suck in air first. Not sure if this is what you mean
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Old 02-07-2013, 10:14 AM
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Re: New to diesels. Throttle question

Probably also dealing with the torque converter slip that's normal.

I made my Samsung SGH-I997 send this.
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Old 02-07-2013, 10:31 AM
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what you're describing sounds to me like 'flash stall', which is a torque converter function..

flash stall is a measurement all by itself that a lot of folks don't count on.. the basis (if I can explain it decently) is this:


an automatic transmission is driven by hydraulics.. fluid moving, swirling the direction the engines crank is turning it.. the torque converter is a fluid coupler, which is physically attached to the main crank of the engine and forces the fluid 'attached' to the transmissions main shaft to swirl the same direction..

if you're idling @1000 RPM, and absolutely stand on the throttle, NOTHING will happen until you reach 1500 RPM... this would represent a 'flash stall' of 500 RPM.. it sounds just like slip, and feels like it for the best part, the only distinguishing factor is when you're slipping, the truck will actually attempt to move.. below and during flash stall, it won't..

think of it like this:

you have a bucket of water in front of you, and a paddle in your hand, resting in the bucket.. you're about to start vigorously stirring that water, like you're mashing the sour for a good stihl run..

instead of starting out slow like, you start stirring like a mad man- and it is a second or two before that water starts uniformly flowing in a circular pattern....

the time between when you start vigorously stirring and when the mash starts uniformly swirling is that bucket of Sour Mash's 'flash stall' rate...

the flash stall has a lot to do with the volume of the transmissions pump, the volume of the torque converter, and the quality of the t/c's stator function.. if you notice your flash stall starting to lengthen a considerable amount, you may need to start paying close attention to the t/c and transmissions health.. it is a good indicator things are wearing out- specifically the stator (which is the gadget that allows that swirl to reverse direction on the same plane)..

transmissions are floggin' intricate and intimidating to figure... but their function is pure simplicity.. it's all about the transfer of fluid, which can dang near be explained every time with that bucket and how the water responds...



edited to add: a high flash stall isn't a bad thing... think of it as getting a running go at something.. if you've built up a lot of inertia, your first obstacle is less likely to stop (stall) you dead in your tracks.. too much, though, and you burn a lot of fuel and put some needless high temperatures in your transmission/ and t/c..

Last edited by drewactual; 02-07-2013 at 10:42 AM.
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Old 02-07-2013, 11:05 AM
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Re: New to diesels. Throttle question

Yea, I understand turbo lag. I was talking more along the lines of while on the move.

Flash stall sounds more like what I'm talking about. Makes a ton of sense. Sooo a some stall is fine, correct?
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Old 02-07-2013, 11:08 AM
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yup.. some flash stall is a good thing.. it's all about getting that inertia going so hitting that first obstacle doesn't stall it cold..

understand, flash stall is something that is accounted for while engineering these rigs.. just like the primary stall rate is..

Last edited by drewactual; 02-07-2013 at 11:16 AM.
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Old 02-07-2013, 11:18 AM
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Re: New to diesels. Throttle question

Badass. Thanks, man.

Sent from my SCH-I535 using AutoGuide.Com Free App
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Old 02-07-2013, 03:56 PM
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Re: New to diesels. Throttle question

So after driving and thinking about what you said, I noticed that there is about a 5-600 rpm "hang" so to speak. So at what point does that slack go away and begin to actually pull with the engine? Is it a period of time? Additional throttle given? I know if I give it enough to downshift, it'll pull. Is that the only way?

Hope that makes sense.
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Old 02-07-2013, 04:39 PM
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The lag between boost and throttle response when the truck is at a stock setting is a joke. Tuned up there is still lag but considerably less. I noticed that taking off from idle the truck has a slight delay but taking off over 1000rpm i cant keep the truck straight the first 60 mph in 2wd.
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Old 02-07-2013, 05:05 PM
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Flash stall will exist anytime you rapidly apply throttle.. it should be about the same jump every time.. easing into throttle you won't see as much if any.. popping it decently hard, its going to flash..
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