How do the accelerator pedal and rpm interact in an internal combustion engine?

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    Accelerator Pedal Rpm
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Discussion Overview

The discussion revolves around the interaction between the accelerator pedal and the RPM of an internal combustion engine. Participants explore how various factors, such as compression ratio, air-to-fuel ratio, ignition rate, and airflow through the intake manifold, influence engine speed as the accelerator is pressed. The conversation delves into both theoretical and practical aspects of engine operation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that the compression ratio remains relatively constant, while others argue that it can vary slightly under certain conditions.
  • There is a contention regarding the air-to-fuel ratio, with some asserting it should be constant, while others suggest it varies significantly, particularly at different RPMs.
  • Participants discuss the ignition rate, with some indicating it must advance as RPM increases, while others suggest it is dependent on the RPM itself.
  • The airflow through the intake manifold is generally agreed to increase with RPM, influenced by the position of the accelerator pedal.
  • Some participants express uncertainty about the definitions and roles of these quantities, leading to varied interpretations of their constancy or variability.

Areas of Agreement / Disagreement

Participants do not reach a consensus on which quantities are constant or variable. Multiple competing views exist regarding the behavior of the air-to-fuel ratio and ignition rate, leading to an unresolved discussion.

Contextual Notes

Some participants note that variations in the air-to-fuel mixture can occur due to engine conditions, and the discussion acknowledges that assumptions about constancy may depend on specific operational contexts.

  • #91
Ranger Mike said:
without having a diagram of the internal passages of your carb i can take a guess. You have two circuits connected to the main jet. The needle screw adjusts the idle like i said. This fuel is still sucked up the carb even at high rpm and is always open so it contributes to the total amount of fuel the carb is using. At high rpm you can shut off the idle circuit but risk making the fuel /air mix too lean and burning an intake valve. Going wide open throttle invites this.

Ok now I understand this.
 
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  • #92
Sailor said:
Worng, my question asks about the acceleration pedal, and it does not lead to 0 rpm nor to any value that would kill the engine and again we have confirmed in post #62 by jack and #66 what the variations are about and for what reasons

That's what, accelerator pedal is connected to throttle butterfly and AFR control, or, throttle butterfly only. Connecting the accelerator pedal to AFR is manufacturer's choice. See Baluncore's posts:
Baluncore said:
That can not be concluded. You are assuming the engine has a simple carburettor.
Carburettors restrict variation of AFR, while direct fuel injection makes any AFR possible.
Many vehicles couple the accelerator pedal directly to the injection pump.
The air flow is kept proportional to RPM. The accelerator pedal causes a change of the AFR alone.
The title of this thread is “Accelerator pedal and rpm”.
Sailor said:
Throttle range is much wider than the 10% you have stated, there is no relation between them
I never said throttle range is 10%. What I said was since AFR screw can change rpm by only 10%, throttle is provided.

Sailor said:
Your point isn't clear

What should the maximum torque indicate in here

Again, unless there are solid numbers, this would implies nothing

I just thought that max torque occurs at max rpm. If that's true, my engine's redline is 6750 rpm.
Sorry, I could not fetch more numbers.
 
  • #93
Without question or context, this thread will go in circles at a high RPM, for ever.
There seems to be no reason behind it, other than an OP need to herd cats.

While the universe may be infinite, human belief systems appear closed and finite.
What does it matter how today’s technology operates, it is only an ephemeral aberration.

What has RPM got to do with anything. RPM must be multiplied by torque to get any usable power.
The consideration of RPM alone, without a torque curve, is not engineering, it is meaningless.
What is engineering if it is not the management of energy flow.

A bicycle has two accelerator pedals, yet it is more energy efficient than an IC engine.
 
  • #94
PhysicoRaj said:
That's what, accelerator pedal is connected to throttle butterfly and AFR control, or, throttle butterfly only. Connecting the accelerator pedal to AFR is manufacturer's choice. See Baluncore's posts:
In a GASOLINE engine this is not valied

The accelerator pedal in a gasoline engine is not connected directly to the feul pump thus does not alter the AFR, any modifications in the AFR by the ECU in modern cars are meant for other benefits we have already stated this many times

I asked you and Baluncore for proof of a gasoline fuel pump that is driven by the accelerator pedal but you have proved nothing yet
I never said throttle range is 10%. What I said was since AFR screw can change rpm by only 10%, throttle is provided.
And I told you that this incrementation is meaningless and equals the increase made by valve timing, and such actions are never utilized, so this prove nothing that relates the accelerator pedal to rpm

I just thought that max torque occurs at max rpm. If that's true, my engine's redline is 6750 rpm.
Sorry, I could not fetch more numbers.
I'm also sorry because without defined numbers this whole concept can go no further ...
 
Last edited:
  • #95
Baluncore said:
Without question or context, this thread will go in circles at a high RPM, for ever.
There seems to be no reason behind it, other than an OP need to herd cats.

While the universe may be infinite, human belief systems appear closed and finite.
What does it matter how today’s technology operates, it is only an ephemeral aberration.

What has RPM got to do with anything. RPM must be multiplied by torque to get any usable power.
The consideration of RPM alone, without a torque curve, is not engineering, it is meaningless.
What is engineering if it is not the management of energy flow.

A bicycle has two accelerator pedals, yet it is more energy efficient than an IC engine.
Obviously, either you didn't read all the comments or you consider yourself one of these cats, no offence

The importance of this topic is to aid in defining which factors have more influence on the rpm of an engine (gasoline in particular) when pressing the accelerator pedal so we can isolate the less influential or less effective ones and from there you should have better understanding of the whole subject, and as of now it appears clearly that this ain't a straitforward matter, hence all the discussion that was made, and I do think it was fruitful and very informative
Pity you don't see it like this

about torque curve Physicoraj brought one and I have been asking for numbers all the time, so if there was a lack of numbers then this thread should help in defining this problem in hope more sceintific research will be done about it

Finally, if you don't like the thread you could simply ignore it all together
 
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  • #96
Sailor said:
which factors have more influence on the rpm of an engine (gasoline in particular)
Sailor, is this your final question? Did you get a satisfactory answer to it?
 
  • #97
PhysicoRaj said:
Sailor, is this your final question? Did you get a satisfactory answer to it?
Yes I believe I have got satisfactory answers to most of the questions

The only one that is left is in post #69

But unless this question had been dealt with before it might require a lab experiment
 
  • #98
Sailor said:
Yes I believe I have got satisfactory answers to most of the questions

The only one that is left is in post #69

But unless this question had been dealt with before it might require a lab experiment

So you are expecting a proof for the accelerator pedal linked to AFR regulator, which in turn is directly indulged in increasing RPM of engine(accelerating the vehicle.)
And your view is that even though the AFR regulator might be linked to the accelerator pedal, it might be due to some other reason (economy reasons according to you) and not for increasing RPM.
And you need solid proof.
 
  • #99
PhysicoRaj said:
So you are expecting a proof for the accelerator pedal linked to AFR regulator, which in turn is directly indulged in increasing RPM of engine(accelerating the vehicle.)
And your view is that even though the AFR regulator might be linked to the accelerator pedal, it might be due to some other reason (economy reasons according to you) and not for increasing RPM.
And you need solid proof.
Exactly, that is what I'm saying, that the alteration in AFR is never meant to accelerate the gasoline engine normaly through the accelerator pedal

The proof is meant pecisely for the linkage between the accelerator pedal and a FEUL PUMP in a gasoline engine in particular as Balucore has claimed rather that just discribing an AFR device
 
  • #100
Sailor said:
The importance of this topic is to aid in defining which factors have more influence on the rpm of an engine (gasoline in particular) when pressing the accelerator pedal so we can isolate the less influential or less effective ones and from there you should have better understanding of the whole subject, and as of now it appears clearly that this ain't a straitforward matter, hence all the discussion that was made, and I do think it was fruitful and very informative
Pity you don't see it like this
I do understand the subject very well indeed. I just don't see the point of a reductionist classification that demands some things to be more fixed and some things to be more variable. The world is not that simple, as you may now be beginning to realize since you have written;
Sailor said:
… as of now it appears clearly that this ain't a straitforward matter …

Sailor said:
Finally, if you don't like the thread you could simply ignore it all together
Then you would never learn anything about the wonderful variability of this universe, nor how to ask a rational question that can actually be answered.

Susan Sontag said:
The only interesting answers are those which destroy the questions.
 
  • #101
Sailor said:
Exactly, that is what I'm saying

The alteration in AFR is never meant to accelerate the gasoline engine normaly throw the accelerator pedal

The proof is meant pecisely for the linkage between the accelerator and a FEUL PUMP in a gasoline engine in particular as Balucore has claimed rather that just discribing an AFR device

I've tried enough to produce proof. Let's see if any other person can provide more valuable, plausible and satisfactory proof.
Hope you get answers (proofs) to your questions.:smile:

[BTW, congrats, the thread has crossed 100 posts ;)]
 
  • #102
This thread is in some serious need of moderation. May be easier to close it and start again with a better defined scope.

Quite how this has spiralled to a hundered posts ill never know.

It's got to the point where I have no idea what is going on. As the OP seems to have concluded things that are the exact opposite of what people said.
 
  • #103
Baluncore said:
I do understand the subject very well indeed. I just don't see the point of a reductionist classification that demands some things to be more fixed and some things to be more variable. The world is not that simple, as you may now be beginning to realize since you have written;
Yes it is not simple, and nothing is absolutly constant in universe not even the quantaties we have described here, but when you can define the more affecting factors which in this case are the variables, then, you know where to concentrate the most and make your modifications more effecient

Si in this case anyone who needed to tune his engine up for better performance and thought that he better start with adding more fuel to alter the AFR all the time, I suppose that after reading this thread his focus should be directed solely towards the volumetric effeciency and should hold the AFR at it's most optimum value without alteration, ofcourse UNLESS he was looking for other qualities other than performance
Then you would never learn anything about the wonderful variability of this universe, nor how to ask a rational question that can actually be answered.
thanks for the notion Baluncore, I understand what you are trying to say
 
  • #104
PhysicoRaj said:
I've tried enough to produce proof. Let's see if any other person can provide more valuable, plausible and satisfactory proof.
Hope you get answers (proofs) to your questions.:smile:

[BTW, congrats, the thread has crossed 100 posts ;)]

Thanks PhysicoRaj
 
  • #105
xxChrisxx said:
This thread is in some serious need of moderation. May be easier to close it and start again with a better defined scope.

Quite how this has spiralled to a hundered posts ill never know.

It's got to the point where I have no idea what is going on. As the OP seems to have concluded things that are the exact opposite of what people said.
Other than your explanation of CR which I have replied to I see nothing wrong with the thread

What THINGS do you refer to ?

Perhaps if you can't understand what has been said at least you can try to express what these points are

Any ways I think I got the answers I was looking for so you are free to start you own thread and state whatever you wish in it
 
  • #106
Locked Pending moderation
 
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