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

[Sailor]

Now if I were to answer this question my self

how much could V3 differ from V1 and still be combustible ?

I would say that it depends on many variables such as air temperature, density, rpm besides the CR and AFR values,

these variables could then be measured and monitored by sensors, now whether this is the case with Valvetronic or not, I'm not sure, from what I've read so far I think there could be a defined value that is set for the minimum amount of air that enters the cylinder at idle

What I'm trying to find is the V3/V2 ratio that should be combustible at minimum save we have a stoichiometric mixture

 

[Sailor]

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”.

when you referred to carburetors in your previous comment I thought you were talking about gasoline engines specifically,

what you describe here is how the accelerator pedal in a diesel engine increases the rpm

However, if you are referring to a gasoline engine that has it's accelerator pedal attached to a fuel pump, then this would be interesting, and I would then ask you for links that entails this

 

[Sailor]

You mean this?

This is not true for all engines.

Edit: As Baluncore said, it depends.

There are other points as wellCan you confirm that there are gasoline engines that utilize AFR solely to increase rpm ?

 

[PhysicoRaj]

Here are some images of the carburettor from my motorcycle. I found the manual and looked for the carburettor, found out the Air to fuel ratio controlling screw and the throttle housing location.

This is the complete carburettor:

This is the A/F ratio controlling screw (I have a screw driver at it):

This is the throttle housing and control cable (look at the screw driver):

I turned on the engine and set out to test:
When I turn the A/F ratio screw, I can change the rpm in any position of the throttle.
When I open the throttle, it also increases the rpm, at any angle of the A/F control screw.
Note that the A/F screw can be turned by 180 degrees on both sides, can have a considerable effect on rpm.

 

[Sailor]

Here are some images of the carburettor from my motorcycle. I found the manual and looked for the carburettor, found out the Air to fuel ratio controlling screw and the throttle housing location.

This is the complete carburettor:


This is the A/F ratio controlling screw (I have a screw driver at it):


This is the throttle housing and control cable (look at the screw driver):


I turned on the engine and set out to test:
When I turn the A/F ratio screw, I can change the rpm in any position of the throttle.
When I open the throttle, it also increases the rpm, at any angle of the A/F control screw.
Note that the A/F screw can be turned by 180 degrees on both sides, can have a considerable effect on rpm.

thanks PhysicoRaj for the nice post,

can you indicate the values of rpm you're having ?, could you vary the rpm from idle to redline ?

because only then we can say that varying AFR in a gasoline engine could substitute air flow rate as an influential factor otherwise it would just be similar to how θ can alter the rpm which isn't sufficient enough to be considered separately in a gasoline engine

 

[PhysicoRaj]

thanks PhysicoRaj for the nice post,

can you indicate the values of rpm you're having ?, could you vary the rpm from idle to redline ?

because only then we can say that varying AFR in a gasoline engine could substitute air flow rate as an influential factor otherwise it would just be similar to how θ can alter the rpm which isn't sufficient enough to be considered separately in a gasoline engine

In the manual it is stated that the idle rpm is about 1400 rpm. The manual doesn't say how much it can be varied by the A/F screw, but I am going to guess, I could alter it by around 1000 rpm. So with the A/F control screw, I can vary the rpm as $1400\pm1000$ rpm. But not to the redline (which is around 10500 I guess).

Important note: I recently found out in the manual that the A/F screw is not linear. That is, With different positions of the throttle, different changes in rpm can be made by the same amount of turn of the A/F screw. That's why I managed to give you a value at the idle state.

 

[Sailor]

In the manual it is stated that the idle rpm is about 1400 rpm. The manual doesn't say how much it can be varied by the A/F screw, but I am going to guess, I could alter it by around 1000 rpm. So with the A/F control screw, I can vary the rpm as $1400\pm1000$ rpm. But not to the redline (which is around 10500 I guess).

since the redline is at 10500 then you are only allowed to make less than 10% modification to the rpm, so I think we can say that the change in rpm as a result of varying the AFR is actually a side effect of a more direct function which could be increasing/ lowering the consumption rate or perhaps it's related somehow to NHV or something or it might aid in fine tuning the idle rpm ...

also note that for the gasoline engine to have a reasonable efficient combustion the variation in AFR should be kept that much small, because if these variations were to be open to the extreme without any restrictions then you could either flood the engine or kill it ...

 

[Sailor]

Important note: I recently found out in the manual that the A/F screw is not linear. That is, With different positions of the throttle, different changes in rpm can be made by the same amount of turn of the A/F screw. That's why I managed to give you a value at the idle state.

Maybe they do not want you to touch it in the first place

 

[PhysicoRaj]

Recent update: I opened the throttle slightly more than half, turned the A/F ratio screw to the max extent and the tachometer almost touched the redline!

My example of my carburettor was not to state that my bike has A/F ratio as the sole reason for revving up. I am just asserting that A/F ratio can have a significant effect on rpm. This convinces that A/F ratio is variable, but independent of throttle in my engine. Other engines with computerized fuel injections do have some means of altering A/F ratio as the accelerator pedal is pressed.

Conclusion: A/F ratio affects rpm. It is left to the discretion of the manufacturer of the engine to decide whether he wants it constant or variable through out the rpm range.

 

[PhysicoRaj]

Maybe they do not want you to touch it in the first place

Then they would not provide a screw

since the redline is at 10500 then you are only allowed to make less than 10% modification to the rpm, so I think we can say that the change in rpm as a result of varying the AFR is actually a side effect of a more direct function which could be increasing/ lowering the consumption rate or perhaps it's related somehow to NHV or something or it might aid in fine tuning the idle rpm ...

I am just guessing the redline. I can give you the exact value later.
10% modification can have a huge effect on rpm when the throttle is considerably open, since A/F screw is non-linear. That's why I got the redline with throttle more than half open and A/F to the max. extent.

 

[Sailor]

Recent update: I opened the throttle slightly more than half, turned the A/F ratio screw to the max extent and the tachometer almost touched the redline!

My example of my carburettor was not to state that my bike has A/F ratio as the sole reason for revving up. I am just asserting that A/F ratio can have a significant effect on rpm. This convinces that A/F ratio is variable, but constant in my engine. Other engines with computerized fuel injections do have some means of altering A/F ratio as the accelerator pedal is pressed.

Conclusion: A/F ratio affects rpm. It is left to the discretion of the manufacturer of the engine to decide whether he wants it constant or variable through out the rpm range.

A/F ofcourse does affect rpm like for example if you would have 0 AFR then you will have 0 rpm but more important is you would actually have 0 rpm much earlier than that I'm guessing around 5 or even 6, a little higher ratio and you should now have extremely lean mixure that is not suffecient enough for normal usage, again this means you have a very narrow band in a gasoline engine to deal with which is not useful for varying the rpm on it's own like the other factors

Now back to your experiment, it is very important to mention the rpm values before and after the variation in AFR, only then we can build a solid conclusion about it

 

[Sailor]

Then they would not provide a screw


I am just guessing the redline. I can give you the exact value later.
10% modification can have a huge effect on rpm when the throttle is considerably open, since A/F screw is non-linear. That's why I got the redline with throttle more than half open and A/F to the max. extent.

Awaiting for the exact values ...

10% isn't suffecient enough to make it an effective factor in the processs, this could be equal to the variation in valve timing for example which is a feature utilized for tuning power and effeciency and not to increase rpm, even though the rpm might actally change a little from it

 

[PhysicoRaj]

A/F ofcourse does affect rpm..

This is the answer to post #1.

...again this means you have a very narrow band in a gasoline engine to deal with which is not useful for varying the rpm on it's own like the other factors

That's why there's something called the throttle.
Okay, you are talking about gasoline engines. See my quote, I have added something:

This convinces that A/F ratio is variable, but independent of throttle in my engine. Other engines with computerized fuel injections do have some means of altering A/F ratio as the accelerator pedal is pressed.

Now back to your experiment, it is very important to mention the rpm values before and after the variation in AFR, only then we can build a solid conclusion about it

I searched the net and got the info that my bike gives maximum torque at 6750 rpm. So I am guessing that must be the limit. Manual says idle is 1400 rpm.
At throttle slightly open, variation in rpm due to AFR change was 1000 rpm. With throttle half open, same amount of change in AFR got me to the redline.

 

[Ranger Mike]

pardon me for raining on you parade but that screw on the carb is to adjust the idle speed of the engine. If there are two screws present, one is for idle adjust and the other is low rpm idle richness adjustment. These have no other use than to keep the engine running when the throttle is not in use. If you will read the legend you will find number 8 and number 10 jets. These are jets that are set by the factory. NOTE - MAIN JET controls the Air/ Fuel Ratio. Nothing the rider can do can adjust the A/F ratio. This is to say, there is a metering hole in the jet. The amount of gasoline passing thru the jet is fixed. What is not fixed is the amount of air passing thru the carb and the throttle controls this. Nothing the rider can do can adjust the compression ration. Both are fixed. This engine has a 8 to 1 compression ratio and you can not change it. Also the timing is set and unless the operator has access to a timing light and degree wheel, the timing is set for idle and for the amount of spark advance. The only thing the rider can do it twist the throttle and let more air into the engine to be mixed with the fixed amount of gasoline as dictated by the JET.

Now Chris xx and Jack have both taken a lot of time to explain these things but unless you can grasp the concept that this fixed JET metering out gasoline is constant as is the compression ration , then we can not continue to post. Savvy?

 

[PhysicoRaj]

pardon me for raining on you parade but that screw on the carb is to adjust the idle speed of the engine. If there are two screws present, one is for idle adjust and the other is low rpm idle richness adjustment. These have no other use than to keep the engine running when the throttle is not in use. If you will read the legend you will find number 8 and number 10 jets. These are jets that are set by the factory. NOTE - MAIN JET controls the Air/ Fuel Ratio. Nothing the rider can do can adjust the A/F ratio. This is to say, there is a metering hole in the jet. The amount of gasoline passing thru the jet is fixed. What is not fixed is the amount of air passing thru the carb and the throttle controls this. Nothing the rider can do can adjust the compression ration. Both are fixed. This engine has a 8 to 1 compression ratio and you can not change it. Also the timing is set and unless the operator has access to a timing light and degree wheel, the timing is set for idle and for the amount of spark advance. The only thing the rider can do it twist the throttle and let more air into the engine to be mixed with the fixed amount of gasoline as dictated by the JET.

Now Chris xx and Jack have both taken a lot of time to explain these things but unless you can grasp the concept that this fixed JET metering out gasoline is constant as is the compression ration , then we can not continue to post. Savvy?

Ranger Mike, my manual says that is the main jet screw. And main jet adjusts the A/F ratio. Either the manual is wrong or I'm turning the wrong screw?

 

[Ranger Mike]

correct..it is for the purpose of setting the idle rpm. But note that the adjustment screw only permits gasoline to enter the carb during idle. If you observe, t here is another passage next to the main jet fuel feed that i think is the idle fuel feed passage. Once sufficent rpm is achieved the main carb circuit takes over. Also note that the main jet is fixed. Again the diameter of the main jet dictates the final fuel/air ratio and this can be assumed to be at wide open throttle.
So you set the throttle stop needle that keeps the slide body open enough to keep the engine running and adjust the idle fuel mix to trickle in enough gas so when you twist the throttle there is enough fuel to make transition to the main fuel circuit smooth with no stumbling ( off idle response).
Once there is enough RPM the engine is totally on the main fuel jet.

 

[Sailor]

This is the answer to post #1.

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 why there's something called the throttle.
Okay, you are talking about gasoline engines. See my quote, I have added something:

Throttle range is much wider than the 10% you have stated, there is no relation between them

I searched the net and got the info that my bike gives maximum torque at 6750 rpm. So I am guessing that must be the limit. Manual says idle is 1400 rpm.
At throttle slightly open, variation in rpm due to AFR change was 1000 rpm. With throttle half open, same amount of change in AFR got me to the redline.

Your point isn't clear

What should the maximum torque indicate in here

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

 

[PhysicoRaj]

correct..it is for the purpose of setting the idle rpm. But note that the adjustment screw only permits gasoline to enter the carb during idle. Once sufficent rpm is achieved the main carb circuit takes over. Also note tbat the main jet is fixed. Again the diameter of the main jet dictates the final fuel/air ratio and this can be assumed to be at wide open throttle.

But even when I 'half' opened the throttle, I could register a significant change in rpm when I turned that screw. That screw can be operated even while riding (I've used my nails to lower it when I am low on gas. Then I open the throttle fully to get more torque.)
So I guess that even if is an idle rpm adjuster, is connected to the main jet and somehow aletrs A/F ratio, resulting in change in rpm.

 

[Ranger Mike]

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.

 

[Sailor]

pardon me for raining on you parade but that screw on the carb is to adjust the idle speed of the engine. If there are two screws present, one is for idle adjust and the other is low rpm idle richness adjustment. These have no other use than to keep the engine running when the throttle is not in use. If you will read the legend you will find number 8 and number 10 jets. These are jets that are set by the factory. NOTE - MAIN JET controls the Air/ Fuel Ratio. Nothing the rider can do can adjust the A/F ratio. This is to say, there is a metering hole in the jet. The amount of gasoline passing thru the jet is fixed. What is not fixed is the amount of air passing thru the carb and the throttle controls this. Nothing the rider can do can adjust the compression ration. Both are fixed. This engine has a 8 to 1 compression ratio and you can not change it. Also the timing is set and unless the operator has access to a timing light and degree wheel, the timing is set for idle and for the amount of spark advance. The only thing the rider can do it twist the throttle and let more air into the engine to be mixed with the fixed amount of gasoline as dictated by the JET.

Now Chris xx and Jack have both taken a lot of time to explain these things but unless you can grasp the concept that this fixed JET metering out gasoline is constant as is the compression ration , then we can not continue to post. Savvy?

Thanks sgain Rabger for your input,

As for the compression ratio and the ignition rate I think were discussed thoroughly and I have made a explanation of what I meant about the variation in compression contrary to what Chris has stated

Ignition rate of course has no effect whatsoever regardless of it being constant or vsriable because it's a driven entity not a driving one

 

[PhysicoRaj]

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.

 

[PhysicoRaj]

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:

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”.

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.

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.

 

[Baluncore]

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.

 

[Sailor]

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 ...

 

[Sailor]

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

 

[PhysicoRaj]

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?

 

[Sailor]

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

 

[PhysicoRaj]

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.

 

[Sailor]

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

 

[Baluncore]

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;

… as of now it appears clearly that this ain't a straitforward matter …

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.

The only interesting answers are those which destroy the questions.

 

[PhysicoRaj]

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.

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

 

[xxChrisxx]

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.

 

[Sailor]

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

 

[Sailor]

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.

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

Thanks PhysicoRaj

 

[Sailor]

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