[Breezin]

'Butt dyno'. Love it!
Thinking of taking a PhD in mechanical engineering... this discussion to be heavily cited! 

[Starpeve]

This is a mistake, but do not worry many people do it. A WOT dyno run cannot be used to extrapolate part throttle or transient as you imply on your last sentence. Unless you get more displacement, the additional power at WOT is always the result of lesser power at part throttle.

The engine lost its harmonics scavenging systems both at the intake and exhaust to get more flow when it was limited, i.e. at high throttle opening and WOT. This means the engine will give more torque than stock, but only at that time; and it will give less when these systems were working. There is threshold on the throttle opening where the power is going to be worse than stock. Usually that is under around 60-70% throttle opening.

It means that when you are cruising, or giving a bit of gas, the engine will produce less torque than stock. the upgraded air filter gives better transient, which makes the butt dyno feel that you get more, but you do not. While this is great in racing condition, it also makes keeping the same speed harder; the bike becomes a bit more on/off.  It is similar to how stiffer suspensions can make its user believe he goes faster, as he feels more bumps and Gs. I had quite some passengers in my track car that said it felt slow compared to their car. They were very surprised seeing it was actually running 2 seconds a lap faster than them. Do not be deceived by your feelings !

Fillings, nothing more than fillings....
Fillings, fillings of lurve....
Sorry, I got the music in me!😁😁👍

[gizzo]

This is a mistake, but do not worry many people do it. A WOT dyno run cannot be used to extrapolate part throttle or transient as you imply on your last sentence. Unless you get more displacement, the additional power at WOT is always the result of lesser power at part throttle.

The engine lost its harmonics scavenging systems both at the intake and exhaust to get more flow when it was limited, i.e. at high throttle opening and WOT. This means the engine will give more torque than stock, but only at that time; and it will give less when these systems were working. There is threshold on the throttle opening where the power is going to be worse than stock. Usually that is under around 60-70% throttle opening.

It means that when you are cruising, or giving a bit of gas, the engine will produce less torque than stock. the upgraded air filter gives better transient, which makes the butt dyno feel that you get more, but you do not. While this is great in racing condition, it also makes keeping the same speed harder; the bike becomes a bit more on/off.  It is similar to how stiffer suspensions can make its user believe he goes faster, as he feels more bumps and Gs. I had quite some passengers in my track car that said it felt slow compared to their car. They were very surprised seeing it was actually running 2 seconds a lap faster than them. Do not be deceived by your feelings !

It's OK, he's only going to be operating at the rev limiter in 1st anyway 

[GlennF]

'Butt dyno'. Love it!
Thinking of taking a PhD in mechanical engineering... this discussion to be heavily cited! 

lol ...  be sure to talk lots about Carnot Cycle heat engines and entropy and enthalpy and thermodynamic system equilibrium cycles and reversible adiabatic expansion .. and, you know ...  stuff

... or you could just follow the modern trend of declaring anything hard to understand, especially if it involves math, as a conspiracy and hence obviously bad for you

[dcolak]

This is a mistake, but do not worry many people do it. A WOT dyno run cannot be used to extrapolate part throttle or transient as you imply on your last sentence. Unless you get more displacement, the additional power at WOT is always the result of lesser power at part throttle.

The engine lost its harmonics scavenging systems both at the intake and exhaust to get more flow when it was limited, i.e. at high throttle opening and WOT. This means the engine will give more torque than stock, but only at that time; and it will give less when these systems were working. There is threshold on the throttle opening where the power is going to be worse than stock. Usually that is under around 60-70% throttle opening.

It means that when you are cruising, or giving a bit of gas, the engine will produce less torque than stock. the upgraded air filter gives better transient, which makes the butt dyno feel that you get more, but you do not. While this is great in racing condition, it also makes keeping the same speed harder; the bike becomes a bit more on/off.  It is similar to how stiffer suspensions can make its user believe he goes faster, as he feels more bumps and Gs. I had quite some passengers in my track car that said it felt slow compared to their car. They were very surprised seeing it was actually running 2 seconds a lap faster than them. Do not be deceived by your feelings !

If the fuel mapping is correct you will see better torque at all throttle openings. Why do you think ECU will restrict the fueling because of more air getting into the engine and being easier to get it out of the system through the new exhaust cans? It will compensate no matter what position throttle is in.

[Starpeve]

If the fuel mapping is correct you will see better torque at all throttle openings. Why do you think ECU will restrict the fueling because of more air getting into the engine and being easier to get it out of the system through the new exhaust cans? It will compensate no matter what position throttle is in.

👍

[cyril31]

If the fuel mapping is correct you will see better torque at all throttle openings. Why do you think ECU will restrict the fueling because of more air getting into the engine and being easier to get it out of the system through the new exhaust cans? It will compensate no matter what position throttle is in.

No, you will not, as the problem is not fuel but air, and i never said that, thank you.

Like starpeve you believe the ECU does some kind of black magic. It does not, it will send whatever fuel is needed to reach the target AFR, this is not an alphaN system nor a carburetor.

The hard part in an engine that uses injection is getting air in and out. Fuel is not a limiting factor. The problem here is that less air is entering the cylinders for the same throttle position when at part throttle.

By removing the airbox cover, you are discarding the system that helps push air in the cylinders.
By removing the stock silencers and replacing them with a straight through, you are discarding the scavenging system that helps pump burnt gas out of the cylinders and replace it with fresh mixture when valve overlap happens.

Both these effects take place around a specific rpm and its first and second multiple (called second and third harmonics), on a race engine they will be set for high rpms (and you will lose top end power by changing the silencer and/or the airbox on that kind of bike. The only reason to ditch the silencer is weight gain).
On bikes like ours, that were never meant with top end power in mind, they are set to work at lower revs. They can restrict flow, and since they are not set for max power, this is why they get removed. Put  bigger exhaust cans and a bigger airbox, and these systems can be used without restricting the maximum amount of air that can enter the engine... but there is no room for that.

Anyway, removing these systems when they are not tuned for max power and restrict max engine flow allows more maximum flow, which is in effect when the throttle is opened a lot.

You will find countless pages of explanations regarding this on google, search for "airbox tuning" or "airbox resonnance" , and exhaust scavenging effect.

[Starpeve]

No, you will not, as the problem is not fuel but air, and i never said that, thank you.

Like starpeve you believe the ECU does some kind of black magic. It does not, it will send whatever fuel is needed to reach the target AFR, this is not an alphaN system nor a carburetor.

The hard part in an engine that uses injection is getting air in and out. Fuel is not a limiting factor. The problem here is that less air is entering the cylinders for the same throttle position when at part throttle.

By removing the airbox cover, you are discarding the system that helps push air in the cylinders.
By removing the stock silencers and replacing them with a straight through, you are discarding the scavenging system that helps pump burnt gas out of the cylinders and replace it with fresh mixture when valve overlap happens.

Both these effects take place around a specific rpm and its first and second multiple (called second and third harmonics), on a race engine they will be set for high rpms (and you will lose top end power by changing the silencer and/or the airbox on that kind of bike. The only reason to ditch the silencer is weight gain).
On bikes like ours, that were never meant with top end power in mind, they are set to work at lower revs. They can restrict flow, and since they are not set for max power, this is why they get removed. Put  bigger exhaust cans and a bigger airbox, and these systems can be used without restricting the maximum amount of air that can enter the engine... but there is no room for that.

Anyway, removing these systems when they are not tuned for max power and restrict max engine flow allows more maximum flow, which is in effect when the throttle is opened a lot.

You will find countless pages of explanations regarding this on google, search for "airbox tuning" or "airbox resonnance" , and exhaust scavenging effect.

And yet you continue to deny or ignore my cpu example of the ls1 V8 example I’ve spoken off.
As I just posted elsewhere, are you aware the the 650’s cpu restricts fuel to the engine when it reads 5500 rpm from the crank angle sensor? Right where the torque drops off? For ‘engine protection’? I’m not talking about black magic, I’m talking about deliberate performance moderation on an engine which could possibly perform much better if allowed. Maybe not. But probably yes.
Steve

[gizzo]

LS1's love a tune because they were tuned so sloppily from new. They run too rich and ignition curves are choppy and all over the place. Who you ask depends on whether it was on purpose or by mistake. Here's a good read. It's old now but LS motors are no spring chickens, either. Note the part where they mention the power gain with a failing fuel pump dropping pressure and leaning the AFR. (Disclaimer: I've never owned an LS, this is just what I've learned from reading and chatting with owners. My own carb fed SBC and I6 motors gained power/economy after cam, head, displacement, exhaust and carb changes).

https://www.oztrack.com.au/2013-09-27-06-14-12/ls1-tuning-explained

I think you're both right. A well tuned from factory engine needs more than a tune to make big power gains. But one hamstrung from the factory, there's room for improvement.

[9fingers]

What a fantastic torque curve! No wonder that bike is so easy and fun to ride.
9fingers

[NVDucati]

...
By removing the stock silencers and replacing them with a straight through, you are discarding the scavenging system that helps pump burnt gas out of the cylinders and replace it with fresh mixture when valve overlap happens.

I think you are describing that "back pressure" slows the pace of (lets call them) gulps of exhaust to better match the valve overlap. Is that true?

I noticed right away that the 650s don't use a cross-over pipe or it is so very small I don't see it.
While impractical for the RE, you can have it both. A variable EXUP valve is widely used now a days.
You can see a short but clear explanation here: https://www.yamahapart.com/exhaustultimatepowervalveexup

As a more sane approach, a small (7/8") pitot tube could be run between two replacement silencers. A thousand years ago I worked on a project that converted a Lycoming 036 aircraft engine to run on propane. We found that these small tubes worked better than the original full diameter cross over tubes.

I guess my point is that cyril31 isn't wrong but avoiding the goal of better performance isn't necessarily right and certainly not impossible.

[Dr Mayhem]

And yet you continue to deny or ignore my cpu example of the ls1 V8 example I’ve spoken off.
As I just posted elsewhere, are you aware the the 650’s cpu restricts fuel to the engine when it reads 5500 rpm from the crank angle sensor? Right where the torque drops off? For ‘engine protection’? I’m not talking about black magic, I’m talking about deliberate performance moderation on an engine which could possibly perform much better if allowed. Maybe not. But probably yes.
Steve

Hmmm?.. and the wizards have no eyes, LoL

I see and easy 58-60 HP from this motor using the stock cams if you have a clue

[cyril31]

And yet you continue to deny or ignore my cpu example of the ls1 V8 example I’ve spoken off.
As I just posted elsewhere, are you aware the the 650’s cpu restricts fuel to the engine when it reads 5500 rpm from the crank angle sensor? Right where the torque drops off? For ‘engine protection’? I’m not talking about black magic, I’m talking about deliberate performance moderation on an engine which could possibly perform much better if allowed. Maybe not. But probably yes.
Steve

Yes, i ignore it because that engine has nothing to do with a twin 650cc SOHC bike engine.

No, i am not aware the ECU "restricts fuel", and neither are you. I am aware you claimed that in another thread, without giving any kind of evidence.

I am aware of your mindset, and i know you resent me each time i show your beliefs are either wrong or unproven. You are not the first, nor the last.
I cannot point you the crossroad and the path, but you will have to choose to walk it. But until you change your mindset to something more scientific and reasonable, you will improve your knowledge.

You are convinced the ECU cuts power, and that you will take every bit of information that seems to go toward your conviction as gospel that does not require any kind of proof. You will jump to conclusions in the same way, and you will discard every proof that shows you are wrong because it does not match what you believe. Case in point, you are ignoring the results of the thread owner here.


I am open to discussing your claim, but you have to realize that claiming something out of the ordinary requires solid proof and explanation.
Explain what you mean by "fuel restriction",give proof of its existence, and how this is a cause of limiting power. And then we will discuss. I do have a  pretty good idea of what you observed or were told though, and a very ordinary explanation of it already.

If you can prove your point I will believe you; i have no problem with accepting I am wrong. 

But right now, considering the complete absence of proof and explanation from you and your stance on the subject i hope you understand my doubts are pretty high.

[Dr Mayhem]

Yes, i ignore it because that engine has nothing to do with a twin 650cc SOHC bike engine.

No, i am not aware the ECU "restricts fuel", and neither are you. I am aware you claimed that in another thread, without giving any kind of evidence.

I am aware of your mindset, and i know you resent me each time i show your beliefs are either wrong or unproven. You are not the first, nor the last.
I cannot point you the crossroad and the path, but you will have to choose to walk it. But until you change your mindset to something more scientific and reasonable, you will improve your knowledge.

You are convinced the ECU cuts power, and that you will take every bit of information that seems to go toward your conviction as gospel that does not require any kind of proof. You will jump to conclusions in the same way, and you will discard every proof that shows you are wrong because it does not match what you believe. Case in point, you are ignoring the results of the thread owner here.


I am open to discussing your claim, but you have to realize that claiming something out of the ordinary requires solid proof and explanation.
Explain what you mean by "fuel restriction",give proof of its existence, and how this is a cause of limiting power. And then we will discuss. I do have a  pretty good idea of what you observed or were told though, and a very ordinary explanation of it already.

If you can prove your point I will believe you; i have no problem with accepting I am wrong. 

But right now, considering the complete absence of proof and explanation from you and your stance on the subject i hope you understand my doubts are pretty high.

LoL 

, are you aware the the 650’s cpu restricts fuel to the engine when it reads 5500 rpm from the crank angle sensor?

Lifted directly from the 650 service manual!!

Paranoid much??

[cyril31]

Doubting and asking for proof is not paranoia, it is science.

Believing everything you read in a book is exactly what religious guys tell you.

I found the info page 620, 606 in the pdf.

copy / paste.

16. Crank Position Sensor
It provides an alternating electrical pulse to the ECU, to determine crankshaft speed and TDC position of the piston in
compression stroke. This input will help the ECU to optimize both fuel injection as well as Ignition advance required to
suit the crankshaft rotation speed (RPM).
In the event throttle is wide open, leading to crankshaft speed above 5500 RPM, the high frequency electrical pulses from
the crank position sensor will prompt the ECU to restrict fuel supply so that the crank speed reduces to safe levels. This is
a safety aspect to prevent damage to moving engine parts.

Read the bold part now. Doesn't it strike you as odd that something tells you it not justs restricts fuel, but it prevents the engine from revving doing so ? Because if that was true, the engine would well, not rev higher than 6000. and yet it does.


Which made me think there is an error in that book - and I know there are tons, like that chapter that tells to top up oil level with brake fluid. But since it is an unordinary claim, i searched for proof ...

And I found it, with a google search. That section is a copy/paste of euro4 single cylinders engines from royal enfield.

 pdf page 178, the very same text. Which makes sense, on a single 500cc engine ...

http://www.royalenfieldlesite.fr/spip/IMG/pdf/manuel-entretien-roayl-enfield-500.pdf

There is a slight change though:

n the event the throttle is held wide open with gears in neutral, leading to crankshaft speed above 5500 RPM, thehigh frequency electrical pulses from the crank position sensor will prompt the ECU to restrict fuel supply so that thecrank speed reduces below 5000 RPM. This is a safety aspect to prevent damage to moving engine parts.

My bet is whoever copied this forgot this part in bold.