[SuziBlu]

If you take an exhaust off, or put one on, change it anyhow, and do not change the tuning, you will get a change in the behavior of the engine, and not always to the betterment.

I took my tail pipe off, only had extractors and a straight thru muffler, retuned it, and that made noticeable difference.

Was too loud and so had to put it back on, and retune, as once the pipe went back on, there was a greater restriction, and so it needed a fine tune.

[royce]

2stroker wrote:

Anyone who has driven a car even for 5 minutes without an exhaust will know what I am talking about. Completely removing an exhaust will make he car loose power at certain rev ranges and run poorly, backfiring when you back off etc as the cool outside air licks back up the pipes and then is expelled by the next pulse of hot exhaust gas. So what I am saying is that what comes after the extractors is as important as the extractors.

MacBear, I have already posted that 3 posts prior to yours, probably from the same google search. In actual fact what you are saying contradicts itself because you say backpressure is 100% myth but then say:

"A good or performance exhaust system, is one that has very little or No backpressure, with High velocity exhaust gases !!!"

To obtain air speed or "high velocity exhaust gases" you need to have some restriction in the flow and restricting the flow means that the flow is backed up to some degree and this creates pressure and that pressure is commonly refered to as backpressure. So you cannot have one without the other.

It is old terminoligy and probably doesn't properly describe the process but so are terms like vacuum which is used to describe suction when the word actually means "a volume of space that is essentially empty of matter"

Only cause the manifold is wrong, why dont Drag cars have full exhausts?

there is a point where the flow is as high as it gets without being a restriction, thats where you are aiming for after that you go backwards

[JrZook]

Gee good tech here on exhaust systems not so much on the topic of carbs. The twin carbs on the datto 1400 you were referring to were they twin side drafts? I'm assuming so, hence in this case each cylinder will have its individual carb sharing a common fuel bowl between two throats. Have a look at the post on sidedraft carbs that someone posted a link to. Then have a look through some of those links in the post about the guys that actually tested them on zuk engine with actual dyno data to show. That actual data shows quite a significant increase in power throughout the rev range (dyno run was started at 2k RPM) Besides the complexity of the manifold design I reckon its a great idea for the zuk on and offroad. A centrally located fuel bowl thats directly under the carb is the best design for an offraod vehicle when extreme angles are involved. All in all it comes really down the carb choice. The CV style bike or SU style carb here would be the better choice, due to their variable venturi design helping to keep air intake speeds up and fuel metering methods.

Anywoo what the go with these p-plate laws these days? Heard a rumor that no performance mods were allowed?

Dan

[TZAR]

JrZook wrote:

Gee good tech here on exhaust systems not so much on the topic of carbs.

Its okay Royce started it. Its fine cause he has a really small car so that means he has a huge penis. Just ask him he will tell you its true. I only know cause Bruce told me.

[2stroker]

Only cause the manifold is wrong, why dont Drag cars have full exhausts?

Because drag cars are not driven, they are aimed at a length of straight road staged to a high rpm and then accelerated through a very narrow rev range where they make their power, everywhere else they are virtually undrivable.

Why do circuit race cars still run exhausts, because they are driven, up and down through gears, accelerating and decelerating at different speeds under different loads, real world stuff.

[ball]

2stroker wrote:

Only cause the manifold is wrong, why dont Drag cars have full exhausts?

Because drag cars are not driven, they are aimed at a length of straight road staged to a high rpm and then accelerated through a very narrow rev range where they make their power, everywhere else they are virtually undrivable.

Why do circuit race cars still run exhausts, because they are driven, up and down through gears, accelerating and decelerating at different speeds under different loads, real world stuff.

Noise restrictions mainly

[MacDaddy]

2stroker wrote:

Anyone who has driven a car even for 5 minutes without an exhaust will know what I am talking about. Completely removing an exhaust will make he car loose power at certain rev ranges and run poorly, backfiring when you back off etc as the cool outside air licks back up the pipes and then is expelled by the next pulse of hot exhaust gas. So what I am saying is that what comes after the extractors is as important as the extractors.

MacBear, I have already posted that 3 posts prior to yours, probably from the same google search. In actual fact what you are saying contradicts itself because you say backpressure is 100% myth but then say:

"A good or performance exhaust system, is one that has very little or No backpressure, with High velocity exhaust gases !!!"

To obtain air speed or "high velocity exhaust gases" you need to have some restriction in the flow and restricting the flow means that the flow is backed up to some degree and this creates pressure and that pressure is commonly refered to as backpressure. So you cannot have one without the other.

It is old terminoligy and probably doesn't properly describe the process but so are terms like vacuum which is used to describe suction when the word actually means "a volume of space that is essentially empty of matter"

Hi 2stroker,

Yep i have had to disconnect the exhaust manifold from the head after a particularly deep creek crossing, where my old 1ltr Sierra stalled and sucked to much water up the exhaust, disconnecting it got me out, but yes the engine did have power lose and ran roughly...

Sorry didnt see it, but i was trying to make a point... everything i wrote with quotation marks, was from the internet, so, no i was not contradicting myself....

What you call restriction, i call channeling the exhaust gases away through a length of pipe, that is long enough so it doesnt interupt the efficient burning of the fuel air mix, it doesnt matter how big the pipe is, but it does have to be the right, tuned length... so how does restriction come into it ?

Ha ha, actually Suction, is not really suction, suction is better understood as creating a low pressure area, which the then high pressure area moves into, so there really is no suction, just different pressure areas moving from one to the other...

I dont want to start a devolving argument about who is right and who is wrong here, it appears we all have different beliefs about exhaust systems and back pressure...

But the " Preponderance " of evidence, all says that exhaust back pressure is a 100% Myth !!!

( My big word for the day " Preponderance ", meaning, in this context, greater in amount )

peaceout

[2stroker]

I agree with almost everything you have said MacBear, the only thing I have a problem with is how do you create higher velocity exhaust gases by adding a larger diameter pipe.

Looking up someones view point on the internet doesn't really equate to a" Preponderance of evidence" most things that you read will only be someones slant on it.

[MacDaddy]

2stroker wrote:

I agree with almost everything you have said MacBear, the only thing I have a problem with is how do you create higher velocity exhaust gases by adding a larger diameter pipe.

Looking up someones view point on the internet doesn't really equate to a" Preponderance of evidence" most things that you read will only be someones slant on it.

Hi 2strocker,

Well almost is better than nothing

Ok, i am sure Steknig is better qualified to answer this... but in my understanding, because there is a pipe to channel the exhaust gases away, you get a higher velocity within the pipe, than if you would without one, much like a Jet engine, also what Steknig said about the pulse wave through the pipe, if you can get the pulses in tune with the pipe length, it will have self drawing/propelling action...

And through my own knowledge of Air Flow, there is a thing called the Coanda effect, well known in the Aeronautical Industry, which basically says - The Faster the Air flows over a surface, the more the air will stick to a surface, and increase in speed, hence increase in velocity, and the airflow can then be directed in another direction !

Also, having an exhaust pipe with little or no restriction, and little or No backpressure, will by its own, increase exhaust velocity...

Cheers

peaceout

[steak_knife]

MacBear wrote:

2stroker wrote:

I agree with almost everything you have said MacBear, the only thing I have a problem with is how do you create higher velocity exhaust gases by adding a larger diameter pipe.

Looking up someones view point on the internet doesn't really equate to a" Preponderance of evidence" most things that you read will only be someones slant on it.

Hi 2strocker,

Well almost is better than nothing

Ok, i am sure Steknig is better qualified to answer this... but in my understanding, because there is a pipe to channel the exhaust gases away, you get a higher velocity within the pipe, than if you would without one, much like a Jet engine, also what Steknig said about the pulse wave through the pipe, if you can get the pulses in tune with the pipe length, it will have self drawing/propelling action...

And through my own knowledge of Air Flow, there is a thing called the Coanda effect, well known in the Aeronautical Industry, which basically says - The Faster the Air flows over a surface, the more the air will stick to a surface, and increase in speed, hence increase in velocity, and the airflow can then be directed in another direction !

Also, having an exhaust pipe with little or no restriction, and little or No backpressure, will by its own, increase exhaust velocity...

Cheers

peaceout

I didn't say any of that!!!!

[MacDaddy]

steknig wrote:

MacBear wrote:

2stroker wrote:

I agree with almost everything you have said MacBear, the only thing I have a problem with is how do you create higher velocity exhaust gases by adding a larger diameter pipe.

Looking up someones view point on the internet doesn't really equate to a" Preponderance of evidence" most things that you read will only be someones slant on it.

Hi 2strocker,

Well almost is better than nothing

Ok, i am sure Steknig is better qualified to answer this... but in my understanding, because there is a pipe to channel the exhaust gases away, you get a higher velocity within the pipe, than if you would without one, much like a Jet engine, also what Steknig said about the pulse wave through the pipe, if you can get the pulses in tune with the pipe length, it will have self drawing/propelling action...

And through my own knowledge of Air Flow, there is a thing called the Coanda effect, well known in the Aeronautical Industry, which basically says - The Faster the Air flows over a surface, the more the air will stick to a surface, and increase in speed, hence increase in velocity, and the airflow can then be directed in another direction !

Also, having an exhaust pipe with little or no restriction, and little or No backpressure, will by its own, increase exhaust velocity...

Cheers

peaceout

I didn't say any of that!!!!

Hi Steknig,

I did say right at the beginning, that this is my understanding of it...
I only mentioned you because of your more qualified understanding of exhaust systems, and you said something about the pulses, and that got me thinking, and then i added my understanding of the pulses and their actions...

I know you didnt say any of that... if i worded it so that you thought i was putting words into your mouth, then my bad , and accept my apologies...

Everything i wrote is my opinion and understanding... accept for the Coanda effect, that is real...


peaceout peaceout peaceout peaceout peaceout

[steak_knife]

WHAT EVA!!!!