blinx's OFFICIAL EXHUAST THREAD velocity backpressure all explained here.


Some people on other forums disagree with this....
 
Well. In short, I just say back pressure is bad. Velocity is good.
And many replies are that they disagree blah blah blah.
 
Bon87 said:
I did, I copied and pasted your info :)
Click to expand...

did you site me? it would have been better if you just linked it, that way they could see our discussion's and we might even gain some members :nice:

give me the link to that form and that page where they are disucssing this, i feel like putting people in there place today ;)
 
I think the incorrect term 'back pressure' is what starts ****. The modern term is 'Volume vs Velocity'
 
Here is the test I have made:

I had OEM header 4-1 on my b16b. From the collector on heder I was running 70 mm pipe straight to muffler. So the pipe from collector point was going from the 60 to 70 mm. In low RPM I had sound like WAHHH WAHHH in very big time intervals, like exhaust was entering in reservoir and after a while letting it out.

My track time was: 14.288 sec

So I went out to find smaller pipe, I put straight pipe till muffler 61.8 mm inner diameter. There was no sound as I described.

My track time was: 14.048, then 14.040 and so on.

Than I put Vibrant ("clearence header" 4-2-1) and same 61.8 pipe. I had to brake to stay in 14 sec clas. (13.850) :nice::nice::nice::nice::clap:

As I read and tried so far, exhaust gas is going out at high speed, and have inertia, leaving negative pressure behind itself and positive in front, and when it goes out from collector it will hit the gas inside 70 mm (or 60mm) pipe. Also have in mind that gas will lover its temperature from the exit point of head, till collector and reduce its volume. (I used Thermal insulation tape).
Leaving negative pressure at collector is good for other cylinder, because it helps poll out its exhaust gas. This is why they make 1 and 4 and 2 and 3 collecting at one. Producers also intend to stop "returning" of pulse, like hytech making small chamber at certain distance from exhaust point.

There are so many things to be considered, but design of header and diameter and length of exhaust must be made for certain engine and its flow specifications. :angry:

When I go to two litter engine (as Blinx and Stephen said) I will have to use another header and pipe and start all process over. :mad:
 
I got told from my mechanic (im sure hes just full of ****, and try to make money) that my manifold had an air leak crack.... I didnt belive him cause, I think i would have heard if the manifold was cracked... anyway, I talk with him, try to see how "big" the crack is, cause a friend might weld it with a MIG... He said that u cant see it when the manifold is cold, only when it gets hot (lol? my engine doesnt work, how he saw that crack) anyways, that being said, he wants to void his warranty because Im not providing him a brand new part, and he says that, the manifold being crack will cause a lost of backpreassure, and cause the valves to overheat (lol? again) we all know due to blinx's that backpreassure his bad, how in a polite way i can tell them his a moron and that having no backpreassure wont causes valves to overheat ?

Thanks
 
bosniacrx said:
Here is the test I have made:

I had OEM header 4-1 on my b16b. From the collector on heder I was running 70 mm pipe straight to muffler. So the pipe from collector point was going from the 60 to 70 mm. In low RPM I had sound like WAHHH WAHHH in very big time intervals, like exhaust was entering in reservoir and after a while letting it out.

My track time was: 14.288 sec

So I went out to find smaller pipe, I put straight pipe till muffler 61.8 mm inner diameter. There was no sound as I described.

My track time was: 14.048, then 14.040 and so on.

Than I put Vibrant ("clearence header" 4-2-1) and same 61.8 pipe. I had to brake to stay in 14 sec clas. (13.850) :nice::nice::nice::nice::clap:

As I read and tried so far, exhaust gas is going out at high speed, and have inertia, leaving negative pressure behind itself and positive in front, and when it goes out from collector it will hit the gas inside 70 mm (or 60mm) pipe. Also have in mind that gas will lover its temperature from the exit point of head, till collector and reduce its volume. (I used Thermal insulation tape).
Leaving negative pressure at collector is good for other cylinder, because it helps poll out its exhaust gas. This is why they make 1 and 4 and 2 and 3 collecting at one. Producers also intend to stop "returning" of pulse, like hytech making small chamber at certain distance from exhaust point.

There are so many things to be considered, but design of header and diameter and length of exhaust must be made for certain engine and its flow specifications. :angry:

When I go to two litter engine (as Blinx and Stephen said) I will have to use another header and pipe and start all process over. :mad:
Click to expand...

You don't absolutely have to change your header when the two litre is done, you will have some power to be gained by changing headers but not too much in my opinion, but then again for NA cars every 1whp is so vital...

GekKey said:
he wants to void his warranty because Im not providing him a brand new part, and he says that, the manifold being crack will cause a lost of backpreassure, and cause the valves to overheat (lol? again) we all know due to blinx's that backpreassure his bad, how in a polite way i can tell them his a moron and that having no backpreassure wont causes valves to overheat ?
Thanks
Click to expand...

well what he is saying is partially true, my arguement about back pressure was based on the everything after the header, but you do need a certain amount of pressure in the header, a small amount but it needs to be there as the engine was designed to work that way. without that pressure the exhaust valves will come crashing down much harder which can damage a motor, thats why you should NEVER drive with the exhaust manifold disconnected from the head!! Now a tiny exhaust leak is not going to make this happen, my mothers car had a hole in the manifold for a few months before i repaired it and its fine now.

why cant you just let the motor idle till it heats up then have him show you the crack?
 
my current engine is broken... the main bearing spunned, and on so... alot of internal damage, 1 connecting rod broken, piston 3 & 4 are at 60psi, piston 2 at 120psi... it can barelly idle... anyways... i know its not a such airleak that will overheat the engine... ill get him to put heat tabs on the head...
 
no clue at all... when i bought the car the guy got it inspected before i could even get to the garage... so maybe it was damaged

the engine had 250k... i know its nothing for a honda but... dunno... bearing spunned
 
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