T-Moss or M.Yount,or exhaust guru's come in

willys1 · Jun 11, 2005

90mustangGT said:
Once again, backpressure is always bad. The fact is that larger exaust will cause more backpressure if the energy and volume of the air isn't sufficient to push the gas out of the car. I have a pnumatic (sp) (air powered) vaccume cleaner with no mechanical parts except a on/off valve. So how do you turn 90+psi into vaccume? Well it has six small ports that face towards the bag. When you squeeze the trigger the air is blown away from the nozel, causing a vaccume. Exaust works the same.

Why would stock headers work best in a stock motor for low end torque? Well even though they are kinked, these kinks act like venturie tubes in a carb to speed up the air, but not allow it to blow back in. Forming a chamber of vaccume behind the kinks so when the exaust opens up there is less volume of gas and actually sucks the exaust up and increases velosity.

HUH?? I got a 5.0,not a Hoover The kinks allow it to flow better? Dude,put down the pipe and walk away!!

5spd GT · Jun 11, 2005

Michael Yount said:
I swore to my buddies based on SOTP that the shorties improved mine -- the dyno data seemed to tell a different story.

SOTP data is extremely unreliable (gains or losses), and if you changed other things at the same time -- well, the fact is you don't really know with certainty what difference your Macs made.

I added more things by the time I hit the track next. Not all at once with the headers. The headers went on seperate. I felt a slight difference. Something noticeable. I have a self-proclaimed good SOTP feel. My friends always come to me or ask me what this or that car will run after I ride in it. I can tune out the smoothness or harshness of the acceleration and actually "feel" a difference. In my eyes...I gained...and in my feel...I gained. These are equal length headers...those stock ones were way to small and seeminly restrictive.

I see it as pretty reliable in my case...not others...because that is them...not me. I have been very accurate with my predictions and "feelings" when I compared them at the track. I keep calling it like the Babe

Jason, I'm with you on this one

04sleeper · Jun 11, 2005

David,

With your setup I would go with the 1 5/8" as well. My car having stock unported heads is what I was refering to.

Billy,

Sounds good, just give me a call whenever is good.

Kevin

Michael Yount · Jun 11, 2005

"I can tune out the smoothness or harshness of the acceleration and actually "feel" a difference. In my eyes...I gained...and in my feel...I gained."

Using the Force no doubt....

5spd GT · Jun 11, 2005

Michael Yount said:
"I can tune out the smoothness or harshness of the acceleration and actually "feel" a difference. In my eyes...I gained...and in my feel...I gained."

Using the Force no doubt....

Not a bad movie

90mustangGT · Jun 11, 2005

willys1 said:
HUH?? I got a 5.0,not a Hoover The kinks allow it to flow better? Dude,put down the pipe and walk away!!

No reefer here, I was posting that to prove scavaging and how the header runners act like the ports on the pnumatic vaccume, the gas leaving one runner causes an area of negative pressure pulling gas out of the other runner. I didn't say anything about flow except how scavanging will increase flow.

An bodies of equal amount of mass pushed one through a larger hole and a smaller hole can be done, but the mass is going to have to move much faster through the smaller hole. More speed equals more scavaging.

At a certian point the volume of gas overwhelms the size of the pipe it has to flow through and backs up know as backpressure. Anyone who tells you that backpressure is important doesn't know what they are talking about.

Michael Yount · Jun 11, 2005

90gt - do a google on exhaust scavenging - your terminology is either off, or you're mistaken. Scavenging occurs because of a pressure wave that bounces back up the primary - timed in a way that it hits the head and bounces back down the primary just when the next exhaust pulse is leaving the same port. That bounced pressure wave helps accelerate the flow of exhaust. The exhaust flow moves at an entirely different, and much slower, velocity than the pressure wave moves at.

For V8's, pressure wave scavenging is much more effective at assisting exhaust flow and (yes) even helping to fill the cylinder during overlap (when both intake and exhaust valves are open) when 1) long tubes are involved - the tuned length of the primary is around 24-36"; 2) an 8"-12" long collector of around 3" diameter is present - it's this expansion of volume (from the primary size to the collector size) that partially 'kills' the pressure wave, and bounces it back up the primary to aid the next pulse. The velocity of the exhaust flow is quite slow compared to the velocity of the pressure waves - which travel at the speed of sound.

dvs bullet · Jun 11, 2005

90mustangGT said:
Once again, backpressure is always bad. The fact is that larger exaust will cause more backpressure if the energy and volume of the air isn't sufficient to push the gas out of the car. I have a pnumatic (sp) (air powered) vaccume cleaner with no mechanical parts except a on/off valve. So how do you turn 90+psi into vaccume? Well it has six small ports that face towards the bag. When you squeeze the trigger the air is blown away from the nozel, causing a vaccume. Exaust works the same.

Why would stock headers work best in a stock motor for low end torque? Well even though they are kinked, these kinks act like venturie tubes in a carb to speed up the air, but not allow it to blow back in. Forming a chamber of vaccume behind the kinks so when the exaust opens up there is less volume of gas and actually sucks the exaust up and increases velosity.

smaller pipes create more pressure, more pressure equals higher velocity ( speed of gases) this speed coming from one tube on a header creates a venturi affect pulling remaining gases in other tubes out ( like a carberator ). What some people don't get is that ther is a certain point that you shouldn't go past to to keep up velocity. What I did was 1 5/8 shorties 2 1/2 h pipe and then went down to 2 1/4 tails, when you get past the muffler the gases cool and shrink loosing presure and velocity, you shrink down a size after the mufflers to keep the gases moving faster

dvs bullet · Jun 11, 2005

At a certian point the volume of gas overwhelms the size of the pipe it has to flow through and backs up know as backpressure. Anyone who tells you that backpressure is important doesn't know what they are talking about.

so run open headers or nothing at all

you need back pressure for torque period

tmoss · Jun 11, 2005

Sorry I don't have time to wiegh in here as I am on the raod moving my son from Portland Oregon back to St Louis. We are taking out time through the scenic routes of the rockies.

Selecting the right exhaust SYSTEM (not one piece) is not that simple deal. Most guys go too big too fast, but some combos can take advantage of the increased system cross section without loosing a lot. In general, a 1 1/2" works well on a 302 and 1 5/8" work well on a 347. I've seen it happen time after time over the years on dyno comparison tests. Some combos do show 1 5/8" being better on a 302 but they are less likely. Like anything thing else - it depnds on the combo you choose to use it with. Most people rely on the SOTP which IS pretty unreliable. Sorry I can't be more helpful, but in the end it's an educated guess.

Rick 91GT · Jun 12, 2005

I've seen similar results with headers and H/X pipes on stock motors, and was surprised how those kinked up messes Ford calls a header actually work..lol

With a ported stock head we have not seen any losses or major gains with a 1.5" shorty, to me they are a waste of money. Wait till you add more mods and swap to a 1.625" shorty or long tube.

Kevin How's the search for a new car coming?

Michael Yount · Jun 12, 2005

"Kevin How's the search for a new car coming?"

Yes - inquiring minds want to know if the next "sleeper" has arrived....

04sleeper · Jun 12, 2005

No, it has not arrived yet.

I have been looking around pricing some 03's and 04's. I have been kind of working on my garage right now trying to get it ready for the new car. Along with working on everything else in the new house. It's been just enough to keep up with right now and I have been traveling a lot with work so it doesn't help.
Here is what I have been working on.

Before:
View attachment 512314

After:
View attachment 512316
View attachment 512318
View attachment 512320

Future:
View attachment 512322

Michael Yount · Jun 12, 2005

willys1 · Jun 12, 2005

Lookin good Kevin ,,Hey Tom if you have time do yourself a favor and stop in Telluride for lunch,or over night if possible Thanks guys,I think Im gonna change my FMS unequal shorties for some equal lenth shorties,a catted X-pipe,and keep my Bassani cat back on..I have a T-Moss lower I was gonna use but I just ran across a cheap GT-40 intake,its real tempting

T-Moss or M.Yount,or exhaust guru's come in

willys1

Active Member

5spd GT

"the 5.0 owns all"

04sleeper

Michael Yount

Mustang Master

5spd GT

"the 5.0 owns all"

90mustangGT

I felt sorry for girls because

Michael Yount

Mustang Master

dvs bullet

New Member

dvs bullet

New Member

tmoss

Gettin Wired

Rick 91GT

Mustang Master

Michael Yount

Mustang Master

04sleeper

Michael Yount

Mustang Master

willys1

Active Member

Similar threads

T-Moss or M.Yount,or exhaust guru's come in

Active Member

"the 5.0 owns all"

Mustang Master

"the 5.0 owns all"

I felt sorry for girls because

Mustang Master

New Member

New Member

Gettin Wired

Mustang Master

Mustang Master

Mustang Master

Active Member

Similar threads

Privacy & Transparency

Privacy & Transparency