Anyone figured out yet why some headers apparently get rid of the 'torque dip'?

[markitect]

Originally Posted by Speedygonzales

Changing the length of primary pipes generally affects the amount of torque produced above and below peak-torque rpm. For example, all else being equal, shortening primary pipes transfers torque from below to above the peak, not significantly shifting the rpm point at which peak torque occurs. Increasing primary-pipe length produces the opposite effect of shortening the length.

Based on this it seems like a UEL header should give you good(not the best) results through the entire rpm band, are there any disadvantages to UEL design?

Also with UEL design, is there a specific way that the firing order is matched to the pipe length?

[rx3]

Xdragonxb0i and Hawaiian thank you for your responses.

I guess the headers just increase exhaust gas velocity, which is subsequently muffled accordingly (less apparently). (And this is responsible for more noise).

Btw, is there also a sort of 'stealth' ceramic coating available, which would make the catted-header appear more stock? (Maybe grayish instead of shiny silver or black.)

[rx3]

Originally Posted by markitect

are there any disadvantages to UEL design?

My guess would be, that each cylinder-bank could scavenge differently due to the UEL design (different fill factors in each bank), which then would lead to different AFRs in each bank. (This is just a guess though).

[Tainen]

Originally Posted by rx3

My guess would be, that each cylinder-bank could scavenge differently due to the UEL design (different fill factors in each bank), which then would lead to different AFRs in each bank. (This is just a guess though).

I don't really see any advantage at all of a UEL system. People have this idea in their head that the UEL design is what causes the rumble, but... that's just not true. :P

Also, @Jason@Nameless has some awesome 3d model mockups of variable intake runner designs. I swear he dreams of that stuff in his sleep.

[Hawaiian]

Originally Posted by rx3

Xdragonxb0i and Hawaiian thank you for your responses.

Btw, is there also a sort of 'stealth' ceramic coating available, which would make the catted-header appear more stock? (Maybe grayish instead of shiny silver or black.)

Glad to help. I don't know for sure, but I'll call and find out.

[P&L Motorsports]

Originally Posted by rx3

Btw, is there also a sort of 'stealth' ceramic coating available, which would make the catted-header appear more stock? (Maybe grayish instead of shiny silver or black.)

Updated: The only two colors the header comes in is Black/Silver.

Dylan@P&L

[SubieNate]

Originally Posted by Tainen

I don't really see any advantage at all of a UEL system. People have this idea in their head that the UEL design is what causes the rumble, but... that's just not true. :P

Also, @Jason@Nameless has some awesome 3d model mockups of variable intake runner designs. I swear he dreams of that stuff in his sleep.

No, it is absolutely true. The rumble is caused by the exhaust pulses running into each other as they enter the collector. Depending on the application there may or may not be a serious performance detriment. But the sound is undeniably caused by the header design.

Can a car still have a nice deep tone that's "rumbly" with an EL? Yes. There are things you can do with the rest of the exhaust to make it deeper. But that signature "boxer rumble" that Subaru is known for is 95% because of the UEL headers. Just listen to any EJ engine that's had an EL twinscroll manifold put on it, or even a Honda with an UEL header. In each case the effect of the header design is very clear.

Cheers
Nathan

[Tainen]

Originally Posted by SubieNate

No, it is absolutely true. The rumble is caused by the exhaust pulses running into each other as they enter the collector. Depending on the application there may or may not be a serious performance detriment. But the sound is undeniably caused by the header design.

Can a car still have a nice deep tone that's "rumbly" with an EL? Yes. There are things you can do with the rest of the exhaust to make it deeper. But that signature "boxer rumble" that Subaru is known for is 95% because of the UEL headers. Just listen to any EJ engine that's had an EL twinscroll manifold put on it, or even a Honda with an UEL header. In each case the effect of the header design is very clear.

Cheers
Nathan

ok. that's not what I've heard from Quirt Crawford. :P

(not trying to be an ass.)

[naikaidriver]

Originally Posted by Tainen

ok. that's not what I've heard from Quirt Crawford. :P

(not trying to be an ass.)

Just an FYI, like Nate, I am also an engineer but Nate makes me look like an idiot child by comparison.

Just my opinion, but I would listen to him. :happy0180:

Scott

[Tainen]

Originally Posted by naikaidriver

Just an FYI, like Nate, I am also an engineer but Nate makes me look like an idiot child by comparison.

Just my opinion, but I would listen to him. :happy0180:

Scott

OK. I am not, and only know what I am told by other engineers, which is why I am definitely not trying to argue with anyone here.

[industrial]

Originally Posted by Tainen

I don't really see any advantage at all of a UEL system. People have this idea in their head that the UEL design is what causes the rumble, but... that's just not true. :P

Also, @Jason@Nameless has some awesome 3d model mockups of variable intake runner designs. I swear he dreams of that stuff in his sleep.

The problem with nameless is for all the buzz, all they have produced is a front pipe and muffler. I understand they are a small operation an probably want to release the headers when their rudimentary exhaust work slows down. But it still stands that at the end of the day, they produce a few exhaust bits that really don't matter who you buy from. And you have to wait a month for.

And the rumble does come from uel. Any sti guy that went to an el setup will tell you that.

[naikaidriver]

Originally Posted by Tainen

OK. I am not, and only know what I am told by other engineers, which is why I am definitely not trying to argue with anyone here.

I'm sorry if it seemed like I was implying your were. I know you weren't. :happy0180:

I was just joining the conversation.

Scott

[SubieNate]

Originally Posted by Tainen

ok. that's not what I've heard from Quirt Crawford. :P

(not trying to be an ass.)

I wasn't either. My post may have been a bit strongly worded.

If Quirt has some explanation other than the headers as to why it completely goes away with every EL setup I've ever seen I'm all ears but the explanations I've heard line up 100% with the empirical data I've seen.

@naikaidriver-*Blush*

Cheers
Nathan