Tri Y design according to firing order

[elliotaw]

Below is a quick number chart showing the firing order according to cylinder number. The Main number indicates the cylinder number and the number in brackets is the firing order.

8(2) 7(7)

6(5) 5(6)

4(3) 3(4)

2(8) 1(1)


I am trying to work out the best design for a tri y header. I am learning here as I go but I assume that you would want to group the primaries as per firing order so that they dont fire close to each other.

Ok, so on the right hand side you wouldnt want cylinders 5 and 7 to have the primaries grouped together as they fire one after the other so the best solution I can work out would be cylinders 1 and 5 together and 3 and 7 together.
Now when we look at the left hand side, you cannot do a mirror of the right hand side as cylinders 4 and 8 fire next to each other. The best solution for the left side is to have cylinders 2 and 4 together and 6 and 8.

My question is this.... this would mean having headers which look visually different to each other. Would doing this somehow unbalance the engine and cause problems? I've done a few searches on the net and found some header manufactures who do exactly this and have differeing setups for each side...I can only assume to get the firing order separated nicely.....

Anyone have any input on this ?

Elliot

 

[elliotaw]

Heres an example I found on the net of headers with different set up primaries on each side....

http://www.stans-headers.com/Photos/246Y.jpg

Elliot

 

[Ursus]

it should be fine as long as the hedders are equal length even if they aren't totally equal the engine should be fine. If you're worried about the weight throwing something off it won't. By the firing order you've shown it looks like an x pipe wouldn't be effective 1/2 the time making either a true dual or maybe an h pipe better for performance. But the design you're proposing would stilll maintain the scavenging affect within the hedder itself. especially with your 4:2:1 design

 

[JBrady]

While it seems to make the most sense to pair cylinders as you suggest... IE; "non-interfering"... there is actually a situation where pairing "interfering" ports is a good thing.

Due to space and design restrictions it was decided to pair the 5 and 7 ports on the S&S headers. When I got a set I tried an expirement: I placed a small piece of paper over the #5 port and blew air into the #5 port. The paper was sucked into the #5 port. This is due to the merge style collector used on this pairing. When designed properly you can actually use the pairing of interfering ports to increase power.

What is your application?

 

[Lambo]

tri y headers

guys here is something that will help, i saved it sometime ago, info since appears to have gone from their site.It covers cylinder pairing and 180 deg headers if you want the v12 type sound.

Regards
Lambo

 

[Lambo]

Can,t figure how to link to it i posted it on 11-3-2006 as a pdf so if you search my post on that day you should be able to read the pdf.

 

[elliotaw]

Those 180 degree headers look the biz... no way I have the room on my own project but made for interesting reading, thanks.

Jbrady, my car will be mostly street use with the occasional track day and drag run..

I'm very limited for room as the engine is in a relatively small car (ford capri) so any kind of tri y is going to be tight.

Elliot

 

[cyberdiamond]

Heres an example I found on the net of headers with different set up primaries on each side....

http://www.stans-headers.com/Photos/246Y.jpg

Elliot

Yes that is how they should be paired (same as a small block chev from memory)