Has anyone ever thought about welding a metal plate down in the middle of the y-pipe where the two converge into one?? I saw a picture of something like that while browsing some Japanese sites. Has anyone tried this on a US y-pipe? Would there be much of a gain? I would think since both pipes are kind of angled at each other that it might clear up some turbulence down in there and keep things moving in the right direction. What do you guys think?

 

I've seen that on this site a few times. Seems like a pretty good idea.

 

i think KinitekFD (i think thats his username) made one and it was a beautiful piece

 

he was actually selling it not long ago
I've been thinking of making one also

here's a thread with all the info
https://www.rx7club.com/showthread.php?t=637865

 

I've spent alot of time at the flow bench testing mods on the Y pipe. I know it defies common sense, but the stock piece is not too bad. (Including the cross-over tube.) It can be improved, but not with the divider that has been shown-- that actually hurts flow. The BOV port needs to be moved and the runners need to be reworked, in order to get maximum effect. I have also experimented with an airfoil mounted inside, a budget approach to approximating a rework, with encouraging results. This kind of mod takes a lot of time and testing to get right. Improvements in flow of 5 to 10% on the individual runners can be achieved and even more can be realized in combined output.

No, I am not going to post pics for everyone to try to do themselves. The tolerances are too critical to try and get to come out right by duplicating a photo. I might consider doing some of these for interested members, but it will not be inexpensive unless I get enough for a production run.

 

I think its a waste of time. There are other restrictions in the twin turbo system. An efini y pipe is more than enough.

 

I recall seeing some comparison dyno sheets from Japan and this mod increased output slightly in the mid-range.

Jack

 

I have removed the bov from the y pipe and reshaped it . The ones I have done it for said it made a differance they could feel .

 

I'd like to remove the bov from the Y, i already have a separate one and don't need it there. I'm probably going to go for an efini Y though.

Has anyone modded the efini y?

 

Wow. Do you polish the inside passages of the y-pipe?

I think for a DIYer with too much time on their hands, that polishing the inside surfaces might be more reasonable.

Dave

 

Actually, polishing the inner surface would cause more turbulence. You only want a really smooth surface if the passage is practically arrow-straight. The boundary layer airflow will cling to a slightly rough surface better (and prevent turbulence) if there are any curves in the passage...of which there are plenty in the FD's complete intake tract.

Basically, it's the same principle that is the reason for golf ***** having dimples.

 

If you think that is cool, you should ask him about the results he observed from testing the turbo manifold. His ported manifold is awesome.

 

I know this has been covered before, I but I couldn't recall offhand if turbulence was desired (as is the case in golf *****) at this point in the intake, or polishing to delay the onset of a turbulent boundary layer was more desirable.

Dave

 

I have modified the Efini Y pipe as well, removed the bov pipe and reshaped the area .

 

Anytime you have a curvature in the surface features, it's more advantageous to have a turbulent boundary layer. Even just a slight curvature will cause the breakup of a laminar boundary layer.

 

LOL, I just scared myself.....I think I actually understood what you just said.

 

Ah, yes, it's all coming back to me now.

I should have dug up the old thread prior to posing the question again.

Dave

 

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/polished-intake-manifolds-very-bad-554531/

 

Please elaborate, or give us a link if you could. Or if Speed of Light could chime in, I'm very interested in the topic.

 

+1 I was going to just PM him but I bet a lot of us are interested in the subject.

 

Interesting,,,shed some light

 

my thoughts exactly