MalcolmV8

Hey guys,

I made my own downpipe and now I'm modding it so I can have a recirculating dump tube. Here's the initial downpipe I built.



Here's how I've modded it to accept the dump tube.



Now I was going to use that piece of flex pipe in the dump tube. It just seemed like a good idea because of heat expansion in the exhaust in case I needed some give in there. However it's such a tight fit and PITA to get that piece of flex in there I'm wondering if I can just leave it out? Am I looking at cracking a pipe that way? Should I continue as originally planned and keep it?

Thanks guys
Malcolm

TheShodan

iTrader: (14)

your flex pipe from the downpipe will absorb any movement from the engine and heat expansion. Since the dumptube is secured with the manifold and downpipe, it will move together with the downpipe. There's no need for a flex section on your dumptube.

BigMike0147

If it's a PITA to put it in there, then don't worry about it like Shodan said.

I put some "flex pipe" into my recirc dump because it makes install a lot easier and if there is any difference in expansion, it will take care of it for me and hopefully not crack the weld at the dump/downpipe joint.

tron_

I vote to not even recirculate the dump

Natural Aspirations

If your concerned about movement use a slip-fit (I don't know the proper term where one pipe slips over the other) joint to allow movement. If your concerned you could even use springs to keep it tight like on the old Toda headers.

scottdh20

im with tron....dont recirculate.....or atleast you need to mellow out the transition in that joint....thats gonna cause alot of turbulance in the exhaust....you will lose power with that set-up as well as having a more restrictive exhaust

kbouchard1092

It seems to go in at a decent angle but further downstream would have been better for powerloss vs. non recirculated,. in comparison i have mine streamed into the downpipe right before the flex on the downpipe ( i have minimal powerloss nothing 1psi would make up for.) If done incorrectly you can loose a more significant amount of power. I would definatly add the flex pipe on the dumptube its a no brainer. I actually orginally used the flex you show in the pictures and ended up having it slightly colapse internally causing me creep issues thats were hard to diagnose. I would go with the Vibrant Turbo flex, these are designed for high heat associated with turbo. I havent had any issues since i swapped it out. IF you dont use one it will crack overtime, the downpipe will flex but the dumptube is not since its welded to the downpipe.

its all preference but i wanted the quietest exhaust possible while keeping as much performance as possible, and less chances of fumes in the car....i made 411 @20psi without no2 on a t3/t4oe.... now would i make 420 without it? maybe but its not worth it too me ill take the quieter set-up.

Also like Mike says above its makes it much easier to take in a put out. However Heat expansion should be the #1 reason to install one

kbouchard1092

WE have different downpipes but for refernece this is what mine looked like orignally. It now has the vibrant turbo flex tho. (I had the flex you use and the one in my picture changed twice before i went to the turbo flex...just fyi)

MalcolmV8

Thanks for all the feed back guys. My thought on the flex joint in there was not for movement but for heat expansion and the welds possibly cracking where the dump tube welds into the downpipe.

Humm so you guys think I chose a bad spot? I should cut that off and weld a patch in there instead? I should instead make the dump tube go much lower down towards the end of the downpipe and then feed in there instead?

Where's a good source for the Vibrant TurboFlex couplers I need to use instead of what I have?

kbouchard1092

i called it turboflex but This is what you want.... http://vibrantperformance.com/catalo...oducts_id=1638
-Thats if youre using a 38mm gate and 1.5" piping....if you have the 44mm you need the 1.75"

Benefits of using this:
- Ideal for use on Wastegate Dump Pipes
- Features a directional, smooth flow solid liner
- Designed to reduce premature cracking of manifolds and downpipes



I mean the angle doesn't look horrible. but rule of thumb is 18" of piping at min. then at that point you can merge in. YOu want to have minimal angle as well.... I think its not horrible(the angle) i have seen alot worse then you have, but i think going longer would have its benefits

I would make it longer and try and do less angle then what you have...if it was me

MalcolmV8

I really like that piece you posted a link to. It's super small and compact. That'll work great for what I want. I tried to buy it but it only has a "wish list" button and says you need to get it through a distributor. Unfortunately I'm at work and won't be able to search for it till tonight.

When I get home from work tonight I'll cut off my side piece joining I had made and patch that hole. Then I'll try and add it way down lower and try and reduced the angle it's coming in at.

Thanks for all the direction. It has been most helpful.

kbouchard1092

here you go....http://thmotorsports.com/vibrant/vib.../i-296898.aspx

again this is for use with 38mm wastegate and 1.5" piping.

The way youre downpie is it might be better to wrap the pipe and merge onto the other side into the bend right before the downpipe flex...Def want as small of angle as you can get...YOu can see mine in the picture its probably around 20 deress.

Bix VT

these threads may shed some light on the issue:

https://honda-tech.com/forums/forced-induction-16/how-much-performance-lost-routing-wastegate-pipe-into-exhaust-94820/

https://honda-tech.com/forums/forced-induction-16/downpipe-size-vs-open-closed-loop-question-151845/

From what I understand, there will always be a loss of power when routing the WG into the exhaust stream, but the loss can be minimized by introducing the WG gasses a decent distance from the turbo, and at the smallest angle possible. However, I consider the losses worth it in my case, as I'm much more concerned with quiet operation than an extra 10whp.

MalcolmV8

Thanks. Reconstruction coming up tonight. It's gonna hurt to cut off all that work I did last night but it must be done correctly.

MalcolmV8

OK I cut off my dump tube setup off the down pipe tonight.



Here's my patched down pipe. Gosh that hurt to see after taking so much pride in building my first down pipe lol



OK here's the new design I'm going with. This is just tacked on here for mock up. The idea is it will enter the down pipe much lower down and hopefully the angle is good too. It sort of goes with were the down pipe bends.



Another shot of the layout



Another



So what you guys think? heading in the right direction? Also I ordered that vibrant turbo flex piece you guys showed me up above.

Thanks
Malcolm

TheShodan

iTrader: (14)

Remove the 90 degree portion completely when going into the downpipe like that. Make an angle cut to make an even smoother transition.

scottdh20

what he said^^^

install it almost like a collecter for a turbo manifold for optimal performance....what you have there is 100x better than it was before though

MalcolmV8

Thought I'd update what I ended up doing for you guys that helped me.







After clean up I put on a coat of black high temp paint to hopefully slow down rust. Not sure if the paint will stay on but worth a shot. Next I'm going to wrap the downpipe and dumptube with some exhaust header wrap and then install on car finally.

Bix VT

Good call on the O2 sensor position. Threads like this make me want to learn how to weld

tron_

Looks much better than before man

MalcolmV8

Yeah man once you can weld it lets you be creative and come up with your own stuff. I'd never tig welded in my life prior to the honda project. Took some practice and there was a learning curve but I got it

Thanks.

kbouchard1092

Looks much better for sure!. I doubt the paint will stay but it doesnt look too bad.

Most likely it will chip off. Usually only professionally coated products really stay (for the most Part) Or ceramic coatings

I am glad i told you about the Turbo flex bellow there..I re-did my dumptube 3 times now cause the flex kept failing (even the turbo flex) This one is made really specifically for dumptubes. Anyone looking to recircualte there Dumptube NEEDS to use this type of Flex. I had one fall apart, and the other one failed internally. The outside looked fine but it had collapsed somewhat internally and let me tell you was quite the PIA to diagnose since it looked perfectly fine from the outside.

kbouchard1092

Nice job tho for a DIY. Good job!

BigMike0147

Good job! a lot of welding on that piece with the flanges and what not. That's OK though because it will help a lot with install and breakdown.

spectacle

Looks good!