Tubi exhaust bypass valve - few q's?

Well , I can give you my experience. I bypassed the soleniod switch that tells the stock bypass valve to open. So it was basically vacuumed open all the time. It sounded great and I knew that it was open ! (I was worried that my soleniod was not working). But my CEL did come on with code P1448.

Some on this forum have not had the same fate. Some have wired the valve open and didn't get the CEL.

 

I'll pass along my experiance with my 355. The OBDI has slightly different exhaust than the 0BDII cars but, the exhaust flow looks to be the same. The 355s have what I would discribe as an upper and lower exhaust. The upper one actually flows better than the lower but, the bypass valve stops the flow of exhaust and forces it thru the lower side which is where the main cats are and than at 3500 rpm the bypass is opened and the exhaust takes the easier route which is thru the upper side. Why the CELs come on sometimes is that the O2 sensors are not getting a correct reading at low RPM with the bypass opened/removed at lower than 3500 rpm. My exhaust is the challenge system which has no bypass and no upper cats, at low rpms the exhaust flow is thru the upper exhaust and actually pulls outside air in reverse thru the lower exhaust and past the O2 sensors the wrong way which of course causes the CELs to come on. I think there is a power increase when the valve is removed because with in place it resticts the flow from taking the least retrictive path at lower rpms. I don't know how much but, I wouldn't think it would be that significant. The noice would be better for sure. Hope that helps, Regards, Vern

 

I have asked myself that question too. I thought it might have to do with compensating for more exhaust flow since the redlne is higher than the 348 ie; needing more capacity for the increased flow at 8500 rpm but, the 360 has a single pipe per side. Maybe just for noise effect at higher rpms the 355 does sound better than the 360. Regards, Vern

 

If there was any power increase...it certainly was not discernable due to the overwhelming exhaust note.

 

We eliminated the uppper level of the exhaust with custom headers, cats, and exhaust on 335bnuts car. It really is such a silly design, the header flow is killed by that rough 1-2 split at the end.

 

I don't know if this is the right place to post this but....Does any one have an exhaust by-pass valve they no longer need?? Mine has failed miserably. The vacuum actuator diaphram is torn and does not respond to vacuum. Hence no workie.

I am interested in the vacuum actuator only or the entire by-pass assembly. For a F355. Will pay reasonable cash pronto!! Thank you!

 

Was there any HP gains with your design?? How about some pics??

 

System is complete. Headers being ceramic coated and exhaust polished. I should have it back together this weekend for pictures and some after dyno runs. Teaser shot of the headers made from 321ss, 321 has a white finish. The tubi caps wont work correctly. If you only cap off 1 of 2 exit points the exhaust gases will still flow to the exit but have no place to go. This will create turbulence inside of the header and slow down exhaust flow as it tries to find its way out of the header. With exhaust design its all about keeping a nice smooth flow.
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Can anyone describe what an "open" and "closed" bypass valve actually
looks like in its different modes?

I am trying to determine is mine is working or not as well. Currently
it seems to stay closed all the time. I am determining this by the
fact when the car is off, the shaft is all the way out of the
round thingy, I assume this is closed. I have NEVER seen it with
the shaft all the way inside the round thingy (Im assuming this is open).
I can move the shaft by hand into the round thing.

My exhaust has some sort of weird connection, and I am unable to
determine if it is vacume/hot wired open or closed (I have another thread
on this with a diagram).

Is it open when the shaft is all the way out the round thing or closed?

 

brendon0, The default position is closed, shaft all the way out the round thingy. You can hook up up some spare vacuum line to it and manually (mouth) put vacuum to it. You should be able to see it pull the shaft into the vacuum actuator (round thingy).

 

Nice pic! So this system will eliminate the bypass valve? Can you sell me the the bypass valve no longer used ?

On the new header/exhaust system, what size are the primaries and collector? I am assuming one has to change the cats and muffler too?

 

1 5/8 stepping into a 1 3/4, 4-1 merge collector going into 2 1/8. Any cats can be used, its built to work with factory cat mounting location. Exhaust must be changed as the upper part is fully removed and the exhaust wont function the same.

 

Why dont you just leave the vacume valve attached to the top
and it'll stay closed... Couldnt hurt since it functions that way
now until a certain RPM..

 

The way the exhaust is designed from start to finish has many flaws. The correct way to fix everything is to build a complete new system. If you just leave the valve closed the flow inside of the muffler is still not correct. The chambers are designed to be filled in the high rpm, without that 3rd source feeding exhaust gases the whole system does not function as its designed. I will be doing a complete write up on the factory layout vs ours with videos, pictures, and dyno graphs to explain everything in detail.

 

Ferrari realized that their exploration with the 3rd source had no advantage and thus reverted to the current setup as with the 360 and 430. What Dan is doing converts the 355 to a 360 exhaust setup.

 

Sounds like a great plan! I am interested in it, though do I just plug the third inlet of my exiting muffler??

 

If you opt for this setup you are going to lose your muffler and replace it with an X pipe. You should call Dan.

 

We make a new x pipe muffler from 321ss or inconel 625. The 321ss system weight 8 pounds in total. You cant just plugs the factory muffler as I explained. The muffler chambers are designed to work with that 3 source, without that it doesnt flow and operate the correct way.

 

So no by-pass valve at all with the new system??

 

That is correct, picture a 360 or 430 exhaust system layout.

 

That sounds great!! So I can use my existing hyperflows with this system?? Will the hypers flow enough to be the only exhaust path?

 

The system im building is integrated with the customers hyper flow cats, so yes. And yes its enough to be the only exhaust path.