Cheap DIYS Stock Turbo Y Pipe Mod
 

Helps eliminate interference. Saves some wear and tear on you turbos and free's up a couple hp. Especialy in sequential mode. Great for Non-Sequential too for that matter. If you have a stock car this is a great mod that doesnt require a computer change or anything else for that matter to help the performance/longevity of your car. Great for Non-Sequential too for that matter... This mod recieved rave reviews in RX-7 Magazine over here in Japan. It will also work with the new style hard pipes.

(Note: I still think seq sucks as far as race tuning is concerned)

Just as in the picture... Take a hard pad grinder and cut a slit along the bottom and sides of the pipe big enough to fit a piece of sheet metal through. (high enough up the sides so you can get a weld on the sheet metal twards the top for rigidity) Cut the sheet metal to fit through the top opening. Once the sheet metal is up there then just cut the remaining off of the outside of the piping. Then weld it along the seam. Even if you cant weld or dont have a welder just do the mod then take it to a muffler shop or something to make the final weld, thats what I did, they shouldnt charge much at all just for a simple weld.

Sorry if its been posted before but I did not see it anywhere.

PICTURE #2
 

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Re: Cheap DIYS Stock Turbo Y Pipe Mod
 

Let's hear the reviews. What HP numbers were gained, and what's the primary function?

This sounds pretty cool, but yeah i'm curious as to exactly how this is supposed to help.

"Helps eliminate interference" -Jesse

It directs the air flow from the turbine to the engine as opposed to the other turbine... efficiency...

A small difference but a difference none the less.

I read in a book about turbo.
Actualy if they are running parallel (non-seq). You want them to come together, it will create turbullence which is good for directing the flow.
Maybe I am wrong, don't remember, but there was a drawing somewhere.

reza

Which RX7 mag? Sounds interesting... I have an extra stock y pipe.. might as well try it.

Could you find that book, and quote it to us? I would like to know the specifics of not doing this set up.

That makes perfect sense. Might help a little with lag.

Its in this book.
I have the book at home, but don't have working scanner.
http://www.amazon.com/exec/obidos/tg...oks/0895861356

Thanks for the link. Screw the scanner, just type the passage from the book. I have the chance to do this mod, but if it doesn't work well with non-sequential I wont do it. It makes good sense to me that it would help, but if the book says, no it's a bad idea to split the streams, then I dont know.

Im gonna break out the dremel and try this. Can you do a diagram of how far down you cut?

Also, what did you do to accomodate for the curvature-- Is it perfectly round, or oval? (diameter size would help)

It seems like a logical thing to do... I dont see how the plate would restrict that much flow since it is only split within the y-pipe. If the airflow from one turbo is going at a faster velocity than the other, it should 'pull' the lower velocity air causing a marginally faster spooling time. Should be a lot less turbulence within the coupler than if the air was to mix within the y-pipe, where the charged air comes in at colliding vectors.

What a great idea...this really does make a lot of sense, as the two directed flows from the two turbos are indeed facing each other, wasting energy in the form of additional heat being added to the air.

Okay, I got it on digital camera.

I think it may not actually apply for RX-7.
The theory is for V8 engine that has parallel turbos for each banks.
https://www.rx7club.com/forum/attach...postid=1047715

whole page

wholepage

i would imagine that splitting the turbo's compressed streams like that would make good sense, but wouldnt it also add a lot of restriction to the air flow of the turbos? im just curious because instead of splitting it up into two 3 inch pipes, it cuts it down to two 1.5 inch baby pipes, so wouldnt this kinda "constipate" the turbos, like if you were to try to take a shit through two small assholes instead of one normal one?

that might be true if it were two 1.5" pipes all the way to the intercooler

how do you figure that? he's splitting up one three inch pipe in half, so he's not losing any area. it's not equivalent to 1.5 inch pipes.

[QUOTE]like if you were to try to take a shit through two small assholes instead of one normal one?

Yeah, I prefer the one normal hole too.:tear:

Seems this would make more sense if you could find a metal strong enough to handle the blast furnace inside the common manifold out of the turbos. Since at moderate boost levels you get exhaust gas reversion(like in the V8 diagram above post) the turbines are fighting against each others pressure waves of exhaust gas. It seems that a strategically placed and welded piece of inconel or other stout material protruding from the down pipe and fitting snugly into the turbo manifold common outlet to shelter exhaust gas from each turbo would make a large difference at higher boost levels(ie 18 or so psi).
art

Well, if your read the fine print, they are concerned about even distribution of fuel mixture to each intake runner. Flow does not seem to be a concern. I would think that this modification would help smooth air out, and perhaps increase perfomance. I would like to see some dyno numbers to back it up.

The excerpt with the example from the turbo V8 doesnt apply, since its merely saying that turbulence is needed to better mix the air/fuel, which is an unrelated matter. I think there are really too many variables to say off the bat whether this would work or not. It depends on things like what kind of flow there is in the pipe (laminar or turbulent, I would think the latter), or whether the additional vortices created at the right angled corner from the metal barrier/pipe interface would offset the gains.

Unless you personally have a glass smooth intake track, I think we can throw out laminar flow and assume that turbulence wins.

Right on.

this mod sounds like the air tornado thing on tv. are there any fuild dynamic scholars in the house? time to apply what you learned. :) help us out here. does it really work? what's the physics behind the two small cross sections as compared to one large one again? what about flow characteristics in a semi circle as compared to a circle? etc, etc.

My point is on the exhaust side of the equation so the laminar/turbulent flow do not apply. My suggestion is merely to separate the exhaust turbines from one another. Since they force compressed gasses against one another, if you could eliminate this reversion at say 60K rpm and up the turbos WOULD produce more boost and much more efficiently since they wouldn't be working against one another.
Art

They'll be working against each other anyway.. You still have to pressurize the entire system before you can build boost. It would eliminate some turbulance down at the Y to maybe ease the transition, but once both turbos are spinning, I can't see how you're flowing any more air..

... which brings me to my idea for the non-seq guys. Why not just block off the primary turbo outlet? It's not pushing boost, all it's doing is providing an alternative path for the secondary air as it spools = more lag. Has anyone tried blocking it off or just putting in a pipe from the 2ndary outlet directly to the x-over pipe?

-pete

YGBSM!

Turbulent BLs would be better anyways because the flow would stay attached longer around sharp turns. Thats why golf balls are dimpled....

Been smoking again? I don't think I understand what you are saying. To me it sounds like you are saying to kill the primary turbo. One turbo only?

Been smoking? no. Do you have any idea at all how non-seq works?

Pay attention smartass:
Non-seq doesn't use the primary turbo at all , by locking in the turbo control rod and leaving the CCV wide open you've just told the primary to fuck off. Let's take this point by point:

1. The turbo control arm mod:
This directs most of the exhaust gas away from the primary. Notice the change in exhaust pitch with NS? That's the less backpressure of the secondary. Notice the missing sound of a primary spinning up with NS?

2. The CCV mod:
This makes the (very slowly) spinning primary try to pressurize an even slower spinning secondary compressor outlet stage. The end result is no boost until the secondary can reverse this flow. Even if the primary had full exhaust (which it DOESN'T) it still couldn't boost because it would just try harder to backspin the secondary.

3. Pre-control mod: (optional I know) This directs yet more exhaust away from the primary turbine see (1).

IDIOTS VERSION: Non sequential is just secondary mode for the turbos. You are not getting any useful flow out of the primary turbo. That's why you get stuff all power below 4500 in 1st 4000 in 2nd and 3750 in 3rd.

I'm happy to draw you a picture if you like.

Now as to what I was saying - When the turbos are in secondary mode, the only thing stopping the secondary compressor from forcing air into the primary is the fact that the primary can still have +ve flow until redline. It cannot flow as much as the secondary and as a result causes the secondary to bleed off pressure - losing you power. If you bypassed the primary altogether - I cant see why you shouldnt get the performance of a reasonably sized single.


-pete

Uhh.. what?

Let me get this straight.. You're trying to say that the secondary turbo makes all the power after the transition? You do understand that it's sized exactly the same as the primary turbo, don't you? It's no bigger at all. So why would just spinning the secondary take longer to spool than just spinning the primary, genius? Why would spinning just the secondary make more power than the primary? Hmmm... Haven't thought this out, have you?

NON-seq runs the turbos together. THAT's why you don't hear just the primary spooling. Because they're BOTH spooling. But please, draw us a picture. I'm curious to see exactly how your car runs.. do you even have an FD?

Turbine sizes:
-------------------------------------
Primary 51mm (50mm for 99+)
Secondary 57mm

LOL I can just see you fuming away there. That makes it all worth it :)

-pete

LOL!

Hmmm, where did you happen to run across that info???

If your talking about US 93-95 FD twins your info is wrong. The 2 cartridges are completely identicle

You sure a bloken apex seal didnt go thru your pri and chew about 6mm off it lol

STEPHEN

Pete, don't get all defensive or anything, butyou have got that all wrong. When you go nonsequential you are simply taking out (or opening up) the doors that allow the turbos to spool independently. The stock sequential system at 4,500+ rpm, and a nonsequential system at any rpm are simply dividing the exhaust gases (relatively) equally to both turbos. The reason it takes so long to spool the turbos with nonsequentil is because you have twice the mass to rotate (i.e. two turbos instead of one). There is no need for all the hostility. P.S. the turbos are the same size.

I guess he was smoking. Don't worry; I felt the same way when I learned that you don't use an apostrophe "s" after "it" to convey possession. I also felt stupid, but I got over it.

:rofl::rofl::rofl:

That was fantastic...

Wow ... I was really worried about my understanding of the FD for a minute.

Pete,

Definitions:

Sequential - One at a time, Take your turn children!
Non-Sequential - Both at the same time, every man for himself!

During sequential mode, the low volume of exhaust at lower RPM's is enough to boost one small turbo efficiently but not one large or two small ones at the same time. Since the primary turbo is small, at larger volumes of exhaust flow at higher RPM's, it becomes inefficient and high back pressure on the exhaust would result. Now comes the little flapper doohickey bypass. It allows some of the exhaust pressure to pre-spin the second turbo and allow it to reach close to operating speeds and temperatures faster. Now open up the full flow to the second turbo, your boost drops. This is because your exhaust volume is the same at this point, but now your flow goes through twice the volume as before because the second turbo flap is opened and taking about 1/2 the flow and energy from the exhaust stream. Boost increases again as the RPM's increase and the exhaust volume increases until the wastegate says: "Whoa dude, too much boost, dumpin' excess now!"

Non sequential allows all of the exhaust gas to flow through both turbos at the same time. Thus you have turbo lag (low RPM's not enough volume to spin both turbos efficiently) and late power band boost.

Remember, the reason that Mazda went with two turbos to begin with was to nearly reduce or eliminate turbo lag. This is what they advertised. Otherwise, they would just go with a big single and have a more dependable car.

Now today's technology is allowing better and more efficient turbo boost patterns and giving the RX7 different options for single turbo upgrades.

Tim

Um, no offense, but....was there a reason for resurrecting this thread by replying to a post nearly a year old?

Kento,

It's not a late reply, he just types slow.

Why does it matter how old the post is?

Yes,

I did a search, found this, felt I had something to contribute, answered and never checked the thread date.

MODERATORS should lock all threads that have had no posts in 30 days. If someone want's to open it back up, they would need to repost with a reference to the original. I have thought this all along, but never voiced my opinion about it.

Besides that, I was going to write a 5 page dissertation about laminar versus fluid flow since most people have it wrong, but I will let that up to another aerospace engineer to correct.

Tim

Tim

Tim, Very nice definitions and discussion as to how the turbos operate. For us non-engineers we would love to hear the "laminar vs. fluid" dissertation when time permits.

Paul

I like this mod - it just makes Ghetto sense!

I'm going to use a band saw to cut the entire pipe in equal halves and then tack weld in a divider to COMPLETELY separate the sides, then weld the pieces back together. I plan on using a piece of metal for the divider roughly the same width as the band saw blade in order to maintain the overall dimensions.

Hell, while there, might as well smooth the interior of the pipe - can't hurt!

Before I start welding, does anyone have a guess as to what type of metal the y-pipe is cast from?

I GOT IT!!!!

GET THE TORNADO!!!

Sorry for shouting guys, I was excited.