Have you tried "venting" yur WG dischaarge to atmosphere instead of back into the DP ?

 

Before you put in the external gate, did you have a mid range spike folowed by a drop off ?

Turbo started out as 60-1 Hi Fi w/ unclipped "O" trim wheel and large ported stock '89 WG passages.

Boost crept over 20psi (Pop-off valve was set to 20psi) before 3,500rpm at which point I took immediately removed the turbo!

Then it was "O" trim clipped 15 degrees w/ the turbo exhaust to WG exhaust divider shown in the above pics, but using even more ported stock (NACA ducts before WG holes in turbo runners) WG passages open air vented out a 2 1/4" hole in the turbo backplate.

Boost creep over 20psi by ~5,000rpm..

Then I did the external WG and enlarged the rear scroll's apperture to 10mm (as the front had been enlarged to 10mm in boring for "O" trim wheel). This was to relieve the higher pressure at the turbine exit and make the angle of the slot much less forward facing.

It seems everything I have done to alleviate boost creep has also improved total system flow as well and so I still incurr boost creep.


What type of exhaust do you run ?

JIC magic Spec 90 (3 1/2" turbo back w/ only 1 straight through muffler). Now, if I run the tip silencer it can't even manage the full 1.2 bar boost.

If I ever get boost creep under control I would like to try out the HKS 4" turbo back exhaust system




Have you tried "venting" yur WG dischaarge to atmosphere instead of back into the DP ?

Of course it is open air vented to the atmosphere!

 

Ok, what I feel you have done is (like you said) increased system mass flow so that your turbine section does not become your restrictor.

It would require X amount of HP to drive your compressor section and the rest your efficiently bypassing out the WG without it seems any detriment to your engine.

Would be very interesting to measure your exhaust manifold pressure while you are at WOT & high revs reaching 20psi intake pressure, It would be VERY HIGH !

The WG's mounted into turbine housing here come of in a "Y" section of the housing so allot more engery and flow is diverted to the WG, yours looks very much like a "T" intersection which is not ideal. either way its allot of effort you have gone to to eleviate the problems your facing. A more restrictive DP and exhaust will get rid of almost all of your problems. 3" is much more suitable for the power level you are going to make with that turbo. Even 2.5" will be more than enough ! Then maybe some folw will divert through the WG system and allow you to control the boost level

 

As you have experienced and what you have most probably realised is that you need to favour some flow to the WG side, the paths that are available very much still strongly swing to the turbine section, the best way you can "redirect some of this is by putting on a more restrictive exhaust DP combo, otherwise I see no solution to your problem, other than adapting a more favourable flow path to the WG "Y" intersection to WG of the housing.

I can tell you from personal experience that it is VERY hard to control boost on a hybrid turbo running a very free flowing post turbine exhaust system like you have.

 

Would be very interesting to measure your exhaust manifold pressure while you are at WOT & high revs reaching 20psi intake pressure, It would be VERY HIGH !

Probably very high, although w/ the low restriction post turbo exhaust I am hoping it is just a very high PRESSURE DIFFERENTIAL. It is hard for me to imagine the manifol pressure being so high w/ that 60mm wastegate open.

 

The more mass flow you "bleed off" through the WG the more pressure you need to deliver the required energy to the Turbine.

Say if you need 100bhp worth of power to to drive the compressor and this is at X flow at 20psi manifold pressure. Then if you "waste half of this flow out the WG" you will only have X/2 going to power the compressor (which still needs 100bhp worth of power) you need to increase the manifold pressure to over 40psi to deliver the same amount of energy to the turbine ! Actually it wil be a bit higher cause a fair bit of heat is being lost at the same time to as well as flow/pressure.

This is why its a non ideal situation to run the Biggest WG you can find, unless your engine can handle running at high exhaust to intake manifold pressure ratio's....... Rotaries in general respond far better to a bigger sized turbine and minimal WG bleed off, which ALL results in far lower exhaust manifold pressures.

Bleeding of energy through the WG INCREASES exhaust manifold pressure, it does not reduce it . Some people see a power increase though still because overall mass flow is increased, just got to be carefull that pre turbine pressure does not go to high.

In your case this maybe is still not an issue casue it is still favouring going through the turbine becasue of your very free flowing exhaust & "T" interersected WG

 

Didn't mean to have 2 posts, sorry

The WG's mounted into turbine housing here come of in a "Y" section of the housing so allot more engery and flow is diverted to the WG, yours looks very much like a "T" intersection which is not ideal.

Yes, I can definitely see the advantage of a less restrictive route to the WG by welding it on right where the scroll begins to curve.

I attempted to "Y" the juntion of the WG holes, but was limited by the casting thickness. By about the 3rd time I had had the turbo off for boost creep I said F*&%$ it I am going to try to maximize flow throught the WG to the detriment of the turbo flow and made large undercuts before the WG hole, but left the rear of the WG hole alone.

A more restrictive DP and exhaust will get rid of almost all of your problems. 3" is much more suitable for the power level you are going to make with that turbo. Even 2.5" will be more than enough ! Then maybe some folw will divert through the WG system and allow you to control the boost level

I found that putting the exhaust resriction at the very end of the exhaust system stopped the boost creep and still provided fairly good turbo response. It would seem to me the smaller downpipe (or any restriction closer to the turbo) will affect the turbo response more.

Anyways, I return this thread to its previous owner

I will post in single turbo section when I get that "P" trim wheel in there and whether it alleviates the boost creep.

 

The more mass flow you "bleed off" through the WG the more pressure you need to deliver the required energy to the Turbine.

Ah, I see that now with your explanation of it above

So w/ the high overlap rotaries have I am leaving a lot of hot exhaust in the intake charge due to the extreme exhaust pressures.

In your case this maybe is still not an issue casue it is still favouring going through the turbine becasue of your very free flowing exhaust & "T" interersected WG

I hope so, but how would you recommend monitoring the exhaust manifold pressure? Could I put a metal line off the turbo to a pressure sensor where the old wastegate flapper was (where stainless allen head bolt is in pics)? Or would EGTs give me a good enough picture of the exhaust pressures?

So much for returning this thread to topic

 

Yeah, you can tap into either the manifold or the base of the exhaust housing (before it starts to reduce in area). Run some metal tube (you can coil it up) and then run some silicone tube to a Industrial pressure gauge. I use a 0-100psi large face unit for this testing.

Only way to do it is to measure what you have pre turbine, give it a go and tell us the results.... A the moment my gut feeling is that it wont be too bad at all. But once you start to get that BIG WG to bleed of some flow and control boost you will see the exhaust manifold pressure starting to rise.

Restrictive post turbine exhaust systems increase manifold pressure heaps, as do large percentages of WG bypass for the reasons outlined before. You need to find out what works for you and your engine. But yes rotors do respond greatly to having an "ideal" match of EX pressure to IN pressure, specially if PORTED !

 

Thank you RICE RACING!

 

so what you're saying is a larger turbine wheel, all else being the same will lower boost due to the fact that it takes more energy do move the larger wheel?

mike

 

I saw a picture of a wastegate right on the turbine, in Corky bell's book: maximum boost. That seams like the ulitmate setup, but...

1, would it work on a divided housing?

2. if you could, how would you do it? just weld a iron fitting on there at a angle. I got a idea in my head on how I could do it.

plus, makeing a manifold would be really easy, I could have a really simple manifold built by stainless works for about $200

 

where can I get a stainless 13b engine flange, and a stainless divided t4 flange.

 

Ok, I'm starting to see grass again in my front yard so I should probably get going on this manifold if I want to have it ready for the spring

After spending about a hour last night just starring/thinking at all the possibilities of what I could do I came up with 2 ways of making this work...

1. Weld some section of tubes to the turbine housing and to the WG flange.

2. Do like the mod pic I posted on page 1:



I've seen a lot of pictures of manifolds lately that "T" from the main runners right before the turbine flange. I've even seen one in that "1000 bhp grand prix cars" book that actually had a reverse Y junction that really made me scratch my head. After thinking it over I guess it makes sence to move the WG intersection point closer to the turbo. Correct me if I'm wrong but I think I'm having all these problems because of my WG lines come out of the manifold just too early. Here is a little pic I drew up quick to explain my theory.



To the left is the engine side of the manifold and the pressure it sees and to the right is the turbo side and what it sees as far as pressure. The first part of the manifold sees both positive and negative pressure waves while near the turbo sees only positive. Seeing both pos and neg waves can't be good to control boost. I think this is what Rice Racing was alluding to. So I'm guessing even if I "T" into the mains near the turbo instead of "Y" I'll still have better control than what I have now.
Did I make any sence here?

 

Here is another pic to aid in showing where I'm thinking of placing the new WG runners.

 

The reason some designs run the WG pipe closer to the turbo is because the exhaust pressure is higher due to the turbine necking down the exhaust flow.

Your manifold is good except for the rear WG pipe - to make everything compact, you compromised on the connection with the front WG pipe.  The two pipes should run independent of each other or at least Y into each other more smoothly.



-Ted

 

Yeah, I'd like to get away from the "H" pipe I have built in.

 

Hey Setzep, here is a picture of the Td07 25g I just bought... Look at the turbine, something look a little different to you?...Max

 

Wow, Max that looks totally different than my turbo! Is that a 14cm turbine housing? Take a look near the turbine inlet flange, on the inside of it you should see a # casted into it. Mine has a 17 cast into it.

 

Its still on the boat getting here!....
I have a feeling that the turbo you have is not sized right for the 13b, back to my original assumptions that all your problems lead back to the turbine size..I have 2 of these turbo's coming now actually, and both look like that picture... When I was in Japan, I think I said this before, but the housings that looked like yours were on motors like sr20's ca18's etc etc... Which explains your problem , its just to small for a 13b, and no matter where you put your wastegate runners, you would probably need 2-60mm wastegates or better to make it work...
Alot of people felt I should have angled and wye'd my runners more, but when I built my manifold, I looked at alot of the more popular manifolds for the FC that are available, and not only do som take it off at 90' angles, even ones like the HKS and Greddy cast, make the exhaust turn 180 degrees to out the wastegate, it was then I knew that runner placement was not going to be absolutley critical, and made the decision to shape the manifold in the interest of the exhaust gas flow to the turbine, for spool purposes, and it worked....There is a rule that all pressures in a duct system are equal in all directions within the duct system, and that applies to manifolds as well... I think you need to change that turbine housing to the right one, or clip the wheel, which I would do as a last resort ....
Incidently, in the FC3s RE amemiya video, Amemiyasan says right to the camera, the TD07-25g is the best possible match to the 13bt as far as turbines go, and visiting his shop, most of the cars, had Td07 -25g's on them...Max

 

It seems you are contradicting yourself here, first you say my turbine is too small then you go on to say Amemiyasan says it's the best match for a 13b??
Looking at the picture you poseted here it looks that your turbine is smaller than mine. When comparing the turbine clamps you can see how my turbine is larger than the one you posted.
Also I think my main runner ID (small) and my cosmo sleeves are screwing me over here. I don't think it's one single thing that's causing my issue, more like the combination of a few.
I few pages back IGY stated that my turbine housing looks like all the other TD07 turbos he's seen over on the other side of the pond. More confusion....

 

dp

 

Wow, and this is supposed to be the end-all solution?

Before you start to type that reply, let me qualify my statement...

At one point in time, I would've agreed.  Now that I know better, I know this is not true.

R.E.A. really disappointed me when they started to sell those stupid SEV things.  If you don't know what I'm talking about, please look into it.

R.E.A. is also very close to Trust, and Trust builds a lot of the R.E.A. products at one point in time.  Strut tower bars - look familiar?  Spark plug wires - look familiar?  Trust uses Mitsubishi turbos - R.E.A. recommends Mitsubishi turbos?  Boy, a coincidence?



-Ted

 

I was digging around looking at old pic's and found this one. It shows the turbine size a bit better than some of the other pic's. It's also a good view of the manifold.

 

If I the translation I got is right on the TD07, there are about 3 different types with many different rear houising available on each variant,.
I am not contradicting myself , the turbo you have is not the same as mine, yours clearly has a tighter wrap on the snail, especially on the rear part of the turbine, yours steps down huge on the rear wrap, where as this one doesn't...Its very hard to judge a/r by the outside appearance of the turbo I know...
But if you watch the FC3s video, and you see the turbine housing, its got the same square flange that mine have, where as yours seem to have a round flange, which leads me to think your turbo is not totally what you think it is, I looked through every Rx-7 magazine I have from Japan, and every Pic of a Td07, has the square flange...

It seems to me TD07-25, is like saying in Garrett terms, its a T04, there are numerous versions available with much different applications, and a p-trim .84 is along way from a 1.0 q-trim, but they are still t04b's...
I bought another Td07 this morning, and this is one is a fujitso engineering package, and low and behold, it uses the same rear turbine as the first one I bought..I looked at the ads closer, and both turbos are TD07-25A
While looking at Td07 turbos' I found the following numbers on various Td07's, tdo7s-25j, td07-25 a through to h, Td07d-25 a,b,c.. I think the turbo you have is a definetly a td07-25, but I don't think its the one that is "exactly matched" to the 13b. Your turbine clamp actually is smaller than the ones on my turbo's , look at the size of the clamp flange on the centre section compared to the height of the oil line bosses, your clamp is considerable smaller than the difference of the 2 bosses, where as mine is quite a bit larger than the boss difference, your centre section appears somewhat smaller than mine at the turbine flange...
I should have those turbos by the end of January in my possession, then I can take some measurements for you and you can have the numbers, I think we are gonna find they are a larger rear housing or the turbine itself is a different size/trim...I also got manifolds with them, so I can test it out that way, as well....

REted, No its an observation I made of the FC3s video, and don't you think if he was that intent on pushing Greddy Trust products, he would push a turbo that they market as their own, rather than a mitsu that can be bought without have to pass through their hands to get through any mitsu turbo dealer? Now If he said the T-78 33d is the best possible match for the 13b, I might tend to agree that he was just sales pitching a greddy product, however that is not the case, having actually been to the RE amemiya shop recently, he stocks very little Greddy product in his store, his inventory was varied among all the Japanese major labels, with no hint of any kind of favouratism played...
And sometimes shops have to sell things they don't like to sell, I don't particularly care for having to build chev small blocks for extra money, but it pays the bills...Thanks for the rather phalic response we have come to expect.......Max