dannobre

iTrader: (3)

You guys are like watching two chunky girls mud wrestle....you know you don't want to look....but here is just something that makes you do it

The wastegate is supposed to be closed till boost threshold and then open and close to keep boost stable....so why not fix it so that it works that way

NgoRX8

iTrader: (1)

Update time

I was hoping to Bump this thread back in glory... but...

I purchased an actuator from MazdaManiac with a much larger diaphragm. Made my HKS actuator seem puny.

I did a run with b/c off, 2nd gear, and I only made 3.8 psi max. May still be dropping off as well because I saw below 3 a could times but at that low of a pressure I cannot say. Tried it with the b/c on and I barely got 4.0 psi even with my b/c set to 7 and 10 psi (could be a b/c thing, but I doubt it). According to my boost gauge, the cracking pressure on the wastegate is about 4-5 psi.

I decided to do a run with the wastegate disconnected to see if it was still blowing open. 2nd gear results showed hitting 11 psi in midrange (I backed off when I saw 9 so I believe I might have had more to go), but top end above 6k rpm I could only produce about 8 psi max.

I'm tempted to add tension to this actuator now. I have it barely 1/2 a turn from being slipped on. My HKS actuator, which had 6-7 psi up top with the wastegate disconnected, had 7 full turns in. I'm making 8 psi right now with 1/2 a turn.

Regardless of tightening it down, it seems that this new actuator has the same problem of blowing open like my previous actuator.

Kane

iTrader: (1)

Dude.... that is just weird.

I made and held 9 PSI with Jeff's actuator and no BC..... is your turbo spun or what?

Try tightening it a turn at a time. A good rule of thumb is that you should have to WORK to put the WG actuator on the flapper valve.... but not pull the actuator arm any.

Brettus

iTrader: (2)

yep - one turn at a time till you get what you want . Then do a maf log

MazdaManiac

iTrader: (3)

Is it actually blowing open or is your turbo out of puff?

Its a kind of rhetorical question because that actuator is not blowing open. Not from exhaust pressure, anyway.

Kane

iTrader: (1)

I concur.... if it's the same actuator I have - it WILL hold at least 14 PSI to redline with an EBC.

Brettus

iTrader: (2)

/\ but not the same wastegate - maybe Ngos is bigger in diameter ?

NgoRX8

iTrader: (1)

I assumed it was blowing open from the test I did back in January. When I restricted the flapper from moving, and almost closed off, I boosted above 12 psi almost instantly above 7000 rpm.

NgoRX8

iTrader: (1)

So I believe I may have ultimately discovered my problem. (hope I'm not jynxing myself)

I decided to take off my downpipe and examine the wastegate and its surroundings more closely. I noticed that my wastegate flapper was a bit different than the t25 .64 garrett turbine housing I have. Unhooked the actuator and noticed a big difference in the surface area of the wastegate between my two turbine housings.

The .64 a/r garrett turbine housing has a hole diameter of 1 inch, giving it a surface area of .785 in^2. My .86 a/r turbine housing that I'm using has a 1.25 inch diameter. That means it's surface area is 1.23 in^2.

With over 50% more surface area , I believe this is the problem.

Gregs was able to measure the greddy turbine housing wastegate and it was 1 inch as well.

I would like to know, either from Jeff or anyone who has the 3071r on hand, if their wastegate is as large as mine.

I may go ahead and pick up a new turbine housing real soon.

Here are a few pics I took to show the difference. sorry, I can't resize on my current computer.

Brettus

iTrader: (2)

I think you have nailed it allright

swoope

iTrader: (5)

wow,

you have a messed up flapper!

just had to say it..

beers

Brettus

iTrader: (2)

/\ yeah can't control his flapper - never a good look . LOL

MazdaManiac

iTrader: (3)

I'll have to wrap my head around this one, but the size of the bypass shouldn't make THAT much of a difference (if any at all), other than the mechanical difference (lever arm) with the actuator diameter (which you've already addressed).
It simply having more flow area shouldn't reduce boost since it'll still close again if the output of the turbo drops below the target boost.
Think how big the flow area is on an external wastegate.

Brettus

iTrader: (2)

/\ since it has 56% greater surface area , there is also 56% more force applied to the lever arm . Taking into account the success of the earlier test in which he got 12psi by forcibly holding the WG closed . The conclusion is pretty obvious .

MazdaManiac

iTrader: (3)

Except...

My first turbo on the RX-8 was a T3/T4 hybrid with a wastegate port equal to that on Danny's car and it easily achieved 11 PSI.
That is a smaller turbine, so more exhaust pressure on the flap.

Your math is off, btw. 56% greater surface area on the flap is not 56% more pressure and the ratio of the port area to the actuator diaphragm is still less than the same on other turbos without this symptom.

Be careful assigning causality to coincidence.

Brettus

iTrader: (2)

What actuator did you have thenm and are you 100% positive you got 11psi at high rpm ?

I said Force not "pressure" . Math is fine .

We know that there is high exhaust backpressure from the renesis/greddy type combo which is obviously more than in other scenarios.

The test where he forced the WG closed took out the actuator as a variable so there is a lot more than coincidence here .

MazdaManiac

iTrader: (3)

Same actuator. I even hit 14 PSI at a few points, but the EGTs were unbearable. Hence the switch to the bigger turbine.

Sorta, but since it's not the issue, it doesn't really matter I guess.

All that did was remove the signal from the equation.

Brettus

iTrader: (2)

Do you at least agree that there is a very high probability that the issue is that the wastegate is still blowing open ?
If not , what other possibilities do you see ?

NgoRX8

iTrader: (1)

It just seems to me that this is the case.

Thinking about how the actuator works, it extends a certain length per a specific amount of pressure. When I first ran MM's actuator with 1/2 a turn preload, I was only able to obtain 3.5-4 psi at the turbo (monitoring with a boost gauge). I believe that more exhaust is being bypassed and so for the same stroke length of the lever arm, the pressure at my turbo (as well as at my engine) is lower for this reason. A much stiffer spring would probably fix this, though Jeff's actuator is already pretty solid.

Through more testing, I came to conclude that the wastegate really doesn't need to open much. In my case with the larger wastegate bypass anyway. I never utlized the full extention of my actuator because my boost would never be high with it, even <45 degrees open. Restricting the wastegate a drastic amount via my HKS 7 psi actuator (which is know is blowing open), provided me only 3 psi down low, though would boost creep up top to 6 psi.

If I ran with the wastegate disconnected with either my 10 psi actuator or MM's actuator I could see boost rise quite a bit at the turbo (not WOT). Running at and below 10 psi, I tend to see about a 2-2.5 psi drop at redline. Running at 12 psi, my boost dropped to approximately 8.5-9 psi up top. I also see the pressure drop at my turbo as well. Boost isn't being lost, it just isn't being made.

It simply drops based on rpm and my peak boost. With MM's actuator, I believe I can hit close to the target pressure up top if I go WOT at a higher rpm, but once the wastegate gets the signal to open it just drops.

I think a new turbine housing with a smaller wastegate bypass would at least be the answer to the first problem I have (much lower boost than the specified actuator pressure).

MazdaManiac

iTrader: (3)

Just put a bleeder valve or a restrictor on the WG signal. Much easier than taking it all apart.