Wastegate problem, please help

[Colton]

I know you guys focus on the KA, but I respect your knowledge and honestly believe you guys might be able to help me (I also posted this in the sr forum)

I'm using an ebay 40mm HKS style wastegate. The spring they gave me was junk so I went ahead and ordered a true HKS spring rated at 9 psi. The wastegate holds 8-10 psi under light load (1st and 2nd gear), but when the engine starts to rev past 5000-5500 rpm the boost will creep to 12 psi.

When I shift into third or fourth and do a few highway pulls the wastegate will hover at ten psi until 5000-5500 rpms then it pulls to 12 psi and doesn't seem to want to stop!!

I don't want this type of boost right now. The car is scary fast at 9psi. Please help. My mods are below.

Precision turbo SC-61HKS step 2 264 intake and exhaust camsHKS cam gearsHKS valve springsHKS 2.0mm head gasketGreddy style intake manifold (ported)Greddy front mount intercoolerCustom 3 inch downpipeApexi N1 cat back (with test pipe)Equal length tubular top mount manifoldPorted and Polished headUnorthodox racing pulleyand other misc. stuff

I have 740cc injectors, but currently I'm using the 370's. I want to make sure everything works at low boost with my stock computer before I go modifying everything else (I'm using an apexi safc 2 to add fuel where it's needed, but honestly the stock fuel system maxes out at 11psi (completely maxed out)

Please help!!

[Fenvy]

are you using any boost controller? or are you controller it from the wastegate only?

I am led to believe that wastegate alone isn't enough to control amount of boost pressure

[Colton]

I was under the impression that an external wastegate could hold x pounds of boost with the desired spring set at X pounds. I have boosted two acuras before with out boost controllers, just external wastegates and they held the boost accordingly. Please advise.

I'm not going to hook up my boost controller until the boost becomes less eratic.

I thought a boost controller aided in helping to up the boost not keep it at the base wastegate setting.

[Colton]

I'm sorry I didn't clarify this is an external wastegate with a divorced screamer pipe.

[Fenvy]

sorry, I am not much help, I never had external wg

the eletronic boost conroller I am using up the boost and does a fairly good job at smoothing it out when it gets close to peak setting

[Colton]

Could I possibly need a bigger wastegate, could I be flowing to much air?? I don't think this could be it, but I could be wrong.

[nissanfanatic]

No. Your wastegate size is fine.

How is the wastegate flange set up on your manifold? And have you tried running it just plain open to atmosphere(without the divorced pipe). Its gotta be some kind of restriction going to or leaving the wastegate.

[Structure240sx]

exactly, backpressure from the dump tube

or resctriction before the wastegate

in your manifold is there a tube coming off for the wastegate or does it flange irght ont he manifold collector or runner?

[Import_Ant]

No. Your wastegate size is fine.

How is the wastegate flange set up on your manifold? And have you tried running it just plain open to atmosphere(without the divorced pipe). Its gotta be some kind of restriction going to or leaving the wastegate.

agreed, that wastegate is plenty big. I'm running a Tial 34mm and it works just fine for a T3/T4 (and should up to 22 psi at least). there' got to be some sort of restriction in the dump from the wastegate or poor location of the flange could be causing it as well.

just a stupid question but alot of external wastegates have two bungs, one is for the ID signal from the turbo and the other is for boost control. do you have the second bung plugged or are you running it to your boost controller? a test would be to disconnect everything from that bung and run full wastegate mode and test to see if you get any creep. On that note, where are you running your ID from to the wastegate? the closer to the turbo the better.

[Colton]

Thank you guys,

When I say divorced, I mean the wastegate is atmospheric (divorced from the down pipe, I also took the screamer pipe off ).

The manifold is a tubular design and it has a small tubular section that comes off of the collector to a flange for the wastegate.

I hooked up the wastegate via the side nipple and did nothing to the other top/bottom nipple (however you look at it). This is connected properly, I can assure you. The line is only 9 to 11 inches long.

The only thing I can think of is that

A. The line is leaking from the compressor nipple or wastegate nipple, and you don't see it leaking till high load.

B. The wastegate is not fully opening and binding somehow.

C. The stainless steel tube connecting the wastgate flange to the manifold collector is to small of a diameter to expel the exhaust gasses. I believe it's roughly the same size as my manifold piping.

Any responses are appreciated. SR guys haven't even responded, figures.

[Import_Ant]

The only thing I can think of is that

A. The line is leaking from the compressor nipple or wastegate nipple, and you don't see it leaking till high load.

B. The wastegate is not fully opening and binding somehow.

C. The stainless steel tube connecting the wastgate flange to the manifold collector is to small of a diameter to expel the exhaust gasses. I believe it's roughly the same size as my manifold piping.

Any responses are appreciated. SR guys haven't even responded, figures.

A) if you have a spare length of ID line maybe try replacing it and zip-tie it at the ends but I highly doubt that is the prob (good idea though)

b) that's certainly possible, you could try pulling the wastegate and test the action yourself. I know on mine (w/ .5 bar [7.35lb]) spring i can compress it by hand with some effort.

c) that shouldn't be an issue, it probably isn't too long anyhow, what is it maybe 1" out from the manifold? if that.

good luck getting this resolved I'm stumped.

[klattr1]

who makes your exhaust manifold?

that might tell some things.

[Colton]

SSautochrome, and before anyone starts saying that it's crap.

I already resurfaced all of the flanges (after heat cycling the manifold) courtesy of NAPA's machine shop ($92).

welded in a small brace (to support the heavy turbo).

rewelded and smoothed the collector welds (very crappy to begin with).

I also bought a true HKS wastegate spring for $28 shipped.

Other than that I purchased the wastegate and manifold package for $278 shipped.

Total investment $398 to my doorstep.

I can't complain this manifold fits great and I've had no issues to truly complain about.

I'll keep everyone updated.

If you are questioning the fitment (clearance wise) check out the picture in this other thread

zerothread?id=126007

[Colton]

Don't mind my plumbing 4 inch to 3 inch adapter, I have nice reducer on the way and a 4 inch 45 degree mandrel bent piece of pipe to finish it off (I know it's super ghetto right now)

[TrunkMonkey]

do you have better pics of the wastegate and manifold?

-demetrius

[Colton]

I apologize that is all the pics I have right now, but you can see that it fits nicely, clearance wise.

[:: orion ::]

If the spring is correct...

The wastegate is big enough...

And the source is proper...

...and they all sound OK...it's the manifold design.

I have a buddy who made his own KA turbo mani, and had the same issue(s).

He modeled it off of the Full-Race SR mani...but that's not too different from your in terms of the collector and wastegate placement.

You need to either:

1) Swap manifolds to something more reliable and better desinged

-or-

2) Modify the manifold so that the WG port is larger, or at a better angle, etc...

The exhaust takes the path of least resistance...if you have high-end boost creep, the exhaust is finding it easier to go through the turbine rather than the WG - Which is NOT uncommon on poorly designed tubular manifolds.

- Brian

[TrunkMonkey]

my eyesight might be going south, but it looks like your wastegate is pointing straight down. if you're using the manifold that i believe you are (the same tubular manifold that SSAC offers for the KA) shouldn't your wastegate be pointing towards the wheel well?

the only other thing i can think of is along the lines of what brian is saying...

Quote »The exhaust takes the path of least resistance...[/quote]even at 40mm, i'm wondering if your wastegate alone can handle the efficiency at which your cams, manifold, 3" exhaust, and test pipe are moving air.

-demetrius

[nissanfanatic]

Quote »my eyesight might be going south, but it looks like your wastegate is pointing straight down[/quote]Looks that way to me too. Does the wastegate tube make any sharp turns before it flanges and meets the wasteagate? The way I see it, you can do one of two things:

1)Put on the 740cc injectors and just tune for the boost creep until you get a chance to fix it.

2)Pull the manifold and fix the problem.

[Colton]

The manifold has a 45 degree coming off of the collector for the wastegate, I can definately see what you guys are saying, but in better news one of my npt fittings on the wastegate was loose thus leeking pressure at high loads!!

I'm going to fix this problem, port the wastegate opening in the collector better and see if that works. If it doesn't I will cut the wastegate tube off and reweld a tial tial flange almost directly to the collector. I'm sure one of the ideas will solve my problem, u guys are great!