Kraken Kit+GBC22 = overboost
 

Hello, I am currently having a boost control issues and I'm looking for possible suggestions on correcting it. I'm considering porting the wastegate orifice but there isn't a whole lot of material to remove on this GBC housing and my tuner isn't very confident that its going to help with the creep.

Setup: VVT motor, stock other than a flat top intake manifold and all the supporting mods, Garrett GBC22-350 with the .5 bar actuator, kraken top mount kit plus intercooler and full 3 inch exhaust. My tuner was unable to control boost at all. No boost controller hooked up and my tuner verified that the actuator was fully opening. Tuner says that he has verified that it is not lack of timing or cam timing. Also, the flapper is free to fully open. The turbo would hit 11psi by 4200 rpm and continue to climb until he let out. Maxing out at 15ish psi by 6k RPM. Kraken says that I'm the first person he has heard of that has had this boost control issue.

It looks like I might be able to open up the orifice of the WQ by maybe 4-5mm and still have 3mm or so for the flapper to seal. I'd be going from a 20mm orifice to 25mm. But I'm not sure that will be enough. Any suggestions? Feeling like a new turbo and tune might be in the works because adding an external gate to this manifold will be a pain.

Thanks in advance.

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Wire the gate open, looks to me like you have an 11 psi actuator.

I'll give wiring the gate open a shot. I checked the wg part# and it's a 7psi gate.

Not really related to your question/issue, but once you get it fixed and dyno tuned, we'd love to see the final results. I've not been actively looking for information on this turbo, but considering the age of the frequently used GT2560R, I'm sure some people would like to know how it performs.

It's mostly fixed now. Porting the wastegate actually helped a ton. It stays around 7psi and sometimes creeps to 9psi by redline. I'm surprised it helped as much as it did.

My tuner doesn't think the car needs to be retuned but I do want to dyno it now and see where she is at power wise. I'll post the results when I get it completed.

I hade the same issue with the kraken kit GBC20-300 with 3" exhaust decat.
Overboosting with 3 actuators 1bar/0.5bar/0.35bar Crack pressure of the actuator.
Ported the wastegate and now is running fine. I have some engine noise and the knock detects the noise coming from the engine bay.
Speak with your tuner to give you more timing and more fuel to cool the exhaust gases + try the highest octane fuel in your area.
If you can share the boost map+ timing map + fuel map ?
i will do a dyno run when i will have the final map done on my car. I am running 1.05 bar boost has a lot of power but the timing is not touched... i will see how it goes after i fix the engine noise




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Hey man, I had forgotten about this thread, but I got the car dyno'ed on wastegate pressure. It still crept to 8-9psi by redline but made 253whp.
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That's a great looking power band! Nice and linear! Good torque.
@Bereanu999 do you have a dyno graph with the 20-300?

Hope everyone doesn't mind the question from an ex MX5 owner, but the query is in regard to these turbos on another car. I fit x2 of the GBC-350's to my 2004 Noble M12.
Believe i'm the first to try these on this particular vehicle platform globally, car made just under 500 (crank hp) at 0.9bar, but very little info around in general on these turbos on any platform.

Reason for the register, is the Miata/MX5 forums seem to the only place to find real world experience of the GBC's, i had to customise the actuator brackets, custom oil drain etc to work on my engine (3.0 V6).
Anyways i noticed the so called 0.5bar actuators run closer to 1bar! I ended up fitting Forge actuators to have a low boost mode (not that i never used low boost). These actuators started to bind a little, and caused a few slight overboost situations, i removed electronic boost control and noted alot of creep, 0.5-0.9bar ish. Thankfully my tune is around this area, but in the short term going to fit the original Garrett actuators back on, but fear even more boost creep, as they open WAY less than my Forge actuators do.

I really don't want to have to port the wastegates, but have GBC owners felt this was the only way to keep Creep at bay?

Thanks

Welcome! We can't answer any questions without photos, in the case of exotica, LOTS of photos! (Always been interested in those cars, that has ABSOLUTELY nothing to do with wanting to see photos of yours :giggle:)

Sorry, can't help with your question, hopefully someone will be along soon with some.

The only way I was able to control the boost was by porting. It wasn't too bad of a job, just a little time consuming. It seems like many other people have experienced this same issue with this turbo.

Not a direct answer, but have you considered an electronic wastegate actuator? They are somewhat pricey, and reliability is unknown to me, but they are becoming quite common in OE applications lately and seem like a good solution overall, particularly considering control options.

That won't work any better then a regular wastegate with controlling boost. I believe the issue on the GBC is the hole not being big enough to allow enough air through to meet target boost levels.

On a GBC20-300 I had no issues commanding whatever boost I wanted as low as 6-7psi steady with 38mm TiAL (IWG welded shut), so I'd say it's simply the IWG hole as shuiend mentions.

Thanks for the replies. The Garrett actuator I bench tested, doesn’t flinch until 0.5bar and carried on moving the rod until around 1.5bar! I’ve no idea how Garrett advertise these as 0.5bar actuators as don’t start moving until after my 0.7bar forge ones! Anyways, great spool, but Garrett ones started to creep to 1.1bar and may have gone behond that, so past where I’m tuned for, shame as felt rapid.
Going back to the forge actuators with a slightly stiffer spring, 0.7 vs 0.9bar, so essentially where my map is.
I think some of this issue is how much that wastegate flapper can open to divert the gases. For anyone wanting to run less than 0.9bar, worth porting seems to be the experience. Perhaps the porting helps that Garrett actuator doing what it says it will do also. I did want a low boost option for a wet track day, guess I’ll just deal with my full boost setup until I have the energy to remove and port 2 turbos!

Thanks again

One way to test for sure of your porting job is to physically wire open your wastegates and go take a log. If the holes are big enough, you should only build 1 or 2 psi of boost.

Hi there,

I agree with Jim above, frightfully little info on these turbos around!

I’ve got the 350 and I’m about to fit it to a forged NB Kitcar build. Low mount mani, all supporting mods you’d expect - but I’ve been warned of serious creep!

I had a look myself - but it doesn’t seem possible to port it symmetrically and fully, without removing the flapper entirely? There is no mechanism to disassemble the actuator arm as far as I can see? I’d rather not break and attempt to re-weld it myself!

In order to remove and reattach the flapper I believe it requires grinding and welding. I was able to sufficiently port mine without removing the flapper. Just used a Dremel with various carbide burrs and was very careful.

Before and after
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nice! though my issue is i have 2 of these on my setup, lol, having to remove and dismantle exhaust housing twice when i imagine theres prob 4-5hrs of work there with a burr bit PER turbo fills me with dread.

to update this, i tried out 0.9 actuator spring also (cracking at 0.5bar), and still got creep behond 1bar. i noted the biggest movement/opening with the wastegate arm to open flapper was with my original actuator springs on the forge units at boost level i want to run (0.7 bar, with a cracking pressure of 0.35)...
i am potentially going to explore restrictor rings on the exhausts before the hassle of getting 2 turbos off. or i bite the bullet and just remap for 1.1bar or something and make an extra 40hp :-)

No idea how hard it is to pull the turbo's on your vehicle. But porting itself should only take 10 minutes or so per turbo. I use a HF electric die grinder and some carbide bits off amazon.