GT2560R stage 3 Boost spike

I got myself a GT2560R on a stage 3 SR with a GFB boost controller. I'm having difficulties adjusting the boost to the required levels (17-20).

I'm getting constant boost spikes at the beginning of my pulls when I go WOT. Right now it's set so the max spike reaches 17.5 but then it tapers to 12-13 psi. It seems a bit extreme of a drop off. I know it's not the appropriate turbo for stage 3 but even so.

If I raise the duty cycle and accelerate gently I can hold 17 no problem. But then at WOT the spike goes above 20 psi.


There seems to be a restriction, but I'm wondering whether it could be the wastegate spring, wastegate door or the exhaust? Any ideas?

H Dev Stage 3? If yes, that requires a GT28RS, not a GT2560r. A GT2560r is the same as a GT28r, same size as a standard turbo but with ball bearings instead. You can run about 17psi with the GT2560r but thats generally considered its limit for it

I know, but 17 is what i kind of want, it's the minimum for stage 3 so it should be fine, i'd just loose a bit of power but no big deal. The problem is that spike. If i want stable 17 psi the spike goes well above 20 and I don't know if I can fix that.
If I had a 19-20 spike and 17 hold stable that would be perfect for me. Is there a way to reduce that difference?

I think you need a better actuator

Or you have a vacuum leak maybe? Check all of your hoses

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No leak, all checked. I got a forge actuator on the way, will get the spring kit and try one of the stronger springs.
It's worth mentioning I have a divorced elbow, but those are supposed to be better not worse.

And btw, maybe I'm being paranoid setting the overboost at 20. I have forged pistons, ARP studs and tomei MLS gasket. Maybe I can safely increase it a bit, that would give me more room to see where the spike reaches.

Divorced elbows are rarely better with internally gated turbos, they're usually shit.

Hmm, well i was considering getting a 3'' exhaust from a friend, not set in stone yet though. I would have to get me a new 3'' elbow and it wouldn't be divorced. Remains to be seen.

Yea you want a big exhaust, 3" all the way.

What size is your exhaust now? It needs to be 3inch all the way, turbo back for stage 3. You want as much free flow as poss.

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I'm not a fan of those divorced elbows, ideally you just want it to be as big as possible.

2.5 inches at the moment.

Well then i guess I'll try the forge wastegate with the stronger spring when it arrives and switch to 3 inch exhaust. I hope it should stabilize boost and reduce the spike.

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Originally Posted by suixo

2.5 inches at the moment.

Well then i guess I'll try the forge wastegate with the stronger spring when it arrives and switch to 3 inch exhaust. I hope it should stabilize boost and reduce the spike.

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You got it man. You need 3 inch turbo elbow and exhaust and a good actuator. What actuator are you currently using?

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Stock from turbo, 6 or 7 psi should be. I have a duty cycle at 40+ and i'm not close to 17 psi boost. To get that i'd have to go to 50 or 60 duty cycle which is way too much. I def need a stronger spring.

Yea ideally you want the actuator at 1 bar and let the boost controller do the rest.

What he says. The stock spring is probably 20 years old.

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Nah the turbo is new, gt2560r. But yes, i do need the stronger spring. I'm thinking the forge blue one which is around 18 psi. From what i've read they usually open sooner than they say. So the yellow 15 psi may be too low. I will just get the kit with all the springs and try which one is best.

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Originally Posted by suixo

Nah the turbo is new, gt2560r. But yes, i do need the stronger spring. I'm thinking the forge blue one which is around 18 psi. From what i've read they usually open sooner than they say. So the yellow 15 psi may be too low. I will just get the kit with all the springs and try which one is best.

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Ah ok, but still a weak spring. I think I have a yellow one in my forge. Holds a bar solid

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Nice, i will probably start with that one then. Thanks!