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Make My Gt30r Reach Full Boost Earlier....


Lithium
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Hi guys,

I'm bound to have spoken to some of you about this issue I have been fighting for a while but now I feel compelled to try and really get it nutted out, the lack of lower-midrange torque is starting to frustrate.

Anyway, the short of it is that my internally gated GT3076R (yeah yeah I know...) opens starts to open wastegate before it reaches the desired boost level - which induces a reasonable amount of lag any time I step on the throttle. Here is the best way I can demonstrate how it behaves when I am targetting 15psi:

Boost280kw.png

Obviously I would much prefer it to hit and hold 15psi instead of pissing around from 11psi to 15psi. I have tried an AVC-R and a bleed valve as different kinds of boost control which help SLIGHTLY but definitely don't fix it, and I am currently trialling a dual-port actuator which so far does the exact same thing. Today I decided that to rule out the possibility that the reason it spools lazily is a boost leak or some other issue elsewhere, I'd do a quick run to 3500rpm with the actuator hose removed to see how much it builds and my result is:

12082009065.jpg

So clearly the turbo and setup is capable of building 1+bar well before the 5000ish rpm I am stuck with at the moment, but the trick is making it do so without free boosting. Any one have any ideas? It may help reduce some stress here :ninja:

Cheers!

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Oh right - so your GT2871R behaved like I am describing and was actually resolved in the end with preload? OK I will max out the preload tomorrow and take it for a drive. The other thing I have considered is using the "Norgren" boost control setup Autospeed wrote up a while ago for their Audi, if anyone has any thoughts on it?

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Yep mine did that and more preload helped a bit but the thing that fixed it once and for all was enlarging the tiny internal wastegate hole.

Enlarged wastegate hole helped spool? I would have thought it would only help fight creep? I actually have a "big flap" internally gated housing - its not a tiny one.

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I think somehow we are forgetting what an actuator does? An actuator does not snap open @ 'x' preset boost level, If an actuator is rated @ say 8psi then it will be fully open @ 8psi however it will gradually open up from much lower pressure. The whole idea of an actuator is to create a linear onset of power. Simply increasing the the preload will increase the boost rating of the actuator not necessarily help with response...

The only way to fix the problem and have ALL your boost hold until 'x' desired level is to fit either a mechanical one way pneumatic valve before the actuator or use an EBC (which is basically the latter but with other fancy crap added to it and in cabin control...)

If you soley rely on the actuator you will never have your turbo's true response potential, however you will have a much smoother increase in power and provide your driveline with less hassle. Depends what you want.

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i had the same problem with my gtr with twin t517z as soon as i tryed running more the 18 psi couldnt fix tryed three diferent ebc all i could get the ebc to do was move the spyke in the rev range

in the end i bought 1.5 bar actuators worked a treat maby try buying a 1 bar actuater

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Enlarged wastegate hole helped spool? I would have thought it would only help fight creep?

it did both because with creep sorted, u can run more preload and/or reduce the boost the actuator sees (increase boost) but still have the same boost up high. I can't explain it very well.

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I think somehow we are forgetting what an actuator does?

...

or use an EBC (which is basically the latter but with other fancy crap added to it and in cabin control...)

One of the reasons threads like this can go in circles, or seem like people are missing things is when people don't read the original posters posts clearly - you obviously missed the 800x600 image of the Apexi AVC-R EBC I have been using to fight this issue :( I have been almost tempted to get a ball valve to put on the feed to the AVC-R/actuator... though I really don't think I should have to consider that.

it did both because with creep sorted, u can run more preload and/or reduce the boost the actuator sees (increase boost) but still have the same boost up high. I can't explain it very well.

Oh yep, that makes sense - creep hasn't been an issue, its just the bringing boost up at the start which is and I have my preload maxed out :)

Edited by Lithium
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I hadn't but just had a hunt around and found it, dammit I wish I found that before I bought my AVC-R :) It was actually vs the PFC boost control, but presumably the same thing.

Edited by Lithium
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Hey Man good to see the old girl still running. It was because of you I went with the Garrett housing on my 3071. Yes, it's a .82 and I can assure you your problem has nothing to do with the actuator control. Nismoid was close on this one when he said wind in some more preload. I have to ask if you have a 14lb actuator or the 7lb. If it is a 14 then it should be ok. If not then that right there is the problem.

Your compressor and therefore your engine is pushing enough boost through the waste gate flap to force it open. Stronger spring is required, simple. I had the same issue till I bought a 14lb actuator. I did that the second time I tuned it with the new setup and fixed it. A boost controller will only bleed air away from the actuator but it is the spring that controls the waste gate itself. Stronger spring, stronger waste gate control. You've got to love external waste gates for this very reason. Why do we continually use boost controllers when a spring will do the job better. All a boost controller dose is fine tune when the boost comes in and helps to stop spikes and such. If your running 15lbs then you need a 14lb actuator. If running 18lbs then get a 17lb actuator.

Oh, and the diaphragms in these actuator things can start losing control after a time and thats another reason external is better but like you I like the stealth of an internal waste gate.

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