Actuator Question - Quick One

[rawd]

hi all,

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quick question for those that don't want to read the rest:

does running a 7psi or 10psi actuator make a difference in boost response if i am running a boost tap controller? theoretically the boost controller should keep the wastegate completely shut until a certain level, right?

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long version to help those with infinite boost issues in the future:

i have a hybrid boost controller installed on my rb20. ever since i bought my car it has boosted to 14psi even on its lowest setting and finally got around to investigating.

1. took the boost controller out and routed vacuum line straight from compressor housing to STOCK rb20 actuator. took it for a spin and still boosts to 14psi but just more gradually due to lack of boost controller solenoid.

2. took the actuator rod off the wastegate thingy and took it for a spin. gunned it up a hill in 2nd till 6000rpms and it only hit around 9psi at 6krpms after a laggy build-up. i have an aftermarket x-force dump but i am pretty sure the wastegate isn't hitting it. the wastegate swingy thingy on the outside hits the heatshield attachment first before anything else. so my wastegate should be opening all the way if i don't go straight to 14psi, right???

3. so, went back to the vacuum hose from nipple to actuator, pulled it off and chucked a new one on to eliminate the split hose issue. went for a spin and still hitting 14psi.

4. now i'm here. i assume the actuator is f**ked but dont have access to compressed air to check. might get my girlfriend to try and blow 10 psi into it - hahaha. so this comes back to my quick question - i'm chucking an r33 turbo on soon and it has the 7psi actuator. should i run the 7psi or the 10psi r32 one with my boost tap for best responsiveness or it won't matter? could anything else be causing my overboosting problem that I haven't covered, cos the last thing i want is blowing my new turbo if it's something engine related.

thanks folks

[lachlanw]

it is hitting it . with wastegate rod off you sould have pretty much no boost anywhere . maybe 1-2 ish . nowhere near 9psi

[rawd]

shit. what a pain in the ass.

x-force dump pipes on stock rb20 turbo

it is hitting it . with wastegate rod off you sould have pretty much no boost anywhere . maybe 1-2 ish . nowhere near 9psi

[lachlanw]

how far does it move before it hits the heat shield you mentioned ?

[D_Stirls]

no it might not be hitting, what turbo is it.

I.E. if you put a T2 turbo with a small wastegate on the rb25 and run it with up the actuator dissconnected it'll produce a large amount of boost before it chokes because the wastegate can't pass enough gas and therefore forces gas through the turbine and boost is produced.

What your problem is is that the wastegate isn't big enough to pass enough gas to drop the boost below 9psi in the top end. this is your lower limit and you can't run less that that. Any actuator you put on the turbo will then increase the figure because you are adding a further restriction on the wastegate.

Go get you wastegate machined and fit a bigger wastegate flap.

Edited August 31, 2009 by D_Stirls

[rawd]

how far does it move before it hits the heat shield you mentioned ?

moves around 50-60 degrees, i do get your drift though. how far should it be swinging? if it swings as much as it should, could it still be hitting inside? factory heat shield on a stock rb20 turbo.. shouldn't be an issue but i'll check anyway to be sure.

[rawd]

stock rb20 on rb20det

don't think that's the issue.

i'll be swapping over a turbo in a couple of weeks so i'll make sure the r33 turbo doesn't hit before going on. reckon a dremel is powerful enough to scrub a dump pipe down if that's the issue?

no it might not be hitting, what turbo is it.

I.E. if you put a T2 turbo with a small wastegate on the rb25 and run it with up the actuator dissconnected it'll produce a large amount of boost before it chokes because the wastegate can't pass enough gas and therefore forces gas through the turbine and boost is produced.

What your problem is is that the wastegate isn't big enough to pass enough gas to drop the boost below 9psi in the top end. this is your lower limit and you can't run less that that. Any actuator you put on the turbo will then increase the figure because you are adding a further restriction on the wastegate.

Go get you wastegate machined and fit a bigger wastegate flap.

[D_Stirls]

yeah it isn't the issue in that case.

You should get 90 degrees of movement with the actuator disconnected.

[rawd]

oh shit actually it is getting about 90 degrees

starts at around 10 oclock and swings anti-clockwise till about 5-6

need to take geometry again i think

f**kk. so it should be opening all the way.. could it be that i didnt wire it open? thought that exhaust gas would be suffiencient to push it open.

Edited August 31, 2009 by rawd

[sickr33]

what boost do you want to run?

are you sure its a stock actuator? (stock gtr ones are 14psi) might be worth looking into!!!!

also what exhaust do you have excessive back pressure may be the cause. eg (blocked cat)

running a 7psi or 10psi actuator make no difference in boost response. eg will still hit 7psi at same rpm but the 10pis one will keep climbing until 10psi

[rawd]

I want to run 12 psi on the r33 turbo - right now I can't get it under 14psi

Could be a gtr - replaced by the previous owner maybe. Still doesn't explain the disconnected actuator still climbing to 9psi. Think I swung the wastegate thing the wrong way though when i disconnected it so I'm gonna do the test again - plus it's fun giving it with the wastegate roaring.

X-force exhaust with twin pipes instead of cannon.

Thanks for the short answer - I guess I'll run r33 actuator with the boost controller then. Cheers.

[heller44]

Stock gtr actuator is ~6psi.. aftermarket ones come as ~14psi. Ran mine on actuator for about 6 months, direct feed, felt like an excel.

[sickr33]

im fairly certain gtr's are 14psi but they also run a boost restricter (solenoid on the drivers side)

moving along

is dump and front in one (turbo to car in one)

or is it a 2 peace

i have xforce dumps on my gtr and they over boosted like shit

look them off and relised where the split type dumps join the hole was way smaller than the actuator pipe eg (pipe 1inch hole 0.5 inch)

i opened the join out as far as i could never had another problem!!!!!!!

i have attached a pic showing what i am talking about

hope this helps

[bradsm87]

My Xforce SR20 dump was the same. Pretty Rubbish.

[rawd]

yeah i think its dump and front in one

not split pipes like the one in the pic though

going to try attack it with the dremel when i do my turbo change. fingers crossed.

[Birds]

Interesting that so many people, myself included, have overboosting troubles with aftermarket dumps. They must be manufactured pretty poorly. Alot of them advertise guaranteed boost gains so I don't doubt that sometimes it's on purpose, but most of the time it'd be poor weld jobs / pipe positioning.

In process of trying to get a refund off my supplier.

[lachlanw]

gtrs dont run 14 on the actuator . there is no way you can run less boost than the wastegate spring pressure (properly . excluding leaks and leaking blow off valves)

[89CAL]

thats strange, i got a full x-force exhaust going from a stock exhaust and mine hit the same boost without having to touch anything...

Just a bit quicker response i think from the bigger exhaust

[sickr33]

i have had a full xforce system on you r33 gtst and it was great

[D_Stirls]

that's why bellmouths s#*t all over split dumps.