Hks Gtrs On Rb20

[floody]

i may have the wrong end of the stick here, but if the flap is not opening enough it will cause higher boost/boost creep & his issue is the opposite.

could be possible the flap is hitting something & not closing properly i spose

Unless its a combination of issues, i.e. the gate not being held shut long enough to build boost low in the revs, but the separator restricting its movement enough that it builds big boost up high...

[NWR31]

maybe, but his first issue seems to be the gate is opening to early.

no exhaust manifold leaks?

[nizmonut]

id say the spring in the waste gate actuator is either weak, weakend or broke. the idea is that most guys pinhole the waste gate actuator housing to deliberatley leak boost as to create a higher boost pressure. and yes your better running the actuator by itself, after all it in it's self is adjustable, let alone having the boost controller aswell. note the maximum boost you can create is up to the amount of pressure the spring in the actator can push, if maximum adjustment is only 15 psi , dialling up 18 psi on ya boost controller wont do jack.

[PM-R33]

id say the spring in the waste gate actuator is either weak, weakend or broke. the idea is that most guys pinhole the waste gate actuator housing to deliberatley leak boost as to create a higher boost pressure. and yes your better running the actuator by itself, after all it in it's self is adjustable, let alone having the boost controller aswell. note the maximum boost you can create is up to the amount of pressure the spring in the actator can push, if maximum adjustment is only 15 psi , dialling up 18 psi on ya boost controller wont do jack.

Incorrect.

The maximum boost pressure and quickest spool up your turbo can do is with the wastegate flap wired shut so it never opens. This will cause the exhaust gases to continually run through the exhaust wheel and increase boost pressure as revs increase to a maximum pressure that the turbine itself can make, has absolutely nothing to do with the actuator spring pressure.

A turbo running off of an actuator just itself is in no way better than running a turbo off an actuator wired up to an electronic boost controller. With the turbo running just off the actuator it will still slowly creep open and leak of exhaust gases through it and then slowly open the wastegate as the spring pressure is overcome by the boost pressure it can hold (ie. usually 14-15psi on its standard form on a hks item).

With the electronic boost controller you can keep that wastegate held shut and then snap open as quick as possible when the desired boost pressure is achieved. This gives a much quicker increase in boost pressure.

Test it yourself, wire up a wastegate shut and see how quickly it spools up as compared to just running off the actuator with no boost controller connected.

[tp1gts2]

ok, so ive just taken the dump pipe off and was going to get the wastegate part of the split dump chopped off down the bottom and the hole in the exhaust welded up.

now ive taken it off, i can see that there would still be a gap up at the flange between the two pipes because the gasket dosnt run between them, can this vacuum still occur and pull my wastegate open even with a gap up the top?

its gotta be a pretty big vacuum to pull it open, the actuator is fairly stiff!

seriously thinking of getting my stock exhaust manifold modified to take a external gate and get rid off all these problems it could be in one fowl swoop! have a mate that can do it for $50 just means i gotta take the manifold off for the first time in 16 years

thanks everyone for your help!

[Roy]

It has less to do with the gate then something else wrong somewhere. I know of an RB20 happily running a GT-RS, here is a few sheets of it dyno alongside my car

As you can see it has no problem holding boost (lower curve GT-RS, upper curve my TD06) If anything you can see its boost is creeping up

And on a Mainline Dyno it made 208rwkws...which always reads lower then an Dyno Dynamics. For example on a Dyno Dynamics my car makes 260rwkws, on the Mainline Dyno it makes 244rwks, so this particular GT-RS is probably making around 225rwkws with a conservative tune

There is something else wrong in there somehwere, it could be as simple as the ignition isnt right

[THENIG]

ok, so ive just taken the dump pipe off and was going to get the wastegate part of the split dump chopped off down the bottom and the hole in the exhaust welded up.

now ive taken it off, i can see that there would still be a gap up at the flange between the two pipes because the gasket dosnt run between them, can this vacuum still occur and pull my wastegate open even with a gap up the top?

its gotta be a pretty big vacuum to pull it open, the actuator is fairly stiff!

seriously thinking of getting my stock exhaust manifold modified to take a external gate and get rid off all these problems it could be in one fowl swoop! have a mate that can do it for $50 just means i gotta take the manifold off for the first time in 16 years

thanks everyone for your help!

Factor in drilling out some exhuast manifold studs, which can be quite a pain, make sure you know what you are doing if you decide to drill them out yourself, if it hasn't been off in 16 years and you manage not to break one then go buy a lotto ticket. That's of course if there isn't one already broken, happened to me and ended up being a costly exercise, but could have been more if an oil gallery was drilled into. You will need a right angled air drill a good centre punch. Maybe try that loctite 'freeze release' stuff, it didn't really work for me but you may have more luck.

I would prolly try looking into some other things first before opening up that can of worms.

[tp1gts2]

good news, ive found the problem! it now hits 18psi at about 4100-4200 i think

i had the bleed valve wound out a heap like it said on the bleed valve's instructions, and when i took it for the first drive it topped out at 18psi so i thought i was on a winner and fluked where id set it up to.

turns out i had it would out way too far and the pressure was getting straight to the actuator.

i shouldve clicked earlier when i took the bleed valve out and it didnt change one bit

anyway, im just happy its sorted now, luckly i had this brain wave of putting the dump pipe back on and trying a few other things like winding the bleed vavle almost all the way in

was seriously thinking about not posting this up on here because i now look like a tool haha

thanks to all that helped, but it was just me being a muppet causing the problem

[PM-R33]

Glad you solved the problem man

[R31 POWER]

Retune now with more boost??

[tp1gts2]

im going to wait until ive got the plazmaman plenum on before i go for the retune, unfortunately it will stuff up the idea of comparing the plenum's but money is scarce.

im also going for a different tuner this time because i think a good tuner should have picked this problem up to start with!