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Rb25 Turbo On Rb20det

Wogan

By Wogan,
in Western Australia

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Wogan Proficient

Wogan

Posted
Posted

Hi all..

My 32 has a similar setup to many many other 32's in that i've got a series 1 r33 rb25 turbo on my rb20. I'm running 14psi and i'm pretty happy with the power it's producing, however it seems quite laggy for such a small upgrade in turbo.

I hit full boost around 4500rpm which is still usable, but i have seen dyno sheets from other cars (Bubba's springs to mind) with the same setup but reaching full boost closer to 3500rpm.

The only difference i can see is that i'm running a manual boost controller as opposed to an EBC.. could this delay in full boost be caused by wastegate creep which would be eliminated by an EBC or is it something else?

* i should clarify what i define as "wastegate creep" since i have heard other people define it differently: as the wastegate is a mechanical device, it begins to open slightly as the car comes onto boost. eg: rb20 actuator is 10psi for fully open, however when you're at 5psi the wastegate would be slightly open due to the pressure.. not enough to open fully but a little.

EBC's try to eliminate this by not letting any pressure reach the actuator till the boost is close to the desired target, thus keeping the wastegate fully closed for as long as possible

the manual boost controller i'm using is one of these: http://www.skylinesaustralia.com/forums/go...ntr-t73375.html

other mods i have are:

apexi pod filter

silicone induction pipe

greddy fmic

3" full zorst

nistune ECU

etc etc

So yeah.. just wondering if it's worth me picking up an EBC or not... will i see the boost come on any earlier?

th_24thOctBoost.jpg

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https://www.sau.com.au/forums/topic/279128-rb25-turbo-on-rb20det/
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stormtrooper Proficient

stormtrooper

Posted
Posted (edited)
* i should clarify what i define as "wastegate creep" since i have heard other people define it differently: as the wastegate is a mechanical device, it begins to open slightly as the car comes onto boost. eg: rb20 actuator is 10psi for fully open, however when you're at 5psi the wastegate would be slightly open due to the pressure.. not enough to open fully but a little.

They're called "wastegate actuators". You can set the trim for the actuators, so you can have the car come on boost gradually or all of a sudden. EBC might be a good idea because you can set the trim on these to open the wastegate when you want it to, and usually don't open the gate until full pressure has been reached.

Edited by stormtrooper
Wogan Proficient

Wogan

Posted
  • Author
Posted

yeah the actuator controls the wastegate.. but the actuator on the rb20 is completely mechanical (no solenoid or anything) so i can't set the trim since i don't have an EBC (yet)

manual controllers try and reduce this creep by using a restriction on the hose to the actuator.. it does work in theory, but i'm wondering how effectively (if at all) my particular boost controller reduces this creep.

I'm mainly looking for other people running rb25 turbos on their rb20 to see at what rpm they reach full boost using which boost controller.

thanks!

bubba Grand Master

bubba

Posted
Posted

I was running a profecBII when I had my Rb20 w/25 turbo.. they have a fature that holds the gate shut until the boost level you choose, this helps bring boost on much faster.

I was also running a quality split dump pipe, 3" front pipe and 2.75" catback.

Wogan Proficient

Wogan

Posted
  • Author
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i'm just using a just-jap 3" dump / front pipe.. not great, but should still be good enough for my low-end horsepower ambitions..

I'm actually fitting an extractor style manifold soon as my current one is leaking and it was about the same price to buy a new one than to get this one fixed... maybe that will help slightly, but probably not enough.

I've also heard there are dodgey things you can do to reduce wastegate creep like using a long hose from the intake to the actuator.. but i don't think i'll be doing that

bubba Grand Master

bubba

Posted
Posted

Have you tried another actuator? I know the ebc will help bring on boost faster but there's still 1000rpm difference between when mine came on and what yours is doing.. that seems like a huge difference..

P.S. love the avatar dude, we have wooden floorboards and 5 cats.. mucho amusement :blink:

Wogan Proficient

Wogan

Posted
  • Author
Posted
Have you tried another actuator? I know the ebc will help bring on boost faster but there's still 1000rpm difference between when mine came on and what yours is doing.. that seems like a huge difference..

P.S. love the avatar dude, we have wooden floorboards and 5 cats.. mucho amusement :blink:

no i haven't.. that's probably a good idea.

I have tried 2 different turbos and 2 different dump pipes in my tuning adventures, but both turbos and both dump pipes gave identical results.

One thing i was considering trying was next time i get it on the dyno, disconnecting the actuator all together and giving it a run (obviously stopping as soon as the boost gets to 15psi) and seeing when it comes on boost completely un-wastegated .. should be a good indication of how much better it *could* be

Harry-Hotpants Collaborator

Harry-Hotpants

Posted
Posted

i had this problem when i first put an r34 turbo on my rb20, but i found out that it was due to the actuator, the wastgate actuator had a sort of power band, would mid boost then full boost, i was full boosting around 4500, all i did was swap over my rb20 actuator over and then that cut the rpm by about 1k

worrth a shot, altho be warned it may change ur boost setting, mine went up to standard boost 13psi

Tezzah Experienced

Tezzah

Posted
Posted
no i haven't.. that's probably a good idea.

I have tried 2 different turbos and 2 different dump pipes in my tuning adventures, but both turbos and both dump pipes gave identical results.

One thing i was considering trying was next time i get it on the dyno, disconnecting the actuator all together and giving it a run (obviously stopping as soon as the boost gets to 15psi) and seeing when it comes on boost completely un-wastegated .. should be a good indication of how much better it *could* be

I was going to suggest that and try it on the road.

just run it and watch the guage, but its not too safe :P

im thinking actuator is the culprit

astrotristan Grand Master

astrotristan

Posted
Posted

ive got a s2 r33 turbo on my 32 (rb20)

and i also have the boost tee and very similar mods to yours, minus nistune and plus splitfires,

my boost guage is unpluged atm (dont ask) so ill get that in this weekend and give it a smash :mellow:

however im pretty sure it comes on before 4500 bro

ill keep ya posted

R31 POWER Mentor

R31 POWER

Posted
Posted

Are you going off just your dyno graph or out on the street? I was looking at your previous dyno sheets and it looks like it ramps up quicker when you had lower power. Id say it's just a slower ramp rate on the dyno.

astrotristan Grand Master

astrotristan

Posted
Posted

hey mate just came back form a chill wiht some of the sau boys, and i took my car for a little burn wen on the freeway,

and anyway, althought my guage isnt plugged in atm - i rkn i hit full boost (12psi) at around 3,200-3,400

:banana:

endless Proficient

endless

Posted
Posted

Had a bit of test on the weekend and mine is making 10 pound by 4k and creeps to 12 pound a few hundred RPM afterward maybe 4.2k or thereabouts.

I'm using one of those GFB bleed valves. Sounds like i may have to find a stock RB20 actuator and swap it over?

daineisdabomb Collaborator

daineisdabomb

Posted
Posted

i put my old S2 rb25 turbo on my mates r32 not long ago. hits full boost (15psi) at 3200rpm in 4th starting at 2000rpm and flooring it. i would say take ur wastegate actuator off and test it with a compressor with a valve on it and gradually increase the pressure untill it opens the actuator. i think the spring inside urs if screwed and opening way too easily causing ur boost to come on slow. or ur wastegate isnt properly closed.

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