Boost Creep

[13thracer]

ok im still battling away with my boost creep problem for staters i have an rb25 series one with a series two turbo, FMIC, bosch 044, malpasii fuel reg, full three inch exhaust i have a dump pipe its the replacement style elbow you can buy of ebay which goes into a custom 3 inch front pipe, using an rb20 wastegate acuator, pod filter, no bleed valve or EBC just striaght to hose to wastegate, and also what i think is my problem a set of hks cams not exactly sure on specs but im pretty sure there to 256/264 ones and stock ECU i have an SAFC but it isnt tuned yet. Now for my problem, i can get it to hold boost of 10psi under heavy load or about 75% throttle in any gear but if i try full throttle it holds for a split second then creeps up to the point rich and retard (about 14psi) kicks in and dies in the arse and i let the throttle off. also if i am nailing it on about 75% throttle it will go all the way to redline on ten psi happily but if i hold it there then push the pedal to the floor it creeps it just doesnt like full throttle.

things i have tried:

the dump pipe (as above)

the old rb25 acutuator 7psi

new 3 inch cat

new muffler only have one on the system

bleed valve GFB atomic

and finally i have taken the turbo off and ported out the wastegate hole and cleaned up the entry and exit have not enlarged the flapper though.

havent tried an ebc i cant see how it would help as it cant even hold a small 7psi with the old wastegate

does not have the stock boost control solenoid engine in a s13 now

have swapped hoses, and checked for any boost leaks all fine in that department

i have wathced the SAFC and aiflow meter is maxing out whch is causing the R&R i know the SAFC should iron out the low end of the rev range maxing out but i dont like the idea of it climbing to 14psi and beyond on a cold night.

On a hot day after rich and retard kicks in for a little if i hold it flat it does come back dpwn to about 12 or 13psi and holds steady there so the 14psi on a cold night really hurts the stock ecu. my theory is that the cams are flowing more gas than wastegate hole can cope with so it ends up going through the turbine, if so what are my options.

if you have actually read all this thankyou for listening and any help would be greatly appreciated i dont care how dumb the idea is you have spit it out it may work for me thankyou

[cameron]

This is the second RB25 i have ever seen do this. We have tried everything aswel, even new HKS turbo, still creeps!

1st thing would be to get a aftermarket ECU so you dont have the fuel cut happening... and new AFM.

Z32 & FC would be fine.

Try disconecting the wastegate arm off the flap and leave it wide open, 1 would think that it would make no more than 7psi at 7,000rpm. We also tried this and got 15psi???

Creep starts to happen always at around 4,500 - 5,500 rpm, and keeps making boost like a super charger.

I would like to know the answer to you question aswel.

[13thracer]

woo hoo im not alone i have tried disconnecting the arm and wiring it open i still get the creep. i have looked into the power fc but the problem being it will still creep and not cut out which is fine but the standard turbo will throw itself apart. the next item on my todo list is a decent batmbl dump pipe then after that i have seen a t3 to t3 flange with a external gate adapter on it so you can run standard everything with an external gate which is bigger. looks like i would only have to extend my lines alittle which i can do and then get the screamer plumbed back in. if you had the dollars you could buy a whole new manifold and external gate setup with new lines and stuff as the only ones i have seen are high mount which is a pain to swap over when you want to keep the stock look. your description of your boost creep is just like mine.

and by the way are you runnning bigger cams by any chance?

[R31Nismoid]

I wouldnt be running cams if i was using an S-AFC, you might aswell go the full hog and get a FULL ECU in there to actually make use of the cams, the S-AFC really doesnt do you much justice to be honest.

I say, drop the exhaust from the dump pipe and then see what happens

And you dont NEED an external gate, you have another problem which you can only fix by trial and error dude.

And EXT GATE is not the answer, especially on a stock turbo.

I have a feeling that the above (dropping exhaust) still might not fix it, and what you have is the good ole e-bay special dump is not letting the int gate open fully.

Hence it will bypass some air, but once your on WOT (Wide open throttle), its simply unable to bypass enough and is spiking

[paulr33]

im not sure there's some 'phantom' problem here.

i think its all normal, and operating as its supposed to.

you've changed the r32 actuator and youve done exhaust upgrades. the r32 actuator is rated at 0.85kcm2 which is 12psi. the stock ecu has a ramp for "excess airflow protection" and its a scale that ramps up, as rpm and load increases. its not an exact cut based but a sliding scale. 12psi is certainly enough to activate it under most conditions.

i can't see a reason why it would happen using the stock r33 actuator, did you confirm a max boost of 7.2psi when using the stock 33 actuator?

my advice would be just get a real ecu, you would benefit from more average power everywhere once tuned and setup properly

[13thracer]

paul i know what your saying about the sliding scale once it jumps outside of its map it does hit R&R (particularly with the cams its sucking in alot more air than usual) because depending on how hot or cold the weather is i hit it all across the rev range some times if i nail it 1st it just dies right down. i did check the that it holds 7psi under load it did but WOT it creeped up the same wih the r32 actuator holds ten fine the creeps when i stand on it. i really would love a power fc but dont have the dollars to buy and get it tuned the SAFC will serve its purpose for now, ill be happy just to have it running right for now, power fc will be coming down the track

at risk of soundling like a tool, why wont a ext gate fix the creep/spike its bigger and will flow out the gas i need to flow.

i cant see the neighbourhood being a big fan of me test driving straight out the dump either wow that would be loud but it has be to done.

[paulr33]

have you checked the actuator and flap for movement and play?

the service manual show you how to check and test this.

it sounds like its not opening correctly or not enough.

there should be no logical reason an r33 actuator would spike to 12psi if its working correctly and has nothing intercepting the signal.

where is the signal coming from ?

[13thracer]

forgot to add fitting a power fc and tuning it would be great but i would still have the boost creep and my std turbo dont like 15psi i dont care that im hitting rich and retard i knida expect it with this setup, i just want to stop the overboosting then i will deal with the R&R.

Sorry if that sounded like i was having a go at you i wasnt, i really appreciate your help its good having more ideas thrown at me it gets me thinking about what i can do to fix it.

[paulr33]

its cool, just seems like an odd problem to have. something doesn't add up or we are missing some info. where is the actuator signal coming from ?

[13thracer]

off the intercooler pipe about a foot from the compressor i put it nice and close, the flapper does have movement in it with the wastegate arm off you can move it up and down a little,i tried this on mates skylines and they have no movement

[paulr33]

do you have an air compressor?

the manual states to pump in 7.2psi for the stock 33 actuator

you should see shaft movement

[13thracer]

yeah i tested the old actuator at work when i swaped them over didnt have a pressure guage on it but was moving freely with light amout of air shot into it

[R31 POWER]

Im guessing it's one of those "XS power" split dumps? If so i had a problem with the flapper valve fowling inside on it. I chopped the poxy wastegate pipe off and welded a 2 inch pipe It's all good now!

[13thracer]

yep thats the one not xs power but looks like it, looking into getting a batmbl dump or ces if not the chop and weld might be on the cards

[R31 POWER]

Thought so. They LOOK like a hks dump but are'nt. Farking shit i say. I'm keen for one of those batmbl dump/front pipe's also.

[paulr33]

ive got a batmbl split dump and no problems at all.

with controller in off mode it stays on the actuator spring rate

with controller on it stays on 0.85 bar no worries, doesnt spike or vary.

thats using a hks evc3 the older style one

[Turbinator]

A friend is having this problem on his R33, he has a Batmbl dump pipe and a GCG high flow.. We haven't tried any other actuators. There is a separator that extends between the dump and exhaust gasses on his Batmbl dump. I thought the wastegate flapper might be fowling on it.. Do you have the separator on yours PaulR33 (or others)?

Perhaps GCG replaced the wastegate flap with a larger one and it is fowling? We have a compressor and will drop the dump off and check things next weekend. I'll keep you updated..

[paulr33]

yeah my batmbl split dump has a seperate pipe for the gate outlet

and a divider between the gate and exhaust wheel

[13thracer]

dont say that i was thinking a bigger dump pipe might fix it, im thiinking about putting on an external wastegate, if i cant get the gas i need out an external gate im pretty sure im stuffed.

[paulr33]

just get a real dump pipe

problem solved

sell the old one on ebay for $100