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Overboosting - car not holding boost

YOYO

By YOYO,
in Engines & Forced Induction

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YOYO Contributor

YOYO

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Hey there fellas. I currently own a 180sx fitted with a Greddy Profec A EBC. Immediately after fitting a boost gauge (now a while back), I saw that the needle regularly reached 16psi. This was quite alarming as the EBC was only set to 7psi (stock). After I noticed this, I verified that the boost gauge was working properly and was not faulty, by verifying that the EBC readout also reached 1.0 bar (14psi or thereabouts) as well.

First question; why is the car not holding boost around 7psi as it should? I have a feeling that either the solenoid or the actuator is stuffed. Are these problems common or unheard of? Which brings me to a third question; if the actuator needs to be replaced, is it possible to purchase and fit an actuator separately? Or do I need to replace the whole turbo assembly?

I'm starting to get a bit freaked out that my turbo or engine is going to suddenly explode, so your help is greatly appreciated.

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NJR 34GTT Proficient

NJR 34GTT

Posted
Posted

Noticed a similar thing with my 34. It has a Greddy Profec EBC and hand controller(hand controller not hooked up though). The boost is set to around 13-14 psi at max but i regularly see it hit 16psi with the very cold mornings we experience here in Canberra.

I thought an EBC was not supposed to allow this to happen?

rb25 Grand Master

rb25

Posted
Posted
Make sure you have completely removed the factory solenoid...

Make sure the EBC is connected properly, and there isnt any leaks.  

If so, it should hold boost fine, ive got an avcr, and the worst it ever spikes is 1 psi

:werd: sounds like the solenoid isnt set up right. 2psi spike? damn, the worst my hks evc spikes is 0.02bar (0.3psi)

YOYO Contributor

YOYO

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Everything is set up right, no leaks in hoses and the factory solenoid has been removed completely. The boost is spiking to more than double what it is set to, this is what's scaring me. If it was only 0.1 bar or 1 to 2 psi it would be OK but double the boost says something is definitely wrong.

The only other option I can think of at the moment is to purchase or lease another profec A solenoid to see whether that works or not.

Trust33 Grand Master

Trust33

Posted
Posted

YOYO

It could be that your gain,set gain and set boost are set to high.If these are to high then you will run into overboosting problems.

I dont know how different the profec A is but it should be simpiler to tune.I use a Profec b spec 2 ebc and it was spiking also.

Run it turned off with the controller hooked up and see if the car does the same.

And also try to keep your hose length to a minimum.Have the boost controller located in a cool area of the engine bay not right next to the motor.

Remember start at zero and work your way up.

YOYO Contributor

YOYO

Posted
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Trust33 -> I'll have to check those knobs you mentioned. What do the ratio/time/offset knobs actually do? I have these three little knobs to the right of the main boost setting but haven't touched them since purchasing the car.

BTW, I've already tried turning the controller off and it still overboosts, so it's not the EBC's fault.

Low25 -> Yes, the profec A does have an OverTake Boost (O.T.B) button but i don't know how much it increases boost by, it lasts around 10 secs though.

Trust33 Grand Master

Trust33

Posted
Posted

The solenoid wants to reach the set boost but it cant cause uve set it to high. Couple that with a small ass exhaust housing and wastegate that cant handle the exhaust gas flow from the engine and the solenoid wants it to achive all this when it cant cause its SET TO HIGH SO BRING IT BACK TO ZERO.

The unit only reads what you set it to.

YOYO Contributor

YOYO

Posted
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Trust33 -> Umm, I've only set it to stock, can't get any lower. I've also tried setting the boost to zero but that didn't work either, the car still overboosts.

rb25 -> I've checked all lines and they are all ok, the controller came as is, installed with the car.

I have a feeling it could be on a different high boost setting, I'm going to check this out tomorrow.

Trust33 Grand Master

Trust33

Posted
Posted

Id suggest that you get a users manual from somewhere.

If you cant find your problem,then you should assume that its your solenoid.

Here you go i may be able to help you.heres a link to a blokes site where he has installed a profec a on his rotary.The diagram shows the points at which the boost controller should be connected.And it is for an internaly actuated wastegate like the one youve got.

http://www.scuderiaciriani.com/rx7/profec_install.html

This is the main page (appendix) to it.

http://64.233.167.104/search?q=cache:cbHl-...df+format&hl=en

This one also has the power fc,avcr and a heap of other manuals and wiring diagrams for peeps to download.

Kaido_RR Grand Master

Kaido_RR

Posted
Posted

YOYO;

I currently run a Profec A ebc on my r33, have u done the learning mode so that the ebc can learn ur turbo cruve, i was lucky and bought mine off someone how had it on a r33 so it was already set to a stock turbo, so i get no overboosting.

Try to do the learning mode or get it tune by a workshop

YOYO Contributor

YOYO

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  • Author
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I got the manual checked out the settings. Low boost is 5bar and high is 7bar.

Today I took it for a good fang and got the car up to 18psi in 5th!!! Needless to say, I let go of the accelerator pretty quick after that!

13_devil -> how did you get the EBC into learning mode? I've got the downloaded manual, but it doesn't say how.

YOYO Contributor

YOYO

Posted
  • Author
Posted

Well guys got it fixed yesterday (Thanks Faeez, you're a f**king legend!). We played around with the hoses a bit and checked that the actuator opened up the wastegate using a bicycle pump. As it turns out, the piping coming off the intercooler charge pipe to the solenoid had an air filter that was leaking.

Now that it's fixed, the car feels a LOT slower; 7psi is nothing compared to 18!!! Oh, and I don't have an excuse to upgrade my turbo :rofl:

Anyways, thanks for your suggestions ppl.

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