Boost Cut -- GRRRR! - Perth-WRX.com

Jim621 · #1 14-03-2009, 10:45 AM

Hey guys,

well the other week at the drags i was getting boost cut down the 1/4 mile strip. it was a cool night and i thought nothing of it.

during the week i cleaned and oiled my APS in-guard airfilter, and now i get boost cut in all gears whenever i floor it! (i run a link ECU, so dont need to worry about the AFM failing)

i did some data logging today, and im hitting the boost cut of 250kPa (23PSI)
which is a little scary on the std EJ205...
the car should be running 220kPa (18PSI)

I got a tune from ASG about a month ago,

SO does the car need another tune and more dyno time? or is it just a simple adjustment of the wastegate settings? (which i could do myself if i knew what to adjust)

Cheers, Steve.

teejay · #2 16-03-2009, 02:06 PM

Is it running a boost controller?

If it was tuned on 18 and has changed since, somethings not right. It doesnt need a tune, but you need to source the reason its making 5 more psi then it was tuned at.

I doubt your hitting boost cut, since the link wouldnt have one I dont think. More then likely stuttering from lack of fuel....

Jim621 · #3 16-03-2009, 02:15 PM

THanks for the reply Teejay,

No boost controller.

Yes, it IS hitting the 23PSI boost cut, i did the data logging with my laptop and it defintely hit 252kpa, and it did completely cut the power for half a second.
Yeah the link has a boost cut....

Maybe the MAP sensor is playing up???
My $50 'supercheap' boost gauge is showing it hitting over 20PSI, so the odds are it IS hitting the boost cut.

according to the setting on the ECU its tuned for 18PSI.

it all got worse after i cleaned the airfilter.
maybe it wasnt tuned properly because the airfilter was limiting the max boost it could develop??

Cheers, Steve.

teejay · #4 16-03-2009, 02:22 PM

Nah a little bit of dirt isnt going to cause a turbo to spike 5psi.

Id be looking for an air leak somewhere or a loose line off the turbo etc. Like I said if you had a boost controller check the lines on that too.

And its good to know it has a boost cut, helps. But if its been tuned for 18 and your hitting 23, you cant be sure the tune will be safe for your motor at that boost.

Probably a good idea to treat it as an urgent matter.

Jim621 · #5 16-03-2009, 02:33 PM

Thanks mate.

Yeah, i havent driven it since i did the data logging.

i checked the hoses to the turbo over the weekend - i couldnt find anything out of place.
ill have to closely inspect for cracked hoses...

its just weird how it got worse after i cleaned the airfilter....

ill give ASG a buzz when i get a minute alone at work.

Cheers, Steve.

Jim621 · #6 18-03-2009, 11:50 AM

So i checked over the hoses to and from the wastegate again, made some small adjustments for things that could be an issue, but the boost spiking remains.

My theory on what has happened is;
during the tune, the dirty airfilter was limiting the amount of air passing into the engine and limiting the boost the turbo could produce.
after cleaning the airfilter, the tune settings for the wastegate now arent dialed in as they should be, so im getting a boost spike.

Sound plausible?

Does anyone have a manual for a 99 wrx, that describes how to test if the MAP sensor, Wastegate solenoid etc etc are working?

Thanks, Steven.

Elrico · #7 18-03-2009, 04:38 PM

Could it be a faulty wastegate actuator? Or would that only limit boost rather then create excessive boost?

Maybe more air can get passed the clean filter and so it has more pressure and reaches boost quicker making the actuator force open further than it should?

Avalanche · #8 20-03-2009, 12:21 PM

i had a similar problem is it a g4? do u have anti lag on?

Jim621 · #9 20-03-2009, 04:22 PM

Hey people,

Fixed it!

nah, its a possum link ECU - oldschool.....and no, dont have antilag.

it was the settings that were wrong.

i did some road tuning to find the problem, i set the wastegate solenoid (WGBase) to 0% duty cycle (ie to run stock boost of 13.5PSI or whatever)

the boost was spiking to ~18 then dropping to 13 to redline...so i knew it wasnt a mechnical leak or whatever..
then adjusted the wastegate sensitivity to the stock setting of 5, and stared to increase the wastegate base to a level where the car had boost, but didnt overshoot.

so all sorted and didnt cost me a cent

cheers guys, Steve.

Avalanche · #10 20-03-2009, 04:39 PM

glad to hear mate