Boost troubles...any advice would be great.

[Guest]

Hey There, I'm new to this forum but hoping someone can help me. I own a 1996 v2 wrx with a v2 sti motor in it. I have been experiencing boost troubles recently. I was running a top mount intercooler and under boost i noticed a slight "Cut" but thought nothing of it. Recently i had a front mount intercooler and 3inch down pipe off the turbo fitted to the car. The boost went from 12psi to 17psi with just those two modifications. Now when you give it gas at about 5rpm (8psi) the car cuts out and backfires (Sometimes a flame pops out the exhaust) 2nd, 3rd and 4th Gears it does that in 5th it goes to 4rpm (6psi) and cuts out. This has happened over time not straight after the intercooler was fitted. I recently had the car scanned and the knock sensor faulted so i replaced it with a genuine brand new one but still have the same boost cut, i also have tried 3 different air flow meters and still the same thing happens. A friend suggested over fueling but there is a good amount of fuel pressure and no lines seem to be blocked. I have hit a dead end on what it could be and its got my mechanic puzzled. Hopefully someone is able to help me. Oh and also going up hills when you give it gas it cuts out and in low revs it starts jolting.

[Guest]

All the hoses and clamps appear tight no leaks there as we had it a part today. My friends dad is a mechanic and he did the install for me.

[Swindog]

Is it hard to start from cold?

[Guest]

No trouble starting it when its cold, i normally turn the key wait for the fuel tank to fill then start it first pop, it idles at 2rpm when it first starts up then goes down to 1rpm.

[spark_38]

Welcome along!

.....awaits Rick's diagnosis.....

[Swindog]

 NOTN2U said:

No trouble starting it when its cold, i normally turn the key wait for the fuel tank to fill then start it first pop, it idles at 2rpm when it first starts up then goes down to 1rpm.

Wish my fuel tank filled up when i turned the key on, normally its the other way round!

I know what you mean.

So its obviously a load matter. I woulnt say its overfuelling I would say its chucking fuel due to something else.

No codes came up from the scan? Was the scan at a subaru dealership or just an obdii reader?

[Guest]

Just the knock sensor code faulted, it was a fancy 10grand scanner at a mechanic in Wellington and everything else seems to be running fine. Another thing i notice is it doesn't use fuel like its not thirsty on gas is this normal? LOL. I live 5mins from my work place so daily it doesn't really travel far for it to get warm enough, would this be bad for the car?

[Swindog]

 spark_38 said:

Welcome along!

.....awaits Rick's diagnosis.....

Did they reset the ecu afterwards do you know?

Could be a faulty afm or your boost solenoid possibly but Ichis the man and i dare say hell help you out when he pops in. In the mean time, try searching on here for the workshop manuals.

[Guest]

Yup they reset everything once the new sensor was fitted. I'm going to have a new air flow meter ordered in to rule out possibilities. I was also given from a friend a v4 sti boost solonoid so maybe that is causing my car to overboost and run like S***? I still have the factory solonoid here so will put that back in to rule that out. I was thinking of installing a boost controller at some stage, but with xmas approaching it will be hard to get my car looked at till after the new year. Thanks for your advice so far and i will try the afm and boost solonoid.

[spark_38]

Perhaps a boost tap to limit the boost in the meantime? I suspect with the overboost - it could be hitting map cut.

My old wagon does that too - doesn't like over 14psi boost spike, yet it's stock so dunno what's causing that. Perhaps the 321,000km's on the stock motor..

[kamineko]

i've owned a v2 and a large downpipe and free exhaust on a td05 is a recipe for hitting factory boost-cut. you could try finding a sti-ra ecu which has a higher boostcut but your still limited by the v2 map sensor and you'll still have the same problem. i don't know how a chipped ecu would react.

in my opinion, time for an EBC like a profec IIb or cheaper but less fun option is putting the factory downpipe back on. you will gain low end torque but it calms the top end down - benefit being stable boost at least.

if your confident your boost is stable below say 17psi then it may not be boostcut and i would look at your ignition system. check the condition of the coils, especially under the rubber caps - that might explain the unburned fuel having a party in your muffler ;p

[Guest]

I prefer not to run boost taps as i hear they spike really bad in Subaru's? I am in the process of buying a boost controller to bring the boost down until i can sort this boost cutting. The reason i put a down pipe on is cause i had so many problems with the factory one leaking a common problem also. I'm finding owning a V2 is really hard to maintain obviously the dud model of the wrx family lol. I did consider the ecu another option as my one is only restricted to 12.75psi. At the moment its gone from 17psi to 8psi and it just cuts at 8psi now. I will try everything you guys have all mentioned and let you know how i get on. Also another question if you run to much boost on a standard clutch does it cause them to go? I just hear of people's clutches slipping on dyno's and wondered if it was the same as running to much boost on a standard clutch. Just curious.

[Swindog]

 NOTN2U said:

I prefer not to run boost taps as i hear they spike really bad in Subaru's? I am in the process of buying a boost controller to bring the boost down until i can sort this boost cutting. The reason i put a down pipe on is cause i had so many problems with the factory one leaking a common problem also. I'm finding owning a V2 is really hard to maintain obviously the dud model of the wrx family lol. I did consider the ecu another option as my one is only restricted to 12.75psi. At the moment its gone from 17psi to 8psi and it just cuts at 8psi now. I will try everything you guys have all mentioned and let you know how i get on. Also another question if you run to much boost on a standard clutch does it cause them to go? I just hear of people's clutches slipping on dyno's and wondered if it was the same as running to much boost on a standard clutch. Just curious.

? Whose your soutce of info mate...sounds like they have some wrong info.

Boost taps work just as well on a subaru as they do any other turbo car. Cant comment on the down pipe though, never had one with a factory pipe on.

Negative on the clutch. Factory boost in my car is 17psi. Though it creates more power, it wont have a detremental effect on your clutch. If its a solid clutch or factory and in good nick youd have trouble pushing it beyond it limits.

[Guest]

Just have friends that always tell me stuff. I always get told so much different s*** i never know what to believe. A friend recommended coming on here and the info has been really helpful. Its my first turbo I've owned and I've built it from standard so just want to make sure i do it right.

[Mutsuraboshi]

 kamineko said:

if your confident your boost is stable below say 17psi then it may not be boostcut and i would look at your ignition system. check the condition of the coils, especially under the rubber caps - that might explain the unburned fuel having a party in your muffler ;p

I second this, check the coils and eliminate them from the equation.