GT4 ST185 Group A - Overboosting/Fuel cutting?

[The Red Baron]

Hi guys

I’m Dan, a new owner of a GT4 ST185 Group A unfortunately instead of out enjoying it I’ve got a problem. Also I’m rather limited in my knowledge.

Earlier in the week I took it for nice long test drive, was fantastic no troubles at all. Smooth, plenty of power.. it drove better than my previous rides Cordia GSR Turbo and SW20 N/A MR2.

Driving it last night in the cold and rain while accelerating I felt a jolt. This happened a number of times on the way home. If I drove it rather slow and changed before the Turbo hit the far right + gauge it seemed alright.

The car is standard apart from an 3 inch Aussie Down Pipe, and a manual Boost Controller.

From what I’ve searched on GT4 forums, people seem to be advising to turn down the Boost and either reset via Battery or EFI Fuse.

Any advice would be much appreciated as I’m inching to drive it.

Cheers!

[Cuts]

need more information mate.

what sort of jolt? only when giving it full beans? since you mentioned cold night could have hit a boost cut, what boost are you running?

[The Red Baron]

It feels at if it's rearing up, I get past around 3k revs turbo winds up but don't seem to be going anywhere. Just odd as a few days earlier was taking it to 5-6k each gear change no problems, smooth power delivery.. last night didn't seem to want to go above 3k and was running rather rough.

To be honest i'm not sure what boost it's running, car doesn't have a Boost Gauge. The previous owner did say he has tweaked it up a bit over standard.

[Cuts]

rearing up? does it miss?

not ideal running a boost controller when you dont have a boost guage.

when was it last serviced? is there any ecu light on? could now be in limp mode because of an overboost situation.

reset the ecu by either disconnecting the batt for 20-30 seconds or so or pull the ecu fuse for the same ammount of time.

[The Red Baron]

It had the same feeling as running out of fuel, but would only last for a moment and if I eased off seem to go back to normal within seconds.

I was a bit hesitant buying the car with a Boost Controller and no guage. It's done 135,000kms and next service is due at 138,000km.

There is no ecu light on, will that only be on if there is a fault? I've read a few times about people checking for fault codes.

Thanks. Is there a preferred method disconnecting batt or ecu fuse.. or much the same?

After it's done are there any other steps I should do? Sorry about all the questions!

[sainz]

sound like over boosting group a ecu has maps upto 17psi .
cold air boost spike hits fuel cut.
cuts the fuel for a moment and u loose power and sht yourself but it returns to normal after that.
dose this sound like what happens?
if so its your boost controller i bet it a ball and spring type if it is wind it in more so it holds more presure.
is it one of these.
http://cgi.ebay.com.au/Turbotech-man...ts_Accessories
just toss it and get a avcr .
just disconect battery one termial will do and leave it of for a 10min some say to be sure.
should twist off and on without undoing the nut.
if you need a boost gauge i have one for you there easy to fit.
also check all vac lines for leaks specifly the ones coming of y\the control to turbo.
hope this helps you.
welcome and post some pics in the gt4 thread

[jonathan yee]

? normally if it's just simple boost cut all you have to do is turn the ign off and on then you should be able to drive normally again(provided you don't over boost again)

have you driven it again since last night?

if it's still doing it (even after reseting the ecu and not over boosting)then it's possible the knock sensor has blown

[Fodder]

*nod* Still fine tuning my boost controller so I'm pretty familiar with fuel cut right now

Once it hits the cut (~12psi on my standard JDM GT4) it cuts power, and does so again any time I hit *any* boost until I've turned the ignition off and back on again. Also throws up the check engine light and stores the error code.

Error code will stay until it's cleared by disconnecting power for a while or pulling the EFI fuse for 30 seconds or so, but won't keep you in limp mode once you've restarted.

[The Red Baron]

Thanks guys appreciate the replies.

Sainz - yes that's exactly what it feels like. I was gutted when first happened.. then back to normal. It is a ball and spring type like your link.

Jonathan - I haven't driven it since last night, was a bit worried if it was doing damage and what was going on.

Fodder - I'm yet to get the check engine light, however the previous owner told me he had troubles with fuel cuts on cold mornings.. yet he said seemed fine on the way home from work at 5pm..

I'll be sure to try give it a wash and upload some pics over the weekend.

[CLG]

Yep, the manual "ball and spring" controllers are notorious for spiking in GT4's with a decent exhaust system. I have one in my ST205 and have had to wind it back in to basically standard boost to stop it spiking when driving aggresively. One day I'll throw it away and install the GReddy PRofec B unit I've had on my office shelf for the past 2-3 years - I don't get to drive it much, as you might be able to tell?!

[Fodder]

I've been using a ball and spring type for a few years - I was really happy with how it held boost for a while there. I set it up on a cold night to just below fuel cut, so on warmer days I got a bit less boost, but for value for money it was hard to beat.

Since changing to my newer setup it seems to spike a lot more - not sure if it's due to age (ie spring wearing out or something) or due to my new setup (the turbo I'm using now pushes more air around, maybe FMIC is more effected by cold air) but like Clint, I'm finding I can't set it a lot higher than stock without it occasionally spiking up to fuel cut.

Looking at going electronic soon I think, probably something like the Gizzmo MS-2 which incorporates a FCD in it.

Quick question: Does your engine light come on when you're starting the car up? Just to make sure the globe isn't blown

[The Red Baron]

Thanks guys, I filled up with BP Ultimate fuel, turned the Boost right down and reset the ECU.

Had a nice long drive tonight no problems at all. A bit smoother delivery of power, although lacks that sudden kick and turbo seemed to peak alot later in the rev range.

Cheers for the help!