fuel cut problem?

[jabbott126]

So i have been working on my new project 90 laser rs turbo. I got it a few weeks ago and it was in "working" order (the kid ghetto rigged alot of stuff). so tore her down and cleaned her up. I replaced the timing belt, and got new exhaust mainifold and turbo gaskets, i also took all of the intercooler piping out and intake for cleaning and inspection.

when we took off the exhaust housing for the turbo we broke a bolt off in it. I got a friend off mine at a turbo company to do an inspection on the turbo and to remove the bolt for me. when i got it back it was sorta messed up so he just gave me his housing. the problem was he had a diffrent wga on it then i had on mine and the boost level was set higher.

the car right now is all stock, expect a new clutch and a small 16g turbo. when i bought the car and drove it home it didnt have this problem with fuel cut.

I adjusted the wga arm last night to lower the boost. and it helped but im REALLY LOW BOOST now (at least it feels like low boost...i dont have a nice boost gauge yet) and its stil fuel cuttin at 5-6 rpms.

ALSO- the car had a boost controller that was broken siting in the back seat but the lines for the controller were hooked up still, and i took out my charcoal canister and there were some uncaped vacuum lines i left.

Im just trying to figure this out. im gonna get a controller and gauge this week and we r doing a boost leak test today.

so lmk what yuou guys think

 

[LiquidX]

Do a boost leak test (with soapy water), figure out the pressure required to actuate the wastegate, recirculate your BOV.

With the 16g, you do not want to be boosting more than 13 PSI so get an actual boost gauge. After 13PSI you begin to run the risk of 100% IDC (injector duty cycle) which is damaging.



Make sure you do all of your maintenance first including a full fluid change and the whole timing side replaced if you don't know when it was last done. Words from the PO don't mean squat unless there is paper work to back it up.

You'll want to get fuel mods since you now have a larger turbo than stock and that will entail to a pump, injectors, and a way to log and tune.

 

[jabbott126]

ok the ill do the boost leak test tonight...how do you use soapy water? and the bov is recirculated as of right now. Do you think i could use the old wga to solve the boost problem or do i need the whole housing for it (the old wga was not adjustable) and the old wga had a smaller whole to fit the arm on then the the adjustable one does

 

[LiquidX]

Use proper spelling, grammar, and punctuation when posting in our Tech Forums - don't use texting/instant messaging lingo here.


You fill up a spray bottle with water and dish soap. Pressurize the intake track and then proceed to spray everything down and look for bubbles. Anything that sees vacuum or positive pressure get's sprayed.

The BOV needs to stay recirculated unless you are using a GM MAF in blow through mode or are running on speed density. If you are not using either one then it has to stay recirculated.

Post a picture of the turbo with the actuator currently along with the housing. Also post one up of the old actuator.

It's possible the adjustable actuator is just not adjusted properly but a true MHI 16g is non adjustable. The eBay ones have the adjustable actuator.

 

[jabbott126]

ok will do!!! like i said my original wga arm was not adjustable. do the exhaust housing change from different sized turbos?

 

[jpLaserRs]

The turbo mite be too big for a stock fuel set up and is causing the fuel cut off, but you turned it down and still doing it?? Id say you have a boost leak some were check for dry rotted lines most common places are to the intake and recuirc line and also your sidemount the hose can be good but the sidemounts have a tendency to pit around the nipple were the hose goes to. good luck man hope you figure it out.

 

[jabbott126]

OK did boost leak test! i had a HUGE leak out of vacuum lines that i forgot to plug off at, and the leak is minimal now. So i took her for a drive and it fuel cut in 2nd... but later i took if for a drive and got through 1st, 2nd, 3rd, and then fuel cut in 4th at 5000rpms im still pretty confused on whats up

 

[jabbott126]

OK so i did some test runs today and it seems to be that i only hit fuel cut if im in full throttle it doesn't seem to have to do anything with my RPM's. If i stay at 60-70% throttle it wont fuel cut. ANY IDEAS???

 

[lou97gst]

have you installed anything to tune yet or no. Mine did the same untill i got it tuned now im back to fuel cut afc mest up and lost all settings. if that helps you out any

 

[LiquidX]

Once you boost a 16g to 14psi you will be at 100%+ IDC with the stock 450s.

 

[dsmtnr]

OK did boost leak test! i had a HUGE leak out of vacuum lines that i forgot to plug off at, and the leak is minimal now. So i took her for a drive and it fuel cut in 2nd... but later i took if for a drive and got through 1st, 2nd, 3rd, and then fuel cut in 4th at 5000rpms im still pretty confused on whats up

Fuel cut wont happen by RPM, it all depend on how much boost you are running and with what setup. I sounds like your car is fairly stock right now. I would make sure your wastegate is hook up properly and invest in a really good boost controller(I like the AEM Tru-boost myself), and gauge. lower you boost to around 11 - 13 psi and you should be good for the mean time.

 

[jabbott126]

So does that mena boost leak wouldnt even affect fuel cut?

 

[LiquidX]

Boost leaks can affect fuel cut along with running like crap. Think about it, when you start to boost, you have a strong vacuum coming in the intake pipe. More boost you run, the more vacuum. It all passes through the MAF and becomes metered air.

Once that metered air hits x amount then you will hit fuel cut to prevent damage. It will still happen even if you have a massive hole where all that air is leaving as there is not another sensor dealing with how much air is flowing to the motor.

If you have a boost leak, fix every single one and keep the boost down below 14 PSI.

 

[jabbott126]

so if i want to run above 14psi i will need bigger injectors, a bigger fuel pump, bigger fuel pump reg, and ill need to run a tune of some kind. ? what size and brands/types would you recommend if want to run 20-25lbs

I hooked up my boost gauge yesturday...it says im running from 10-15lbs. Would boost leak tell me an unacccuate answer?

 

[teamfallen]

boost leak will effect the gauge reading . if it dont hold the boost reading usally it is a boost leak

 

[jabbott126]

I checked for boost leak yesturday. nothing that i could hear leaking or see. but my gauge has been reading from 10-15psi. i think i just need a way to burn down my boost more or its time to do the fuel system upgrade (pump injectors regulator tune)

 

[LiquidX]

I checked for boost leak yesturday. nothing that i could hear leaking or see. but my gauge has been reading from 10-15psi. i think i just need a way to burn down my boost more or its time to do the fuel system upgrade (pump injectors regulator tune)

Do you hold pressure for at least a minute with the motor at 15*TDC (all valves closed)? If not then you have leaks some where.

 

[jpmxrider489]

you could try to get larger injectors

 

[lou97gst]

What is your goal to achieve hp wise to see what type of injectors to go for 255 is the usual fp

 

[jabbott126]

So i did another boost leak test today (correctly) im kinda stupid and didnt realize i had to watch to see if the system held pressure duh! but anyways we found a bad leak out of PCV valve and the BOV. Is there any better brand for PCV valves? also with HP goals... i looking at around 350hp and we will go from there

 

[lou97gst]

from what i know with what hp goal i wanted around the same as yours. I was told all suporting mods 1000cc injectors 255fp fpr dsm link wideband kit performance clutch fmic and make sure you have good compresion on the motor. check over everything make sure their is not anything worn out. Dont slap the fuel mods in untill you get the electronics in. because tunning is gonna be the key and its gonna run crappy with fuel mods and it not tuned 16g turbo and it should be good from what i was told.

 

[red_talon]

if you want decent power and dont want to waste alot of money, upgrade your fuel pump to evo or 3000gt, many members here sells fuel pumps. replace injectors with evo, or others that are 550cc or your choice. use a SAFC to correct the air flow. high boost will be ok at this point with the 16g turbo.

 

[1Illeagle]

i replaced a gutted 13g turbo with a big 16g..and it fried the piston ring on cylinder #1...so i take it that ill have to have bigger injectors as well? or will it just need tuning, or both?

 

[WES_393]

i replaced a gutted 13g turbo with a big 16g..and it fried the piston ring on cylinder #1...so i take it that ill have to have bigger injectors as well? or will it just need tuning, or both?

How much boost were you running? Any of the 16g's can be run at stock boost levels without fuel mods. Any higher and yes, you will need fuel pump, injectors, etc. But if the damage was localized to one cylinder and the others are fine, I would look at other causes of failure as well. Also, how was the ring fried? Did it seize in the ringlands, tear up the cylinders walls, melt, or what?

 

[1Illeagle]

id say around 14psi dont have an aftermarket boost guage...yet......as far as the piston goes im not sure, i havent tore it apart yet..im hoping it didnt mess up the cylinder walls, but i was planning on running it around 12lbs