Why do I lag so bad?

[jdurston]

Just wanted to get your guys opinion my situation. My turbo takes forever to build boost. I don't hit 10psi until about 5000rpm and then I hit fuel cut at about 6000rpm. I properly installed a MBC and have it set to the minimum. I tried cranking it up and can't really get more than 11psi out of it, but have left it turned down for now till I get this sorted out.

I just did a leak test of my intake as per VFAQ.com. I did find a minor leak on the intercooler output hose connection. When I pressures the system to about 15psi it would leak down at about 1psi per sec. I think that even with this small leak it should be pressurizing far faster, closer to 3k rpm not 5Krpm.

I did recently fail my emissions test on carbon monoxide.
Could my catalytic convertor be plugged and causing a ton of lag?

Do the wastegates get stuck open a crack ever wrecking low rpm response? the wastegate moves freely if I disconnect the actuator arm, but is solidly held shut if attached. My turbo does not have any shaftplay.

Is my turbo possibly poached?

How much of an effect does my small leak have? The fuel cut makes it seem like I have some huge leak.

I even tried backing out the maf adjustment screw to get rid of the fuel cut but it did not work.

The car idles fine and seems to run fine off boost. But my boost experience is just not what it should be.

Is it possibly that I have a cracked manifold or exhaust housing?

Any tips or things to look for would be appreciated.


Thanks

Josh

 

[xcelr8n]

massive exhuast leaks?
either cracked manifold etc....
a massive leak before the o2 sensor will mess up fuel trims, I'm dealing with the same issues...

 

[ltho98]

Just wanted to get your guys opinion my situation. My turbo takes forever to build boost. I don't hit 10psi until about 5000rpm and then I hit fuel cut at about 6000rpm. I properly installed a MBC and have it set to the minimum. I tried cranking it up and can't really get more than 11psi out of it, but have left it turned down for now till I get this sorted out.

I just did a leak test of my intake as per VFAQ.com. I did find a minor leak on the intercooler output hose connection. When I pressures the system to about 15psi it would leak down at about 1psi per sec. I think that even with this small leak it should be pressurizing far faster, closer to 3k rpm not 5Krpm.

I did recently fail my emissions test on carbon monoxide.
Could my catalytic convertor be plugged and causing a ton of lag?

Do the wastegates get stuck open a crack ever wrecking low rpm response? the wastegate moves freely if I disconnect the actuator arm, but is solidly held shut if attached. My turbo does not have any shaftplay.

Is my turbo possibly poached?

How much of an effect does my small leak have? The fuel cut makes it seem like I have some huge leak.

If you are hitting fuel cut, it makes me think that there is some massive boost leak somewhere that is causing the car to boost up slowly, but you're still flowing more soo.. BAM fuel cut at low boost levels.

However, if you failed your emissions tests on CO, it could also be due to a clogged cat, which could also cause poor boost response.

Your wastegate is normal and the turbo seems to be ok if there is no shaft play.

Usual problems that cause to boost developing problems.

Pre-turbo exhaust leak: manifold to head or manifold to turbo
Post turbo exhaust restriction: Clogged cat
Too rich of an AFR can cause boost to develop super slow
Wastegate opening prematurely due to too large of a gate or too weak of a spring
Boost leaks (of course)
Seizing turbo cartridge (rare)

 

[FastEclipseGSXT]

My buddy had the same problem and it turned out being an exhaust leak...we tightened all the bolts on the turbo, manifold ex, and 02, car pulls great now..

 

[jdurston]

I bought the car from a car who didn't tell me a lot things. I think I must have a problem in my exhaust system and intake. It seems weird to me that I would hit fuel cut so easy off of such a small leak when tested (about 1 psi per second @15psi).

The only way to hit fuel cut at a low boost is a major leak, correct? Last night I was looking at my fuel cut problem. The stock boost gauge is a about .75 when I hit cut. It then maxs out past 1 after cut. My autometer gauge is climbs to about 11 psi till until fuel cut, then it drops drastically. Why would the stock gauge spike after fuel cut and not before if it is essentially an air flow gauge not a boost gauge.

I would feel better having seen the turbo and manifold for myself, by taking it off and inspecting it. Is it a big deal? Will any cracks or leaks be obvious?

Thanks for the input,

Josh

 

[69_luv]

Jus thought I would throw this in for you....

I couldn't get more than 12psi, and hit hard fuel cut at 4k. Pressure test came out ok, and system held 30+ psi.

Problem came to be the fuel pump oring had cracked, and was allowing the car to run proper boost but hit fuel cut at 4k. If you have a chance to hook up to a wideband, my car hit 17-1 at 4k, thats supper lean.

 

[jdurston]

Fuel pump oring?
Was this oring at the pump in a connection on the fuel line?
My buddy has a wide band maybe I can convince him to weld a bung onto my exhaust.
Josh

 

[69_luv]

My fuel pump was not seated properly into the part where it goes into the fuel line. The oring was all messed up, it allowed the car to run up to 4k but after that it would choke, sput and backfire.

As for the wideband, you DON"T NEED to weld a bung, just use the rear O2, plug the wideband in and run the cord safely under the car. That is what Pina did for me and it worked just fine. You don't need the downstream O2, so just pull it out and plug the wideband in.

If you have done a boost leak check and your holding pressure, you can check your wastegate. But if your hitting fuel cut, does it happen before 6k? It took a lot of hours to find that damn Oring on my fuel pump, but you should be generating boost a lot earlier.

Good luck

 

[jdurston]

Found out why, I lag.

Don't used cars rock!? I just bought this car the owner didn't say anything about this.

 

[xcelr8n]

told ya
my exhuast manifold looks just like that, but only one is snapped....

 

[jdurston]

Will I damage the cylinder head if I con't to drive with the broken studs and resulting exhaust leak? My fuel mileage is terrible, wondering if it messing with the O2 sensor.

Josh

 

[xcelr8n]

damage to the cylinder head dont think so....
youre gonna run friggin rich all the time though, hence youre gas mileage....
yes it is jacking with youre o2 sensor therefore youre fuel trims....

 

[jdurston]

Thanks, thats a relief I have to drive the car to college everyday this week.

One of the studs is broken off almost inside the cylinder head.
Should I drill it out very carefully or is there a better way to remove it?
What about "Easy outs", or various bolt remover tools. I don't want to make it any worse by buggering up the hole.

I know I'll probably have to use a helicoil to repair the hole.

-Josh

 

[realhp=turbo]

Trick is that its a steel stud in an aluminium hole. heat the shit out of it, squit with penitrating oil, and attempt to turn the screw out with a very hardened piece of steel and a hammer. good luck but if you screww up wile trying to drill it out youll oblong the hole and screw the entire head up.
mike