Boost hits zero and thats it

[1cln91]

Ok put a manual boost controler on my car (91 tsi, all stock) and ran it at about 14-15 psi?, it was a lot faster of course but then i came to a stop light, took off hit 7grand shifted to second got up to about 5 and then started acting funny so i let off and shifted to third, it had no power and i looked at my boost gauge and it would go to zero and the stop boosting, took off the mbc and still did it, tested the wastegate, operted normaly, tested the wastegate selonoid, perfect, havn't done a boost leak test yet, but could it be boost leak, last time i had a boost leak it would hit 4-5 grand and pop and fall on it's face but its not doing that it just doesnt make any boost, what could be the problem, any help would be greatly appriciated.

 

[hybridb18]

make sure your waste gate is still connected to the turbo

 

[MrBoxx]

Check your turbo for shaft play, and as hybridb18 said, make sure the wastegate actuator arm is still attached to the wastegate flapper arm. If this falls off, you'll usually hit about 0 psi.

 

[viprez586]

The pop and falling on your face aka almost smashing your face into the steering wheel is fuel cut. Hit that little search button to read more about it. Anyway do a boost leak test, any little leak will make our cars run like crap. Chances are when you turned up the boost you blew a seal somewhere. The compressor cover, Compressor elbow, BOV flange, throttle body, and injector seals are great places to start looking. Best of luck man.

 

[Gregory]

Was it boosting above zero before the pop? Are you sure that you hooked up the boost controller correct? More times than you'd think, people hook them up backwards. Good luck.

 

[1cln91]

sorry about taking so long to reply been really busy trying to fix the car, it was the turbo, i guess when i rebuilt it i didnt get the shaft balanced right when i put it back together so it spun the bearings, but now i have another problem (i just cant get a break), i got a 16g turbo and new o2 housing with dump and put in a 190 lph walbro fuel pump, it stated cutting out about 6500 in first and gets worse through as the gears progess, so i did a boost leak test and found a couple but their was one more and i cant find it, it sounds like its comming from the mainifold, also i installed an auto meter a/f gauge, when it cuts out the gauge goes to lean instantly, is that definantly fuel cut or will a boost leak make the car do that to, thank for every ones help and again sorry it took so long to respond.

 

[Talesin]

You're getting fuel cut. Find and fix that boost leak. Also, A/F gauges are useless to tune from.. all they tell you is that your narrowband O2 is still cycling... in this case, yes, it confirmed that you're getting fuel cut. ECU cuts fuel = no fuel = completely lean.
A 16g will flow a lot more air than the 14b, and pull a lot harder. As a result, you'll run out the stock injectors a lot sooner, even without the boost leak contributing to your hitting fuel cut.

 

[1cln91]

Ok, so would a set of 550cc injectors and a 2g maf fix that, cause i can get those, but the apexi safc is a lot of money and i've read that if you use the two together you dont need the safc, is this true and also does the 16g spool up slower than the stock 14b

 

[schoffs4]

I have 550 fic injectors 18% bigger 2g mass air said to let 20% un metered air in . I have an afc and not had to use it to correct fuel trims . Wach out for WOT as you should run 2% lean I turned up my fpr to 40 and is pretty close still with no correction .Your ecu will correct for the 2% you need intill WOT. Thats my setup I'm using and its working for me till I want more and I do.

 

[1cln91]

im new to this so im not sure what that first part means exactly

 

[schoffs4]

Your stock injectors are 450cc 550cc are about 18% bigger and letting 18% more fuel that the ecu dosn't know about. 2g mass air is known to let 20% more air {fitted to a 1g] in that the ecu dosen't know about so 18% more fuel + 20% more air = 2% correction or lean that your ecu will compensate for except for WOT where it cant. You should get a logger or wideband I know there are pricey. I turned my fuel pressure regulator FPR to 40 and got good WOT readings on a wideband I hope that helps I type very slow sorry

 

[schoffs4]

Thats a good setup with no fuel managment but I recomend you get one as every car even with the exact same mods are tuned diffrently.

 

[1cln91]

ok now i understand that part, but what exactly is a wideband and a logger and where do i get themand how do i use them

 

[schoffs4]

A wideband 02 sensor [ oxygen sensor] reads Air fuel ratio. A logger lets you see and record engine data to let you know what the ecu [cars computer] is doing to manage fuel and timing, and give you information on steps you need to take based on the data. As far as where to get them just go to the dsm parts on this site and serch very easy.IF you serch forms on these items you'll find alot of info on how to use them and the readings you should expect. Tough to explain how to use them with out writing a book on it ,so much info on it. If you start with the info I gave you, you'll be fine with that setup intill you have some $ for more in the meantime search threds you will learn tons

 

[oldman]

Ok, so would a set of 550cc injectors and a 2g maf fix that, cause i can get those, but the apexi safc is a lot of money and i've read that if you use the two together you dont need the safc, is this true and also does the 16g spool up slower than the stock 14b

Hitting fuel cut has little to do with your ability to deliver fuel, stop being lazy and fix ALL your leaks.

I have 550 fic injectors 18% bigger 2g mass air said to let 20% un metered air in . I have an afc and not had to use it to correct fuel trims . Wach out for WOT as you should run 2% lean I turned up my fpr to 40 and is pretty close still with no correction .Your ecu will correct for the 2% you need intill WOT. Thats my setup I'm using and its working for me till I want more and I do.

That is absolutely not true, a 2G mas flows up to 33% more than its 1G counterpart, most will run lean without an AFC.

 

[Talesin]

Uh... no. Switching your MAF/injectors will not fix a boost leak. Fix the boost leak, and your fuel cut should go away at stock boost levels.

That said, switching to a 2G MAF and 550s is a good idea, and will allow you to run higher boost with less chance of hitting actual fuel cut. You CAN run with just the 2G MAF and 550s on a 1G, and pretty much run stock. It's not perfect, but it's in the close-enough range.
An SAFC (or better yet, DSMLink) will allow you to get a better tune and make more power, but that's down the road for you, from the sound of things.

 

[dsm-onster]

According to dsmchips,

At 1000 Hz:
1G MAS = 90 liters per second
GVR-4 MAS = 94 liters per second
2G MAS = 119.5 liters per second
3G #482 MAS = 150 liters per second
EVO 7/8 MAS = 150 liters per second

I suspect the actual curve of the tranfer funtion between the 1g maf and the 2g maf is not the same as well. If they are similar curve shapes, one can apply the same correction factor for fuel flow as airflow when they are swapped. The Dsmlink manual shows the correct way to correct fuel. Applying this to maf signal changed:

(old meter reading)
------------------------- - 1 = percent correction factor
(new meter reading)


90 liters per second
------------------------------ - 1 = -0.25
119.5 liters per second


Or -25% correction, not 33% correction.

See Converting Karman to AirFlow for the whole thread.

The question is can the ecu adjust the fuel trims for the -7% more correction neccesary for the 2g maf? Also, 7% correction = waht on a wideband. Stock ecus run up to 9.4:1 a/f ratio stock. Is this rich enough for WOT runs to be safe. I ssupect that you'll still see serious knock levels as the begining of the WOT curve on the 1g fuel map points to 11.5:1 or leaner but now you ahve to add the even MORE lean reading from the 2g maf. So you could be running at over 13.5:1 at WOT on spool up. This is not good with pump gas even w/ the biggest intercooler you can fit.

No swapping mafs w/out a logger and fuel control.

 

[oldman]

Or -25% correction, not 33% correction.

I wasn't talking correction , correction doesn't give you the % increase from the the old, it gives you the % decrease of the new.

119.5 - 90 / 90 = .328 = 33%.

Therefore,

1G maf flows 25% less than a 2G mas when 2G mas is used as base.

2G mas flows 33% more than a 1G maf when 1G maf is used as base.

a 2G mas flows up to 33% more than its 1G counterpart

 

[dsm-onster]

Ah! different points of view for the same signal: getting drinks thrown in mens faces for generations.

 

[1cln91]

im not trying to be "lazy", i know that the maf and injectors wont fix the boost leak im just trying to figure out what i need to buy to fix the fuel cut, i plan on fixing the boost leak as soon as i have a day or two off i can actually work on the car, but from the way talesin talks my fuel cut sould go away after i fix that boost leak scine i am running stock boost, so does this mean in dont need to worry about the injectors and the 2g maf and all those other thing that cost lots of money to make my be able to hit 7000rpm with out cutting out or am i completly miss understanding what im being told, go easy on me Oldman im new to this

 

[oldman]

Fuel cut is designed to guard against runaway boost due to a defective wastegate, what triggers fuel cut is not fuel starvation, it's a sudden drastic increase in air flow count that exceeds the pre-programed factory setting. The reason boost leak and fuel cut are often spoken in the same sentence is because boost leaks accounts for most fuel cuts by inflating the air flow count therefore triggering fuel cut even though you're running pig rich.

 

[1cln91]

So fix that last boost leak and the fuel cut should go away?

 

[oldman]

How do you know you only have one leak left? A leak test is not complete until you're able to hold higher than your actual boost level while taking no less than 30 seconds to bleed down to zero. How much pressure was shown on your boost gauge during your last boost leak test?

 

[1cln91]

i had one on my jipe one on my bov flange, and i could hear a really bad leak on the mainifold somewhere, i dont know what the gauge said because its leaking out so fast that i barely had enough time to spray soap water on all the possible leak points before the presure bleed out and i had to represureize the system, but i had my air compessor regulator set to about 15 to 20 psi so im guessing thats what my boost gauge would have read.

 

[oldman]

i had one on my jipe one on my bov flange, and i could hear a really bad leak on the mainifold somewhere, i dont know what the gauge said because its leaking out so fast that i barely had enough time to spray soap water on all the possible leak points before the presure bleed out and i had to represureize the system, but i had my air compessor regulator set to about 15 to 20 psi so im guessing thats what my boost gauge would have read.

You would think so! Have a friend read your boost gauge next time, I suspect it's barely registering anything if it's leaking out that fast.