car wont boost over 9 psi

[dragracer08]

will your car boost 9 psi if there is a boost leak. reason im asking is some of the guys on here told me the reason i couldnt boost over 10 is because i have leaks, but i havent seen any yet. the screw on the lex is all the way out. i know that it is something simple, maybe some place im not looking for leaks

 

[mkiii222]

EDIT:

Just read your other posts. Check for boost leaks. It definitely sounds like a boost leak.

At 10 psi the system is under more pressure so more air will leak than at 9 psi which is probably why it's worse at 10 psi.

 

[Poodles]

You're giving us ZERO info. What mods?

 

[dragracer08]

will your car boost 9 psi if there is a boost leak. reason im asking is some of the guys on here told me the reason i couldnt boost over 10 is because i have leaks, but i havent seen any yet. the screw on the lex is all the way out. i know that it is something simple, maybe some place im not looking for leaks

sorry guys i have the 60 trim ct26, 550cc inj, lex afm w/ screw all the way out,255 walbro, 1.2mm head gasket, aeromotive afpr, 3 " exhaust , k&n fipk, and safc but havent installed it yet

 

[Poodles]

Hitting fuel cut, or just won't boost over 9psi?

 

[dragracer08]

sorry guys my internet has been down from a storm, but it seems that the car is fuel cut it goes full rich but it could be a leak, you guys are more experienced on this

 

[ogre]

very simple to do a boost leak test , take your snorkle pipe of your turbo , measure the inlet .
go to lowes
1. buy a pvc pipe cap with the same outer diameter
2. buy a coupler and 2 clamps
3. buy an air fitting for a air compressor
4. drill a hole in the cap and screw the air fitting in there
5. next adjust your air pressure on your compressor to 20 psi
6. connect the boost leak tester to you turbo
7. connect air to the fitting
8. listen to all the hissing of the air
9. feel around for where its leaking most likely crappy couplers , injector seal , throttle body seals , intake manifold gasket , stock i/c pipes , if you hear it but cant feel it or see it try taking some dish soap mixed with water in a squirt bottle and squirt things with it and look for bubbles.

 

[ben1984j]

sorry guys my internet has been down from a storm, but it seems that the car is fuel cut it goes full rich but it could be a leak, you guys are more experienced on this

Clear your codes, then go boosting and check them again. If you get a code 34 you're hitting fuel cut...

But you say "it goes full rich"...that sure doesn't sound like fuel cut to me; on the other hand I'm pretty sure a boost leak can make you run rich...

 

[Poodles]

On a 60-trim with lex/550 and no tuning, sounds about right to me...

 

[ben1984j]

On a 60-trim with lex/550 and no tuning, sounds about right to me...

Oh yeah, I didn't mean to say fuel cut wasn't a possibility, it threw me off cause I was thinking he meant "full rich" at max boost (the point where fuel cut would occur) which wouldn't make sense because fuel cut pulls, not adds fuel...so probably not what he was saying...

So, want to see if I've got this right: A larger turbo (with no tuning) will hit fuel cut sooner because it takes more airflow to spool up a larger turbo than a smaller turbo (to the same boost pressure), and airflow past the AFM is what determines fuel cut...is that correct or no?

 

[hvyman]

no fuel cut is when you have too much air than fuel. so it saves your engine from going full lean and blowing a hole in the piston. when you have a larger turbo you flow more air and hit fuel cut quicker. with the lex tho you can adjust it so you should be able to hit 17psi not prob with the upgraded ct.

 

[TurboStreetCar]

no fuel cut is when you have too much air than fuel. so it saves your engine from going full lean and blowing a hole in the piston. when you have a larger turbo you flow more air and hit fuel cut quicker. with the lex tho you can adjust it so you should be able to hit 17psi not prob with the upgraded ct.

No fuel cut is a safety margin programmed into the TCCS to protect in case of wastegate failure.

By the time you hit fuel cut, without tuning, the mixture will be rich enough for two engines.

Fuel cut is determined by a number of things, mainly AFM frequency (roughly 1500hz in my experience). MAF EFI setups use airflow to calculate boost pressure, when airflow is high it can pass the threshold of stock boost. The TCCS thinks there is a problem with the wastegate and shuts down the motor.

You either have a boost leak, or are at the limit of airflow for the stock EFI system.

Boost is only resistance to flow, temperature also plays a role in fuel cut. Larger turbo, less heat, more dense air, less resistance to flow because its less volume for same amount of mass flow.

Oh yeah, I didn't mean to say fuel cut wasn't a possibility, it threw me off cause I was thinking he meant "full rich" at max boost (the point where fuel cut would occur) which wouldn't make sense because fuel cut pulls, not adds fuel...so probably not what he was saying...

So, want to see if I've got this right: A larger turbo (with no tuning) will hit fuel cut sooner because it takes more airflow to spool up a larger turbo than a smaller turbo (to the same boost pressure), and airflow past the AFM is what determines fuel cut...is that correct or no?

The first part doesnt make sence, and neither does the second.

"Full rich" doesnt make sence and theres no point of full rich, Its not something you can "reach".

A larger turbo will hit fuel cut at a lower boost pressure becuase its moving more mass air flow at a lower pressure. Has nothing to do with spool up time.

To the OP, Check for leaks, and check for codes. Just to verify the condition, is the car shutting off while on boost? Or is the car running smoothly, just not boosting more then 9psi?

We need more information on what the car is doing then "i cant boost over 9psi".

 

[ben1984j]

no fuel cut is when you have too much air than fuel. so it saves your engine from going full lean and blowing a hole in the piston. when you have a larger turbo you flow more air and hit fuel cut quicker. with the lex tho you can adjust it so you should be able to hit 17psi not prob with the upgraded ct.

Right, but fuel cut doesn't happen at a certain air/fuel ratio, but rather at a certain level of airflow (measured by frequency, as nosechunks pointed out). The conditions for fuel cut to occur actually have nothing to do with the amount of fuel present.

"Full rich" doesnt make sence and theres no point of full rich, Its not something you can "reach".

"Full rich" was the OP's term, not mine I agree maybe "full rich" isn't a good choice of words, or correct, but I'm pretty sure he just means he's running rich in general (don't know what else that could mean).

A larger turbo will hit fuel cut at a lower boost pressure becuase its moving more mass air flow at a lower pressure. Has nothing to do with spool up time.

I never said anything about "spool up time"...when i said it would hit fuel cut sooner, I was talking in terms of boost... Like you said, it has to do with airflow - at a given boost pressure, a large turbo is moving more air than a small turbo. And to flip it around, if the same airflow goes through a large and a small turbo, it will generate less pressure (boost) in the large turbo. Because pressure = resistance to flow (as you stated above), and there is less resistance in the larger turbo. I don't think we're in disagreement...

Thanks for the responses both of you. Hopefully this will help in diagnosing the OP's problem...To the OP a little more info would be great, the answers to the questions nosechunks asked you are just what we need to know.

 

[dragracer08]

No fuel cut is a safety margin programmed into the TCCS to protect in case of wastegate failure.

By the time you hit fuel cut, without tuning, the mixture will be rich enough for two engines.

Fuel cut is determined by a number of things, mainly AFM frequency (roughly 1500hz in my experience). MAF EFI setups use airflow to calculate boost pressure, when airflow is high it can pass the threshold of stock boost. The TCCS thinks there is a problem with the wastegate and shuts down the motor.

You either have a boost leak, or are at the limit of airflow for the stock EFI system.

Boost is only resistance to flow, temperature also plays a role in fuel cut. Larger turbo, less heat, more dense air, less resistance to flow because its less volume for same amount of mass flow.



The first part doesnt make sence, and neither does the second.

"Full rich" doesnt make sence and theres no point of full rich, Its not something you can "reach".

A larger turbo will hit fuel cut at a lower boost pressure becuase its moving more mass air flow at a lower pressure. Has nothing to do with spool up time.

To the OP, Check for leaks, and check for codes. Just to verify the condition, is the car shutting off while on boost? Or is the car running smoothly, just not boosting more then 9psi?

We need more information on what the car is doing then "i cant boost over 9psi".

the car will smoke only when the throttle is to the floor,it tries to go over 10 you can tell that it wants too but then starts to doing the stutter, but as soon as i get a chance i'm looking for boost leaks thanks guys anything else you can think of let me know

 

[dragracer08]

No fuel cut is a safety margin programmed into the TCCS to protect in case of wastegate failure.

By the time you hit fuel cut, without tuning, the mixture will be rich enough for two engines.

Fuel cut is determined by a number of things, mainly AFM frequency (roughly 1500hz in my experience). MAF EFI setups use airflow to calculate boost pressure, when airflow is high it can pass the threshold of stock boost. The TCCS thinks there is a problem with the wastegate and shuts down the motor.

You either have a boost leak, or are at the limit of airflow for the stock EFI system.

Boost is only resistance to flow, temperature also plays a role in fuel cut. Larger turbo, less heat, more dense air, less resistance to flow because its less volume for same amount of mass flow.



The first part doesnt make sence, and neither does the second.

"Full rich" doesnt make sence and theres no point of full rich, Its not something you can "reach".

A larger turbo will hit fuel cut at a lower boost pressure becuase its moving more mass air flow at a lower pressure. Has nothing to do with spool up time.

To the OP, Check for leaks, and check for codes. Just to verify the condition, is the car shutting off while on boost? Or is the car running smoothly, just not boosting more then 9psi?

We need more information on what the car is doing then "i cant boost over 9psi".

no fuel cut is when you have too much air than fuel. so it saves your engine from going full lean and blowing a hole in the piston. when you have a larger turbo you flow more air and hit fuel cut quicker. with the lex tho you can adjust it so you should be able to hit 17psi not prob with the upgraded ct.

hey hvyman,i have the screw all the way out i know its something simple, i'm taking you guys advice on the boost leak stuff.

 

[TurboStreetCar]

the car will smoke only when the throttle is to the floor,it tries to go over 10 you can tell that it wants too but then starts to doing the stutter, but as soon as i get a chance i'm looking for boost leaks thanks guys anything else you can think of let me know

Smoke what color? Black, blue white? Again, starting the "stutter"? Is the engine shutting down? As in completely loosing power for about a full second? Or is it missing? Shuddering very rapidly? Does the engine light come on? Did you check for codes?

Check for codes to make sure your hitting fuel cut and not blowing out spark. Its not very likely to have spark blowout at that low of a load but you never know.

If your hitting fuel cut and you dont have any boost leaks then your at fuel cut and need to do other modifications to raise fuel cut.

Before you do any of these modifications do some research as it doesnt seem you have the best idea of whats going on.

 

[Fubar231]

The shutter really sounds like a boost leak to me. That was happening to me a few weeks ago, (Wouldnt boost over 10-11 psi and it would just flutter/bounce back and forth, tested my system with a home made boost leak tester and fixed it. Had numerous random lines that wernt on all the way, a few were cracked etc.

 

[MKIIINA]

"full rich" im betting hes looking at a NB output where it just goes all the way over to rich.

you have a boost leak. your afm is seeing alot of air, between the afm and the combustion chamber you are leaking it out, when the remaining air hits the chamber theres alot of fuel there to meet it and hence the smoke.

you need to pressurize the intake track and look for leaks. the charge pipe coming off the turbo going forward to the intercooler is a good suspect.

 

[Sprmcy]

well i might be having a similar problem. when under boost the turbo makes a loud whistling sound it has never done that before. its boosting around 8psi. could it be a boost leak or a malfunctioning turbo?

 

[zdatsupra]

very simple to do a boost leak test , take your snorkle pipe of your turbo , measure the inlet .
go to lowes
1. buy a pvc pipe cap with the same outer diameter
2. buy a coupler and 2 clamps
3. buy an air fitting for a air compressor
4. drill a hole in the cap and screw the air fitting in there
5. next adjust your air pressure on your compressor to 20 psi
6. connect the boost leak tester to you turbo
7. connect air to the fitting
8. listen to all the hissing of the air
9. feel around for where its leaking most likely crappy couplers , injector seal , throttle body seals , intake manifold gasket , stock i/c pipes , if you hear it but cant feel it or see it try taking some dish soap mixed with water in a squirt bottle and squirt things with it and look for bubbles.

I believe capping off the 3000 pipe where it enters the tb helps too, keeps the air from escaping into the manifold, cylinders and exhaust... otherwise its hard to build up any pressure and there will be a lot of irrelevant hissing, Right? am i missing something here?