Boost Build Up But No Power

[The_one]

Hi DSM Tuners,
I have a problem related to boost and power output that i need some assitances with. Whenever, i drive My 95 AWD TSI i can hear, feel, and see the boost is building up by the Turbo (small 16g). But for some odd reasons the engine can not obtain that boost from the turbo. I drove my brother stock 97 gst and i could feel his car has more power output than mine. His turbo build up boost faster than mine too

Things i did/checked:

1. Boost Leak Test (Leaks Fixed with Silicon RTV)
2. Compression Test (Good, 130psi on all 4 cylinders)
3.


If anyone knows how to diagnose this problem. Feel free to post


Thank You Very Much

Vu

 

[missionx96x]

did you check your TB and intake manifold? BOV? anything between the turbo and intake manifold. double check everything. if you can hear your turbo spooling and you kno its making boost then it must be leaking out somewhere.

 

[kenamond]

1. Boost Leak Test (Leaks Fixed with Silicon RTV)
2. Compression Test (Good, 130psi on all 4 cylinders)

First, what were the results of your boost leak test? You pressurized to 20psi and it held how well?

Second, your profile says stock internals, and on a 2g, the service limit for compression is 133psi (178psi is perfect). All 4 cylinders are below 133. Did you do the compression test on a warm motor (you should)?

I recommend first doing a compression test with the motor warmed up. Then do a wet compression test and see if the numbers go up a lot. After doing a proper compression test, if you still see low compression, signs of ring wear (read that compression test page), or pressure differentials of more than 15psi between any two cylinders, I recommend having a leakdown test done. Here is a description.
Post the detailed results of your boost leak test. You can fix some boost leaks with RTV, but there are other leaks you cannot (or should not) such as injector insulators and bad PCV valve, so I'm not convinced you fixed all of the boost leaks.

We can go from there.

 

[v2ner]

1) are you hearing spool up and the BOV?
2) are the RPMs jumping when you step on it?

 

[TimG]

130 compression on a stock 2G 7-bolt motor is not good. Either way, you should still make some good power. Try something as simple as changins your spark plugs. It's cheap (under $15) and you'll be doing the car a favor in the long run.

 

[JayRolla]

Yea kenamond is right. Your compression is real low. I had 180 on all 4 pistons when I upgraded to 2g pistons in my 6 bolt. This could be making you lose power.

 

[The_one]

did you check your TB and intake manifold? BOV? anything between the turbo and intake manifold. double check everything. if you can hear your turbo spooling and you kno its making boost then it must be leaking out somewhere.

I am able to hear my turbo spool when i rev it. When i did the Boost Leak test I only presurized the turbo up to 10 psi. I don't know that amount is low or hight ?

 

[JayRolla]

You want to pressurize the motor to what ever boost levels you will most likely run one day. I test mine up to 22psi. You pressurize it to at least 20 psi

 

[The_one]

First, what were the results of your boost leak test? You pressurized to 20psi and it held how well?

Second, your profile says stock internals, and on a 2g, the service limit for compression is 133psi (178psi is perfect). All 4 cylinders are below 133. Did you do the compression test on a warm motor (you should)?

I recommend first doing a compression test with the motor warmed up. Then do a wet compression test and see if the numbers go up a lot. After doing a proper compression test, if you still see low compression, signs of ring wear (read that compression test page), or pressure differentials of more than 15psi between any two cylinders, I recommend having a leakdown test done. Here is a description.
Post the detailed results of your boost leak test. You can fix some boost leaks with RTV, but there are other leaks you cannot (or should not) such as injector insulators and bad PCV valve, so I'm not convinced you fixed all of the boost leaks.

We can go from there.

- I am new to turbo car and i afraid that i might break the turbo so i only presurized up to 10psi and found the leaks
- I did the compression test when the engine was warm. But i didn't let the throtle Wide Open.
- I didn't do any other tests beside the two i listed

I agree with you that i need to perform more tests on this car

 

[kenamond]

I am able to hear my turbo spool when i rev it. When i did the Boost Leak test I only presurized the turbo up to 10 psi. I don't know that amount is low or hight ?

It's not about whether you can pressurize to 10psi. It's about how that pressure holds when you stop adding air. If it leaks down to 0psi in 1 second, you have major boost leaks.

I would recommend doing a leak test at a minimum of 15psi and max of 20psi since you're stock boost right now. When you pressurize and then stop adding air, it shouldn't drop quickly. 1psi drop per second isn't bad and is about the best you'll see with that poor compression. Have someone watch the boost gauge (you do have an aftermarket gauge, right?) to tell you when to stop adding air and then to watch how quickly it drops back to 0.

One sign of a possible major boost leak is running really rich. This can show up as terrible fuel economy (maybe 10mpg or less) or black smoke if you're WAY rich, or smelling gas in your exhaust.

Make sure you're doing your boost test correctly, and make sure you're doing your compression test correctly (read that webpage I included before, understand it, and follow it).

Good luck.

 

[The_one]

1) are you hearing spool up and the BOV?
2) are the RPMs jumping when you step on it?

- I hear the psssh pssh sound when i shift into gear
- RPM works fine, idle like a charm.

 

[The_one]

130 compression on a stock 2G 7-bolt motor is not good. Either way, you should still make some good power. Try something as simple as changins your spark plugs. It's cheap (under $15) and you'll be doing the car a favor in the long run.

- I will do that today or tomorrow

Thanks

 

[The_one]

You want to pressurize the motor to what ever boost levels you will most likely run one day. I test mine up to 22psi. You pressurize it to at least 20 psi

- How do you pressurize the motor ?
I did the Boost Leak Test at 10 psi (i was chicken)

 

[No_Skillz]

... Do you have a boost guage?

"pressurize motor"... he means boost leak test. Go ahead and do the test at 20psi. You won't damage anything. And if you do, you should be grateful since it means that part was going to break and you found it.

 

[kenamond]

Okay. Lets slow down for a second.

You need an aftermarket boost gauge to do a proper boost leak test. The stock gauge doesn't have numbers on it and doesn't actually measure boost pressure (it's what the ECU "thinks" the boost is). We need real pressure numbers for the test. If you don't have an aftermarket gauge, stop here and tell us if you are willing to get a boost gauge. If you have one, read on.

Do your boost test on 15psi or maybe 20psi, but don't bother going higher. A 15psi boost leak test is perfectly safe for your turbo and car. Just make sure you have your pressure regulator on your compressor set at maybe 30psi or something - definitely not a good idea to have it at 120psi.

Have someone watch the boost gauge. They should tell you when to stop adding air (when the gauge reads 15psi). After you stop adding air, they should count off the readings as they drop. This gives you an idea of how quickly the pressure is leaking out of the system.

If you've done a proper compression test and get 130psi compression, your motor is worn out and needs work. Aside from this, the boost leak test pressure is going to leak out of your combustion chambers as well. This is not a boost leak, though. However, it will be one place for your test air to leak from. Don't expect to be able to hold 15psi for 30 seconds, because it's impossible.

After you've done this boost leak test, report back how much pressure you pumped into the intake and how quickly it dropped when you stopped adding air.

We'll go from there. There's not much more we can do until we find out the results of a proper test.

 

[The_one]

It's not about whether you can pressurize to 10psi. It's about how that pressure holds when you stop adding air. If it leaks down to 0psi in 1 second, you have major boost leaks.

I would recommend doing a leak test at a minimum of 15psi and max of 20psi since you're stock boost right now. When you pressurize and then stop adding air, it shouldn't drop quickly. 1psi drop per second isn't bad and is about the best you'll see with that poor compression. Have someone watch the boost gauge (you do have an aftermarket gauge, right?) to tell you when to stop adding air and then to watch how quickly it drops back to 0.

One sign of a possible major boost leak is running really rich. This can show up as terrible fuel economy (maybe 10mpg or less) or black smoke if you're WAY rich, or smelling gas in your exhaust.

Make sure you're doing your boost test correctly, and make sure you're doing your compression test correctly (read that webpage I included before, understand it, and follow it).

Good luck.

Thanks Kenamond

 

[The_one]

... Do you have a boost guage?

"pressurize motor"... he means boost leak test. Go ahead and do the test at 20psi. You won't damage anything. And if you do, you should be grateful since it means that part was going to break and you found it.

I can't argue with you on that. Yes, i do have an after market boost guage but i didn't install it during the boost leak test I did. i based my reading from this boost leak test device i built here is the link http://www.dsmtuner.com/forums/showthread.php?t=201554

 

[kenamond]

I can't argue with you on that. Yes, i do have an after market boost guage but i didn't install it during the boost leak test I did. i based my reading from this boost leak test device i built here is the link http://www.dsmtuner.com/forums/showthread.php?t=201554

You should be able to use that tester without a boost gauge (as long as it has the gauge on it like the design at that link). Do the test just as I've described, but you don't need someone to watch the boost gauge for you, because you can obviously monitor the gauge on your tester.

Let us know how it goes.

 

[The_one]

You should be able to use that tester without a boost gauge (as long as it has the gauge on it like the design at that link). Do the test just as I've described, but you don't need someone to watch the boost gauge for you, because you can obviously monitor the gauge on your tester.

Let us know how it goes.

I will perform the test either later today or tomorrow afternoon.

Thanks Alot Kenamond

 

[The_one]

Hello Guys,
I am back with the compression test result. I did the compression test today (7/24/2006) @ 8:30pm with both the dry and wet (add oil). I followed the same procedures mentioned at the VFAQ website.

Results (From Left to Right):


Dry: 133-135psi, 130psi, 130psi, 130psi
Wet: 140psi, 140psi, 140psi, 140psi

I don't know the 10psi variation is bad or good? Your inputs are welcome.

* I am approximately 5,000ft above sea level (Denver)

 

[kenamond]

Hello Guys,
I am back with the compression test result. I did the compression test today (7/24/2006) @ 8:30pm with both the dry and wet (add oil). I followed the same procedures mentioned at the VFAQ website.

Results (From Left to Right):


Dry: 133-135psi, 130psi, 130psi, 130psi
Wet: 140psi, 140psi, 140psi, 140psi

I don't know the 10psi variation is bad or good? Your inputs are welcome.

* I am approximately 5,000ft above sea level (Denver)

Well, it doesn't look like worn rings. If the rings are the problem, you'll see the wet test numbers go up 30psi or more, but you still have low compression. Are you sure the motor is a stock 7-bolt? If a previous owner swapped in a 6-bolt motor (the 1g motor) with stock 1g pistons, your compression isn't actually that bad. This is because the 1g has a lower compression ratio, so the range of "good" compression test results is also lower (121psi is the service limit on a 1g, whereas 133psi is the service limit on a 2g). I'm sure someone on the forum knows how to tell a 6-bolt from a 7-bolt, but I'm not sure how to tell if it has 1g pistons in it or not (if they swapped in a 6-bolt, 1g motor but put 2g pistons in it, you end up with 2g compression ratio and 2g compression specs that go with that compression ratio, and you're back to having a compression problem). You might want to find the answer to the 6- vs. 7-bolt question before going any farther or you might end up spending money on tests for no reason.

 

[The_one]

Well, it doesn't look like worn rings. If the rings are the problem, you'll see the wet test numbers go up 30psi or more, but you still have low compression. Are you sure the motor is a stock 7-bolt? If a previous owner swapped in a 6-bolt motor (the 1g motor) with stock 1g pistons, your compression isn't actually that bad. This is because the 1g has a lower compression ratio, so the range of "good" compression test results is also lower (121psi is the service limit on a 1g, whereas 133psi is the service limit on a 2g). I'm sure someone on the forum knows how to tell a 6-bolt from a 7-bolt, but I'm not sure how to tell if it has 1g pistons in it or not (if they swapped in a 6-bolt, 1g motor but put 2g pistons in it, you end up with 2g compression ratio and 2g compression specs that go with that compression ratio, and you're back to having a compression problem). You might want to find the answer to the 6- vs. 7-bolt question before going any farther or you might end up spending money on tests for no reason.

I bought it from the previous owner, and he is no longer in town. My brother has a stock 97 gst, i could do a compression test on his engine and compare the result to mine. First of all, to make sure that there is no problem with the equipments. And i will continue on with something esle.

Thanks

 

[MyBeatGSX]

Correct me if I'm wrong, but being at 5,000ft will have an effect on the compression test numbers. Whether its significant enough or not to put him above the service limit, I don't know.

Also, you did the test the first time with the throttle closed and got 130psi. And then did it again with the throttle open and still only got 130psi? Or was it still closed the second time. I think the high elevation and a closed throttle plate could be killing your compression numbers. Your motor might be in perfectly good condition, it even has remarkably even compression.

If you don't have an aftermarket boost gauge then how do you know you're even getting boost? My BOV pops even when I shift off boost and just because you can hear the turbo, doesn't mean you're making boost. I can hear mine start to spool at 5-7in/hg. And how can you "feel" it boosting if its not making any power? Wouldn't it have to be making more power for you to "feel" the boost?

 

[The_one]

Correct me if I'm wrong, but being at 5,000ft will have an effect on the compression test numbers. Whether its significant enough or not to put him above the service limit, I don't know.

Also, you did the test the first time with the throttle closed and got 130psi. And then did it again with the throttle open and still only got 130psi? Or was it still closed the second time. I think the high elevation and a closed throttle plate could be killing your compression numbers. Your motor might be in perfectly good condition, it even has remarkably even compression.

If you don't have an aftermarket boost gauge then how do you know you're even getting boost? My BOV pops even when I shift off boost and just because you can hear the turbo, doesn't mean you're making boost. I can hear mine start to spool at 5-7in/hg. And how can you "feel" it boosting if its not making any power? Wouldn't it have to be making more power for you to "feel" the boost?

I have one but i didn't installed it at the time i test drove the car. However i will install it sometime this week.

Thanks for your input

 

[kenamond]

Good info MyBeatGSX. I'll have to search around for high altitude compression numbers (I'm at 7500ft).

I found out something quite useful today w.r.t. boost leak testing. Doing the test on a warm motor makes a HUGE difference. I was leaking 1psi/second out the VC breather due to blow by and/or valve stem seal leaks on a cold motor, but I got 1psi per 5 seconds on a fully warmed up motor. Good to know when you think you got all the leaks but get too much coming out the VC breather.