Kia Forte Turbo Forum banner
1 - 14 of 14 Posts

·
Registered
Joined
·
633 Posts
Discussion Starter · #1 ·
I don't know if it's just the ol' butt dyno that's out of calibration but I feel like the car doesn't just have the same amount of power as it used to. I can see that the commanded boost value (through Torque) will routinely show 16.4 PSI under WOT but ofcourse this isn't a measured value. Eventually I plan on installing an actual boost gauge.

I know a common issue is the stock BOV developing a tear in the diaphragm but from what I can tell, I'm not exhibiting any symptoms of the BOV going bad.

I've got 31,000 kms (19,200 miles) on the car now and have never inspected the hoses or clamps. I should probably test for boost leaks using a PVC end cap with a compressor fitting and an air compressor.

Now, you can find a ton of videos or guides on using this method, but my plan was to disconnect the stock intake at the air box and put the cap there. Would this be my best approach?

Second, you must regulate the PSI starting small (5 PSI) and work your way up. Since our cars run about 16 PSI stock (18-19 peak), theoretically I should be able to to pump 16 PSI through the system and not worry about causing damage, correct? I will probably go as high as 10 PSI when testing for leaks as I feel that should be enough to find any leaks.

I can take pictures for those who are interested. I appreciate all comments, suggestions and tips.

What are some of your methods?
 

·
Registered
Joined
·
1,697 Posts
First - why don't you get a reading from MAP? That is the pressure in the manifold. Hence, the true boost you get, despite what commanded was.

Then, you are not looking for small leaks... turbo is a very efficient compressor in terms of flow. Your garage compressor, even if it is 10 gallon tank, is not quick enough to give you good knowledge. I mean, for small parts of the system, such as IC, or hotpipe, but not the whole system. What I am saying, you will not be able to hear/see the leak with this slow flow you are getting from the garage compressor.

Check all the clamps. There are not too many. I bet it would be easier to inspect each and every clamp that do compression test. That's what I would do.
If nothing can be found this way, then compression could be done.

Keep in mind you are dealing with air. It is not liquid that is easily noticeable. Any air leaks - that must be quick hiss to be noticeable for you.


So again - Torque gives MAP readbacks. Use that to see what is commanded and what is actual. Lack of power does not necessarily mean poor boost. It could be easily retarded timing.
 

·
Registered
Joined
·
633 Posts
Discussion Starter · #3 ·
Everywhere I read it shows its a good idea to do this test atleast once a year. Didn't know about the MAP readings mind you.

Now correct me if I'm wrong here, but from what I understand the system should remain pressurized for atleast a little while giving you enough time to check for air leaks... Or with a bottle of soapy water you can just spray the clamps and look for bubbles.

I've got a 25 gallon tank at my disposal.

I could check all the clamps but that wouldn't necessarily tell you there is a leak... Which is why I thought this method was so highly recommended.

Could be other things yes... I just thought this was a good start.
 

·
Registered
Joined
·
1,697 Posts
25 should do. What pressure you got there? 125 psi? Again, turbo is very quick compressor for low pressure so if you really have a leak it will be rather larger than smaller. And refilling your tank may be not quick enough.
If you have a good quality gauge in range 0-20 psi (mandatory to do the leak check) to observe pressure drop. For sure nothing what is on the tank would be usable as they are 0-150 psi range, so 10 psi for them is not really reliably detectable.
If you got a way to lock (seal) the ends, sure that would do. But I cannot tell you what pressure drop is acceptable. 2 psi per 10 seconds? That depends on the length of the system, volume, and such...

I personally would not really start there due to it being a very labor intensive project. I would rather check the clamps first. Remove each one, disconnect the hose, check for signs of leaks. Or maybe one clams is loose?

And then do the leak check.


But without the readback from MAP, or a boost gauge, I would not be convinced that I found, or not, a leak.

Again - get Torque and find MAP. It is called: Turbo Boost and Vacuum Gauge. Located almost at the very end of the list. I use the paid version, not sure if free has it same way.
Compare the data first. Without this you do not know what you are looking for.
If you really discover boost does not build up as quickly as it should, start looking for leaks - either leak check, or visual inspection. I would, again, do inspection first as it is easier and faster. No soap, no mess. Then after all is tight - get the pressure test and verify that all is good. You see, you may have a leak on the IC. If that's the case - once you have all clamps tight (so they do not leak) and you already excluded other connections - that must be IC.


The other condition would be... dying compressor.


I just feel doing leak test is like replacing head gasket if uneven idle. See my point? One would check vacuum leaks, spark plugs and then compression/head gasket. Try simple and easy tasks first.
 

·
Registered
Joined
·
633 Posts
Discussion Starter · #5 ·
Wait, I thought the "Turbo Boost and Vacuum Gauge" option was a commanded value, not measured?
 

·
Registered
Joined
·
1,697 Posts
Yep, it is measured...


I am not sure you can actually read commanded value. ECU may request oxygen level (hence, AFR) in exhaust, but not really boost. It may say it was overboost, or boost was too low for too long to create an error, but request? Mapping, and I bet I will be corrected, shows expected/possible boost, but not really "requested" boost.

So... experiment is coming :)
That is from MAP sensor.
To check that - disconnect the sensor and see how it goes. Simply unplug MAP when engine is off, but ignition on. You will lose intake temperature and boost/vacuum will be crazy or completely gone.
I did it once for testing so it is safe. Just do not drive it. It is fail safe anyway, but driveability will be heavily impaired.
 
  • Like
Reactions: staax

·
Registered
Joined
·
633 Posts
Discussion Starter · #7 ·
Wow, I had no idea that is the measured value. I thought that was the ECUs commanded value based on throttle input/load etc.

On WOT in a 2nd or 3rd gear pull I will see 16.4 PSI but it doesn't feel like all the boost is there. Maybe I'm just getting too used to the car and it doesn't feel as exciting anymore.

Perhaps I could be hitting max boost, but having it fall on its face due to a small leak? Like I mentioned earlier I think the BOV is fine, I would've guessed there was a leak around a clamp as I hear they arnt the best.

Learn something new everyday.
 

·
Registered
Joined
·
1,697 Posts
hmmm... try resetting ECU.

Maybe cleaning the MAP would help.

Leaks are the best noticeable when it you are in boost build-up. If it takes long time for boost to build, it may suggest leak or poor turbo performance.
16.4 psi - yeah, that is something what I was reading most of the time. Only time it would peak would be upshifts and at lower rpm. Higher rpm would cause boost to get lower.
That is for stock, non-tuned.
 

·
Registered
Joined
·
633 Posts
Discussion Starter · #9 ·
I'll try both those. Can't hurt.

I remember 2nd gear pulls always being very torquey but I don't feel that anymore. And I only do WOT in both 2nd and 3rd gears., By the time I hit 4th I'm already going fast enough.

If I forgot to mention, I'm bone stock running the stock tune. Only running catchcans.
 

·
Registered
Joined
·
194 Posts
Keep it simple

With the mileage you have it would not be a bad idea to put your car on jack stands go underneath and remove, clean, and re-install all your "hot pipe" and IC connections. This way you can see how much oily shit or not is going through your system. This alone will erase 95 % of your boost leak causes normally encountered. The other big two are, the BPV/BOV as you have mentioned and the intake manifold map sensor gasket. I think you will be shocked how filthy you pipes will be, especially if you have not used OCCs':eek:
 

·
Registered
Joined
·
633 Posts
Discussion Starter · #11 ·
Thanks, I have used OCCs so hopefully it won't be too bad.

Would you recommend replacing the clamps or atleast having some on hand in case they break? I don't know the quality of the stock clamps.

I'll also check the MAP sensor too.
 

·
Registered
Joined
·
1,697 Posts
You will see how they hold.
For stock the clamps are sufficient. I think they use 8 mm socket. Not easy to pull off the cap for the very first time, especially after a long while...
I would add a drop of oil on the gearing of the clamp. Less resistance on the thread makes it easier to gauge how tight they are. Screwdriver is NOT enough.

I have never seen any clamp to "break", like crack. The only damage I ever found was thread being stripped but too much torque. So do not over-tighten them.
 

·
Registered
Joined
·
194 Posts
Thanks, I have used OCCs so hopefully it won't be too bad.

Would you recommend replacing the clamps or atleast having some on hand in case they break? I don't know the quality of the stock clamps.

I'll also check the MAP sensor too.
Yes. They are cheap ass worm gear.**** Even though your are stock tune, you want to be as fire and forget as possible. Do it once and have confidence. The absolute strongest T-bolt clamps I have tried, (I tried them all), are made by HPS. I was popping aftermarkets left and right until I found these after my SSturbo.
I was "splitting" silicone couplers as well. The HPS are 5 layer. (of course you don't need these). Just to let you know what I encountered.
This way the effort you make will hold as long as possible under any boosting circumstance. Nothing worse than doing a double drop, and POP-HISSS CEL (under-boost) awww shit !
I can't remember the diameters since my piping is not stock anymore but the clamps that would work would be a 2.25.

Its going to surpise you how much crap you will find lodged in your connections. Its not that they "break". The boost sends blow by etc even with OCCs and this CREEPS and PENETRATES into your connections. It ultimately acts as a lubricant in a perverse way, and lets the boost leaks happen. It ineviatable, its why the maintenace/cleaning re-install protocol makes sense. The frequency would be based on how aggressive you were in your driving.
 
1 - 14 of 14 Posts
Top