Boost Creep

[Stephen@NCAutoUSA]

Before I do anymore changes I want to ask opinions on what may be the issue for this right now. Here's the background of my kit.

Custom made by member Elite
Precision 6262 turbo
Tial BOV
Tial 44mm Wastegate
Manual boost controller
A2A inter cooler
500whp, 93 octane, and a boost spike up to 16psi which then settled down to roughly 14 if I remember

Now the important things I recently changed
Manual boost controller to an electronic one "mac valve"
SOS W2A inter cooler


My issue is with boost creep now. I don't have the dyno sheets or logs but once I set up a laptop I can pull some runs and post but we ran the car on the dyno and after slowly turning the boost up or doing what tuners do with the valve we reached 14psi. I was running some not to good gas that I got in the corn fields of maryland but didn't think much of it and we heard some slightly knock so we just turned it back down to 12psi. At 12psi we did 477whp which I'm happy with. We also set up a triggered toggle switch on one of the pins to activate and deactivate the mac valve so I can just run wastegate spring pressure for the track.

We tuned on Monday evening. I had VIR Tuesday and Wednesday and only ran the wastegate setting. Thursday I switch back over to activate the mac valve and the car seems to let off under WOT pulls.

I test this out and it happens in 2nd and 3rd gear pulls and I didn't try the others. After meeting back up with my tuner he pulls some logged runs today and we discover that it's creeping up. I believe we set it at 13.66 for cut off but the target was 12psi.

I'm just wondering what it is? A key thing is that the car ran fine and I didn't notice anything at VIR this past week when I was just running wastegate spring pressure. I was WOT on the straights as well for the most part in 3rd gear and had no issue or cut off. Essentially these items are all the same as well when I had my previous tune on the manual boost controller, the items are all the same size... It's really odd because when he was tuning the car it didn't behave like this on the dyno either. I didn't hit anything at VIR, and the only thing that I'm told to check is the lower wastegate line to make sure that doesn't have holes or damage, but I ran the lines away from hot items and I don't think that's the issue.

So the theory is that since I was running higher boost before the creep wasn't an issue since we were running more boost. Now that we're trying to limit it lower the wastegate can't let enough pressure out therefore we need a larger waste gate "my tuners saying a tial 60mm wastegate would work".

Another option is to run good quality 93 octane gas and hope to not knock and go back up to 16psi target

I'm kind of stumped. Spark plugs were changed and gapped low. I believe they are Ngk 7's and gapped at 22. I clocked my turbo when changing things out and also had the turbo itself off the Y pipe and the wastegate off. I'm just trying to list things that I had my hands in too just encase I should check anything specific out.

Other then that I'm stuck with trying to throttle enough to run hard but not enough to go into boost creep.

 

[E-Nough Logic]

If the car is controlling boost adequately on the wastegate spring then you do not need a larger wastegate, and more than likely the plumbing is fine as well. It is more than likely a boost controller/boost mapping problem. What is your wastegate spring rated for, and what boost levels are you seeing without the solenoid active?

I'm guessing you are controlling the solenoid with AEM right? Setup for this takes a lot of time, and the weather can change around the variables as well. Boost target compensation can help but if Boost cut is set too close to boost target it might not get a chance to mend things.

Are you familiar at all with the AEM software? I always suggest anyone that uses a boost solenoid get comfortable with at least the boost settings in the AEM software as it can be very difficult for the tuner to prepare for all variables in one tuning session, and the boost tables may often times need work by the end user.

 

[Stephen@NCAutoUSA]

Hey man thanks for chiming in. To answer a few questions that you have.

I was fine for a day running off wastegate at the track but when I flipped the switch to activate the solenoid the next day is when it cut out. Ever since then with and without the solenoid on it still creeps and cuts off. It just cuts earlier under full throttle when running the solenoid vs just the wastegate.

I lost to a mustang today since it cut out real early and more then once!

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Also to mention when we were tuning the previous night before VIR it was pretty cool and that earlier in the session he had trouble controlling the boost but after things got nice and warm it was I guess easier?

At the track conditions were cooler of course in the morning but outside temps got up to roughly 75 max if I were to guess?

 

[E-Nough Logic]

Ok didn't realize you were having problems on just the wastegate spring. What boost level is your wastegate spring?

How is your boost controller plumbed? Do you have direct pressure to the bottom port on the wastegate, and the boost solenoid controlling the top port(Left example in the pdf below) **or** do you have the bottom port controlled by the wastegate(Right exampled)?

http://www.aemelectronics.com/Images/Products/Installation Instructions 30-2400.pdf

A quick way to eliminate any type of control issue is to remove the boost controller. Run a single line from a pressure source to the bottom port on the wastegate and see if you still have creep issues.

 

[Stephen@NCAutoUSA]

I believe my wastegate spring is 8lbs and it's plumbed like the diagram on the left since it's an external setup.

If I remember there's 2x ports on the side and one on top. I think only one side one has a fitting too and the other was open so not sure if that other hole not being used on the side of the wastegate should be plugged or not.

I used 1/8th ID barb fittings with solenoid valve and wastegate. I used basic Home Depot brass fittings with Honda bond instead if Teflon tape and I forget if I used honda bond on the wastegate or not but I don't think so.

Just trying to shoot stuff out to you now to see if anything red flags at all.

So basically I should run a line from the turbo to the side of the wastegate and see if it still boost creeps up?

If it does wouldn't that just confirm it's the wastegate size if I stick to a 12 psi cut off still?

 

[sohc_mshue]

Hi guys I am the one tuning this. When the car is switched to low boost it is directly running off of the wastegate spring. Solenoid output is 0%. It is runnin with the solenoid completely off.

On the dyno with it running on only the spring it experiences about 2-3 psi of creep from 6-7000 rpm. Wastegate spring looks to be a 5 psi spring.

With the controller on it held 12psi across the powerband.

Now on the street with the controller turned off it creeps all the way to redline ( hits boost cut at 13.5 psi well before redline). Being that this did not happen on the track I am inclined to believe that something on the setup has changed. Likely a leak in the gate line. Or the gate valve possibly sticking or something.

It should not be too bad of an issue to resolve. I would start with the line.

 

[E-Nough Logic]

Additional side ports should be plugged. Is it an mvr or the older 44mm. The newer mvr has cooling lines that are optional and do not need to be plugged.

Also if the solenoid is plumbed wrong it can also leak as well.

 

[Stephen@NCAutoUSA]

When I have a second I'll pull things off and check the wastegate and also replace the line going off the side of the wastegate.

The only thing that's strange is there's tons of clearance I think and they're not rubbing or hitting anything.

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The solenoid is wired the way the aem diagram is on the left. That's what I referenced when hooking it up so I don't think that's the issue.

Maybe the side hole has to be plugged then? The wastegate is 4 years old I believe so not to sure about the model. I can get a picture.

I left the side of the hole unplugged though I believe because there was no plug in the other to begin with. When I had a manual boost controller it had only one line going out, then to the manual controller, then the barb fitting on the turbo. Before I think the top hole and one of the sides were left open, but this wasn't an issue before I don't think. Although I did have a boost spike before then it settled back down. I wish I could find the old Dyno of the psi I have floating around...

 

[Elite]

From memory, I think it's a .7 bar spring, but may be a .5 at smallest.

 

[mrbozo1]

Before you destroy your motor , take some pics of how the boost controller is plumbed so someone here can confirm that is done correctly, it is very easy to misunderstand how it is to be done.If you eliminate the electronic boost controller does it creep. When I say eliminate the boost controller I mean disconnect it and then try it, not just turn it off because if it is plumbed wrong it will still apply boost pressure to one side of the diaphram and it will function incorrectly. Pics are best. You should resolve this boost creep before you drive the car hard as this could be an expensive mistake.

 

[Stephen@NCAutoUSA]

Gotcha. I'll post some pictures in a few hours. Driving into work now.

Also the wastegate hole I thought may have been left open or any banjo bolts that were loose are all tight.

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<img src="http://www.nsxprime.com/photopost/data/500/photo_45.jpg" />

<img src="http://www.nsxprime.com/photopost/data/500/photo_37.jpg" />

<img src="http://www.nsxprime.com/photopost/data/500/photo_2-2.jpg" />

Ok so ignore the heat wrap that kind of looks like a black hose since that's what the wires are wrapped in.

The bottom of the brass T fitting goes to the side of the wastegate. The other sides of the T go of course to the turbo and the right side of the solenoid. The other line from the solenoid goes to the top of the wastegate.

The solenoid isn't out of site or hazards like water and dirt, it's just behind my bumper cover and on top of the lower section of the rear valance so maybe the middle part got clogged?

Mrbozo when you say remove the controller all together do you mean then to just plumb the side wastegate hose to the side of the turbo for a run to see if it still cuts out?

Would temp play any role in what's causing the creep or not that major of a role?

 

[mrbozo1]

To eleminate the boost controller and just run off the wastegate spring....run the line from the compressor housing to the side of the wastegate,leave the top of the wastegate open to atmosphere... this way the wastegate sees the actual boost that is coming from the turbo and it will control if from there. If it still builds too much boost it is the wastegate not relieving the pressure. Good luck and let us know the results.

 

[E-Nough Logic]

Someone swapped your Tial for a Precision wastegate! May not be THE problem, but A problem lol.

Just cut a new vacuum line too so you can eliminate any cracked line from being a problem. Wastegate may just need to be freshened up a bit, might have a torn diaphragm. I haven't dealt with precision wastegates before.

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Any pics of the rest of the turbo setup, always like to what other turbo kits are out there.

 

[curtsr]

Another option is to run good quality 93 octane gas and hope to not knock and go back up to 16psi target

I'm not sure why you aren't always running a premium grade rather than low or mid.

 

[Stephen@NCAutoUSA]

Someone swapped your Tial for a Precision wastegate! May not be THE problem, but A problem lol.

Just cut a new vacuum line too so you can eliminate any cracked line from being a problem. Wastegate may just need to be freshened up a bit, might have a torn diaphragm. I haven't dealt with precision wastegates before.

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Any pics of the rest of the turbo setup, always like to what other turbo kits are out there.

No other pictures right now but I can get some up this weekend. But yeah it's a Precision, haha.

I'm not sure why you aren't always running a premium grade rather than low or mid.

It was 93. Just not my usual sunoco or shell stations I usually go too.

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Do you guys think a lower psi spring would work in there if it's not the lowest? I think I still have some springs in the original box laying around I can try swapping out to a smaller one.

 

[mrbozo1]

What you need to do is eliminate potential problems....You must make sure your wastegate is functioning properly. Then go to the boost controller and make sure it is functioning properly....Then confirm your tune is correct. If the car used to work on just the wastegate spring ...confirm that. Once you confirm that ,you can move on knowing that is not your problem.

 

[Vega$ NSX]

What you need to do is eliminate potential problems....You must make sure your wastegate is functioning properly. Then go to the boost controller and make sure it is functioning properly....Then confirm your tune is correct. If the car used to work on just the wastegate spring ...confirm that. Once you confirm that ,you can move on knowing that is not your problem.

You beat me to the punch. I was going to recommend something similar. With complex builds (I put turbo builds in this category) when a problem occurs, the best approach to fixing it is to compartmentalize the problem. It's like links on a chain, you'll need to examine each link to find the weak point. The very first thing I would check, is to just double check your entire plumbing. Just make sure all the piping is correct, all the fittings are tight and that you have no leaks anywhere in the system. Then the next thing you need to do is focus on the wastegate and spring. Disable your boost controller and verify that your wastegate and spring are working properly and consistently. If necessary, try using a different spring for a lower boost pressure and verify proper function and consistency. If that checks out ok, then check your boost controller and make sure it is functioning correctly. Last check your tune, your mappings and especially any feedback loops.

 

[RYU]

Stephen - I really don't like the look of this zip tie! Might be collapsing that vacuum line. $0.02.

 

[curtsr]

Stephen - I really don't like the look of this zip tie! Might be collapsing that vacuum line. $0.02

Make that $.03

 

[Stephen@NCAutoUSA]

I'll undo that one but it's not tight... The sheeting that looks collapsed in that picture is just like cloth material and there's 2x wires inside. The tubing used has like a 1/8th inch sidewall so unless bent it's not cutting anything off.

 

[Vega$ NSX]

On an aside, I've found that zip ties get both hot and dried out in or around the engine or underside of the car. I'm sure living in Vegas exacerbated the problem, but I've have numerous occasions where random zip ties have broken off on me with little warning, rhyme or reason. Be careful.

 

[Stephen@NCAutoUSA]

Cool thanks for the replies everyone. I see what everyone is saying with just doing things and ruling items out slowly starting from the most simple.

I originally wanted to do push lock fittings but that ended up not working out so back to the rubber lines. When I replace the lines I'll be replacing the zip ties I think as well.

 

[Elite]

All this is why I have used simple old manual boost controllers over the years. :biggrin: Pro's and con's to either option.

Let us know what happens when you remove the lines and try just wastegate spring.

And going down in spring rate will not help, it will likely hurt.

 

[Stephen@NCAutoUSA]

All this is why I have used simple old manual boost controllers over the years. :biggrin: Pro's and con's to either option.

Let us know what happens when you remove the lines and try just wastegate spring.

And going down in spring rate will not help, it will likely hurt.

Haha I hear ya. I was on the phone with precision as well about wastegate placement but what he also mentioned that switching from my a2a to w2a could have caused it as well.

 

[E-Nough Logic]

Haha I hear ya. I was on the phone with precision as well about wastegate placement but what he also mentioned that switching from my a2a to w2a could have caused it as well.

The air to water will have less pressure drop resulting in more boost but I can't imagine it making too much of a difference. What boost levels were you getting before with the A2A?