So I've been trying to get my car tuned recently, but there is a problem. I set the boost to 25 psi, go wot and it holds all the way up to around 6k and then immediately drops to around 7-10 psi. I've don't several boost leak tests and can't find any leaks. What else could it be? I've swapped waste gate actuators,boost controllers and double checked the vacuum routing.

Bbk full turbo
Fp 18 psi waste gate actuator
Hallman mbc
Map 02 dump
K&N drop in filter
Stock IX blow off valve
Works turbo back
Aquamist hfs-3
Gsc s1 cams
Act 2600
Fic 780cc injectors
Walbro 255

 

does the turbo whine when boost drops?

 

No.

 

Does your dump happen to be VTA? If so, can you audibly detect at what level of boost the gate cracks open? Have you "crushed" your IX DV, or not? Do the Hallman controllers have different rates of internal springs available, or not? If so, does yours have a light sping or a heavy spring? Do you know what level of spring pressure your actuator is adjusted to? Did you "preload" the gate or just slip the actuator on w/o any tension? Have you shortened the length of the actuator rod by cutting a few threads off yet?

 

I gather that you are in fact hitting your target boost of 25#. Is this correct? By what engine RPM is your turbo hitting 25#, please?

 

Yes my dump is vta,But I honestly can't hear it opening like I can with lower boost.I have not crushed my bov, I have no idea what spring rate it is,but I have swapped out with my tuners working one set at 30 psi,and no change I can't pass 25 psi. The wastegate was pre loaded, but I haven't cut anything.


I'm hitting full boost by 3500 and holding it till 6k and as the Rpms increase from there it drops down to 12 lbs then down to 7 in a matter of seconds. This is only 3rd gear pulls that I've tested also.

 

I am curious as to what WGA's you have tried aside from the FP 18# unit. The BBK is shipped by Chad fitted with the stock MHI IX actuator isn't it? I gather that you experienced this problem with the turbo setup as delivered with respect to preload etc.

So, what other MBC's have you used? You must be fairly handy with tools if you've been tinkering with the car yourself? Did you install the MBC, the DV and the WGA yourself? Or did a shop do it for you?

Who is your tuner anyway? Has he had any thoughts as to what the possible cause of your problem might be? Are you totally stumped yourself? Not trying to be facetious just wondering if you have any suspicions about the cause of this scenario.

Which Hallman MBC are you using? Is it the "Pro", or the in cockpit model? Are you using the turbo's compressor discharge tube or the hose from the IM to the DV as a boost reference source for your MBC? Do you have any pics of your MBC routing that you can post up please?

When you do the WOT tests you say that it is in 3rd gear right? Do you do it on level ground? I'd like you to try a WOT run in 4th, or 5th on an uphill grade instead. The grade should have at least a 25* included angle. I want to see if uphill with different load the RPM range at which the boost drops will change at all. (Of course, keep your eyes open for those pesky CHP laser gun traps....jejeje).

Also, try a WOT run with your MBC knob backed all the way out to the lowest possible boost setting. Let me know how your boost readings change.Especially note the peak boost reading for me.

Furthermore, when you back the adjustment knob out make note of just how many complete turns it takes to get from its present setting to the full soft position. For example I wanna know if it is 3&1/2 rotations from its current setting to full soft, etc.

 

A couple of things that you mentioned lead me to believe that your gate is not sufficiently preloaded. At least this is one of the most likely possible culprits. It may be that and a combination of other things working(or better, not working) together to cause your problem. But, we can only test things out one at a time anyhow.

 

We are probably going to want to disconnect your MBC and set it aside to do some testing of the actuator preload and to run the gate straight off the reference source. Are you going to be OK with this? Say yes!

 

Could go with an EBC also check your WG Duty cycle in your tune...

 

The abbreviated terms, WGDC, BCS, MAP, and even the omniscient ECU are irrelevant to this particular boost control thread.

FYI & FWIW, we are dealing with an MBC fitted Evo. Therefore, WGDC does not enter into this discussion. Comprendo?

 

Yes the BBK came with an orginal actuator, so I didn't know this was an issue until we started the road tune. My tuner Jay (boosted tuning) told me to upgrade the actuator, so the day we started the tune again,we pre loaded the fp unit, went for a test drive and same thing. I installed the MBC, DV,and actuator myself. I can post pictures of the routing if that would help. Jay suspected something to do with a pre-turbo exhaust leak, other then that im the only one tracing the problem down. I am totally stumped, ive read problems of people with tb shaft seals leaking at wot, but I don't think this could be the case. Also, I wondered if the stock intake was collapsing, but i've read this is rare.

Every test was on level ground in 3rd gear because we were starting the tune, I will try again as you stated. Also prior to this before the boost turned up i could hold 20 psi no problem, it's when we turned it a few turns up this started happening. The MBC is a hallman es, basically the poor mans version, we tried his forge MBC also, and same results. I'm using the source at the turbo for the MBC.

 

Of course, but my boost gauge only reads to 30 psi

 

I mentioned that it would be helpful for you to back your MBC knob all the way out to full soft(counter-clockwise) which is the lowest possible boost setting. Take it for a WOT spin with the controller set at full soft and check peak boost on the gauge.

Depending on the reading, this should give us an idea of the wastegate spring pressure level. We really won't know for sure if this is actually base pressure yet because this test doesn't take into account whether or not, and just how much the actuator rod has been adjusted shorter. But, it will give us an idea of spring pressure.

This will be helpful because there is a degree of uncertainty as to just how much preload if any that you and your tuner applied when you installed the new FP actuator. It seems contradictory at least for the gate to be preloaded and for you to see boost tapering down to 7-8 PSI.

It is unusual for a BBK to exhibit any boost taper at all and definitely not as much taper as you are seeing. Even a stock IX turbo which is a notorious taper hound usually won't taper much more than 4-6 PSI.

So, I really doubt that your taper issue is turbo related per se. It is probably actuator related with a dose of DV, or MBC thrown in. That is assuming that everything else is up to snuff such as: no boost leaks whatsoever, and as you mentioned no pre turbo exhaust leaks.

Incidentally, you checked all vacuum hose fittings and secured with hose clamps...even the tubing connected to the backside of the boost gauge? You installed all new 4mm vacuum hose when you installed the MBC, DV, and WGA....right?

Did you connect the reference port of your MBC to the compressor housing discharge nipple or did you "T" into the IM/DV hose?

 

Yeah, AWDs is having a weird issue. As he said, I was suppose to tune his car, but we are running into this weird issue.

When we run lower boost (20psi), it only tapers to 16psi at redline. But soon as we up the boost to our desired target (25-30psi), it does the weird taper thing, taping down to 10psi at 6Krpm. Here is a log of it.



When we saw this, I initially though the MBC was installed incorrectly/broken or WGA (stock WGA) was not preloaded. So first we tried my FORGE MBC, that work perfectly fine on my car. Still the issue. Then we tried to add more preload to the WGA, but the lock nug was rusted stuck (Kevin said he couldnt even get it loose after taking the WGA out). Since we couldn't preload the stock WGA anymore, I recommend Kevin picking up a upgraded WGA. So he bought a FP 18psi WGA, installed it himself and came back for tuning. I put a good amount of preload on the WGA, but the issue still persisted. IMO, the wastegate is close during this issue, as we do NOT hear the dump at all

He did have a meth failsafe solenoid ran with the MBC, but we eliminated that for testing. I re installed his MBC personally and its installed correct.

Notes so far:
-We have tried two WGA, stock and FP 18psi, with a good amount of preload
-We have tried two MBCs. Boost source for the MBC is off the turbo J-pipe
-Kevin has done a couple boost leak test and they have came out fine
-We have not tested WGA only, as the issue doesnt happen at lower boost (20-22psi)
-O2 dump does NOT make any noise when this happens.

Only other things I think it could be would be:
-broken turbo, which would be weird, since this turbo was bought brand new from CBRD
-pre turbo exhaust leak, which I believe Kevin checked for and said was okay.
-a "possible" timing issue, as kevin said he changed the timing belt recently IIRC. But the car runs smoothly and doesnt exhibit other symptoms of incorrectly timed timing belt

I have offered Kevin to diagnosis the issue, do more testing and find the issue, but he has decided to try to find it himself. So far, I havent charged him anything for working on his car, but it seems like this issue would possible take a couple hours of testing and taking stuff apart, which I cant do for free.