Boost drops to 0 psi @ 5K RPM in 3rd (4EAT)

Bdub · Post by **Bdub** » Fri Apr 10, 2009 12:27 am

It came with 3 different springs for different boost settings, an 8-12psi, 12-16, and a 16-20psi. I'm not sure how true those numbers are, but I just used the smallest spring because I'm just running a stock turbo.
I didn't notice any difference in building boost, but the car holds it much longer than it used to.
The metal BPV is probably 3 times larger than the stock subaru one too. So, I had to get some larger hose and a couple reducer elbows.

Adam West · Post by **Adam West** » Fri Apr 10, 2009 1:32 am

Is it one of these?

http://www.forgemotorsport.com/content. ... =FMDVMSP02

Sorry to hijack but this might be a useful upgrade for high boost applications and have been trying to get clear on the benis.

Cheers,

Bdub · Post by **Bdub** » Fri Apr 10, 2009 9:07 pm

That is what it looks like. But, mine you can unscrew the top and remove the spring. Not sure if you can with the one in the link.
I got mine from an Ebay seller in Japan for around $60.

wtdash · Post by **wtdash** » Sat Apr 11, 2009 3:36 am

Uh, don't mind me.

JK...this site and its members are awesome and good info is always welcome in my book.

Update:

What are the chances that 3 BPVs are bad?? Anyone?

I tried both replacements and I'm still dropping to 0 psi...Oh, and it's getting worse it now does it in 2nd gear, too.

What's left? The TD04? It has lesss than 15K miles on it (if the Seller was honest).

Yea, I've been running it hard since I've had it - 14-18psi, but jeesh it's a Subaru!

I guess I'll pull it apart and check for shaft play? What else?

Thanks

asc_up · Post by **asc_up** » Sat Apr 11, 2009 3:50 am

I'd try it with the MBC just one more time, just to make sure it's not your turbo or a leaking BPV.

Although, I did notice something in your signature. It says that you're using the Stage 2 Revtronix chip. The problem with that is that they've only mapped out the chip for the VF-11, not the TD04. I wonder if that's where the problem lies. You might not be getting enough fuel at full boost in 3rd gear up top, so then your engine might start to knock and cause the BCS to limit boost to WG pressure (5 psi).

beatersubi · Post by **beatersubi** » Sat Apr 11, 2009 5:10 am

Its actually a Mitsubishi.
I also think it has something to do w/ the EM. Do you have a stock ECU you could swap in?
Although, its odd that it'd drop to 0psi. There'd have to be pressure to the wastegate actuator to open it. Unless there isn't enough exhaust pressure to spin the turbo fast enough to make boost. Which would come back to the EM.

Post by **Legacy777** » Sat Apr 11, 2009 5:14 am

I would tend to agree it's probably something with the EM.

If you have a select monitor, what the knock sensor reading and see if it's pulling back timing when you have no boost.

Other thing that you may want to look at is the TPS, if there's a dead spot at full throttle, it may be giving you some weird issues.

wtdash · Post by **wtdash** » Sat Apr 11, 2009 5:23 am

asc_up wrote:.......
Although, I did notice something in your signature. It says that you're using the Stage 2 Revtronix chip. The problem with that is that they've only mapped out the chip for the VF-11, not the TD04. I wonder if that's where the problem lies. You might not be getting enough fuel at full boost in 3rd gear up top, so then your engine might start to knock and cause the BCS to limit boost to WG pressure (5 psi).

I'll pass this up to Mike @ Revtronix for comment.

I know next to nothing about EM/tuning (that's why I like the chip), so can't argue your point. I do know I went to Vancouver, BC to work w/Revtronix on the tune, put it on the dyno there, and have been doing testing w/Revtronix for the last month to finalize the settings.

WG pressure on my TD04 is 10 psi - I've tested it. I'm getting 0 psi - no boost @ all @ 5K rpm.

wtdash · Post by **wtdash** » Sat Apr 11, 2009 5:32 am

Legacy777 wrote:I would tend to agree it's probably something with the EM.

If you have a select monitor, what the knock sensor reading and see if it's pulling back timing when you have no boost.

Other thing that you may want to look at is the TPS, if there's a dead spot at full throttle, it may be giving you some weird issues.

I do have a select monitor USB cable and the Revtronix data logging software.

I have an extra TB and TPS. I'll check mine 1st (w/your TPS adjustment links (thanks)) and then try the other one I have.

Would the IAC have any effect @ WOT?

wtdash · Post by **wtdash** » Sat Apr 11, 2009 5:53 am

beatersubi wrote:Its actually a Mitsubishi..

Yeah, I was generalizing....not fair to blame Subie on a Mitsu turbo.

beatersubi wrote:I also think it has something to do w/ the EM. Do you have a stock ECU you could swap in?
Although, its odd that it'd drop to 0psi. There'd have to be pressure to the wastegate actuator to open it. Unless there isn't enough exhaust pressure to spin the turbo fast enough to make boost. Which would come back to the EM.

I do have a stock ECU (or could just pull the chip), but what's a bigger PITA? Removing the turbo for inspection or swapping the MAF (easy) /fuel rails (not so much)?

The car ran w/the stock ecu and maf, just way rich on the 480's. I could start there.

Thanks ALL for the input tonight. I'm F'ing frustrated, but the feedback helps as it gives me a plan of attack.

wtdash · Post by **wtdash** » Sat Apr 11, 2009 10:28 pm

I put in my other ECU (w/out a chip) and MAF.

NO Boost Drop!

But this is @ a max of 13 psi....which is where I was before w/the stock BCS, TD04/TMIC setup....10psi WG actuator plus 2-3 psi of boost creep...yeah it's strange.

Mike @ Revtronix also suggested I try the original chip again....I never had the boost drop w/it.

Also, adjusted the TPS, which made no difference. I initially tested it (just resistance) according to procedures I found on here and it didn't match any of the values given....but neither did any of the other 2 throttle bodies/TPS I tested...they were all the same.

beatersubi · Post by **beatersubi** » Sun Apr 12, 2009 5:40 am

Well, at least you know where the problem lies.
12-13psig is normal w/ a td04. Its due to the stock management trying to work w/ the vf11 w/g actuator.

wtdash · Post by **wtdash** » Mon Apr 13, 2009 12:27 am

beatersubi wrote:Well, at least you know where the problem lies.
12-13psig is normal w/ a td04. Its due to the stock management trying to work w/ the vf11 w/g actuator.

I'm not convinced the chip is the cause, as the issue didn't occur 'til halfway thru testing the 2nd chip.

However, I'm not sure where to look in my turbo setup.

Here's a recap of what I know:

- When the car is just warmed up, the 1st full throttle run works OK.

- If I only use 1/2-3/4 throttle I can still accelerate past 5k rpm and get to 6k rpm.

- If I let off on the throttle after boost drops, let the car slow a bit and then hit it, boost comes back until I hit 5K again.

- It started in the last month, during testing of the 2nd chip.

- Running the stock ECU/MAF/480cc injectors/13psi it does NOT drop boost....but it does run like crap and is slow.

- I've tried 3 different BPV's (all stock) w/out a difference.

- It still does it w/an MBC or GM BCS.

EDIT: The boost drops to 0 and stays there as long as I keep the pedal to the floor...I've continued to run the car this way for @ least 5 seconds. The car decelerates but continues to run - not lurching/sputtering/etc. Just a smooth decrease in speed and rpm. Only after I let off the throttle and reapply it does boost come back normally...until I hit 5K rpm and it drops again.

If there's a leak or other issue w/my setup does it sound like it's before or after the turbo?

Thanks,

Post by **Legacy777** » Mon Apr 13, 2009 1:56 am

What is the MAP sensor telling the ECU?

I wonder if you're getting a funky type of fuel cut? You could try a FCD or some sort of mechanical setup to bleed boost to the MAP sensor to make sure the ECU isn't cutting your fuel.

wtdash · Post by **wtdash** » Mon Apr 13, 2009 2:44 am

Legacy777 wrote:What is the MAP sensor telling the ECU?

I wonder if you're getting a funky type of fuel cut? You could try a FCD or some sort of mechanical setup to bleed boost to the MAP sensor to make sure the ECU isn't cutting your fuel.

The Revtronix chip has the fuel cut @ 18-19psi, which I have hit due to a boost spike-felt just like the stock's 13psi.

I have Vikash's FCD, which I could reconnect.

wtdash · Post by **wtdash** » Tue Apr 14, 2009 6:40 pm

Update:

Definitely temperature/heat related. Yesterday a.m. and p.m. I did multiple WOT runs, and it only occurred after 5500 RPM on the last run.

Temps were around freezing in the a.m., and <40 F after work (it snowed this a.m.!).

So what items under the hood are so heat-sensitive they would cause my issue?

beatersubi · Post by **beatersubi** » Wed Apr 15, 2009 2:56 am

IAT sensor?
Was that with the stock ECU or the chip?

wtdash · Post by **wtdash** » Wed Apr 15, 2009 4:16 am

beatersubi wrote:IAT sensor?
Was that with the stock ECU or the chip?

EDIT: Per Legacy777:
There is no IAT sensor for the MAF based cars.

I believe it was an OBDII (95+)
sensor.

And this was w/the chip installed.

I tried a different ignitor and still have the issue - our temps are back up into the 50's.

beatersubi · Post by **beatersubi** » Thu Apr 16, 2009 4:07 am

Yeah, I wasn't sure. Its sounding like a fuel cut. Still strange that it'd only happen it third. I wonder if the MAF is sensitive to air density. That'd explain why outside temp has an effect.

wtdash · Post by **wtdash** » Thu Apr 16, 2009 4:50 am

Update:

I put in the MBC and FCD, running @ 16 psi and still got the boost drop...only difference was it occurred @ 5500 RPM, which is about 500 rpm higher than before.

Also, last week when it got up to 65 deg. F, it was dropping boost in 2nd and 3rd gear.

Post by **Legacy777** » Thu Apr 16, 2009 5:49 pm

Hmmm....this is very strange. Have you done any logging or watching of the different sensor values while this is occuring? It might be good to see what the MAF, TPS, etc are looking like on the select monitor during these events.

wtdash · Post by **wtdash** » Thu Apr 16, 2009 6:51 pm

Legacy777 wrote:Hmmm....this is very strange. Have you done any logging or watching of the different sensor values while this is occuring? It might be good to see what the MAF, TPS, etc are looking like on the select monitor during these events.

Some, but not all. I'll work on getting a complete log this weekend.

Thanks

wtdash · Post by **wtdash** » Fri Apr 24, 2009 2:46 am

Good news....it ain't the chip!

Back to stock and still dropping boost @ 5K rpm w/the MBC/FCD @ 15psi (I'm running 440cc injectors - hopefully a bit rich).

Car runs strong..way better than w/the 480's..'til I hit the boost drop.

Bad news - don't know what the f'ing issue is.

TD

asc_up · Post by **asc_up** » Fri Apr 24, 2009 3:47 am

I still think it's a faulty boost control solenoid. When mine was going out, it would sometimes allow full boost and then other times it would only allow 5 psi.

wtdash · Post by **wtdash** » Fri Apr 24, 2009 4:00 am

asc_up wrote:I still think it's a faulty boost control solenoid. When mine was going out, it would sometimes allow full boost and then other times it would only allow 5 psi.

I REALLY wish it were.....

I've used 3 different BCS' - 2 stock and 1 GM. Plus it does it w/the MBC.

The boost is very consistent; it's the boost drop that I'm fighting (and losing).

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Boost drops to 0 psi @ 5K RPM in 3rd (4EAT)