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PostPosted: Wed May 11, 2016 1:46 pm 
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Went to a track day this weekend in my swapped Expo.

Image

Can't say it was fast, but it was sure fun to track my 7 seater van. Usually I track my other vehicle but I was called on last minute as a instructor and I didn't have my track car prepped.

Unfortunately after 2 sessions, something happened and I'm only boosting 6psi. Checked all turbo lines and they are tight, no vacuum leaks on the waste gate lines. Could be a boost leak, but I can't seem to locate it at the track. So took the afternoon sessions off.

I pulled the wastegate line off and its still only boosting 6psi. Hope its not the turbo but I'm expecting the worse. The motor had about 130k miles on it when I took it from the parts car. I hope its just a major boost leak that I couldn't spot.

Theres no turbo noise or air wooshing noise under boost. Will investigate further this weekend.

Anyways video below if anyone is interested.

https://www.youtube.com/watch?v=L4IpRc0coIw


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PostPosted: Wed May 11, 2016 6:15 pm 
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Check the wastegate arm to see if it has come off center. I had a 14b do this. The arm had moved in it's bore and not allowed the flapper to cover the hole it was designed to. Low boost or high boost depending on which way it "felt" like boosting.
Definitely pull off the intake snorkel and see what is up with the compressor wheel.
Cool to see a Van out on the track!

Very cool project.


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PostPosted: Thu May 12, 2016 12:08 pm 
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Sure looks like fun! Does this thing have 5000 rpm redline? ;)


Last edited by grndsm on Mon May 16, 2016 8:56 am, edited 1 time in total.

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PostPosted: Thu May 12, 2016 2:46 pm 
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Haha funny u say that.

Cause I'm using the factory tach, the thing redlines at 6000 and my brain tells me to shift at redline.

But actually with the 4G63 it redlines at 7k. So I've been retraining my brain to shift way past redline.


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PostPosted: Fri May 13, 2016 1:59 am 
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So i finally had time to check the car after the track day.

Wastegate arm and flapper is fine. Disconnected arm and flapper moves freely.

Took off intake tube and checked turbo for shaft play. Its nice and tight and rotates freely.

Checked intake pipes after turbo and it has slight amount of oil residue which seems normal.

My car has been idling higher than usual after the track day. After playing around with a few things I figured out its from my factory bov.

Once i disconnected the vac line at the bov and covered It with my finger it idled normally.

I disconnected the vac line to the factory 1g bov and covered with nipple and went for a drive. Still low boost.

It seems like the bov has a ripped diaphram allowing metered air to go thru this vac line directly pass the throttle plate into the manifold. Causing the high idle.

I dont have another bov to try out, but could this be the cause of my low boost? I dont have a boost leak tester yet but ill try and make one this weekend.

It doesnt seem like a ripped diaphram would cause it to loose that much boost? Could the bov be stuck open?


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PostPosted: Fri May 13, 2016 10:12 pm 
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Spring pressure should keep the recirc valve closed, diaphragm creates leverage with vacuum applied to open the valve if I got this correct.

With that in mind a ripped diaphram should cause the "duck chirp" in between shifts then. I had this happen and it tested fine with opening around 12 inches, hand held vacuum pump action though so maybe not an accurate test. I was getting compressor surge after every shift as pressure was not being relieved.

Low boost is a low spinning turbo, wastegate flapper not aligned or closing fully or cracks in the CHRA/housing where the flapper would seat (very common on TD05), or some massive boost leak ala the pipes and or boots/couplers. Check for a split silicone/rubber intercooler pipe, loose clamps, basically a boost leak test is next I figure. This will disclose if your TB seals took a dumpe to atmosphere, FIAV issues could be present, ETC. Heck, maybe your BISS screw wound itself out and it's a secondary issue altogether.

As you said though, disconnecting the BOV and plugging that line, with idle change, would indicate a leaky mechanism for sure.


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PostPosted: Mon May 16, 2016 9:03 am 
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7k was the "advertised" redline, stock ECU actually allowed you to go to 7500rpm! However, most people remove those silly limits and rev these engines to 8k on stock internals and up to 9-9.5k with proper supporting mods (intake, cams, valve springs/guides). Some even go up to 10k! Top dogs go up to 11k, but that usually requires aluminum rods.

So your 6k is EXTREMLY conservative! ;)


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PostPosted: Mon May 16, 2016 4:49 pm 
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Yes 6k is way too low. now if I can figure out why my car is still boosting low...

Replaced the orig 1G recirc valve with a good unit. The original one has indeed failed. The diaphragm was leaking slightly and was not opening under vacuum. However when vacuum was applied, the recirc valve could be pushed open slightly easier by hand.

I wonder if this failed recirc valve caused my turbo to fail? I did check for shaft play and there is none. It also does not leak any oil thru the seals as I see no smoke. It does spin relatively easily but didn't seem as free I last remembered. Its also not making any weird noise under boost.

Has anyone seen a turbo fail in such a way? no obvious signs of failure, but maybe the turbo isn't spinning as freely as it should hence it doesn't work properly at higher boost?


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PostPosted: Wed May 18, 2016 12:31 pm 
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Quote:
I disconnected the vac line to the factory 1g bov and covered with nipple and went for a drive. Still low boost.
Actually, even a good BOV will leak if you do this! BOV uses pressure from the manifold to stay closed (along with the spring), so this was not a good test to do ;)

But if your BOV was bad, it will definitely keep your boost down. Have you test drove it with a new BOV?


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PostPosted: Wed May 18, 2016 1:07 pm 
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I changed the BOV to a known good one this past weekend and its still boosting low.

It came off a Nissan RB25DET that boosted up to 12psi previously. Surprisingly that BOV is exactly same as a 1G BOV and bolts onto our flange! Even has the same part number, but with the nipple facing the opposite way.


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PostPosted: Wed May 18, 2016 1:25 pm 
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Have you pressure tested the intake system?


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PostPosted: Mon May 23, 2016 9:16 pm 
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Well checked for boost leaks this weekend. Found a very minor one in one of the intercooler hoses, fixed that. Still 6psi afterwards.

Had to go to a camping trip this weekend, so I took the car on a 500 mile road trip with some long and big hill climbs. Car ran like a champ, but so damn slow at 6psi. It climbed long hills with throttle pinned to the floor at 5-6 psi for 10-15 minutes straight not missing a beat. No missing, no hesitations. After the trip I consumed 0 oil as well. Fuel economy wasn't great, but wasn't horrible either at around 23mpg.

I did notice that at higher elevations at around 1700m, the car did boost lower at around 5psi.

I'm stumped ><

On a side note, weighed my van at the truck scales and its actually 3390lbs with no one inside. I had about 50lbs of camping stuff in the car I'm guessing. So 3340lbs for a stripper model 7 seater with a swap.


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PostPosted: Tue May 24, 2016 8:00 am 
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That is around 250-300lbs heavier than the van! Or... one, "husky" passenger ;)

I would next focus on hot side of the turbo. How is your turbine housing? Any major cracks?


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PostPosted: Tue May 24, 2016 8:20 pm 
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Definitely sounds like the WG flapper is not sealing correctly..Probably due to cracks in the housing most likely caused my the extreme load typically experienced during track days..


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PostPosted: Thu May 26, 2016 4:07 pm 
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Yup the next step is to look at the hot side of the turbo. From the outside I don't see any cracks.

There is a slight hairline crack on the exhaust manifold. But I don't believe its leaking very much if at all.

But if I'm taking it apart anyways I'm tempted to get a new manifold and turbo and just replace it.

Looking for a used Evo3 manifold with turbo, any other good economical recommendations for a manifold/turbo setup?


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