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Old 05-05-2011, 10:58 PM   #1
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Default loss of vaccum

Ok guys, been monitoring my compression for a while and constantly refining my tune in MSPNP.

Before turbo 175-170-175-175 psi compression
Stayed that way for a while, 1k miles ago was the last check.

Now I HAVE had a couple pings here and there however I allways backed off immidiatly and took out timing from that MAP range. I had one hell of a solid and safe tune for about a week. Then without warning my idle KPA goes from 25-26 to 33 with no real change in idle speed.

Current compression: 170 150 155 170.

Ive gone over every gasket and seal in the entire intake side of the system. EVERY single one. Twice, if not more.

Checked to make sure the cams were inline.
Ok skipped one tooth on the crank pully *both cams one tooth off*

Didnt fix the problem. Didnt even make a difference.

It dosent burn oil and when I did the old 'squirt some oil in the cylinder and re-test' It only bumped it up 3-4 psi...

There is a VERY SMALL loss in power under boost, however off boost it runs like absolute crap... Checked all my valve clearences, they are all well within Mazda factory spec.

Allways without exception run 91 octane *cali's "best" *
AFRs above 75 kpa allways in the 12.5-10.5:1 range depending on exactly where above 75 kpa it was *more boost=more fuel*
cruise AFR typically 15:1 and never any indication of Detonation

Turbo setup: modified BEGi kit with garrett 2554R. Cast manifold, BEGi #2 intercooler, forge BOV, Rx-7 460cc, MSPnP, LC-1 wideband that is allways calibrated, MAX AIT ever seen during boost was 112 and that cooled off quick once I started moving and got some fresh air under the hood. typically on a 75* day I will see a max of 92-94* under boost after a 15 second pull.

Engine: Stock '00 longblock. No changes made anywhere except to run '95 sensors and control stuffs.

Any Input guys? As is I'm thinking maybe a bent valve or two...

*edit* I should add Ive never run more then 9 PSI and 90% of the time its at the original wastegate controler's 5.5 that creeps to 8.5 psi at redline. All changes in boost tuned for and before I turned up the boost at all I would allways make sure that the area I was aming for was VERY rich and had timing pulled back beforehand.
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Old 05-06-2011, 01:33 AM   #2
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Comp numbers seem to indicate blown HG. I could be wrong.
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Old 05-06-2011, 02:13 AM   #3
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How exactly are you running the car? Do you still have the MAF in there or have you switched over to MAP based tuning? The compression numbers sort of suck, but I would think there's something else at play here.
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Old 05-06-2011, 02:21 AM   #4
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Yeah, AFM removed long ago. Been on MAP since installing MS.
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Old 05-06-2011, 02:26 AM   #5
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Leakdown test. Either HG (rare) or you burned a valve.
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Old 05-06-2011, 02:40 AM   #6
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Thats what I was kinda thinking Damn, now I have to break down and buy a freakin leakdown tester... Yeah, its not making any horrendous noises, not puking stuff out the tail pipe or any of that mess... just stopped pulling vaccum and runs like crap off boost.
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Old 05-06-2011, 03:19 AM   #7
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Based on the cylinders 2-3 being both low it makes sense its a gasket.

But valve sealing issues would do it too.

Dann
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Old 05-06-2011, 11:56 AM   #8
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You're pulling the head either way. Just pull the head. You'll immediately see if it's a head gasket. If not, rebuild the head. No big deal. Your bottom end seems fine.

Last edited by hornetball; 05-06-2011 at 06:53 PM.
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Old 05-06-2011, 05:51 PM   #9
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Easy to say but this is my daily lol. Well time to get that Kawasaki KZ440 ltd I bought for $200 up and running...
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Old 05-06-2011, 06:55 PM   #10
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borrow/rent while u fix?
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