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DIY Turbo Discussion greddy on a 1.8? homebrew kit?

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Old 03-26-2009, 10:15 PM   #1
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Default Low vac problem tried everything.

Ok I have had a persistant and annoying low vacuum condition that I cannot figure out. While the vacuum is low the car has zero power and literally cannot pull out into traffic.

Its not a leak anywhere in the intake system. I hooked it up to a smoke machine and pumped in smoke for several minutes and no smoke leaked out.
I have checked just about every vac line in the car. Sprayed carb fluid everywhere blah blah.

Today just for fun I took off the entire intercooler setup and discovered my check valve on my DO WI kit was NOT working. A few oz of water came out of the charge pipe.

I was happy and figured that was the problem so I threw the stock plastic intake system on. This made pretty much zero difference. What is strange is sometimes it will idle with a normal vac of 19/20 but then it will lower to 14. If you rev the car and let it go back to idle it will go back to 19/20 and then sometimes the vac will go lower.

When the car is cold it runs like total ****. Zero power, you can almost out walk it while its floored. Sometimes giving the car some gas will make the revs go LOWER instead of higher ha!

I am going nuts over this while situation. Anybody have any advice? I tried on miata.net a few months ago and that when nowhere with everybody telling me to check my intercooler pipes when I told them several times they have been checked.

It may be the crack nose again, but I don't want to take off that crank bolt again. There is a healthy amount of loctite down there and I am sure it will be a massive bitch to take off again. It sucks that there is no good method to tell if the alignment has slipped due to the crank nose getting yoked out.

Ok here is my car's setup. I know its a greddy kit not DIY, but I consider the POS kit to be DIY anyways.

1990 miata (loctite fixed) Checked to see if the crank nose is fucked (again), I checked to the best of my ability and it's fine. Also the TB has not slipped a tooth or anything.

Greddy with Starion IC (disconnected) @ 6psi

TurboXS POS BOV (Disconnected)

Devils Own WI (Leaking check valve. Compleatly Disconnected.)

Thanks guys for any ideas.
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Old 03-26-2009, 10:48 PM   #2
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Short nose crank failure? Sounds like it might be the cause. The low vacuum and lack of power could be a timing issue.


Opps. You said you checked it. Have you thrown a timing light on the car?
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Old 03-26-2009, 10:50 PM   #3
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Do a compression test I had low vac and it was cuz I had bent rods and also check timing.
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Old 03-26-2009, 11:08 PM   #4
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can check crank nose by looking at your timing. If your mark is off, most likely it's shifted. You can also count t-belt teeth at TDC to the cam gears to see if it slipped. Or you could check your compression as well.

Do you have WBO2? Also extreme rich condition can cause a bog. Sounds more like timing, though. Otherwise it could be piston rings.
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Old 03-26-2009, 11:09 PM   #5
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can check crank nose by looking at your timing. If your mark is off, most likely it's shifted. You can also count t-belt teeth at TDC to the cam gears to see if it slipped. Or you could check your compression as well.

Do you have WBO2? Also extreme rich condition can cause a bog. Sounds more like timing, though. Otherwise it could be piston rings.
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Old 03-26-2009, 11:39 PM   #6
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Yeah it looks like the next step is to do a compression test or leakdown.

What is the proper procedure to disable spark and fuel to do the test. I got the gauge. I can do the compression test right now, I am just unsure how to disable fuel/spark.

I do not have a wideband but I have monitored my narrowband and it seems to go full rich under boost, but other than that seems normal.

Maybe its time for a 99 motor or something?

EDIT: my timing mark was not off and the belt has not slipped. I counted the teeth. Checking the TB to see if the crank nose has failed does not work in my experiance. The reason is that when you turn the motor by hand with a ratchet you will move the key back into allignment and everything will appear to be fine, but it will slip back out when the crank moves the pulley.

Anybody got a 1.8L they wanna sell me? haha
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Old 03-27-2009, 12:22 AM   #7
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Is it possible you have a restricted exhaust?

Ron
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Old 03-27-2009, 12:42 AM   #8
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Quote:
Originally Posted by Alta_Racer View Post
Is it possible you have a restricted exhaust?

Ron
Thought of that, I semi unbolted the downpipe and it didn't change anything as far as I could tell.
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Old 03-27-2009, 06:13 AM   #9
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Ok I did a compression test but there was a few problems. The gauge I used had like a 1/8 inch screw in part. A 1/8 inch socket wont fit down the spark plug well so I had to tighten it by hand.

I warmed up the engine blah blah, had the throttle wide open blah blah all for plugs removed blah blah.

Every cyc put around 150-155 with this gauge. I think it might be low because of how I could not get it 100% tightened due to not being able to get a socket down there. The guage was clearly leaking, but I figure if all 4 cyc are over 150 compression with a leaking gauge compression may not be a problem.

What do you guys think?
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