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| no egr valve | |
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| Tweet Topic Started: Feb 22 2012, 10:54 AM (2,052 Views) | |
| ernrose | Feb 22 2012, 10:54 AM Post #1 |
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New Member
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91 geo metro has no egr valve, does this causing a burnt valve issue, should i replace the intake with a egr unit |
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| Mikemetro | Feb 22 2012, 11:00 AM Post #2 |
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Your 91 didn't come with one. I believe in order to do that you would need new harness and ecu from 92+ |
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| idmetro | Feb 22 2012, 11:33 AM Post #3 |
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Many Metros out there without an EGR valve - I am not aware of any anectdotal evidence suggesting they burn valves any faster or more frequently than engines with the EGR valve. Mostly it seems to come down to maintenance - If you have an EGR valve keep it and the passageways clean, if you don't then don't worry, regular oil changes (with decent oil - great debate on what constitutes "good oil" most agree on regular change intervals), use good fuel or at least run a good fuel system cleaner through on a regular basis. Basically take care of your ride! |
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| ernrose | Feb 22 2012, 11:39 AM Post #4 |
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New Member
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well, you guess that the engineer finally figure out that the 91's was burning a valve and designed the 92's accordingly. compression is 150/75/0.. i see the 0 is a mushroomed on the exhaust valve but the 75 i don't see anything obvious. what's considered strong compress/ medium compress/ low compression #'s to kinda give me a idea of rebuild time is near. |
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| idmetro | Feb 22 2012, 11:51 AM Post #5 |
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Factory fresh is 200 with factory minimum IIRC being 156 but many members have run down much closer to 100 psi (with greatly reduced performance of course but they still run...) You will definitely know it's time for a rebuild as you watch performance fade away, fuel mileage go down and oil consumption go up. Much more important than the actual compression number is that all 3 cylidners be equal or nearly equal - the 3 cyl is already out of balance no need making it worse. |
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| ernrose | Feb 22 2012, 01:50 PM Post #6 |
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New Member
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thanks, for your infro. |
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| Bad Bent | Feb 22 2012, 02:15 PM Post #7 |
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Facetious Educated Donkey
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My '91 has no issues without the EGR. It is probably running a little on the cold side anyway.Here is the wiki on EGR: The exhaust gas, added to the fuel, oxygen, and combustion products, increases the specific heat capacity of the cylinder contents, which lowers the adiabatic flame temperature. In a typical automotive spark-ignited (SI) engine, 5 to 15 percent of the exhaust gas is routed back to the intake as EGR. The maximum quantity is limited by the requirement of the mixture to sustain a contiguous flame front during the combustion event; excessive EGR in poorly set up applications can cause misfires and partial burns. Although EGR does measurably slow combustion, this can largely be compensated for by advancing spark timing.* The impact of EGR on engine efficiency largely depends on the specific engine design, and sometimes leads to a compromise between efficiency and NOx emissions. A properly operating EGR can theoretically increase the efficiency of gasoline engines via several mechanisms: Reduced throttling losses. The addition of inert exhaust gas into the intake system means that for a given power output, the throttle plate must be opened further, resulting in increased inlet manifold pressure and reduced throttling losses. Reduced heat rejection. Lowered peak combustion temperatures not only reduces NOx formation, it also reduces the loss of thermal energy to combustion chamber surfaces, leaving more available for conversion to mechanical work during the expansion stroke. Reduced chemical dissociation. The lower peak temperatures result in more of the released energy remaining as sensible energy near TDC, rather than being bound up (early in the expansion stroke) in the dissociation of combustion products. This effect is minor compared to the first two. It also decreases the efficiency of gasoline engines via at least one more mechanism: Reduced specific heat ratio. from http://en.wikipedia.org/wiki/Exhaust_gas_recirculation *That line about advanced spark timing is why it is generally recommended to bump the timing from the factory 5-6o BTDC to 8-10o BTDC. |
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| ernrose | Feb 22 2012, 06:28 PM Post #8 |
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New Member
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uuuuhhh thanks, 8-10deg... what do you think about using chrome or stainless steel valves and are they available |
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| Bad Bent | Feb 22 2012, 07:12 PM Post #9 |
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Facetious Educated Donkey
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Oh, yeah. Try: geometroforum.com/3Tech G10 Hand polished SS Set of 6 valves $75 Exhaust only $40 A rebuild kit is $115 with hand polished SS valves. ![]() 3Tech has lots of nice stuff and I have his street/race cam plus +10 deg. cam gear. I don't have a link on chrome valves. OEM valves would be from http://www.store.partsdinosaur.com/page17.html or http://www.rockauto.com/ |
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| ernrose | Feb 22 2012, 07:17 PM Post #10 |
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i imagine the ss valves are the strongest,thanks man.. |
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| ernrose | Feb 23 2012, 01:24 PM Post #11 |
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what if i drill/tap a hole in the exhaust manifold that doesn't have a egr valve and channel a tubing from there to the exhaust piping to relieve the exhaust valve pressure |
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| snowfish | Feb 23 2012, 02:04 PM Post #12 |
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Basic GearHead
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The EGR does not relieve exhaust pressure. In simple terms it just directs some exhaust gas to the intake. And it only draws off of one cylinder. I highly doubt that the EGR, plugged or not, causes burnt valves. Spinning at 3000rpm+ for 150,000 miles causes burnt valves and more. A clean and functioning EGR allegedly improves fuel economy and reduces emissions. In my opinion, the jury is still out on that one. My Wife's 93 seems to run smoother after the EGR was cleaned. But that could be placebo effect too. If you want to relieve exhaust pressure, just run a 2 inch exhaust from the manifold to the back. Let it breath! But that's a subject prone to controversy as well.
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| Bad Bent | Feb 23 2012, 09:23 PM Post #13 |
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Facetious Educated Donkey
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Let's not forget mwebb's chant about dogsnit oil causing burnt valves - IIRC Look at this Single POST #5. And of course the chant; "the minimum specification MUST be ACEA A3 B3 - B4" IMHO, adding a header, flow through Cat. and glasspack seemed to reduce some back pressure and "free up some horses." maas will make a header with an EGR port if so ordered. http://geometroforum.com/pages/headers Spend at least $175+shipping on a new header rather than clean out the OEM header EGR channel works for moi.
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| Cobb | Feb 23 2012, 10:28 PM Post #14 |
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BANNED
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I disconnected the egr on my Honda Insight to see what would happen. I ended up loosing 15mpg and after 70 miles or so got a check engine light. So, it helped mpg, but it felt like it had 3 more lbs of tq with it disconnected. Of course back in my day we stuck BBs up the vacuum hose so it wouldnt open. 100psi? I knew a guy who drove his v8 truck that had 75psi compression test. |
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| Woodie | Feb 24 2012, 07:25 AM Post #15 |
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THIS
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It is probably running a little on the cold side anyway.

In simple terms it just directs some exhaust gas to the intake.
And it only draws off of one cylinder.
Spinning at 3000rpm+ for 150,000 miles causes burnt valves and more.
In my opinion, the jury is still out on that one.
But that could be placebo effect too.
3:31 AM Jul 11