EGR valve orifice washers?
Thread Starter
Race Director
Joined: Jan 2000
Posts: 12,399
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From: San Jose CA
EGR valve orifice washers?
Anyone work with one of these kits from standard motor?
It's basically a washer pack and it restricts the size of the orifice.
Obviously, this will change the relationship between back pressure and valve movement.
So, should I err on the side of a larger or smaller washer ID? My car has significantly less backpressure than a stock 78 Corvette would, in any configuration, so it'd be nice to do some "tuning" here.
It's basically a washer pack and it restricts the size of the orifice.
Obviously, this will change the relationship between back pressure and valve movement.
So, should I err on the side of a larger or smaller washer ID? My car has significantly less backpressure than a stock 78 Corvette would, in any configuration, so it'd be nice to do some "tuning" here.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Read up on EGR. You are polluting the A/F mixture with burnt exhaust gas. Which in theory allows a motor to run lower octane gas without pre-ignition. Your L-82 is already pretty low compression.
If you can run 87 gas with it blocked off do it. I would retard the total timing before i would use EGR
If you can run 87 gas with it blocked off do it. I would retard the total timing before i would use EGR
Racer
Joined: Apr 2006
Posts: 477
Likes: 43
From: Millbrae California
The EGR is used to lower the NOx emmisions, the valve should come with a chart that tells you which washer to use but the smaller the hole will be better the better for driveability. If you are in an area that checks for exhaust emmisions via a smog check and have a high NOX reading you can use the washer size as a tuning aid or if you are not in an area that does emmisions testing for your car you can use a small washer or leave it disconnected but FYI, it is illegal to disconnect or tamper with any emmisions device under federal law even if your area does not check for exhaust emmisions
Thread Starter
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
Yeah, I just failed high on NOx, so I'd like to set it up to minimize the NOx as much as possible. Not sure if the old valve failed or not. Plan on lowering the timing to the lowest the spec range will allow and hopefully squeeking through. Car is running 91, which is more than enough for the given modifications it has.
Too high an octane wouldn't raise NOx, would it?
Too high an octane wouldn't raise NOx, would it?
Race Director
Joined: May 2006
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From: Dayton, Ohio
Years ago when our area had testing,rule of thumb when testing was , lowest octane fuel , cover a portion of radiator to keep engine temp high and add 1oz alcohol per gal of fuel in tank. I'm sure our requirements were not as strict as CA.
Racer
Joined: Apr 2006
Posts: 477
Likes: 43
From: Millbrae California
A high NOx reading would most likely be from too much ignition advance (too muxh mechanical or too much from the vacuum advance for the octane of the gasoline). It can also be from too high of a compression ratio, carbon build up in the combustion chamber or a VERY lean a/f mixture. If the CO reading is lower than 0.2% the air pump disabled (if used) and the readings taken in front of the catalitic convertor (if used).
I would suggest checking the NOX reading with the vacuum advance disconnected and limit the total mechanic timing to 34 degrees at 3-3600 rpm. If it is lower limit the vac advance to 10 degrees and see if it is still lower.
I hope this helps Henry @ olescarb
I would suggest checking the NOX reading with the vacuum advance disconnected and limit the total mechanic timing to 34 degrees at 3-3600 rpm. If it is lower limit the vac advance to 10 degrees and see if it is still lower.
I hope this helps Henry @ olescarb
