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Subject:
Re: EGR Valve on L98
From: Bob I <birelan1(at)yahoo.com>
Subject: Re: EGR Valve on L98
Lines: 58
Date: Sun, 09 Sep 2007 09:02:27 -0500
NNTP-Posting-Host: 66.188.214.61
Bytes: 3914
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At least on the `95, the ECU command to the EGR control valve and if it
doesn`t "see" the expected manifold pressure change, sets the check
engine light. As for "blocking" it off, well the purpose is to reduce
the amount of "excess o2" and reduce combustion chamber temperatures to
preclude the formation of NOX, during specific operating conditions
(primarily LOW output levels, meaning cruise and small throttle
openings) Visualize not very much fuel being injected to need available
oxygen. So they replace some of the pumped volume with a gas that has
the oxygen removed. Cooling the intake charge is good for maximizing the
amount of oxygen available for WOT conditions, but please tell me how
much time you spend there!!! If blocking off the recirculation resulted
a 20% increase, I would surmise there was a lot more "broken" and not
functioning on that Ford than just the EGR valve controls. Given CAFE
fines, I doubt the manufacturer is going to "give up" 20% gas mileage to
reduce NOX emission with an EGR valve.
Eugene Blanchard wrote:
> My answer is a little bit off topic but it concerns the egr valve. Don`t
> know where you live but if you don`t have yearly smog tests to pass. I
> suggest you block off the egr valve.
>
> Now I don`t have a 90s Vette but bear with me. On my 92 Ford Ranger, the
> computer controls the EGR valve position using vacuum, then there`s an EGR
> position sensor to verify that its working. So disconnecting anything
> brings up the Check Engine light and a trouble code.
>
> To get around the computer, I made a metal plate which matched the outline
> of the EGR valve gasket and installed it with the gasket. The EGR position
> sensor reports that the EGR is working and no error codes!
>
> Why block off the EGR? It recirculates the exhaust gas back into the intake
> manifold to reduce NOx emissions. Ideally, you want the coolest air in the
> intake, the EGR adds extremely HOT exhaust gas in. And it screws up your
> fuel/air mixture - rather than clean outside air, you have hot CO gas
> coming back in. The result is less power and poorer gas mileage.
>
> Blocking off my EGR valve increased my overall hp (every little bit counts
> on a 2.3l ford) and increased my gas mileage by 20% around town.
>
> http://www.cadvision.com/blanchas/Ranger/egr.html
>
> Comments?
>
> gjt wrote:
>
>> `90 L98 Vert. Service Engine Light would come on after about 15 minutes of
>> driving. Any time I would turn off the engine, it would reset. Comes
>> right
>> back on when it warms up. Took it to local Firestone. They said my EGR
>> valve was badly stuck. Said if I continue to drive as is, the Cats would
>> eventually load up with Carbon. They want $450!!! I think this is a bit
>> excessive. Is there something about an L98 that makes this a difficult
>> job? From doing some searches, looks like the going rate for the valve is
>> around $70.
>>
>> Thanks for your input.
>> gjt
>
From: "Butcher" <butcher57(at)swbell.net>
Subject: Re: EGR Valve on L98
Lines: 49
NNTP-Posting-Host: 67.67.218.1
Date: Sun, 9 Sep 2007 09:32:28 -0500
Bytes: 3779
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"Eugene Blanchard" <blanchae(at)telus.net> wrote in message
news:QhLEi.26498$Pd4.10951(at)edtnps82...
> My answer is a little bit off topic but it concerns the egr valve. Don`t
> know where you live but if you don`t have yearly smog tests to pass. I
> suggest you block off the egr valve.
>
> Now I don`t have a 90s Vette but bear with me. On my 92 Ford Ranger, the
> computer controls the EGR valve position using vacuum, then there`s an EGR
> position sensor to verify that its working. So disconnecting anything
> brings up the Check Engine light and a trouble code.
>
> To get around the computer, I made a metal plate which matched the outline
> of the EGR valve gasket and installed it with the gasket. The EGR position
> sensor reports that the EGR is working and no error codes!
>
> Why block off the EGR? It recirculates the exhaust gas back into the
> intake
> manifold to reduce NOx emissions. Ideally, you want the coolest air in the
> intake, the EGR adds extremely HOT exhaust gas in. And it screws up your
> fuel/air mixture - rather than clean outside air, you have hot CO gas
> coming back in. The result is less power and poorer gas mileage.
>
> Blocking off my EGR valve increased my overall hp (every little bit counts
> on a 2.3l ford) and increased my gas mileage by 20% around town.
>
> http://www.cadvision.com/blanchas/Ranger/egr.html
>
> Comments?
>
Since my LT-4 doesn`t have an EGR valve because of additional cam overlap
I`m assuming the valve is supposed to close when rpm/throttle increases
(vacuum decreases, or should I say manifold pressure goes up), so it`s
`active` only with little or no throttle. And since the ECU controls the
mixture thinking the EGR is working I`m wondering if the mixture will be
richer because of the blockoff (instead of just a cooler charge) --
enriching mixture is usually a good thing for power and throttle off/on
transition with these newer cars that run so lean, and more power means less
throttle at any given power setting so mileage would go up a little maybe.
But what about carbonizing the cat. over time because of the richer mixture?
Maybe the fix will cause an expensive repair later on if the cats. are left
in place and block up?
Just a thought...
Butcher
`96 LT-4 CE
From: "gjt" <gjtooley(at)bellsouth.net>
Subject: Re: EGR Valve on L98
Lines: 62
Date: Sun, 9 Sep 2007 09:46:55 -0500
Bytes: 3808
________________________________________________
Yep, that`s what the guy at Firestone told me. If left alone and not
corrected, the long term effect is loading up the CATs with carbon. He said
the CATS on an L98 are not cheap.
"Butcher" <butcher57(at)swbell.net> wrote in message
news:cuTEi.2105$ZA5.770(at)nlpi068.nbdc.sbc.com...
>
> "Eugene Blanchard" <blanchae(at)telus.net> wrote in message
> news:QhLEi.26498$Pd4.10951(at)edtnps82...
>> My answer is a little bit off topic but it concerns the egr valve. Don`t
>> know where you live but if you don`t have yearly smog tests to pass. I
>> suggest you block off the egr valve.
>>
>> Now I don`t have a 90s Vette but bear with me. On my 92 Ford Ranger, the
>> computer controls the EGR valve position using vacuum, then there`s an
>> EGR
>> position sensor to verify that its working. So disconnecting anything
>> brings up the Check Engine light and a trouble code.
>>
>> To get around the computer, I made a metal plate which matched the
>> outline
>> of the EGR valve gasket and installed it with the gasket. The EGR
>> position
>> sensor reports that the EGR is working and no error codes!
>>
>> Why block off the EGR? It recirculates the exhaust gas back into the
>> intake
>> manifold to reduce NOx emissions. Ideally, you want the coolest air in
>> the
>> intake, the EGR adds extremely HOT exhaust gas in. And it screws up your
>> fuel/air mixture - rather than clean outside air, you have hot CO gas
>> coming back in. The result is less power and poorer gas mileage.
>>
>> Blocking off my EGR valve increased my overall hp (every little bit
>> counts
>> on a 2.3l ford) and increased my gas mileage by 20% around town.
>>
>> http://www.cadvision.com/blanchas/Ranger/egr.html
>>
>> Comments?
>>
>
> Since my LT-4 doesn`t have an EGR valve because of additional cam overlap
> I`m assuming the valve is supposed to close when rpm/throttle increases
> (vacuum decreases, or should I say manifold pressure goes up), so it`s
> `active` only with little or no throttle. And since the ECU controls the
> mixture thinking the EGR is working I`m wondering if the mixture will be
> richer because of the blockoff (instead of just a cooler charge) --
> enriching mixture is usually a good thing for power and throttle off/on
> transition with these newer cars that run so lean, and more power means
> less throttle at any given power setting so mileage would go up a little
> maybe. But what about carbonizing the cat. over time because of the richer
> mixture? Maybe the fix will cause an expensive repair later on if the
> cats. are left in place and block up?
>
> Just a thought...
>
> Butcher
> `96 LT-4 CE
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