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Yes, it has a car seat
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1,884 Posts
Discussion Starter #1
I see on the f-body ls1 sites all of the time people removing the exhaust gas recirculation system and the air injection regulator. Looking through Helms I'm not finding either of these systems listed. Does our car have these?
Dan
 

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13 year owner
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16,384 Posts
And even if we had them I wouldn't remove them as they have no HP gains.

EGR only injects exhaust gases into the intake streams in part throttle applications. Under full throttle the PCM overrides it "off" anyway.

Secondary A.I.R. system is only on up to 240 seconds or until the PCM goes into closed loop segment. It's sole purpose is to help "light off" the cats sooner in order to get the PCM into closed loop quicker. Once again, since it's off after 240 seconds of operation (at the longest), it won't have any HP gain by removing it.

I have both systems fully operational and went to great lengths to add back my EGR system on my Camaro when I installed the LS6 intake (since mine is a '98). There is no gain to be had by removing these systems.
 

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May I quote you on that?
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22,046 Posts
I'm wondering how they got the NOX numbers down without an EGR. Do combustion temps run high on LS1's sans EGR or have they compensated in other ways?
 

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13 year owner
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All combustion temps run high, otherwise they wouldn't have put it on. ;) That's one of the reasons for EGR systems on any car.

On the '01+ cars without EGR, I believe they changed the cam profile's ramp speeds to accomodate.
 

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13 year owner
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16,384 Posts
Here is a little information from GM that I posted on LS1Tech awhile back. It is specifically on the EGR system for LS1's (and most GM's in general).

Purpose

An Exhaust Gas Recirculation (EGR) system is used in order to lower Oxides of Nitrogen (NOx) emission levels. The EGR system accomplishes this by feeding small amounts of exhaust gas back into the combustion chamber. High combustion temperatures cause NOx. Combustion temperatures are reduced when the air/fuel mixture is diluted with the exhaust gases.

Operation

(1) Cap-Sensor
(2) Sensor-EGR Pintle Position
(3) Pole Piece-Primary
(4) Bobbin and Coil Assembly
(5) Sleeve-Armature
(6) Valve-Pintle
(7) Armature and Base Assembly

The EGR valve is designed to accurately supply exhaust gases to the engine without the use of intake manifold vacuum. The EGR valve controls the exhaust flow into the intake manifold from the exhaust manifold through an orifice with a PCM controlled pintle. The PCM controls the pintle position using inputs from the Engine Coolant Temperature (ECT) sensor, the Throttle Position (TP) sensor, and the Manifold Absolute Pressure (MAP) sensor. The PCM commands the EGR valve in order to supply the correct amount of exhaust gas recirculation for the current engine operating conditions. This can be monitored on a scan tool as the Desired EGR Position.

The PCM monitors the position of the EGR valve through a feedback signal. The PCM supplies a 5.0 volt reference and a ground to the EGR valve. A voltage signal representing the EGR valve pintle position is sent to the PCM from the EGR valve. This feedback signal can also be monitored on a scan tool and is the actual position of the EGR pintle. The Actual EGR Position should always be near the commanded or Desired EGR Position.

The EGR valve is usually activated under the following conditions:

- The engine is warm.
- The engine is above the idle speed.


Diagnosis

(1) Linear EGR Valve
(2) Exhaust Gas
(3) To Cylinders
(4) Pintle

Too much EGR flow causes any of the following conditions to occur:

- The engine stalls after a cold start.
- The engine stalls during closed throttle conditions.
- The vehicle surges during a cruise condition.
- A rough idle.
- A DTC P0300 (misfire detected).

Too little or no EGR flow allows the combustion temperatures to increase. This causes the following symptoms:

- Spark knock (detonation)
- Engine overheating
- Emission test failure
- DTC P0401
- Poor fuel economy

The EGR flow diagnosis is included in the DTC P0401 diagnostic table. The EGR pintle position and the EGR valve control circuit diagnosis are covered in DTCs P0404, P0405, and P1404. Go to the appropriate DTC table for diagnosis if an EGR diagnostic trouble code is stored
 
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