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Junior Charter Member
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Discussion Starter · #1 ·
I,m going to use a Stock 95 5.0 EFI setup with 4 into 4 headers and was wondering what the effects of deleting the EGR valve has. I know the resistor tricks the computor so the light doesn't come on. But what happens with engine timing control? Does O2 verify EGR operation? Are you backing base timing down to compensate for engine detenation?, if so how much? Seems to me that just blocking off the EGR and adding the resistor is not a full solution for getting rid of EGR function. I'm thinking of keeping the EGR and fabricating a tube from the back of the cylinder head. What are your thoughts about this?
 

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Many just keep it. The performance difference is not great and extra maintenance for cleaning is minimal. The EGR function actually improves gas mileage. Which as we all know is of primary importance to Cobra owners


http://en.wikipedia.org/wiki/EGR
 

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Senior Charter Member
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I'm not sure on the 95 strategy, but the A9L strategy simply ignores EGR once it knows it does not work. This in turn keeps it out of the EGR timing tables, so there shouldn't be an issue.

The EGR eliminator will set a code 33 or similar 3 digit code. This may make the Check Engine illuminate. I don't have the CEL, but a friend's truck would turn on the CEL when code 33 was set.

You can have a chip burned to eliminate EGR function. This definitely removes the code setting.
 

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Tropically Twisted
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EGR isn't exactly a bad thing to have. At WOT, the engine stops all operation of it. It only runs at part-throttle, part-load cruise, and helps with fuel economy.

I think you're confused, since in 5.0 engines, the EGR is completely internal to the heads/intake manifold.

The tubes that go to the back of the heads are part of the Thermactor Air Injection system.

HTH,

Will
 

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Willspeed:

Yes, the EGR system runs through the heads and intake, but the EGR valve lives on the back of the EGR spacer, sandwiched between the TB and the upper intake. I eliminated mine, 'cause it's just plain ugly.

I think you are right about the air tubes in the back of the heads; he's confused there.
 

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Discussion Starter · #6 ·
Ok, I realize that the passage in the rear of the heads is for air pump supply to help the cats lite off faster. I should have stated I will not be running the air pump and assocated plumbing. If you remove the crossover tube from the rear of the cylinder heads and start the engine then exhaust will come out the holes. My primary concern is computer stragegy durring part throttle operation, does the computor back down timing if O2 doesnt confirm EGR operation. If base timing is retarded because of removed EGR the the O2 signal doesnt confirm EGR opration and then backs up the timing further, performance may less that desirered, just to clean up the look of the engine. Secondly keeping the EGR wouldn't hurt performance but plumbing into the coated 4into4's,... well I was thinking that the passage at the rear of the head may do just fine for the small volume of exhaust gas needed for EGR operation.
 

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Official OLD GUY
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Matt R

Eliminating the EGR won't effect your power at all . . . fooled the A9L years ago and don't have EGR hooked up at all on FFR3712K. No issues in two years.

Base timing set at 12*BTDC and idle set for 800RPM with E303 cam.

Still getting 22.5 MPG (avg) with 3.73 rear end and T5.

As a side note, I have all the "smog" sensors resistor by-passed (TAD/TAB & carbon canister) and my CEL only lites when I first turn the key on to verify it's working . . . never had a code yet.

Doc
 

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95 is CBAZA strategy. When the EGR is active it looks like it runs a spark adder table(s). It should not remove timing in a noticeable way when the EGR is inactive.

The EGR gas is considered inert. The EGR air is taking up space, but no additional O2 is present. The HEGOs will simply maintain the commanded Air Fuel Ratio. I don't see any special fueling for EGR (doesn't mean it's not there). The EEC will tend to focus on AFR (injector pulsewidth) and work off tables to set timing.

Once the EGR is found to not function the EEC should not utilize any of the EGR modifying tables. It should behave fine.

The 94-95 strategy can tend to ping; its a more emissions focused setup. It tends to be unfriendly towards "calibrated" MAFs with bigger injectors, due to more Load calculation dependence than earlier EEC IV's.
 

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Professional Internet Browser
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All eliminating EGR will do is save a little weight and greatly increase your engine operating temps and NOx emissions because of the lack of cooling effect of the EGR during normal driving. leave it on.
 

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Anyone care to explain how pumping hot exhaust gases (EGR) back into your intake helps "cool" the engine.

The air pump and thermactor bypass hardware help cool the catalytic converter, but I'd like to hear how recirculated hot exhaust gas cools an engine. It is there for emissions, just like the massive exhaust port bump on stock heads.

I've removed the EGR, and all of the air pump/thermactor associated plumbing and hardware with NO effect on operating temperature. I'm running a modified A9L. I've disabled the EGR and Thermactor functions in the EEC by using my TwEECer.
 

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I have a 92 motor and its naked as a jbird... everything has been shi canned except what makes it lite and go... NO PROBLEMS.. and I never have a lite come on.. Oh, I shi canned that to!!!
My computer has never been touched either.
 

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mk 1.5 original
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The primary reason for EGR is to reduce NOX. NOX is formed when combustion temps exceed 1800 deg. By adding inert gas to the charge it reduces the amount of air and fuel in the cylinder = Less energy = less heat. Less fuel = better fuel mileage. It does not really affect the water temp. it works by reducing engine displacement.

chris
 

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FFCobra Fanatic
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Chris is correct. And on 94 and up 5.0L motors, the EGR is plumbed from the back of the haeds to the throttle body, not up through the manifold. I deleted mine because it started to whistle and I could not justify spending any money on it.
 

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Junior Charter Member
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Discussion Starter · #15 ·
It seams that the 93 and older A9L handle EGR system deletion with minimaln problems. The 94-95 CBAZA system sounds like it is more sensitive to EGR mods. Since I'm using a stock 95 5.0 w/4into4,s and the normal routing of exhaust gas is from the shorty header tube, I was thinking of using the crossover tube on the back of the heads and modifing to rout exhaust gas to EGR valve. Cleaning up the apperance of the engine by removing the EGR doesn't seam warrented in my case. Just for conversation, heres a Chrysler fuel calculation; RPM over Max RPM (X) MAP over Baro (X) EGR Flow (X) TPS (X) ECT (X) IAT (X) Sensed B+ (X) Up O2 (X) ST (X) LT (X) Purge Vapor Ratio = Pulse Width. So you can see that EGR has a fairly large input in the equation. I don't know how much weight the 94-95 CBAZA EGR strategy has, more than likly not worth removing on a stock engine set up. Base timing would need to be backed down to far to be worth while.
 

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mk 1.5 original
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I am running a 95’ GT driveline with the CBAZA J4J1 strategy. I use the tweecer to turn the EGR off for my performance tunes. And it’s on for my emissions tune for Passing the emissions test. I welded a bung into my shorty header so everything fits nice. I am sure you could do the same with the 4 into4s.

As far as what other calculations are made during EGR operation there are a lot of scalars, Tables and functions that start off with EGR.

The main reason I turn it off is that it Is easier to tune. Making accurate timing predictions and changes. Important with the CBAZA strategy because in its stock form the timing is aggressive in the Mid load tables. This with the relatively lean AFR causes that dreaded SN-95 ping.

chris
 

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Junior Charter Member
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Discussion Starter · #17 ·
Chris,
Thanks for the info, It seams I'm going to keep my EGR system. I've heard mention of "Tweecer" but never have ck'ed into it. Is it add on controller or replacement for the EEC module that allows you to set parameters like timing, EGR, exc.? I'll look into it soon.
 
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