Cats or no cats??? - Ford Mustang Forum
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post #1 of 19 (permalink) Old 09-23-2017 Thread Starter
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Cats or no cats???

I'm starting plans for mods on my '87 GT.I can go into detail of the mods if needed,but my main question is if I'm eliminating the egr system,and the smog system,should I bother keeping the cats??

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post #2 of 19 (permalink) Old 09-23-2017
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my '66 GT350 likes cats

Z

PS if you eliminate the smog equipment, can your car pass any state inspection ? or is it a race car?

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Galaxie 500
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post #3 of 19 (permalink) Old 09-24-2017 Thread Starter
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I'm in Ontario Canada,'87 and older do not require an emissions test,but that being said there are fines for removing smog equipment,but that's only if you are doing something stupid and give the police some reason to inspect and/or fine you.
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post #4 of 19 (permalink) Old 09-24-2017
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Quote:
Originally Posted by Robs87GT5.0 View Post
I'm starting plans for mods on my '87 GT.I can go into detail of the mods if needed,but my main question is if I'm eliminating the egr system,and the smog system,should I bother keeping the cats??
The egr valve is a good thing to keep.When the egr valve is opened,the exhaust gasses actually helps lower combustion chamber temps.The computer leans the fuel mixture and adds timing advance,when the egr valve is open,which can help with part throttle performance and fuel mileage (possible but not likely)
When a egr system fault occurs,the computer deletes (turns off) egr function,which sets the fuel mixture and timing advance to normal.

If you remove the smog (thermactor) system,the cats will need to be removed because they'll clog and fail,if they dont receive fresh air from the smog pump.There are 4 cats on the Foxbody.The 2nd cat on each bank has platinum & palladium inside it.Fresh air from the smog pump is combined with those metals to create the catalytic reaction.
Make sure you plug all vacuum hoses that were connected to any components you removed,because a vacuum leak will occur if you forget.
Some codes will be present once you delete the egr & smog system.These are called Soft Codes.They wont cause the check engine light to come on and they wont cause driveability issues either,but if you dont wanna see those codes in a koeo/koer test,resistors can be used to prevent those codes.

The following link details the smog and egr system.
Scroll to post #10,once the link opens.

https://www.stangnet.com/mustang-for...-to-it.477938/
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1991 Mustang lx
D.S.S. 342ci {10.5:1}
TFS 190cc + track heat
Lunati 61011 .549".565"
Pro-M 76mm maf
Jetronic 30lb inj
QA1 Coilovers
17" Weld ProStar XP's
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post #5 of 19 (permalink) Old 09-24-2017 Thread Starter
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Thanks for the info,very helpful indeed.I will have to figure out an alternative to the egr,I'm going to be using a non egr explorer intake with GT40P heads.
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post #6 of 19 (permalink) Old 09-24-2017
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Quote:
Originally Posted by Robs87GT5.0 View Post
Thanks for the info,very helpful indeed.I will have to figure out an alternative to the egr,I'm going to be using a non egr explorer intake with GT40P heads.
Forget the egr valve then.The ports arent present in the intake to run it.

1991 Mustang lx
D.S.S. 342ci {10.5:1}
TFS 190cc + track heat
Lunati 61011 .549".565"
Pro-M 76mm maf
Jetronic 30lb inj
QA1 Coilovers
17" Weld ProStar XP's
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post #7 of 19 (permalink) Old 09-24-2017
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Speed density car? Dont even run a throttle body spacer. Feed the beast!!!! Replace those cats with some nice straight pipe, take off the smog pump completely and charcoal canister. Then just simply run a shorter belt.

1993 LX hatch. Black nose, white hood, black fenders blue body, originally red. Survived hurricane katrina. Peeling hooters bumper sticker, hatch doesn't close right, driver's side door handle is broken but works(you know what I'm talkin' about haha, hell yeah!) Next generation Rat Rod living in the present. 331 stroker, backed up by a g-force T5. Built(slowly torn apart for weight reductions) for autocross and making rich people feel bad. SKOOOOOOOOOOOWEEEEEEEEEE! Yeehaw!
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post #8 of 19 (permalink) Old 09-24-2017 Thread Starter
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I'm doing a MAF swap but yes it's presently SD. Do you not have to keep the charcoal canister to avoid gas fumes under the hood?
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post #9 of 19 (permalink) Old 09-24-2017
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Long story short, you dont need a charcoal canister. Lol

1993 LX hatch. Black nose, white hood, black fenders blue body, originally red. Survived hurricane katrina. Peeling hooters bumper sticker, hatch doesn't close right, driver's side door handle is broken but works(you know what I'm talkin' about haha, hell yeah!) Next generation Rat Rod living in the present. 331 stroker, backed up by a g-force T5. Built(slowly torn apart for weight reductions) for autocross and making rich people feel bad. SKOOOOOOOOOOOWEEEEEEEEEE! Yeehaw!
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It won't make much of a difference either way. No cats will be a tad louder and might be a tad smellier.
Performance wise you won't be able to tell the difference really.
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Quote:
Originally Posted by zray View Post
my '66 GT350 likes cats

Z

PS if you eliminate the smog equipment, can your car pass any state inspection ? or is it a race car?

Nice looking cat I have 4. I don't have cats on my car I don't like cleaning
off the paw prints. One of my cats use to use one of my tires for a scratching post.
not good either.
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Quote:
Originally Posted by Robs87GT5.0 View Post
I'm doing a MAF swap but yes it's presently SD. Do you not have to keep the charcoal canister to avoid gas fumes under the hood?
Yes youll have gas fumes,if you remove the charcoal canister.
If you want to test this scenerio,disconnect the hose from the canister,thats coming from the fuel tank,and leave it open.Disconnect the other hose from the canister,thats coming from the purge valve,and plug it so you wont create a huge vacuum leak.
Take the car for a test drive/check for fumes....
Park the car at idle/check for fumes....
Shut the engine off/check for fumes....

BTW-most people that delete the charcoal canister delete the purge valve too.Some people that delete the charcoal canister & purge valve will then connect the hose (thats coming from the fuel tank) directly to the intake vacuum fitting,instead of leaving it open to atmosphere.That wont work.It'll cause the engine to run rich due to the fuel vapors being constantly ingested by the intake.Thats the reason why a canister and purge valve is used,so the vapors can be stored until the computer purges them into the intake.They are normally purged right after startup and during cruise mode.Purging them during cruise richens the fuel mixture.This causes the o2 sensors to trigger a rich condition,which then causes the ecm to lean (reduce) the fuel mixture.A lean mixture at cruise is better than a rich mixture.
When the engine is shutdown,vapors flow into the canister and stay there until the engine is fired up again.

Its Imperitive to leave that hose open to atmosphere,once you delete the components listed above,because thats what allows those vapors to escape now.Wherever you decide to locate that vacuum hose is ultimately the area where youll experience the fumes.
The only other method you could use to vent the tank,if you wanted to plug the vacuum hose,would be to install a vented gas cap,but the fumes are still gonna be present.They'll just be relocated from the engine bay to the gas cap door.lol.

**EDIT/ADDITION**
The oem gas cap has a valve built into it.It acts to allow air into the fuel tank to replace the fuel as it is used.
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1991 Mustang lx
D.S.S. 342ci {10.5:1}
TFS 190cc + track heat
Lunati 61011 .549".565"
Pro-M 76mm maf
Jetronic 30lb inj
QA1 Coilovers
17" Weld ProStar XP's

Last edited by wbrockstar; 09-26-2017 at 09:21 PM.
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Quote:
Originally Posted by SmokeyJo5.0 View Post
Speed density car? Dont even run a throttle body spacer. Feed the beast!!!! Replace those cats with some nice straight pipe, take off the smog pump completely and charcoal canister. Then just simply run a shorter belt.

He'll have to run an egr spacer,with a block off plate over the egr holes,or buy an egr delete plate.One of these has to be present in order to mount the throttle cable bracket.The delete plate is a thin plate with the throttle bore plus tabs for mounting the throttle cable bracket.Since he already has an egr spacer,thats the cheapest route.

1991 Mustang lx
D.S.S. 342ci {10.5:1}
TFS 190cc + track heat
Lunati 61011 .549".565"
Pro-M 76mm maf
Jetronic 30lb inj
QA1 Coilovers
17" Weld ProStar XP's
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Quote:
Originally Posted by squekster View Post
Nice looking cat I have 4. I don't have cats on my car I don't like cleaning
off the paw prints. One of my cats use to use one of my tires for a scratching post.
not good either.
The GT350 still has the factory original paint, 51 years old. So it's seen a lot worse than cat hair or paw prints. Like dried beer from numerous "winners circle" drenching after street drag racing in Juarez Mexico some 44-48 years ago, and a few west Texas sand storm etchings in the paint.

But I get your point. Everybody has their own way to treat their car(s).

Z


Galaxie 500
'65 K code Mustang
& a few '66 GT350's (1970-2012)
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Quote:
Originally Posted by zray View Post
The GT350 still has the factory original paint, 51 years old. So it's seen a lot worse than cat hair or paw prints. Like dried beer from numerous "winners circle" drenching after street drag racing in Juarez Mexico some 44-48 years ago, and a few west Texas sand storm etchings in the paint.

But I get your point. Everybody has their own way to treat their car(s).

Z
Good thing it was 44-48 years ago.Racing,or doing anything else,in Juarez Mexico nowadays will get you killed.Its got bad over there.


1991 Mustang lx
D.S.S. 342ci {10.5:1}
TFS 190cc + track heat
Lunati 61011 .549".565"
Pro-M 76mm maf
Jetronic 30lb inj
QA1 Coilovers
17" Weld ProStar XP's
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