cat converter causing lower boost?

Awyman18 · 07-24-2011, 01:58 PM

So...I was driving my 1990 toyota supra turbo, and my friend who was driving behind me said that he could smell rotten eggs. So I'm guessing the cat is bad. Also, I'm only boosting around...5lbs..could a bad cat effect the boost this much? Stockk boost is supposivly around 6.7-6.8ish

Green7mgte · 07-24-2011, 03:09 PM

well yes. the material in the catalytic converter may have melted over in places causing a severe restriction to exhaust flow and preventing boost from developing.

I would check for any vac leaks first, its ez enough. When your boosting do you see you needle dropping even with pressure on the throttle? thats one ez way to check for a major vac leak.

Awyman18 · 07-24-2011, 03:21 PM

No the needle never drops when on the throttle. So I don't think its a vac leak

mirage83 · 07-24-2011, 06:38 PM

A bad cat can definately cause problems. If it has to be replaced I'd recommend a hi-flow cat. Magnaflow has a good one that I'm running.

Awyman18 · 07-24-2011, 06:54 PM

Yea I plan on just buying a test pipe because I'm getting a new exhaust here soon. 3" pipe, the whole shabang. And I live in ohio and the emmission rules are lax

Imso-jdm · 07-24-2011, 08:47 PM

I took off my Cat from my supra mk3 7m-ge. i really felt the difference when i took it off compare when i actually had it

mirage83 · 07-25-2011, 01:13 PM

Lax laws or not, doing the right thing would be replacing the cat, not just removing it. A good quality cat would still allow for good exhaust flow.

El Supracabras · 07-25-2011, 05:28 PM

Using a test pipe is a good idea. They were designed to prevent expensive catalyst damage during tuning and racing and are not intended to replace the cat permanently. They are technically only legal off road regardless of state emission testing. Once the car has been tuned well, you can install a good hi-flowing catalyst. You should notice little to no decrease in power and the cat should last awhile.

Green7mgte · 07-25-2011, 07:46 PM

hmm well I agree with all the above statements. I would recomend running a highflow cat If you decide to put a new one back on. Altho that is entirely up to you. I'm not going to be as presumptuous and tell you whats right and whats wrong. A high flow cat from magflow will give you the same gains as running one w/o. If money is tight and you choose to run the test pipe till you save up, you still have an option of just going straight 3'' all the way back. Either choice is yours. Hell, I ran mine with just the downpipe for about 3 days while my exhaust was being fabricated. Altho I wouldn't recommend it I'm not going to tell you it's wrong. The thing with just deleting the cat all togather is the fabrication will probably run you about the same as a high flow (maybe.) and yes running the test pipe as a permanent solution isn't really worse off then running cat delete. if you want to take the risk, but again these are just options of what is available to you.

Awyman18 · 07-26-2011, 04:29 AM

well...thanks for the advice, and...we shall see on the cat lol

07-24-2011, 01:58 PM	#1
Awyman18 3" Exhaust Join Date: Apr 2011 Location: columbus Posts: 151	cat converter causing lower boost? So...I was driving my 1990 toyota supra turbo, and my friend who was driving behind me said that he could smell rotten eggs. So I'm guessing the cat is bad. Also, I'm only boosting around...5lbs..could a bad cat effect the boost this much? Stockk boost is supposivly around 6.7-6.8ish

07-24-2011, 03:09 PM	#2
Green7mgte Supra Forum Moderator Join Date: Nov 2009 Location: Green-Ohio Posts: 1,297	well yes. the material in the catalytic converter may have melted over in places causing a severe restriction to exhaust flow and preventing boost from developing. I would check for any vac leaks first, its ez enough. When your boosting do you see you needle dropping even with pressure on the throttle? thats one ez way to check for a major vac leak. __________________ 92 Ma71 7mGTE Auto. SafcII Supra FAQ Supra MKIII FAQ Classified Section guidelines :

07-25-2011, 07:46 PM	#9
Green7mgte Supra Forum Moderator Join Date: Nov 2009 Location: Green-Ohio Posts: 1,297	hmm well I agree with all the above statements. I would recomend running a highflow cat If you decide to put a new one back on. Altho that is entirely up to you. I'm not going to be as presumptuous and tell you whats right and whats wrong. A high flow cat from magflow will give you the same gains as running one w/o. If money is tight and you choose to run the test pipe till you save up, you still have an option of just going straight 3'' all the way back. Either choice is yours. Hell, I ran mine with just the downpipe for about 3 days while my exhaust was being fabricated. Altho I wouldn't recommend it I'm not going to tell you it's wrong. The thing with just deleting the cat all togather is the fabrication will probably run you about the same as a high flow (maybe.) and yes running the test pipe as a permanent solution isn't really worse off then running cat delete. if you want to take the risk, but again these are just options of what is available to you. __________________ 92 Ma71 7mGTE Auto. SafcII Supra FAQ Supra MKIII FAQ Classified Section guidelines :

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07-24-2011, 03:21 PM	#3
Awyman18 3" Exhaust Join Date: Apr 2011 Location: columbus Posts: 151	No the needle never drops when on the throttle. So I don't think its a vac leak

07-24-2011, 06:38 PM	#4
mirage83 12psi boost Join Date: Feb 2007 Location: Georgia Posts: 359	A bad cat can definately cause problems. If it has to be replaced I'd recommend a hi-flow cat. Magnaflow has a good one that I'm running.

07-24-2011, 06:54 PM	#5
Awyman18 3" Exhaust Join Date: Apr 2011 Location: columbus Posts: 151	Yea I plan on just buying a test pipe because I'm getting a new exhaust here soon. 3" pipe, the whole shabang. And I live in ohio and the emmission rules are lax

07-24-2011, 08:47 PM	#6
Imso-jdm Stock Join Date: Jul 2011 Location: Brampton, ON, Canada Posts: 2	I took off my Cat from my supra mk3 7m-ge. i really felt the difference when i took it off compare when i actually had it

07-25-2011, 01:13 PM	#7
mirage83 12psi boost Join Date: Feb 2007 Location: Georgia Posts: 359	Lax laws or not, doing the right thing would be replacing the cat, not just removing it. A good quality cat would still allow for good exhaust flow.

07-25-2011, 05:28 PM	#8
El Supracabras 3" Exhaust Join Date: Feb 2010 Location: Chicago Posts: 240	Using a test pipe is a good idea. They were designed to prevent expensive catalyst damage during tuning and racing and are not intended to replace the cat permanently. They are technically only legal off road regardless of state emission testing. Once the car has been tuned well, you can install a good hi-flowing catalyst. You should notice little to no decrease in power and the cat should last awhile.

07-26-2011, 04:29 AM	#10
Awyman18 3" Exhaust Join Date: Apr 2011 Location: columbus Posts: 151	well...thanks for the advice, and...we shall see on the cat lol