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Discussion Starter · #1 ·
For a 1987 Grand National....

1. ATR high flow cat converters....anyone know how good/bad they are?

2. Suppose said '87 GN had a 3 inch straight shot exhaust with a Dynomax Ultraflow muffler....if a high flow cat was installed, how much would turbo spool up, hp, etc. be affected?
 

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I would only install a converter if I had to, otherwise a test pipe/aftermarket exhaust is the way to go. The converter restricts the exhaust flow which in turn slows down the boost build up, and may effect total peak boost output which in turn will effect peak HP. I remember when these cars were new and we would remove the converter and replace with a test pipe and it really woke up the car.....and a big noticeable difference. Any converter will effect the power in negative way(very noticeable). Another thing to look out for is, if your going to install a converter onto a car that doesn't have one on it, you have to be aware of the chip/tune the car is currently running, a lot of the tunes/chips are meant to run without a converter so you may cause issues by installing a converter. I don't have any experience with the ATR but, it's probably better then a stock unit.....if your forced to run a converter.
 

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Discussion Starter · #3 ·
I don't "have" to run a cat....but the problem is, anytime I start or drive the car, my clothes end up smelling like exhaust fumes. Also the exhaust fumes get into the house, stink everything up and set off all of my CO2 alarms. To me this is a draw back, especially since the car gets driven rather daily. Nothing like coming to the office smelling like raw unburnt gasoline fumes right?

I know in the old days, catalytic converters were restrictive, but I would think in todays day and age, they would have finally found a way to make catalytic converters less restrictive while still cleaning the air.

If it helps any, my engine only makes maybe 370 hp :eek: yet has a full 3" exhaust off the turbo on out the end of the tail pipe, while using the highest flowing muffler on the market. I'm kinda thinking maybe the size of the pipes might be a bit of an overkill for the car, so perhaps a 3" ceramic ATR cat wouldn't hinder performance/spool up too much...?
 

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register it as a historic and no more inspection ever and no cat checks either.
 

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A couple comments:
1. If your clothes stink from just driving the car, setting off the detectors, etc, there's something wrong...Tune, etc.
2. ATR has been out of business for many yrs. That cat may not be the better design, such as metal substrate brick.
3. Tests of the hi-flo Random Tech cats show about a 3-5HP loss.
 

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I have the same "stinky exhaust" issue. It never bothered me until my dad was in town; he drove the Buick and I was in the passenger seat. It smelled pretty strong, like unburnt exhaust.

The numbers on the ScanMaster all look great at idle and WOT. I wonder if I have a post-turbo exhaust leak and it's getting into the car near the passenger side (maybe downpipe-to-testpipe or turbo-to-downpipe).

My wife doesn't like riding in my Buick... now I realize why she complained so much (I thought she was just jealous of my other girlfriend). My dad said it smells more than his 66 GTO.

My car is in semi-storage for the winter. In the spring I'll probably try to diagnose it myself (and take it to a professional if I can't figure it out).
 

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Metal Matrix Hi FLo Stainless Steel Catalytic Convertors

A couple comments:
1. If your clothes stink from just driving the car, setting off the detectors, etc, there's something wrong...Tune, etc.
2. ATR has been out of business for many yrs. That cat may not be the better design, such as metal substrate brick.
3. Tests of the hi-flo Random Tech cats show about a 3-5HP loss.
X2

Go with one of the newer style Hi FLo Metal Matrix Catalytic Convertors. Minimal cfm loss and they work way better than the old school ceramic core convertors of yesteryear! :yup:
 

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Like Chuck says...your car is out of tune. Order a chip from Eric...and that'll sort it out. Put a cat on the car with it running way rich...and the exhaust will smell like rotten eggs. A cat affects driveability...period.
 
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