Hello:

I plan on installing a complete exhaust on my 85 when one is developed and available, but in the interim I have been wondering about my cats which were gutted several years ago.

I read in a previous post that there is a loss of gas velocity when it enters the open cat, and that the velocity is never regained. I am wondering if I would be better off to section out the cats and just replace them with a straight pipe to reduce the loss in gas velocity?

Any thoughts? And if someone out there has headers, x pipe and dual 2.5 inch or a merge collector into a 3.5 inch exhaust ready to go, contact me....I'm ready to buy.

Regards,

Ken

 

I believe if there's some sort of x-pipe or h-pipe integrated with the bypass pipe it will provide some form of smoothening of the flow and pressure to maintain velocity. I haven't heard of any losses in a cat-bypass as long as the 2 style pipes above (either or) are installed and the exhaust piping isn't too open. Maintain anywhere from 2.5" to 3" per each bank of the motor since your car is a 32 valve engine

 

Hi Andy:

My application is just gutted cats, not a true purpose built cat bypass. I am concerned that when the gas reaches the cat chamber which is now empty that it will slow down and not be as effective as a straight pipe.

Behind where the cats are now I am running a 2 into one merge collector with a single 3 inch pipe.

Thanks,

Ken

 

I'm sorry I'm not familiar with gutted cats. I would assume though that due to the diameter of the catalytic convertors on the car, that the exhaust would be losing density if entering a larger chamber such as that one.

 

Andy

Thats what I was thinking.....

Thanks,

Ken

 

Well so much for theory !

I have removed the Cats (offroard) on my as before described exhaust.....merge collector 2 into a single 3 inch.

Only to find that the car lost 3 MPH in the quarter mile times as recorded on my G- tech.
Same road etc....different day and I know that temperatures etc. could have played a part but that is a sizeable loss.

Can anyone who is using a single pipe tell me how far back from the manifold they have made their "union". I wonder if the merge collector is out of the sweet spot? For that matter an x pipe measurement from the manifold would probably serve the same purpose.

I hope some one hurrys up and builds a dual exhaust for these darn 85/86 cars "BOOB" bit of old bugger. The car ....uhhh well both of us.

Ken

 

i'm kind of lost on what to do with my exhaust also. currently i had the aftermarket cat removed and had straight pipes put in. the car now has 2 pipes to the mid pipe, then two to the muffler and something is rattling terrribly. i'm not sure what to do, i was thinking of buying a stock muffler with two inlets and removing the midpipe and having the local shop make an x pipe/h pipe somewhere up from where the cat used to be. if the exhaust system you're looking for isn't already on the market, i really woulnd't expect it to be curretly in development and ever hit the shelves. 84 euro