Y Pipe Vs Catalyst a Comparison

[Fixer]

After filing and honing out my 16V 1983 928 stock exhaust manifolds (logs) i decided to take another look at both the Y pipe
i have been using and my old Exhaust Catalyst.

Not seeing much dimensional info on the Y Pipe, I thought I'd do that here.

I do like the sound and presume i have a bit more power because the older Cats do not flow like the later units
from my experience.

I bought this Y pipe a year ago through Auto Atlanta, It took well over 2 weeks to get to my door.

It is made of mild steel and was painted black for 'presentation' only. It cost about $200.

Firstly it does weigh a bit less than the Cat;

Weight Y= 8.8lbs Catalyst: 21.4lbs.

The Tubing Diameter of the Y is also larger all around;

Y Inlet O.Dia: 2" Catalyst Inlet Outside Diameter is 1.9" the wall thickness is the same, and this difference translates into a larger ID for the Y Pipe as well.

Both collect into a larger pipe and the Y Pipe again has a larger Interior Diameter;

Y Outlet Interior diameter: 2.4" the Cat I.D.: 2.275"

I found the alignment of the Y's Flanges to the Cast Iron Manifolds to be OK but not great. Heat may be required to bend them to fit better.

Also at the outlet of the Y pipe, it is not designed to use the stock Donut exhaust gasket, you have to source a gasket from your neigborhood Auto Supply. This means that no movement is allowed for as designed.

I do like the burble and it sure did not make the car run worse, but HP gains cannot be verified by me.

If anyone has dyno'd their 928 with a Y Pipe please include that information

[MPDano]

I wish I could do that in Smog Nazi California

[AirtekHVAC]

I think the y pipe is crap, no good, junk....put the cat back on, and....well, heck, just send me the y pipe, and I'll get rid of it for you.....

[Fixer]

Originally Posted by MPDano

I wish I could do that in Smog Nazi California

how old does a car have to be? probably if it had one originally rule.

Originally Posted by AirtekHVAC

I think the y pipe is crap, no good, junk....put the cat back on, and....well, heck, just send me the y pipe, and I'll get rid of it for you.....

LOL, if/when i am done with it it's yours. Looking for another setup eventually.

[Danglerb]

Ca froze inspection exemption at 1975 and earlier, but I run a Y with a high flow cat with so far no issues, but I slipped under deadline for using generic "type and weight" approved cats. New law as of a couple years ago requires model specific replacements, and all are the old klunky style.

Done right a Y or X has a solid bump in torque, that one doesn't look too right.

Burns Stainless merge pipe as used in a Y.

[Fixer]

Done right a Y or X has a solid bump in torque, that one doesn't look too right.

Burns Stainless merge pipe as used in a Y.

yes not much went into it's design and fab from the looks of it.

will look into Burns

[Danglerb]

Two parts to "right" the merge and where it goes, best results I know of on a 928 are from Greg Brown's exhaust system with crazy as it sounds the merge at the rear near the battery box. It makes a lot of torque.