328 test pipe to get desired sound / performance

Hope you're wearing nomex!

 

From Ferrari 328 primer, version 0.1 (a work in progress)

I have run a Stebro 'euro resonator' in mine, deepens the sound without being too obnoxious

 

Hi,
I have a 89 328 GTS, and recently replaced the cat with a Tubi test pipe. The exhaust is a bit noiser, there is perhaps a touch more power, I picked up a resonance when the exhaust when it is cold which may or may not be related. The BIG difference, and reason why I am very satisfied with the modification, is that the heat in the engine compartment is significantly reduced... I didn't get the chance to run the car hard before and after, so I can't really say what, if any, performance advantage there is. I would hazard a guess of perhaps 10-15hp.
Cheers, Lawrence.

 

Having taken the 328 exhaust and cat off before (in order to install a Tubi, but reinstalled the cat) I see little restriction with the stock cat. I would doubt very much that one could gain 10-15 hp by removal of the cat. I would guess 5 hp max, maybe nothing.

I have removed the dual cats on a 78 308GTS, and noticed no performance increase, but some additional volume, which was pleasant.

 

The Mondial t / 348 engine w/o cat is factory rated at 300 hp. The swiss version with its heavier cat is rated at 285 hp, the other cat versions at 295 hp.

I guess this is a pretty good indication that the performance gain is small.

 

I run my 89 328 GTS with Tubi test pipe and exhaust. I wouldn't dream of going back to stock.

Marginally more power, substantially more sound. Not just "louder" but "more sound."

 

One other thing that I am looking for at some point, pehaps with a hyperflow cat or something other. I'm pretty content with the 328's power (it is what it is!), and the sound is pretty damn good. However, what I don't like is the typical delay between blipping the gas and the susequent rise in RPMs.

When I put the catless ANSA on the 308 (for the track only), it was MUCH free-er revving.

This is important when blipping the throttle on a downshift; now, I have to have a second or so of lead time to get the RPMs where they need to be...

So, a stebro resonator or hyperflow cat (or no cat) might allow for a more freely revving system, by reducing the backpressure in the exhaust.

I don't know how much of this is due to the cat, and how much do the actual exhaust itself...

 

As davehanda indicates, you'll find the stock cat is pretty free flowing, so, likely modest performance gain from replacing with a straight/test pipe, particularly if your cat is not deteriorated in any way. However, you'll find there are two other significant benefits with a straight/test pipe: a) lower engine temps - perhaps a full 10 degrees on hot days (oil and water), and b) lesser chance of engine fires due to unburnt fuel accumulating and lighting up in the cat. The straight pipe and stebro muffler on my car has a wonderful sound but you won't be sneaking up on anyone unannounced. There is quite a bit of resonance which my wife finds annoying (but what does she know...). Incidentally, for those who scream environmental degredation, my 3.2 passes emissions in WA state with flying colors with this set up.