extra HP from cat and exhaust?

IME (and HO), doing free flowing cats and a Tubi alone will not produce a huge gain in HP. It will help some, but if you don't open up the breathing on the intake side, merely opening the exhaust will give a little boost, but not much. Maybe 10 hp? Now, if you port the heads, play with the cams, open up the intake, along with tweaking the exhaust, you could pick up a nice amount of HP. But you can only get out of an engine what you put in. Unless you go with forced induction or play with the heads and cams, the gain won't be enough from exhaust alone to really feel much difference in the driver's seat.

YMMV.

 

I don't have any specific experience with 328s, but what FasterIsBetter said above is exactly my experience with other cars.

 

I have a 1981 308 GTSI with the same CATS and Exhaust installed. Mine is going in this Tuesday 5/15/07 to the Dyno. THe shop is going to reset my fuel mixtures and airflow on the Dyno for me.

The mechanic said I will receive all sorts of data from the Dyno including a HP readout. I will post it when I get it.

Jeff

 

Call me stupid but I'm wondering why you guys just don't remove the cats.
Am I missing something?

 

Well.

Here in the Peoples Republic of California, Every two years are cars get checked to see if we are contributing to Global Warming. Since we are not eligible for carbon credits for our Ferrari's, we must then keep our smog systems working. The fine is most likely being shot in the head.

Hyper-Flow CATS have the same effect as a test pipe with only a 5% loss in engine power and we get to tell the SMOG Nazi's that our cars confom to the higher than Federal standards for emissions because California MUST be a leader in everything.

Because I am basicly lazy, I do not want to have to install CATS everytime I need to prove to the emperor my car conforms.

Hope this explains it.

Jeff

 

<laughing like crazy>

ah yes, you nutty Californians

 

I had test pipes put on my '80 308 this week and it sounds so much better. Not alot louder but it now has a deeper rumble.

Without expecting it i seem to have a little more power. My cats were clogged so maybe getting rid of them got rid of some back pressure.

I wouldn't change a thing now.

 

Yep guys,

On my Rachel, I did Hyper-flows & X-Ost. Not only do I pass Smog BS with flying colors, but I hear the most beautiful music from behind my head. - - Oh, and I picked up some added ponies (that I can feel) as well

Cheers all,
Hank

 

My experience with X-ost and hyperflow is great sound, very slight increase is throttle response. Increase HP is not reason to change.

I'm awaiting Tommy's(Cosgrove) obligatory response on the smell associated with test pipes........

You'd be crazy to change to test pipes in CA, limited or no benefit on HP, the smell and the problems passing smog/getting stopped and fined for illegal setup.

Jeff

 

Loud pipes save lives,

LOL
Guess, this isn't allowed in California.

Here, in Europe, we stille have the benefit of exeptions for older cars.
In this case, I've done some research (frankly I demolished it) in Ansa-technic. The thing was actually in perfect shape. As a kid I always wanted to know how a clock looked from the inside. My parents, still in good health, never knew why so many clocks in our house had such a short life. Back to the so-called Ansa sportexhaust. This soundbox does not only weigh the equivalent of a horse, it also has so much restrictions in flow that it's a wonder that they help to produce any horse at all.
So, with some dare, I took the liberty to fabricate some silencers myself.
I have done a lot of weightreducing mod's on this car. Now I have an alternative that weights 4,5 kg. (ever powerlifted an Ansa?).
After placing them, I gained some acceptable increase in db's but hey, wat a noise! I use the K&N replacement and needed more fuel. It's a matter of finetuning the carbs and next step is to the dyno.
I went for a 600 km drive to the Nurburgringregion and back. No regrets. The only silencer I would put back is the original single tailpipe. I leave it on the shelf untill I sell the car. (not likely that I will)
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The smell on my car is slight. My mechanic says if the smell is too strong something in the ignition is off and needs adjustment/replacement.
It really does feel more powerful and the sound is fantastic IMO.