So currently I am running the AMS TBE with test pipe. I'm the kind of motorhead that would rather hear the engine and exhaust notes than listen to the music half the time. Although I love the sound, the long highway drone gets old after a while, not to mention the cloud of exhaust that plumes when i get WOT. Performance wise will a HFC be significantly different than a test pipe? I dont think it will but I am curious to know. Asking because I think Im going to switch over to reduce some of the noise and to make it actually street legal. Hear that the cops out here are actually checking 'modified' cars for catalytic converters.

 

kinda the same check out...could be of some use...

https://www.evolutionm.net/forums/sh...d.php?t=312422

 

of course there will be a performance difference between TP vs HFC. You will be looking at 10-20 whp.

 

You could always do the Buschur 2 muffler trick versus just a straight TP...

 

Wow, after all of the reading I have done on this particular topic I havn't come accross anything that says you will lose 10-20 WHP. The most I have heard about is 1-5 WHP between a TP and a full Cat. 1-3 between a TP and a HFC.
I read an article comparing Test Pipes to HFC and Full Cats and the differences were minimal.

 

Not on our cars. It's pretty significant, search the topic and read around a bit; you'll see.

 

yeah, not sure where the 10-20whp number came from. made me sick to my stomach thinking it was that high. One of the guys on here with a 9 second Evo and 11 sec daily driver evo IX, told me just to use a HFC because the horsepower differences were minimal at the lower horsepower range.

 

There are TONS of these threads. I guess it's the new year so we need a new one!

At stock HP and boost, yes I can see the gains are minimal. Anything over 300whp the gains start to increase significantly. The more boost you run the more flow you need!!!

Yes, it IS more than 1-5 HP. I've had both a HFC and test pipe. Went with the pipe!

 

Testpipe is less restrictive ,period. When a cat heats up, then will be really restrictive.
Just remember, on the dyno the cat dont have really enough time to heat up all away. In the race situation will be much more hotter then on the dyno. So you will have more restrictive cat on the race day then on the dyno day. Now the test pipe is just a pipe. So you get what you have. All day long.

 

Why would a hotter cat be more restrictive?

 

because its actually start working and expands inside. Most cat not even working untill they heats up. So when is cold, little more restrictive then the testpipe
/ highflow cat /.

 

I have a Resonated Test pipe on my AMS Exhaust. So it looks a bit like a HFC to a laymen and brings down the noise a touch. But I believe it is by no means quiet on the highway. Especially if you maintain over 80mph. However I never ran a straight test pipe either... So unless we start talking numbers, SAE dBs etc, then this is not a helpful comment on "loudness".

 

You should run our resonated Test pipe. Its $219.00 And has all the subtle tone of the cat but all the HP gains of a test pipe

Eric

 

i passed;
with the 3 inch, TBE Blitz nur-spec Not the quiet exhaust i can tell you that much, and resonated test pipe/e-bay/
The lime rock DBs test. The limit was 88 db ,and 1000 rpm below the redline./you have to hold it there/
i do not remember the exact distance where they measured it , but wasn't that far from my exhaust.
So in N.J. the legal limit is 93 db. That is mean i will pass the noise inspection with 3 inch TBE with test pipe.

 

HFC is a good choice if you are concerned about the sound level and smell. Testing back and forth using my HFC and test pipe revealed that big differnce between them are more sound and smell than power.
You lose about 5~10 Whp and bit of spool up time compared to Test Pipe.