jsotelo

I have not seen much posted on this subject even when I search..

RB says that unless you are using a carb to NOT use a header.. just use a the cat replacement as it's less expensive and offers "similar" power gains..

WTF.. I have been told that the stock manifold of the FC sucks *** and is very prohibitive but I guess I would have to believe RB...

Anyway I don't know anyone that doesn't run a header.. Does anyone know how much more power a header makes than the cat replacement/pre silencer?

Seems that the Header/presilencer combo costs $200.00 more.. ouch

Suparslinc

It boils down to money. A cat replacement pipe is a good alternative for the price; thats what my '84 GSL has and it's a nice piece of metal.

ilike2eatricers

bump

CrispyRX7

iTrader: (139)

Just did RB header/presilencer combo. Yeah about $200 more but no regrets. Much to my surprise and pleasure though the RB header came with a block off plate/kit for the ACV valve too. I have an '86 BTW. Presilencer has enough backpressure to run the 5/6th ports without the airpump and ACV Yippee!
OBTW the headers make the car sound absolutely killer not to mention the weight savings over the stock setup. Although the RB header and presilencer aren't light they are still 12 lbs lighter then the stock manifold, precats, and main cat.
FWIW
Crispy

jsotelo

Well they say I can get 18 HP by doing nothing more than running a downpipe and presilencer.. that's only 290.00 so that sounds like the route I will probably take.. just keep the stock exhaust for now.. they say that's about 7 hp to replace that but it's about 600.00 for the setup to do it..

Okay this is what it says in the Ad for the combo..
"The down pipe is equipped with a mounting flange for the oxygen sensor, and an exhaust back-pressure tube for correct operation of the 6-port actuators. Installation of this requires the removal of the air control and check valve and the air pump."

Now I don't HAVE to remove the ACV, Check Valve and air pump right? I'd like to keep it so that when smog time rolls around in a year I can just pop my cats right back in..

Also it says that the DP has a mounting flange for the O2 sensor... doesnt' the O2 sensor bolt into the maniforld?!?

CrispyRX7

iTrader: (139)

I don't see why you'd have to remove the ACV and airpump in place even when using the RB presilencer. When I did the header it certainly looked like it wouldn't have been a problem to leave that stuff in place. BTW if you just want to replace the cats (both pre and main) with a straight pipe loom at what Rotary Performance offers. They sell a one "piece" pipe that replaces everything from the OE manifold to stock "Y" pipe for about $170.
As for the O2 sensor bung, you got me on that one?
Regards,
Crispy

rx7will

iTrader: (6)

I would go with the simplicity of the cat replacement pipes, since you are concerned about smog.

1BADRX7

I've tried both DP-presilencer and Header-presilencer and the header is king. The difference in power is noticeable, and the louder header sound is really nice.

A'PEXi 7

ive had both. the headers do have more power......maybe like another 5hp......but i hated the sound at the top end. So i took the header off and put on the stock manifold and the replacement pipe. Not a huge difference in power but i loved the sound......just deep all the way to redline.Then it gets loud..............

jt240

*bump*... I'm coming from the world of Hondas, where a header, high flow cat, and cat back were the basic essentials in replacing the stock exhaust system. Seeing as the RX7 exhaust system is much more complex, I would too like to know more about the header vs presilencer/cat.
Also, how is the stock catback in terms of its restriction? I was thinking of just getting a BONEZ highflow presilencer+cat combo, and keeping stock header and stock catback.. normally replacing the midsection on a car and keeping the stock rear section is pointless b/c the rear is a bottleneck, but is this true for the FC as well? My other alternative would be full RACING BEAT header all the way to stock cat back.. again, is this pointless when used w/ stock catback? I'm shooting for optimum power gains, but w/o the super loud noise. HELP A NOOB PLEASE! TIA