Hey,
I am installing my Bonez hi flow cat monday and I was wondering what kind of hp gains I am gonna get over the stock setup.
How much of a hp loss would it be over a straight pipe?

 

It depends on how clogged your cats were to begin with. Is this the downpipe + main cat replacement? The difference will be noticeable in speed and sound, but don't expect 20 rwhp

 

Your drastic HP gains from exhaust will be doing a FULL exhaust system. That includes the FULL package of headers (no stock exhaust collector or pre-cat), main performance cat or pre-silencer, aftermarket cataback exhaust & mufflers.

The Racing Beat dual or single full-exhaust is dyno proven.

Note while I only gained ~5HP from replacing the 3 stock cats with a single high-flow cat, I picked up a more low end torque and noticed a HUGE improvement in streetability (wider power band / RPMS) & the engine's eagerness to rev.

 

wow i wish i didnt live somewhere where i cant do that.

 

you should be able to get away with a high-flow cat. Most times, they work much better at cleaning up your emisions then a stock setup, and the couple I've seen had a new downpipe eliminating the pre-cats. Personally, I'm going to pull my pre-cats and have them replaced with a straight downpipe when I take my FC in for a new y-pipe.

Here's the Catco units on Summit, which I've heard are pretty sweet, and have a great price IMO.

I don't think they have a turbo one, the set they sell there have 2 1/4 inlet and outlets: http://store.summitracing.com/defaul...=catco&x=0&y=0

 

The difference between the OEM 3-cat setup and either installing the Bonez or gutting the first two OEM cats is amazing, definite seat-of the pants improvement. The difference between gutting the first two OEM cats or installing the Bonez is negligible...The difference between the Bonez hi-flow with the cat and without is also negligible, all other things being equal. I've tried all 4 "flavors"

 

So cutting the pre-cats is recommend as well, eh? I'll have to attempt a pull when I get the chance and take the lead pipe to the inards. Do you leave any of the honeycomb in to attempt to keep turbulence down, or should I just keep hacking at it until all the junk comes out?

 

Just to point out...you won't get crap from a "high flow" cat vs. an OEM cat...

...hold up....for some reason the fact that the fc has a stupid number of catalitytic convertors escaped me....

 

It's not a good idea to keep anything in there, as it will tend to break up and clog anything downstream (been there too, lol). Completely gut the first two, take a good look at the main cat while you got her out, then throw everything back together. Drive around like that for awhile if you wish, because the $350 Bonez (that was back when I bought it) will give you almost nothing in gains compared to the gutted-first-two setup...

 

Gutting is definitly the cheapest way to increase flow and will net a bit more HP. I wanted a better solution that was cheap, so for a little bit of money I got a used downpipe (partial headers). Turbulance is a non-issue and it's much simpler.

Here's my setup, a magnaflow 93516 cat with the OEM cat flanges welded on for easy removal.

More details here:
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/pics-hp-gained-magnaflow-vs-bonex-cats-321221/

 

well I got it in and its quieter that my old ones.
Also it was too long and we had to cut it up.
How long is the stock one? If I went straight thru from one flange to another it's 40 in.

Must be cuz I have an custom catback.
HP wise I haven't tried it yet.

 

I installed the Bonez Intake, Bonez less restrictive Cats and Racing Beat Cat back system. Can't say there was a dramatic Horsepower improvement but car feels stronger and smoother and sounds wonderful! I love it. But Remember-I live in California so I am limited to what I can legally do and quickly repair every two years when we have to Re-test for emissions. It's a good compromise.