Would I see a big improvement in exhaust flow if I bought the Bonez DP and mid pipe and kept the stock cat on? My car only has 32xxxmiles on it and need to keep the cat for smog. I'd like to save the extra cash and not buy the high flow cat.

Anyone have any thoughts?

 

the cat is the main power restriction, so no not really.

 

Of course. Well im in toronto and with the dollar,tax,fees, shipping etc it would be about $900 CDN for the Bonez turboflo system with midpipe and gaskets. To me thats too much. I should just get a custom setup with a magnaflow cat then.

 

or a presilencer the same size as the cat.

 

I need to keep the cat on the car. I was caught before with no cat on my 944 turbo. Was given a ticket and now im in their system for it. Car was old enough to not need a smog test but still needed a cat. So needless to say i do not want this to happen again.

 

then go custom with a high flow cat

 

The Bonez system eliminates the precat and with the Bonez high flow main cat I saw no improvement
in performance. Actually, with the Bonez DP along with the factory main cat and factory cat back
(purchased the car new so exhaust is original), there was no difference when the Bonez cat was installed,
and both pass the NJ emissions test.
Still run 12lbs with both, just that with the Bonez cat there is more of an exhaust note, which I like, but
the wife hates.

 

Really. I didn't expect that. The catback on my car was replaced back in 1998 with stockish parts. So i'm leaving that alone. I'm not really looking for a big power gain here. I'm just looking for quicker throttle response and a decrease in lag. Also is the stock dp and mid pipe 2.25"? I'd like to go all 2.5".

 

What year are you working on?

 

I have an 88 10AE. It was not driven much. Thats why the cat back had to be replaced in 98. Probably filled up with condensation and rotted in a few spots. The replacement catback is still in great shape. So i may as well get a 1 pc custom 2.5" dp made to a magnaflow Hi flow cat. I'll keep the air pipe as well.

 

I've known people who would gut the factory cat, slip a piece of pipe in and weld it. However, I imagine if someone were somehow caught having something like that there would be lots of money involved in getting a new set of problems to go away.

 

They catch you on that one by using a heat gun. If its hollowed out with a pipe through it the temps on the pipe going in are almost the same as the pipe coming out of the cat. If its a stock cat the pipe going in is much hotter.

 

pretty technical to get a couple cars off the road emissionswise..

 

Ya tell me about it. But its quick and easy. Ontario, Canada sucks for emissions testing. Not as bad as Cali but still crap if you live in an emission zone.

 

sounds worse actually. i have never heard of a cop running a heat gun on your hogged out cat.

 

Cop won't do it, but the emissions testing facility might.

As for upgrading the exhaust and keeping the factory cat, I wouldn't bother, the old cats are the most restrictive part of the exhaust. Get yourself a generic high performance 3" cat and get an exhaust shop to weld on short pipes and flanges - that's what I did. Picked up a brand new 3" Flowmaster high perf cat that was leftover from a guy's Camaro project off Kijiji for $60 (he forgot to drop it at the shop with the car, so they used their own), and I think it cost me $120 at a shop to get flanges and short connector pipes added so it dropped right in where the main cat (or in my case, RB resonator) would go. No power difference that I could tell, and actually sounded a little mellower at idle than the Racing Beat resonator/midpipe.

 

Its the ministry of transportation that will check it, not the cops.

Oh cool. Ya sounds like a good idea. I'll get a 2.5 DP to a highflow cat custom made and installed.

 

if you need a cat, but don't actually need to pass an emissions test, which is a situation i would really like, try one of these Products - Random Technology

the metal substrate are higher enough flowing, and more durable than the ceramic.

unfortunately i'm in California, so we can't run these, for some reason this style of cat is against the law here.

 

because they are less efficient.

 

I installed a random technology cat on my 944 turbo. It was a 1987 and in Ontario if a vehicle is 1987 and under it no longer needs an emission test. But my rx7 is a 1988 so i will need a working cat or i would run another random technology cat. They are great. Get rid of the smell and barely hinder performance.