has anybody on here done 2.5 or 2.25 straight pipe header back? ive heard this gives some good gains but takes away some low end tq. im considering it cus im gonna s/c for sure but i just wanna know how it has faired with people out there..

i used to have it on my old z24. straight 2.5" mandrel bent with a magna flow muffler. good gains i must say but really just throw a high flow cat on it. cause i did one day for sh*ts and giggles and the gain wasnt very noticeable after that.

i to had it done on my older z24. it had an rksport 4-1 header, 2.5" mandrell bent catback, HFC and 2.25" catback system...
i had it 2 ways, straight pipe, and magnaflow muffler.

ill just put it this way, it ran its best time with the muffler ON. and the butt dyno def. noticed an increase in torque after installing the muffler.

IMO straight piping it was useless and gained nothing, now... on something a lot more hp-say turbo or nitrous or something, then i could see it helping, but not on an average N/A car.

o i think i confused u guys, i was referring to deleting the cat and putting straight pipe there? is it worth it to do 2.5 from the header back with no cat is wut i meant...

im running 2.25" with a gutted cat which is the same thing and i lost low end but gained some top end.

do u think its worth it or not?

i think it was, any gain on top end is worth it man.

does it have that bad smell? ur makin me lean toward it again...

its worth it till you go to get your car inspected or you get a ticket, the fines are outrageous!!!! but if its JUST a track car then ya its worth it. hell for that matter just runn the pipe off the header and straight out the side behind the front wheels


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i did mine mainly due to it failing and not having money to properly repair it. though here within a couple of weeks i plan on having it all redone from the manifold back to tip including a new hi flow cat, now my car did have a smell for the first about week but after that it cleared up and i actually to have yet have a cel for it. but i plan again on being emmisions legal. but yes you notice a slight difference but the raspiness and chance of legal issues is not worth it to me. good luck man.

we don't have emissions here, so i know alota people that have it on other cars, i was mainly concerned about the benefit on a cav..

whether or not you have to pass emissions in your area, its a FEDERAL OFFENSE to remove a cat from a car that came equipped with one from the factory. let that sink in. if the cop's an ass, you become an instant felon for just not having a cat on your car.



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When I had the turbo, full 2.5" madrel exhaust, on the car I had my cat flanged so I could easily swap in the test pipe. Honestly the butt dyno said no gains so I just put the magnaflow cat back in.

i'd recommend doing it and going with 2.25" exhaust, thats what i have and i noticed a gain up top. you will not fail emissions if you have them because it throws no light what so ever if you just cut your current cat cause the 02 sensor is still hooked up, if you take out the cat and put a peice of pipe in there you would have a engine light thrown because the rear 02 sesor wouldnt be hooked up. you can however put in a 02 simulator so the ecu thinks the cat is hooked up and running fine.

In the case of the ECO where there isn't a sim available you can buy the spark plug anti foulers and use those. Sensor is still hooked up but the anti foulers bring the sensor out of the exhaust stream. I'm not sure how much the sims are but I spent about $5 on the anti foulers.